Determination of Low Concentrations of Protein by the Biuret ‘Method Using the “Stopped-flow Time Difference Analysis” Technique

Abstract

The “stopped-flow time difference analysis” technique (a novel and sensitive technique, involving a sort of end-point assay using the stopped-flow method) was applied to the modified biuret method (micro-biuret method) for protein determination. Protein concentration was easily determined from a reaction curve recorded for only 2 sec. The calibration curve for bovine serum albumin was linear from zero to 1000/µg/ml. The detection limit for bovine serum albumin was 4 /µg/ml and is comparable to that of the widely used Lowry method. The important advantage of the present method, compared with the conventional spectrophotometric methods, is that it was much less affected by the variation of protein species, and was almost free from interference by coexisting materials, including widely used tris(hydroxymethyl)aminomethane and peptides. The method is thus useful for a sensitive and accurate determination of either an unknown individual protein or total proteins in an aqueous solution. © 1987, Japan Society for Bioscience, Biotechnology, and Agrochemistry. All rights reserved.