- Sandipan Chowdhury added an answer:Is it possible to know the stoichiometry of two proteins interaction at physiological level?
I tried to know the stoichiometry of two proteins using size exclusion chromatography but i found both form aggregation and eluting in void volume, so could not be able to study. Now i am using whole cell lysate and run on size exclusion chromatography (Superdex 200HR 10/300 GL column) then collecting fractions of 100 ul and checking out them on western blotting using protein specific antibodies but not getting band on desired position according to my positive control.
Is there any way to calculate the stoichiometry of these proteins? please suggest me...
The answer to your question depends largely on 2 factors: (1) affinity of binding (2) how much of the individual proteins you are able to obtain (preferably purified protein). Some of the techniques available are as follows:
(1) Isothermal titration Calorimetry - for this you would need ~20uM of purified protein and the affinity of the proteins needs to be strong for the calorimeter to be able to measure the heat of binding accurately. However, complex stoichiometries (especially if the stoichiometry is at least partially conc. dependent can significantly contaminate results).
(2) Analytical ultracentrifugation - this is actually a pretty good technique if your protein pairs are capable of forming multiple stoichiometries - you will be able to obtain Kdiss of each stoichiometric combination. But you need significant amounts of purified protein for this.
(3) Glutaraldehyde cross-linking - cross-link your purified protein partner with glutaraldehyde (which is non-specific as it relies on exposed lysines) and run a gel (or do a western) to identify higher molecular weight bands. Compare this result with Blue-native PAGE (non-denaturing gels) analysis of uncrosslinked protein mix. While this might be the simplest/easiest thing to try - the results can be quite notorious because often several molecular weight bands will be seen - that said it is quite certainly the first step
(4) Mass-spec is certainly an option - but once again concentration dependent multiple stoichiometry will make results hard to interpret
(5) Dynamic light scattering - using scattering of light to measure molecular radii of different species which exists in solution and thereby relating it to molecular weight and size. Requires significant quantities of purified protein
(6) FRET - tag the two proteins with GFP/YFP - purifiy them and measure FRET. This will need small quantities of protein. But if there are multiple stoichiometries then interpreting FRET ratio could be tortuous (FRET signal will change with stoichiometry of association as well as distance between the FRET pairs). Also GFP/YFP might itself affect the stoichiometry of association, especially if the pair forms a moderate to weak affinity complex.
(7) SIMPUL - this is probably the best technique but it requires a TIRF microscope. Have the two proteins tagged with say Strep and Myc tags. Add fluorophore tethered primary Ab to the protein mix - lay the protein complex+Ab mix on a cover slip and perform single molecule photobleaching experiment. Very tiny amounts of protein will be required - starting sample need not be very pure (actually could simply be clarified lysed cells) - but instrumentation and software needed are not the most commonly available ones.
Hope this (along with other answers listed above) helps you think about what will be the best option for you.
- Richard Christison added an answer:Why would I not be getting recombinant protein from mammalian cells?
I have transfected CHO and HEK293 with constructs for 3 different proteins. I get resistant colonies (compare to mock transfected) which grow up after 3 weeks or so. The proteins should be being secreted but I cannot detect them in the supernatant by western blot or elisa (i have also checked cell lysates). The constructs have been checked and are all in frame with no mutations etc. Could it be that the proteins are aggregating/being degraded?
Checking the mRNA will tell you something, you should at least get a better idea of where to look for you problem.
Unless there is some compelling reason for production of a stable line it would be a good idea to at least look at the other expression systems as some systems suit some proteins better than others.
I am also a fan of checking a pool of transfected cells after a couple of days when setting up stable lines - it can save a lot of work catching a problem early.
- Wenke Weidemann added an answer:Any suggestions for myc protein westernblot?
There are two sepcific and strong bands when I use anti-myc(santa cruz 9E10) to analysis the whole cell lysates of transfected flag-myc 293t cell.But I could not detect any specific bands when I analysis the whole cell lyasates of HELA, HCT116,U87,MEF cell.The process of lysing is as below
1,wash the plates twice with cold PBS
2.add 200μl RIPA buffer into plates and scratched the cell into a tube
3.incubate the tube on ice for 20min
4.sonic 5s and break 2s for 12 times
5.centrifuge 13500 rpm for 15min,4℃
6. using supernants for 10% SDS-page immunoblot
Are there any problems?
does anybody konw how to successfuly detect endogenous myc protein?
