分类: 物理学 提交时间: 2016-05-08
摘要: A general (k, l) clique community of a network, which consists of adjacent k- cliques sharing at least l vertices with k - 1 >= l >= 1, is introduced. With the emergence of a giant (k, l) clique community in the network, there is a (k, l) clique percolation. Using the largest size jump Delta of the largest clique community during network evolution and the corresponding evolution step T-c, we study the general (k, l) clique percolation of the Erdos-Renyi network. We investigate the averages of Delta and T-c and their fluctuations for different network size N. The clique percolation can be identified by the power-law finite-size effects of the averages and root mean squares of fluctuation. The finite-size scaling distribution functions of fluctuations are calculated. The universality class of the (k, l) clique percolation is characterized by the critical exponents of power-law finite-size effects. Using Monte Carlo simulations, we find that the Erdos-Renyi network experiences a series of (k, l) clique percolation with (k, l) = (2, 1), (3, 1), (3, 2), (4, 1), (4, 2), (4, 3), (5, 1). We find that the critical exponents and therefore the universality class of the (k, l) clique percolation depend on clique connection index l, but are independent of clique size k.
分类: 物理学 >> 普通物理:统计和量子力学,量子信息等 提交时间: 2017-05-02
摘要: We study type I clathrate Ba8Cu5.1Ge40.2Sn0.7 single crystals (space group Pm3"n, no. 223, a 1⁄4 10.7151(3)) grown using a Sn flux method. Microprobe analysis and single-crystal X-ray diffraction reveal a small amount of Sn embedded in the Cu/Ge framework, which increases disorder at the guest Ba sites. Ba8Cu5.1Ge40.2Sn0.7 is diamagnetic with a susceptibility of $2.8 10 7 emu g 1 and shows metal-like behavior (dr/dT > 0) with a low charge carrier concentration of 0.5 e per unit cell at 300 K. The single crystals show a relatively high carrier mobility (m (300 K) 1⁄4 11.9 cm2 V 1) and very low lattice thermal conductivity ($0.6 W m 1 K 1). The thermoelectric figure of merit ZT of Ba8Cu5.1Ge40.2Sn0.7 single crystals reaches a maximum value of 0.6 at 773 K, which can be further improved by adjusting the chemical composition.
分类: 物理学 >> 核物理学 提交时间: 2016-09-12
摘要: A neutral structure in the DD¯∗ system around the DD¯∗ mass threshold is observed with a statistical significance greater than 10σ in the processes e+e−→D+D∗−π0+c.c. and e+e−→D0D¯∗0π0+c.c. at s√ = 4.226 and 4.257 GeV in the BESIII experiment. The structure is denoted as Zc(3885)0. Assuming the presence of a resonance, its pole mass and width are determined to be (3885.7+4.3−5.7(stat)±8.4(syst)) MeV/c2 and (35+11−12(stat)±15(syst)) MeV, respectively. The Born cross sections are measured to be σ(e+e−→Zc(3885)0π0,Zc(3885)0→DD¯∗)=(77±13(stat)±17(syst)) pb at 4.226 GeV and (47±9(stat)±10(syst)) pb at 4.257 GeV. The ratio of decay rates B(Zc(3885)0→D+D∗−+c.c.)B(Zc(3885)0→D0D¯∗0+c.c.) is determined to be0.96±0.18(stat)±0.12(syst), consistent with no isospin violation in the process Zc(3885)0→DD¯∗.
分类: 药物科学 >> 结构生物学 提交时间: 2024-02-29
摘要: Succinic acid, a tricarboxylic acid (TCA) cycle intermediate, significantly influences mitochondrial reactive oxygen species homeostasis through the G protein-coupled succinate receptor (SUCR1, also called GPR91), linking it to various physiological and pathological processes. Despite SUCR1’s pivotal role in mediating effects leading to liver fibrosis, hypertension, angiogenesis, inflammation, and offering a therapeutic target for multiple diseases, its activation mechanism by diverse ligands and interaction with downwards G protein remains poorly understood. This study presents the cryo-electron microscopy (cryo-EM) structures of SUCR1 in complex with inhibitory G protein (Gi) bound to succinic acid, maleic acid, and compound 31, a high-affinity agonist. These structures elucidate the distinct ligand binding modes, uncover the activation signal cascade, and detail the G protein coupling mechanism of SUCR1. Our findings provide a comprehensive structural basis for SUCR1 activation, paving the way for structure-based drug design aimed at SUCR1-related pathologies.
