MOLECULAR WEIGHT OF BOVINE PLASMA ALBUMIN, VITELLENIN, AND THEIR OXIDATION PRODUCTS IN FORMIC ACID

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Abstract
Sedimentation, diffusion, and Archibald transient state measurements were made on bovine plasma albumin and vitellenin of egg yolk in formic acid (88% w/w) solution. The molecular weight of bovine plasma albumin, averaging 77 × 103and 70 × 103with and without added salt, respectively, indicated that peptide bonds were stable to the acid for at least 1 week (storage at 5 °C and measurement periods at 20 °C). Similar values were obtained from estimates based on viscosity measurements but greater deviations occurred. Vitellenin had a mean molecular weight of 93 × 103from sedimentation and diffusion but polydispersity was revealed by the Archibald measurements (molecular weights from 55 × 103to 10 × 103). Higher values of molecular weight were obtained for vitellenin by varying the dissolution technique and exposure time in formic acid and also when viscosity measurements were used to compute molecular weight. Analyses of N-terminal amino acids showed that peptide bond rupture was not a major factor in the polydispersity of vitellenin. Although aggregates are probably present in formic acid solutions of this protein, it appears to be naturally polydisperse. Both albumin and vitellenin were considerably degraded by performic acid oxidation procedures.