Investigations on the role of CH O interactions and its impact on stability and specificity of penicillin binding proteins.

Penicillin binding proteins are recognized as important antibacterial targets because of their crucial role in the cell wall synthesis of bacteria. Alteration in the binding site of penicillin binding proteins is one of the major problems for beta lactam antibiotics to exert its effect. In the present study the influence of CH…O interactions in the conformational stability of penicillin binding proteins were analyzed in both Gram positive and Gram negative bacteria. CH…O interactions constitute about 20 to 25% of total hydrogen bonds and act as an important driving force in ligand selectivity. From our analysis we observed a total of 13,398 CH…O interactions in Gram positive bacteria and 10,855 CH…O interactions in Gram negative bacteria. It was interesting to observe that CH…O interactions were higher in Gram positive bacteria than in Gram negative bacteria, which augurs well for the discrepancy in cell wall of the bacteria. CH…O interactions are classified into four types depending on the interaction of acceptor residues with the back bone or side chain of CH groups. From our results we observed that major contribution to penicillin binding proteins was observed from side chain atoms of donor residues and back bone atoms of acceptor residues [SM CH…O] in both Gram positive and Gram negative bacteria. Conformational preference of Gram positive bacteria indicated that amino acids lacking side chain and the cyclized amino acids preferred to be in turn regions, whereas aromatic amino acids dominated in Gram negative bacteria. Our analysis gives detailed information about the principles involved in the conformational stability of penicillin binding proteins and the results will be useful for researchers exploring penicillin binding proteins.

Duodenal diverticulum and associated pancreatitis: case report with brief review of literature.

Pancreatitis in the elderly is a problem of increasing occurrence and is associated with severe complications. Periampullary diverticula (PAD) are extraluminal outpouchings of the duodenum rarely associated with pancreatitis. The presence of PAD should be excluded before diagnosing idiopathic pancreatitis, particularly in the elderly. However, when a duodenal diverticulum is found in the absence of any additional pathology, only then should the symptoms be attributed to the diverticulum. We describe a case of duodenal diverticulum presenting with pancreatitis to emphasize the importance of this commonly neglected etiology.