Singlet oxygen generation by photodynamic agents

Abstract The singlet oxygen quantum yield of photodynamic agents was measured at 546 nm, 630 nm, and on the far-red absorption peak. The technique employed is available in most laboratories, in which the photosensitization of lysozyme is used as an internal actinometer. Measurements in a pH 7.4 phosphate buffer plus 1% Triton X-! 00 (PB/X 100) are scaled to 0.52 for methylene blue in the phosphate buffer. The average quantum yields are: hematoporphyrin IX (0.73), protoporphyrin IX (0.56) zinc protoporphyrin IX (0.91), mesotetra-(4-sulfonato-phenyl) porphine (0.61), Photofrin s (0.89), benzoporphyrin derivative monoacid ring-A (0.84), chlorin e6 in PB (0.64), pheophorbide a (0.69), and aluminum phthalocyanine tetrasulfonate (0.38). Protection factors were measured for added azide ion, 1,4-diazabicyclo [ 2.2.2]-octane, and superoxide dismutase. Spectral evidence is presented for chlorin e6 interactions with PB/TX 100 and for binding to lysozyme

Primary Mechanisms of Photosensitization by Furocoumarins

A proper understanding of the PUVA therapy action mechanism requires the synthesis of concepts developed at the level of molecules, single cells and whole organisms. Although progress has been made in identifying key factors within each level of organization, the interrelationships remain obscure. Important unanswered questions at the molecular and cellular levels include: (1) Which excited states of the furocoumarin in molecule (triplet or excited singlet) are involved in the formation of DNA monoadducts, and the conversion of monoadducts to cross-links. (2) How does the spectrum of the incident radiation affect the distribution of the initial photochemical products from the PUVA sensitizers. (3) What are the relative contributions of furocoumarin-DMA monoadducts, furocoumarin-DNA cross-links and singlet oxygen to mutagenesis and lethality in cells, at the furocoumarin and UV-A dose levels corresponging to PUVA therapy. Additional information about these key aspects of furocoumarin photosensitization should lead to a more definitive relationship of the cellular level events to the endpoints observed with PUVA therapy, and suggest directions for potential improvements in the current clinical procedures

The Science of Phototherapy: An Introduction

Phototherapy exemplifies scientific medicine. The major advances have resulted from effective collaborations between basic researchers and clinicians. This book is directed to clinicians and basic researchers who are interested in current and emerging implementations of phototherapy. It can serve as an introductory reference and a textbook for advanced undergraduate and graduate courses in medical physics and biomedical engineering. The emphasis is on the science underlying the various phototherapy procedures, which encompasses aspects of classical and molecular photophysics, biological photochemistry, photobiology and biophotonics. Topics that do not usually appear in other general sources include the theory and applications of tissue optics, Monte Carlo simulation, light dosimetry, and analytical modeling of laser surgery. Many illustrative problems with answers are provided to exemplify the more quantitative aspects of each topic

LASER FLASH PHOTOLYSIS

Author Institution: Biophysics Laboratory, Department of Physics Illinois Institute of TechnologyNanosecond flash photolysis research has been initiated in our laboratory utilizing a frequency doubled 1.06 Nd: YAG laser. Time and spectral resolution for transient species absorbing in the ultraviolet is 5 ns and 10 \AA respectively. Current research includes photodynamic and ultraviolet inactivation of enzymes. Recent work of dye sensitized photoinactivation of lysozyme by eosin shows that singlet oxygen is the major inactivating agent. A 1 as pulse of singlet oxygen is produced by irradiating oxygen-saturated eosin solutions at 530 nm, allowing for mechanisms involving singlet oxygen reactions to be studied. The current status of these and related investigations will be summarized. This work was supported by the Division of Biomedical and Environmental Research, U. S. Atomic Energy Commission on Contract No. AT(11-1) 2217.