NotMarbles
Draw a protein as space-filling spheres and it looks like a solid pile of hard, fixed marbles. It isn’t. Every atom is jiggling all the time, and some parts of a protein move far more than others. In this game you bet which regions hold their place and which smear — then watch the mobile ones jitter. Everything runs locally; nothing about you is collected.
This is the tool — a small game, no login, nothing tracked. Every protein and its regions are listed in full below (works without JavaScript). Motion respects your “reduce motion” setting.
Loading the game… If it does not start, the full region guide below still works.
How to play. Press Start. Select a region (click a column, or ←/→) and bet H (holds, rigid) or S (smears, mobile). Press R to reveal — the mobile regions jitter — and score. Press Enter or Next.
A snapshot of something that jiggles
A structure — even a crisp space-filling one — is a snapshot or an average of a molecule in constant thermal motion. An NMR ensemble shows this directly: it is a bundle of models, and where they disagree, that region is mobile; where they overlap, it is rigid. (Crystallographic B-factors tell the same story.) So a space-filling picture is not a bag of fixed marbles — that is the misconception this game targets (M10). Ubiquitin’s little C-terminal tail smears; BPTI barely moves at all.
The proteins and how they move
Ubiquitin · UBB · P0CG47 · 1D3Z (NMR)
| Region | Residues | Moves? |
|---|---|---|
| N-terminal β-hairpin | 1–17 | Holds (rigid) |
| Core (helix + β-sheet) | 18–70 | Holds (rigid) |
| C-terminal tail (…LRGG) | 71–76 | Smears (mobile) |
BPTI (trypsin inhibitor) · BPTI · P00974 · 5PTI
| Region | Residues | Moves? |
|---|---|---|
| N-terminal region | 1–15 | Holds (rigid) |
| Disulfide-stapled core | 16–45 | Holds (rigid) |
| C-terminal region | 46–58 | Holds (rigid) |
Calmodulin · CALM1 · P0DP23 · 2K0E (NMR)
| Region | Residues | Moves? |
|---|---|---|
| N-lobe (EF-hands 1–2) | 1–76 | Holds (rigid) |
| Central linker helix | 77–80 | Smears (mobile) |
| C-lobe (EF-hands 3–4) | 81–148 | Holds (rigid) |
Methods & about
This is a teaching game and honest about being a simplification: the sphere cluster is a schematic space-filling view (not real atomic coordinates), and “holds vs smears” is a coarse, binary stand-in for continuous per-residue mobility (as measured by an NMR ensemble spread or crystallographic B-factors). The jitter is undirected thermal wobble — atoms bump and jiggle, they do not travel with purpose. The examples are canonical: ubiquitin (rigid core, mobile Gly-Gly tail), BPTI (a textbook rigid, disulfide-locked protein), and calmodulin (rigid lobes on a flexible central linker). Every region is written by hand, not generated, and science-checked. No accounts, no storage, no servers.
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