------------------------------------------------------------------------
    COLLOQUIUM OF THE LABORATORY FOR COMPUTER DESIGN OF MATERIALS
        Institute for Computational Sciences and Informatics
	                      CSI 898-Sec 001  
------------------------------------------------------------------------
   ROLE OF MULTIPLE MINIMA IN PROTEIN VIBRATIONAL SPECTROSCOPY.
        ANHARMONIC EIGENFUNCTIONS FOR DIFFERENT CONFORMERS.

                           Adrian Roitberg
     National Institute of Standards and Technology, Gaithersburg,MD

Recently, we proposed a method to calculate anharmonic vibrational
wavefunctions in large systems [1]. We applied it to the protein BPTI, and
found that the anharmonic effects, when included on top of the normal mode
picture, gave rise to a blue shift in the vibrational distribution as well as
in the predicted IR spectrum. That calculation was performed in a wet sample
of the protein, on a structure obtained after minimization of an equilibrated
run. In this presentation, we will introduce the next level of refinement.
One of the successes of small molecular spectroscopy has been to correlate
spectra with conformations. A current dream consist of trying to achieve the
same success for biomolecules of large size. To address this possibility, we
repeated our previous calculation on a series of thermally accessible
minima. Our results show that there is a difference in the vibrational
spectra for different minima, but that the bottleneck is related
to the large number of minima present in the system, which would make a clean
assignment a potential problem.
[1]Roitberg A., Gerber B., Elber R. and Ratner M., Science(1995) 268:1319-1322

	               Monday , September 15 1997
                                 4:30 pm
                        Room 206, Science & Tech. I

Refreshments will be served.
--------------------------------------------------------------------------
(http://www.csi.gmu.edu/lcdm/seminar/schedule.html)