The modular JTS-100 spectrometer (BioLogic; www.biologic.net) designed for the use of many combinations of light sources and detection, enables measurements of absorbance changes in leaves, cells, and isolated thylakoid membranes which assess the redox kinetics of cytochromes, plastocyanin, and P700 (photosystem I) or the electrochromic shift for determination of cyclic electron transport, photosystem stoichiometry, and the proton motive force. The JTS-100 is an LED-based pump-probe spectrophotometer, also capable of measuring fluorescence. The instrument consists of an electronic controller and a top-bench optical module. The electronic control module sets the timing and intensity for the LED light sources and controls the timing of samples recorded from the photodiode detectors. The JTS is designed for investigation of the events in the microsecond time range as well as from 1 ms to minutes or hours. The other critical innovation of the Joliot type spectrometer is the ability to account for light scattering.

Addition of a laser from Continuum enables calibration of fluorescence and absorption change measurements (Rappaport F et al., BBA (2007) 1767, 56–65; Joliot P&A, BBA (2008) 1777, 676–683). It is equipped with a dye cavity from JBeamBio to excite in a region of the light spectrum (red, 640 nm) outside the region of interest for detection (520 nm). This set-up allows saturation on a nanosecond time scale, thus inducing single turnovers of light reactions. Being able to perform this measurement provides a reliable and functional reference (photosystem charge separation), as opposed to a normalization based on same quantity of leaf material for example that disregards whether or not electron transfer components are active.

Location: room B3.44.49