Why do I see a doublet when using the Bcl-xL (54H6) Rabbit mAb #2764 for western blot?

The Bcl-xL (54H6) Rabbit mAb #2764 recognizes a portion of the human Bcl-xL sequence which is retained in all three isoforms of Bcl-xL. Please see UniProt for the precise isoform sequences:

https://www.uniprot.org/uniprot/Q07817#sequences

The doublet is most likely Bcl-xL and Bcl-xB, as Bcl-xS has a lower predicted molecular weight (19 kDa versus 25-26 kDa).
 

Last updated: March 31, 2026