Characterization of the photoproducts of protoporphyrin IX bound to human serum albumin and immunoglobulin G

L Brancaleon, SW Magennis, Ifor David William Samuel, E Namdas, A Lesar, H Moseley

Research output: Contribution to journalArticlepeer-review

46 Citations (Scopus)

Abstract

Clinically useful photosensitisers (PSs) are likely bound to subcellular and molecular targets during phototherapy. Binding to a macromolecule has the potential to change the photophysical and photochemical characteristics of the PSs that are crucial for their phototoxicity and cell-killing activity. We investigated the effects of binding of a specific PS (protoporphyrin IX or PPIX) to two proteins, human serum albumin (HSA) and a commercially available immunoglobulin (IgG). These two proteins provide two different environments for PPIX. The albumin binds PPIX in hydrophobic binding sites located in subdomain IIA and IIIA, conversely IgG leaves PPIX exposed to the solvent. We show that photophysical parameters such as emission maxima and fluorescence lifetime depend on the binding site. Our results indicate that the different binding site yields very different rates of formation of photoproducts (more than three times higher for PPIX bound to HSA than to IgG) and that different mechanisms of formation may be occurring. Our characterization shows the relevance of protein binding for the photochemistry and ultimately the phototoxicity of PSs. (C) 2003 Elsevier B.V. All rights reserved.

Original languageEnglish
Pages (from-to)351-360
Number of pages10
JournalBiophysical Chemistry
Volume109
DOIs
Publication statusPublished - 1 Jun 2004

Keywords

  • human serum albumin
  • immunoglobulin G
  • protoporphyrin IX
  • fluorescence spectroscopy
  • PHOTOPHYSICAL PROPERTIES
  • PORPHYRINS
  • PROTEINS
  • PHOTOOXIDATION
  • AGGREGATION
  • FLUENCE
  • BINDING
  • TARGETS
  • OXYGEN

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