Biology Project Abstract
ANTIMICROBIAL PEPTIDE PC-17 INSERTION INTO LIPID MONOLAYERS
Presenter:
Madeleine M. Walsh, Illinois Mathematics and Science Academy, 1500 West Sullivan Road, Aurora, IL, 60506; mwalsh@imsa.edu
Mentors:
Mr. Yuji Ishitsuka, The University of Chicago, 5735 S. Ellis Avenue, Chicago, IL, 60637; 773-834-2793; yuji@uchicago.edu
Dr. Ka Yee C. Lee, The University of Chicago, Dept. of Chemistry,5735 S. Ellis Avenue, Chicago, IL, 60637; 773-702 7068; kayeelee@uchicago.edu
Abstract:
PC-17 is a modification of the antimicrobial peptide protegrin-1 (PG-1), which is isolated from porcine leukocytes. Previous studies have shown that PG-1 interaction with cellular membranes is dependent upon the composition of the membrane, and the results of this study suggest that the same would be true of PC-17. In this study, Langmuir monolayers are used to mimic the outer membranes of bacterial and mammalian cells. The insertion of PC-17 into these monolayers at varying surface pressures has been observed by measuring the degree of insertion of the peptide into the monolayer and also through fluorescence microscopy images. PC-17 showed relatively high levels of insertion into monolayers composed of lipids present in bacterial membranes [dipalmitoylphosphatidylglycerol (DPPG) and lipid A] and low levels of insertion into monolayers composed of lipids present in mammalian cell membranes [dipalmitoylphosphatidylcholine (DPPC)] at surface pressures varying between 25 mN/m and 35 mN/m. Fluorescence microscopy indicated significant disordering of membrane packing in the DPPG membranes after the insertion of the peptide, but little or no difference in membrane morphology for DPPC after insertion. DPPG and lipid A are major components of the outer membranes of Gram positive and negative bacterial cells, respectively, while DPPC is a component of mammalian red blood cell membranes.