A modification of the Lowry procedure to simplify protein determination in membrane and lipoprotein samples

doi:10.1016/0003-2697(78)90586-9

Analytical Biochemistry

Volume 87, Issue 1, 15 June 1978, Pages 206-210

https://doi.org/10.1016/0003-2697(78)90586-9 Get rights and content

Abstract

The original Lowry method of protein determination has been modified by the addition of sodium dodecyl sulfate in the alkali reagent and an increase in the amount of copper tartrate reagent. These alterations allowed the method to be used with membrane and lipoprotein preparations without prior solubilization or lipid extraction and with samples containing 200 mm sucrose or 2.5 mm EDTA.

References (9)

O.H. Lowry et al.
J. Biol. Chem
(1951)
J. Eichberg et al.
Anal. Biochem
(1969)
H. Schuel et al.
Anal. Biochem
(1967)
T.H. Ji
Anal. Biochem
(1973)

There are more references available in the full text version of this article.

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^☆: This research was supported by National Institutes of Health Grant HD06441 and a Public Health Service Research Fellowship (1 F22 HL00259-01) from the Heart and Lung Institute to M.A.K.M. This is Journal Article No. 8147 from the Michigan Agricultural Experiment Station.

²: Present Address: Department of Bacteriology and Molecular Biology Institute, University of California, Los Angeles, Calif. 90024.

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A modification of the Lowry procedure to simplify protein determination in membrane and lipoprotein samples☆

Abstract

J. Biol. Chem

Anal. Biochem

Anal. Biochem

Anal. Biochem