Biology subjects

V. Guzman, H.

Publications and source records attributed to V. Guzman, H..

4 recordsLinked to original sources

bioRxiv2026

Topological Closure Drives Structural Stabilization and Fast Cooperative Dynamics in Crowded Circular Polysomes

In linear polysomes, excluded-volume interactions among ribosomes can induce dimensional reduction of mRNA. Yet linear architectures allow steric stress to relax at open ends-- limiting how strongly crowding can remodel the mRNA's structure and dynamics. Using coarse-grained molecular-dynamics simulations, we compare circular and linear polysomes over a range of ribosome densities. Circular closure selects a predominantly quasi-planar global conformational ensemble, as indicated by a shape dimensionality dshape {approx} 2 over a range of ribosome densities. Crucially, circular topology and ribosome crowding act cooperatively to suppress structural fluctuations. While closure alone or linear crowding reduces relative global size fluctuations ({Delta}Rg/Rg) only to {approx} 0.16, their combined effect drives this fluctuation down to {approx} 0.07. Within this stabilized architecture, increasing ribosome density drives a distinct in-plane reorganization: the ring becomes more isotropic, global size fluctuations are strongly suppressed, and the scaling exponent increases toward {nu} [~=] 0.74 - 0.77, consistent with two-dimensional self-avoiding walk-like value over the accessible finite-size window, 1000 [≤] N [≤] 4969. Closure shortens the radius-of-gyration decorrelation time of circular polysomes by 40-fold relative to matched linear systems, reflecting the topological elimination of free ends. Within this closureselected ensemble, ribosome crowding further reduces the decorrelation time by up to 20% at the highest density. A fluctuation-informed crossover model links the density dependence of the global scaling exponent to inter-ribosomal subchain statistics. These results distinguish the geometric role of circular closure from the density-dependent steric response that it enables, revealing a confined yet dynamically responsive conformational regime for circular polysomes.

biophysics↗

bioRxiv2024

Adsorption-driven deformation and landing-footprints of the RBD proteins in SARS-CoV-2 variants onto biological and inanimate surfaces

Respiratory viruses, carried through airborne microdroplets, frequently adhere to surfaces, including plastics and metals. However, our understanding of the interactions between viruses and materials remains limited, particularly in scenarios involving polarizable surfaces. Here, we investigate the role of receptor-binding domain (RBD) mutations on the adsorption of SARS-CoV-2 to hydrophobic and hydrophilic surfaces employing molecular simulations. To contextualize our findings, we contrast the interactions on inanimate surfaces with those on native-biological interfaces, specifically the ACE2 receptor. Notably, we identify a twofold increase in structural deformations for the proteins receptor binding motif onto the inanimate surfaces, indicative of enhanced shock-absorbing mechanisms. Furthermore, the distribution of amino acids (landing-footprints) on the inanimate surface reveals a distinct regional asymmetry relative to the biological interface. In spite of the H-bonds formed at the hydrophilic substrate, the simulations consistently show a higher number of contacts and interfacial area with the hydrophobic surface, with the WT RBD adsorbed more strongly than the delta or omicron RBDs. In contrast, the adsorption of delta and omicron to hydrophilic surfaces was characterized by a distinctive hopping-pattern. The novel shock-absorbing mechanisms identified in the virus adsorption on inanimate surfaces could lead current experimental efforts in the design of virucidal surfaces.

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↗

bioRxiv2021

RNA secondary structure regulates fragments' adsorption onto flat substrates

RNA is a functionally rich molecule with multilevel, hierarchical structures whose role in the adsorption to molecular substrates is only beginning to be elucidated. Here, we introduce a multiscale simulation approach that combines a tractable coarse-grained RNA structural model with an interaction potential of a structureless flat adsorbing substrate. Within this approach, we study the specific role of stem-hairpin and multibranch RNA secondary structure motifs on its adsorption phenomenology. Our findings identify a dual regime of adsorption for short RNA fragments with and without secondary structure, and underline the adsorption efficiency in both cases as a function of the surface interaction strength. The observed behavior results from an interplay between the number of contacts formed at the surface and the conformational entropy of the RNA molecule. The adsorption phenomenology of RNA seems to persist also for much longer RNAs as qualitatively observed by comparing the trends of our simulations with a theoretical approach based on an ideal semiflexible polymer chain.

biophysics↗