Science topic

Membranes - Science topic

Thin layers of tissue which cover parts of the body, separate adjacent cavities, or connect adjacent structures.
Questions related to Membranes
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I have used hydrophobic MMT, Cloisite 15A and General MMT in PVDF membrane with 18% of concentration. It was found that the hydrophobicity of membrane changed the same degree. Regarding to the fact that the hydrophobicity of MMT is more than those others, I was surprised. What are the factors that possibly affect the changes of hydrophilicity in this case?
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Any amount of hydrophilic and hydrophobic nature of nanoparticle can effect the structure the structure of polymer but the effect is visible for a good amount of both the properties.
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I have been using celo-phane membrane for diffusion studies but not getting drug release in a requsite manner..so can i think that  membrane is not upto the level..pls help
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The file attached contains a list of 13 Synthetic Membranes.[ Zoom150-200]
Table 1. contains their (ρ - membrane porosity, τ – membrane tortuosity). and
Table 2. contains total diffusion after 6 h and the coefficient of variation (CV) of flux for individual synthetic membranes.
The tables are reproduced from the following paper:
Pharmaceutics 2010, 2, 209–223; doi:10.3390/pharmaceutics2020209
A Comparative Study of Transmembrane Diffusion and Permeation of Ibuprofen across Synthetic Membranes Using Franz Diffusion Cells
Shiow-Fern Ng 1,*, Jennifer Rouse 2, Dominic Sanderson 3 and Gillian Eccleston 2
1 Faculty of Pharmacy, Universiti Kebangsaan Malaysia, Jalan Raja Muda Abdul Aziz, KualaLumpur, 50300, Malaysia
2 Strathclyde Institute of Pharmacy and Biomedical Sciences, University of Strathclyde, Taylor Street, Glasgow G4 0NR, UK
3 GlaxoSmithKline, Pharmaceutical Development, Harlow, CM19 5AW, UK
* Author to whom correspondence should be addressed; E-Mail: nsfern@gmail.com;
Tel.: +603-92897199; Fax: +603-26983271.
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Selection of membrane is very important for expression of proteins with good quality in WB. So I want to know the best membrane and its supplier so that good results can be obtained. 
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PVDF membrane from Millipore is very good. My lab colleagues have been using it for a long time and it is working very well.
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I have inquisition about the presence of ions in outer and inner side of the cell membrane? Please answer.
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Simply, because Na is toxic for the cells while K is not, despite both have nearly chemical and physical properties. In addition, K is the main ion participating in membrane potential. The latter is so important for ion absorption as well as other physiological processes occurring in the membrane. 
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In my experiments, some different electrospun membranes were fabricated from the PHB solution with the different solvents. And the results showed the solvents have the obvious effect on the elongation of these fibrous membranes. For investigating the mechanism,what characterizations should I do?
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I think you should refer to the dipole moment and dielectric constant of the solvent as greater value of dipole moment and dielectric constant will result in higher amount of accumulated charges on collector and then result in higher pulling force applied on the polymer jet. In this case the collected fibers are more elongated and maybe thinner.
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Platelet rich fibrin is being claimed to be a natural autologous barrier membrane for periodontal regeneration nowadays.
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Hi Saurav.
My answer would be NO.  This because bone needs months to repair or grow, but soft tissue does it a lot faster, just weeks.  PRF has another benefits but I don't see it being a cellular occlusive material since it resorbes no more than 2 weeks after, just like any other soft tissue would heal.
Grettings.
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Hello,
I'm working with clinical isolates of A.Fumigatus for my secretome analysis. Previously, I used Millipore ultrafiltration membrane in amicon ultrafiltration unit to concentrate the large volume of protein sample. Now, I'm in sort of membrane to pursue my work further. I would like to get suggestions for the alternate method to concentrate the large volume of protein sample.
Also,
1. Can I use the same membrane for different strain? 
2. How many times can I use the membrane?
Thanks in advance friends. 
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1.     Yes, as long as the size of strain sample is larger than poresize of membrane.
2.     Membrane can be used to concentrate the protein sample continuously
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I want to use nafion membrane in 2 compartment cell.The solvent I want to use inside the cell is organic & insoluble in water. Nafion membrane is stored in DI water. So for using an inorganic solvent, how can I dry or use the nafion membrane inside the two compartments of the cell for this water insoluble organic salt?
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So, Are you using a H-Cell ? (http://adamschittenden.com/admin/image_detail.php?id=1497). Some times ago I used a H-Cell for electrochemical CO2 reduction with Nafion membrane. I simply placed a nafion layer between 2 compartment of the H-Cell it worked out well.
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I wish to know the method and materials required to remove sputtered Ag or Au layer from the surface of a polycarbonate membrane used for the preparation of nanowires.
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For polishing there are plenty of fine polishing clothes, paper, teflon sheets available. For instance, you can use Diamond Lapping Sheet (1 µm Grit) from Thorlabs. But remember, this will damage the surface of your sample as well. 
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I have only small piece of membrane. Can I use further by boiling with H2O2 &  H2 SO4 ? Thanks.
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Yes my friend ; you can reuse it by following the procedure as represented in the attached file.
REF:
Fill/ Click:
Nafion 115 membranes are reusable or not when boiled in H2O2 and H2SO4
Reach/ Click:
• [PDF]
Agnieszka Złotorowicz - research.ncl.ac.uk; ; Newcastle ...
6. Pre-treated Nafion membrane drying at 80º C. Nafion 115 washing in boiling 3%H2O2. 1h rinsing in boiling distilled H2O. 1h boiling in 1M H2SO4. 1h.
Costamagna, P.. et al. Electrochimica Acta, 47 (2002) 1023-33.
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I am looking for a commercial Polybenzimidazole (PBI) membrane for fuel cell and electrolysis. Is it difficult to find it in the interne?
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I need to blot for interleukins which are all less than 50KD what membrane would should be used to blot it appropriately?
Thanking you
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Have not used the above antibodies yet.  In the 90's I developed an in-house ELISA with a polyclonal antibody as capture antibody and a 3E4 monoclonal antibody as detecting antibody.  Both were from SIGMA. For signal just anti-mouse conjugated to HRP and then TMB soluble substrate from Pierce (NB:You get both Western Blot and ELISA substrates with TMB).  For blocking use 2 % albumin.  For detection antibody and conjugate dilution use 0.1 % albumin in PBS/Tween (same as wash solution).  For washes use PBS containing 0.05 % Tween 20.
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I want to do fluorescence microscopy to identify the localization of a membrane protein with a periferal subunit. I need to prove if it is in the cytoplasm or if it is in the periplasm.
