Scientific articles using ASH

ASH is a relatively new code but has been used for a few different research projects that led to publications. Below you can find various examples, including example ASH scripts that were used in the publications.

If you have used ASH in your research and you would like to mention it here, contact me!

MM and QM/MM protein studies

Micro-second classical dynamics simulation of an artificial Mo-Cu hydrogenase

2023 J. Am. Chem. Soc. article

This article used the OpenMM interface in ASH (ORCA interface) to set up new solvated models of the Orange protein (Orp) and to explore possible binding sites of an anionic S2MoS2CuS2MoS2 cluster to the protein. Long-time scale classical MD simulations were carried out, up to 1 microsecond (1000 nanoseconds) on a workstation with an Nvidia GPU card (platform='CUDA'). The X-ray structure of the apoprotein (PDB-ID : 2WFB) together with a DFT-optimized (r2SCAN/def2-TZVP) structure of the metal cluster was used to set up the system which was fully solvated. The metal cluster was described as a semi-rigid entity (bond constraints) with a nonbonded model (DFT-derived CM5 charges and UFF Lennard-Jones parameters). Periodic boundary conditions were used, all X-H bonds frozen and all water molecules were rigid. Before production NVT simulations, the system was minimized for 100 steps, gently heated up using 3 short NVT simulations before running an NPT simulation until volume and density became stable. Production NVT simulations at 300 K were run for up to 1 microsecond using an integration timestep of 4 fs, Langevin friction coefficient of 1 ps-1 and hydrogen mass repartioning of 1.5 amu. The simulations were found to be consistent with the anionic cluster binding to a positively charged Arg,Lys-containing pocket.

Example setup script:

from ash import *

#Original raw PDB-file (no hydrogens, nosolvent)
#XML-file to deal with cofactor
#Setting possible manual protonation states.
# Setting up system via Modeller
OpenMM_Modeller(pdbfile=pdbfile, forcefield='CHARMM36',
    extraxmlfile=extraxmlfile, watermodel="tip3p", pH=7.0, solvent_padding=10.0,
    ionicstrength=0.1, pos_iontype='Na+', neg_iontype='Cl-', residue_variants=residue_variants, use_higher_occupancy=True)

where MCM.xml is the forcefield file for the Mo2CuS8 cluster:

<Type name="MOX" class="Mo" element="Mo" mass="95.96"/>
<Type name="CUX" class="Cu" element="Cu" mass="63.546"/>
<Type name="SXB" class="S" element="S" mass="32.065"/>
<Type name="SXT" class="S" element="S" mass="32.065"/>
<Residue name="MCM">
<Atom name="MO1" type="MOX"/>
<Atom name="MO2" type="MOX"/>
<Atom name="CU1" type="CUX"/>
<Atom name="S1" type="SXT"/>
<Atom name="S2" type="SXT"/>
<Atom name="S3" type="SXB"/>
<Atom name="S4" type="SXB"/>
<Atom name="S5" type="SXB"/>
<Atom name="S6" type="SXB"/>
<Atom name="S7" type="SXT"/>
<Atom name="S8" type="SXT"/>
<NonbondedForce coulomb14scale="1.0" lj14scale="1.0">
<Atom type="MOX" charge="0.909" sigma="0.0" epsilon="0.0"/>
<Atom type="CUX" charge="0.074" sigma="0.0" epsilon="0.0"/>
<Atom type="SXT" charge="-0.691" sigma="0.0" epsilon="0.0"/>
<Atom type="SXB" charge="-0.532" sigma="0.0" epsilon="0.0"/>
<LennardJonesForce lj14scale="1.0">
<Atom type="MOX" sigma="0.2719022887764316" epsilon="0.234304"/>
<Atom type="CUX" sigma="0.3113691019900486" epsilon="0.02092"/>
<Atom type="SXT" sigma="0.3594776327696269" epsilon="1.146416"/>
<Atom type="SXB" sigma="0.3594776327696269" epsilon="1.146416"/>

Example MD script (opt,gentle heating, NPT and production NVT for 2.5 ns):

from ash import *


#Defining list of lists of bond-constraints for cluster

#PDB-file to read topology from (and also initial coordinates)

#Read coordinates from PDB-file only this time

#OpenMM object with constraints
omm = OpenMMTheory(xmlfiles=["charmm36.xml", "charmm36/water.xml", "MCM.xml"], pdbfile=pdbfile, periodic=True,
    platform='CUDA', numcores=numcores, autoconstraints='HBonds', constraints=bondconstraints, rigidwater=True)

#MM minimization for 100 steps
OpenMM_Opt(fragment=fragment, theory=omm, maxiter=100, tolerance=1)

