蛋白と色素との結合に及ぼす尿素の影響

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By using equilibrium dialysis method, it was intended (i) to ascertain the findings obtained spectrophotometrically by Klotz et al. that urea not only inhibits the interaction between serum albumin and methyl orange (MO), but also splits the preformed combination between them, and (ii) to examine the influence of urea upon the binding of MO and methylene blue (MB) to fish “actomyosins”. Equilibrium dialysis 5ml. of protein solution in inside cell was dialysed against 10ml. of dye solution in outside cell through cellophane for 72 hr. at 4°C.* Control dialysis was set up in order to make correction for absorption of dye on membrane itself. Amount of bound dye was calculated from the difference between equilibrium concentrations of free dye in ouside cells of protein-containing and control dialysis systems. Results 1. In 6M urea, combination between serum albumin and MO did not take place (Table 2), and also the preformed combination was abolished (Table 4). Binding of MO to cellophane which was used as semipermeable membrane was also completely inhibited in 6M urea but the binding once formed was hardly affected. 2. In 2M urea, the binding of MO to albumin took place to some extent though an inhibitory effect of urea was marked. The extent of combination was the same whether albumin and MO were dialysed in 2M urea solution, or albumin in 6M urea was dialysed against 3 vol. of phosphate buffer containing MO (Table 2, and Fig. 1, Curve C). 3. 0.6M malonic amide and 1M urea are equivalent in raising dielectric constant of water. The former, however, inhibited only slightly the binding of MO to albumin, but the latter noticeably. Thus the inhibitory effect of urea cannot be explained soley by increase in dielectric constant of the solution. 4. “Actomyosin” either from horse mackerel or squid combined with both MO and MB but albumins do not combine with MB. Under the conditions of the present experiments there seemed to exist the following orders with regard to the combining abilities of dye and of “actomyosin”: MB > MO, and squid “actomyosin” > horse mackerel “actomyosin ”. 5. Carp “actomyosin” which was freed from urea by dialysis after it had been kept dissolved in 6M urea for 24 hr., showed the same binding ability toward MO as native carp “actomyosin”. Results 2 and 5 show that effect of urea upon the combination of protein and MO is reversible. * For the apparatus, see this Bull. 22, 260 (1956).
公益社団法人日本水産学会の論文

蛋白と色素との結合に及ぼす尿素の影響

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