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EDTA treatment will disrupt the outer membrane specifically. The peptidoglycan cell wall can be disrupted with lysozyme. If these procedures are carried out in suitably high osmolarity, the cytoplasmic membrane will remain intact and the result will be spheroplasts consisting of the cytoplasm and inner membrane only.
By the way, periplasmic proteins usually have identifiable N-terminal signal sequences  that are removed by signal peptidase I or II when the proteins are secreted. The presence or absence of such a sequence should be a strong indication of a protein's natural location.
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I am doing research on FO-MBR, which give permeate with high salinity. as in literature FO-MBR remove above 99% COD. Forward osmosis membrane bioreactor
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In this case it is appropriate to measure the TOC. But you can try to measure t by diluting the sample and reducing the alkalinity ιν the limits of the method of COD (if not too high). See the attached file.
Do PH and C2 domains have different binding affinities for PI(4,5)P2-containing membranes?
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Is there any information available whether the PI(4,5)P2-binding affinity of PI(4,5)P2-specific PH-domains differs from that one of Ca2+-independent C2 domains? I read that proteins with PH domains can differ in their affinity against PI(4,5)P2-containing membranes, but is it also the case for different PI(4,5)P2-binding domains? Can someone help?
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My understanding is that most lipid-binding domains vary greatly in affinity (and selectivity), even within the particular classes of domain. Not all C2 domains bind to PI(4,5)P2. Maybe some of the primary references in the following reviews will help. 
What might be reasons of reflexes in roentgenogram during the investigation of membrane suspension by X-ray diffraction method?
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We have received reflexes from membrane suspensions under the large and small angles- looking for explanations.
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At small angles reflection can occur due to periodic ordering in the material. with best regards, uk
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I am working on osmotic membrane synthesis. If you have any recent research articles on this issue please give them to me.
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Thank u Andre Rieger sir.....now i got perfect direction, .....
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Can anyone give a physical explanation with regarding to the structure of Nafion membrane? Need to be easy to understand, cause I am not from Materials science or Chemical engineering.
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Hi Jeannie,
For more detailed and precise chemical structure of Nafion membrane, certainly you can look up for it in literature, or even Wikipedia can help. However, for short and simple explanation, it is a polymer membrane, with the main structure of the Teflon (or PTFE) which is hydrophobic, and with modifier parts containing -SO3H group, which give the membrane hydrophilicity and proton conduction. It is this hydrophilic domain containing -SO3- group to absorb water when the membrane is in contact with water. When this happens, the membrane absorbs water and swell.
So if you have the membrane in contact with water inhomogeneously/ununiformly, there will be parts that swell, and other areas remain dried and unchanged in physical size. This will produce the wrinkles in the membrane, as you observed.
In fact, if you submerge the membrane in water and make it absorb water uniformly, the membrane will swell uniformly and there is no wrinkle. It is the ununiform swelling that give the wrinkles.
Hope it helps :)
Kien Cuong
Can anyone help with pipe leakage?
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If a pipe has a small leakage, and we feed CO2 (e.g., 2 or 3 bar) through the pipe, we know CO2 will leak out, but how about the air? does air leak into the pipe due to partial pressure difference?
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Thank you for your answer-Alain
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We have a Beckman Coulter Delsa Nano C that provides zeta potential of membranes. But the software get us 2 different values: Zeta potential and Surface Zeta Potential (only when we are measuring membrane zeta potential).
What's the difference between those?
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It seems that in your case 'surface zeta potential' and 'zeta potential' are the same thing. Surface zeta potential refers to surfaces such as a membrane, zeta potential is the general name for the definition of the charge of any substance. However, when determining the zeta potential of particles in suspension (by direct relation to the electrophoretic mobility) this is also called 'zeta potential'.
The calculation of the zeta potential for surfaces and particles uses slightly different equations.
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How can I distinguish between proton conductivity and ionic conductivity?
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I have read something related and they used Impedance spectroscopy.
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I would like to conduct post-treatment using ethanol or glycerol but I could not find any supporting documentation on its effects.
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Post treatment depends on your membrane fabrication process and membrane materials. Some use heat treatment at different temperatures, some use freeze drying, some use different non/solvents like ethanol. You can wash your membranes with appropriate solvent for some time. Or you can prepare membrane module and by using a pump, you can run the non/solvent selectively either through one side or both side of the membrane.
Does anyone know which company supplies the auto-coating machine for preparation of composite flat-sheet membranes?
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see above
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Yes, to coat a thin layer on the top of support.
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I want to extend application scope of ceramic membrane in nonaqueous solutions. I wonder that is there exsit stable water-in-oil emulsions (W/O) without surfactant for experiment.
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Please read this article: Effects of temperature on water-in-oil emulsions stabilised solely by wax microparticles.
Maybe it'll help. Best regards.
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Hey everybody!
I have no signal for my protein (IkappaBalpha), but the control GAPDH is there. So I want to try an antibody from another company now. Is it necessary to stripp before incubating with the new antibody?
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I agree with the above but keep in mind that with stripping you will probably lose some of your target protein.  If it is present at low levels then it might be even harder to detect as a consequence.  Are the antibodies from the two companies different clones?  If so it may not be necessary to strip since they should detect different epitopes.  You can always strip the membrane after you have tried the new antibody and seen no signal.
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I have been using AccPbFRET to analyze my FRET data. I used to use ivision, which is too expensive. This software is free, and I have tested it with my old samples, and it proved to be OK, generating some consistent data. However, I am confused about the way that it took to get the mean FRET value from the FRET map. What is the "not NaN P.?" Does it count every pixel that I select or only the "not NaN P."? The FRET value also seems different then when I use high threshold to only highlight the cell membrane part and get FRET v.s. when I use low threshold >20 not to highlight the membrane, but used a ROI to select membrane part, and get FRET. Would these two ways of analysis give me different results?
Thank you so much!
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In attached paper is example of FRET between fluorescent protein and conducting polymer.
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Most of the articles only state using eggshell membrane pieces but they didn't explain how much did they used for the immobilization.
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I am planning to activate the eggshell membrane by using glutaraldehyde. I am doing a comparison on enzyme immobilization on rice husk and eggshell membrane and planning to use 1g of support material (rice husk and eggshell membrane) and I wonder whether the weight of the support material will affect the immobilization or not. I really need your opinion on this. Thank you.
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I have some six-year-old probes for microdialysis, 
I tried to run microdialysis with those probes but got no drug (even when I equilibrate it for 1 hour), I guess it is the problem of the semi-permeable membrane.
Can you recommend any way to reactivate them?
