How to Assign AMBER Parameters to Desmond-generated System with viparr4 v1

2021 ◽  
Author(s):  
Thilo Mast ◽  
Dmitry Lupyan
Keyword(s):  
Molecular Dynamics ◽  
Molecular Dynamics Simulations ◽  
Force Fields ◽  
Third Party ◽  
Ligand Complex ◽  
Software Suite ◽  
Dynamics Simulations

This tutorial partially copies steps from How to Assign CHARMM Parameters to Desmond-generated System with viparr4 but differs in the parametrization steps. You can use the Schrödinger software suite to prepare systems for molecular dynamics simulations, however, only the OPLS _2005 and OPLS4 force fields can be automatically assigned. This tutorial will show you how to use Desmond with third-party force fields like AMBER, using the Viparr utility from D.E. Shaw Research. You will prepare a protein-ligand complex, generate custom AMBER parameters for the ligand, and use the Viparr utility to convert the generated AMBER parameters into a viparr-formatted template, that can be used for simulations. You can find the input files for this tutorial here:

scholarly journals Ethidium bromide interactions with DNA: an exploration of a classic DNA–ligand complex with unbiased molecular dynamics simulations

2021 ◽  
Vol 49 (7) ◽  
pp. 3735-3747
Author(s):  
Rodrigo Galindo-Murillo ◽  
Thomas E Cheatham
Keyword(s):  
Molecular Dynamics ◽  
Molecular Dynamics Simulations ◽  
Ethidium Bromide ◽  
Base Pair ◽  
Force Fields ◽  
Ligand Complex ◽  
Base Pairs ◽  
Duplex System ◽  
Double Stranded Dna ◽  
Dynamics Simulations

Abstract Visualization of double stranded DNA in gels with the binding of the fluorescent dye ethidium bromide has been a basic experimental technique in any molecular biology laboratory for >40 years. The interaction between ethidium and double stranded DNA has been observed to be an intercalation between base pairs with strong experimental evidence. This presents a unique opportunity for computational chemistry and biomolecular simulation techniques to benchmark and assess their models in order to see if the theory can reproduce experiments and ultimately provide new insights. We present molecular dynamics simulations of the interaction of ethidium with two different double stranded DNA models. The first model system is the classic sequence d(CGCGAATTCGCG)2 also known as the Drew–Dickerson dodecamer. We found that the ethidium ligand binds mainly stacked on, or intercalated between, the terminal base pairs of the DNA with little to no interaction with the inner base pairs. As the intercalation at the terminal CpG steps is relatively rapid, the resultant DNA unwinding, rigidification, and increased stability of the internal base pair steps inhibits further intercalation. In order to reduce these interactions and to provide a larger groove space, a second 18-mer DNA duplex system with the sequence d(GCATGAACGAACGAACGC) was tested. We computed molecular dynamics simulations for 20 independent replicas with this sequence, each with ∼27 μs of sampling time. Results show several spontaneous intercalation and base-pair eversion events that are consistent with experimental observations. The present work suggests that extended MD simulations with modern DNA force fields and optimized simulation codes are allowing the ability to reproduce unbiased intercalation events that we were not able to previously reach due to limits in computing power and the lack of extensively tested force fields and analysis tools.

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