title: Two-Photon Activation of p-Hydroxyphenacyl Phototriggers: Toward Spatially Controlled Release of Diethyl Phosphate and ATP.
abstract: Two-photon activation of the p-hydroxyphenacyl (pHP) photoactivated protecting group is demonstrated for the first time using visible light at 550 nm from a pulsed laser. Broadband two-photon absorption measurements reveal a strong two-photon transition (>10 GM) near 4.5 eV that closely resembles the lowest-energy band at the same total excitation energy in the one-photon absorption spectrum of the pHP chromophore. The polarization dependence of the two-photon absorption band is consistent with excitation to the same S3 ((1)ππ*) excited state for both one- and two-photon activation. Monitoring the progress of the uncaging reaction under nonresonant excitation at 550 nm confirms a quadratic intensity dependence and that two-photon activation of the uncaging reaction is possible using visible light in the range 500-620 nm. Deprotonation of the pHP chromophore under mildly basic conditions shifts the absorption band to lower energy (3.8 eV) in both the one- and two-photon absorption spectra, suggesting that two-photon activation of the pHP chromophore may be possible using light in the range 550-720 nm. The results of these measurements open the possibility of spatially and temporally selective release of biologically active compounds from the pHP protecting group using visible light from a pulsed laser.
authors.affiliation: Department of Chemistry, University of Kansas , Lawrence, Kansas 66045, United States.
authors.forename: Amanda L
authors.initials: AL
authors.lastname: Houk
authors.affiliation: Department of Chemistry, University of Kansas , Lawrence, Kansas 66045, United States.
authors.forename: Richard S
authors.initials: RS
authors.lastname: Givens
authors.affiliation: Department of Chemistry, University of Kansas , Lawrence, Kansas 66045, United States.
authors.forename: Christopher G
authors.initials: CG
authors.lastname: Elles
mesh_terms: D000255:Adenosine Triphosphate / Q000737:chemistry*; D007834:Lasers; D015394:Molecular Structure; D010755:Organophosphates / Q000737:chemistry*; D010648:Phenylacetates / Q000737:chemistry*; D017785:Photons
chemical_list: D010755:Organophosphates; D010648:Phenylacetates; C008070:4-hydroxyphenylacetic acid; C034789:diethyl phosphate; D000255:Adenosine Triphosphate