rbrgouda

Hi Charon, Thanks for the reply. Your information helped me to understand more about my proteins. As you said, it should be the property of the protein itself. Both the protein show deviation less than 5 kDa. I did MS to confirm the presence of both the proteins. I didn't try to estimate the mass of the full size protein, instead I was looking for the presence of these protein peptides after trypsin digestion. If it is possible in MS I will estimate the mass of the full length protein. Thanks Rbrgouda

Hi Charon, a) I use SDS-PAGE low range molecular weight standards (Bio-Rad) b) They are not prelabeled c) Proteins are not membrane proteins, they are helicase and single stranded DNA binding (SSB) proteins.

Hi, I have expressed several recombinant proteins in E.coli. But, I never encountered a strange problem like this before. Currently two of the proteins I'm trying to express in E.coli are running about 4-5 kDa bigger than expected size. If it had happened with only one protein then I would assume that particular protein property makes it run it little higher. At this point of time I'm thinking of changing the protein sample buffer containing higher percent b-ME and SDS. Please help me to overcome this problem. Rbrgouda:confused: