Effect of the Environment on Absorption Spectra

The environment here can be the temperature, solvent, chromophore interaction with another molecule, etc. 

In native VCPO, the position and intensity of cofactor-induced absorption are sensitive to pH change at pH 5, the band is blue-shifted (Xmax 308 nm), and the intensity is decreased to e = 2.0 mM-1 cm-1. The exact correlation between the above-mentioned spectral features and the known X-ray data are complex, but a further UV-VIS analysis of several mutants of this enzyme showed the importance of several structural elements. A His496Ala mutant showed no optical spectrum (Hemrika et al. 1999), whereas crystal structure of this mutant showed the presence of tetrahedral vanadate in the active site (Macedo-Ribeiro et al. 1999), indicating that the V— N bond is crucial for the observed spectrum. The effect of other mutations can be seen in Table 1.1. 

H496A No spectrum observed — — Renirie etal. (2000a) 

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