We usually suggest customers using PVDF membranes rather than nitrocellulose membranes, because PVDF membranes offer better protein retention, physical strength and broad chemical compatibility. The typical binding capacity of commercially available PVDF membranes is 100-200 μg/cm2, compared to that of nitrocelllulose membranes having a binding capacity of 80-100 μg/cm2. However, if the detection requires that the transferred protein retains its native conformation after transfer, for instance, when the antibody recognizes 3-D structure (e.g. an antigenic epitope consisting of non-contiguous residues), nitrocellulose membranes might be preferred.

The concentration of antigen may be too low. If the relative concentration of the antigen of interest is too low (less than 0.2 % of total protein), it may be difficult to detect. If this happens please load more sample, or enrich the antigen by fractionation or by immunoprecipitation.

There are many factors that are responsible for additional bands appearing in western blot results:
a) Mechanical degradation of the lysate: If samples are stored for a prolonged period or if proteins or membranes are fractionated after homogenization of the starting tissue, additional bands which are faster migrating than the targeted one may appear. To get around this use fresh lysate.
b) Proteolytic degradation of the lysate: Proteolysis is a common cause of the appearance of background bands. Make sure there are sufficient protease inhibitors in the sample.
c) Too much protein sample was loaded
d) The detection system used was too sensitive
e) The western blot membrane was not blocked correctly.
f) Homologous proteins or other isoforms of the target protein: Around one third of proteins belong to protein families, containing homologous proteins which may cross-react with antibodies. Furthermore, one single gene can be translated into isoforms with different molecular weights. Antibodies usually can detect more than one of them. 
g) Unspecificity of the antibody: Although Proteintech applies the most stringent quality assurance standards to ensure that our antibodies do not bind multiple targets; it is possible that the antibody binds some unrelated proteins, especially on those lysates which we did not test.

Please keep in mind that the predicted molecular weight is calculated from the protein sequence. There are several possibilities which may explain this observation:
a) Degradation of the lysate: The sample may have been degraded by proteolysis; explaining why it will show a band with a different molecular weight than the one predicted from the sequence.
b) Protein modification: Some proteins, such as membrane proteins, are commonly modified (e.g. glycosylation) after translation. This may result in the protein having a different molecular weight to that predicted from the primary protein sequence.

Yes, we can offer you a negative tissue control.

We would be pleased to investigate this for you. Please contact us for more detailed information.

This is hard to predict with accuracy but will depend upon the extent of protein sequence similarity between the immunogen and the potential cross-reactive protein sequence. A pair-wise sequence alignment can be performed online through NCBI-BLAST website (Link to http://blast.ncbi.nlm.nih.gov/Blast.cgi).

You can find the detailed information for each antibody on their product datasheet. Please search and click the antibody of your interest; you will be directed to the datasheet for your antibody which includes validated applications, images, etc. You could also print the datasheet.

Please store the antibody in the original tube at -20°C and do not aliquot. Our antibodies are stored in 50% glycerol which prevents them from freezing.

Our antibodies will remain functional for a minimum 2 years when properly stored.