Surface activity of amphiphilic helical beta-peptides from molecular dynamics simulation.
The surface activity of beta-peptides is investigated using molecular simulations. The type and display of hydrophobic and hydrophilic groups on helical beta-peptides is varied systematically. Peptides with 2/3 hydrophobic groups are found to be surface active, and to adopt an orientation parallel to the air-water interface. For select beta-peptides, we also determine the potential of mean force required to bring a peptide to the air-water interface. Facially amphiphilic helices with 2/3 hydrophobic groups are found to exhibit the lowest free energy of adsorption. The adsorption process is driven by a favorable energetic term and opposed by negative entropic changes. The temperature dependence of adsorption is also investigated; facially amphiphilic helices are found to adopt orientations that are largely independent of temperature, while nonfacially amphiphilic helices sample a broader range of interfacial orientations at elevated temperatures. The thermodynamics of adsorption of beta-peptides is compared to that of 1-octanol, a well-known surfactant, and ovispirin, a naturally occurring antimicrobial peptide. It is found that the essential difference lies in the sign of the entropy of adsorption, which is negative for beta- and alpha-peptides and positive for traditional surfactants such as octanol.
Department of Chemical and Biological Engineering, University of Wisconsin-Madison, Madison, Wisconsin 53706-1691, USA.
Clark A
CA
Miller
Nicholas L
NL
Abbott
Juan J
JJ
de Pablo
D020003:1-Octanol / Q000737:chemistry; D000327:Adsorption; D000388:Air; D023181:Antimicrobial Cationic Peptides / Q000737:chemistry; D003198:Computer Simulation; D015233:Models, Statistical; D000442:Octanols / Q000737:chemistry; D010455:Peptides / Q000737:chemistry*; D011336:Probability; D013499:Surface Properties; D013501:Surface-Active Agents; D013696:Temperature; D013816:Thermodynamics; D014867:Water / Q000737:chemistry
D023181:Antimicrobial Cationic Peptides; D000442:Octanols; D010455:Peptides; D013501:Surface-Active Agents; C440189:ovispirin; D014867:Water; D020003:1-Octanol