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1.
Kai-For Mo 《Carbohydrate research》2009,344(4):439-1494
The synthesis of laminarahexaose is described. NMR studies of several of the intermediates leading to the β-1,3-glucan show anomalously small coupling constants for some of the C-1 hydrogens. An X-ray structure for the protected hexasaccharide shows that the small coupling constants are due to some of the glucopyranose rings adopting a twist-boat conformation. The X-ray studies also explain other unexpected NMR observations. 相似文献
2.
The heart as an endocrine organ 总被引:1,自引:0,他引:1
Modern data on atrial natriuretic factor (ANF) are presented. Synthesis of this factor, its storage and release from cardiac atria are described. The role of ANF in the body fluid volume regulation and blood pressure homeostasis is discussed. ANF is regarded as a circulating hormone. 相似文献
3.
Francesco Ricci Kshitij Tandon Maria Moßhammer Ellie H.-J. Cho Linda L. Blackall Michael Kühl Heroen Verbruggen 《Environmental microbiology》2023,25(8):1505-1521
The coral skeleton harbours a diverse community of bacteria and microeukaryotes exposed to light, O2 and pH gradients, but how such physicochemical gradients affect the coral skeleton microbiome remains unclear. In this study, we employed chemical imaging of O2 and pH, hyperspectral reflectance imaging and spatially resolved taxonomic and inferred functional microbiome characterization to explore links between the skeleton microenvironment and microbiome in the reef-building corals Porites lutea and Paragoniastrea benhami. The physicochemical environment was more stable in the deep skeleton, and the diversity and evenness of the bacterial community increased with skeletal depth, suggesting that the microbiome was stratified along the physicochemical gradients. The bulk of the coral skeleton was in a low O2 habitat, whereas pH varied from pH 6–9 with depth. Physicochemical gradients of O2 and pH of the coral skeleton explained the β-diversity of the bacterial communities, and skeletal layers that showed O2 peaks had a higher relative abundance of endolithic algae, reflecting a link between the abiotic environment and the microbiome composition. Our study links the physicochemical, microbial and functional landscapes of the coral skeleton and provides new insights into the involvement of skeletal microbes in the coral holobiont metabolism. 相似文献
4.
5.
Mutational specificity of the dnaE173 mutator associated with a defect in the catalytic subunit of DNA polymerase III of Escherichia coli. 总被引:4,自引:0,他引:4
We developed a system to examine forward mutations that occurred in the rpsL gene of Escherichia coli placed on a multicopy plasmid. Using this system we determined the mutational specificity for a dnaE173 mutator strain in which the editing function of DNA polymerase III is impeded. The frequency of rpsL- mutations increased 32,000-fold, due to the dnaE173 mutator, and 87 independent rpsL- mutations in the mutator strain were analyzed by DNA sequencing, together with 100 mutants recovered from dnaE+ strain, as the control. While half the number of mutations that occurred in the wild-type strain were caused by insertion elements, no such mutations were recovered from the mutator strain. A novel class of mutation, named "sequence substitution" was present in mutants raised in the dnaE173 strain; seven sequence substitutions induced in the mutator strain occurred at six sites, and all were located in quasipalindromic sequences, carrying the GTG or CAC sequence at one or both endpoints. While other types of mutation were found in both strains, single-base frameshifts were the most frequent events in the mutator strain. Thus, the mutator effect on this class of mutation was 175,000-fold. A total of 95% of the single-base frameshifts in the mutator strain were additions, most of which occurred at runs of A or C bases so as to increase the number of identical residues. Base substitutions, the frequency of which was enhanced 25,000-fold by the mutator effect, occurred primarily at several hotspots in the mutator strain, whereas those induced in the wild-type strain were more randomly distributed throughout the rpsL sequence. The dnaE173 mutator also increased the frequency of duplications 28,000-fold. Of the three duplications recovered from the mutator strain, one was a simple duplication, the region of which was flanked by direct repeats. The other duplications were complex, one half part of which was in the inverted orientation of a region containing two sets of inverted repeats. The same duplications were also recovered from the wild-type strain. The present data suggest that dnaE173 is a novel class of mutator that sharply induces sequence-directed mutagenesis, yielding high frequencies of single base frameshifts, duplications with inversions, sequence substitutions and base substitutions at hotspots. 相似文献
6.
Kinetics of folding and unfolding of alpha alpha-tropomyosin and of nonpolymerizable alpha alpha-tropomyosin. 总被引:1,自引:0,他引:1
Stopped flow CD (SFCD) kinetic studies of self-assembly of coiled coils of rabbit alpha alpha-tropomyosin and of nonpolymerizable alpha alpha-tropomyosin (NPTm) are reported. The protein was denatured in 6 M urea buffer, then renatured by 10-fold dilution into benign saline buffer. Folding was monitored by SFCD in the backbone region (222 nm). Protein chains are shown to be totally unfolded (and separated in the reduced species) in the initial denaturing medium and fully folded as two-chain coiled coils in the final benign medium. In all cases of folding in benign buffer of totally unfolded chains, two phases were found in the folding process: a fast phase (less than 0.04 s, the SFCD dead time), in which an intermediate state with about 70% of the equilibrium ellipticity forms; followed by a slower, observable phase that completes the folding. The slow phase is first order (k-1 = 1.6 s at 20 degrees C), signifying that chain association for reduced samples occurs in the fast phase. In contrast, folding in benign buffer from an initial state with 70% of the equilibrium ellipticity is all fast, suggesting that the folding intermediate is not an equilibrium species. Cross-linking at Cys-190 increases the helix content of the fast-formed intermediate state to about 85% of the equilibrium value, but leaves the rate constant of the slow phase unchanged. In NPTm, which does not form high aggregates at low ionic strength, the rate of the observable phase is almost independent of ionic strength in the range of approximately 0.15-0.6 M, but is reduced one to two orders of magnitude by further reduction to 0.026 M. In folding from totally unfolded chains, the rate is reduced less than one order of magnitude by changing the final state to about 50% folded. In contrast to folding, unfolding of alpha alpha-tropomyosin from the native state is all fast. 相似文献
7.
