1. The 20 amino acids

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

3. 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)

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

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

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

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

8. 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)

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

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

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

12. 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)

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

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

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

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

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

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

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

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

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