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Hi, did you keep the membranes moist over the six years? Most probably these are dried out, even, if you did not open the sealing. What material are the membranes made of? You could try to keep the probes in saline over night and then have a run again. Check the tip of the probes at high flow rates 4-10ul/min, we experienced "sweating" if they were damaged. If this is not the case try a standard solution for recovery experiments. 
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Can a doctor blade knife be used without motor ie. manually to cast a membrane on a glass substrate?
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Manually casting is commonly adopted on lab scale. Of course, you have to move carefully but in a firm manner.
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We know beta-catenin binds with E-Cadherin intracellular domain stably, while Wnt pathway is activated, beta-catenin will be released from membrane, however, what is the mechanism? 
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Caspase-3 cleavage of beta-Catenin
What are the differences between S. cerevisiae ER membrane and E. coli plasma membrane regarding membrane protein expression?
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Hello everyone, I am really grateful if someone knows some basic differences between S. cerevisiae ER membrane and E. coli plasma membrane. This information is regarding the expression of S. cerevisiae membrane proteins in E. coli. thanks in advance
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The main difference between these membranes arise from the fact that the ER membrane of an eukaryotic organism has the property to form microsomes and/or vesicles for protein transport to another organelle or into plasma membrane. And the prokaryotic membranes do not carry this process out; to mobilise proteins from their cytoplasm into another prokaryotic organism or even into an eukaryotic organism they make use of their protein secretory systems (e.g. Type three secretion system).
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I want to transfer 10 kbp DNA from my polymer membrane to Zeta-Probe membrane using southern blotting method. Normal way to move DNA for southern blotting is from gel to membrane but in my case I want to move DNA from my polymer membrane to Zeta membrane. I have bio rad elecrophoretic transfer cell made by Bio-rad. Also, for detecting DNA on the Zeta membrane, I am looking for florescent dye. I just want to dye whole transferred DNA fragments on the zeta membrane. Please help me.
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Thank you John. I 
How can I synthesize very small size LiCl or NaCL nanoparticles?
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I need very small sizes to be able to use as a porogen. Particles of a specified shape and size, used to make pores in moulded structures or membrane (case of study).
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Precise control over reaction temperature and selection of a suitable capping agent may results in small sized nano-particles.
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Hi all, I work use the SEPA CFII membrane cell from Osmonics and it was provided with different shims and feed spacers. I know that they allow to process the fluid in turbulent conditions. But how can I know which is the best? I need to test it every time I do an experiment? Can anyone one help to calculate the Reynolds number for the SEPA CF?
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Good Morning. Please find attach the link. Regards Ariadne Tsambani
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For a fibre optical pressure sensor system as shown in the paper by F. Ceyssens et al what is the maximum frequency response one could expect? What are the differences in frequency response between a bulk silicon micromachined membrane and a SiC membrane?
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The frequency response/resonance frequency depends on both the material and the structure of the system. So, the inital material of the fibre gives you some hints about the specrum however, it is changed within different structures and I think the experiment is the only way to investigate it. Cheers,N
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See above
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What is the liquid and what are you trying to separate?
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I want to prepare a membrane from solid aromatic block co-polymer for fuel cell applications. How do I do it?
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Thank You Dr. Meenakshi, Can you support me with any detailed Example of the membrane preparation and fuel application.
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I am working on efflux pump proteins nowadays and trying to have predicted membrane topology of some of these. Actually, I tried some open source tools like Protter. Is there any other tool that you really recommend, maybe more advanced?
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The best to look at is OPM -> http://opm.phar.umich.edu/
If you want a more detailed prediction of the protein helices and position, you can have a look at topcons which is one one the most highly relevant according to litterature: http://topcons.cbr.su.se/.
You can also have a look at David Jones tools: http://bioinf.cs.ucl.ac.uk/psipred/
There are other tools, but for a start, they should give you some good starting points.
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I am trying to extract membrane proteins of C. Glutamicum. I am finding out alternate methods because an ultra centrifuge is not available. I tried spinning at 18000 rpm and I got a small amount of membrane fraction. But its not enough for my assay.
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What's your further experiment for these proteins? If you only need them to do activity assay, you can try to solubilize the supernatant with Triton/other detergent after 16000rpm. And then if enrichment is needed, you can concentrate the sample and run one cycle of gel filtration or ion exchange column.
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The supercapacitor we made out of electrospun membrane has high voltage of about 2.6 volt, but it discharge so fast,  with in few seconds. so we are unable to glow LED using the supercapacitor. we used brush coating method to prepare electrode.should we use different coating  technique .........                                                                                                                             
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If it is self discharging very fast means either the capacitance is very low or the material has high resistance. what electrode and electrolyte system are you using. Try to glow LED with a conventional system first such as Activated carbon electrode prepared in Ni foam or Al current collector with 6 M KoH or 1M TEATBF in acetonitrile electrolyte 
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Unable to see small proteins on my transfer to PVDF membranes.
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Either approach should have the same effect. Use whichever is more convenient.
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In terms of the expression and characterization of efflux pump proteins, there seem to be several setbacks due to their trans-membrane nature. One method that I know of is the denaturation of the membrane by using Urea, and then attempting to renature the proteins. However this does not seem a suitable method for retaining a sufficient level of the protein activity, thus making further analysis difficult. If possible suggest more suitable methods for the same.
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You can always try to re-modify your clone to allow the express of protein towards the membrane fraction of the bacteria; that way you can somewhat obtain the membrane protein in the native-like state and use different mild detergents for refolding of protein without interrupting/denaturing the structural integrity of the protein. Please take a look at our paper for reference.
Another way is cell-free expression that are being used more and more these days. I also attached a reference here for you to take a look
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I would like to prepare anodized alumina membrane (AAO) in the laboratory but I am totally unaware of the instrumental set-up specification. is it possible to procure a ready to use set-up directly? if yes please suggest the names of manufacturers. If NOT, please let me know what should be the necessary equipment and their specifications
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Dear A. Suresh,
the basic equipment you will need for anodization would be a temperature controlled thermostatic bath, some dc current sources ranging to high enough voltages (depending which processes of anodization of materials you like anodizing), multimeters for controlling the current/voltaje, and a computer connected for data registration of current transients would be of much helpful while not mandatory. A pH-meter would be also of great interest. Some manufacturers you could try would be Thermohaake, Keithley Instrum., Selecta, etc.
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I learned from a paper that membrane capacitance was calculated from transients evoked by 10 mV voltage step. I do not understand. Who can explain it for me? I appreciate it.
