Campus Units
Chemistry
Document Type
Article
Publication Version
Published Version
Publication Date
9-27-2005
Journal or Book Title
Journal of Physical Chemistry B
Volume
109
Issue
41
First Page
19484
Last Page
19489
DOI
10.1021/jp051645u
Abstract
The photophysics of hypericin have been studied in its complex with two different isoforms, A1-1 and P1-1, of the protein glutathione S-transferase (GST). One molecule of hypericin binds to each of the two GST subunits. Comparisons are made with our previous results for the hypericin/human serum albumin complex (Photochem. Photobiol. 1999, 69, 633−645). Hypericin binds with high affinity to the GSTs: 0.65 μM for the A1-1 isoform and 0.51 μM for the P1-1 isoform (Biochemistry 2004, 43, 12761−12769). The photophysics and activity of hypericin are strongly modulated by the binding protein. Intramolecular hydrogen-atom transfer is suppressed in both cases. Most importantly, while there is significant singlet oxygen generation from hypericin bound to GST A1-1, binding to GST P1-1 suppresses singlet oxygen generation to almost negligible levels. The data are rationalized in terms of a simple model in which the hypericin photophysics depends entirely upon the decay of the triplet state by two competing processes, quenching by oxygen to yield singlet oxygen and ionization, the latter of these two are proposed to be modulated by A1-1 and P1-1.
Copyright Owner
American Chemical Society
Copyright Date
2005
Language
en
File Format
application/pdf
Recommended Citation
Halder, Mintu; Chowdhury, Pramit Kumar; Das, R.; Mukherjee, Prasun; Atkins, W. M.; and Petrich, Jacob W., "Interaction of Glutathione S-Transferase with Hypericin: A Photophysical Study" (2005). Chemistry Publications. 636.
https://lib.dr.iastate.edu/chem_pubs/636
Comments
Reprinted (adatped) with permission from Journal of Physical Chemistry B 109 (2005): 19484, doi: 10.1021/jp051645u. Copyright 2005 American Chemical Society.