Intensity-dependent enzyme photosensitization using 532 nm nanosecond laser pulses

• Published in: Photochemistry and photobiology Vol. 63; no. 2; p. 154
• Main Authors: Lambert, C R, Stiel, H, Leupold, D, Lynch, M C, Kochevar, I E
• Format: Journal Article
• Language: English
• Published: United States 01-02-1996
• Subjects: Chemical Phenomena; Chemistry, Physical; Cholinesterase Inhibitors - chemistry; Cholinesterase Inhibitors - pharmacology; Erythrocyte Membrane - drug effects; Erythrocyte Membrane - enzymology; Erythrocyte Membrane - radiation effects; Humans; Photochemistry; Photosensitizing Agents - chemistry; Photosensitizing Agents - pharmacology; Rose Bengal - chemistry; Rose Bengal - pharmacology
• ISSN: 0031-8655
• DOI: 10.1111/j.1751-1097.1996.tb03007.x

The intensity dependence of the rose bengal (RB)-photosensitized inhibition of red blood cell acetylcholinesterase has been studied experimentally and the results compared to a quantitative excitation/deactivation model of RB photochemistry. Red blood cell membrane suspensions containing 5 microM RB were irradiated with 532 nm, 8 ns laser pulses with energies between 1 and 98.5 mJ. A constant dose (7 J) was delivered to all samples by varying the total number of pulses. At incident energies greater than approximately 4.5 mJ/pulse, the efficiency for photosensitized enzyme inhibition decreased as the energy/pulse increased. The generation of RB triplet state was monitored as a function of laser energy and the triplet-triplet absorption coefficient was determined to be 1.9 x 10(4) M-1 cm-1 at 530 nm. The number of singlet oxygen molecules produced at each intensity was calculated from both the physico-mathematical model and from laser flash photolysis results. The results indicated that the photosensitized inhibition of acetylcholinesterase was exclusively mediated by singlet oxygen, even at the highest laser intensities employed.