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61.
9-beta-D-Arabinofuranosyl-8-n-butylaminoadenine, a C-8 substituted nucleoside in the anti conformation. Crystallographic and NMR studies 总被引:1,自引:0,他引:1
S Neidle M R Sanderson A Subbiah J B Chattopadhyaya R Kuroda C B Reese 《Biochimica et biophysica acta》1979,565(2):379-386
The protein NMR spectrum of 9-beta-D-arabinofuranosyl-8-n-butylaminoadenine shows an unusually low-field 5'-hydroxyl proton resonance, which has been interpreted in terms of an anti glycosidic conformation together with an 05' ... N8 intramolecular hydrogen bond. Confirmatory evidence for this was obtained by an X-ray crystallographic study; in the crystal, the glycosidic angle chi is 52.7 degrees and the sugar pucker is C3' endo-C4' exo. 相似文献
62.
Dewey Ryu R. Andereotti M. Mandels B. Gallo E. T. Reese 《Biotechnology and bioengineering》1979,21(11):1887-1903
By employing a two-stage continuous-culture system, some of the more important physiological parameters involved in cellulose biosynthesis have been evaluated with an ultimate objective of designing an optimally controlled cellulose process. The two-stage continuous-culture system was run for a period of 1350 hr with Trichoderma reesei strain MCG-77. The temperature and pH were controlled at 32°C and pH 4.5 for the first stage (growth) and 28°C and pH 3.5 for the second stage (enzyme production). Lactose was the only carbon source for the both stages. The ratio of specific uptake rate of carbon to that of nitrogen, Q(C)/Q(N), that supported good cell growth ranged from 11 to 15, and the ratio for maximum specific enzyme productivity ranged from 5 to 13. The maintenance coefficients determined for oxygen, MO, and for carbon source, MC, are 0.85 mmol O2/g biomass/hr and 0.14 mmol hexose/g biomass/hr, respectively. The yield constants determined are: YX/O = 32.3 g biomass/mol O2, YX/C = 1.1 g biomass/g C or YX/C = 0.44 g biomass/g hexose, YX/N = 12.5 g biomass/g nitrogen for the cell growth stage, and YX/N = 16.6 g biomass/g nitrogen for the enzyme production stage. Enzyme was produced only in the second stage. Volumetric and specific enzyme productivities obtained were 90 IU/liter/hr and 8 IU/g biomass/hr, respectively. The maximum specific enzyme productivity observed was 14.8 IU/g biomass/hr. The optimal dilution rate in the second stage that corresponded to the maximum enzyme productivity was 0.026 ~ 0.028 hr?1, and the specific growth rate in the second stage that supported maximum specific enzyme productivity was equal to or slightly less than zero. 相似文献
63.
Plasmodium falciparum: loss of knobs on the infected erythrocyte surface after long-term cultivation. 总被引:5,自引:0,他引:5
After long-term in vitro cultivation in human erythrocytes, variants of three strains of the malaria parasite Plasmodium falciparum no longer produce the “knob” alterations on the host erythrocyte surface. The time in continuous culture before knobs failed to appear ranged from 18 months for the Gambian strain FCR-4 to 33 months for the Vietnamese strain FCR-1. The loss of knobs is correlated with the inability to concentrate trophozoites, schizonts, and segmenters from these variant lines by the use of gelatin-containing media. This is the first report of a change in Plasmodium falciparum or its host cell as a consequence of long-term culture. 相似文献
64.
Defective bud formation in human cells chronically infected with subacute sclerosing panencephalitis virus. 总被引:3,自引:1,他引:2
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Human prostate cells chronically infected with the Mantooth strain of subacute sclerosing panencephalitis (SSPE) virus multiply normally, fuse only occasionally to form giant cells, and yet have twisted intracytoplasmic nucleocapsids. These cells are able to support replication of vesicular stomatitis virus, although they release only small amounts of SSPE virus. To determine why carrier cells do not produce virus, they were examined with techniques for surface replication, freeze-fracturing, and immunoperoxidase labeling with SSPE antibody. The surface of carrier cells, like that of productive cells, is characterized by ridges crowned with viral antigens and devoid of the intramembrane particles revealed by freeze-fracture techniques. Since surface ridges form where nucleocapsids attach to the membrane, the shape and length of ridges are indicative of the shape and length of the underlying nucleocapsid. Whereas ridges on productive cells are serpentine in shape, those on carrier cells are typically straight or hairpin shaped, and the hairpin ridges are twice as long as serpentine ridges on productive cells. Furthermore, the spacing between ridges on carrier cells is never as small as that in productive infections, so that continuous sheets of viral membrane are never formed. The majority of carrier cells lack the round viral buds observed in productive cells but have, instead, many elongated processes attached to the cell surface. Each of these processes contains one or two hairpin ridges overlying hairpin-shaped nucleocapsids. These "hairpin buds" are restricted to a single region of the carrier cell surface, whereas viral buds are distributed over the entire surface of productive cells. Thus, there are several structural defects in carrier cells that depend on the specific interaction of a certain viral strain with a certain cell type. These defects prevent the deployment of viral antigen in some regions of the cell surface, the formation of nucleocapsids of normal length, the coiling of attached nucleocapsids, and the consolidation of sheets of viral membrane into spherical buds with the nucleocapsids coiled inside. These defects may account for the failure of carrier cells to shed infectious virus. 相似文献
65.
