Additive transfer free energies of the peptide backbone unit that are independent of the model compound and the choice of concentration scale
Additive transfer free energies of the peptide backbone unit that are independent of the model compound and the choice of concentration scale
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DOI：
10.1021/bi035908r
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发表时间：
2004-02-10
期刊：
影响因子：
2.9
通讯作者：
Bolen, DW
中科院分区：
文献类型：
--
作者：
Auton, M;Bolen, DW
通过了解蛋白质变性时新暴露的化学基团的单个转移自由能，并假设基团转移自由能贡献是相加的，应该可以预测蛋白质在变性剂存在下的稳定性。不幸的是，一些悬而未决的问题严重阻碍了定量发展的蛋白质折叠/展开的这种转移模型。这些问题包括缺乏足够的证明，基团转移自由能（DeltaG（tr））是添加剂和独立的模型化合物的选择，所产生的问题，从依赖的DeltaG（tr）的浓度范围内，缺乏知识的活动系数，并在获得DeltaG（tr）值中使用的数学结构的有效性。关于从水转移到1 M浓度的天然存在的渗透剂，三甲胺-N-氧化物（TMAO），肌氨酸，甜菜碱，脯氨酸，甘油，山梨醇，蔗糖，海藻糖和尿素，使用环状甘氨酰甘氨酸，两性离子甘氨酸肽，和N-乙酰甘氨酸酰胺肽作为蛋白质的肽骨架的模型，我们着手解决这些问题，并获得肽骨架单元的DeltaG（tr）值。我们展示了实验方法，该实验方法可用于浓度规模的选择，并展示了所有溶剂系统研究的肽骨架单元的DeltaG（TR）的加和性。有证据表明DeltaG（tr）值与所研究的化学模型无关，并给出实验条件来说明何时数学结构有效以及何时可以忽略活度系数。解决了长期存在的问题，阻碍了发展的转移模型，现在有可能设计转移实验，产生可靠的和定量的值之间的相互作用的渗透剂的溶剂和天然和未折叠的蛋白质。
With knowledge of individual transfer free energies of chemical groups that become newly exposed on protein denaturation and assuming the group transfer free energy contributions are additive, it should be possible to predict the stability of a protein in the presence of denaturant. Unfortunately, several unresolved issues have seriously hampered quantitative development of this transfer model for protein folding/unfolding. These issues include the lack of adequate demonstration that group transfer free energies (DeltaG(tr)) are additive and independent of the choice of model compound, the problem arising from dependence of DeltaG(tr) on concentration scales, the lack of knowledge of activity coefficients, and the validity of the mathematical constructs used in obtaining DeltaG(tr) values. Regarding transfer from water to 1 M concentrations of the naturally occurring osmolytes, trimethylamine-N-oxide (TMAO), sarcosine, betaine, proline, glycerol, sorbitol, sucrose, trehalose, and urea, using cyclic glycylglycine, zwitterionic glycine peptides, and N-acetylglycine amide peptides as models for the peptide backbone of proteins, we set out to address these issues and obtain DeltaG(tr) values for the peptide backbone unit. We demonstrate experimental approaches that obviate the choice of concentration scale and demonstrate additivity in DeltaG(tr) of the peptide backbone unit for all solvent systems studied. Evidence is presented to show that the DeltaG(tr) values are independent of the chemical model studied, and experimental conditions are given to illustrate when the mathematical constructs are valid and when activity coefficients can be ignored. Resolution of the long-standing issues that have stymied development of the transfer model now make it possible to design transfer experiments that yield reliable and quantitative values for the interactions between osmolyte-containing solvents and native and unfolded protein.