scholarly journals Improving The Performance Of The Amber Rna Force Field By Tuning The Hydrogen-Bonding Interactions

2018 ◽  
Author(s):  
Petra Kührová ◽  
Vojtěch Mlýnský ◽  
Marie Zgarbová ◽  
Miroslav Krepl ◽  
Giovanni Bussi ◽  
...  
Keyword(s):  
Md Simulations ◽  
Rna Motifs ◽  
Conformational Ensembles ◽  
Interaction Terms ◽  
Empirical Potentials ◽  
Hydrogen Bonding Interactions ◽  
Bonding Interaction ◽  
Free Energy Landscapes ◽  
Folding Simulations ◽  
Fine Tune

ABSTRACTMolecular dynamics (MD) simulations became a leading tool for investigation of structural dynamics of nucleic acids. Despite recent efforts to improve the empirical potentials (force fields,ffs), RNAffshave persisting deficiencies, which hamper their utilization in quantitatively accurate simulations. Previous studies have shown that at least two salient problems contribute to difficulties in description of free-energy landscapes of small RNA motifs: (i) excessive stabilization of the unfolded single-stranded RNA ensemble by intramolecular base-phosphate and sugar-phosphate interactions, and (ii) destabilization of the native folded state by underestimation of stability of base pairing. Here, we introduce a generalffterm (gHBfix) that can selectively fine-tune non-bonding interaction terms in RNAffs, in particular the H-bonds. gHBfix potential affects the pair-wise interactions between all possible pairs of the specific atom types, while all other interactions remain intact, i.e., it is not a structure-based model. In order to probe the ability of the gHBfix potential to refine theffnon-bonded terms, we performed an extensive set of folding simulations of RNA tetranucleotides and tetraloops. Based on these data we propose particular gHBfix parameters to modify the AMBER RNAff. The suggested parametrization significantly improves the agreement between experimental data and the simulation conformational ensembles, although our currentffversion still remains far from being flawless. While attempts to tune the RNAffsby conventional reparametrizations of dihedral potentials or non-bonded terms can lead to major undesired side effects as we demonstrate for some recently publishedffs, gHBfix has a clear promising potential to improve theffperformance while avoiding introduction of major new imbalances.

scholarly journals Towards Convergence in Folding Simulations of RNA Tetraloops: Comparison of Enhanced Sampling Techniques and Effects of Force Field Corrections

2021 ◽  
Author(s):  
Vojtech Mlynsky ◽  
Michal Janecek ◽  
Petra Kuhrova ◽  
Thorben Frohlking ◽  
Michal Otyepka ◽  
...  
Keyword(s):  
Time Scale ◽  
Md Simulations ◽  
Sampling Techniques ◽  
Enhanced Sampling ◽  
Free Energies ◽  
Native State ◽  
Good Convergence ◽  
Empirical Potentials ◽  
Folding Simulations ◽  
Established Technique

Atomistic molecular dynamics (MD) simulations represent established technique for investigation of RNA structural dynamics. Despite continuous development, contemporary RNA simulations still suffer from suboptimal accuracy of empirical potentials (force fields, ffs) and sampling limitations. Development of efficient enhanced sampling techniques is important for two reasons. First, they allow to overcome the sampling limitations and, second, they can be used to quantify ff imbalances provided they reach a sufficient convergence. Here, we study two RNA tetraloops (TLs), namely the GAGA and UUCG motifs. We perform extensive folding simulations and calculate folding free energies (ΔGfold) with the aim to compare different enhanced sampling techniques and to test several modifications of the nonbonded terms extending the AMBER OL3 RNA ff. We demonstrate that replica exchange solute tempering (REST2) simulations with 12-16 replicas do not show any sign of convergence even when extended to time scale of 120 μs per replica. However, combination of REST2 with well-tempered metadynamics (ST-MetaD) achieves good convergence on a time-scale of 5-10 μs per replica, improving the sampling efficiency by at least two orders of magnitude. Effects of ff modifications on ΔGfold energies were initially explored by the reweighting approach and then validated by new simulations. We tested several manually-prepared variants of gHBfix potential which improve stability of the native state of both TLs by up to ~2 kcal/mol. This is sufficient to conveniently stabilize the folded GAGA TL while the UUCG TL still remains under-stabilized. Appropriate adjustment of van der Waals parameters for C-H...O5' base-phosphate interaction are also shown to be capable of further stabilizing the native states of both TLs by ~0.6 kcal/mol.