Restriction endonucleases EcoRI and HindIII generated fragments of T4 cytosine-containing DNA were inserted into bacteriophage vector λgtSuIII and plasmid vectors pMB9 and pBR313. Resulting clones were screened for hybridization with 32P labeled T4 tRNA. Recombinant bacteriophages and plasmids were isolated which contained a T4 fragment coding for T4 RNA species 1 and 2 and T4 tRNAArg. Selected λ-T4 hybrid bacteriophages were grown to high titer and their DNA analyzed by gel electrophoresis. 相似文献
66.
Small subunits of ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) have been purified from 3 species of orchid in the genus Cymbidium by gel filtration followed by preparative sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE) and electroelution. The samples were subjected to amino acid composition analysis and partial N-terminal amino acid sequencing. The sequencing data clearly confirm that one of the species examined is the hybrid offspring of a cross between the other two. 相似文献
67.
The gene encoding the nucleocapsid protein of Gill-associated nidovirus of Penaeus monodon prawns is located upstream of the glycoprotein gene
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Cowley JA Cadogan LC Spann KM Sittidilokratna N Walker PJ 《Journal of virology》2004,78(16):8935-8941
The ORF2 gene of Gill-associated virus (GAV) of Penaeus monodon prawns resides 93 nucleotides downstream of the ORF1a-ORF1b gene and encodes a 144-amino-acid hydrophilic polypeptide (15,998 Da; pI, 9.75) containing 20 basic (14%) and 13 acidic (9%) residues and 19 prolines (13%). Antiserum to a synthetic ORF2 peptide or an Escherichia coli-expressed glutathione S-transferase-ORF2 fusion protein detected a 20-kDa protein in infected lymphoid organ and gill tissues in Western blots. The GAV ORF2 fusion protein antiserum also cross-reacted with the p20 nucleoprotein in virions of the closely related Yellow head virus. By immuno-gold electron microscopy, it was observed that the ORF2 peptide antibody localized to tubular GAV nucleocapsids, often at the ends or at lateral cross sections. As GAV appears to contain only two structural protein genes (ORF2 and ORF3), these data indicate that GAV differs from vertebrate nidoviruses in that the gene encoding the nucleocapsid protein is located upstream of the gene encoding the virion glycoproteins. 相似文献
68.
This systematic review examines effects of surface texture on marine biofouling and characterizes key research methodologies. Seventy-five published articles met selection criteria for qualitative analysis; experimental data from 36 underwent quantitative meta-analysis. Most studies investigated fouling mechanisms and antifouling performance only in laboratory assays with one to several test species. Textures were almost exclusively a single layer of regularly arranged geometric features rather than complex hierarchical or irregular designs. Textures in general had no effect or an inconclusive effect on fouling in 46% of cases. However, effective textures more often decreased (35%) rather than increased (19%) fouling. Complex designs were more effective against fouling (51%) than were regular geometric features (32%). Ratios of feature height, width, or pitch to organism body length were significant influences. The authors recommend further research on promising complex and hierarchical texture designs with more test species, as well as field studies to ground-truth laboratory results. 相似文献
69.
Stephen B. Pyecroft Anne-Maree Pearse Richmond Loh Kate Swift Kathy Belov Nolan Fox Erin Noonan Dane Hayes Alex Hyatt Lingfa Wang David Boyle Jeff Church Debra Middleton Robert Moore 《EcoHealth》2007,4(3):346-351
In the mid 1990s an emerging disease characterised by the development of proliferative lesions around the face of Tasmanian
devils (Sarcophilus harrisii) was observed. A multi-disciplinary approach was adopted to define the condition. Histopathological and transmission electron
microscopic examination combined with immunohistochemistry help define Devil Facial Tumour Disease (DFTD) as a neoplastic
condition of cells of neuroendocrine origin. Cytogenetic analysis of neoplastic tissue revealed it to be markedly different
from normal devil tissue and having a consistent karyotype across all tumours examined. Combined with evidence for Major histocompatability
(MHC) gene analysis there is significant evidence to confirm the tumour is a transmissible neoplasm. 相似文献
70.
Differential expression of two P5CS genes controlling proline accumulation during salt-stress requires ABA and is regulated by ABA1, ABI1 and AXR2 in Arabidopsis 总被引:13,自引:0,他引:13