The thermal denaturation of nonpolymerizable alpha alpha-tropomyosin and its segments as a function of ionic strength 总被引:3,自引:0,他引:3
Nonpolymerizable tropomyosin (NPTm) is found to unfold thermally at high ionic strength almost exactly as the parent protein, but it does not aggregate at low ionic strength. Thus, NPTm can be used as a tropomyosin surrogate whose coiled-coil structural stability can be probed by varying the ionic strength. Studies of NPTm by CD show that increasing ionic strength stabilizes the coiled-coil structure. CD spectra over a wide range of helix content, obtained by varying either temperature or ionic strength, show an isodichroic point at 203 nm, suggesting a local, residue-level, two-state model. At given temperature, such a local helix in equilibrium random equilibrium suggests ln [phi h/(1-phi h)] = A1 + A2In, wherein phi h is the fraction helix, and A1, A2, and n are constants. In the low ionic strength region, theoretical limiting laws for ionic strength mediated charge-charge, dipole-dipole, and apolar-apolar (salting out) interactions give, respectively, n = 0.5, 1.0, and 1.0. Our experimental values for 40 degrees C, where the data span a wide range of helix content, show n = 1.0, suggesting that ionic strength stabilizes either by reducing dipole-dipole repulsions or by enhancing hydrophobic interactions, both probably interhelix in nature. Two segments of tropomyosin, 11Tm127 and 142Tm281, neither of which aggregate at low ionic strength, give results similar to those for NPTm, i.e., n = 0.96 and 0.84, respectively. 相似文献
8.
Dai Sik Ko Junho Kang Hye Jin Heo Eun Kyoung Kim Kihun Kim Jin Mo Kang YunJae Jung Seung Eun Baek Yun Hak Kim 《International journal of biological sciences》2022,18(13):5154
Vascular smooth muscle cell (VSMC) proliferation is a hallmark of neointimal hyperplasia (NIH) in atherosclerosis and restenosis post-balloon angioplasty and stent insertion. Although numerous cytotoxic and cytostatic therapeutics have been developed to reduce NIH, it is improbable that a multifactorial disease can be successfully treated by focusing on a preconceived hypothesis. We, therefore, aimed to identify key molecules involved in NIH via a hypothesis-free approach. We analyzed four datasets (, GSE28829, GSE43292, and GSE100927), evaluated differentially expressed genes (DEGs) in wire-injured femoral arteries of mice, and determined their association with VSMC proliferation in vitro. Moreover, we performed RNA sequencing on platelet-derived growth factor (PDGF)-stimulated human VSMCs (hVSMCs) post-phosphoenolpyruvate carboxykinase 2 (PCK2) knockdown and investigated pathways associated with PCK2. Finally, we assessed NIH formation in Pck2 knockout (KO) mice by wire injury and identified PCK2 expression in human femoral artery atheroma. Among six DEGs, only PCK2 and RGS1 showed identical expression patterns between wire-injured femoral arteries of mice and gene expression datasets. PDGF-induced VSMC proliferation was attenuated when hVSMCs were transfected with PCK2 siRNA. RNA sequencing of PCK2 siRNA-treated hVSMCs revealed the involvement of the Akt-FoxO-PCK2 pathway in VSMC proliferation via Akt2, Akt3, FoxO1, and FoxO3. Additionally, NIH was attenuated in the wire-injured femoral artery of Pck2-KO mice and PCK2 was expressed in human femoral atheroma. PCK2 regulates VSMC proliferation in response to vascular injury via the Akt-FoxO-PCK2 pathway. Targeting PCK2, a downstream signaling mediator of VSMC proliferation, may be a novel therapeutic approach to modulate VSMC proliferation in atherosclerosis. GSE120521相似文献
9.
10.
Jinchun Wu Ziye Zou Yang Liu Xuhao Liu Zhengrong Zhangding Mo Xu Jiazhi Hu 《Nucleic acids research》2022,50(19):11128
CRISPR/Cas9 has been adapted to disrupt endogenous genes in adoptive T-lymphocyte therapy to prevent graft-versus-host disease. However, genome editing also generates prevalent deleterious structural variations (SVs), including chromosomal translocations and large deletions, raising safety concerns about reinfused T cells. Here, we dynamically monitored the progression of SVs in a mouse model of T-cell receptor (TCR)-transgenic T-cell adoptive transfer, mimicking TCR T therapeutics. Remarkably, CRISPR/Cas9-induced SVs persist and undergo clonal expansion in vivo after three weeks or even two months, evidenced by high enrichment and low junctional diversity of identified SVs post infusion. Specifically, we detected 128 expanded translocations, with 20 615 as the highest number of amplicons. The identified SVs are stochastically selected among different individuals and show an inconspicuous locus preference. Similar to SVs, viral DNA integrations are routinely detected in edited T cells and also undergo clonal expansion. The persistent SVs and viral DNA integrations in the infused T cells may constantly threaten genome integrity, drawing immediate attention to the safety of CRISPR/Cas9-engineered T cells mediated immunotherapy. 相似文献