分类: 药物科学 >> 结构生物学 提交时间: 2024-02-21
摘要: Bombesin receptor subtype-3 (BRS3) is an important orphan G protein-coupled receptor that regulates energy homeostasis and insulin secretion. As a member of the bombesin receptor (BnR) family, which includes neuromedin B receptor (NMBR) and gastrin-releasing peptide receptor (GRPR), the lack of known endogenous ligands and high-resolution structure has impeded understanding of BRS3 signaling and function. Here, we present cryogenic electron microscopy (cryo-EM) structures of BRS3 in complex with heterotrimeric Gq protein in three states: apo, bound to the pan-BnR agonist, BA1, and bound to the synthetic BRS3-specific agonist MK-5046. These structures reveal the architecture of the orthosteric ligand pocket underpinning molecular recognition. Comparisons with BnR members provide insights into the structural basis for BRS3’s selectivity and low affinity for bombesin peptides. Examination of conserved micro-switches suggests a shared activation mechanism among BnRs. Together our results enable deeper exploration of BRS3’s ligand selectivity, signaling, and therapeutic targeting for diabetes and obesity.
分类: 化学 >> 物理化学 提交时间: 2017-11-05 合作期刊: 《结构化学》
摘要: The title compound, ethyl (R)-2-(biphenyl-4-carbonyl)-2,3,4,9-tetrahydro-1H-pyrido[3,4- b]indole-1-carboxylate (C27H24N2O3) has been synthesized, and its structure was characterized by 1H-NMR, 13C-NMR, ESI-MS and single-crystal X-ray diffraction. It crystallizes in the orthorhombic system, space group Pbca with a = 16.9950(8), b = 9.5445(4), c = 28.3188(3) Å, V = 4593.6(3) Å3, Z = 8, T = 294.64(10) K, μ(MoKα) = 0.08 mm-1, Dc = 1.228 g/cm3, F(000) = 1792.0 and GOOF = 1.036. 11836 reflections were measured (7.04≤2θ≤52.04°), and 4506 were unique (Rint = 0.0393, Rsigma = 0.0546) and used in all calculations. The final R = 0.0576 (I > 2σ(I)) and wR = 0.1563 (all data). The preliminary biological tests show that the title compound has a good antitumor activity against Hela in vitro with the IC50 value of 4.71 μmol/L.
分类: 化学 >> 物理化学 提交时间: 2017-11-05 合作期刊: 《结构化学》
摘要: A novel coordination complex, {[Cd2(C20H10O5)2(H2O)4]·10H2O}n, has been synthesized based on fluorescein (2-(6-hydroxy-3-oxo-3H-xanthen-9-yl) benzoic acid) and systematically characterized by elemental analysis, infrared (IR) spectrum, thermo gravimetric analysis (TGA), powder X-ray diffraction (PXRD) and single-crystal X-ray diffraction. Compound 1 crystallizes in monoclinic, space group P2/n with a = 20.428(5), b = 8.084(2), c = 21.689(5) Å, β = 96.360(5)º, Mr = 993.46, V = 3559.7(15) Å3, Z = 4, Dx = 1.845 g/cm3, μ = 1.276 mm-1, F(000) = 1974.0, GOOF = 1.044, λ(MoKα) = 0.71073 Å, the final R = 0.0553 and wR = 0.1720 for 7245 observed reflections with I > 2σ(I).
分类: 生物学 >> 生物物理学 提交时间: 2016-05-11
摘要: Enfuvirtide (T20), is the first HIV fusion inhibitor approved for treatment of HIV/AIDS patients who fail to respond to the current antiretroviral drugs. However, its clinical application is limited because of short half-life, drug resistance and cross-reactivity with the preexisting antibodies in HIV-infected patients. Using an artificial peptide strategy, we designed a peptide with non-native protein sequence, AP3, which exhibited potent antiviral activity against a broad spectrum of HIV-1 strains, including those resistant to T20, and had remarkably longer in vivo half-life than T20. While the preexisting antibodies in HIV-infected patients significantly suppressed T20's antiviral activity, these antibodies neither recognized AP3, nor attenuated its anti-HIV-1 activity. Structurally different from T20, AP3 could fold into single-helix and interact with gp41 NHR. The two residues, Met and Thr, at the N-terminus of AP3 form a hook-like structure to stabilize interaction between AP3 and NHR helices. Therefore, AP3 has potential for further development as a new HIV fusion inhibitor with improved antiviral efficacy, resistance profile and pharmacological properties over enfuvirtide. Meanwhile, this study highlighted the advantages of artificially designed peptides, and confirmed that this strategy could be used in developing artificial peptide-based viral fusion inhibitors against HIV and other enveloped viruses.
