(616f) The Effect of Interactions with Silica Surface On the Conformation of Antimicrobial Peptide Cecropin P1 Using Molecular Dynamics Simulation
AIChE Annual Meeting
2009
2009 Annual Meeting
Engineering Sciences and Fundamentals
Interfacial Phenomena in Pharmaceutics
Thursday, November 12, 2009 - 5:00pm to 5:20pm
Cecropin P1 is a 31 amino acid peptide found in nematodes from the stomachs of pigs which exhibits antimicrobial activity predominantly against Gram-negative bacteria (with reduced activity against Gram-positive bacteria) through pore formation in cell membrane as a result of its alpha helical structure. An analog of Cecropin P1, known as Cecropin P1 C, where a cysteine residue is attached at the C terminal, is also selected as a model peptide because of a cysteine residue is necessary for the peptides to be attached on a solid surface. It is of interest to relate the loss of antimicrobial activity (if any) as a result of attachment of these peptides to a surface to the conformational changes.
A Molecular Dynamics simulation was performed using AMBER to calculate the secondary structure, potential energy and end-to-end distance for Cecropin P1 and Cecropin P1 C in solution as well as for Cecropin P1 C physically adsorbed onto silica surface or anchored to the surface with a linker molecule. The simulation results showed an equilibrium structure consisting of two α helix regions for Cecropin P1 as well as for Cecropin P1 C with a sharp bend for the latter. Eventhough this could not be compared with NMR structure, the prediction of two α helical regions is consistent with the available structures of other antimicrobial peptides. % α helix of the equilibrium structure is highest (40%) for Cecropin P1 in the presence of 0.12M salt as a result of shielding of electrostatic interactions, followed by Cecropin P1 C (30%) and Cecropin P1 (25%). The conformation of adsorbed Cecropin P1 C on silica surface indicated a α helix content of around 10% as opposed to a value of around 30% in solution. In addition, the adsorbed Cecropin P1 C on silica surface does not exhibit a hairpin bend with the end to end distance being around 4 nm compared to a value of 1.5 to 2 nm in solution. The α helix content and end to end distance of Cecropin P1 C anchored to the silica surface with oligo ethylene oxide spacer molecule were found to be significantly different from those for adsorbed polypeptide.