Chromogenic groupings in the Lowry protein determination

Abstract

showed that a complex reagent containing molybdate, tungstate and phosphoric acid would react with proteins to yield a blue colour approximately proportional to the tyrosine and tryptophan content. Pressman (1943) defined some of the variables influencing colour yield. Herriott (1941) discovered that pretreatment with cupric ion greatly intensified the blue colour given by proteins and peptides, but had no effect upon the colour .yield from tyrosine. Lowry, Rosebrough, Farr & Randall (1951) further refined and systematized these observations into a practical method of protein assay which, because of its

A Purified Serum Glycopeptide from Controls and Cystic Fibrosis Patients. I. Comparison of their Mucociliary Activity on Rabbit Tracheal Explants

“…The absence of aromatic amino acids was further documented by the discrepancy between the protein concentration as calculated from the UV absorbancy (21) and that determined by the Lowry et al method (20). The chromogenic product of the Lowry procedure is influenced by the presence of aromatic amino acids, amino acid sequence and peptide bonds, whereas the UV difference between 225 nm and 215 nm is not affected by the presence of aromatic amino acids (13,21). The purified glycopeptide from both CF and controls was positive with orcinol staining and negative with resorcinol staining.…”

Studies on the sub-units of triose phosphate isomerase

“…The two minor components were both present in the control experiment lacking guanidine and cyanate. (Chou & Goldstein, 1960) and the failure to detect free amino acids is not important in the present context. The reaction was carried out as described by Bailey (1967), except that solution A contained N-sodium hydroxide (rather than 0-1 N-sodium hydroxide), to neutralize the buffer in the sample.…”

Nonheme Iron Electron-Transfer Proteins

“…The conditions for reconstitution differ in this respect from those for other known apometalloenzymes, such as the apoprotein of carboxypeptidase that is converted to holoenzyme by the addition of a metal alone (25). The thio:[ requirement appears to be associated with the regeneration of the protein sulfhydryl groups from the derivative formed by the addition of the mercuria| since apoproteins prepared under conditions in which sulfhydryl groups were not protected could not be reconverted to the native material and contained all their sulfhydryl groups in the form of disulfides (63).…”

“…The high color-value for ferredoxin, as compar,~.d with bovine serum albumin, is striking since ferredoxin contains only one or two aromatic amino acid residues and would be expected to give a lower than normal color-value. However, this enhanced color yield may result from the particular amino acid sequence in the protein and the relatively large number of glutamate residues (25).…”