Color regulation in the archaebacterial phototaxis receptor phoborhodopsin (sensory rhodopsin II)

Phoborhodopsin, a repellent phototaxis receptor in Halobacterium halobium, exhibits vibrational fine structure, a feature that has not been identified for any other rhodopsin pigment at physiological temperatures. This conclusion follows form analysis of the absorption properties of the pigment in H. halobium membranes containing native retinal and an array of retinal analogues. The absorption spectrum of the native pigment has a maximum at 487 nm with a pronounced shoulder at 460 nm; however, the bandwidth is that expected for a single retinylidene species. Gaussian band-shape simulation with a spacing corresponding to the vibrational frequencies of polyene stretching modes reproduces the structured absorption spectra of native pigment as well as of analogue phoborhodopsin. Absorption shifts produced by a series of dihydroretinal and other retinal analogues strongly indicate that the dominant factor regulating the color of the pigment is planarization of the retinal ring with respect to the polyene chain.     

Mechanism of adenylate kinase. Structural and functional demonstration of arginine-138 as a key catalytic residue that cannot be replaced by lysine

Replacement of the arginine-138 of adenylate kinase (AK) by lysine or methionine resulted in a decrease in kcat by a factor of 10(4), increases in Km by a factor of 10-20, and relatively little changes in dissociation constants. Proton nuclear magnetic resonance (NMR) studies were then undertaken to obtain structural information for quantitative interpretation of the kinetic data. Since the lysine mutant (R138K) represents a conservative mutation with surprisingly large effects on kinetics, structural studies were focused on the wild type (WT) and R138K. The results and conclusions are summarized as follows: (i) The aromatic spin systems of WT and R138K were assigned from total correlated spectroscopy (TOCSY). Comparison of the chemical shifts of aromatic protons, one-dimensional spectra, TOCSY, and nuclear Overhauser enhanced spectroscopy (NOESY) indicated that the conformation of R138K was almost unperturbed relative to that of WT. Thus Arg-138 is not important for the tertiary structure. (ii) Proton NMR titrations with AMP and MgATP suggested that substrate binding affinities and substrate-induced conformational changes are nearly identical between WT and R138K. Thus arginine-138 should not be involved in stabilizing the first substrate in the binary complex. (iii) Notable differences were observed between the proton NMR spectra of the WT and R138K complexes with the reaction mixture, which agrees with the perturbation in the Km values of R138K. The differences were analyzed in detail by using a "static reaction mixture'--p1, p5-bis(5'-adenosyl)pentaphosphate (MgAP5A). The aromatic spin systems of WT + MgAP5A and R138K + MgAP5A were partially assigned from various two-dimensional spectra.(ABSTRACT TRUNCATED AT 250 WORDS)     

Mechanism of adenylate kinase. Are the essential lysines essential?

Using site-specific mutagenesis, we have probed the structural and functional roles of lysine-21 and lysine-27 of adenylate kinase (AK) from chicken muscle expressed in Escherichia coli. The two residues were chosen since according to the nuclear magnetic resonance (NMR) model [Mildvan, A. S., & Fry, D. C. (1987) Adv. Enzymol. 58, 241-313], they are located near the alpha- and the gamma-phosphates, respectively, of adenosine 5'-triphosphate (ATP) in the AK-MgATP complex. In addition, a lysine residue (Lys-21 in the case of AK) along with a glycine-rich loop is considered "essential" in the catalysis of kinases and other nucleotide binding proteins. The Lys-27 to methionine (K27M) mutant showed only slight increases in kcat and Km, but a substantial increase (1.8 kcal/mol) in the free energy of unfolding, relative to the WT AK. For proper interpretation of the steady-state kinetic data, viscosity-dependent kinetics was used to show that the chemical step is partially rate-limiting in the catalysis of AK. Computer modeling suggested that the folded form of K27M could gain stability (relative to the wild type) via hydrophobic interactions of Met-27 with Val-179 and Phe-183 and/or formation of a charge-transfer complex between Met-27 and Phe-183. The latter was supported by an upfield shift of the methyl protons of Met-27 in 1H NMR. Other than this, the 1H NMR spectrum of K27M is very similar to that of WT, suggesting little perturbation in the global or even local conformations.(ABSTRACT TRUNCATED AT 250 WORDS)     

