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 | onLy Lysine and Leucine are pureLy ketogenic | Leu · Lys |
| Glucogenic and ketogenic | PITTT | Phe · Ile · Thr · Trp · Tyr |
| Aromatic | W F Y. Say it fast: "wifey." You put a ring on it. | Trp · Phe · Tyr |
| Sulfur-containing | Cys and Met carry the Sulfur, but only Cys's free -SH can cross-link | Cys · Met |
| Hydroxyl-containing | S-T-Y: Ser, Thr, Tyr, where kinases park their phosphates | Ser · Thr · Tyr |
| Polar, uncharged | STaCk QuiN: Ser, Thr, Cys, Gln, Asn | Ser · Thr · Cys · Gln · Asn |
| Polar, charged | DEHKR, said "decker": D and E acidic, H K R basic | Asp · Glu · His · Lys · Arg |
| Branched-chain | "I Love Vermont" maple syrup: Ile, Leu, Val | Ile · Leu · Val |
| Quirkily coded | QWKYNERD, the "quirky nerd" eight whose one-letter code is not their initial | Gln · Trp · Lys · Tyr · Asn · Glu · Arg · Asp |
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 ring locks the backbone, the helix breaker. |
| 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: SH = SulfHydryl. Two hissing cysteines fuse into a disulfide Cross-link. |
| 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, the 4th letter, with 4 carbons. E, the 5th letter, has 5. |
| Glutamate | GlutamatE → E. E is longEr than D by exactly one CH₂. |
| Lysine | Lysine takes K because Leucine claimed L, and K like K⁺: positive at pH 7. |
| 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. |