魚肉アクトミオシンの粘度に関する研究-I

Abstract

Some fundamental problems concerning the viscosity of actomyosin were studied by using a tilting viscometer (Fig. 1) designed by WADA3), in which control of velocity gradient of the flow can be readily practiced simply by changing the position on the supporting plate to which the curved end of the viscometer is fixed. Relative viscosity ηγ and velocity gradient ?? are calculated from equations (1) and (2) respectively, where to and ts are efflux times of solvent and solution, respectively. V and R in equation (2) are the efflux volume and the radius of the capillary, respectively. Viscosity of carp actomyosin solution prepared according to Table 1 was measured at varying velocity gradients ( ?? ) and concentrations (c). Some one hour was required for the whole measurement, but the solution proved to be stable at least for one hour at 10°C. (Table 2) and 20°C. Apparent decrease in viscosity was observed with increasing velocity gradient (Fig. 2), as already reported by many workers with rabbit1, 2) and carp6) actomyosins. At quite a low velocity gradient ( ?? <100 sec-1), however, ηγ showed a fixed value independent of ?? at any concentration studied (0.03-0.25%) as illustrated in Fig. 2. This is not concordant with the result obtained by HAMOIR who measured viscosity of carp actomyosin under varying pressures form 0 to 15cm. of water by means of a capillary tube equipped with an air reservoir. On the other hand, the same results as ours have been obtained with nitrocellulose in butyl acetate and polystyrene in toluene as well as tobacco mosaic virus in water7). The reason of the disagreement between the result of HAMOIR and ours is obscure. Intrinsic viscosity [η] of carp actomyosin was determined from ηsp/c or In ηγ/c by extrapolating both c and ?? to zero and was found to be 2.0-6.0 (Fig. 3). Measuring temperature seemed to exert an influence hardly or but slightly, if any, on intrinsic viscosity of carp actomyosin; [η]=2.5 at 5°C., and 2.2 at 20°C. were obtained with one and the same preparation (Fig. 5). Viscosity number Zη=(2.3 log ηγ)/c is often conveniently used as a substitute of intrinsic viscosity. Since, however, in carp actomyosin no linearity was found except one out of a dozen cases in the relationship between In ηγ and c at least within our experimental conditions (Fig. 4), viscosity number cannot be a characteristic quantity independent of experimental conditions. Similarly in carp actomyosin at least within our experimental conditions, ATP-sensitivity, Zη-ZηATP/ZηATP, proposed by PORTZEHL et al cannot be taken significant in characterizing an actomyosin preparation, independently of experimental conditions. The initial slope of the curve (ηsp/c)c→o- ?? or (In ηγ/c)c→o- ?? affords a rough measure of the readiness with which the molecules are orientated, that is the shape of the molecule; and the initial slope of the curve (ηsp/c) ?? →o-c or (In ηγ/c) ?? →o-c offers some knowledge about the extent of intermolecular interaction (cf. Fig. 6).