純蛋白質定量に用いる蛋白質沈澱剤について(第3報)

0.3%NaOH性60%熱アルコール溶性蛋白質のトリクロル酢酸による沈澱性

抄録

In our previous experiments, it was found that the precipitable nitrogen in the hot 0.3% alkaline 60% alcohol soluble fraction of leafy vegetables by trichloroacetic acid was less than the total nitrogen in the fraction. To make this clear, the precipitabilities of proteins in 0.3% alkaline 60% alcohol solution by trichloroacetic acid were studied.The results obtained were as follows:
(1) By the treatment of proteins in 60% alcohol solution by trichloroacetic acid, the protein of soybean leaf precipitated as much as 36.9% by 5% acid solution, but none of the protein of Japanese radish leaf. The amount of protein precipitate washed with 2% trichloroacetic acid solution did not agree with that washed with 2% trichloroacetic-60% alcohol solution, which indicated that the concentrated alcohol solution inhibited the precipitation of protein by trichloroacetic acid. Accordingly the precipitate should not be washed with alcohol solution.
(2) For the determination of the true protein in the hot 0.3% alkaline 60% alcohol soluble fraction of leafy vegetable, the alcohol should be removed from the solution, and there after 5% trichloroacetic acid as the precipitant and 2% acid solution for washing the precipitate were employed.