An all solidstate nearinfrared timecorrelated single photon counting instrument for dynamic lifetime measurements in DNA sequencing applications Rev.Single quantum well light emitting diodes demonstrated as excitation sources for nanosecond phasemodulation fluorescence lifetime measurements Rev.

The ability to observe the behavior of living cells and tissues provides unparalleled access to information regarding the organization and dynamics of complex cellular structures. While great strides have been made over the past 30 to 40 years in the design and application of a variety of novel optical microscopic techniques, until recently, it has not been possible to image biological phenomena that occur over very short time periods (nanosecond to millisecond) or over short distances (10 to 1000 Å). However, the recent combination of (1) very rapidly gated and sensitive image intensifiers and (2) the ability to deliver fluorescence excitation energy to intact living biological specimens in a pulsed or sinusoidally modulated fashion has allowed such measurements to become a reality through the imaging of the lifetimes of fluorescent molecules. This capability has resulted in the ability to observe the dynamic organization and interaction of cellular components on a spatial and temporal scale previously not possible using other microscopic techniques. This paper discusses the implementation of a fluorescence lifetime imaging microscope (FLIM) and provides a review of some of the applications of such an instrument. These include measurements of receptor topography and subunit interactions using fluorescence resonance energy transfer (FRET), fluorescence anisotropy of phospholipids in cell membranes, cytosolic free calcium (Ca2+)i and the detection of human papillomavirus (HPV) infection in clinical cervicovaginal smears.

We describe the construction and emission characteristics of a gap-adjustable, capacitor-replaceable pulsed light source (air-discharge type) that produces high-repetition pulsed UV light of nanosecond duration. Stable light pulses of 0.8 to 3.5 ns width are generated from atmospheric-pressure air discharge between the sharp anode and round cathode. Appreciable heterogeneities on the distribution of emission intensity and its on-set timing along the discharge gap were observed. Fluorescence lifetimes of ethidium bromide solutions were measured to demonstrate the usefulness of the light source.

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