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81.
Adolfo H. Mü ller Paulo C. Vieira M. F tima das G.F.da Silva Jo o B. Fernandes 《Phytochemistry》1995,40(6):1797-1800
Two novel dihydrochalcones, 2′,3,4′,6′-tetrahydroxy-4-methoxy-3′,5-di-(3,3-dimethylallyl)-dihydrochalcone and 2′,.3,6′-trihydroxy-4-methoxy-5-(3,3-dimethylallyl)-3′,4′-(2″,2″-dimethyldihydropyran)-dihydrochalcone, have been isolated from fresh fruits of Metrodorea nigra. Stems and leaves showed a similar composition and we have isolated common steroids, simple coumarins, several furocoumarins, furoquinoline alkaloids and a furofuran lignan. From stems, we have also isolated the pentacyclic 6-C-monoterpenyl-5,7-dioxycoumarin, deoxybruceol. Structures of the isolated compounds were elucidated on the basis of spectral data. 相似文献
82.
Quintilio W. Sato R.A. da Silveira A.M. Barratt G. Fattal E. Bueno-da-Costa M.H. 《Biotechnology Techniques》1997,11(9):697-700
The advantages of the intrinsic fluorescence of the tryptophan and the absorbance of the methionine residues of the 18 kDa-hsp - a recombinant protein from Mycobacterium leprae - was exploited here to develop a sensitive and low costs method for protein assaying. They presented linearity between 3 and 1000 g of protein. The correlations between intrinsic fluorescence or absorbance at 230 nm and protein contents were both superiors to 0.99. These methods can be extended to others proteins with low aromatic residue contents. 相似文献
83.
The phylogenetic distribution of transposable families, P, gypsy, hobo, I, and mariner has been analyzed in 33 species of
11 groups of neotropical Drosophila and a Drosophilidae species Zygotrica vittimaculosa, using squash blot and dot blot. Genomic
DNA of almost all neotropical species tested hybridized with gypsy probe and some species showed a particularly strong hybridization
signal, as D. gaucha, D. virilis, and species of flavopilosa group. The hobo element was restricted to melanogaster group
and some strains of D. willistoni. Only D. simulans DNA showed hybridization to mariner probe in all species tested and D.
simulans and D. melanogaster showed hybridization with I element probe. P element homologous sequence was present in D. melanogaster
and all species and strains of the willistoni and saltans groups tested. The presence of at least one P-homologous sequence
was detected in Drosophila mediopunctata. This one was the only P-bearing species of all six tested from the tripunctata group.
Four different pairs of primers homologous to segments of the canonical sequence of D. melanogaster's P were used to amplify
specific sequences from D. mediopunctata DNA, showing the occurrence of seemingly well-conserved P-homologous sequences.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
84.
Characterization of novel long-chain 1,2-diols in Thermus species and demonstration that Thermus strains contain both glycerol-linked and diol-linked glycolipids.
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R Wait L Carreto M F Nobre A M Ferreira M S da Costa 《Journal of bacteriology》1997,179(19):6154-6162
In this study, we purified and characterized tetra- and triglycosyl glycolipids (GL-1 and GL-2, respectively) from two different colonial forms of Thermus scotoductus X-1, from T. filiformis Tok4 A2, and from T. oshimai SPS-11. Acid hydrolysis of the purified glycolipids liberated, in addition to the expected long-chain fatty acids, two components which were identified by gas chromatography-mass spectrometry as 16-methylheptadecane-1,2-diol and 15-methylheptadecane-1,2-diol. Fast atom bombardment mass spectrometry of the intact glycolipids indicated that a major proportion consisted of components with glycan head groups linked to long-chain 1,2-diols rather than to glycerol, although in all cases glycerol-linked compounds containing similar glycan head groups were also present. As in other Thermus strains, the polar head group of GL-1 from T. filiformis Tok4 A2 and from T. scotoductus X-1 colony type t2 was a glucosylgalactosyl-(N-acyl)glucosaminylglucosyl moiety. However, GL-2 from T. scotoductus X-1 colony type t1 and from T. oshimai SPS-11 was a truncated analog which lacked the nonreducing terminal glucose. Long-chain 1,2-diols have been previously reported in the polar lipids of Thermomicrobium roseum and (possibly) Chloroflexus aurantiacus, but to our knowledge, this is the first report of their detection in other bacteria and the first account of the structural determination of long-chain diol-linked glycolipids. 相似文献
85.