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You should go for standard utility in Clampex called Seal test (or Membrane test, sorry, do not remember correctly). The software will do rough calculation for you automatically. Basically it does it by measuring the rate of transient current decay: Thau=R*C. R is calculated from Ohm's law I=U/R automatically too. During Seal test procedure software measures R, finds time when current becomes e (exponent) smaller from its peak value and that is it! The important thing you should remember is to compensate you electrode capacitance, because it contributes to your transient current. And if you want to measure the capacitance of entire cell, you should do your experiment in whole-cell configuration. So in general you should do following:
1. Turn on Seal Test (or Membrane test) on amplifier.
2. Place your electrode in bath solution.
3. Compensate your electrode capacitance (do not see transient anymore).
4. Form the gigOhm contact.
5. Break the membrane (i.e. obtain whole-cell configuration)
6. Observe the reappearance of the transients. Don't do any compensations. Now your Seal test (Membrane test) will show you the capacitance of membrane of entire cell. It may sound too busy, but in real experiment - 1-2 minutes
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I got some PVDF ultrafiltration hollow fiber, and they have been placed and became dry a few month. I know that will cause a irreversible damage, but how can I activate them and use for flux analysis?
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Fiber dried will lead to permanent damage from pore shrinkage or increasing in fiber brittleness, but you may try to soak your dried fiber in ethanol to re-open membrane pore. In our experience, soaking dried membrane in a solvent can significantly increase membrane permeability.
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I am looking for microporous ultrathin membranes (25 micron or less thickness) from PTFE, PVDF, PP.
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Hu Chaoyang
Can you tell me more about PVDF membrane you made (specially porosity, thickness)
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In Malate-aspartate shuttle oxaloacetate first convert to malate and then pass inner mitochondrial membrane. in matrix of mitochondria oxaloacetate regenerated from malate.
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Basic purpose of malate-aspartate shuttle is to transport reducing power (NADH) generated in cytosol into mitochondria. This shuttle involves two antiporters - one exchanges aspartate with glutamate and the second one exchanges malate with alpha-ketoglutarate. It is obvious that there is no oxaloacetate transporter or oxaloacetate-malate shuttle. To the best of my knowledge oxaloacetate is synthesized and its threshold level is maintained in mitochondria to take care of Kreb's cycle and synthesis of linked organic molecules (in particular keto-acids needed for synthesis of amino acids etc.) .
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Please explain why I am not getting signal for my protein on upper half of the membrane blotted after 2D electrophorosis while lower region shows nice spots of control?
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How can I make a polymer inclusion membrane using DMSO as a solvent?
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I have synthesized an organic compound having solubility only in DMSO but because of the high boiling point of DMSO it is not getting vaporized thus I am not able to make a membrane. And if i take a mixture of the solvents : dicloromethane and DMSO then phase separation occurs.
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have you tried with vacuum? you may try vacuum dry at 80C
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For finding out the concentration polarization, the K value is very very important.
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A rather simple method is the velocity variation method. If you haven't tried that yet you find a brief description in Berg et al: Mass transfer coefficients in cross-flow ultrafiltration, J of Membrane Science 47 (1989) pp. 25 - 51. It is termed the velocity variation method and described in the named paper.
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I have separated a crude mixture of protein by ammonium sulphate precipitation method (70%). I now want to separate a specific protein of about 66 kDa in size. I am a bit confused about the use of a dialysis membrane. Can someone suggest which type of dialysis membrane I should use to separate the protein(66 kDa)?
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Assuming you want to keep your protein native I would use gel filtration and ion exchange to further purify your protein. Success of these downstream purification procedures will depend on how complex your 70% ammonium sulfate precipitation mixture is. If your 66kD protein is a prominent band by SDS-PAGE, dialysis using a 30K MWCO membrane into a buffer such as PBS should allow you to do gel filtration using a column similar to a Superdex 200 column. You will then need to transition fractions eluted containing your protein of interest into a low salt buffer and further purify using cation or anion exchange depending on the isoelectric point of your protein. This approach has the potential to yield protein that is quite pure.
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Type II membrane proteins are proteins spanning the membrane once, with its N-terminus on the cytoplasmic side of the membrane. The transmembrane domain is located close to the N-terminus and it functions as an anchor.
How does such a topology look if a type II protein is inserted in a subcellular organelle membrane (e.g. endoplasmic reticulum, Golgi, plastid)? Is the N-terminus exposed to the lumen and the C-terminus to the cytoplasm?
I would be grateful for some authoritative literature.
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You can take a look at this review for membrane protein insertion at endoplasmic reticulum http://www.ncbi.nlm.nih.gov/pubmed/21801011 it includes the type II membrane proteins
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Pervaporation seperation of close boiling mixtures.
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Based on my experiments PDMS
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The membrane of alginates.
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You can prepare a membrane using alginate via multi-valent metals (Calcium salts) as cross-linking agents.
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Tried cleaning the membrane several times with HCl, but there is still some concentration of the dye present in the permeate as well as reject.
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Before I can answer you question, I need more information as follows.
(1) What are the properties of the NF membrane you used? What is the MWCO and surface charge density?
(2) What is the concentration of the methylene blue in the water? Does it snythetic solution or industrial effluent?
(3) What are the operating conditions?
I hope it is still not too late to ask you since you have posted the question in Jul 2013.
How to convert to the equivalent energy consumption in different separation methods?
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In MEA system, the energy consumption includes two parts, the thermal energy for reboiler and the power consumption for solvent pump, blower and CO2 compressors. While in membrane processes, only the electricity used for the compressors and vacuum pumps. How to convert heat duty in amine system to the equivalent energy consumption in order to compare the energy intensity with membrane process?
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In my work, I used the equivalent work correlation proposed by Van Wagener and Rochelle, 2011 (Chem. Eng. Res. Des. 89 (9), 1639–1646), in which  all the electric power requirements and the term accounting for the reboiler duty are summed up. In principle, this allows you to estimate how much useful work would have been produced if the extracted steam was fed to the turbine. Although this correlation does not account for the drop in the steam pressure downstream the extraction point, which can be important as shown in one of my papers, it would allow you to compare different technologies. 
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Hexagonal H-II inverted cylindrical phase of lipids does not obviously fit with fluid mosaic lipid bilayer structure of biological membranes; yet MGDG in thylakoid membranes dominates - how?
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I personally suspect that the high content of transmembrane helices in the thylakoid membrane might be an important factor to stabilize the bilayer. The exact (more or less) lipid composition is present in the prolamellar body (PLB) which forms in etioplasts and in this is characterized by a cubic phase. On the other hand, the very high content of protochlorophyllide-protochlorophyllide reductase complexes might play a role in maintaining the cubic structure of the PLB. Soon after illumination which induces transformation of the protochlorophyllide to chlorophyllide the PLB "dissolves" and lamellar structures start to form. The attached paper seems like a great source of new information on this topic. I will read it and possibly revise my opinion.
