分子拥挤条件下生物大分子性质研究

细胞中成千上万种生物分子以不同的浓度发挥着各自的生理作用,但是体外研究中常常忽略细胞内的拥挤环境,随着分子拥挤理论的提出,体外添加大分子拥挤试剂被越来越多的生物学家和化学家所重视,众多的研究结果显示分子拥挤试剂的加入对细胞内的生物大分子的性质造成了一定的影响。从分子拥挤试剂对蛋白质折叠与聚集以及核酸分子结构与性质的影响等方面探讨了拥挤环境下生物大分子的性质和功能,为以后大分子拥挤条件下生物分子的研究提供一定的参考依据。     

乳铁蛋白分子结构及其抗菌机制

乳铁蛋白是一种单体糖蛋白,是哺乳动物非特异性免疫系统的第一道防线,具有防御微生物感染的功能。分析了乳铁蛋白氨基酸组成、多肽链折叠、铁结合结构、分子表面特性等与抗菌有关的分子结构。综述了乳铁蛋白抗微生物活性的作用机制,包括限制Fe3+利用,抑制细菌生物膜形成,与负电性生物大分子结合,降解细菌毒力因子以及阻止细菌入侵等。     

综述: 冷冻电镜技术在表观遗传学研究中的应用

染色质装配、修饰和重塑复合体,以及它们和核小体、染色质等一起形成的超大分子复合体的精细结构解析,对于在原子水平揭示表观遗传信息建立、维持和调控的分子机制至关重要．近年来,迅速发展的冷冻电镜三维重构技术对于解析这些多亚基、大分子质量、柔性超大分子复合体的结构带来了很好的机遇．本文综述了冷冻电镜三维重构技术在表观遗传学相关的结构研究领域中的一些应用和进展．     

三维电子显微镜方法进展

从生物样品（细胞或大分子）的电镜图象重组其三维结构的方法近年取得了重大进展,这是冷冻电镜样品制备、电镜设备、图象处理和分析方法等几方面进步的综合结果。三维电镜方法的进步和完善,使细胞和学家得以了解在复杂的细胞过程中各种相关细胞器之间的空间关系,而使分子生物学家不仅可以研究那些能够形成二维结晶的样品,并为分析具有重要生物功能但不能形成二维结晶的大分子或分子聚休物的结构提供了一种强大的手段。     

细胞穿膜肽介导生物大分子入胞机制研究进展

生物大分子药物与传统治疗方式相比作用靶点具有高度的专一性,成为21世纪药物研发中最具发展前景的领域之一,但由于细胞膜的天然屏障作用致使许多潜在的胞内药物靶标无法应用于新药研究。细胞穿膜肽(cell-penetrating peptides,CPP)是一类具有穿膜功能的小分子短肽,可高效携带核酸、蛋白质等生物大分子穿过细胞膜进入胞质发挥功能,在介导生物大分子药物入胞上有着高效、低毒等诸多优势,但仍存在效率低、靶向性差等问题。CPP携带货物分子入胞的方式可以根据是否依赖能量分为直接入胞和内吞。直接入胞依据孔隙形成的方式不同分为四种模型:桶板模型、超环面模型、地毯模型和反向胶团模型。内吞则根据受体的不同又分为巨胞饮、网格蛋白介导的内吞、小窝蛋白介导的内吞、硫酸乙酰肝素蛋白聚糖介导的内吞以及神经毡蛋白-1介导的内吞。CPP自身的类型、浓度、效应分子的物理化学性质以及分子大小都会影响CPP的入胞过程,进而决定CPP携带生物大分子入胞的途径。对CPP介导生物大分子的入胞机制进行综述,为研究更加高效、靶向性强的CPP提供依据,从而推动其在生物、医学领域的应用。     

单颗粒电子显微学的研究进展

单颗粒电子显微学是一种新型的结构生物学技术和方法,一方面,其解析生物大分子复合体结构的分辨率日益提高,可以达到近原子分辨率,提供大蛋白分子或复合体的精细结构;另一方面,还可以解析生物大分子在不同功能状态下的结构及变化,对于揭示生物大分子复合体结构的作用机理具有重要作用。本文就单颗粒电子显微学的研究进展作一综述。     

