Crystallization and preliminary X-ray and optical spectroscopic characterization of the photochemical reaction center from Rhodobacter sphaeroides strain 2.4.1

The photochemical reaction center from Rhodobacter sphaeroides 2.4.1 has been crystallized. The crystals were obtained in a solution of beta-octylglucoside by the vapor diffusion technique using polyethylene glycol 4000 as the precipitant at 22 degrees C. The orthorhombic crystals (space group P2(1)2(1)2(1)) have cell constants a = 142.5 A, b = 136.1 A, c = 78.5 A, and diffract to 3.7 A. The crystals display pronounced linear dichroism in the carotenoid absorption spectral region.     

Interrelatedness of 5S RNA sequences investigated by correspondence analysis

Summary Correspondence analysis (a form of multivariate statistics) applied to 74 5S ribosomal RNA sequences indicates that the sequences are interrelated in a systematic, nonrandom fashion. Aligned sequences are represented as vectors in a 5N-dimensional space, where N is the number of base positions in the 5S RNA molecule. Mutually orthogonal directions (called factor axes) along which intersequence variance is greatest are defined in this hyperspace. Projection of the sequences onto planes defined by these factorial directions reveals clustering of species that is suggestive of phylogenetic relationships. For each factorial direction, correspondence analysis points to regions of importance, i.e., those base positions at which the systematic changes occur that define that particular direction. In effect, the technique provides a rapid determination of group-specific signatures. In several instances, similarities between sequences are indicated that have only recently been inferred from visual base-to-base comparisons. These results suggest that correspondence analysis may provide a valuable starting point from which to uncover the patterns of change underlying the evolution of a macromolecule, such as 5S RNA.     

Submarine foraging behavior of alcids in an artificial environment

We used an artificial environment at Sea World, Inc, San Diego, to study underwater foraging behavior of alcids. Larger birds dove longer and had greater wingbeat frequencies. The pigeon guillemot Cepphus columba was the only species to use both feet and wings for propulsion; all others used just wings. Aggressive interactions underwater were common. Competition among alcids in the wild may occur primarily underwater, and artificial environments may be the best means to study such interactions.     

Feeding responses to solanaceous allelochemicals by larvae of the tobacco hornworm, Manduca sexta

Feeding responses of the oligophagous tobacco hornworm to allelochemicals prevalent in their host plants were determined in food choice-tests using filter paper discs laced with a test solution or water (control). Six solanaceous alkaloids, tomatine, tomatidine, solanine, solanocapsine, atropine and nicotine, were tested and only tomatine and solanocapsine were found to influence preference behavior. Solanocapsine (5 mM) deters feeding whereas tomatine (1 mM) stimulates feeding slightly. No synergistic effect of either tomatine or tomatidine with sucrose was found.The responses to tomatine are affected by previous feeding experience. Tomatine slightly stimulates feeding in larvae reared on tomato (Lycopersicon esculentum), but slightly deters feeding in larvae reared on Jerusalem cherry (Solanum pseudocapsicum). Such induced preference is absent for the other alkaloids tested, which indicates that these alkaloids do not by themselves induce preferences for the plants containing them.The non-alkaloid allelochemicals, chlorogenic acid, rutin, and 2-tridecanone also influenced food choice behavior. Chlorogenic acid is slightly stimulatory at its natural concentration (1mM), but strongly deterrent at higher concentrations. Rutin stimulates feeding in a concentration-dependent manner. Its activity must be due to the glycosylated structure, because both the aglycone (quercetin) and the sugar moiety (rutinose) are neutral. Removal of the glucose part of rutin, as in quercitrin, results in feeding deterrent activity. 2-Tridecanone is neutral at its concentration in cultivated tomato (1 mM), but strongly deterrent and toxic at higher concentrations. Preference behavior is not affected by solanesol, GABA, and a mixture of host plant compounds stimulatory for anothe solanaceous-specific feeder, the Colorado potato beetle (Leptinotarsa decemlineata).We conclude that the prevalent solanaceous alkaloids and other allelochemicals tested do not play important roles in food selection of the tobacco hornworm, although some may make small contributions.

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Résumé Des experiences de choix de chenilles oligophages de M. sexta ont été réalisees avec des disques de papier filtre imbiles d'eau ou de solutions des substances allélochimiques dominantes dans les plantes consommées. Sur les six alcaloïdes de solanées examinés: tomatine, tomatidine, solanine, solanocapsine, atropine et nicotine, seuls la tomatine et la solanocapsine ont influé sur le choix; la solanocapsine (5 mM) empêche la prise de nourriture, tandis que la tomatine (1 mM) la stimule légèrement. Aucun effet synergique de la tomatine ou de la tomatidine n'a été observé en présence de sucrose.La réponse à la tomatine est modifiée par la prise de nourriture antérieure. Elle stimule légèrement l'alimentation de chenilles élevées sur tomates (Lycopersicon esculentum), mais dissuade légèrement les chenilles élevées sur Solanum pseudocapsicum. II n'y a pas d'action induite semblable avec les autres alcalïdes examinés, ce qui indique que ces alcaloïdes ne peuvent pas induire par eux-mêmes de préférences pour les plantes qui les contiennent.Des substances allélochimiques non-alcaloïdes: acide chlorogénique, rutine, et 2-tridécanone, influent aussi sur le comportement de choix alimentaire. L'acide chlorogénique est légèrement stimulant à sa concentration naturelle (1 mM), mais fortement dissuasif aux concentrations supérieures. La rutine stimule la prise de nourriture en fonction de sa concentration. Son activité doit être due à sa structure glucosylate, puisqu'aussi bien l'aglycone (quercitine) que la moiteé sucrée (rutinose) sont neutres. La suppression de la partie glucose de la rutine, comme dans le cas de la quercitine, a un effet dissuasif. A sa concentration dans la tomate cultivée (1 mM), le 2-tridécanone est neutre, mais il est fortement dissuasif et toxique à des concentrations supérieures.Le comportement de choix n'est pas modifié par le solanésol, le GABA, et par un mélange de composés végétaux stimulant un consommateur spécifique de solanées, comme le doryphore (Leptinotarsa decemlineata).Nous pouvons conclure que les principaux alcaloïdes et autres substances allélochimiques des solanées que nous avons examinés n'interviennent pas d'une façon importante, mais peuvent avoir une influence secondaire, dans les choix alimentaires de Manduca sexta.