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Using solvent- antisolvent method , same sheet of synthesized membrane, same Temp, TMP, humidity, thickness, and same casting solution chemical- physical properties.
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Please check the phase inversion kinetic, different rate of coagulation will significantly affect the properties of membrane i.e. the change from delayed demixing regime to instantaneous demixing.
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I'm making polymeric membrane by phase inversion method. After dissolving polymer in solvent i put the dope solution in a dark place. After 24 hr cast it on a glass and immerse it in non-solvent bath. My casting knife is automatic. But in all of my membrane there are 3 or 4 bubble.
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If you can use of an ultrasonic bath you can remove bubbles from your solution rapidly and completely.
Pay attention during using ultrasonic the temperature of solution increase rapidly.
how can an ultrasonic bath change the properties of your nano particles?
Specific energy consumption for CO2 capture.
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Considering different processes for CO2 capture e.g. absorption, membrane and cryogenics, how could we compare the energy consumption? In chemical absorption, the main energy consumption comes from the stripper reboiler (heat duty), while in a membrane process, the main energy consumption comes from the compressors and vacuum pumps (power or electricity) and cooler (heat duty). We know the price between heat and power is different, so how can we convert to the same base to compare the specific energy consumption (GJ/tonne CO2 capture) in different processes?
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You must take into account all energy needed for each unit operation or process for CO2 removal. For instance in gas absorption you have to come to a nt value of energy (in J) needed for capture of 1 ton of CO2. Do not forget anything: calculate the energy you need for the reboiler, pumps, energy released from the absorption column and balance these items. Then you will arrive to the net specific energy consumption (J/ton CO2). Do the same for other processes and you will be able to compare them. Also take a look on the following paper which is, actually, a classic on this topic: Rao and Rubin, Env. Sci. Tech., 36, 4457/4475, 2002.
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coal gasification; H2 production
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Hot ceramic filters can do a great job on particles. Then add a second filtering stage (i.e. scrubber)
Dispersion of carbon nanotubes in a polymer solution
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How can I disperse the CNTs in a polymer solution evenly? I tried ultrasonic, but the CNTs still aggregrate together if I add a relatively high content of CNTs (e.g., 1-2%). After dispersion, I used a 10um filter to remove some impurities or larger particles, but the filter was totally blocked by the CNTs, does anyone have good suggestions?
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@Soujit Sen Gupta "I agree with Pavel. Only solution is surface functionalization." This is simpy not true, unless you want to include physical association between the CNTS and agent in that defintion. I think most of us understand "surface funcationalization" to mean either covalent grafting of some molecule to the CNT surface, or some other treatment, such as oxidation, that disturbs the CNT surface and renders it reactive. Simple mixing with nonionic surfactant with sonication followed by either centrifugation or settling by gravity (can take several days--do you have time to wait?) will produce well-dispersed CNTs, usually as single tubes, in the supernate. Several papers have been published by various groups that show the surfactant tends to wrap around the CNT. If you want to have some additional properties, such as covalent bonding to a matrix, then choose a surfactant that includes an appropriate functiional group for further reactions. I have not seen any papers describing the use of titanate or zirconate coupling agents in this role, but I suspect they will also work, if your final product can tolerate having some organo-metallics like these. By the way, don't bother with gum arabic. As I recall, this was the first publication that demonstrated reasonable dispersion of CNTs. The idea was based on ancient processing that used gum arabic to disperse the solids in ink. The results are not very good compared to using surfactants. A good dispersion of the CNTs in the polymer matrix is not the only thing that should concern you. What about compatibility between the CNTs and the polymer? If your polymer is soluble in the same solvent used to disperse the CNTs, you may get a very nice dispersion of the CNTS in the polymer solution, but what happens as the solvent is removed? Unless the CNTs have been made to be very compatible with the polymer, you will get a non-homogeneous solid that has individual domains of polymer and of CNTs. If the compatiblity is especially poor so that the interface between the polymer and CNT is poor, there will be a number of physical properties that suffer. If you are dealing with extrusion polymers, then you will have the problem of getting your well-dispersed CNTS to be uniformly dispersed in the extruded polymer. Even a twin-screw extruder won't do a very good job. @He You said "Adding surfactant may introduce some extra impurities". What impurities? You can purify a commercial non-ionic surfactant by passing through an HPLC column. ANY kind of modification you do to the CNTs to disperse them or make more compatible with the polymer could be considered as an impurity.
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What is the the size range and chemical nature of nanoparticles which can pass through cell membranes? If it is not permeable how can we induce its permeability?
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Usually 14 to 50-nm-size particles are the most efficient in their uptake. In order to increase this uptake you can functionalize the nanoparticles with specific biomolecules that enhance the cellular uptake, such as cell penetrating peptides (TAT and RGD peptides for example).
Please check these papers (see my profile to get them) where we use 14nm gold nanoparticles functionalized with these peptides for in vivo gene silencing and tumour targeting:
In vivo tumour targeting via nanoparticle-mediated therapeutic siRNA coupled to inflammatory response in lung cancer mouse models.” João Conde, F. Tian, Y. Hernández, C. Bao, D. Cui, K.P. Janssene, M.R. Ibarra, P.V. Baptista, T. Stoëger and J.M. de la Fuente. Biomaterials (2013).
“Design of Multifunctional Gold Nanoparticles for in vitro and in vivo Gene Silencing.” João Conde, A. Ambrosone, V. Sanz, Y. Hernández, V. Marchesano, F. Tian, H. Child, C.C. Berry, M.R. Ibarra, P.V. Baptista, C. Tortiglione and J.M. de la Fuente. ACS Nano (2012), Vol. 6, pp. 8316–8324.
CO2 adsorption in polymer materials for high pressure gas separation
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Most polymer materials, typically rubbery polymers, suffer the CO2 plasticization at high pressure, what is the principle? High concentration CO2 adsorbs into the polymer matrix, then the polymer chain starts to become flexible. The plasticization pressure is mainly dependent on the material properties, does anyone know what is the CO2 partial pressure for the plasticization of polyvinyl alcohol?
