RE: BSA Molecular Weight

From: Len Packman (lcp2@mole.bio.cam.ac.uk)
Date: Tue Mar 06 2001 - 09:48:33 EST

This topic was discussed in 1995. Below are the summarised replies from then

Len

  Using ionspray MS we have determined the MW of Sigma BSA as 66429.05. After
reduction and alkylation with 4-vinyl pyridine, the MW determined was
70,150.55, corresponding to the addition of 35.4 pyridylethyl groups. Using
the sequence shown below, the predicted MW for 34 disulfide linked cyteines and
one reduced is 66429.96 and after alkylation with vinylpyridine 70144.1.

DTHKSE IAHRFKDLGE EHFKGLVLIA

FSQYLQQCPF DEHVKLVNEL TEFAKTCVAD ESHAGCEKSL HTLFGDELCK

VASLRETYGD MADCCEKQEP ERNECFLSHK DDSPDLPKLK PDPNTLCDEF

KADEKKFWGK YLYEIARRHP YFYAPELLYY ANKYNGVFQE CCQAEDKGAC

LLPKIETMRE KVLTSSARQR LRCASIQKFG ERALKAWSVA RLSQKFPKAE

FVEVTKLVTD LTKVHKECCH GDLLECADDR ADLAKYICDN QDTISSKLKE

CCDKPLLEKS HCIAEVEKDA IPEDLPPLTA DFAEDKDVCK NYQEAKDAFL

GSFLYEYSRR HPEYAVSVLL RLAKEYEATL EECCAKDDPH ACYTSVFDKL

KHLVDEPQNL IKQNCDQFEK LGEYGFQNAL IVRYTRKVPQ VSTPTLVEVS

RSLGKVGTRC CTKPESERMP CTEDYLSLIL NRLCVLHEKT PVSEKVTKCC

TESLVNRRPC FSALTPDETY VPKAFDEKLF TFHADICTLP DTEKQIKKQT

ALVELLKHKP KATEEQLKTV MENFVAFVDK CCAADDKEAC FAVEGPKLVV

STQTALA

      Hope this helps

      Roland Annan
      Research Mass Spectrometry
      SmithKline Beecham

__________________________
There are papers that reported the masses of BSA measured by ESI
mass spectrometry. Feng et al (J. AM. Soc. Mass Spectrom.1991, 2, 387-401)
reported that the MW of BSA was found to be 66431.5 +/- 1.3 Da, ~164 Da
higher than the old caculated sequence MW, but is very close to the
revised sequence MW 66430.3 (Hirayama et al, 1990) (see the paper for
details). Since the disulfide bonds remain intact under normal ESI conditions
the measured mass should reflect the disulfide bond content, and you don't
need to subtract any mass to match the calculated sequence MW that should
have already been corrected for the disulfide bond content. Based on the
report of Feng et al, the calculated sequence MW of 66430.3 Da of BSA has
a

lready included the mass reduction effect due to the disulfide bonds.

Xuejun Tang Ph.D.
Dept. of Biochemistry
Albert Einstein College of medicine
1300 Morris Park Ave.
Bronx, NY 10461
Phone 718-430-3479
FAX 718-823-5877

________________________________________________________
MS -speck; the comment to the BSA mol.mass.

I hope, the reference:

Rong Feng, Yasuo Konishi, and Alexander W.Bell

High Molecular Weight Determination and Variation Characterization of
Proteins Up To 80 ku by Ionspray Mass-spectrometry.

J. Am. Mass. Spectrom. 1991, 2, 387-401.

will help: "The MW of bovine serum Albumine (BSA) was found to be 66,431.5 +/-
1.3 u, ~ 164 u higher than the calculated sequence MW, most probably because
of incorrectness in the previously reported BSA amino acid sequence" (cited
from the abstract, p. 387).

Sincerely, Viacheslav N. Medvedkin
_________________________________________________________ 

-- 
*********************************************************************
Dr Len C. Packman
Assistant Director of Research
Department of Biochemistry
University of Cambridge
80 Tennis Court Road
Cambridge, CB2 1GA, UK

Tel: +44 (1223) 333639   FAX: +44 (1223) 766002
e-mail: l.c.packman@bioc.cam.ac.uk

Protein and Nucleic Acid Chemistry Facility 
http://www.bio.cam.ac.uk/proj/adr/PNAC/pnac.html

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