Calcium binding mode of gamma-carboxyglutamic acids in conantokins.

Conantokin-T (con-T) and conantokin-G (con-G) are two highly homologous peptide toxins found in Conus venom. The former is a 21-residue peptide with four gamma-carboxyglutamic acid (Gla) residues (at positions 3, 4, 10 and 14), while the latter is a 17-residue peptide with five gamma-carboxyglutamic acid residues (at positions 3, 4, 7, 10 and 14). Despite the apparent similarity in number and relative positions of the gamma-carboxyglutamic acid residues, (113)Cd-NMR studies indicated a distinct metal binding behavior for con-G and con-T. There appears to be four binding sites in con-G in contrast to one metal binding site in con-T. To elucidate the mode of calcium binding by the gamma-carboxyglutamic acid residues in these conantokins, we designed various analogous peptides with their gamma-carboxyglutamic acid replaced by other amino acid residues. (113)Cd-NMR experiments on conantokin analogues reveal that the major difference in the number of metal binding sites between con-G and con-T is due to the residue at position 7. We also performed molecular simulations to calculate the relative binding free energies of several potential binding sites. Based on our theoretical and experimental results, we propose a 'four-site' binding model for conantokin-G and a 'single-site' binding model for conantokin-T.     

Characterization and structural analyses of nonspecific lipid transfer protein 1 from mung bean

Plant nonspecific lipid transfer proteins (nsLTPs) are thermal stable proteins that are capable of transferring lipid molecules between bilayers in vitro. This family of proteins, abundant in plants, is proposed to be involved in defense, pollination, and germination; the in vivo biological function remains, however, elusive. Here we report the purification and sequencing of an nsLTP1 from mung bean sprouts. We have also determined the solution structure of this nsLTP1, which represents the first 3D structure of the dicotyledonous nsLTP1 family. The global fold of mung bean nsLTP1 is similar to those of the monocotyledonous nsLTP1 structures and consists of four alpha-helices stabilized by four disulfide bonds. There are, however, some notable differences in the C-terminal tails and internal hydrophobic cavities. Circular dichroism and fluorescence spectroscopy were used to compare the thermodynamics and lipid transfer properties of mung bean nsLTP1 with those of rice nsLTP1. Docking of a lipid molecule into the solution structure of mung bean nsLTP1 reveals similar binding cavities and hydrophobic interactions as in rice nsLTP1, consistent with their comparable lipid transfer properties measured experimentally.     

Quorum Sensing Is a Language of Chemical Signals and Plays an Ecological Role in Algal-Bacterial Interactions

Algae are ubiquitous in the marine environment, and the ways in which they interact with bacteria are of particular interest in the field of marine ecology. The interactions between primary producers and bacteria impact the physiology of both partners, alter the chemistry of their environment, and shape microbial diversity. Although algal-bacterial interactions are well known and studied, information regarding the chemical-ecological role of this relationship remains limited, particularly with respect to quorum sensing (QS), which is a system of stimuli and response correlated to population density. In the microbial biosphere, QS is pivotal in driving community structure and regulating behavioral ecology, including biofilm formation, virulence, antibiotic resistance, swarming motility, and secondary metabolite production. Many marine habitats, such as the phycosphere, harbor diverse populations of microorganisms and various signal languages (such as QS-based autoinducers). QS-mediated interactions widely influence algal-bacterial symbiotic relationships, which in turn determine community organization, population structure, and ecosystem functioning. Understanding infochemicals-mediated ecological processes may shed light on the symbiotic interactions between algae host and associated microbes. In this review, we summarize current achievements about how QS modulates microbial behavior, affects symbiotic relationships, and regulates phytoplankton chemical-ecological processes. Additionally, we present an overview of QS-modulated co-evolutionary relationships between algae and bacterioplankton, and consider the potential applications and future perspectives of QS.     

双歧三联活菌胶囊对急性胰腺炎患者肠黏膜屏障功能的保护作用

目的探讨双歧三联活菌胶囊对急性胰腺炎患者肠黏膜屏障功能的保护作用。方法选取急性胰腺炎患者66例,随机分为观察组和对照组。两组患者均予以禁食水、持续胃肠减压、解痉镇痛、抗感染、抑制胃酸分泌、生长抑素、改善局部微循环和保持水电解质酸碱平衡等常规治疗。观察组患者加用双歧杆菌三联活菌胶囊420mg水化后自胃管灌注,夹管1．5h,3次／d,连用7d。观察两组患者的治疗前后肠黏膜屏障功能的变化情况,并比较其临床疗效。结果治疗7d后,两组患者血清内毒素、TNF—α和D-乳酸水平均有明显下降（P〈0．05或P〈0．01）,且观察组下降值比对照组更明显（P〈0．05）;同时观察组患者临床总有效率为93．94％,明显高于对照组的75．76％（χ2=4．24,P〈0．05）。结论双歧杆菌三联活菌胶囊治疗急性胰腺炎效果较好,能降低血清内毒素、TNF-α和D-乳酸水平,对患者肠黏膜屏障功能具有良好的保护作用。