The twenty residues
Amino acid mnemonics
The set phrases first — they answer more exam questions than any single structure — then one hook per residue.
The sets
| Set | Mnemonic | Members |
|---|---|---|
| Essential | PVT TIM HALL | Phe · Val · Thr · Trp · Ile · Met · His · Arg · Leu · Lys |
| Purely ketogenic | The two L's are pureLy ketogenic | Leu · Lys |
| Glucogenic and ketogenic | PITTT | Phe · Ile · Thr · Trp · Tyr |
| Aromatic | W F Y. Say it fast and it sounds like "wifey" | Trp · Phe · Tyr |
| Sulfur-containing | Cys and Met are the S-team | Cys · Met |
| Hydroxyl-containing | Ser, Thr, Tyr, the kinase targets | Ser · Thr · Tyr |
| Charged | Dragons Eat Knights Riding Horses (DEKRH) | Asp · Glu · Lys · Arg · His |
One per residue
| Residue | Hook |
|---|---|
| Glycine | G for Glycine, the only achiral amino acid. Its side chain is a single H. |
| Alanine | A for Alanine, the simplest carbon side chain: one CH₃. |
| Valine | V for Valine, the V-shaped fork of two methyls on Cβ. |
| Leucine | Leu branches LATE (at Cγ); Ile branches EARLY (at Cβ). |
| Isoleucine | I for Isoleucine, which branches at Cβ and so has a second chiral center. |
| Proline | P for Proline, the Prison. Its side chain loops back and locks up the nitrogen. |
| Methionine | M for Met, the START. AUG is its only codon and the initiator. |
| Phenylalanine | F = "Fenylalanine". Spell it with an F and the one-letter code follows. |
| Tyrosine | tYrosine. The Y is in the name, and the letter looks like the phenol stub. |
| Tryptophan | W = "double-u" = the double ring. The biggest letter for the biggest residue. |
| Serine | S for Serine: Small, with a Simple -OH. Serine is alanine plus OH. |
| Threonine | T for Threonine, serine plus a methyl, so it is the branched alcohol. |
| Cysteine | C for Cysteine, and C for the Cross-links it forms. |
| Asparagine | AsparagiNe → N. It is the amide of aspartate: swap the -OH for -NH₂. |
| Glutamine | Q-tamine. "Gln" sounds like Q, the spare letter next to N. |
| Aspartate | AsparDic acid → D. D is the shorter acid; E is D plus one CH₂. |
| Glutamate | GlutamatE → E. E is longEr than D by exactly one CH₂. |
| Lysine | Lysine takes K because Leucine already claimed L. K is the nearest free letter. |
| Arginine | aRginine → R. The most basic side chain of all, so it is essentially always positive. |
| Histidine | H for His, and for the H⁺ it hands back and forth. The only side chain that buffers near pH 7. |