分类: 物理学 >> 核物理学 提交时间: 2023-06-18 合作期刊: 《Nuclear Science and Techniques》
摘要: Aluminium is widely used as an antimicrobial coagulant, food additive, and cookware. However, many reports indicate that aluminium may be a critical factor in many amyloid diseases, such as Alzheimers disease and Parkinsons disease. Unfortunately, the underlying mechanism is still poorly understood, which limits efforts to prevent and treat these diseases. In this paper, using an ab initio method, we studied the interaction of Al-backbone ring structure with the -electron-rich sidechains of His, Phe, Trp, and Tyr. We found that in the absence of water, the Al-backbone ring can stably bind with those sidechains. In the presence of water, the Al-backbone ring can bind to the His sidechain and cannot bind to the other sidechains. As revealed by further investigations, this could be attributed to the fact that there was a coordinate bond of the Al-backbone ring with the His sidechain, while there were the - stacking and cation--like interactions with the other sidechains. These findings potentially provide a molecular understanding of Al-related toxicity, and may be helpful in designing drugs for those aforementioned aluminum-linked diseases and encourage treatment of Al-polluted water.
分类: 化学 >> 物理化学 提交时间: 2017-11-05 合作期刊: 《结构化学》
摘要: Two coordination polymers (CPs), {[Ag(ADA)0.5(DPE)]·H2O}n (1) and {[Ag(ADA)0.5(Bipy)0.5]·H2O}n (2), (H2ADA = 3,3-azodibenzoic acid, DPE = 1,2-di(4-pyridyl)- ethylene, Bipy = 4,4΄-bipyridine), have been synthesized via solvothermal reactions of Ag+ with ADA2- and/or DPE, Bipy. CPs 1 and 2 were characterized by elemental analyses, IR spectra, thermal behaviors, and X-ray single-crystal diffraction. CPs 1 and 2 feature “Ag···Ag” subunits. CP 1 shows a 3D construction, in which the “Ag···Ag” subunits extend through ADA2- and DPE ligands using μ6-kO,O;kO;kO;kO,O;kO;kO and μ2-kO;kO coordination modes, respectively. It crystallizes in triclinic system, space group P, with a = 0.3808(18), b = 1.2476(6), c = 1.309(6) nm, α = 76.757(5), β = 84.649(5), γ = 86.809(5)º, V = 0.6024(5) nm3, Z = 2, Mr = 351.11, C13H11AgN2O3, Dc = 1.936 g/cm3, F(000) = 348, S = 1.064, R = 0.0323 and wR = 0.0689. CP 2 exhibits a 3D supramolecular structure, in which the “Ag···Ag” subunits are connected by ADA2- and DPE ligands with μ6-kO;kO;kO,O;kO;kO and μ2-kO;kO coordination modes, respectively. Ultimately, through hydrogen bond and π···π interaction, the “Ag···Ag” subunits stabilize the 3D supramolecular structure of 2. It crystallizes in monoclinic, space group C2/c, with a = 25.301(15), b = 13.197(8), c = 6.970(4) nm, β = 102.597(7)º, V = 2.271(2) nm3, Z = 8, C12H10AgN2O2.50, Mr = 330.09, Dc = 1.931 g/cm3, F(000) = 1304, S = 1.082, R = 0.1107 and wR = 0.2984. The fluorescence properties of CPs 1 and 2 have been also investigated.
分类: 化学 >> 物理化学 提交时间: 2017-11-05 合作期刊: 《结构化学》
摘要: Using 4΄-methoxy-5-hydroxyisoflavone and 4΄,5-dihydroxy-7-methoxyisoflavone as leding compounds, 6-methoxy-2H-phenanthro[9,10-c]pyrazol-11-ol (1a) and 9-methoxy-2H-phenanthro [9,10-c]pyrazol-6,11-diol (1b) were synthesized by two dehydration processes in the EtOH solution. They were characterized by IR, 1H NMR and 13C NMR. The black prism crystal of 1a was grown by the slow solvent evaporation technique from 40:1 (v/v) CHCl3/MeOH, and it was determined by single-crystal X-ray diffraction. In the crystal structure, 1a was stabilized by intramolecular (O–H···N) and intermolecular (N–H···O, O–H···O, π···π, C–H···π) interactions. In addition, the fluorescence properties of 1a and 1b in the base and neutral media revealed that they possessed excited state intramolecular proton transfer phenomena (ESIPT).