Should I pay attention to some details specially?
Endogenous myc-levels may be to low to detect in whole cell lysate. Try to immunoprecipitate myc before analysing by western blot. I had the same problem with an other protein, I could detect the overexpressed and immunoprecipitated protein but not the endogenous protein. Good luck.Following
- Viktor Y Butnev added an answer:Most of protein is still stuck in the origin of resolving gel after transfer, how can I improve the resolution of the bands?
Stacking gel is 5% and resolving gel is 7.5% and my protein is 260kDa. I loaded 30ug protein in a volume of 50uL. I did a wet tank transfer 120V for 1 hour with cooling. I don't know why most of the protein is still stuck in the interface between stacking and resolving gel. Please help. I have attached a picture in ppt if it helps.
The proteins about 250K are often stuck between the stacking and resolution gels because they are bound to some other membrane (hydrophobic) proteins. I would suggest to try the commercial gradient gels with low concentrations of acrylamide. I would also recommend to use Laemmli SDS-sample buffer (2% SDS and 5% b-mercaptoethanol) for the extraction of the membrane-bound proteins from the cells. After that you will need to make a high speed centrifugation at least at 10,000 g (because a lot of insolubile proteins and DNA will remain in the pellet). Then, you will need to boil your sample for 3 min at 100*C and load it on your gel. Since not all of your protein will be extracted from the cell membrane as a monomer you might want to use a higher concentration of your 1st and 2nd antibodies for your western blots. Hope this might help.Following
- Emilia Manole added an answer:Can we co-incubate the primary and secondary antibodies at the same time for Western Blotting ?
Generally, we incubate the blocked membrane with the primary antibody, wash away the unbound primary antibody, then incubate with the secondary antibody which binds to the primary antibody, and detect the protein of interest on the membrane. Since the primary antibody binds its epitope with its variable domain, whereas; the secondary antibody binds with its constant domain, there should be no reason that mixing these two antibodies together will interfere with the binding. Can we incubate the blocked membrane with both primary and secondary antibodies at the same time for Western Blotting ? If it works, it will save time.
More of this, the time of incubation is different for the 1st and the 2nd antibodies. Sometimes it is better to incubate the membrane with the 1st antibody over night at 4 dgrs for a proper result. If you put the secondary antibody a lot of time with the membrane, or more concentrated, it would be possible to bind unspecific and to obtain many unspecific bands or background. And it is right that the TBST washes between the antibodies have a great importance in obtaining a good and clear result of WB. So the protocol was established very well and for certain reasons in the way to put the 1st and the 2nd antibodies separately.Following
- Liu Jiyun added an answer:Do you have any advice on my protein 1st Dimension Run Problem?
There is problem with the running of 1st dimension of proteins. The sample is isolated from leaf and midrib of banana plant. We have optimized the protocol and getting good results but there is problem with the running of 1st dimension of leaf now. It does not run properly. Usually, 1st dimension run from negative to positive, in these cases it start running from negative to positive but after 1:30 hour, it also starts to run from positive to negative side as well. This problem persist until the run is over and we got the strips in this form(picture attached). Firstly i thought it might be some handling problem or with the samples, so I changes the sample and run with the midrib replicate. Problem persists. Now, i do not know what is the problem with them. New Rehydration buffer and 1M DTT stock were prepared but issue was not solved. Room temperature was 22C.
First I thought that it might be due the improper washing of the focusing tray, but we cleaned it well and still the problem persist. Can this be due to the Protean IEF Cell Bio Rad? It got some problem and now running the strip in this manner?
Hope to hear positive.
I agree with Manuel Sebastián- The phenolic extraction method is more suitable for the banana plant protein extration compared with other methods as it can clear polysacharides effectively. The detailed protocol can be seen in the article: http://www.nature.com/nprot/journal/v1/n2/abs/nprot.2006.102.htmlFollowing
- Wolfgang Schechinger added an answer:What could have gone wrong with my Western Blot?
my Western Blot looks like this (see attachment).
The samples loaded onto the gel are cell lysates, I blotted for 4 hrs at 4°C and 300mA (transfer buffer: Tris Glycine with 20% MetOH), which I've done before and so far it has always worked fine.
Does anyone have an idea what might have happened?
