The 20 amino acids

A Ala Alanine Small Hydrophobic Helix: ++ Strand: – Turn: – – Mutate to Ala if you have to mutate but have no clue to which residue

C Cys Cysteine Small Hydrophobic Sulfur containing Helix: – Strand: + Turn: + The SH-group is very reactive: Can make Cys-Cys bridges Can bind metal ions (especially Zn and Cu)

D Asp Aspartate Intermediately large Hydrophilic Negatively charged Helix: 0 (++ at N-terminus) Strands: – – Turn: ++ Often in active sites Can bind ions (mainly calcium)

E Glu Glutamate Large Hydrophilic Negatively charged Helix: ++ Strand: 0 Turn: –

F Phe Phenylalanine Large Hydrophobic Aromatic Helix: 0 Strand: ++ Turn: – –

G Gly Glycine Smallest residue No side chain Helix: – – Strand: – Hydrophobicity undetermined Very flexible Star of the turn Helix: – – Strand: – Turn: ++

H His Histidine Large Hydrophilic Charge (depending on the environment): Positive Neutral or Negative No secondary structure preference Often in active sites Can bind metal ions (mainly Zn, Ni, Cu)

I Ile Isoleucine Intermediately large Hydrophobic Helix: 0 Strand: ++ Turn: – –

K Lys Lysine Large Hydrophilic Positively charged Helix: ++ Strand: – Turn: 0 Long, flexible side chain

L Leu Leucine Intermediately large Hydrophobic Helix: ++ Strand: + Turn: – –

M Met Methionine Large Hydrophobic Sulfur containing Helix: ++ Strand: 0 Turn: – – Non-reactive sulfur which can bind metal ions Often the first residue of the sequence and therefore at the surface (forced marriage)

N Asn Asparagine Intermediately large Hydrophilic Helix: – – Strand: 0 Turn: ++ Can bind ions (Ca) but not as well as its isosteric partner Asp

P Pro Proline Small Hydrophobic Helix: – – (except at the first position) Strand: – – Turn: ++ Imino acid No backbone proton Pre-bend for turns (forced marriage)

Q Gln Glutamine Large Hydrophilic Helix: + Strand: 0 Turn: 0 Isosteric with Glu

R Arg Arginine Large Hydrophilic Positively charged No secondary structure preference Contains a rigid guanidinium group

S Ser Serine Small Intermediate hydrophobicity Alcoholic Helix: – Strand: – Turn: ++ Often in active sites (with Asp and His) Can bind calcium

T Thr Threonine Small Intermediate hydrophobicity Alcoholic Helix: 0 Strand: + Turn: 0 Can bind calcium

V Val Valine Small Hydrophobic Helix: 0 Strand: ++ Turn: – – Isosteric with Thr

W Trp Tryptophan Largest residue Hydrophobic Aromatic Helix: 0 Strand: ++ Turn: 0 Most conserved residue

Y Tyr Tyrosine Large Intermediate hydrophobicity Aromatic Alcoholic Helix: – Strand: ++ Turn: 0