Snyder G H
Biochemistry. 1987 Feb 10;26(3):688-94. doi: 10.1021/bi00377a005.
The cyanogen bromide fragment comprising residues 115-181 of Kunitz soybean trypsin inhibitor is a soluble random-coil peptide at pH 7 containing two cysteines separated by eight other amino acids in the primary sequence. Four of the six rate constants have been determined for the three disulfide exchange reactions between this fragment and oxidized and reduced forms of N-acetylcysteine methyl ester. The rate constant for intramolecular loop formation in the fragment containing one thiolate anion and one sulfur connected by a disulfide bond to the small cysteine analogue is 0.36 +/- 0.15 s-1 at 23 degrees C in 3 M guanidine hydrochloride. This measurement provides a frame of reference corresponding to formation of a small but sterically unstrained loop, the fast limit for intramolecular disulfide exchange in a random-coil peptide.
库尼茨大豆胰蛋白酶抑制剂中包含115 - 181位残基的溴化氰片段，在pH 7时是一种可溶性无规卷曲肽，其一级序列中有两个半胱氨酸，中间相隔八个其他氨基酸。已测定了该片段与N - 乙酰半胱氨酸甲酯的氧化态和还原态之间三个二硫键交换反应的六个速率常数中的四个。在3 M盐酸胍中，于23℃下，含有一个硫醇盐阴离子和一个通过二硫键与小半胱氨酸类似物相连的硫的片段中分子内环形成的速率常数为0.36±0.15 s⁻¹。该测量提供了一个参考框架，对应于一个小的但空间上无张力的环的形成，这是无规卷曲肽分子内二硫键交换的快速极限。
