This page is thought to be a personal reminder on how to draw amino acids in LaTeX with the chemfig package. The package documentation is very well written, but personally, I think that some tangible and simple ‘practical’ examples are missing. Especially when one starts using it, it’d be great to have a simple vademecum with some (possibly, biological) examples. So here are mine. All the code chunks are highlighted in the rounded box, in the spirit of Jupyter Notebooks.

The generic amino acid can be typeset in his neutral form in LaTeX as

\schemestart
  \chemfig{ H_2 N-[:-30,]C(<:[:-120,]R)(<[:-60]H)(-[:30,]C(=[:90,0.7]O)(-[:-30,]OH)) }
\schemestop

and the result is

We can do better, simply by removing the H bound to the Cα and specifying the sidechain R. Omitting all the \schemestart and \schemestop commands (which must be included!), here are reported the skeletal formulæ for the amino acids in their zwitterionic form.¹ I am not sure all these formulæ are correct, though.

Nonpolar amino acids

• Glycine: \chemfig{ NH_3^\oplus -[:30]-[:-30](=[:30]O) (-[:-90]O^\ominus) }
  Click to reveal.

  
• Alanine: \chemfig{ H_3C-[:30]-[:-30](<[:-90,,,1]NH_3^\oplus) -[:30](=[:90]O) (-[:-30]O^\ominus) }
  Click to reveal.

  
• Valine: \chemfig{ H_3C-[:30](-[:90]CH_3)-[:-30](<[:-90,,,1]NH_3^\oplus) -[:30](=[:90]O) (-[:-30]O^\ominus) }
  Click to reveal.

  
• Cysteine: \chemfig{ HS-[:30]-[:-30](<[:-90,,,1]NH_3^\oplus) -[:30](=[:90]O) (-[:-30]O^\ominus) }
  Cystein is one of the key amino acids for protein folding, since it can build very strong disuphide bridges that help the folding process.
  Click to reveal.

  
• Proline: \chemfig{ *5(-\chembelow{N}{H}-((<:[:50])-[:-30](=[:-90]O) (-[:30]O^\ominus))<--) }
  Click to reveal.

  
• Leucine: \chemfig{ H_3C-[:-30](-[:-90]CH_3)-[:30]-[:-30](<[:-90,,,1]NH_3^\oplus) -[:30](=[:90]O) (-[:-30]O^\ominus) }
  Click to reveal.

  
• Isoleucine: \chemfig{ H_3C-[:-30]-[:30](<:[:90]CH_3)-[:-30](<[:-90,,,1]NH_3^\oplus) -[:30](=[:90]O) (-[:-30]O^\ominus) }
  Click to reveal.

  
• Methionine: \chemfig{ H_3C-[:30]S-[:-30]-[:30]-[:-30](<[:-90,,,1]NH_3^\oplus) -[:30](=[:90]O) (-[:-30]O^\ominus) }
  Click to reveal.

  
• Phenilalanine:² \chemfig{ *6(-=-(-[:30]-[:-30](<[:-90,,,1]NH_3^\oplus) -[:30](=[:90]O) (-[:-30]O^\ominus))=-=) }
  Click to reveal.

  
• Tryptophan: \chemfig{ *6(-*5(-[,,,2]HN-=(-[:30]-[:-30](<[:-90]NH_3^\oplus)-[:30](=[:90]O)-[:-30]O^\ominus)-)=-=-=)}
  Click to reveal.

  

Polar amino acids

• Serine: \chEMFIG{ HO-[:30]-[:-30](<[:-90,,,1]NH_3^\oplus) -[:30](=[:90]O) (-[:-30]O^\ominus) }
  Click to reveal.

  
• Threonine: \chemfig{ H_3C-[:30](-[:90]OH)-[:-30](<[:-90,,,1]NH_3^\oplus) -[:30](=[:90]O) (-[:-30]O^\ominus) }
  Click to reveal.

  
• Tyrosine: \chemfig{ HO-[:30]*6(-=-(-[:30]-[:-30](<[:-90,,,1]NH_3^\oplus) -[:30](=[:90]O) (-[:-30]O^\ominus))=-=) }
  Click to reveal.

  
• Asparagine: \chemfig{ O=[:-30](-[:-90]NH_2)-[:30]-[:-30](<[:-90,,,1]NH_3^\oplus) -[:30](=[:90]O) (-[:-30]O^\ominus) }
  Contrarily to the common belief, the typical smell of pee is not given by asparagine, since it does not contain phosphate atoms which are typically responsible for bad smells!
  Click to reveal.

  
  \
• Glutamine: \chemfig{ H_2N-[:30](=[:90]O)-[:-30]-[:30]-[:-30](<[:-90,,,1]NH_3^\oplus)-[:30](=[:90]O) (-[:-30]O^\ominus) }
  Click to reveal.

  

Positively-charged amino acids

• Lysine: \chemfig{ H_3^\oplus N-[:-30]-[:30]-[:-30]-[:30]-[:-30](<[:-90,,,1]NH_3^\oplus) -[:30](=[:90]O) (-[:-30]O^\ominus) }
  Click to reveal.

  
• Arginine: \chemfig{ H_3^\oplus N-[:30](=[:90]NH)-[:-30]\chembelow{N}{H}-[:30]-[:-30]-[:30]-[:-30](<[:-90,,,1]NH_3^\oplus) -[:30](=[:90]O) (-[:-30]O^\ominus) }
  Click to reveal.

  
• Histidine: \chemfig{ H_2^\oplus N*5(-=(-[:30]-[:-30](<[:-90,,,1]NH_3^\oplus) -[:30](=[:90]O) (-[:-30]O^\ominus))-N=-) }
  Click to reveal.

  

Negatively-charged amino acids

• Aspartic acid: \chemfig{ O=[:-30](-[:-90]O^\ominus)-[:30]-[:-30](<[:-90,,,1]NH_3^\oplus) -[:30](=[:90]O) (-[:-30]O^\ominus) }
  Click to reveal.

  
• Glutamic acid: \chemfig{ O^\ominus-[:30](=[:90]O)-[:-30]-[:30]-[:-30](<[:-90,,,1]NH_3^\oplus) -[:30](=[:90]O) (-[:-30]O^\ominus) }
  Click to reveal.