scholarly journals Conformational Ensembles by NMR and MD Simulations in Model Heptapeptides with Select Tri-Peptide Motifs

2021 ◽  
Vol 22 (3) ◽  
pp. 1364
Author(s):  
V. V. Krishnan ◽  
Timothy Bentley ◽  
Alina Xiong ◽  
Kalyani Maitra
Keyword(s):  
Principal Component ◽  
Md Simulations ◽  
Conformational Space ◽  
Random Coil ◽  
Radius Of Gyration ◽  
Small Peptides ◽  
Conformational Ensembles ◽  
Solution State ◽  
Peptide Motifs ◽  
Explicit Solvent

Both nuclear magnetic resonance (NMR) and molecular dynamics (MD) simulations are routinely used in understanding the conformational space sampled by peptides in the solution state. To investigate the role of single-residue change in the ensemble of conformations sampled by a set of heptapeptides, AEVXEVG with X = L, F, A, or G, comprehensive NMR, and MD simulations were performed. The rationale for selecting the particular model peptides is based on the high variability in the occurrence of tri-peptide E*L between the transmembrane β-barrel (TMB) than in globular proteins. The ensemble of conformations sampled by E*L was compared between the three sets of ensembles derived from NMR spectroscopy, MD simulations with explicit solvent, and the random coil conformations. In addition to the estimation of global determinants such as the radius of gyration of a large sample of structures, the ensembles were analyzed using principal component analysis (PCA). In general, the results suggest that the -EVL- peptide indeed adopts a conformational preference that is distinctly different not only from a random distribution but also from other peptides studied here. The relatively straightforward approach presented herein could help understand the conformational preferences of small peptides in the solution state.

scholarly journals Markov models for the elucidation of allosteric regulation

2018 ◽  
Vol 373 (1749) ◽  
pp. 20170178 ◽  
Author(s):  
Ushnish Sengupta ◽  
Birgit Strodel
Keyword(s):  
Markov Models ◽  
Allosteric Regulation ◽  
Md Simulations ◽  
Markov Modelling ◽  
Conformational Ensembles ◽  
Markov State ◽  
Protein Allostery ◽  
Markov State Models ◽  
State Models ◽  
Allosteric Mechanisms

Allosteric regulation refers to the process where the effect of binding of a ligand at one site of a protein is transmitted to another, often distant, functional site. In recent years, it has been demonstrated that allosteric mechanisms can be understood by the conformational ensembles of a protein. Molecular dynamics (MD) simulations are often used for the study of protein allostery as they provide an atomistic view of the dynamics of a protein. However, given the wealth of detailed information hidden in MD data, one has to apply a method that allows extraction of the conformational ensembles underlying allosteric regulation from these data. Markov state models are one of the most promising methods for this purpose. We provide a short introduction to the theory of Markov state models and review their application to various examples of protein allostery studied by MD simulations. We also include a discussion of studies where Markov modelling has been employed to analyse experimental data on allosteric regulation. We conclude our review by advertising the wider application of Markov state models to elucidate allosteric mechanisms, especially since in recent years it has become straightforward to construct such models thanks to software programs like PyEMMA and MSMBuilder. This article is part of a discussion meeting issue ‘Allostery and molecular machines’.

scholarly journals Simulating Absorption Spectra of Flavonoids in Aqueous Solution: A Polarizable QM/MM Study