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To comprehend the principle of plasticization of PVA you could read the article: Free Volume and the Mechanism of Plasticization in Water-Swollen Poly(vinyl alcohol) Hodge, R. M.; Bastow, T. J.; Edward, G. H.; Simon, G. P.; Hill, A. J. Macromolecules, vol. 29, issue 25, pp. 8137-8143 A similar theory can describe the carbon dioxide effect . For CO2 partial pressure data see too: Plasticization of gas separation membranes M. Wessling, S. Schoeman, Th. van der Boomgaard, C.A. Smolders Gas Separation & Purification Volume 5, Issue 4, December 1991, Pages 222–228
Robeson upper bound.
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Most researchers in the membrane gas separation field are using Robeson upper bound to characterize the improvement of their membrane performance. However, people need to think about two important parameters before comparing their data with upper bound: 1) Testing condition, those polymeric membrane were tested at 2 bar, and we know high pressure will decrease the membrane performance a lot for many polymeric materials. 2) For asymmetric and composition membranes, we can not using permeability to characterize since the actual thickness is difficult to measure. Therefore, the standard upper bound should consider the specific applications: a) CO2/N2 from flue gas, set 3 bar, actually 2 bar will lead to a very low CO2 flux, and then results to a larger membrane area based on the simulation results in some literature. b) CO2/ CH4 in biogas, 10bar c) CO2/CH4 in natural gas 30 bar
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Asymmetric and comosite membranes, permeance is usually employed instead of permeability, while many researchers misunderstand the two items.
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I synthesised flat sheet membranes and want to test their fouling potential by passing wastewater through the membrane and then analyzing the filtrate. I wanted to have a perspex cell made with two chambers. I want to clamp the membrane in the middle of the two chambers, have wastewater in the first chamber and the filtrate in the second chamber. Has anyone done this before and can you provide me with a schematic or image of the set-up?
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Hi Heidi,
Are you going for dead-end or cross-flow filtration? If it's the latter, well, I was looking for something similar myself (I'm currently experimenting with flat metallic microsieves), and the set-up described in the link below pretty much did the trick for me -- as a bonus, it comes with detailed schematics and the list of components:
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I plan to culture the HUVEC cell line CRL-1730 on a permeable membrane. Which one is better- polycarbonate membrane, polyester membrane or PET membrane? Also what is the optimum pore size for studying HUVEC permeability- 0.4, 1 or 3 micrometer?
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I'd guess that your cells would readily migrate through the 3um pore membranes...
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My membrane material is of PVDF, and its category is flat sheet.
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Gas gravimetric sorption with magnetic suspension balance could be an option.
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As far as I understand it, it minimizes the surface energy along each face, which represents what is happening in reality to liquids. There are some examples which claim the simulation behaves similarly to a real droplet.
Two books might help you:
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Is there any formula or estimation for the change of critical micellar concentration (CMC) of detergents in different buffers (with different ionic strengths), since I know that the cmc of detergents decreases drastically in the presence of salt.
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Good question. To my knowledge there is no formula to do that. The reason is that different detergents respond differently to ionic strength. As you correctly noted, CMC will go down as ionic strength increases, but how much it goes down varies depending on the detergent. For example, at 0-50 mM ionic strength, the CMC of SDS is 0.2-0.3%, whereas at 100-200 mM the CMC is .03-.06%. In contrast, the CMC of octyl glucoside, MEGA 9, and others don't decrease much at all when ionic strength is increased from 0-50mM to 100-200mM, and the CMC of CHAPS only decreases by about 2-fold. These values are taken from a pamphlet published more than 20 years ago by Calbiochem entitled 'A Guide to the Properties and Uses of Detergents in Biology and Biochemistry.' In my lab our 'rule of thumb' is to use detergents in buffers that have ionic strength no less than 100mM.
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plasma membrane
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There are individual ions which in many cases remain completely solvated, but, for example, though magnesium is usually fully solvated in the presence of chloride, it will bind in the active site of many ions, and to phosphate. In general, you can follow the work of Yun Lou and Benoit Roux on osmotic pressure to see if a given molecular dynamics force field forms too many of these ion pairs (a common problem), and the work by Kim Collins on water affinities for the main ideas behind predicting which ions form lots of ion pairs and which form few.
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We recently bought this membrane for Western blot analysis and it seems that it is two-sided (one smooth and one rough). There are no details on how to use it. Is there a preferential side that should be in contact with the gel? The lab is also experiencing some problems in transfer, so I was hoping someone could explain the issue. Any suggestions?
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the smooth side is the surface with PVDF. for future purchases, in my opinion, millipore PVDF works much better!
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Our aim is to separate VFA's from medium undergoing anaerobic fermentation
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Is it for laboratory purposes or for full-scale design?
Can caveolin-3 be secreted like caveolin-1 or is it always plasma-membrane bound?
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In my opinion the CDS sequence given from the original NM_001234.4 sequence results in a human caveolin-3 expressed in the membrane. I'm right now in a middle of a discussion, trying to find out if this sequence gives a secreted or a membrane-bound protein. Can anybody help?
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Caveolin 3 has a transmembrane region starting around 78 AA to 100 AA based on TMHMM version 2 models. hence it cannot be secreted. Kindly look at the attached word file based on AA sequence from Danio rerio
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Lipids in membrane bilayer do exhibit few types of motion, e.g: rotational motion, translation motion, vibration and so on. But I am quite unsure how the motion would like to be for axial diffusion.
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Axial diffusion is diffusion of lipid molecules within the same side of bilayer membrane. This kind of diffusion of lipids is very common and its rate is really high. There is another kind of diffusion of lipid molecules called "Lateral Diffusion" in which lipid molecules of the bilayer membrane of one side diffuses to the other side of lipid bilayer although this diffusion rate is quite slow
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I'm writing my thesis and in order to explain the different polymers used, I would like to group them by "types" or "classes" (with similar chemical structure of the elemental unit and properties).
The polymers I'm talking about are:
Polysulfone (PSU), Polyphenylsulfone (PPSU), Polyethersulfone (PES) and Polyetehersulfone with Cardo group (PES-C). (See attached file)
Although I've found that Blanco et.al. and Yamagishi et.al. consider these polymers to belong to the same class, they differ in the name given to the "family".
So, I'm not really sure if:
(1) it is correct to group them
and, in case it is,
(2) which would be the correct name of the "family": poly(arylsulfones), polysulfones... ?
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In my point of view, the PSU, PPSU PES PES-C are thermoplastics with some change in functional group and stereo-chemistry, rather they belong to same family, for more details I have pasted some links for further information, Please read them
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I am studying the interactions between an antimicrobial peptide and PG-containing LUV via ITC (VP-ITC from Microcal). My earlier experiments revealed a PG/drug binding ratio of 2 quite consistently, but after repeating these titrations recently, using materials prepared in the same way and under the same conditions (hopefully), N seems to be increased to between 2-4 with significant variability. dH and K from both sets of experiments are consistent. Has anyone seen such irritating results?
