Instrumentation for fluorescence lifetime measurement using photon counting

We describe the evolution of HORIBA Jobin Yvon IBH Ltd, and its time-correlated single-photon counting (TCSPC) products, from university research beginnings through to its present place as a market leader in fluorescence lifetime spectroscopy. The company philosophy is to ensure leading-edge research capabilities continue to be incorporated into instruments in order to meet the needs of the diverse range of customer applications, which span a multitude of scientific and engineering disciplines. We illustrate some of the range of activities of a scientific instrument company in meeting this goal and highlight by way of an exemplar the performance of the versatile DeltaFlex instrument in measuring fluorescence lifetimes. This includes resolving fluorescence lifetimes down to 5 ps, as frequently observed in energy transfer, nanoparticle metrology with sub-nanometre resolution and measuring a fluorescence lifetime in as little as 60 μs for the study of transient species and kinetics

Fluorescence of the higher helicenes

The fluorescence spectra, quantum yields and lifetimes of [10]-, [11]-, [12]-, [13]-, and [14]-helicene and 3,15-ethanoheptahelicene have been observed in 1,4-dioxan solution at room temperature. The fluorescence occurs from the 1 Lb state, which is not observed in absorption. The fluoroscence rate parameter decreases with increase in ring number N, in a manner which depends on whether N is odd or even. The intersystem crossing rate parameter increases with N up to N = 11 and then decreases. The interval between the fluorescence maxima, which is equated to the So symmetrical vibrational mode, decreases from 1200 cm-1 (N = 6) to 650 cm-1 (N = 13). © 1976.SCOPUS: ar.jinfo:eu-repo/semantics/publishe

Improved biocompatibility of protein encapsulation in sol-gel materials

By using the fluorescent dye 6-propionyl-2-(N,N-dimethylamino) naphthalene (PRODAN) to monitor methanol generated during tetramethyl orthosilicate polymerization we have optimised the encapsulation of protein in silica sol-gel monoliths with respect to completion of hydrolysis and distillation in order to remove methanol such that protein can be added without denaturation. A minimum of 24 h at +4 °C was found to be required before hydrolysis is complete and 3-5 min of vacuum distillation at 50 °C and 300 mbar needed to remove methanol before the gel is formed. The biocompatibility of a tetramethyl orthosilicate sol-gel monolith was demonstrated by preserving the trimer protein allophycocyanin (APC) in its native form for up to 500 h. This obviates the previously essential requirement of covalently binding the trimer together in order to prevent dissociation into monomers and has enabled observation of native APC trimer in a sol-gel pore for the first time down to the single molecule level using combined fluorescence spectroscopy and confocal microscopy. The higher stability afforded by the protocol we describe could impact on the application of sol-gel materials to single-molecule studies of wider bearing such as protein folding and aggregation