Space-filling model of the L -tryptophan molecule, C ₁₁ H ₁₂ N ₂ O ₂ , in the zwitterionic form found in the crystal structure at 123 K determined by single-crystal X‐ray diffraction and reported in Acta Cryst. B (2012), 68 , 549-557 ( CSD entry VIXQOK ).

Colour code:

Carbon, C: grey

Hydrogen, H: white

Nitrogen, N: blue

Oxygen, O: red