Nuclear quantum mechanical

Hwang, J.-K. Warshel, A., How important are quantum mechanical nuclear motions in enzyme catalysis, 7. Am. Chem. Soc. 1996,118, 11745-11751... 

The calculated [using a quantized classical path (QCP) approach] and observed isotope effects and rate constants are in good agreement for the proton-transfer step in the catalytic reaction of carbonic anhydrase. This approach takes account of the role of quantum mechanical nuclear motions in enzyme reactions.208... 

THEORETICAL PHYSICS, Georg Joos, with Ira M. Freeman. Classic overview covers essential math, mechanics, electromagnetic theory, thermodynamics, quantum mechanics, nuclear physics, other topics. First paperback edition, xxiii + 885pp. 55 x 8(4. 65227-0 Pa. 17.95... 

The quantitized classical path approach (Hwang and Warshel, 1996) was applied to the analysis of quantum mechanical nuclear motion in enzyme catalysis. According to this approach the rate constant of the process... 

The Born-Oppenheimer approximation uncouples electron and nuclear motion. The latter concerns massive (at least, relative to electrons) bodies, and much lower velocities while the formal velocity of an electron may approach the speed of light, a molecule in the gas phase travels at about the speed of a supersonic jet plane. While electronic energies must be calculated by quantum mechanics, nuclear motions are more easily described in a classical framework. 

The quantum mechanical nuclear dipole moment is defined as... 

Warshel and Chu [42] and Hwang et al. [60] were the first to calculate the contribution of tunneling and other nuclear quantum effects to PT in solution and enzyme catalysis, respectively. Since then, and in particular in the past few years, there has been a significant increase in simulations of quantum mechanical-nuclear effects in enzyme and in solution reactions [16]. The approaches used range from the quantized classical path (QCP) (for example. Refs. [4, 58, 95]), the centroid path integral approach [54, 55], and variational transition state theory [96], to the molecular dynamics with quantum transition (MDQT) surface hopping method [31] and density matrix evolution [97-99]. Most studies of enzymatic reactions did not yet examine the reference water reaction, and thus could only evaluate the quantum mechanical contribution to the enzyme rate constant, rather than the corresponding catalytic effect. However, studies that explored the actual catalytic contributions (for example. Refs. [4, 58, 95]) concluded that the quantum mechanical contributions are similar for the reaction in the enzyme and in solution, and thus, do not contribute to catalysis. 

Special attention was given to the conformations about the C-5-C-6 bond in semiempirical quantum mechanical nuclear shielding calculations on a series of hexopyranoses," and in molecular mechanics simulations of methyl a- and P-d-gluco-, -galacto-, and talo-pyranoside in aqueous solution," " as well as to the conformation of the acetamido group in 2-acetamido-2-deoxy-D-allo- and -d-gluco-pyranose derivatives, such as 18-20." ... 

However, the hquid drop model is powerless to explain the more detailed features within the binding energy per nucleon curve, such as the various discontinuities that are superimposed on it, reflecting the enhanced stabihties of nuclei of He, C, 0, Ne, and Mg. To explain these more subtle features, we need to consider the quantum mechanical nuclear-sheU model, which bears a number of similarities to the electron-shell model as described in chapters 7 and 9. 

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