LOW BARRIER HYDROGEN BONDS IN ENZYMIC CATALYSIS

这个项目的目的是寻找实验证据， 支持最近的假设，即酶获得所需的能量 用于催化，通过形成非常强的，低势垒的氢键， 过渡态，或其他不稳定的中间体，而 在基态只有弱氢键。 低势垒 氢键具有非常低的场质子NMR化学位移，并且我们 我们将在酶复合物中寻找这种低场信号， 从其他证据来看，他们应该在场。 比如说， 我们将研究与氯富马酸盐复合的脱氢酶， 3-硝基乳酸盐或3-硝基丙酸盐，因为这样的络合物应该 模拟反应中烯醇化的“碳负离子”中间体， 必须通过低势垒氢键来稳定。 低势垒 氢键还具有低氘分馏因子， 可以通过对混合H2O和D2 O中的NMR峰进行积分来测量 溶剂后 我们将测量任何低场的分馏因子 我们在酶复合物中发现的峰， 的NMR谱中先前看到的低场峰的因素， 天冬氨酸转氨酶

The purpose of this project is to seek experimental evidence to support the recent hypothesis that enzymes obtain the energy needed for catalysis by forming very strong, low-barrier, hydrogen bonds in the transition state, or in otherwise unstable intermediates, while having only weak hydrogen bonds in the ground state. Low-barrier hydrogen bonds have very low field proton NMR chemical shifts, and we will look for such low field signals in enzyme complexes where we think, from other evidence, that they should be present. For example, we will look at fumarase complexed with chlorofumarate, 3-nitrolactate, or 3-nitropropionate, since such complexes should mimic the enolized "carbanion" intermediate in the reaction which we believe must be stabilized by low-barrier hydrogen bonds. Low-barrier hydrogen bonds also have low deuterium fractionation factors, which can be measured by integrating the NMR peaks in mixed H2O and D2O solvent. We will measure the fractionation factors of any low field peaks we find in fumarase complexes, and also the fractionation factors of the low field peaks previously seen in the NMR spectra of aspartate transaminase.