Elizabeth, have you prepared all the samples the same way, i.e. are they comparable? Looks to me there was problem with the gel rather than with the blot - different salt concentrations in your samples on the left and on the right (where you suspect bad transfer)?Following
- Fernanda R C Giachini added an answer:How to store a membrane in Western Blot?I am a beginner in western blot.
Sometimes I need to store the PVDF membrane for later re-probing.
I have asked my colleagues, some said I should dry the membrane and store it in 4 degree
but I was told by others that the membrane should not be dried in any process,
some said the proteins may degrade, some said it will result in higher background signals.
So most of my colleagues store the membrane in TBST in 4 degree.
But when I search in the internet, I found that some people did dry the membrane in the storage process.
There are a few questions I want to know:
1. The rationale of drying the membrane in storage,
2. The consequence of drying the membrane, why the membrane should be kept wet?
3. How long can a membrane be kept, without affecting the result?
4. Which method can store the membrane for a longer time?
Does dry-air storge work for nitrocellulose membranes?Following
- Kyohei Miyazaki added an answer:Does anybody know a good antibody to claudin-5 for western blot?
Hi, I use HUVEC for tight junction research. I struggled to get bands of claudin-5 for westernblott(WB) using some antibodies. I could obtained good results from immunofluorescent stain using same antibodies. Anti claudin-5 antibodies I tried are rabbit anti claudin-5 polyclonal antibody (IBL, Takasaki, Japan), mouse anti-claudin-5 monoclonal antibody (invitrogen, catlog No. 35-2500) , and mouse anti-claudin-5 monoclonal antibody (Santa Cruz, sc-374221) . WB protocol is followed; blocked by 5% or 10% non fat dry milk / 0.1% Tween20 / TBS at room temperature for 1 hour, followed by incubated with 1:500 diluted primaly antibody in 1% or 5% non fat dry milk / 0.1% Tween20/ PBS at 4℃ overnight, and HRP-conjugated anti mouse or anti rabbit IgG as secondaly antibody diluted 1:10000 in 1% or 5% non fat dry milk / 0.1% Tween20/ PBS at room temperature for 1 hour. I could not get significant bands of claudin-5 at 23kDa. Protein applied to SDS-PAGE was about 30 ug/well. Does anyone let me know good anti claudin-5 antibody for WB? Thank you.
Dear Attila Lehotzky
Thank you for your suggestion. claudin-5 is expressed in HUVEC, but very low as you pointed out. Further more, antibodies I used had many non-specific bands, and these bands signals were stlonger than that of claudin-5, so the band signal of claudin-5 was hard to detect. I'll modified with secondary Ab dilution and incubation time.Following
- Trang Mai added an answer:Can you show the picture of your worst Western blot, and explain the reasons for this disaster please?I start this topic in order to collect the gallery of the photos of Western-blots (WB) as ugly as possible. The detailed description of the problem and the technical solutions were applied to resolve it are strongly suggested, however ugly WBs without the clue what is wrong are welcome to discuss it here. The overall idea of this post is to help the young researchers to resolve the problem with simple and cheap tricks. On the photo below you can see the lightning in the middle, dust in the upper left corner, small air bubble in ECL solution in the upper right corner. The background is not fully grey, means ECL was not properly distributed, only band visible is not specific binding of the antibody to the slightly degraded marker band (right).
Sometimes I used the 12% acrylamide SDS gel but it couldn't separate my proteins below 28 kda. All the proteins below 28 kda (including the ladder, the lower red one is 28 kda) were in the same line with the dye. However when I prepared the gel several days before and stored it in the complete running buffer 4°C, the gel worked fine. It could be the pH problem? Both the gel and the buffer contained 0.1% SDS. Thanks for your comments !!Following
- Vinay Saunders added an answer:Standardizing supernatant?I'm collecting supernatant as samples and measuring certain proteins released by cells/tissues after treatment. I would appreciate suggestions on how to standardize supernatant in running Westerns and ELISA. I am aware that running these assays using LYSATES we use total protein content measured by BCA assay or other protein assays. But what about if you are using supernatants where we don't expect intracellular proteins to be present? What should be used as a measure of uniformity in loading the wells?
I realise this topic is quite old now, but I'm interested in the same question.
Ryan, can i ask you what solution you came up with?
I also have a question; a few people have suggested doing ELISAs, but doesn't that also require normalisation to some sort of standard to account for potential differences in the amount of tissue in each well?Following
- Madhur Agrawal added an answer:Why was Sirt1 detected at 75 kDa but not 110 kDa?
