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1.
Crystallization and preliminary crystallographic studies of the decadeoxyoligonucleotide d(CpGpTpApCpGpTpApCpG) 总被引:1,自引:0,他引:1
Crystals of the self-complementary decadeoxyoligonucleotide d(CpGpTpApCpGpTpApCpG) have been grown from a solution containing [Co(NH3)6]Cl3 and spermine. The amber-colored crystals are hexagonal and belong to the space group P6(5) (or P6(1] with unit cell parameters a = 17.93 A, c = 43.41 A. Precession photography and molecular packing considerations indicate that the unit cell consists of a 12 nucleotide duplex. The asymmetric unit, therefore, is a disordered duplex dimer in which each pyrimidine-purine base-pair is occupied 60% of the time by a C . G pair and 40% of the time by a T . A pair. The above considerations and preliminary structure analysis reveal that this alternating pyrimidine-purine oligomer assumes a Z-DNA conformation. 相似文献
2.
Corneas with central epithelial wounds, 3 mm in diameter, were organ cultured in the presence of tunicamycin (TM) (1 microgram/ml), an antibiotic that inhibits glycosylation of asparagine-linked glycoproteins. Compared with control corneas, which healed in 22 hr, corneas cultured in the presence of TM for the entire culture time or for only the first 6 hr displayed a progressively slower epithelial healing rate that essentially dropped to zero by 24 hr of culture time. At 24 hr, approximately 75% of the wound was covered. After repeated washings with TM-free culture media (6X, 10 min each), this effect could consistently be reversed in corneas exposed to TM for 6 hr. Incorporation of [3H]glucosamine into trichloroacetic acid-precipitable proteins of migrating epithelial sheets was reduced to 14% that of controls after 12 hr of culture with TM, whereas [14C]leucine incorporation was not significantly affected. The decreased glycosylation was reflected on the cell surface after 12 and 20 hr culture in the presence of TM: apical cell membranes of the first six cells of the leading edge of the migrating sheet bound significantly fewer ferritin-concanavalin A particles per micrometer of membrane than did controls. These results indicate that synthesis of asparagine-linked glycoproteins is required for continued migration of corneal epithelial sheets. The asparagine-linked glycoproteins that are required for migration probably include cell-surface glycoproteins. 相似文献
3.
4.
Andrew W. Saxe Ji-Won Yoon Phillip Gorden Murray F. Brennan 《In vitro cellular & developmental biology. Plant》1982,18(10):884-890
Summary Dispersed cells from both fresh and cryopreserved human insulinoma have been maintained in cell culture. Initial yield of
viable cells was 50% for fresh and 25% for cryopreserved tissue. Viability of cells in culture was documented by increasing
numbers of cells (doubling time approximately 5 d initially and 2 d at the sixth subculture for both fresh and cryopreserved
tissue) and continued release of insulin over time (approximately 100 ng/ml per 105 cells at 10 d and 175 ng/ml per 105 cells at 30 d of culture for both fresh and cryopreserved tissue). Evidence that cells growing in culture were beta cells
was provided by: (a) recovery of intracellular and extracellular immunoreactive insulin (IRI), (b) electron microscopic morphology,
and (c) immunohistochemical staining. Cells from fresh insulinoma incubated with increasing concentrations of extracellular
glucose released increasing amounts of IRI up to approximately 15 mM glucose, which paralleled changes in plasma insulin obtained during a preoperative glucose tolerance test.
Under an Intergovernmental Personnel Act Exchange from the Department of Surgery, University of California, Davis, Sacramento
Medical Center. 相似文献
5.
6.
Definition of the surface antigens of Mycobacterium malmoense and use in studying the etiology of a form of mycobacteriosis 总被引:2,自引:0,他引:2 下载免费PDF全文
M McNeil A Y Tsang J K McClatchy C Stewart I Jardine P J Brennan 《Journal of bacteriology》1987,169(7):3312-3320
Mycobacterium malmoense is the latest of a roster of atypical mycobacteria implicated in pulmonary infections. Yet it lacks recognizable phenotypic features to allow its ready identification. Some 23 clinical isolates of M. malmoense were examined for homologous seroagglutination reactions and characteristic surface antigens. One group showed concordant agglutination interreactions and an identical spectrum of glycolipids and are regarded as M. malmoense sensu stricto. The glycolipids are of the newly found, trehalose-containing lipooligosaccharide class. De-O-acylation followed by high-pressure liquid chromatography revealed one major and several minor oligosaccharides. Partial acidic cleavage to release glycosidically linked trehalose, alpha-mannosidase digestion to demonstrate the presence of a non-reducing-end mannobiose, perdeuteriomethylation, partial acid hydrolysis, reduction, and O ethylation, combined with 1H nuclear magnetic resonance and electron impact and fast-atom bombardment mass spectrometry revealed the structure of the major oligosaccharide as alpha-D-Manp-(1----3) -alpha-D-Manp-(1----[2-alpha-L-Rhap-(1--]4--3)-alpha-L-Rh ap- (1----3)-alpha-D-Glcp-(1----1)-alpha-D-Glcp, in which two of the 2-alpha-L-Rhap residues are O methylated at C-3. (Man, mannose; Rha, rhamnose; Glc, glucose; p, pyranosyl). The structures of the minor oligosaccharides were also determined; they differ at the distal nonreducing end. The dominant oligosaccharide was acylated by octanoate, 2-methyleicosanoate, and 2,4-dimethylpentacosanoate to yield the major species-specific surface antigen of M. malmoense, which we regard as the most characteristic feature of the pathogen. 相似文献
7.
