The biochemistry and circadian regulation of luminescence in two Pyrocystis species, P. lunula Hulburt and P. noctiluca Murray et Haeckel, were compared with a wellstudied species, Gonyaulax polyedra Stein. All exhibit circadian rhythms and all have similar luciferins and luciferases. However, the Pyrocystis species lack a second protein involved in the reaction in Gonyaulax, the luciferin (substrate) binding protein, which sequesters the luciferin at the cytoplasmic pH and releases it upon acidification, thus controlling the characteristic flashing, which is similar in the three species. More striking is the difference in the circadian regulation of luminescence, which in Gonyaulax involves the daily synthesis and destruction of the two proteins, along with the luminous organelles (scintillons) from which light is emitted, and which are present in all species. In the Pyrocystis species, the amount of luciferase is the same in extracts made during the day and night phases; its circadian regulation in vivo may be attributed to a change in its localization from day to night phase.

The implementation of efficient technologies for the production of recombinant mammalian proteins remains an outstanding challenge in many structural and functional genomics programs. We have developed a new method for rapid identification of soluble protein expression in E. coli, based on a separation of soluble protein from inclusion bodies by a filtration step at the colony level. The colony filtration (CoFi) blot is very well suited to screen libraries, and in the present work we used it to screen a deletion mutagenesis library.

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Three different chlorophyll (chl) c‐type pigments were isolated from two cryptophyte species by silica thin‐layer chromatography or polyethylene high‐performance liquid chromatography. Chroomonas sp. Hansgirg contained chl c1 and magnesium‐2,4‐divinylpheoporphyrin a, mono‐methylester; chl c2 and magnesium‐2,4‐divinylpheoporphyrin a5 monomethylester were found in Cryptomonas maculata (syn. Rhodomonas maculata Butcher). These identifications were based on spectral characteristics and on comparison with reference pigments isolated from the synurophycean Synura petersenii Korshikov and the prasinophyte Mantoniella squamata Manton & Park. Neither of the cryptophyte species contained chl c1 and chl c2. The significance of chl c1 as a major pigment and the occurrence of magnesium‐2,4‐divinylpheoporphyrin a5 monomethylester in cryptophytes are discussed.

The NADPH-protochlorophyllide oxidoreductase, an enzyme catalysing the light-driven conversion of protochlorophyllide to chlorophyllide, was studied in the greening mutant C- 2A′ of the unicellular green alga Scenedesmus obliquus. Studies of the enzyme activity in vitro showed strong dependence on the presence of glycerol and the detergent Triton X-100. Prerequisite for the formation of a photoactive enzyme complex is a sufficient preincubation time with the substrates PChlide and NADPH. A continuous assay system, reading the absorbance increase at the wavelength of chlorophyllide, was used to determine the kinetic constants. The Km value for NADPH is 4.2 μᴍ, the Vmax is 5.9 pmol · s-1. The Km and Vmax for protochlorophyllide are 0.19 μᴍ and 6.5 pmol · s-1, respectively. The pH-dependence of the reaction exhibits a broad maximum between pH 7-8.5 typically for an enzyme active during chloroplast development, when pH-changes might be expected. The obtained kinetic data outline that the light dependent formation of chlorophyll in vivo is not limited by the substrates PChlide and NADPH, indicating that only light is the triggering factor in the very early greening process.

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Dark‐grown cells of mutant C‐2A' of Scenedesmus obliquus accumulate monovinyl‐and mainly divinyl‐protochlorophyllide (PChlide). Both PChlide‐forms are equally well photoconverted in vitro by the NADPH‐protochlorophyllide oxidoreductase of the light‐dependent greening mutant C‐2A’of Scenedesmus obliquus. The chlorophyllide (Chlide) resulting from this photoconversion in vivo has a predominantly monovinyl character. Only small traces of a transient Chlide‐form with divinyl fluorescence could be detected.