Research Activity of Prof. Donald D. Shillady
The past three years has been spent largely focused on the problem of electron correlation in solvent clusters. A new method has been coded in which Coulomb's Law of electron repulsion is replaced by a screened-Coulomb interaction which results in near experimental energy values in computer run times only about 60% longer than traditional self-consistent-field methods. This is compared to other post-Hartree Fock methods such as Configuration Interaction and Moller-Plesset perturbation methods which require run times about ten times as long as SCF calculations. The resulting program PCLOBE is being developed for use by students on PCs and is in testing mode by undergraduates at this time.
Another interest of long standing in our laboratory is the measurement and calculation of circular dichrosim (CD) and magnetically-induced circular dichroism (MCD, Faraday Effect). Computer coding for direct calculation of CD and MCD bands has been incorporated into PCLOBE and recent work on melatonin in solution has used this analysis. Past work on the MCD of serotonin has recently been extended to melatonin. Computer modeling of melatonin has shown that the flexible side chain of melatonin has many possible conformations but in water there is a low energy conformation that is stabilized by a water molecule in a sort of "basket" conformation. Comparison to MCD spectra shows that this conformation is not favored in methanol and the calculations are in agreement with spectral measurements. It is hoped that PCLOBE will become widely used for CD/MCD analysis of biologically important molecules and it is one of only a few computer programs available for this type analysis.
Virginia Commonwealth University
Date last modified:
10/27/04
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