Manganese-histidine cluster as the functional center of the water oxidation complex in photosynthesis

The recent model of Kambara and Govindjee for water oxidation [Kambara T. and Govindjee (1985) Proc. Natl. Acad. Sci. U.S.A., 82:6119–6123] has been extended in this paper by examining all the data in order to identify the most likely candidate for the redox-active ligand (RAL), suggested to operate between the water oxidizing complex (WOC) and Z, the electron donor to the reaction center P680. We have concluded that a very suitable candidate for RAL is the imidazole moiety of a histidine residue. The electrochemical data available on imidazole derivatives play heavily in this identification of RAL. Thus, we suggest that histidine might play the role of an electron mediator between the WOC and Z. A model of S-states in terms of their plausible chemical identity is presented here.Abbreviations J electronic spin of ion - P680 reaction center chlorophyll - RAL Redox active ligand - S_n state of the oxygen-evolving system - WOC water oxidation complex - Z electron donor to P680 Dedicated to Prof. L.N.M. Duysens on the occasion of his retirement     

Flavonoids in the leaves of twenty-eight polygonaceous plants

Flavonoids in the leaves of twenty-eight species belonging to the Polygonaceae were studied. Thirty-three kinds of flavonoids were isolated, and eighteen kinds were obtained as crystals. Quercetin glycosides were commonly found in the family. In the quercetin glycosides, 3-O-rhamnoside was most frequently found: 3-O-glucuronide is also distributed widely. Myricetin glycosides were rare. Methylated flavonols were found in some species of the sectionsEchinocaulon andPersicaria. Eleven kinds ofC-glycosylflavones were found in the present survey, andC-glycosylflavones were distributed in all species of the genusRheum and in almost all species of the section Tiniaria.Rumex Acetosella andPolygonum suffultum are exceptional, the former contains flavone glycoside and the latterC-glycosylflavones only, as main components.     

Interaction of glycylglycine and Na+ at the mucosal border of Guinea-pig small intestine: A non-mutual stimulation of transport

Sodium-dependence of glycylglycine (Gly-Gly) influx and stimulation of Na⁺ transport by Gly-Gly were studied in everted sacs, sheet preparations and brush-border membrane vesicles isolated from guinea-pig ileum. Gly-Gly influx was found to be independent of the presence of Na⁺, while Na⁺ transport was stimulated by Gly-Gly as evidenced by increases in transmural potential difference (PD_t), short-circuit current (I_sc) and Na⁺ influx. The change in PD_t (ΔPD_t) induced by Gly-Gly was a saturable function of Gly-Gly concentration, showing a Michaelis-Menten type relationship. The half-saturation concentration for Gly-Gly estimated from the electrical data was nearly identical with that estimated from influx data. At a constant Gly-Gly concentration the relationship between I_sc and Na⁺ concentration was sigmoid, and the Hill coefficient was 1.5. Kinetic analysis according to Garay Garrahan indicates that each Gly-Gly carrier has two equivalent non-interacting binding sites for Na⁺, and that translocation of Na⁺ occurs when the two Na⁺ sites on the carrier loaded with Gly-Gly are occupied by Na⁺. However, our results indicate that the resultant Na⁺ flow is not capable of stimulating Gly-Gly translocation.     

Variations of Natural 13C Abundances in Leguminous Plants

The natural ¹³C abundance (¹³C value) of the field-grown leguminousplants (soybean, kidney bean, pea, azuki bean, mung bean, peanutand cowpea) was investigated by mass spectrometry with a precisionbetter than %0.2 for ¹³C. Among organs of premature plants,the leaves had the most negative values, and the nodules generallyhad the least negative values, and other organs, fruits, stemsand roots, showed intermediate values. In the soybeans so farinvestigated, the grains of nodulating plants exhibited higher¹³C values than nonnodulating lines. The ¹³C values of the grainsvaried depending on the species: peanuts showed the most negativevalues. Possible causes underlying these variations are discussed. ³Institute of Biological Sciences, University of Tsukuba, Sakura-mura,Ibaraki 305, Japan. (Received December 3, 1982; Accepted May 25, 1983)     

Interindividual distance and influence of dominance on feeding in a natural Japanese macaque troop

In a natural troop of Japanese macaques (Macaca fuscata yakui), the dominant-subordinate relationship restricted the feeding behavior of the subordinate in two ways: (1) the dominant drives away the subordinate through agonistic interactions; and (2) the subordinate avoids approaching the dominant without any agonistic interactions. These occurred only infrequently, and only when an interindividual distance was less than a certain distance, which is called the “tolerance/intolerance” (T/I) distance. On the other hand, the usual interindividual distance when feeding was much greater than the T/I distance. Therefore dominance has little influence on feeding in the study troop. In the study troop, the T/I distance between kin-related females was shorter than that between unrelated individuals. Although this difference may facilitate kin selection if the troop faces severe competition over concentrated food, the difference does not seem to influence survival or reproductive rate in the study troop.     

Adenosine 3′,5′-Cyclic Monophosphate-Deficient Mutants of Vibrio cholerae

Two adenosine 3',5'-cyclic monophosphate (AMP)-deficient mutants of Vibrio cholerae (biotype El Tor) were successfully isolated by nitrosoguanidine treatment followed by pencillin screening for pleiotropic sugar-negative clones. Exogenous cyclic AMP is required for the fermentation of sucrose, trehalose, fructose, maltose, and mannose but not of glucose, as well as for the formation of normal flagella and specific somatic antigens. A striking characteristic of the mutants is their growth behavior at higher temperatures. They cannot grow on TCBS selective plates at 37 C or higher unless they are provided with a supply of exogenous cyclic AMP, although they are capable of producing colonies on the same medium, even without cyclic AMP, at temperatures lower than 30 C. Since the mutants are converted to spheroplasts, spindle forms, and spiral filaments in cyclic AMP-free media at 37 C, and this phenomenon is stopped by the addition of cyclic AMP or a combination of 20% sucrose and 0.2% magnesium chloride, it is assumed that cyclic AMP is essential for the synthesis of the cell wall of V. cholerae at higher temperatures.     

Mutants of Group D1Salmonella Carrying the Somatic Antigen of Group A Organisms: Isolation and Serological Characterization

O antigen mutants were obtained from Salmonella durban, a group D(1) organism, by treatment with N-methyl-N'-nitro-N-nitrosoguanidine. Serological studies demonstrated that the mutants lost the O-9 antigen factor of the parent organism but acquired the O-2 factor specific to group A Salmonella. Lipopolysaccharides of the mutant strains contained paratose which determines the specificity of O-2 factor. Tyvelose, present in the wild-type lipopolysaccharide, was not found in the mutants. H antigens and other biological characteristics of the mutant strains were the same as those of the wild-type organism. The present finding implies that group A Salmonella species might be derived from group D(1) organisms.     

Plant regeneration from isolated microspore cultures of Chinese cabbage (Brassica campestris spp. pekinensis)

Isolated microspores of Chinese cabbage (Brassica campestris ssp. pekinensis) were incubated in modified NN medium containing 10% sucrose in darkness at 33°C for one day followed by culture at 25°C. After 14 days of culture, microspores developed into embryos ranging from globular to cotyledonary stage. Plants were regenerated after transfer of embryos to medium containing 3% sucrose and no plant growth regulators.Abbreviations NN Nitsch and Nitsch - MS Murashige and Skoog - NAA naphthaleneacetic acid - BA 6-benzylaminopurine