Effect of aggregation on bacteriochlorin a triplet-state formation: a laser flash photolysis study.

Abstract

Bacteriochlorin a (BCA) is a potential photosensitizer for photodynamic therapy of cancer. It has been shown previously that the photoefficiency of the dye is mainly dependent on singlet oxygen (1O2) generation. Nanosecond laser flash photolysis was used to produce and to investigate the excited triplet state of the dye in methanol, phosphate buffer and dimiristoyl-L-alpha-phosphatidylcholine (DMPC) liposomes. The transients were characterized in terms of their absorption spectra, decay kinetics, molar absorption coefficients and formation quantum yield of singlet-triplet intercrossing. The lifetime of the BCA triplet state was measured at room temperature. The triplet-state quantum yield is quite high in methanol (0.7) and in DMPC (0.4) but only 0.095 in phosphate buffer. In the last case, BCA is in a monomer-dimer equilibrium, and the low value of the quantum yield observed was ascribed to the fact the triplet state is only formed by the monomers.

• Authors: Xavier Damoiseau, Francis Tfibel, Maryse Hoebeke, Marie-Pierre Fontaine-Aupart
• Journal: Photochemistry and photobiology (Photochem Photobiol) Vol. 76 Issue 5 Pg. 480-5 (Nov 2002) ISSN: 0031-8655 [Print] United States
• PMID: 12462641 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)

Chemical References

• Buffers
• Liposomes
• Phosphates
• Photosensitizing Agents
• Porphyrins
• Reactive Oxygen Species
• bacteriochlorin a
• Dimyristoylphosphatidylcholine
• Methanol

Topics

• Buffers
• Dimyristoylphosphatidylcholine (chemistry)
• Kinetics
• Lasers
• Liposomes
• Logistic Models
• Methanol (chemistry)
• Phosphates (chemistry)
• Photolysis
• Photosensitizing Agents (chemistry)
• Porphyrins (chemistry)
• Protein Conformation
• Reactive Oxygen Species (chemistry)
• Spectrophotometry, Atomic