液-液相分离在细胞信号调控过程中的作用机制

近年来,液-液相分离(简称相分离)因其独特的功能与组织性,在细胞生物学研究中发展迅速。细胞内部分蛋白质及核酸(多为RNA)等生物大分子通过由多种弱多价相互作用及构象熵共同介导的相变(phase transition)形成无膜细胞器(membraneless organelles, MLOs)。这些无膜结构具有明显的流体性质,包括其圆形外表、可浸润、滴落和彼此融合,并具有动态的内部成分交换。在体内形成的无膜细胞器,广泛参与到包括细胞膜信号传导、膜结合蛋白质组装、染色质重塑、RNA代谢、突触传递、活跃转录中心形成、有丝分裂结构形成,以及蛋白质病理性转变等多种重要的细胞内信号调控过程。本文从相分离的研究背景,相分离发生的分子机制,正常相分离过程参与的多种细胞生理活动,异常相分离与神经性疾病及癌症发生的关系等方面,阐述了生物大分子的相分离在细胞信号调控过程中的普遍性及重要作用,并对研究相分离的实验技术和常用的相分离数据库进行了介绍。生物大分子相分离行为的发现,为重新理解众多结构及细胞生物学现象提供了全新的角度,生物大分子相分离可能作为一种新的生物学过程,帮助重新认识众多信号通路的调控方式,也有望为相关疾病的治疗提供新的方向。     

生物物理学报作者须知

1编辑方针《生物物理学报》是中国生物物理学会主办的学术期刊,发表有关生物物理学、分子生物学和细胞生物学领域基础研究和应用研究方面具有原创性的高水平研究论文、快报和综述文章。本刊将把重点放在分子与细胞水平的研究工作。特别欢迎以下方面的投稿:蛋白质组学,生物大分子的结构与功能,生物膜的结构与功能,生物信息学,细胞的信号转导,脑和认知功能的分子和细胞生物学基础,环境(光、声、电磁场、力和辐射)对生物作用的分子与细胞生物学机制,生命运动中各种分子、细胞和系统过程的理论模拟,以及生物物理、分子生物学与细胞生物学研究的…     

冷冻电镜技术在表观遗传学研究中的应用

染色质装配、修饰和重塑复合体,以及它们和核小体、染色质等一起形成的超大分子复合体的精细结构解析,对于在原子水平揭示表观遗传信息建立、维持和调控的分子机制至关重要.近年来,迅速发展的冷冻电镜三维重构技术对于解析这些多亚基、大分子质量、柔性超大分子复合体的结构带来了很好的机遇.本文综述了冷冻电镜三维重构技术在表观遗传学相关的结构研究领域中的一些应用和进展.     

物种共存理论研究进展

群落内的多物种如何共存是群落生态学的核心研究内容之一。经典的物种共存理论强调物种之间的生态位分化,注重具体共存机制的研究。这种以具体共存机制为研究对象的方法一定程度上促进了当代物种共存理论框架的形成。在当代物种共存理论框架下,物种间的差异被划分为两类综合性的抽象差异——生态位差异和平均适合度差异,前者促进物种共存,对应稳定化机制;后者导致竞争排除,对应均等化机制。本文在简要回顾经典物种共存理论的基础上,介绍了当代物种共存理论的框架(包括理论的形成和定义)、基于该理论的部分实验验证工作及其在一些重要生态学问题中的应用。当代物种共存理论不仅揭示了群落内物种是如何共存的这一基本理论问题,更重要的是在全球变化的背景下该理论对生物多样性的保护和管理具有重要的应用价值。期望本文的介绍有助于国内生态学和生物多样性工作者了解当代物种共存理论,并将其应用于群落构建和生物多样性维持机制等方面的研究。     

尿酸钠结晶诱导痛风性关节炎动物模型研究进展

痛风性关节炎是由于机体嘌呤代谢紊乱,导致血内尿酸增高而引起尿酸盐在组织沉积的疾病,本文简要介绍大鼠尿酸钠结晶急性足跖肿胀模型、大鼠尿酸钠结晶急性痛风性踝关节炎模型、小鼠与大鼠尿酸钠结晶皮下气囊法急性痛风性滑膜炎模型和家兔尿酸钠结晶急性膝关节炎模型的制作方法进展。将有益于抗痛风性关节炎药物研究时的更多选择应用。     

