A simple electrolytic method of labeling human fibrinogen, immune gamma globulin and serum albumin with 99mTc-pertechnetate at pH 7.4

An improved electrolytic labeling technique has been developed for tagging human plasma proteins at physiologic pH condition. The basic principle involves the addition of protein after electrolysis and pH adjustment, thus avoiding harsh treatment of the protein and preserving its biological properties. High binding efficiency has been obtained for human fibrinogen, immune gamma globulin and serum albumin with an average of 77%, 86% and 87% respectively as assayed by paper radiochromatography. The labeling mechanism is not known. Data from protein electrophoresis demonstrate the existance of chemically active 99mTc-complex species with high protein binding capacity. The entire labeling process requires less than 1 hour. Since plasma proteins are labeled at pH 7.4, the problem of protein denaturation has been significantly reduced.