抄録
Some physico-chemical studies were carried out on myosin A labelled with a fluo-rescent dye, 1-dimethylaminonaphthalene-5-sulfonyl chloride, and the following results were obtained.
1. The appearance of the faster sediment-ing peak and the increase in intrinsic viscosity became more remarkable, as the degree of the labelling with the dye increased, whereas considerable changes in the content of abnormal tyrosine and in the helical content were scarcely observed.
2. The attached dye was scarcely released by dialysis against alkaline solutions and the ATPase activity of myosin A was not restored by this treatment.
3. The dye-labelled myosin A emitted a visible fluorescence with a maximum at 505 mμ when the dye moiety was excited at 330 mge, and it emitted both the ultraviolet fluorescence of 340 mμ and the visible fluo-rescence of 505 mμ when the aromatic residues of the protein was excited at 285 mμ. Urea or dioxane decreased both the fluorescence intensity and -[m']400. Ethanol scarcely influenced the helical content estimated from the bo term, but increased the ultraviolet fluorescence and decreased the visible fluo-rescence.
Based on these results, some physical properties of the dye-labelled myosin A and the structure of the part attached by the dye were discussed.
The authors would like to thank Departments of Physics and Pharmacology in Sapporo Medical College for the instrumentation for the measurements of optical rotatory dispersion and fluorescence spectra.