粤北南岭大宝山矿流域山水林田湖草修复阻力与优先级分析

遵循“防源、控流、治汇”理念,以粤北南岭大宝山矿区作为风险源,以所在流域为研究区,分析研究区主要阻力因素,采用最小累积阻力模型建立区域生态阻力面;利用Jenks自然断点法,分析生态修复优先级,提出分区治理重点和对策。研究结果表明：研究区综合阻力系数处于9-32之间,各评价指标的阻力面空间分布格局相似,其阻力值呈现出东南部大,西北部小的空间格局;长期的矿业开采污染了流域生态环境,且距离矿区越近的区域生态修复的优先性越高。将研究区分为4个优先级区,各区修复优先性依次为Ⅰ区 > Ⅱ区 > Ⅲ区 > Ⅳ区。Ⅰ区重点在于治水,提高pH、降低重金属有效态含量和增加地表植被覆盖度。Ⅱ区重点在于河流治理与治土,确保污染减排,增强拦泥库的废水调节。Ⅲ区、Ⅳ区核心在治土,逐步改善土壤条件。研究结果为修复项目在时空尺度上落地和科学治理提供科学依据。     

乳粉中嗜热菌污染研究进展

嗜热菌是乳粉中的常见污染菌,是影响乳粉品质的一个重要因素。本文综述乳粉中嗜热菌的种类、污染源对乳品工业的危害及其控制手段的研究进展,为国内相关领域研究提供参考。     

CD36 aggravates podocyte injury by activating NLRP3 inflammasome and inhibiting autophagy in lupus nephritis

A major cause of proteinuria in lupus nephritis (LN) is podocyte injury, and determining potential therapeutic targets to prevent podocyte injury is important from a clinical perspective in the treatment of LN. CD36 is involved in podocyte injury in several glomerulopathies and was reported to be a vital candidate gene in LN. Here, we determined the role of CD36 in the podocyte injury of LN and the underlying mechanisms. We observed that CD36 and NLRP3 (NLR family pyrin domain containing 3) were upregulated in the podocytes of lupus nephritis patients and MRL/lpr mice with renal impairment. In vitro, CD36, NLRP3 inflammasome, and autophagy were elevated accompanied with increased podocyte injury stimulated by IgG extracted from lupus nephritis patients compared that from healthy donors. Knocking out CD36 with the CRISPR/cas9 system decreased the NLRP3 inflammasome levels, increased the autophagy levels and alleviated podocyte injury. By enhancing autophagy, NLRP3 inflammasome was decreased and podocyte injury was alleviated. These results demonstrated that, in lupus nephritis, CD36 promoted podocyte injury by activating NLRP3 inflammasome and inhibiting autophagy by enhancing which could decrease NLRP3 inflammasome and alleviate podocyte injury.Subject terms: Mechanisms of disease, Inflammasome, Lupus nephritis, Autophagy     

中国省域旅游业碳中和时空分异与模拟

旅游业碳中和的实现对于旅游业的绿色高质量发展和可持续发展至关重要。基于全国尺度以30个省份为分析单元,在承接团队前期关于旅游业碳达峰研究成果的基础上,借助土地利用数据、碳吸收系数和灰色预测模型分别测算与模拟了近20年和未来40年各省旅游业碳汇,通过旅游业碳中和指数反映旅游业碳排放和旅游业碳汇之间的动态变化,并利用空间自相关探索旅游业碳中和指数的时空差异。结果表明：（1）未来40年,我国省域旅游业碳汇总体呈现出"南北高,中间低"的空间分布特征,大多数省份的旅游业碳汇不断增长。东北部地区和长江流域以南各地区的旅游业碳汇较为富余,华东地区的山东、江苏和上海等省份的旅游业碳汇则相对匮乏。（2）不同情景中,低碳情景下的旅游业碳中和实现情况最好,有云南、四川和青海等7个省份在2060年之前实现了旅游业碳中和,而中等情景和基准情景下均仅有黑龙江和云南2个省份能够如期或提前实现。其中,西部和北部沿边省份的旅游业碳中和实现情况都要优于其它地区。（3）各省旅游业碳中和指数在未来40年的等级分区大致呈现出从Ⅰ级区逐步向Ⅴ级区转变的趋势,我国总体旅游业碳赤字率由2030年的96.67%逐渐降至2060年的76.67%。（4）未来40年,我国省域旅游业碳中和指数在空间上总体处于集聚态势,热点和冷点的空间分布特征较为明显,且演化趋势较为稳定。其中,热点区和次热点区主要分布在西北、西南、华南和东北地区,冷点区和次冷点区集中分布在华北、华中和华东地区。研究有效探讨了旅游业碳中和研究的理论与范式,并为中国旅游业碳中和的实现提供了一定的现实参考。     

