Bending motions: potential surfaces

The equilibrium geometries of Cp2M (M = Yb, Eu, Sm) were studied by ab initio pseudopotential calculations at the Hartree-Fock (HF), MP2 and CSID levels. In the Hartree-Fock calculations [118] all the metallocenes favoured regular sandwich-type equilibrium structures with increasingly shallow potential energy surfaces for the bending motions along the series, M = Ca, Yb, Sr, Eu, Sm, and Ba. 

Recent ab initio calculations have attempted to probe the fundamental source of the reversal of H/D preference in ionic as compared to neutral systems, using water as a test base. A harmonic analysis of the potential energy surface of the water dimer, computed with a 6-31G basis set, indicates that the preference for D in the bridging site can be explained in a manner similar to that described earlier for HF - HF. The frequency of the bending motion of the bridging atom is sensitive to its mass this effect leads to a lower vibrational energy of some 0.2 kcal/mol when the heavier D undergoes this motion. The computations indicated that electron correlation has little effect upon this conclusion, even its quantitative aspects. While the treatment was purely harmonic in nature, other calculations have indicated that anharmonicity effects yield very little distinction between one isotopomer and the next. 

E-fS ES ES. The standard deviation of the distribution, (Atopen ) = 8.3 2ms, reflects the distribution bandwidth. For the individual T4 lysozyme molecules examined under the same enz unatic reaction conditions, we found that the first and second moments of the single-molecule topen distributions are homogeneous, within the error bars. The hinge-bending motion allows sufficient structural flexibility for the enzyme to optimize its domain conformation the donor fluorescence essentially reaches the same intensity in each turnover, reflecting the domain conformation reoccurrence. The distribution with a defined first moment and second moment shows typical oscillatory conformational motions. The nonequilibrium conformational motions in forming the active enzymatic reaction intermediate states intrinsically define a recurrence of the essentially similar potential surface for the enzymatic reaction to occur, which represents a memory effect in the enzymatic reaction conformational dynamics [12,41,42]. 

Free energy of solvation Absolute and ApK Free energy of binding Redox potentials PB forces Electrostatics for Brownian dynamics calculations Rate constants Loop and hinge bending motions Polymer dynamics Protein-surface dynamics... 

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