Inner structure of isolated intact chloroplasts was observed for the first time by a method of laser scanning microscopy at the temperature of liquid nitrogen at 77 K. The microscope, based on gradient index optics, has a maximum resolution of 440 nm at the wavelength of 650 nm. Chloroplasts were excited into the Q-band of chlorophyll b by a krypton laser line at 647.6 nm and fluorescence was detected using two different interference filters. The 680 nm interference filter detects the regions where photosystem (PS) 2 mainly occurs, the 730 nm interference filter detects domains with predominant location of PS1. Since PS1 occurs mainly in stroma lamellae, whereas PS2 occurs mainly in grana regions we were able to view the structure of thylakoid membrane in isolated intact chloroplast that is the closest to in vivo state. and F. Vácha ... [et al.].
Low temperature phosphorescence, fluorescence and transient hole buming spectra of the photosystem 2 particles isolated from the cyanobacterium Synechococcus elongatus were measured. The role of photosynthetic activity was estimated by comparison of these spectroscopic methods. A model explaining chlorophyll fluorescence changes and both phosphorescence quantum efficiency increase and transient hole bimiing efficiency decrease connected with Chemical or heat photosynthetic deactivation is presented.