Volume 140, Issue 11, 21 March 2014
Index of content:
Interfacial systems are at the core of fascinating phenomena in many disciplines, such as biochemistry, soft-matter physics, and food science. However, the parametrization of accurate, reliable, and consistent coarse-grained (CG) models for systems at interfaces remains a challenging endeavor. In the present work, we explore to what extent two independently developed solvent-free CG models of peptides and lipids—of different mapping schemes, parametrization methods, target functions, and validation criteria—can be combined by only tuning the cross-interactions. Our results show that the cross-parametrization can reproduce a number of structural properties of membrane peptides (for example, tilt and hydrophobic mismatch), in agreement with existing peptide-lipid CG force fields. We find encouraging results for two challenging biophysical problems: (i) membrane pore formation mediated by the cooperative action of several antimicrobial peptides, and (ii) the insertion and folding of the helix-forming peptide WALP23 in the membrane.
140(2014); http://dx.doi.org/10.1063/1.4869329View Description Hide Description
Photosynthetic units perform energy transfer remarkably well under a diverse range of demanding conditions. However, the mechanism of energy transfer, from excitation to conversion, is still not fully understood. Of particular interest is the possible role that coherence plays in this process. In this perspective, we overview photosynthetic light harvesting and discuss consequences of excitons for energy transfer and how delocalization can be assessed. We focus on challenges such as decoherence and nuclear-coordinate dependent delocalization. These approaches complement conventional spectroscopy and delocalization measurement techniques. New broadband transient absorption data may help uncover the difference between electronic and vibrational coherences present in two-dimensional electronic spectroscopy data. We describe how multipartite entanglement from quantum information theory allows us to formulate measures that elucidate the delocalization length of excitation and the details of that delocalization even from highly averaged information such as the density matrix.