TwoIslands
Some proteins are two little islands joined by a string. AlphaFold can draw each island crisply and still be unsure how the two sit next to each other. Before you see the answer, paint your prior: are the islands Firmly placed, or Fuzzy? Then reveal the real PAE map and check. Everything runs locally; nothing about you is collected.
This is the tool — the gentle, 9–14 companion to HingeHunt. Your prior is scored against the live PAE matrix fetched from AlphaFold, not a stored answer. The proteins are listed below (works without JavaScript). A native version, when it ships, adds offline use.
Loading the game… If it does not start, the guide below still works.
Before you call it: guessing alone would be right about 1 time in 2.
Most first predictions in science miss. Checking is the point.
Saying 'fuzzy' every time would score 2 of 3.
How to play. Press Start. Look at the two crisp islands and paint your prior — Firm or Fuzzy (buttons or keys 1/F, 2/Z). The real PAE map is revealed and your prior is scored. Press Enter or Next.
Why two confident islands can float apart
Troponin C, a close cousin of calmodulin, sits on the thin filaments of heart muscle. Calcium binding to its N-terminal lobe starts each contraction, while the C-terminal lobe anchors it to the rest of the troponin complex. Each lobe is well folded, but they are linked flexibly, so the model can be sure of each shape and unsure how they sit together: that is what the PAE between them shows.
Crisp islands, fuzzy bridge
pLDDT tells you how sure the model is about each island’s own shape. PAE tells you how sure it is about where one island sits relative to the other. When the bridge between two islands is floppy, the PAE between them is pale even though each island is crisp — that is a common misreading, made gentle here as a Firm-or-Fuzzy paint.
The proteins
Answer key — open it after you play
| Protein | The two islands | Note |
|---|---|---|
| Calmodulin CALM1 · P0DP23 | N-lobe (1–75) · C-lobe (82–148) | Two lobes on a floppy string. |
| Troponin C TNNC1 · P63316 | N-lobe (1–80) · C-lobe (90–161) | A muscle calcium sensor; a calmodulin cousin. |
| Phosphoglycerate kinase 1 PGK1 · P00558 | N-domain (1–185) · C-domain (200–417) | Two domains with a hinge between them. |
Methods & about
This is a teaching game and a simplification. The score is the live mean inter-island PAE (under 10 Å = firm, over 15 Å = fuzzy, in between = either), computed from the fetched AlphaFold matrix; island boundaries are approximate. Structures + PAE are the real AlphaFold predictions, fetched in your browser. No score history, no accounts, nothing sent anywhere.
Want the grown-up version? Try HingeHunt, or the Fold Commons apps. Everything we make is free and non-profit.