Matthew L Plenert | PubMed Health

PubMed2004

Multiphoton-excited serotonin photochemistry.

We report photochemical and photophysical studies of a multiphoton-excited reaction of serotonin that previously has been shown to generate a photoproduct capable of emitting broadly in the visible spectral region. The current studies demonstrate that absorption of near-infrared light by an intermediate state prepared via three-photon absorption enhances the photoproduct formation yield, with the largest action cross sections ( approximately 10(-19) cm(2)) observed at the short-wavelength limit of the titanium:sapphire excitation source. The intermediate state is shown to persist for at least tens of nanoseconds and likely to be different from a previously reported oxygen-sensitive intermediate. In addition, the two-photon fluorescence action spectrum for the fluorescent photoproduct was determined and found to have a maximum at approximately 780 nm (3.2 eV). A general mechanism for this photochemical process is proposed.

Aluminum Oxide↗

PubMed2003

Microsecond electrophoresis.

Although analysis strategies exist for probing a diverse array of molecular properties, most of these approaches are not amenable to the study of reaction intermediates and other transient species. Separations in particular can provide detailed information on attributes not readily measured by spectroscopy but typically are performed over time scales much longer than the life span of highly unstable compounds. Here we report the development of an electrophoretic strategy that dramatically extends the practical speed limit for fractionations and demonstrate its utility in examining transient hydroxyindole photoproducts. Fluorescent reaction intermediates are optically generated in femtoliter volumes within a flowing reagent stream and are differentially transported at velocities as large as 1.3 m.s(-1), thereby minimizing band variance and allowing multicomponent reaction mixtures to be resolved over separation paths as short as 9 microm. Analyte migration times and band variances do not deviate significantly from basic theory for separations performed with fields that exceed 0.1 MV.cm(-1), indicating that effects from Joule heating are minor. We demonstrate the feasibility of achieving baseline resolution of a binary mixture in <10 micros, nearly 100-fold faster than previously possible. Application of this approach to the study of a range of short-lived molecules should be feasible.

5-Hydroxytryptophan↗