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Section II: Chemistry Science Center.

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12:00 MECHANISTIC INSIGHT OF FRAGMENTATION CHARACTERISTICS OF MACROLIDE ANTIBIOTICS, Victor Ibeanusi and Yassin Jeilani, Spelman College, Environmental Science and Studies. Macrolide antibiotics are composed of a large ring (14 to 16 carbons) on which several sugars are attached, some of these are amino sugars with diethylamino group. Mass spectrometric characterization of macrolide antibiotics has been a challenge because of low number of characteristic fragments in their collision induced dissociation. Tandem mass spectrometric fragmentation of these antibiotics show two types of dissociations: a) cleavage of glycosidic linkages attaching the sugars to the macrolide ring and elimination of water, and b) macrolide ring opening cleavages. In this study, erythromycin, tylosin, and oleandomycin were selected to study both types of fragmentations. Using collision induced dissociation data, a multipathway fragmention mechanism was proposed for the selected antibiotics.

12:15 DRUGS BOUND TO THE ENZYME HUMAN GLUTAMINYL CYCLASE **, Breanna Spires and Robert Zurales, Middle Georgia College, Cochran, GA 31014. We started our research by visiting the Protein Data Bank website (www.pdb.org). Here we selected three different recent studies of a drug bound to the enzyme human glutaminyl cyclase, an enzyme implicated in Alzheimer' disease. We attempted to calculate which drug fits the best. We selected key amino acid side chains and deleted all other atoms in the protein. Since the crystal structure does not include hydrogen atoms, we used our chemical intuition to place the hydrogen atoms accordingly. First we allowed the hydrogen atoms to move, freezing the positions of the heavy atoms and optimizing the positions of the hydrogen atoms. Next we froze only the heavy atoms of the protein and then allowed all the hydrogen and drug atoms to move. In each case, the drugs did not really move much. This suggested that we included the most important side chains for binding the drug. These preliminary calculations were performed at the AMI level using the computational chemistry program Gaussian 03W. Estimated binding constants calculated using a more sophisticated theory will be presented.

12:30 MOLECULAR MODELING OF CARBONIC ANHYDRASE INHIBITORS **, Candice Charles Broome * and Robert W. Zurales, Middle Georgia College, Cochran, GA 31014. While the enzyme carbonic anhydrase (CA) is found throughout the body, the isoform known as CA IX is found almost exclusively in tumors. We are studying drugs that bind more tightly...

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