类粘蛋白对自旋标记普萘洛尔和自旋标记孕酮的结合作用。

The binding of spin-labeled propranolol and spin-labeled progesterone by orosomucoid.

作者信息

Kirley T L, Sprague E D, Halsall H B

出版信息

Biophys Chem. 1982 Jun;15(3):209-16. doi: 10.1016/0301-4622(82)80004-5.

Abstract

The binding of the spin-labeled propranolol and spin-labeled progesterone to human orosomucoid has been studied as a function of temperature by electron spin resonance (ESR) techniques. At 20 degrees C the association constants are 1.9 x 10(6) and 4.9 x 10(5) M-1, respectively. In each case, the binding is competitive with unlabeled ligand. Above about 50 degrees C the apparent association constant for both ligands decreases rapidly with increasing temperature. This is due to thermal denaturation of the orosomucoid, as was shown independently by ultraviolet absorption spectroscopy and differential scanning calorimetry. Below the denaturation region the number of binding sites per orosomucoid molecule remains constant at approx. 1. Examination of the thermodynamic parameters shows the progesterone binding at 37 degrees C to be essentially enthalpically driven, while the propranolol binding at 37 degrees C has a substantial entropic component.

摘要

通过电子自旋共振（ESR）技术，研究了自旋标记的普萘洛尔和自旋标记的孕酮与人血清类黏蛋白的结合情况，并将其作为温度的函数。在20摄氏度时，缔合常数分别为1.9×10⁶和4.9×10⁵ M⁻¹。在每种情况下，这种结合都与未标记的配体存在竞争。在约50摄氏度以上，两种配体的表观缔合常数均随温度升高而迅速降低。这是由于血清类黏蛋白发生了热变性，这一点已通过紫外吸收光谱法和差示扫描量热法独立证实。在变性区域以下，每个血清类黏蛋白分子的结合位点数保持恒定，约为1个。对热力学参数的研究表明，37摄氏度时孕酮的结合基本上由焓驱动，而37摄氏度时普萘洛尔的结合则有很大的熵成分。