Free Energies of the Disassembly of Viral Capsids from a Multiscale Molecular Simulation Approach.

Molecular simulations of large biological systems, such as viral capsids, remains a challenging task in soft matter research. On one hand, coarse-grained (CG) models attempt to make the description of the entire viral capsid disassembly feasible. On the other hand, the permanent development of novel molecular dynamics (MD) simulation approaches, like enhanced sampling methods, attempt to overcome the large time scales required for such simulations. Those methods have a potential for delivering molecular structures and properties of biological systems. Nonetheless, exploring the process on how a viral capsid disassembles by all-atom MD simulations has been rarely attempted. Here, we propose a methodology to analyze the disassembly process of viral capsids from a free energy perspective, through an efficient combination of dynamics using coarse-grained models and Poisson-Boltzmann simulations. In particular, we look at the effect of pH and charge of the genetic material inside the capsid, and compute the free energy of a disassembly trajectory precalculated using CG simulations with the SIRAH force field. We used our multiscale approach on the Triatoma virus (TrV) as a test case, and find that even though an alkaline environment enhances the stability of the capsid, the resulting deprotonation of the genetic material generates a Coulomb-type electrostatic repulsion that triggers disassembly.

Phylogenetics based on partial ORF2 of triatoma virus in triatomines collected over a decade from domiciliary habitats.

The only virus sequenced and studied in triatomines is the Triatoma virus, from the Dicistroviridae family, which causes delayed development, reduced oviposition, and premature death of infected insects. With the goal of expanding the sequences already obtained in previous years and verifying if any changes occurred in their genomic sequences, 68 samples of triatomines from several provinces of Argentina were analyzed. Sixteen positive samples were obtained by Reverse Transcription (RT)-polymerase chain reaction using the VP3-VP1 subregion of open reading frame-2 as a diagnostic method; after sequencing, 11 samples were obtained from Triatoma infestans. These new sequences showed no significant differences in the analyzed regions, which were not grouped by species or habitat or geographical distribution. There were no differences when compared with the sequences found during 2002-2012, all obtained from the wild. We conclude that despite being an RNA virus, the different sequences show high homology.