分类: 化学 >> 物理化学 提交时间: 2017-11-05 合作期刊: 《结构化学》
摘要: One new coordination polymer (CP) [Cd(bct)(bib)]·2(H2O) (1), based on 3,5-bis(4΄-carboxy- phenyl)-1,2,4-triazole (H2bct) and 1,4-bis(imidazol-1-ylmethyl)benzene(bib), has been synthesized by hydrothermal method, and its structure was determined and characterized by single-crystal X-ray diffraction analysis, elemental analysis, IR spectroscopy, and thermogravimetric analysis. The crystal structure of CP 1 is a three-dimensional framework with (3,5)-connected topology, where the bct ligands adopt a µ3-kO,kO,kO coordination mode connecting with three Cd centers and the bib ligands adopt a µ2-kN,kN coordination mode bridging two Cd ions. It crystallizes in monoclinic system, space group C2/c, with a = 2.6838(4), b = 1.24221(17), c = 1.8011(2) nm, β = 102.939(2)º, V = 5.8522(13) nm3, Z = 8, C30H27CdN7O6, Mr = 694.00, Dc = 1.566 g/cm3, F(000) = 2784, S = 1.055, R = 0.0294 and wR = 0.0731. Furthermore, solid-state photoluminescence measurements show that CP 1 produces strong emissions at room temperature.
分类: 物理学 >> 基本粒子与场物理学 提交时间: 2016-05-08
摘要: Aiming to understand real-world hierarchical networks whose degree distributions are neither power law nor exponential, we construct a hybrid clique network that includes both homogeneous and inhomogeneous parts, and introduce an inhomogeneity parameter to tune the ratio between the homogeneous part and the inhomogeneous one. We perform Monte-Carlo simulations to study various properties of such a network, including the degree distribution, the average shortest-path-length, the clustering coefficient, the clustering spectrum, and the communicability.
分类: 生物学 >> 生物物理学 提交时间: 2016-05-11
摘要: Maize chlorotic mottle virus (MCMV) is the only member of the Machlomovirus genus in the family Tombusviridae. Here, we obtained the Cryo-EM structure of MCMV by single particle analysis with most local resolution at approximately 4 angstrom. The C alpha backbone was built based on residues with bulky side chains. The resolved C-terminus of the capsid protein subunit and obvious openings at the 2-fold axis demonstrated the compactness of the asymmetric unit, which indicates an important role in the stability of MCMV. The Asp116 residue from each subunit around the 5-fold and 3-fold axes contributed to the negative charges in the centers of the pentamers and hexamers, which might serve as a solid barrier against the leakage of genomic RNA. Finally, the loops most exposed on the surface were analyzed and are proposed to be potential functional sites related to MCMV transmission. (C) 2015 Elsevier Inc. All rights reserved.
分类: 心理学 >> 认知心理学 提交时间: 2020-06-30
摘要: Metacognition refers to the ability to introspect our cognitive ability, which plays an essential role in guiding and optimizing our activities. However, little is known about metacognitive capacity for highly practiced motor behaviors and its neural correlates. Using structural and functional magnetic resonance imaging (MRI), the present study examined the brain substrates underlying individual differences in self-awareness of handwriting in adults, a highly practiced visuomotor skill. Results showed that adult writers generally overestimate their handwriting skill, which is more pronounced in males relative to females. The extent of overestimation of handwriting quality was positively correlated with grey matter volume in the left fusiform gyrus, right middle frontal gyrus and right precuneus. Moreover, the activation of these regions in a handwriting task was not correlation with self-awareness of handwriting, confirming that the identified connection between brain structures and handwriting self-awareness is independent of task performances. The left fusiform gyrus and right middle frontal gyrus are thought to represent domain-specific brain mechanisms for handwriting self-awareness, while the right precuneus is likely to be a domain-general brain mechanism, suggesting that the ability of introspect practiced visuomotor skills relies on both domain-general and domain-specific brain systems. Together, this study is the first to reveal the neuroanatomical correlates of a highly practiced motor behavior, extending our understanding about the neural basis of human metacognition.
分类: 化学 >> 物理化学 提交时间: 2017-11-05 合作期刊: 《结构化学》
摘要: Two new inorganic-organic hybrid vanadogermanates H[Cd(en)(phen)(H2O)][Cd(en)(phen)]{[Cd(phen)]2[Ge8V12O41(OH)7]}�H2O (1) and [Cd(dien)2][Cd(dien)]2{[Cd(phen)]2Ge8V12O42(H2O)(OH)6}�.5H2O (2) (en = ethylenediamine, dien = diethylenetriamine, phen = 1,10-phenanthroline) have been synthesized by hydrothermal method. Their structures were measured by single-crystal X-ray diffractions, thermogravimetric analysis, powder X-ray diffractions and infrared spectra. Structural analysis reveals that compound 1 is an infrequent dimeric structure based on di-Cd-substituted Ge-V-O cluster and transition-metal complex bridges, while compound 2 is an infinite 1-D chain constructed from di-Cd-substituted Ge-V-O clusters and dinuclear bridging complexes. Magnetic measurement indicated that both 1 and 2 exhibit antiferromagnetic behaviors.
