Sippl M J
Center for Applied Molecular Engineering, University of Salzburg, Austria.
J Mol Biol. 1996 Aug 2;260(5):644-8. doi: 10.1006/jmbi.1996.0427.
We estimate the Helmholtz free energy of peptide hydrogen bonds in native protein structures as a function of spatial separation between donor and acceptor atoms. The resulting potential function has a deep narrow well at H-bond contact but bond formation is hindered by a barrier and the net change in free energy is close to zero. The barrier provides a molecular lock mechanism acting as a kinetic trap. Once formed, H-bonds keep protein chains in a precise orientation. However, bond formation requires energy input and opposes protein folding. In contrast, the free energy functions of most side-chain interactions have no energy barriers. They lack spatial precision but free energy differences of contact formation are substantial. These interactions drive folding and stabilize structures but precision is mediated and maintained by H-bonds.
我们估计天然蛋白质结构中肽氢键的亥姆霍兹自由能是供体和受体原子之间空间距离的函数。所得的势能函数在氢键接触处有一个深而窄的阱，但键的形成受到一个势垒的阻碍，自由能的净变化接近于零。该势垒提供了一种作为动力学陷阱的分子锁定机制。一旦形成，氢键会使蛋白质链保持精确的取向。然而，键的形成需要能量输入，并且与蛋白质折叠相反。相比之下，大多数侧链相互作用的自由能函数没有能量势垒。它们缺乏空间精度，但接触形成的自由能差异很大。这些相互作用驱动折叠并稳定结构，但精度是由氢键介导和维持的。