     

Biochemical characterization of polypeptide components involved in neurite fasciculation and elongation

Polypeptide components and carbohydrate linkage types of F11 antigen and G4 antigen, two chick cell-surface glycoproteins implicated in neurite fasciculation and elongation [Rathjen, F.G., Wolff, J.M., Bonhoeffer, F. and Rutishauser, U. (1987) J. Cell Biol. 104, 343-353], have been studied in comparison to mouse L1 antigen. Tryptic fingerprint analysis does not reveal any relation of the 130-kDa components of G4 or F11 antigens to each other or to neural cell-adhesion molecules. The 180/190-kDa component of G4 antigen comprises parts of the 130-kDa and 80/65-kDa components and shares a sequence corresponding to the amino terminus of the G4 130-kDa component as shown serologically with anti-peptide sera. This closely parallels the relationship found for mouse L1 antigen components. In contrast, the F11 170-kDa component is different from the F11 130-kDa component, as shown serologically and by fingerprint analysis. A combination of chemical and enzymatic deglycosylation methods reveals that while O-glycosylation cannot be detected F11 130-kDa, G4 130-kDa and L1 140-kDa components contain N-linked carbohydrates. Endoglycosidase H treatment shows that the oligosaccharides present in the G4 130-kDa component and mouse L1 are mostly of the complex type, while the F11 130-kDa component consists of two populations, one containing mainly complex-type carbohydrates and a second containing high-mannose/hybrid-type carbohydrates.     

N-Deacetylation of 2-acetamido-2-deoxy-hexosecontaining oligosaccharides and polysaccharides by calcium in liquid ammonia

N-Deacetylation of 2-acetamido-2-deoxy-hexose residues is accomplished in liquid ammonia containing calcium. Oligosaccharides, lacto-N-fucopentaose II and lacto-N-difucohexaose I, containing 3,4-disubstitutedN-acetylhexosamine residues are quantitativelyN-deacetylated. When applied to polysaccharides, however, only partialN-deacetylation was achieved.Author for correspondence. AXRD     

Puromycin enhances 20-hydroxyecdysone-induced protein synthesis in wing discs of Drosophila melanogaster

The effect of cycloheximide and puromycin on 20-hydroxyecdysone-induced protein synthesis in wing discs of Drosophila melanogaster has been studied by one-dimensional and two-dimensional SDS polyacrylamide electrophoresis. It is found that puromycin, but not cycloheximide, when applied simultaneously with the hormone enhanced the hormone-induced synthesis of the early and late proteins. However, when puromycin was applied after hormone treatment, only the late proteins were induced. The possible implication of these observations is discussed.     

Localization of ornithine decarboxylase in the chick embryo during organogenesis

Summary The localization of ornithine decarboxylase (ODC), a key enzyme in polyamine biosynthesis and thus in cell growth, was determined in the 4.5-day-old chick embryo, using two independent methods of analysis. ODC protein was identified by indirect immunofluorescence with a monospecific ODC antibody, and catalytically active ODC was identified by autoradiography with -(5-³H) difluoromethylornithine. Both methods revealed a basically similar distribution of ODC within the embryo. Among the organs, the brain exhibited the highest ODC levels. ODC levels were also high in spinal cord, mesonephric tubules and heart. Similar levels, but confined to limited areas, were found in liver tissue, head mesenchyme, and the oral and pharyngeal regions. Organs that exhibited high ODC levels are all engaged in rapid growth, as well as in extensive tissue remodeling and differentiation.     

Crystal structure analysis of an A-DNA fragment at 1.8 A resolution: d(GCCCGGGC).

Single crystals of the self-complementary octadeoxyribonucleotide d(GCCCGGGC) have been analysed by X-ray diffraction methods at a resolution of 1.8 A. The tetragonal unit cell of space group P4(3)2(1)2 has dimensions of a = 43.25 A and c = 24.61 A and contains eight strands of the oligonucleotide. The structure was refined by standard crystallographic techniques to an R factor of 17.1% using 1359 3 sigma structure factor observations. Two strands of the oligonucleotide are related by the crystallographic dyad axis to form a DNA helix in the A conformation. The d(GCCCGGGC) helix is characterized by a wide open major groove, a near perpendicular orientation of base pairs to the helix axis and an unusually small average helix twist angle of 31.3 degrees indicating a slightly underwound helix with 11.5 base pairs per turn. Extensive cross-strand stacking between guanine bases at the central cytosine-guanine step is made possible by a number of local conformational adjustments including a fully extended sugar-phosphate backbone of the central guanosine nucleotide.