Hi, I'm studying Sirt1 on mice muscle. The antibody has not a specific epytope to recognize, so it should detect the band at 110 kDa. The problem is that I have only a single band at 75 kDa in wild type and mutagenized mice. I know that the 75 kDa is an inactive fragment, but I expect to detect the active form in wild type. Can someone help me?
I would suggest you to contact Abcam once and in the mean while, try cell signalling antibody, it works well for me for 110 KD band.Following
- Bulut Hamali added an answer:Does anyone have any idea why I only have low weight size in western blot?
I have been trying this for more than 2 months, but it is always the same result. I am doing Fasciola hepatica whole cell lysate like below:
Adult parasites were homogenized in 10 mM Tris–HCl, pH
7.2 containing 150 mM NaCl, 0.5% Triton-X100, 1 mM
EDTA, 1 mM PMSF and 1 tablet complete Lysis protease inhibitor. To remove cellular debris, thehomogenates were solubilized for 30 min at 37C, followed
by centrifugation at 12,000g for 15 min at 4C.
When I do Ponceau S staining I do not see any higher bands than 40kDa. I load about 15-20 ug per well, but it did not improve until now.
And Thanks a lot Wolf. I actually did always semi dry transfer but I will think about to try wet blot as well. Thanks a lot for suggestion.Following
- Wu Anguo added an answer:What is the best percentage of gel for a 14 kDa protein using western blot and the best voltage for transferring the protein from gel to membrane?Running a western blot gel using a 14 kDa protein.
12% gel, I usually use 12% gel to analyse 14-16 kDa protein such as LC3Following
- Stephan P Tenbaum added an answer:DNA dot blotting and Licor Odyssey infrared detectionantibody, detected using the Li-cor Odyssey infrared system. We have used the instrument previously only
Quantify DNA and put equal amounts in 20-50 ul H2O or TE. (for tiny amounts you may choose Qubit quantification.)
Dot/Slot blot straight to the NYLON membrane (Amersham Hybond N+, GE Gealthcare) – I use a vacuum blot (Biorad). Do not heat the sample before loading. (If you boil you may get DNA denaturation resulting in unknown amount of ssDNA stretches, since I use dsDNA antibody as loading control heating would potentially alter the result.
I tried UV crosslinking, of the membrane and baking worked better. I boiled samples before blotting and got worse signals. I blotted with SCC-based buffers and they worked worse in my hands then straight blotting in water.
Fix by baking at 80ºC for 2h
Block directly with 5% milk in TBS-Tween for 2h
In the following I combine HRP/ECL detection in combination with fluorescent secondary antibodies so I mix mouse dsDNA antibody and rabbit 5hmC primary antibodies for incubation (o/n 4ºC). So I get the loading ctrl of the same spot.
The same way, I incubate together a mix of secondary antibodies (anti-rabbit-HRP (1:5000/1:10000) and anti-mouse-Alexa flour 680 (1:5000) for 1-2h. Then, I first (!!!) do fluorescent detection in a Licor Odyssey or camera-based system to detect dsDNA signal strait with the washed wet membrane and then I incubate the blot with standard ECL. (The fluorescent signal is easily quantified (linear signal) – ECL is more sensitive as signal is accumulative on the x-ray film and may be exposed longer at will. ECL solutions may screw up fluorescent secondary signal detection if you do the other way round.
I use a mouse anti dsDNA antibody (ABCAM HYB331-01, ab27156) as loading control (1:10000) and 5hmC antibody (1:1000) Active Motive. Cat. Nº 39769. I also tried a mouse Methyl-cytosine antibody once and it worked fine.
I hope this helps, good luck!
My very best,
- Vanessa Mendes added an answer:What are the causes of a bad Western blot result?
I did the Ponceau on the last run, and it came out looking like these two images, attached.
What could cause this, besides bad gel?
I'm having the same problem. How did you solve it? Today I tried more sonicating and DNAse I, but it didn't seem to improve.
- Fernanda Mügge added an answer:Does anybody know of ATF6 (Activating transcription factor 6) antibodies that have worked in INS-1 cells for western and immunostaining?
I am planning to look at the expression of ATF6 in INS-1 cells under high glucose or ER stress. There are number of antibodies out there but I want to know if anyone in researchgate has personally used any of these and has worked without much trouble for western and immunostaining. Thanks.
were any of you successful?
