Biology subjects

Assenza, S.

Publications and source records attributed to Assenza, S..

4 recordsLinked to original sources

bioRxiv2023

Systematic comparison of Amber force fields for the mechanical properties of double-stranded DNA

AbstractThe response of double-stranded DNA to external mechanical stress plays a central role in its interactions with the protein machinery in the cell. Modern atomistic force fields have been shown to provide highly-accurate predictions for the fine structural features of the duplex. In contrast, and despite their pivotal function, less attention has been devoted to the accuracy in the prediction of the elastic parameters. Several reports have addressed the flexibility of double-stranded DNA via all-atom molecular dynamics, yet the collected information is insufficient to have a clear understanding of the relative performance of the various force fields. In this work, we fill this gap by performing a systematic study in which several systems, characterized by different sequence contexts, are simulated with the most up-to-date force fields, bcs1 and OL15, in the presence of external forces with increasing magnitude. Analysis of our results, together with their comparison with previous work focused on bsc0, allows us to unveil the differences in the predicted rigidity between the newest force fields, and suggests a road map to test their performance against experiments.

biophysics↗

bioRxiv2023

RNA multiscale simulations as an interplay of electrostatic, mechanical properties, and structures inside viruses

Multiscale simulations have broadened our understanding of RNA structure and function. Various methodologies have enabled the quantification of electrostatic and mechanical interactions of RNA at the nanometer scale. Atom-by-atom simulations, coarse-grained strategies, and continuum models of RNA and its environment provide physical insight and allow to interpret diverse experiments in a systematic way. In this chapter, we present and discuss recent advances in a set of methods to study nucleic acids at different scales. In particular, we introduce details of their parameterization, recent applications, and current limitations. We discuss the interaction of the proteinacous virus capsid, RNA with substrates, compare the properties of RNA and DNA and their interaction with the environment, and analyze the application of these methods to reconstruct the structure of the virus genome structure. Finally, the last lines are dedicated to future developments and challenges ahead.

biophysics↗

bioRxiv2022

A novel fluorescent multi-domain protein construct reveals the individual steps of the unfoldase action of Hsp70

A detailed understanding of the mechanism by which Hsp70 chaperones protect cells against protein aggregation is hampered by the detailed characterization of the aggregates, which are typically heterogeneous. To tackle this problem, we designed here a reporter chaperone substrate, MLucV, composed of a stress-labile luciferase core, flanked by stress-resistant fluorescent mTFP and Venus domains, which upon denaturation formed a discrete stable population of small aggregates. Combining Forster Resonance Energy Transfer and enzymatic activity measurements provided unprecedent details on MLucV states, including native, aggregated, unfolded and chaperone-bound conformations. Using MLucV, we probed the various steps undertaken by bacterial Hsp70 to convert stable discrete aggregates into native proteins. The mechanism first involved an ATP-fuelled disaggregation and unfolding step of the stable pre-aggregated substrate, with a consequent stretching of MLucV beyond simply-unfolded conformations, followed, upon release, by native refolding. Furthermore, the ATP-fuelled unfolding action of Hsp70 on MLucV aggregates could accumulate native MLucV species under elevated denaturing temperatures, highly adverse to the native state. These results unambiguously excluded binding and preventing aggregation from the non-equilibirum mechanism by which Hsp70 converts stable aggregates into metastable native proteins.

molecular biology↗

bioRxiv2021

Accurate sequence-dependent coarse-grained model for conformational and elastic properties of double-stranded DNA

We introduce MADna, a sequence-dependent coarse-grained model of double-stranded DNA (dsDNA), where each nucleotide is described by three beads localized at the sugar and base moieties, and at the phosphate group. The sequence dependence is included by considering a step-dependent parameterization of the bonded interactions, which are tuned in order to reproduce the values of key observables obtained from exhaustive atomistic simulations from literature. The predictions of the model are benchmarked against an independent set of all-atom simulations, showing that it captures with high fidelity the sequence dependence of conformational and elastic features beyond the single step considered in its formulation. A remarkably good agreement with experiments is found for both sequence-averaged and sequence-dependent conformational and elastic features, including the stretching and torsion moduli, the twist-stretch and twist-bend couplings, the persistence length and the helical pitch. Overall, for the inspected quantities, the model has a precision comparable to atomistic simulations, hence providing a reliable coarse-grained description for the rationalization of singlemolecule experiments and the study of cellular processes involving dsDNA. Owing to the simplicity of its formulation, MADna can be straightforwardly included in common simulation engines.

biophysics↗