# Amino-acid structure images

The 40 PNGs in this directory were retrieved on 2026-09-15 from the U.S. National Library of Medicine's PubChem PUG REST service:

`https://pubchem.ncbi.nlm.nih.gov/rest/pug/compound/name/{compound}/record/PNG?record_type={2d|3d}&image_size=300x300`

The compounds are the 20 standard proteinogenic amino acids, using their conventional one-letter codes as filenames. PubChem was queried for each `L-` amino acid by name; glycine, which is achiral, was queried as `glycine`. Both the `2d` line depictions and `3d` conformer PNGs are direct, unmodified outputs from PubChem.

PubChem PUG REST documentation: https://pubchem.ncbi.nlm.nih.gov/docs/pug-rest

## Ball-and-stick images

The `*-balls.png` files are direct Wikimedia Commons thumbnails of crystal-structure ball-and-stick renderings by Ben Mills. The Commons metadata marks all 20 works as public domain. They show zwitterionic amino acids and include visible hydrogen atoms.

| Code | Wikimedia Commons file |
| --- | --- |
| A | `Alanine-from-xtal-3D-bs-17.png` |
| R | `Arginine-from-xtal-3D-bs-17.png` |
| N | `Asparagine-from-xtal-3D-bs-17.png` |
| D | `Aspartic-acid-from-xtal-view-1-3D-bs-17.png` |
| C | `Cysteine-from-xtal-3D-bs-17.png` |
| E | `Glutamic-acid-from-xtal-view-1-3D-bs-17.png` |
| Q | `Glutamine-from-xtal-3D-bs-17.png` |
| G | `Glycine-zwitterion-from-xtal-3D-bs-17.png` |
| H | `Histidine-from-xtal-3D-bs-17.png` |
| I | `Isoleucine-from-xtal-3D-bs-17.png` |
| L | `Leucine-from-xtal-3D-bs-17.png` |
| K | `Lysine-from-xtal-3D-bs-17.png` |
| M | `Methionine-from-xtal-3D-bs-17.png` |
| F | `Phenylalanine-from-xtal-3D-bs-17.png` |
| P | `Proline-from-xtal-3D-bs-17-view-A.png` |
| S | `Serine-from-xtal-view-1-3D-bs-17.png` |
| T | `Threonine-from-xtal-3D-bs-17.png` |
| W | `Tryptophan-from-xtal-3D-bs-17.png` |
| Y | `Tyrosine-from-xtal-3D-bs-17.png` |
| V | `Valine-from-xtal-3D-bs-17.png` |

Commons category: https://commons.wikimedia.org/wiki/Category:Zwitterionic_forms_of_L-amino_acids

## Word bank

The frequency-ranked word bank is mechanically filtered from
`google-10000-english-usa-no-swears.txt` in the first20hours/google-10000-english
project. Only five-letter entries made entirely from the 20 standard amino-acid
one-letter codes are included. The source project contains its licensing notice:
https://github.com/first20hours/google-10000-english