I work with MEFs and use a SCBT antibody. For Western Blot it is VERY difficult to get a good result for ATF6. I've tested at least 4 extraction protocols and the last one, which leads to a very concentrated cell extract is the best so far, but I get a LOT of innespecific bands;
Today I am using this same Ab for immunofluorescence and don't know if it will work...Following
- Narendra Singh added an answer:What is the best protocol to make ECL (western blotting) mannualy at lab?
cancer biology researchers, those do western blotting frequently.
Thanks dear Wassim.Following
- Amy Schutz Geschwender added an answer:Does anybody have experience with blocking reagents compatible for the LI-COR Odyssey?I am using the LI-COR Odyssey system for Western Blot detection. I have high background levels
Yes, every lot of PVDF membrane from LI-COR is QC-tested for low background fluorescence.Following
- Denis Dermadi Bebek added an answer:Are the protein samples extracted for 2-D gel using urea and CHAPS buffer valid for direct 1D western blotting?
I need to confirm some results of 2D immunoblotting by carrying out the western blot (1 D) using same samples that are prepared for 2D using rehydration buffer contains 8M urea, 4% CAPS, 40 mM trisCl 6.8 and DTT. as i know that boiling urea will cause carbamylation. i wonder whether i can use the sample directly in my WB without boiling.
when i perform the 2 D gel of my proteins in the rehydration samples the second dimension works perfectly so i assume loading the samples directly will also work.
is the equilibration step after IEF contribute to the resolution of the 2nd dimension?
incubation at room temperature with SDS and b-mercaptoethanol for 15-20 min helps a lot. I run my samples that were extracted in urea.Following
- Norbert Kartner added an answer:Best way to resuspend Acetone-precipitated protein for Western Blot?I'm using QIAGEN kit to extract RNA and to better use these samples, I decided to extract protein as well, which QIAGEN recommends to do so by adding acetone to the flow through.
Judging by the size of the pellet I've been able to collect great amounts of protein, however, when I try to resuspended in RIPA buffer or PBS alone, the pellet barely dissolves.
Does anyone have a suggestion in how to resuspend the pellet or what buffer to use?
Try PRMM method, doi: 10.1128/AEM.70.1.610-612.2004
Haven't done an acetone precip. in over a decade, but I seem to recall that barely-dried pellets dissolve in a minimal amount of just plain distilled water. Use a flame-sealed Pasteur pipet as a stirrer to suspend/dissolve the pellet. Any ionic strength changes solution time from minutes to hours. You can add buffers etc. after dissolution. BTW, if you use urea, do NOT heat your sample above 37 deg. Urea and heat will transcarbamylate your protein (particularly messy for 2D gels). Methanol precipitation has to be cold, not room temp. if you want anything approaching quantitative recovery for dilute mixed proteins.Following
- Amit Koul added an answer:How should I perform anti alpha-synuclein western blots?
I am working with PC12 cells and. My problem is that when I perform anti alpha-synuclein Western Blots, the signals of this protein are never consistent with each other, even when I run duplicates of each sample. Is it because the protein is aggregated?In this case, what should I do?Should I sonicate my samples?Or make the lysates in a special buffer?
Well i think difference in signal mostly comes down to your skills of loading protein on the gel. In your duplicates, are you sure you are loading same amount of protein on the gel? If you are not, that could give you two different signals .Following
- Amelia Trimarco added an answer:Protein present but not being expressed. Any ideas why?
I've transfected HEk293, HEk293T, Cos-7 cells with 2 different plasmids. By PCR I can confirm that the DNA is there but by Western Blot there is no overexpression of the proteins. Any ideas why this is happening??
Did you check if your protein can be secreted?...We had the same problem and in the end secretion was so quick that we found it in the medium and not within cells!!!Following
- Nicolas Tardif added an answer:Does anyone have experience using infrared secondary antibodies for western? What protocols work best for you?
I am trying to detect a purified bacterial his-tagged protein on western blot (using nitrocellulose membrane). I did see the protein in elution fractions on SDS gel using coomassie stain. Primary used to detect is a rabbit anti-his, and my secondary is anti rabbit-680 conjugate. I blocked with 5% milk, incubated with primary o/n at 4 in 5% milk, and also placed the secondary in 5% milk for 45min at RT (I was told by some protein loving friends that milk can also help improve secondary antibody background). I have not used these fluorescent antibodies before. Called the company and am waiting to hear back, however in short, it might be that I should tailor my staining protocol to something closer to an IF, so use serums for blocking and incubations instead of milk. Also an option to just use TBST for antibody incubations. Any help/thoughts is much appreciated!
