In this work, a study of the supramolecular interaction between a photochromic spirooxazine, 1,3-dihydro-1,3,3-trimethyl-8'-nitro-spiro[2H-indole-2,3'-[3H]naphth[2,1 -b][1,4]oxazine] and some amino acids has been carried out. The photochrome interplays with amino acids after UV irradiation, through its zwitterionic photomerocyanine form. The interaction has a negative catalytic effect on the thermal ring closure reaction of the photomerocyanine. The strength of this interaction is a function of the size of the group (R) anchored to the alpha carbon atom of the amino acid and is the greater the smaller R is. This behaviour can be applied to molecular recognition. (c) 2007 Elsevier B.V. All rights reserved.