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Its not easy to answer this question without looking at the different titration curves that you have generated. Of course solubility and stability of your reagents could play a role but you should also consider the concentrations of your sample relative to the affinity values you are generating from the fitting (the c-value).
Recall that c=Ka*[receptor]*n
This shows that n is affected by the experimental design just as much as the other parameters. You wouldn't generally be concerneed about a 2-fold difference in expected Ka (eg 1X10^6 vs. 2X10^6 M^-1) but a 2-fold error in concentration or n makes you seriously question your data, even though according to the c=value equation these effects are equivalent. To accurately determine n from an ITC experiment the c value should be as high as possible since this minimizes the effects of errors in the determination of Ka.
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Also, does anybody know the details of manufacturers of the membrane (preferably in India)?
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Dear Rambabu,
Closely related PEK-C (alternative name PEEK-WC) membranes can be prepared either by wet phase inversion or dry phase inversion to get asymmetric dense or porous membranes, or by solvent evaporation to get symmetric dense membranes. A very complete overview is given in the attachment. Please see references therein for the exact procedures.
I have no personal experience with PES-C, but I have enough experience to know that everything thas is valid for PEK-C is in principle valid for PES-C. Depending on the polymer grade (molar mass etc.) you will have to do some optimization of the best preparation conditions.
Unfortunately I have no information on possible producers of the polymer or commercial membranes.
Kind regards,
John Jansen
What is the meaning of negative Zreal value in Electrochemical Impedance Spectroscopy of polymer membranes tested in a 2 electrode set-up?
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The conductivity of the membranes is calculated from the Zreal value corresponding to the intersection of the curve at the "zero" of the Zimag. If the interception gives a negative resistance value then how to calculate the conductivity?
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Thanks for the suggestions Oleg. As far as I know the resonance or inductance should result in negative Zimag, but not negative Zreal.
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A "plate" is a solid body bounded by two surfaces. The distance between the two surfaces defines the thickness of the plate, which is assumed to be small compared to the lateral dimensions.
But what is the border between the membrane and plate?
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Membrane and Plates have basic differences in structural behaviour. Membrane sustain transverse loading using inplane stresses. While plates sustain loading using bending stresses. 1-D analogous examples are difference between a thread/cable and beam.
If the bending stiffness of the plate is reduced to zero, it will act like a membrane with due consideration of boundary conditions.
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In some case we want to get the cell membrane inverted out which is so called inside-out vesicles. (For example E.coli membrane). But I don't know much about the detail about making such vesicles. Can anyone help me?
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Method for preparation of uniformly oriented and sealed inside out vesicles (ISOv) from Escherichia coli cells was further developed and published by our group in Bogdanov, M., Heacock, P. and Dowhan, W.: A polytopic membrane protein displays a reversible topology dependent on membrane lipid composition. EMBO J. 21: 2107-2116, 2002. To prepare ISO vesicles Escherichia coli cells were ruptured using a French press at 560 kg/cm2 (8000 p.s.i. THIS PRESSURE IS CRUCIAL!). Orientation of membrane vesicles was verified by new vesicle sidedness assay by taking advantage of mapping of uniform topology of essential E. coli protein leader peptidase (Lep). Please see Materials and Methods and Supplemental material to EMBO J. 21: 2107-2116, 2002 manuscript for details of both protocols respectively.
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I am looking for a recipe for wet blot transfer with TRIS-HEPES buffer (in combination with NC membranes).
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I am rather interesting in this, first i thought i misunderstood something, next i realized that tris-hepes-sds running buffer for page is existing... nice. than transfer buffer exists. it looks to me it is expensive to change simply glycine to hepes, but surely, must be something to be worth it.
How to calibrate water vapour in GC?
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I want to know how to calibrate water vapour in GC or MS in order to detect the water vapour content in a gas stream.
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an other option 'Determination of water in gases and liquefied gases with the 875 KF Gas Analyzer'
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Can you suggest some methods to increase the hydrophobicity and surface roughness of a polymeric membrane surface? Is it possible to make the surface of a hydrophilic polymeric membrane in to superhydrophobic by any means of surface modification?
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You can use plasma nanotexturing with a CF4 or C4F8 gas. Also plasma nanotexturing with O2 or Ar gas followed by deposition of a thin layer of PTFE, C4F8, pFOTS etc.
I propose plasma since you can modify both roughness and chemistry with one machine.
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Might it be related to size and water filtration?
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I am using PVDf as polymer and NMP for solvent
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The immersion time shoud be more in all cases of fabrication of membrane by phase inversion and in case specially when the polymer take time to ppt, so more time is needed.
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Biofouling is caused by the adhesion of microbial slimes on the membrane.This needs expensive periodic cleaning.
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Membrane properties such as pore size, hydrophobicity, pore size distribution, membrane material,Solution properties such as concentration, the nature of the components,particle size distribution,Operating conditions such as pH, temperature, flow rate and pressure affect membrane biofouling.
It can be minimized by strategies such as cleaning, appropriate membrane selection and choice of operating conditions.Membranes can be cleaned physically, biologically or chemically.
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I want to show a reduced membrane abundance of AQP2 in paraffin-embedded mouse kidney IHC. Therefore, I'm looking for an apical membrane marker. Already thought of Na-K-ATPase, but as expression is mostly basolateral, I won't be happy with that, what do you think? Maybe you have further suggestions on how I clearly can show AQP2 in membrane vs. vesicular abundance? Thanks a lot in advance
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Proton pump and bicarbonate/chloride exchanger are good markers of apical Intercalated cells. These cells are intermingled with Collecting Ducts cells.
I hope this help, cheers
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The conventional thermal desalination have much higher fluxes than membrane distillation. Why MD flux is not as high as the flux of the conventional units?
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Suggested reading:
ADNAN, S., HOANG, M., WANG, H. & XIE, Z. 2012. Commercial PTFE membranes for membrane distillation application: Effect of microstructure and support material, Desalination 284: 297-308
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I want to know the mechanism behind an AC electrical field which affects/helps the formation of GUVs in the 'electroswelling method'. I know the hydration of lipid film will eventually lead to the formation of vesicles when the lipid concentration is above CMC. Applying an electrical field seems to accelerate the vesicle formation process and make the size of vesicles larger. Also, I heard that the electroswelling method will yield more unilamellar vesicles.. But how does an electrical field achieve all these? Also, what should be the principles guiding the choice of the frequency and amplitude of the applied electrical field? Will there be any restrictions on the charge of lipid head group? Thanks!