钱江源国家公园森林物种组成和群落结构

全面了解以国家公园为主体的自然保护地体系木本植物物种组成,特别是珍稀濒危物种,分析其区系特征及不同植被类型群落结构现状,对国家公园物种保护和不同植被类型恢复具有重要指导意义。基于对钱江源国家公园全域的木本植物调查,详细分析了不同胸径大小级森林植被类型的物种组成、区系特征、种-个体曲线分析和结构特征。调查涵盖313个木本物种,温带分布的科多于热带分布的科(22/35),热带分布的属略少于温带分布的属(28/31);中国特有属7个,特有种101个,中国珍稀保护物种10个,世界自然保护联盟(IUCN)红色名录的近危、易危和濒危物种17个。在同等取样水平下,物种多样性在常绿阔叶林最高,天然针叶林次之,杉木林最低;全域所有个体及各林型的径级分布总体呈现明显的倒"J"形,群落总体上更新良好。研究发现钱江源国家公园物种丰富,但由于包含较多次生林等植被类型,整体温带多于热带区系成分,亟待采取措施恢复至典型中亚热带常绿阔叶林植被;研究对钱江源国家公园木本植物物种的多样性及其更新情况等科学和保护实践急需解决的基本问题做出了回答,也为未来钱江源国家公园生物多样性保护和恢复提供了科学依据。     

亚热带森林转换对土壤无脊椎动物群落结构的影响

受人类活动干扰的增加,亚热带森林频繁转换为次生林和人工林,可能显著影响土壤无脊椎动物群落结构及其生态功能,但当前的认识并不一致。因此,于2022年7月调查了亚热带天然常绿阔叶林转换为次生林、米槠人工林、杉木人工林后土壤无脊椎动物群落结构特征。共捕获土壤无脊椎动物659只,丰度为26540只/m²,隶属1门6纲13目59科,其中蚁科和球角 虫 兆 科为优势类群。森林转换改变了土壤无脊椎动物群落组成和多样性。天然林向米槠人工林和杉木人工林转换后,土壤无脊椎动物丰度和类群均明显降低,其中大型土壤无脊椎动物丰度的响应更为敏感,在2种林型中分别显著降低了33.58%和36.53%。尽管林型转换对土壤无脊椎动物群落多样性指数无显著影响,但改变了土壤无脊椎动物群落组成,其中天然林与杉木人工林群落组成极不相似(J ＜ 0.25),等节 虫 兆 科为杉木人工林优势类群,占比达到59.84%。冗余分析显示,土壤湿度、凋落物现存量和凋落物磷含量是影响土壤无脊椎动物群落的主要因子,对土壤无脊椎动物群落的解释率为69.30%。可见,林型转换可能通过改变土壤理化性质和凋落物质量,调控土壤无脊椎动物群落结构。     

一株兔源A型多杀性巴氏杆菌的分离鉴定和全基因组测序及分析

【背景】多杀性巴氏杆菌可导致猪肺疫、牛出血性败血症和兔出血性败血症等多种疾病,严重威胁多种动物畜牧养殖业的健康发展。【目的】重庆某兔场送检一批病死兔,为研究其病原和治疗方法,对病原进行了微生物分离和全基因组测序分析。【方法】从2022年重庆某兔场送检兔病料中进行细菌分离纯化、生化试验、16S rRNA基因鉴定、荚膜血清型分型、药敏试验和毒力基因检测,同时通过全基因组测序结果进行毒力、耐药基因注释和遗传进化等分子生物学信息分析。【结果】该菌为兔源A:ST74多杀性巴氏杆菌,命名为LXSS001,基因组序列上传到NCBI数据库(登录号为CP119523.1),药敏试验显示该菌对四环素、杆菌肽、复方新诺明和磺胺异恶唑耐药,对头孢噻肟、头孢哌酮和丁胺卡那等药物敏感。全基因组长度为2 480 671 bp,并注释到了58个毒力基因和9类药物的靶向抗药基因。通过联合建树表明其与3480株一致性最高。【结论】本研究完成了一株A型多杀性巴氏杆菌的分离鉴定和全基因组测序,并揭示了其与国内外其他分离株的进化关系,为多杀性巴氏杆菌的后续研究提供了参考依据。