Bradykinin receptor 2 extends inflammatory cell recruitment in a model of acute gouty arthritis

The aim of this study was determine the effect of bradykinin receptor antagonism on MSU crystal-induced chemokine production and leukocyte recruitment. Mice were injected intraperitoneally with monosodium urate (MSU) crystals ± bradykinin B1- or B2 receptor antagonists, Des-Arg-HOE-140 and HOE-140, respectively. MSU crystal-induced chemokine production and leukocyte recruitment in the peritoneum were measured over 24h and B1 and B2 receptor expression on leukocytes and peritoneal membrane was determined by flow cytometry and fluorescence microscopy. Data analysis showed that only B2 receptor antagonism decreased monocyte and neutrophil infiltration 24 h post MSU crystal administration. Decreased leukocyte infiltration was associated with reduced monocyte (CCL2) chemokine levels. MSU crystal-induced damage to the surrounding visceral membrane was also attenuated in the presence of B2 receptor antagonism. Together, these data show that bradykinin receptor 2 plays a role in maintaining MSU crystal-induced leukocyte infiltration and membrane permeability and identify the B2 receptor as a potential therapeutic target for managing inflammation in gout.     

Formation of leukotrienes and hydroxy acids by human neutrophils and platelets exposed to monosodium urate

Monosodium urate (MSU) crystals stimulate the production of arachidonic acid metabolites by human neutrophils and platelets. Neutrophils exposed to MSU generated leukotriene B (LTB), 6-trans-LTB4, 12-epi-6-trans-LTB4, and 5S, 12S DHETE from endogenous sources of arachidonate. In addition to these metabolites both monohydroxyeicosatetraenoic acids (i.e., 5-HETE) and omega-oxidation products (i.e., 2O -COOH LTB4) were formed by neutrophils exposed to MSU. Addition of exogenous arachidonic acid led to increased formation of each of these metabolites. When neutrophils were treated with colchicine (10 microM), LTB4 but not 5-HETE formation was impaired. (1-14C)Arachidonate-labeled platelets exposed to MSU released (1-14C)-arachidonate, (14C)-12 HETE, (14C)-HHT and (14C)-thromboxane B2. Results indicate that MSU stimulates arachidonic acid metabolism in both human neutrophils and platelets. Moreover, they suggest not only that metabolites of arachidonate may be considered as possible candidates for mediators of inflammation in crystal-associated diseases, but that colchicine blocks the formation of LTB4.     

Determination of urate crystal formation using flow cytometry and microarea X-ray diffractometry

Gout is known to be induced by monosodium urate (MSU) crystals. The formation of MSU crystals is the first step of gouty inflammation. Detecting the early stage of crystallization accurately is considered to be important in understanding the mechanism of gouty arthritis. In this study, we employed flow cytometry (FCM) to detect small amounts of crystals produced in a supersaturated solution of uric acid. FCM was sensitive and crystals were determined at 2 h after the beginning of reaction. Gamma-globulin accelerated the formation rate time-dependently and dose-dependently. Low levels of lactic acid (less than 1.0 mg/ml) did not affect the formation rate but lactic acid of 2.0 mg/ml enhanced the formation of urate crystals. The crystals obtained with 2.0 mg/ml of lactic acid were analyzed with a microarea X-ray diffractometer and were shown to be a mixture of MSU and uric acid. FCM is a very useful method to determine the formation of crystals. Furthermore, analysis with a microarea X-ray diffractometer can provide detailed information about crystal composition.     

