Tautomerization, autoxidation and bond-exchange reactions of 2-mercaptopyridine derivatives were investigated in solution, by using several kinds of solvents. A 2-mercaptopyridine derivative having an N-benzylamide group was dissolved not only in water but also in cyclohexane, although the solubility toward such solvents was lower than that toward methanol or chloroform. From the UV-Vis spectra, it was confirmed that thione-type isomer was major in these solvents except for cyclohexane. Autoxidation reactions were monitored in methanol or methanol-d₄, and ca. 36% of 2-mercaptopyridyl groups were oxidized into disulfide bonds within a month in ¹H-NMR spectral measurements. Bond-exchange reactions between 2,2’-dipyridyl disulfide and a thiol compound were observed more clearly in methanol than in chloroform, suggesting a solvent effect to dissolution of corresponding disulfide compounds.

The influence of the weave, thickness, and fiber material of the fabric on the direct determination of the protein in the fabric by the bicinchoninic acid (BCA) method was investigated in this paper. Six kinds of cotton fabrics, with different weaves and thicknesses, and eight kinds of plain-weave fabrics with different fiber materials were used as the test swatches. The K/S value was calculated from the reflectance, based on the color reaction of the BCA method, and the quantitation was evaluated based on the relationship between the K/S value and the protein concentration. Based on the results, it was determined that the influence of the weave and thickness was not significant, and the quantitation was good. Contrastingly, it was found that protein fibers (wool and silk) and the cuprammonium rayon, in which copper ions remained, which react with the C solution of the BCA method, are not suitable for this method.