分类: 生物学 >> 生物物理学 >> 生物物理、生物化学与分子生物学 提交时间: 2016-05-15
摘要: The cyclic nucleotide-binding (CNB)-like protein (CNB-L) from Brucella abortus shares sequence homology with CNB domain-containing proteins. We determined the crystal structure of CNB-L at 2.0 angstrom resolution in the absence of its C-terminal helix and nucleotide. The 3D structure of CNB-L is in a twofold symmetric form. Each protomer shows high structure similarity to that of cGMP-binding domain-containing proteins, and likely mimics their nucleotide-free conformation. A key residue, Glu17, mediates the dimerization and prevents binding of cNMP to the canonical ligand-pocket. The structurally observed dimer of CNB-L is stable in solution, and thus is likely to be biologically relevant. (C) 2015 Elsevier Inc. All rights reserved.
分类: 医学、药学 >> 中医学与中药学 提交时间: 2020-05-05
摘要: 类风湿关节炎(RA)是一种自身免疫性疾病。胡蜂毒被认为是云南景颇族的一种传统民间药物,具有治疗类风湿性关节炎的作用。本研究旨在探讨胡蜂毒对实验性大鼠类风湿性关节炎的改善作用。我们建立了II型胶原(CII)诱导的SD大鼠关节炎(CIA)模型,并检测了炎症抑制作用和自身免疫反应。通过对患肢的肿胀、组织病理学评分及组织病理学改变来评价胡蜂毒(WV)的抗关节炎作用。检测了IL-6、TNF-α和IL-1β的表达水平以及外周血中炎症细胞的数量来。采用流式细胞术检测大鼠脾脏T细胞亚群比例的变化,同时测定脏器指数和免疫血清球蛋白水平。结果表明,不同剂量的WV(0.125、0.25、0.5 mg/kg)对CIA大鼠足肿胀和关节炎评分有显著的缓解作用(P < 0.05)。WV(0.25、0.5 mg/kg)能减轻大鼠踝关节滑膜组织病变,滑膜细胞增生、炎性细胞浸润的组织病理学评分(P < 0.05)。在免疫调节方面,0.5 mg/kg WV可降低免疫血清球蛋白水平(P < 0.05),我们进一步发现,0.5 mg/kg的WV可抑制Th细胞的免疫应答,同时显著增强脾脏细胞中Tc细胞和Treg细胞的功能(P < 0.05)。WV的免疫抑制作用类似于其对大鼠血清中IL-1β、TNF-α、IL-8、IL-6、cox-2和PGE2水平的抑制。综上所述,这些发现表明WV具有抗关节炎的活性,这可能与它们对免疫的调节和抗炎作用有关。
分类: 天文学 >> 天文学 提交时间: 2023-02-19
摘要: Galactic supernova remnants (SNRs) and their environments provide the nearest laboratories to study SN feedback. We performed molecular observations toward SNR W49B, the most luminous Galactic SNR in the X-ray band, aiming to explore signs of multiple feedback channels of SNRs on nearby molecular clouds (MCs). We found very broad HCO+ lines with widths of dv = 48--75 km/s in the SNR southwest, providing strong evidence that W49B is perturbing MCs at a systemic velocity of $V_{LSR}=61$--65 km/s, and placing W49B at a distance of $7.9\pm 0.6$ kpc. We observed unusually high-intensity ratios of HCO+ J=1-0/CO J=1-0 not only at shocked regions ($1.1\pm 0.4$ and $0.70\pm 0.16$), but also in quiescent clouds over 1 pc away from the SNR's eastern boundary (> 0.2). By comparing with the magnetohydrodynamics shock models, we interpret that the high ratio in the broad-line regions can result from a cosmic-ray (CR) induced chemistry in shocked MCs, where the CR ionization rate is enhanced to around 10--100 times of the Galactic level. The high HCO+/CO ratio outside the SNR is probably caused by the radiation precursor, while the luminous X-ray emission of W49B can explain a few properties in this region. The above results provide observational evidence that SNRs can strongly influence the molecular chemistry in and outside the shock boundary via their shocks, CRs, and radiation. We propose that the HCO+/CO ratio is a potentially useful tool to probe an SNR's multichannel influence on MCs.
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.