Reactive molecular dynamics simulations of oxygen species in a liquid water layer of interest for plasma medicine
Evidence and attribution¶
Authority of statements
Prose below summarizes the publication identified by doi, title, and pdf_path. The wiki slug prefix 2013al- is a corpus artifact; metadata matches Yusupov et al. J. Phys. D (2014 PDF filename).
Summary¶
Reactive MD investigates O, OH, HO₂, and H₂O₂ interacting with a liquid water film as a model of biomolecule surface layers in plasma medicine. The abstract reports OH, HO₂, and H₂O₂ can penetrate deeply into the water layer; O, OH, and HO₂ undergo H-abstraction from water, while H₂O₂ does not in their observations—framed as transport and reaction constraints for ROS reaching cells. The J. Phys. D study is explicit that liquid water slab geometry is a deliberate simplification of plasma–liquid coupling intended to isolate downstream ROS fates after species enter a condensed phase.
Methods¶
Potential: ReaxFF C/H/O/N glycine/water parameters (Rahaman et al.). Water slab: 500 H2O in 25 x 25 x 23.93 A (1 g/cm^3); NVT equilibration 500 ps at 300 K (Bussi thermostat, 100 fs coupling); expand to 25 x 25 x 80 A and relax interfaces 100 ps. Production: Delta t = 0.25 fs; Bussi thermostat; z drift restrained (dummy atom vs water COM, Figure 1). ROS impacts: species placed >=10 A above the slab with thermal velocities at 300 K; O trajectories >=1.4 ns in examples cited. Like-species ROS bundles: z ~ 55 A, >=7 A separation, 100 ps runs, five replicas each.
Figure-linked protocols in papers/Yusupov_JPhysD_plasma_medicine_2014.pdf document initial ROS placement, replica counts, and analysis windows used to classify penetration versus surface scavenging for each species.
Force-field training¶
N/A — applies the published ReaxFF C/H/O/N (Rahaman et al.) parameter set; no new QM refit is reported in the abstract (normalized/extracts/2013al-venue-reactive-molecular-2_p1-2.txt).
MD application (integrated)¶
Engine / code: Reactive molecular dynamics; N/A — specific package name not on p1–2 excerpt—confirm in pdf_path.
System & composition: 500 H\(_2\)O molecules in a cell 25 × 25 × 23.93 Å (density ~1 g cm\(^{-3}\)), later expanded to 25 × 25 × 80 Å for interface relaxation (Methods in pdf_path).
Boundaries / periodicity: 3D periodic supercell for the slab geometry (Methods).
Ensemble: NVT for equilibration/production as summarized from the article Methods on this page.
Timestep: Δt = 0.25 fs for production (Methods).
Duration / stages: 500 ps NVT equilibration at 300 K; 100 ps interface relaxation after cell expansion; ROS impact trajectories include ≥1.4 ns examples for O; like-species bundles use 100 ps windows with five replicas each (Methods/Figure 1).
Thermostat: Bussi–Donadio–Parrinello thermostat, 100 fs coupling time, during NVT equilibration and production (Methods).
Center-of-mass restraint: z-drift restraint tying a dummy atom to the water COM (Figure 1).
Barostat / pressure: N/A — NPT barostat not used for the summarized NVT slab protocol.
Temperature: 300 K for equilibration and thermalized ROS initial velocities.
Electric field: N/A — not used.
Replica / enhanced sampling: N/A — umbrella / metadynamics not used; five independent replicas for selected like-species bundles (Methods).
Findings¶
Outcomes: OH, HO\(_2\), and H\(_2\)O\(_2\) reach bulk-like water regions of the slab; O, OH, and HO\(_2\) drive hydrogen-abstraction cascades, whereas H\(_2\)O\(_2\) remains non-dissociative in the reported water-contact runs (abstract alignment + article discussion summarized here). HO\(_2\) solution behavior shows rapid proton shuttling consistent with literature equilibrium constants (Methods/Results in pdf_path).
Comparisons: ROS fates are contrasted with expectations from plasma medicine literature on transport through biofilms (introduction chain).
Sensitivity / levers: Penetration vs surface scavenging depends on species identity (O vs OH vs HO\(_2\) vs H\(_2\)O\(_2\)) and initial placement/replica sampling (Figure 1 protocol).
Limitations: Simplified planar water film; ReaxFF accuracy for O\(_3\)/RNS excluded in this parameterization; plasma formation chemistry is not simulated—only post-liquid ROS + water.
Corpus honesty: Wiki slug prefix 2013al- is a corpus artifact; metadata corresponds to 2014 J. Phys. D pdf_path. Duplicate ingest: [[2013al-venue-reactive-molecular]].
Limitations¶
See Findings (limitations bullet). Prefer this slug’s pdf_path when reconciling hashes with the 2013al-venue-reactive-molecular PDF path.
Relevance to group¶
Adri C. T. van Duin coauthored reactive ROS/water simulations for plasma biointerfaces.
Citations and evidence anchors¶
- DOI 10.1088/0022-3727/47/2/025205 — J. Phys. D: Appl. Phys. 47, 025205 (2014).
- PDF:
papers/Yusupov_JPhysD_plasma_medicine_2014.pdf; extract:normalized/extracts/2013al-venue-reactive-molecular-2_p1-2.txt.