McGavin ‘12 Studying Destructive Protein Piscidin

Jason McGavin '12
Jason McGavin '12
Jason McGavin ’12 observes the organic balls that seem to be bleeding dye into the surrounding liquid. But what caused the destruction? In this microscopic game of Space Invaders, it is the destructive entity that is the aggressor: piscidins, a type of bacteria-killing protein found in fish. McGavin is looking at two specific piscidins and attempting to relate their destructive function to their chemical structure.

McGavin’s advisor, Associate Professor of Chemistry Myriam Cotten, has been studying piscidins for many years, learning about their behaviors and composition. Like any another peptide, piscidins are just short proteins, containing only 22 amino acids instead of 200-300. Electronic properties of the peptide enable the peptide to rupture the cell it is attacking by interacting with the membrane of the cell. Besides lysing (or popping) the cell membranes of bacteria, its most common target, certain types of piscidins can also kill red blood cells. The rise of antibiotic resistance is a major concern in modern medicine, so research into new areas and methods of combating bacteria is a hot topic in scientific research. Studies that determine how piscidins’ function is related to their structure could lead to novel ideas about how bacteria cells can be killed.

McGavin is conducting the first dye leakage study at Hamilton. To determine the conditions under which his specific piscidins work best, McGavin is manipulating the pH and correlating it to the lysing rate. He places the peptide in varying ratios to dye-filled vesicles, balls made of cell building blocks called phospholipid. The ratios range from one peptide to one vesicle up to one peptide to 256 vesicles. The percent leakage of the sample in comparison to a positive control indicates how the effectivity changes depending on the conditions on the plate, showing McGavin the conditions in which the piscidins function best. One of the conditions that he manipulates is the composition of the vesicles: “Phospholipids have head groups, and what is on the head group can vary electronically and structurally,” McGavin explained. The piscidins’ effectiveness, which depends on the composition of the vesicle, reflects their behavior in a natural setting where vesicles are replaced by bacteria or other cells.

In addition to the dye leakage studies McGavin will also be placing samples in bicelles, a type of lipid environment that better mimics physiological environments and allows membrane proteins to be in conditions that permit them to act more like they do in typical biological settings. He will then test the bicelles with nuclear magnetic resonance (NMR) to see how the addition of piscidins to the bicelles changes the signal in comparison to the control bicelles that lack the piscidins. In the end, McGavin will hopefully better understand the conditions under which the piscidins work best, enabling him to relate their unique function to their structure. “We are looking to build up a larger base of knowledge about piscidins and discover more specific knowledge on the peptide and its interactions,” McGavin said.

When he is not in the lab, McGavin is an avid climber, works at the climbing wall, and is a member of the Delta Phi fraternity. He is a member of the Hamilton Outing Club and is a leader for Adirondack Adventure. A premed chemistry major with a minor in philosophy, McGavin will be spending the fall semester in Denmark.

McGavin attended Liberty High School in Bethlehem, Pa.

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