Broering James M, Bommarius Andreas S
School of Chemical & Biomolecular Engineering, School of Chemistry and Biochemistry, Georgia Institute of Technology, 315 Ferst Drive, Atlanta, GA 30332-0363, USA.
J Phys Chem B. 2005 Nov 3;109(43):20612-9. doi: 10.1021/jp053618+.
Dissolved salts are known to affect properties of proteins in solution including solubility and melting temperature, and the effects of dissolved salts can be ranked qualitatively by the Hofmeister series. We seek a quantitative model to predict the effects of salts in the Hofmeister series on the deactivation kinetics of enzymes. Such a model would allow for a better prediction of useful biocatalyst lifetimes or an improved estimation of protein-based pharmaceutical shelf life. Here we consider a number of salt properties that are proposed indicators of Hofmeister effects in the literature as a means for predicting salt effects on the deactivation of horse liver alcohol dehydrogenase (HL-ADH), alpha-chymotrypsin, and monomeric red fluorescent protein (mRFP). We find that surface tension increments are not accurate predictors of salt effects but find a common trend between observed deactivation constants and B-viscosity coefficients of the Jones-Dole equation, which are indicative of ion hydration. This trend suggests that deactivation constants (log k(d,obs)) vary linearly with chaotropic B-viscosity coefficients but are relatively unchanged in kosmotropic solutions. The invariance with kosmotropic B-viscosity coefficients suggests the existence of a minimum deactivation constant for proteins. Differential scanning calorimetry is used to measure protein melting temperatures and thermodynamic parameters, which are used to calculate the intrinsic irreversible deactivation constant. We find that either the protein unfolding rate or the rate of intrinsic irreversible deactivation can control the observed deactivation rates.
已知溶解盐会影响溶液中蛋白质的性质，包括溶解度和熔化温度，并且溶解盐的影响可以通过霍夫迈斯特序列进行定性排序。我们寻求一个定量模型来预测霍夫迈斯特序列中的盐对酶失活动力学的影响。这样的模型将有助于更好地预测有用生物催化剂的寿命，或改进基于蛋白质的药物保质期的估计。在这里，我们考虑了文献中提出的一些作为霍夫迈斯特效应指标的盐性质，以此作为预测盐对马肝醇脱氢酶（HL - ADH）、α - 胰凝乳蛋白酶和单体红色荧光蛋白（mRFP）失活影响的一种方法。我们发现表面张力增量不是盐效应的准确预测指标，但发现观察到的失活常数与琼斯 - 多尔方程的B - 粘度系数之间存在共同趋势，这表明离子水合作用。这种趋势表明失活常数（log k(d,obs)）随离液序列高的B - 粘度系数线性变化，但在促溶溶液中相对不变。与促溶B - 粘度系数的不变性表明蛋白质存在最小失活常数。差示扫描量热法用于测量蛋白质熔化温度和热力学参数，这些参数用于计算内在不可逆失活常数。我们发现蛋白质解折叠速率或内在不可逆失活速率都可以控制观察到的失活速率。
