Primary Photo-Processes in Biology and Medicine

Recently there have been major developments in the experimental techniques available for the study of the primary events following the absorption of ultra-violet and visible radiation by biological systems. These techniques, which include absorption, emission, resonance Raman, electron spin resonance, nuclear magnetic resonance and photoacoustic spectroscopies, can be used to study the fate of transient species with lifetimes ranging from seconds to nanoseconds and extending in some cases, such as laser flash photolysis, to pico 12 15 (10- S)- and even femtoseconds (10- s). In parallel with these developments there has been a dramatic increase in the use of light in medicine via the direct photochemical alteration of endogenous molecules (phototherapy) or via the photoactivation of drugs in the skin or other tissue (photochemotherapy). Thus neonatal hyperbili rubinaemia can be routinely treated by phototherapy and psoriasis is frequently treated by PUVA photochemotherapy. A promising new photo chemotherapy used the phototoxicity of porphyrin drugs activated by red light to destroy solid malignant tumors. While some of the overall qualitative effects of such treatments are known, only recently have we begun to understand the associated molecular mechanisms. The primary molecular processes involve short-lived species. The pur pose of this Advanced Study Institute was to review some newer experi mental techniques for the study of such species, the application of these techniques to biological and medical systems and to examine the value of such information in phototherapeutic situations.

Inhalt
Instrumentation for the generation and detection of transient species.- Flash photolysis.- Pulse radiolysis.- Time-resolved fluorescence of dyes of bio-medical relevance: Influence of the environment.- Nonexponential fluorescence decay in tryptophan and tryptophan-containing peptides and proteins.- Time-resolved resonance Raman spectroscopy.- Flash photolysis NMR.- Time domain ESR.- Time-resolved photoacoustic and photothermal methods: Application to substances of biological interest.- Spectro-electrochemistry: Porphyrins and Metalloporphyrins.- Activated oxygen.- The historical development of ideas on applications of photosensitized reactions in the health sciences.- Drug-DNA interaction.- Some properties of furocoumarin (FC) excited states.- Photoreactions of furocoumarins (psoralens and angelicins).- Biological and medicinal aspects of furocoumarins (psoralens and angelicins).- Photochemistry of porphyrins and bile pigments in homogeneous solution.- Molecular and cellular mechanisms in photomedicine: Porphyrins in microheterogenous environments.- Cell photosensitization by psoralens and porphyrins.- Molecular and cellular mechanisms in photomedicine: Porphyrins in cancer treatment.- Skin and light.- Lasers in surgery and medicine.- Classification and mode of action of sun filter and sunblock products.- Participants.