A bioactive biotin-containing derivative of the synthetic bovine parathyroid hormone analog [Nle8,Nle18,Tyr34]bovine parathyroid hormone-(1-34) (bPTH-(1-34] amide was prepared by reacting the peptide with N-biotinyl-epsilon-aminocaproic acid N-hydroxysuccinimide ester. The derivative was incubated with particulate renal plasma membranes or with detergent [3-[(3-cholamidopropyl)dimethylammonio]-1-propanesulfonate) extracts of renal cortical membranes, and two membrane components were identified. Labeling of these components was competitively inhibited by underivatized bPTH-(1-34) or bPTH-(3-34) but not by insulin, adrenocorticotropin, or oxidized rat PTH-(1-34). PTH-binding components that were immobilized on nitrocellulose could be detected by incubating the membrane with biotinyl-bPTH-(1-34). Binding components of apparent molecular mass 68, 70, and 150 kDa were specifically labeled in plasma membranes derived from canine, human, and porcine renal cortex, rat liver, and human fibroblasts. The 68-kDa binding protein was found to be consistently more acidic than the 70-kDa binding protein in human, porcine, and canine renal membranes analyzed by two-dimensional electrophoresis. The 68-70-kDa receptor doublet could be specifically isolated by streptavidin-agarose chromatography of solubilized membrane extracts that had first been incubated with biotinyl-BPTH-(1-34). Biotinyl-bPTH-(1-34) should be useful as a tool for further characterization and purification of the PTH receptor. 相似文献
8.
Evolution of the 28S ribosomal RNA gene in anurans: regions of variability and their phylogenetic implications 总被引:1,自引:0,他引:1
Fifteen restriction sites were mapped to the 28S ribosomal RNA gene of
individuals representing 54 species of frogs, two species of salamanders, a
caecilian, and a lungfish. Eight of these sites were present in all species
examined, and two were found in all but one species. Alignment of these
conserved restriction sites revealed, among anuran 28S rRNA genes, five
regions of major length variation that correspond to four of 12 previously
identified divergent domains of this gene. One of the divergent domains
(DD8) consists of two regions of length variation separated by a short
segment that is conserved at least throughout tetrapods. Most of the
insertions, deletions, and restriction-site variations identified in the
28S gene will require sequence-level analysis for a detailed reconstruction
of their history. However, an insertion in DD9 that is coextensive with
frogs in the suborder Neobatrachia, a BstEII site that is limited to
representatives of two leptodactylid subfamilies, and a deletion in DD10
that is found only in three ranoid genera are probably synapomorphies.
相似文献
9.
Novel human proalbumin variant with intact dibasic sequence facilitates identification of its converting enzyme 总被引:1,自引:0,他引:1
We describe here the identification of a new genetic variant of human proalbumin with an N-terminal sequence of Arg-Gly-Val-Phe-Arg-Arg-Val-Ala-His-Lys-. Proalbumin Blenheim (10%) and mature albumin Blenheim (38%) with an initial sequence of Val-Ala-His-Lys-make up nearly half the serum albumin in affected individuals. Despite retaining an intact dibasic processing site, proalbumin Blenheim (1 Asp----Val) enters the circulation unprocessed. The observed ratio of proalbumin to albumin can be accounted for by proteolysis in the periphery. Employed as a potential substrate, proalbumin Blenheim provides a unique means of identifying the physiologically relevant proalbumin convertase. In vitro studies showed that the variant is readily cleaved by trypsin. However, it is not cleaved by the proposed proalbumin convertase, a membrane-bound Ca2+-dependent proteinase prepared from rat liver Golgi vesicles, which gives authentic cleavage of normal human proalbumin. 相似文献