Red edge excitation effect in intact eye lens

Shift in the wavelength of emission upon shift in the excitation wavelength towards the red edge of the absorption band is termed Red Edge Excitation Shift (REES). This effect is observed only in a situation where the fluorophore mobility with respect to the surrounding matrix is considerably reduced. We have observed such red edge excitation effect in the intact eye lens. The REES observed for a normal lens is different from that seen in a photodamaged lens and hence appears to be a potential tool to monitor the changes in the state of the lens. Photodamage experiments with tryptophan in polyethylene glycol (PEG) and intact eye lens indicate that the red edge photon can also cause photodamage

The conformational status of a protein influences the aerobic photolysis of its tryptophan residues: melittin, β-lactoglobulin and the crystallins

We have studied the aerobic photolysis of the tryptophan residues of the proteins melittin and p-lactoglobulin when the proteins are in ordered conformations and when they are in randomly coiled states. The results suggest that the conformational status of the protein is a factor that influences the photolysis of the constituent tryptophan residues. This point appears to be of relevance to the photo-oxidation of the tryptophan residues of the eye lens proteins crystallins