分类: 化学 >> 物理化学 提交时间: 2017-11-05 合作期刊: 《结构化学》
摘要: Two new copper complexes based on pyrazole-3-carboxylic acid (H2pca) ligand, Cu(Hpca)2(H2O)2·2H2O (1) and Cu2(pca)2(H2O)4 (2) have been synthesized and fully characterized by single-crystal X-ray diffraction (SXRD), infrared spectroscopy (IR), thermal gravity analysis (TGA), powder X-ray diffraction (PXRD) and elemental analyses. Complex 1 is mononuclear while complex 2 shows a dinuclear structure. Complex 1 crystallizes in the monoclinic system, space group P21/c with Z = 2, a = 6.5591(5), b = 21.696(2), c = 4.9486(2) Å, V = 680.94(9) Å3, F(000) = 366, Dc = 1.745 g/cm3, μ = 1.650 mm-1, the final R = 0.0340 and wR = 0.0792. Complex 2 crystallizes in the monoclinic system, space group P21/n with Z = 2, a = 5.1935(4), b = 9.6052(7), c = 12.7347(9) Å, V = 634.44(8) Å3, F(000) = 420, Dc = 2.195 g/cm3, μ = 3.404 mm-1, the final R = 0.0305 and wR = 0.0653. The three-dimensional frameworks of two complexes are formed by the O−H···O and N−H···O hydrogen bonding interactions. Notably, two copper complexes are further used as catalysts in the oxidation of alkylbenzenes using t-butylhydroperoxide (TBHP) as the oxidant and they exhibit excellent catalytic performance (Conv. up to 98.9%, Sele. up to 98.7%).
分类: 化学 >> 物理化学 提交时间: 2017-11-05 合作期刊: 《结构化学》
摘要: One novel phenoxyacetamide derivative (C22H28N2O3, Mr = 368.47) has been synthesized and determined by means of NMR spectroscopy, high resolution mass spectra and single-crystal X-ray diffraction. The single crystal belongs to the monoclinic system, space group Cc with a = 14.910(3), b = 14.592(3), c = 38.683(8) Å, β = 100.37(3)°, V = 8279(3) Å3, Z = 16, Dc = 1.183 g/cm3, F(000) = 3168, μ = 0.079 mm-1, MoKα radiation (λ = 0.71073 Å), the final R = 0.0508 and wR = 0.0666 for 4120 observed reflections with I > 2σ(I). There are four independent molecules in an asymmetric unit cell. The four symmetry-independent molecules have a variety of different conformations indicating considerable conformational freedom. The bioassay results indicated that the title compound displayed effective activities against glutamine-induced neurotoxicity in PC12 cells and significantly prolonged the survival time of mice subjected to acute cerebral ischemia.
分类: 化学 >> 物理化学 提交时间: 2017-11-05 合作期刊: 《结构化学》
摘要: Four new coordination compounds, [Zn(bppc)2(H2O)2]·3H2O (1), [Zn2(bppc)2(m-bdc)(H2O)4]·7H2O (2), [Zn(bppc)2(H2O)2]n·n(m-Hbdc)·n(H2O) (3), [Zn2(bppc)(btc)(H2O)3]n·5nH2O (4) (Hbppc = 2,6-bis(pyrazin-2-yl)pyridine-4-carboxylate, H2(m-bdc) = 1,3-benzenedicarboxylic acid, H3btc = 1,3,5-benzene-tricarboxylic acid), have been hydrothermally synthesized and structurally characterized. Compound 1 shows a mononuclear structure and 2 shows a dinuclear structure. Compound 3 is a one-dimensional chain structure, which is extended into a 3D supramolecular network by intermolecular hydrogen interactions. In 4, a 1D loop-like chain is connected by (btc)3- anions to generate a 2D layer structure. The structure differences of 1~4 show that the pH and aromatic acid as auxiliary ligand have important influence on the final structures.[1]Additionally, the luminescent properties of 1~4 have been investigated with fluorescent spectra in the solid state, and 1~4 display a strong fluorescent emission at room temperature and have potential applications as fluorescent-emitting materials.
提交时间: 2017-05-02
摘要: The title compound, C18H28O3, was prepared by the reaction of 2,6-di-tert-butylphenol with methyl acrylate under basic conditions using dimethyl sulfoxide as the promoter. The structure of this antioxidant indicates significant strain between the ortho te