#Gentle heating up protocol
OpenMM_MD(fragment=fragment, theory=omm, timestep=0.0005, simulation_steps=10, traj_frequency=1, temperature=1,
    integrator='LangevinMiddleIntegrator', coupling_frequency=1, trajfilename='NVTtrajectorystepA', trajectory_file_option='DCD')
OpenMM_MD(fragment=fragment, theory=omm, timestep=0.001, simulation_steps=50, traj_frequency=1, temperature=10,
    integrator='LangevinMiddleIntegrator', coupling_frequency=1, trajfilename='NVTtrajectorystepB', trajectory_file_option='DCD')
OpenMM_MD(fragment=fragment, theory=omm, timestep=0.004, simulation_steps=10000, traj_frequency=1, temperature=300,
    integrator='LangevinMiddleIntegrator', coupling_frequency=1, trajfilename='NVTtrajectorystepC', trajectory_file_option='DCD')

#NPT simulation until density and volume converges
OpenMM_box_relaxation(fragment=fragment, theory=omm, datafilename="nptsim.csv", numsteps_per_NPT=10000,
                    volume_threshold=1.0, density_threshold=0.001, temperature=300, timestep=0.004,
                    traj_frequency=100, trajfilename='relaxbox_NPT', trajectory_file_option='DCD', coupling_frequency=1)

#Classical NVT MD simulation for 2500 ps at 300 K
OpenMM_MD(fragment=fragment, theory=omm, timestep=0.004, simulation_time=2500, traj_frequency=1000, temperature=300,
    integrator='LangevinMiddleIntegrator', coupling_frequency=1, trajectory_file_option='DCD', trajfilename='NVTtrajectory')

#Re-image trajectory so that protein is in middle
MDtraj_imagetraj("NVTtrajectory.dcd", "final_MDfrag_laststep.pdb", format='DCD')

QM/MM modelling of a CN-inhibited state of FeFe hydrogenase

2023 Chem. Sci. article

This article used the QM/MM module of ASH together with the ORCA interface (ORCA interface) for the QM part and the OpenMM interface (OpenMM interface) to setup The OpenMMTheory interface used CHARMM-style forcefield files.

QM/MM modelling of dinitrogen binding to redox states of nitrogenase

2023 Inorg. Chem. article

This work, exploring dinitrogen binding to multiple redox states of the complex iron-molybdenum cofactor of nitrogenase used the QM/MM module of ASH together with the ORCA interface (ORCA interface) for the QM part and the OpenMM interface (OpenMM interface) for the MM part (CHARMM36 forcefield with CHARMM files). Broken-symmetry solutions in the QM-part were controlled by the ORCA interface (brokensym, HSmult, atomstoflip keywords, see ORCA interface).

QM/MM modelling of Cu proteins

Uncovering primary and secondary coordination sphere effects in S-nitrosylating azurin: 2023 JACS article

Highlevel WFT workflows

Multistep DLPNO-CCSD(T)/CBS workflow for a transition metal complex

2023 PCCP article

This article used ORCA_CC_CBS_Theory (Highlevel workflows) functionality in ASH. Below is a script that describes a recommended DLPNO-CCSD(T)/CBS workflow that worked well for this class of metallocenes and should be reasonably reliable in general (assuming coupled cluster is reliable). It uses a CBS(3/4) basis set extrapolation using the cc-pVnZ-DK basis set family, together with BP86 reference orbitals, DKH scalar relativistic Hamiltonian, PNO extrapolation using the cheaper approach and the cheaper T1 correction described in th article.

Example script:

from ash import *
numcores=24 #Number of cores reserved
actualcores=16 #Number of cores used
#Defining molecular fragments
cpco0=Fragment(xyzfile="", charge=0, mult=2)
cpcoI=Fragment(xyzfile="", charge=1, mult=1)
# Defining species, stoichiometry and reaction specieslist=[cpco0,cpcoI]
stoichiometry=[-1, 1]
reaction = Reaction(fragments=specieslist, stoichiometry=stoichiometry, unit='eV')
#Defining a ORCA_CC_CBS_Theory object
cc = ORCA_CC_CBS_Theory(elements=cpco0.elems, cardinals=[3,4], basisfamily="cc-dk", DFTreference="BP86",
    DLPNO=True, CVSR=False, T1correction=True, T1corrbasis_size='Small', T1corrpnosetting='NormalPNOreduced',
    numcores=actualcores, pnosetting="extrapolation", pnoextrapolation=[1e-6,3.33e-7,2.38,'NormalPNO'],
    memory=20000, scfsetting="Verytightscf", relativity='DKH', SCFextrapolation=False)
#Running reaction
Singlepoint_reaction(theory=cc, reaction=reaction)