Molecules ◽  
2020 ◽  
Vol 25 (24) ◽  
pp. 5853
Author(s):  
Sulejman Skoko ◽  
Matteo Ambrosetti ◽  
Tommaso Giovannini ◽  
Chiara Cappelli
Keyword(s):  
Molecular Dynamics ◽  
Aqueous Solution ◽  
Hydrogen Bonding ◽  
Force Field ◽  
Absorption Spectra ◽  
Computational Study ◽  
Md Simulations ◽  
Quantum Mechanical ◽  
Hydrogen Bonding Interactions

We present a detailed computational study of the UV/Vis spectra of four relevant flavonoids in aqueous solution, namely luteolin, kaempferol, quercetin, and myricetin. The absorption spectra are simulated by exploiting a fully polarizable quantum mechanical (QM)/molecular mechanics (MM) model, based on the fluctuating charge (FQ) force field. Such a model is coupled with configurational sampling obtained by performing classical molecular dynamics (MD) simulations. The calculated QM/FQ spectra are compared with the experiments. We show that an accurate reproduction of the UV/Vis spectra of the selected flavonoids can be obtained by appropriately taking into account the role of configurational sampling, polarization, and hydrogen bonding interactions.

scholarly journals Structure and Dynamics of Glycosphingolipids in Lipid Bilayers: Insights from Molecular Dynamics Simulations

2011 ◽  
Vol 2011 ◽  
pp. 1-9 ◽  
Author(s):  
Ronak Y. Patel ◽  
Petety V. Balaji
Keyword(s):  
Molecular Dynamics ◽  
Lipid Bilayers ◽  
Membrane Structure ◽  
Lipid Membrane ◽  
Biological Membranes ◽  
Md Simulations ◽  
Atomic Level ◽  
Structure And Dynamics ◽  
Hydrogen Bonding Interactions ◽  
Dynamics Simulations

Glycolipids are important constituents of biological membranes, and understanding their structure and dynamics in lipid bilayers provides insights into their physiological and pathological roles. Experimental techniques have provided details into their behavior at model and biological membranes; however, computer simulations are needed to gain atomic level insights. This paper summarizes the insights obtained from MD simulations into the conformational and orientational dynamics of glycosphingolipids and their exposure, hydration, and hydrogen-bonding interactions in membrane environment. The organization of glycosphingolipids in raft-like membranes and their modulation of lipid membrane structure are also reviewed.

THEORETICAL STUDY ON INTERACTION BETWEEN IONIC LIQUIDS AND AROMATIC SULFUR COMPOUNDS

2011 ◽  
Vol 10 (01) ◽  
pp. 31-40 ◽  
Author(s):  
YI NIE ◽  
XIANGAI YUAN
Keyword(s):  
Hydrogen Bonding ◽  
Ionic Liquids ◽  
Density Functional ◽  
Sulfur Compound ◽  
Ion Pairs ◽  
Benzene Molecule ◽  
Sulfur Compounds ◽  
Functional Theory ◽  
Hydrogen Bonding Interactions ◽  
Bonding Interaction

It is important to understand how ionic liquids interact with aromatic sulfur compounds in view of ionic liquids application in desulfurization from fuels. Ion pairs of N, N-dialkylimidazolium dialkylphosphate ionic liquids were optimized at the Becke3LYP level of density functional theory. The most stable geometries were obtained. The stable ion pairs indicate there exist hydrogen bonding interactions between them. The calculated interaction energies of ion pairs were found to increase in magnitude with decreasing alkyl chain length, and with decreasing anionic radius. Furthermore, the interactions between the IL and aromatic sulfur compound, and benzene molecule were investigated. The results indicate that there exist hydrogen bonds between them. The calculated interaction energy between IL and sulfur compound is larger than that between IL and benzene. The aromatic ring π - π interaction and hydrogen bonding interaction may be the dominant factors to influence the trend of interaction between ILs and aromatic sulfur compounds.

scholarly journals Determination of Protein Structural Ensembles by Hybrid-Resolution SAXS Restrained Molecular Dynamics.

