This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. This project continues to further develop and maintain state of the art fast and ultrafast methods of optical and infrared spectroscopy that are indispensable for the study of a wide range of biological processes stretched over the widest possible range of time scales. Part of the work is aiming at developing new techniques for excited state lifetime and anisotropy measurements that use spontaneous emission as the detection of the excited state. This method will be applied to determine the excited state properties of DNA probes in collaborative experiments with Prof. Burgess. It is also proposed to incorporate a NOPA device into the ultrafast fluorescence upconversion apparatus which would be particularly important in the dynamical analysis of the DNA-labeling cassettes. For example, in those studies, it would important to employ excitation wavelengths specifically tuned to the absorption maxima of the energy donor chromophores near 490 nm, a wavelength not available by simply using the second harmonic of a Ti:S output. Nanosecond spectroscopy has demonstrated a wide range of applications over the whole of biology. It permits the identification of intermediate species in optically triggered processes. This research involves the development and maintenance of a nanosecond absorption spectrometer. This device continues to provide high quality spectra from the nanosecond to second time scale, with a wide range of sample handling and improved kinetic analysis software. The apparatus can record absorption or gain spectra of transients excited by pulses from a YAG laser running at 10Hz. The probe source is a microseond xenon flash transmitted to the sample with quartz optical fibers. The time resolution is achieved by a gated diode array with a gate width of 5 ns. We further plan to extend the use of our nanosecond apparatus to involve T-jump experiments based on a Raman shifter pump pulse provider and fluorescence detection as the probe signal.
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