Monosodium Urate Crystals Promote Innate Anti-Mycobacterial Immunity and Improve BCG Efficacy as a Vaccine against Tuberculosis

A safer and more effective anti-Tuberculosis vaccine is still an urgent need. We probed the effects of monosodium urate crystals (MSU) on innate immunity to improve the Bacille Calmette-Guerin (BCG) vaccination. Results showed that in vitro MSU cause an enduring macrophage stimulation of the anti-mycobacterial response, measured as intracellular killing, ROS production and phagolysosome maturation. The contribution of MSU to anti-mycobacterial activity was also shown in vivo. Mice vaccinated in the presence of MSU showed a lower number of BCG in lymph nodes draining the vaccine inoculation site, in comparison to mice vaccinated without MSU. Lastly, we showed that MSU improved the efficacy of BCG vaccination in mice infected with Mycobacterium tuberculosis (MTB), measured in terms of lung and spleen MTB burden. These results demonstrate that the use of MSU as adjuvant may represent a novel strategy to enhance the efficacy of BCG vaccination.     

Biomacromolecular localization in bacterial cells by the diffusion and capture mechanism

Subcellular localization of biomacromolecules (nucleotides and proteins) is the base for their proper function in bacterial cells. One model to explain the localization of biomacromolecules, particularly proteins, is “diffusion and capture”. In this model, proteins are localized by diffusion through the cytoplasm or the membrane until binding to another protein or proteins that were already previously sequestered in cells. The use of fusions with fluorescent proteins to follow the fate of biomacromolecules has given new insight into the molecular localization mechanisms in living cells. Here, several proteins following a diffusion and capture mechanism to reach their proper location in the cells are presented. Some RNAs also seem to localize by this mechanism. It is an intrinsic feature that the information for molecular localization should exist in the sequences of protein itself. However, very little information has been available in this field to date.     

Pycnogenol attenuates the inflammatory and nitrosative stress on joint inflammation induced by urate crystals

Acute gouty arthritis results from monosodium urate (MSU) crystal deposition in joint tissues. Deposited MSU crystals induce an acute inflammatory response which leads to damage of joint tissue. Pycnogenol (PYC), an extract from the bark of Pinus maritime, has documented antiinflammatory and antioxidant properties. The present study aimed to investigate whether PYC had protective effects on MSU-induced inflammatory and nitrosative stress in joint tissues both in vitro and in vivo. MSU crystals upregulated cyclooxygenase 2 (COX-2), interleukin 8 (IL-8) and inducible nitric oxide synthase (iNOS) gene expression in human articular chondrocytes, but only COX-2 and IL-8 in synovial fibroblasts. PYC inhibited the up-regulation of COX-2, and IL-8 in both articular chondrocytes and synovial fibroblasts. PYC attenuated MSU crystal induced iNOS gene expression and NO production in chondrocytes. Activation of NF-κB and SAPK/JNK, ERK1/2 and p38 MAP kinases by MSU crystals in articular chondrocytes and synovial fibroblasts in vitro was attenuated by treatment with PYC. The acute inflammatory cell infiltration and increased expression of COX-2 and iNOS in synovial tissue and articular cartilage following intra-articular injection of MSU crystals in a rat model was inhibited by coadministration of PYC. Collectively, this study demonstrates that PYC may be of value in treatment of MSU crystal-induced arthritis through its anti-inflammatory and anti-nitrosative activities.     

Formation of leukotrienes and hydroxy acids by human neutrophils and platelets exposed to monosodium urate

Monosodium urate (MSU) crystals stimulate the production of arachidonic acid metabolites by human neutrophils and platelets. Neutrophils exposed to MSU generated leukotriene B₄(LTB₄). 6- -LTB₄, 12- -6- -LTB₄, and 5S, 12S DHETE from endogenous sources of arachidonate. In addition to these metabolites both monohyroxyeicosatetraenoic acids (i.e., 5-HETE) and w-oxidation products (i.e., 20-COOH LTB₄) were formed by neutrophils exposed to MSU. Addition of exogenous arachidonic acid led to increased formation of each of these metabolites. When neutrophils were treated with colchicine (10 uM), LTB₄ but 5-HETE formation was impaired. (1-¹⁴C) Arachidonate-labeled platelets exposed to MSU released (1-¹⁴C)-arachidonate. (¹⁴C)-12 HETE, (¹⁴C)-HHT and (¹⁴C)-thromboxane B₂. Results indicate that MSU stimulates arachidonic acid metabolism in both human neutrophils and platelets. Moreover, they suggest not only that metabolites of arachidonate may be considered as possible candidates for mediators of inflammation in crystal-associated diseases, but that colchicine blocks the formation of LTB₄.