title: Partial Unfolding of Tubulin Heterodimers Induced by Two-Photon Excitation of Bound meso-Tetrakis(sulfonatophenyl)porphyrin.
abstract: The water-soluble porphyrin meso-tetrakis(p-sulfonatophenyl)porphyrin (TSPP) can be noncovalently bound to tubulin and used as a photosensitizer, which upon irradiation triggers photochemical reactions that lead to conformational changes of the protein. These conformational changes in turn inhibit tubulin's primary function of polymerizing into microtubules. We explored the possibility of using two-photon excitation of the bound porphyrin to induce photosensitized protein unfolding. Although TSPP has a relatively low cross section (∼30 GM) our results did find that two-photon excitation of the ligand causes partial unfolding of the tubulin host and the inhibition of the in vitro formation of microtubules. Conversely, irradiating tubulin alone caused no such effects despite the large irradiance per pulse (97-190 GW/cm(2)). The conformational changes were characterized using spectroscopic studies and provide a promising protocol for the future application of non-native photosensitization of proteins.
authors.affiliation: The University of Texas at San Antonio , Department of Physics and Astronomy, One UTSA Circle, San Antonio, Texas 78249, United States.|Human Effectiveness Directorate, Bioeffects Division, Optical Radiation Bioeffects Branch, 711th Human Performance Wing, Joint Base San Antonio , JBSA Fort Sam Houston, Texas 78234, United States.
authors.forename: Brady
authors.initials: B
authors.lastname: McMicken
authors.affiliation: Human Effectiveness Directorate, Bioeffects Division, Optical Radiation Bioeffects Branch, 711th Human Performance Wing, Joint Base San Antonio , JBSA Fort Sam Houston, Texas 78234, United States.
authors.forename: Robert J
authors.initials: RJ
authors.lastname: Thomas
authors.affiliation: The University of Texas at San Antonio , Department of Physics and Astronomy, One UTSA Circle, San Antonio, Texas 78249, United States.
authors.forename: Lorenzo
authors.initials: L
authors.lastname: Brancaleon
mesh_terms: D017785:Photons; D011166:Porphyrins / Q000737:chemistry*; D058767:Protein Unfolding; D014404:Tubulin / Q000737:chemistry*
chemical_list: D011166:Porphyrins; D014404:Tubulin; C092400:meso-tetrakis(4-sulfonatophenyl)porphyrin