PARTIAL SPECIFIC VOLUMES AND INTERACTIONS WITH SOLVENT COMPONENTS OF PROTEINS IN GUANIDINE HYDRO CHLORIDE
PARTIAL SPECIFIC VOLUMES AND INTERACTIONS WITH SOLVENT COMPONENTS OF PROTEINS IN GUANIDINE HYDRO CHLORIDE
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DOI：
10.1021/bi00699a005
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发表时间：
1974-01-01
期刊：
影响因子：
2.9
通讯作者：
TIMASHEFF S N
中科院分区：
文献类型：
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作者：
LEE J C;TIMASHEFF S N
James C. Lee 和 Serge N. Timasheff* 摘要：通过密度测量确定 12 种蛋白质的部分比容。对于这些处于天然状态的蛋白质，部分比容的测定值通常与公认的文献值非常一致，牛α-乳清蛋白除外。测定值 0.704 与溶菌酶的测定值相似。还测量了 6 m 盐酸胍与这些蛋白质的优先相互作用参数。对于所研究的 12 种蛋白质，与溶剂成分的优先相互作用在 0 至 0.17 g 胍之间变化。尽管准确了解蛋白质的部分比容 v 对于通过超速离心数据和小角 X 射线散射测定分子量至关重要，但在过去很少测量该参数。分子量由假定的v值计算，或由氨基酸组成计算。然而，准确测量部分比容的重要性已得到普遍认可，因为该参数中的小误差在分子量计算中会成倍增加，特别是在变性剂浓溶液（如 6 m Gdn-HCl）中进行测量时，* 1 这是亚基系统研究中的常见做法。分子量估计的不确定性可能导致对天然大分子组装中亚基数量的错误结论，并导致缔合系统热力学参数计算中的严重错误。一个典型的例子是多年来关于兔肌肉醛缩酶中多肽链的确切数量的不确定性（Kawahara 和 Tanford，1966；Schachman 和 Edelstein，1966；Castellino 和 Barker，1968；Reisler 和 Eisenberg，1969；Meigben 和 Schachman，1970）。直到最近，可用于测量部分比容的方法要么经常需要大量的材料（如传统比重瓶），要么涉及漫长而复杂的程序（如密度梯度柱技术）（Linderstrpm-Lang 和 Lanz，1935；Hvidt 等，1954；Reithel 和 Sakura，1963）。最近，已经描述了几种需要少量材料的新的、优雅的 v 测量方法。其中包括 Edelstein 和 Schach-man (1967) 的 H20~ D20 方法、Ulrich 等人 (1964) 的磁性浮子方法，以及基于“音叉”振动频率的精密密度计，该音叉由填充样品的石英组成。 布兰代斯大学生物化学研究生部出版物 924，沃尔瑟姆，马萨诸塞州 02154。7 月 23 日收到， 1973。这些研究部分得到美国国立卫生研究院拨款 GM 14603 和 NS 5241 以及美国国家科学基金会拨款 GB12619 的支持。
James C. Lee and Serge N. Timasheff* abstract: The partial specific volumes of twelve proteins were determined by density measurements. For these proteins in their native state, the determined values of partial specific volumes are generally in good agreement with the accepted literature values except in the case of bovine a-lactalbumin. The determined value of 0.704 is similar to that found for lysozyme. Preferential interaction parameters of 6 m guanidine hydrochloride with these proteins were also measured. For the twelve proteins studied, the preferential interactionwith solvent components varies between 0 and 0.17 g of guanidine. ŋXlthough an exact knowledge of the partial specific volume, v, of a protein isessential for the determination of molecular weights from ultracentrifuge data and small-angle X-ray scattering, in thepast this parameter was seldom measured. The molecular weights were calculated from values of v assumed, or calculated from amino acid composition. And yet the importance of accurate measurements of the partial specific volume was generally recognized, since a small error in that parameter is multiplied several fold in the calcula-tion of the molecular weight, in particular when measurements are carried out in concentrated solutions of denaturant, such as 6 m Gdn-HCl,* 1 a frequent practice in studies of subunit systems. Uncertainties in estimates of molecular weight can lead to wrong conclusions about the number of subunits in the native macromolecular assembly and to serious errors in the calculation of the thermodynamic parameters of associating systems. A classical example is the uncertainty which prevailed for several years about theexact number of polypeptide chains in rabbit muscle aldolase (Kawahara and Tanford, 1966; Schachman and Edelstein, 1966; Castellino and Barker, 1968; Reisler and Eisenberg, 1969; Meigben and Schachman, 1970). Until recently, the methods available for the measurement of the partial specific volume either required frequentlyprohibitive amounts of material, as in conventional pycnometry, or involved long complicated procedures, as in the density gradient column technique (Linderstrpm-Lang and Lanz, 1935; Hvidt et al., 1954; Reithel and Sakura, 1963). Recently, several new and elegant approaches to the measurement of v, requiring small amounts of material, have been described. These include the H20~ D20 method of Edelstein and Schach-man (1967), the magnetic float method of Ulrich et al.(1964), and the precision densimeter, based on the frequency of vibration of a “tuning fork,” consisting of a sample-filled quartz t Publication 924 of the GraduateDepartment of Biochemistry, Brandéis University, Waltham, Massachusetts 02154. Received July 23, 1973. These studies were supported in part by National Institutes of Health Grants GM 14603 and NS 5241, and by National Science Foundation Grant GB12619.