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Hi Zheng,
Below is a very good review about GUVs. In particular, references 3 and 4 of this review discuss how to prepare mixtures with negatively charged lipids. You will need to change frequencies and voltages as compared with zwitterionic lipids. In general, I would say it will be very uncommon to produce asymmectric GUVs by a simple electroformation. However one common problem is that the lower-Tm lipids will be hydrated faster that the higher-Tm lipids. You can have problems if you work at a temperature that is below the Tm of one of your lipids. Make sure to be above the Tm of the mixture you are using. Also, longer times and bigger concentrations of lipids in the wires or the ITO help obtain GUVs with more homogeneous compositions. (use at least 10 mg/ml of lipids in solvent).
Biochimica et Biophysica Acta 1798 (2010) 1324–1332
GUV preparation and imaging: Minimizing artifacts
Nelson F. Morales-Penningston a, Jing Wu b, Elaine R. Farkas c, Shih Lin Goh b, Tatyana M. Konyakhina b,
Judy Y. Zheng b, Watt W. Webb c, Gerald W. Feigenson b,⁎
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Purification of liver protein
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Purify by homogenizing in 0.25M Sucrose, 50mM HEPES, 1mM MgCl2 with protease inhibitors. Then do a sucrose gradient using an ultracentrifuge. You can look up how to purify microsomal cytochrome P450 to determine how to make the sucrose gradient. Take the layer that has your activity or proteins and then depending on what you want to do, you can solubilize with detergent, and then do standard chromatography such as ion exchange and affinity chromatography.
What you do, depends on what proteins you are trying to obtain, and if they can survive in detergent. The detergent is usually non ionic like NP40 or DDM. Sometimes Triton X 100 is used. The detergents need to be tested empirically to see which one is best suited for your needs. And the best method depends on your protein as well.
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The membrane is made of the following materials: PVDf, polypropylene, and polyester. Its category is flat sheet.
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I realy like DMA as a method and it is a very good method to learn about the mechanical behaviour of your baterial but in my opinion DMA is not a suitable method for measuring the tensile strength, but it will give you the (complex) modulus of your material.This might also be an interesting value for you. Also the position of transition processes can be determined.
To determine tensile strength you have to perform tensile testing. As this is a standard test it should be easily available.
Which way can be used for separation of soluble nitrate from water in industry scale?
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Please express ways that used the membrane methods.
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[1]RO and ED (mainly) can be used to remove nitrates on a small scale. The ED based methods use electric current to pass cations or anions through SPM. But the current can be adjusted to pass only the cations and reject nitrates. But these current based technologies are high cost technologies. [2] Recently, hollow- fibre membranes are used. Atotropic bacteria (from certain plants) is grown out side of the membrene in water containing nitrates while H2 is slowly supplied with in the membrane. Nitrates and O2 permeate into the biofilms grown on the membrane which reduce nitrates to N2 in the following steps: NO3 (-)---NO2(-)--- NO(g)---N2O(g)---N2(g). [3] The membranes are impegnated with finely divided extra pure Fe. The industral water containing nitrate is allowed to pass repeatedly which ultimately changes nitrates to N2(g).The PROBABLE mechanism ( though not confirmed but reported in the literature) is given below: Fe(0)—Fe(2)---Fe(3) ---NO3(-)—NO2(-)--NO(g) ---- NOH---N2O2H2-----N2O----N2 (2). [4] Chitosan [CS] based membranes are exploited for the use of removal of nitrates from industrial water and are met with with some success. Chitosan is a linear polysaccharide composed of randomly distributed β--linked D-glucosamine and N-acetyl-D-glucosamine. It is made by treating shrimp and other crustacean shells with NaOH.
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How they are affecting the processes?
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"Bad" are biofilms formed in pressure-driven membrane processes such as RO; NF; UF and MF. In these operations, they reduce the solvent (water in most cases) flux and cause bio-fouling. "Good" are biofilms formed in membrane biofilm reactors, where they are intentionally grown in order to catalyze desired reactions. Thus, they allow for combining reaction and separation steps in an integrated process, which can be advantageous in a number of cases.
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Is there a simple method to synthesize graphene from graphite flakes?
I would like to use the synthesized graphene in membrane fabrication.
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you can make it from Commercially-available expandable graphite flakes (GIC), whic is intercalated with a mixture of sulfuric acid and nitric acid . This mixture has to heated at 700 (EG) flakes. These EG flakes sonicated in acetone and dried in air leading to expanded and sonicated graphene stacks.
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I used to fabricate highly porous and hydrophobic macro porous membranes. But they are single layer and thicker (>100 microns). Suggestions for the fabrication of thin film hydrophobic macro porous layers are much appreciated. I prefer to fabricate these thin film membranes on any hydrophilic supports.
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Micro-arc Oxidation (MAO) is one method to produce micro porous coatings. The porous size can be varied from micron to nano scale. The surface morphology of the coatings may not uniform in the micro scale range. MAO method is derived from anodisation which is also called Plasma electrolyte oxidation.
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Developing PES based HFM for UF applications at 60 K MWCO i need some one help to proper guidance
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Polymeric hollow fiber membrane or ceramics hollow fiber membrane?
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In a project we need to stain bacteria (Gram-negative and positive ones) with a fluorescent dye for detection. It would also be ideal if the dye would absorb strongly in the UV range but would emit in the VIS range. Advantageously the dye had a high quantum yield. We tried semi-conductor particles - Quantum Dots - to stain the membranes. These would be ideal but the hydrophobic QDots are difficult to suspend in aqueous solutions (as expected…) and other types of QDots with surface coatings do not interact with the bacterial cells. Thank you for any advice!
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Do you just need to stain the membranes, or is it ok if the whole bacteria light up? If the latter, acridine orange is cheap, easy to use, and meets your other preferences.
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All gram negative microbes have a unique signature molecule - lipopolysaccharide - abundant in the outer leaflet of their outer membrane. What advantage does it provide to the organisms?
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LPS interferes with deposition and activation of the complement system, enabling bacteria to evade host's immune response. Also, lipid A activates macrophages that produce profuse amounts of proinflammatory cytokines damaging host's tissues, this also enables bacteria to evade the immune response.
What is the simplest method for examination membrane porosity?
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 simplest method for examination membrane porosity
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Scanning electron microscopy is certainly the simplest and fastest method for examining the porosity, as it will show immediately if porosity exists or not, and which are the characteristic pore sizes. However, the method won't give any other quantitative information, nor will allow to see the porosity if the pores are of nanometer size. Other methods will be therefore required (porosimetry, adsorption, TEM, ...). Alain