Chem 380.37 Lecture Notes 21

To completely optimize the molecule required 79

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Unformatted text preview: To completely optimize the molecule required 79 cycles, or a total of 263 days of computing! How good was the calculation? Figure 2, taken from the article, shows the heavy-atom framework from the calculation and from the X-ray crystal structure. The agreement is remarkable considering that the calculation was performed in the gas phase and was compared to the solid-state crystal structure. 2 Figure 2. Comparison of heavy atom framework from Hartree-Fock geometry optimization and Xray crystal structure of crambin [from C. Van Alsenoy, C.-H. Yu, A. Peeters, J. M. L. Martin, and L. Schafer, J. Phys. Chem. A 1 998, 1 02, 2246.] Some examples of the agreement between the calculated and X-ray geometrical parameters are the RMS deviation in N-C(α) bond lengths is 0.013 Å, while the RMS deviation in N-C(α)-C´ bond angles is 1.5º. Active S ite M odels While molecular orbital calculations of proteins like crambin can now be carried out, it is still prohibitively expensive in terms of CPU time to d...
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This document was uploaded on 03/04/2014 for the course CHEM 380.37 at Illinois State.

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