A modular transient absorption spectrometer / fluorometer has been constructed using affordable components. Pulsed high-power LEDs were used as sources for both the pump and the probe. Several LED modules with different color LEDs have been prepared, allowing us to investigate different pump wavelengths easily. With a white LED as the probe, full visible absorption spectra of intermediates or excited states have been acquired. The spectra are recorded by a diode array detector from Ocean Optics. A low-cost digital delay generator from Quantum Composers controls the timing between the pump and probe pulses and the data acquisition. This spectrometer has been used to measure changes in the light-induced isomerization kinetics of Congo Red, a common organic dye, as the pH was varied, and as the ethanol-water ratio in the solvent mixture was varied. By deactivating the probe LED, the apparatus converts to a fluorometer. We have investigated changes in absorbance and fluorescence spectra when cyanine dyes bind either in the minor groove of DNA or by intercalation. This reveals the roles that both ligand structure and noncovalent interactions play in the binding of small molecules to DNA. This is an incredibly versatile spectrometer with a wide variety of applications in many divisions of chemistry.

Using an affordable transient absorption spectrometer/fluorometer to investigate isomerization of an organic dye and small molecule binding to DNA

251st National Meeting (2016)

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.