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The results described here demonstrate that single-molecule fluorescence spectroscopy of molecules freely diffusing in solution can yield unique information about both the dynamics and conformations of proteins. We used single-molecule FRET to detect the dynamics in CaM on the timescales of 100’s of microseconds and a few milliseconds by cross-correlation analysis of the donor and acceptor signals. In addition, analysis of the distribution of donor-acceptor distances by single-molecule FRET demonstrates the presence of three distinct conformational substates of CaM in solution. Together these results paint a picture of a protein that is dynamic and flexible, accessing a range of distinct conformation substates in solution. It has further been the purpose of this review to show how time-resolved fluorescence decay measurements can be used in concert with single-molecule measurements. Analysis of the donor fluorescence decay by MEM confirmed the presence of three distinct conformational substates of CaM. The anisotropy decay of the donor in the presence of the acceptor showed that donor orientational motion can be described by a homogeneous orientational model, and thus the conformational substates do not result from distinct dynamic states of the donor fluorophore. The predicted uncertainty in the FRET orientational factor further shows that the observed single-molecule distance distributions cannot result from heterogeneous conformations of the acceptor dye. Thus, conformational substates are an intrinsic feature CaM in solution.

One of the recurring themes in modern biology, namely, dynamics along with structure forms the basis of function of biomolecular systems is getting increasing level of support from various experimental and molecular dynamics simulation techniques. In this chapter, the power of time-resolved fluorescence spectroscopy in bringing to light various intricate aspects of DNA dynamics and, in some cases, their correlation with function has been shown. We believe that this is a very fruitful approach in seeking explanations for complex activity o f DNA based systems especially in the light of the enormous level of structural information being gathered in recent times.

Among the various atmospheric trace species that play a role in environmental issues, volatile halogenated alcanes have attracted considerable interest because of their massive industrial use and of their documented effects on global warming and ozone depletion. Whereas the monitoring of halogenated alcanes at or near ground level can be accomplished routinely using a variety of established techniques, their determination at higher altitude poses considerable technological and/or logistic challenges. One class of detection techniques that has been experiencing accelerated development in recent years is the use of laser sources to remotely excite and/or fragment the target molecules, followed by their identification and quantification using their optical emission. The purpose of this review is to describe the current status and future trends in remote detection of atmospheric halocarbons by laser-based spectroscopic techniques, with a special emphasis on the use of luminescence techniques to detect the analytes of interest.