I performed a WB using plasma rats and monkeys samples with anti ubiquitin K-48 antibody. In every sample the antibody binds something and it appears a specific band that seems to be 71kDa. When I used anti-ubiquitin unspecific antibody(just to see if I get the same results) same bands appears. It cannot be ubiquitination because the molecular weight. How can I explain the both antibodies bind something that I dont know?


  • $\begingroup$ I can not see the reason why you deny ubiquitination. In addition, Ubiquitin K-48 ligated products can be recognized by anti-ubiquitin antibody. But, usually you could get multiple bands from cells and as a result, a whole lane is stained and smeary. $\endgroup$ – 243 Sep 25 '15 at 21:41
  • $\begingroup$ thanks for your answer. I see it strange because I am using several plasma samples of different animals, and it appears exaclty the same in all of them with the same molecular weight. So I dont know what is it. Because if there is poly-ub as you say it should appears smears, but no a clear band of specific molecular weight in all the animals right? I am a litle confuse. $\endgroup$ – Bio Sep 25 '15 at 21:56
  • $\begingroup$ Plasma contains cells but also lots of extracellular proteins such as albumin, immunoglobulin, etc., right? So, signals from cells can be very weak. $\endgroup$ – 243 Sep 25 '15 at 22:05
  • $\begingroup$ Yes but Im using as a control cells which I know they accumulated poly-ub K48, so the control looks as smear, however, plasma cells it does not look like that, it looks as a clear band of specific molecular weight that it does not correspond with the weight of the ubiquitin but is not a smear either. I am still confuse :/ $\endgroup$ – Bio Sep 25 '15 at 22:22

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