In total, 86 enterococcal strains including representatives of most of the described species were tested for the ability to agglutinate human, sheep, and rabbit erythrocytes. Five strains did not react with any of the erythrocytes tested, and 81 (94.2%) strains agglutinated only rabbit erythrocytes. The hemagglutination titers ranged from 2 to 64. Loss of the hemagglutination activity was observed when rabbit erythrocytes were treated with trypsin or neuraminidase. Trypsin treatment of the bacterial suspensions also caused loss of the agglutination ability. On the other hand, heat treatment of bacterial suspensions increased the efficiency of the interactions, and higher titers were obtained. Assays for inhibition of hemagglutination were performed with -d-fucose, -d-galactose, -d-galactose, d-glucose, N-acetyl-galactosamine, N-acetyl-glucosamine, N-acetylneuraminic acid, N-acetylneuraminic acid-lactose, and fetuin. Only fetuin was able to inhibit the hemagglutination reactions. The results showed that hemagglutination properties are common to the different enterococcal species tested. They also suggest that enterococci possess hemagglutinins of proteic and non-proteic nature that are involved in the attachment to sialic acid-containing receptors on the surface of rabbit erythrocytes. 相似文献
86.
The Drosophila neuromusculin (nrm) gene encodes an immunoglobulin-like (Ig-like) cell adhesion molecule expressed in the precursors of the embryonic peripheral nervous system (PNS), in the midline precursors of the central nervous system (CNS), and in muscles. During the initial phases of CNS axonogenesis, nrm is expressed in cells involved in the development of commissures and longitudinal tracts. Mutations which alter expression of nrm mRNAs cause aberrant development of commissures and longitudinal axon pathways. Defects in the PNS and muscles of nrm mutants are also observed. In most nrm embryos, abnormal development can be detected in a subset of abdominal segments; however, in approximately 1 of 10 nrm embryos, the defects extend to all segments. Herein, we present evidence that nrm plays an important role in early morphogenesis, possibly by mediating or facilitating inductive cell contacts and movements. 相似文献
87.
Gustavo A. Bouchardet da Fonseca Thomas E. Lacher Jr. 《Primates; journal of primatology》1984,25(4):441-449
We report the exudate feeding behavior of two groups of marmosets (Callithrix jacchus penicillata) living permanently in Cerradão, a common woodland formation of Central Brazil. Cerradão is an open canopy formation and marmosets must occasionally descend to the ground in order to move from tree to tree. Even in atypical habitat, exudate eating is the predominant foraging activity. Marmosets are engaged in exudate collection over 70% of the total time spent feeding. They were observed gnawing on seven species of trees, and consumed exudates from four of these species. We compared the degree of utilization of the exudate sources, and examined a number of different characteristics of the exudates. Morphological adaptations that allow for the exploitation of the “exudate-eater niche” may be an important component of the adaptability ofCallithrix marmosets. 相似文献
88.
A procedufe is described for the isolation of flagella of Crithidia fasciculata, Herpetomonas samuelpessoai and Leishmania tarentolae in a highly purified state and giving reasonably good yield. The 3 types of flagella give a similar electrophoretic pattern of proteins. It is shown that H. samuelpessoai and, to a lesser extent, C. fasciculata flagella confer protection against Trypanosoma cruzi infection. 相似文献
89.
A. van Rotterdam F. H. Lopes da Silva J. van den Ende M. A. Viergever A. J. Hermans 《Bulletin of mathematical biology》1982,44(2):283-305
A linear spatially distributed model of a chain of neurons and interneurons was investigated in relation to the generation
of propagated alpha rhythmic activity. It was assumed that the elements of the chain were interconnected by means of recurrent
collaterals and inhibitory fibres in such a way that the connectivity functions were assumed to be homogeneous and their strength
was an exponentially decreasing function of distance. It was found that such a neuronal chain shows propagation properties
for frequencies in the alpha band. The results obtained with the model are in agreement with the phase velocities encountered
experimentally. In this way, it was possible to estimate the length of the neural fibres responsible for the phenomenon of
propagated activity. The estimates obtained are in good agreement with recent quantitative neuroanatomical data on the circuitry
of the neocortex. 相似文献
90.
Low angle X-ray diffraction patterns were recorded from crab leg muscle in living resting state and in rigor (glycerol-extracted). Both resting and rigor patterns showed a series of layer-lines arising from a helical arrangement of actin subunits in the thin filaments. In the resting state, the crossover repeat of the long-pitch actin helices was 36.6 nm, and the symmetry of the genetic actin helix was an intermediate between and . When the muscle went into rigor, the crossover repeat changed to 38.3 nm and the helical symmetry to .In the living resting pattern, six other reflections were observed on the meridian and in the near-meridional region. These were indexed as orders of 2 × 38.2 nm and could be assigned to troponin molecules; the spacings and the intensity distributions of these reflections could be explained by the model proposed by Ohtsuki (1974) for the arrangement of troponin molecules in the thin filaments.The muscle in rigor gave meridional and near-meridional reflections at orders of 2 × 38.3 nm. These were identified as the same series of reflections as was assigned to troponin in the living resting pattern, but were more intense and could be seen up to higher orders. We consider that the myosin heads attached to the thin filament at regular intervals along its axis also contribute to these reflections in the rigor pattern. 相似文献