2019 ◽  
Author(s):  
Cristina Paissoni ◽  
Alexander Jussupow ◽  
Carlo Camilloni
Keyword(s):  
Dynamical Behavior ◽  
Computational Cost ◽  
Three Dimensional ◽  
Md Simulations ◽  
Coarse Grained ◽  
Conformational Ensemble ◽  
Biomolecular Systems ◽  
Conformational Ensembles ◽  
Independent Experimental Data

<div><div><div><p>SAXS experiments provide low-resolution but valuable information about the dynamics of biomolecular systems, which could be ideally integrated in MD simulations to accurately determine conformational ensembles of flexible proteins. The applicability of this strategy is hampered by the high computational cost required to calculate scattering intensities from three-dimensional structures. We previously presented a metainference-based hybrid resolution method that makes atomistic SAXS-restrained MD simulation feasible by adopting a coarse-grained approach to efficiently back-calculate scattering intensities; here, we extend this technique, applying it in the framework of multiple-replica simulations with the aim to investigate the dynamical behavior of flexible biomolecules. The efficacy of the method is assessed on the K63-diubiquitin multi-domain protein, showing that inclusion of SAXS-restraints is effective in generating reliable and heterogenous conformational ensemble, also improving the agreement with independent experimental data.</p></div></div></div>

scholarly journals Energy Penalties Enhance Flexible Receptor Docking in a Model Cavity

2021 ◽  
Author(s):  
Anna Sophia Kamenik ◽  
Isha Singh ◽  
Parnian Lak ◽  
Trent E Balius ◽  
Klaus R Liedl ◽  
...  
Keyword(s):  
Protein Flexibility ◽  
Md Simulations ◽  
High Energy ◽  
General Applicability ◽  
Penalty Term ◽  
Conformational Ensembles ◽  
X Ray Crystallography ◽  
Conformational Preferences ◽  
Energy Penalty ◽  
Cavity Opening

Protein flexibility remains a major challenge in library docking due to difficulties in sampling conformational ensembles with accurate probabilities. Here we use the model cavity site of T4 Lysozyme L99A to test flexible receptor docking with energy penalties from molecular dynamics (MD) simulations. Crystallography with larger and smaller ligands indicates that this cavity can adopt three major conformations, open, intermediate, and closed. Since smaller ligands typically bind better to the cavity site, we anticipate an energy penalty for cavity opening. To estimate its magnitude, we calculate conformational preferences from MD simulations. We find that including a penalty term is essential for retrospective ligand enrichment, otherwise high-energy states dominate the docking. We then prospectively docked a library of over 900,000 compounds for new molecules binding to each conformational state. Absent a penalty term, the open conformation dominated the docking results; inclusion of this term led to a balanced sampling of ligands against each state. High ranked molecules were experimentally tested by Tm-upshift and X-ray crystallography. From 33 selected molecules, we identified 18 new ligands and determined 13 crystal structures. Most interesting were those bound to the open cavity, where the buried site opens to bulk solvent. Here, highly unusual ligands for this cavity had been predicted, including large ligands with polar tails; these were confirmed both by binding and by crystallography. In docking, incorporating protein flexibility with thermodynamic weightings may thus access new ligand chemotypes. The MD approach to accessing and, crucially, weighting such alternative states may find general applicability.

scholarly journals Extra hydrogen bonding interactions by peripheral indole groups stabilize benzene-1,3,5-tricarboxamide helical assemblies

2019 ◽  
Vol 55 (59) ◽  
pp. 8548-8551
Author(s):  
Gaëtan Basuyaux ◽  
Alaric Desmarchelier ◽  
Geoffrey Gontard ◽  
Nicolas Vanthuyne ◽  
Jamal Moussa ◽  
...  
Keyword(s):  
Hydrogen Bonding ◽  
Hydrogen Bonding Interaction ◽  
Hydrogen Bonding Interactions ◽  
Bonding Interaction ◽  
Additional Hydrogen

The indole groups (Ind) of these BTA monomers provide an additional hydrogen bonding interaction that enables the formation of remarkably stable supramolecular helices.

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