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I would like clarification on the predicted band size. I have read the following: "Question: don't these two statements from the datasheet contradict each other: 1. This antibody detects a band at 130kDa corresponding to Rad 21 and also a band of unknown origin at 75kDa. 2. WB: 1/500 - 1/5000. Predicted molecular weight: 72 kDa. unless 75kda is the unprocessed precursor and the protein is phosphorylated? thank you. Answer Thank you for your enquiry. I have been in contact with the originator of this product, and the band at 130 kDa is the Rad 21 band, and the band at 75 is unknown. I do not know exactly why Rad21 runs a larger band than is predicted. I hope this information helps, please do not hesitate to contact us if you need any more advice or information." On the datasheet it is implied 75kDa is the predicted weight. Does the datasheet need updating to 130kDa? Can you clarify the expected band size?When I run WB I get strong band at 130kDa.
Asked on Mar 21 2013
Based on Swiss-prot, the predicted molecular weight for this protein is indeed 75 kDa as mentioned on our datasheet. However, a band at ˜120-130 kDa has been previously observed: Mol Cell Biol. 2002 Dec;22(23):8267-77 PMID: 12417729. The higher molecular weight band seen is also consistent with the banding pattern observed for other commercially available antibodies to Rad21.
Some suggestions for the presence of these two bands is that the molecular weight of rad21 is ˜75kDa and the molecular weight of phosphorylated rad 21 is ˜120 kDa. Other data suggests that ab992 recognises endogenous Rad21 at 130 kDa in HeLa cell lysates consistent with the findings by Hoque and Ishikawa JBC, 276, 5059-5067, 2001 and that the prominent band seen at 75 kDa has not been characterised but is presumed to be a fragment of Rad21.
I am sorry that I do not have a more definitive answer for your but it would seem that the exact identity of these the bands has still not been confirmed.
With regards to the above Question and Answer published on our website, I have removed this as it was confusing and incorrect so thank you for bringing this to our attention.
Answered on Mar 21 2013