Structure of the decarboxylated derivative of the chromophore from the fluorescent peptide produced by iron-deficient Azotobacter vinelandii

Abstract

Iron-deficient cultures of Azotobacter vinelandii contain a yellow-green fluorescent peptide which, upon hydrolysis, yield several amino-acids and a chromophoric residue which retains the spectral properties of the parent peptide. The decarboxylated derivative of the chromophore (I), which retains the spectral behaviour, has been determined by X-ray crystallographic study. Crystals are monoclinic, space group P2₁/c, with four molecules of C₁₃H₁₂N₃O₃Cl.2H₂O in the unit cell of dimensions a= 10·342(1), b= 6·986(1), c= 21·525(3)Å, β= 115·78(2)°. The structure was solved by direct methods from diffractometer data and refined by block-diagonal least-squares techniques to R 8·0% for 1331 independent reflections. The molecules are piled one above the other between hydrogen-bonded spirals of chloride ions and water molecules.