医薬品とタンパク質との結合に関する物理化学的研究(第6報) : 分光学的方法によるメチルオレンジと水晶体タンパク質との結合について

抄録

Binding of Methyl Orange with α- and β-crystallins, the main proteins of lens cortex, was examined spectrophotometrically, in the range of pH 1.7∼8.0. Further, this binding at pH 3.6 was studied by the use of dialysis equilibrium method. As a result, the following points were clarified. 1) The binding of Methyl Orange with α- and β-crystallins in the range of pH 1.7∼8.0 occurs between the sulfone group in Methyl Orange and positively charged amino acid residue in the proteins. No difference was observed in the binding mechanism between the two proteins. 2) The number of binding sites of with Methyl Orange with the two proteins at pH 3.6 is smaller than that in the higher pH range. This fact is considered to be due to changes in the structure of the proteins at pH 3.6. 3) The binding of Methyl Orange with α-crystallin becomes the maximum at around pH 3.6, and that with β-crystalline is at around pH 3.2. This fact is considered to be due to the acid-type structure of Methyl Orange in the acid region, resulting in static repulsion of the positively charged molecule, and decoiling of the protein structure in the acid region.