coarse-grained

coarse-grained is a skill for Claude Code, Codex from Kdevos12/ALKYL. It costs 66 tokens per session (770 once invoked), scanned A, original, MIT.

A guide to coarse-grained molecular dynamics, a simulation method that represents groups of atoms as larger particles so bigger biological systems can be simulated for longer times. It focuses on the MARTINI 3 force field and GROMACS workflows.

In plain words
What is it for?
Simulating lipid membranes, vesicles, membrane proteins, lipid nanoparticles, protein binding or insertion, large conformational changes, and conversion back to atom-level models.
Why use it?
Using fewer particles makes it practical to study large membrane systems, major shape changes, and processes that are too slow or large for atom-by-atom simulation.

Skill for Claude CodeCodex

Part of the alkyl plugin — 27 skills shipped together

Install

Getting it into your agent

One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.

agentmods
npx agentmods add skills/kdevos12/alkyl/coarse-grained
Any agent
npx skills add Kdevos12/ALKYL --skill coarse-grained
Clone the repo
git clone --depth 1 https://github.com/Kdevos12/ALKYL

Made for: Claude Code, Codex.

Or install alkyl, the plugin that ships this one along with the rest of its 27 skills.

Wrote this? Show the measurements

A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.

agentmods badge for coarse-grained

README.md
[![agentmods](https://agentmods.dev/badge/skills/kdevos12/alkyl/coarse-grained.svg)](https://agentmods.dev/skills/kdevos12/alkyl/coarse-grained)
Your own site
<a href="https://agentmods.dev/skills/kdevos12/alkyl/coarse-grained"><img src="https://agentmods.dev/badge/skills/kdevos12/alkyl/coarse-grained.svg" alt="Measured on agentmods" height="20"></a>
Per session 66 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 770 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. Scan, not verified.
Origin original No closer match found in the catalogue.
Token cost

What it costs to keep this loaded

Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.

ModelPer sessionOnce invoked
Fable 5 $0.00066 $0.00770
Opus 5 $0.00033 $0.00385
Sonnet 5 $0.00013 $0.00154
Haiku 4.5 $0.00007 $0.00077

Measured 3d ago against content hash bdceb13f1417, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

coarse-grained scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 3d ago.

A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.

Nothing flagged

None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.

skills/coarse-grained/SKILL.md · 64 lines

How it starts

The opening of the file, as written. The whole thing — 64 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Coarse-Grained Molecular Dynamics

Purpose

Run µs–ms scale MD simulations using coarse-grained force fields. Primary use cases: membrane self-assembly, protein-membrane interactions, lipid nanoparticles, large conformational changes, crowding effects.

When to Use This Skill

  • Simulating lipid bilayers, vesicles, or membrane proteins
  • Accessing timescales (µs–ms) beyond all-atom MD reach
  • Screening protein-membrane binding or insertion
  • Studying large-scale conformational changes (IDPs, domain motion)
  • Building membrane systems for subsequent AA MD (backmapping)
  • Coarse-grained small molecule parameterization (MARTINI)

Reference Files

File Content
references/cg-theory.md CG resolution levels, mapping schemes, Boltzmann inversion, force matching, MARTINI 3 philosophy, bead types, scaling factors
references/martini-proteins.md martinize2, elastic network (ElNeDyn), Go-MARTINI, OpenMM/GROMACS protein CG setup, common pitfalls
references/martini-membranes.md Lipid library, insane.py membrane builder, CHARMM-GUI CG, protein-membrane embedding, lipid mixing
references/cgmd-workflows.md GROMACS CG workflow (mdp parameters, timestep, thermostat), OpenMM CG, backmapping (backward.py), equilibration protocol
references/cg-analysis.md MDAnalysis CG trajectories, membrane thickness/APL/order parameters, lateral diffusion, protein CG RMSD/RMSF, density profiles

Quick Routing

"Set up a lipid bilayer simulation"martini-membranes.md

"Convert my protein to MARTINI CG"martini-proteins.md

"Run a CG simulation in GROMACS"cgmd-workflows.md

"Backmap CG structure to all-atom"cgmd-workflows.md (backward.py section)

"Analyze membrane properties from CG trajectory"cg-analysis.md

"What resolution should I use?"cg-theory.md

Key Numbers (MARTINI 3)

Property Value
Mapping ratio ~4 heavy atoms per bead
Timestep (default) 20 fs (safe: 10–30 fs)
Time scaling factor ×4 (CG time ≈ 4× real time)
vdW cutoff 1.1 nm
Electrostatics cutoff 1.1 nm
Recommended thermostat v-rescale (τ=1 ps)
Recommended barostat Parrinello-Rahman (τ=12 ps)
Effective timestep 80 fs (20 fs × 4 scaling)
Accessible timescale µs per day (GPU)

Read the full file on GitHub · 64 lines

Files

What ships with it

5 files beside SKILL.md in the same directory: the scripts, references and assets a skill reads on demand. Not counted in the per-session cost; read them before you install if any of them is executable.

Changes

What this file has done since we first saw it

Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.

  1. 3d ago First seen · 64 lines · 66 tokens per session scan A bdceb13f1417

Subscribe to this mod's changes

coarse-grained is a skill published in the GitHub repository Kdevos12/ALKYL (6 stars, last pushed 5mo ago), licensed MIT. It adds 66 tokens to every session and 770 once invoked, about $0.0003 per session on Opus 5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-31.

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