In situ optical spectroscopy of some systems of biological interest.

Monitoring the optical absorption or emission spectrum of a condensed phase sample offers information about the supramolecular assembly, packing effects and other features characteristic of the phase that would be missed when one studies solution-state spectra. We have used the technique of photoacoustic spectroscopy to study intact biological specimens, such as algae, parasite cells and the eye lens. Such a study has offered information about the status of endogenous hemin in Plasmodium cells and the mode of interaction of antimalarial drugs of the chloroquine class therein. We have also attempted to do in situ fluorescence spectroscopy on isolated intact eye lenses, which has enabled us to follow the photochemistry and the status of the photoproduct of the oxidation of the trp residues of the crystallins of the lens.