Specific photoisomerization of retinal in squid rhodopsin and metarhodopsin

The composition of retinal isomers in the photosteady-state mixtures formed from squid rhodopsin and metarhodopsin was determined by high-pressure liquid chromatography. A large amount of 9-cis-retinal was obtained at liquid N₂ temperature when rhodopsin was irradiated with orange light, but only small quantities of 9-cis-retinal were obtained at 15°C. Scarcely any 9-cis-retinal was produced from metarhodopsin by irradiation at liquid N₂ temperature. A large quantity of 7-cis-retinal was found in the photoproduct of rhodopsin irradiated at solid carbon dioxide temperature, but not at 15°C and liquid N₂ temperature. 7-cis-Retinal was not produced from metarhodopsin at any temperatures. These results indicate that the photoisomerization of retinal is regulated by the structure of the retinal-binding site of this protein. The formation of 9-cis- and 7-cis-retinals is forbidden in the metarhodopsin protein.     

Construction of a physical map of a kanamycin (Km) transposon, Tn5, and a comparison to another km transposon, Tn903

Summary A cleavage map of Tn5, a kanamycin (Km) transposon from plasmid JR67, was constructed from pMKI, a composite plasmid of ColE1 and Tn5, and compared to that of Tn903, a Km transposon from plasmid R6-5. The two transposons showed marked heterogeneity in both the structural gene for Km resistance and the inverted repeat regions as evidenced by their distinctly different restriction maps. This result suggests separate paths of evolution for the two Km transposons.     

Photoreaction of tyrosin-iodinated bacteriorhodopsin at low temperature

To elucidate the role of tyrosine residues in the shift of max and the light-driven proton pump of bacteriorhodopsin~ the photochemical reaction of tyrosine-iodinated bacteriorhodopsin (tyr-mod-bR) was investigated by low-temperature spectrophotometry. After 4–5 of 11 tyrosine residues of bacteriorhodopsin were iodinated, the meta-intermediate of tyr-mod-bR in 75% glycerol solution became so stable that its decay could be observed even at room temperature and i t was stable in the dark for several hours at –65°C.Four batho-intermediates were formed by irradiation with green light (500 nm) at –170°C. Like native bacteriorhodopsin, these batho-intermediates were photoreversible at –170°C. Four corresponding meta-intermediates were also formed by irradiation at –60°C. Using the difference spectra between meta-intermediates and tyr-mod-bR, the absorption spectra of four kinds of tyr-mod-bRs, batho-intermediates, and meta-intermediates were estimated. Each was at shorter wavelengths than that of its corresponding type in native bacteriorhodopsin. The results indicate that two or more tyrosine residues have some role in determining color in native bacteriorhodopsin.     

The synthesis,characterization, and preliminary biological evaluation of 1-β-D-arabinofuranosylcytosine-5′-diphosphate-L-1,2-dipalmitin

Recently, 1-β-$\text{D}$-arabinofuranosylcytosine-5′-diphosphate-$\text{DL}$-1,2-dipalmitin (VIa) was reported to inhibit the growth of L51784 cells in mice and of human colon carcinoma HCT-15 cells, also in mice. This paper describes the synthesis of a single diastereomer by conversion of 1-β-$\text{D}$-arabinofuranosylcytosine 5′-monophosphate (II) to the nucleoside 5′-phosphomorpholidate (III), followed by reaction with $\text{L}$-α-dipalmitoylphosphatidic acid (IV) to give 1-β-$\text{D}$-arabinofuranosylcytosine-5′-diphosphate-$\text{L}$-1,2-dipalmitin (V) in good yield. The separation of the product is described and its characterization by chromatography, elemental analysis, and spectroscopic methods. The lipophilic nature of V renders it insoluble in aqueous media and a method of sample preparation utilizing sonication techniques is described which provides a clear solution suitable for biological evaluation. In addition, the ability of V to inhibit the $\text{in}\text{vitro}$ growth of L1210 cells and of mouse myeloma MPC 11 cells is desscribed and compared with 1-β-$\text{D}$-arabinofuranosylcytosine (I) and other lipophilic prodrugs of I.     

Light-dependent development of thermoluminescence, delayed emission and fluorescence variation in dark-grown spruce leaves

Thermoluminescence profiles of spruce leaves grown under various light or dark conditions were measured after excitation at a low temperature (−70 to −20 °C) by 1-min illumination with red light, and the following results were obtained. Mature spruce leaves showed five thermoluminescence bands at −30, −5, +20, +40 (or +35) and +70 °C (denoted as Z_v, A, B₁, B₂ and C bands, respectively), but dark-grown spruce leaves with a similar chlorophyll content showed only two bands, at −30 and +70 °C (the Z_v and C bands) and were devoid of the three other bands (the A, B₁ and B₂ bands). On exposure of the dark-grown leaves to continuous red light, the A, B₁ and B₂ bands were rapidly developed, and the development was accompanied by enhancement of delayed emission, fluorescence variation and the Hill activity (photoreduction of 2,6-dichlorophenolindophenol with water as electron donor). It was demonstrated that the dark-grown spruce leaves are devoid of the water-splitting system in Photosystem II, and that the latent water-splitting activity is rapidly photoactivated by exposure of the leaves to continuous red light. These results on the gymnosperm spruce leaves, in which greening proceeds in complete darkness, being independent of the development of the water-splitting system in light, were discussed in relation to previous observations on angiosperm leaves, in which both greening and the activity generation proceed in the light.     

Multiple-flash development of thermoluminescence bands in dark-grown spruce leaves

Spruce leaves greened in darkness were devoid of three of the five thermoluminescence bands found for mature leaves. These bands were developed rapidly by exposure of the dark-grown leaves to continuous light. The development of these bands was studied by illumination with repetitive flashes at varied intervals. Flashes at intervals of 1 s were the most effective in inducing these bands. Those at shorter or longer intervals were less effective. It was deduced from these data that the development of these bands is a multiquantum process which involves at least two photo-events with a dark reaction between them.     

Adsorption of Vibrio parahaemolyticus onto Chitin and Copepods

Vibrio parahaemolyticus was observed to adsorb onto chitin particles and copepods. The efficiency of adsorption was found to be dependent on pH and on the concentration of NaC1 and other ions found in seawater. Highest efficiency was observed in water samples collected from Chesapeake Bay and lowest in water from the open sea. V. parahaemolyticus was found to adborb onto chitin with the highest efficiency of the several bacterial strains tested. Escherichia coli and Pseudomonas fluorescens did not adsorb onto chitin. The adsorption effect is considered to be one of the major factors determining the distribution of this species and affecting the annual cycle of V. parahaemolyticus in the estuarine system.     

Amino acid sequence of the alpha chain of chicken AI hemoglobin.

Adult chicken hemoglobin is heterogeneous and contains two major components, AI and AII (1). The amino acid sequence of the alpha chain of the AI component from white leghorns (small A type) was determined and compared with that of the alpha chain of the AII component, previously determined by the authors (2). An unexpectedly large difference of 65 amino acids was found between these two chains.