It's probably a bit late to answer, but when I use the IRdye for western there is few tips to avoid background and usually they work nicely.
1) choose a low fluorescent membrane, I am suing immobilon-FL
2)for the blocking I prefer to use the odyssey buffer
3)most important, when you use the secondary 680LT from licor, you have to add 0.01% SDS and 0.1% tween-20, if you don't you will have just background. If you use the 800CW you don't have this problem.
- Laurie Verzeaux added an answer:What are these white spots on my Ponceau-stained Western Blot?
We ran 20 ug protein in each lane (mouse kidney cortex). I transferred at 100V for 3h with the transfer box in the fridge with ice packs around it. I'm positive the buffer was the right transfer buffer we use. I've done Westerns many times and usually they come out fine but sometimes they have these big empty spots. I always roll out the bubbles as I make the transfer sandwich and I rinse the gels to get the excess SDS transfer buffer off so I just really don't know why this happens. Does anyone have any idea if it could be a problem with the transfer apparatus? Thanks!
Hi, I've had this problem due to the presence of salts (from transfer buffer of the last transfer) into sponges used to make the sandwiches. Rince them several times in water before each use. Hope that will help you.Following
- Junhee Choi added an answer:Western blot bands blur and become faint. what should I do?
My western blot bands blur and become faint.
Two different independent experiment show similar phenomena at the left side (maybe protein marker side).
Please give me advice.
Maria Vicenta Camarasa
Laurence Stuart Hall
Thank you all!!!!
If i get to solve the problem, I will comment hereFollowing
- Madhurima Saha added an answer:No ponceau stain despite successful western. What's wrong?
I am doing westerns with human brain tissue and the westerns seem to be working fine. I'm getting a nice band of the right weight, but nothing shows up when I ponceau stain.
But here's the thing: I am using revived fixed tissue. Frozen tissue from the same case stains with ponceau.
Any thoughts? Is it okay that it blots just fine but doesn't ponceau?Following
- Swapnil Shinde added an answer:Did anyone here ever did a successful Western blot for either Usp9x, USP7 or HUWE1 ?
I do semi-dry on PVDF, block with 4% milk and do the AB 1:1000 oN but all I get is background. Any help is appreciated!
I do semi dry transfer on PVDF but i use 5% milk for blocking.
To reduce the back ground I would suggest you to give more washes after primery incubation as well as after secondary antibody.
Try to change the primery Ab dilution.Following
- Manchala Nageswar Reddy added an answer:Why do I have a problem running the SDS gel?I have used 10% resolving and 5% stacking gel with exact amounts for the preparation. I believe there is no error in it. I lysed Caski cells using RIPA buffer and loaded them in the wells. I reused the running buffer I made last time.
The gel runs very weirdly. Is it because of the buffer? Or is there some mistake in the gel casting?
The composition of lysed Caski cells using RIPA buffer may matters.Please check the pH of the lysate which may interfere in the protein migration while running in the gel.
all the bestFollowing
- Ru-Jeng Teng added an answer:Has anyone detected enos(nos3) in huvec by western blot ? I need some useful suggestions?
I detect the protein expression of enos(nos3) in huvec and cannot get results with enos.The expression of other proteins are strong enough to detect .The only one cannot be detect is enos .
I extracted the total protein of HUVEC. Also, the final concentration of total protein is about 5mg/ml.
So ,I need anyone who detected enos in huvec by western blot to help me .
Thank you for your attention .
We had similar probelm occasionally such as strong signal with phospho-eNOS but no signal for eNOS or IP with eNOS showed associated proteins but no eNOS signal. We still can not figure out the reason. Will suggest you to try more than one eNOS antibodies.Following
About Western Blot
Western blot is a widely accepted analytical technique used to detect specific proteins in the given sample of tissue homogenate or extract. It uses gel electrophoresis to separate native proteins by 3-D structure or denatured proteins by the length of the polypeptide. The proteins are then transferred to a membrane (typically nitrocellulose or PVDF), where they are stained with antibodies specific to the target protein.