地球工程开展现状及其对生物多样性的影响

与气候相关的地球工程(Climate-Related Geoengineering,简称地球工程)是为了减缓气候变化及其影响的目的,采取一系列大规模的人工技术和方法对地球环境或气候系统进行干预.地球工程的研究和开展受到越来越多的关注,已经成为《生物多样性公约》讨论的焦点之一.地球工程项目在全球进行了不同程度的实验和推广,与我国的利益密切相关.本文通过参与相关会议讨论以及对会议材料和相关文献的整理,梳理了地球工程的定义和内涵、介绍了不同类型地球工程的开展现状,分析了地球工程对生物多样性的潜在影响,并阐述了《生物多样性公约》对地球工程的争论.研究表明:地球工程主要通过改变区域或局地的气候和环境间接影响生物多样性,由于目前对地球工程的影响缺乏足够了解,对生物多样性有潜在影响的大规模地球工程将被禁止,但节能减排工作的义务使地球工程仍然具有应用前景.笔者对未来地球工程发展提出了自己的意见,认为地球工程技术的研究应兼顾高效、低廉和环境安全的标准,开展地球工程活动应采取预先防范措施,并探讨建立监管机制的可能性.     

低温辐射聚合用于酵母细胞固定化的高分子载体的研究

本文报导了一种新的用于酵母细胞固定化的高分子载体,该载体是用亲水／疏水性单体在－７８℃辐射聚合而成,讨论交联剂,乳化剂,增韧剂和致孔剂的加入对载体的制备以及载体固定化细胞的雪酵醇量的影响,同时对固定化细胞的重复反应性做了研究。     

Enhancement of radiation-induced apoptosis by 6-formylpterin

Radiation-induced apoptosis and its possible enhancement in the presence of 6-formylpterin (6-FP), a metabolite of folic acid, were examined in human myelomonocytic lymphoma U937 cells. When cells were treated with 6-FP at a nontoxic concentration of 300 μM, and then exposed to X-rays at a dose of 10 Gy, significant enhancement of radiation-induced apoptosis as determined by nuclear morphological change, phosphatidylserine (PS) externalization and DNA fragmentation were observed. Flow cytometry for the detection of intracellular hydrogen peroxide (H₂O₂) revealed that 6-FP increased the formation of intracellular H₂O₂, which further increased when the cells were irradiated. Decrease of mitochondria trans-membrane potential (MMP), release of cytochrome c from mitochondria, and activation of caspase-3 were enhanced after the combined treatment. Remarkable activation of protein kinase C δ (PKC δ) and its translocation from cytosol to mitochondria were detected in combined treatment. Increase of intracellular Ca₂₊ concentrations ([Ca₂₊]i) was also observed, however, neither calpain I nor calpain II could inhibit the apoptosis. In addition, c-Jun NH₂-terminal kinase ( JNK) activation was not enhanced in the combined treatment. A protein involved in a caspase-independent apoptosis pathway, apoptosis inducing factor (AIF), remained unchanged even 3 h after treatment. These results indicate that intracellular H₂O₂ generated by 6-FP enhances radiation-induced apoptosis via the mitochondria-mediated caspase-dependent pathway, with the active involvement of PKC δ.     

CRM1 protein-mediated regulation of nuclear clusterin (nCLU), an ionizing radiation-stimulated, Bax-dependent pro-death factor

Expression of the clusterin (CLU) gene results in the synthesis of a conventional secretory isoform set (pre- and mature secretory clusterin proteins, psCLU/sCLU), as well as another set of intracellular isoforms, appearing in the cytoplasm (pre-nuclear CLU, pnCLU) and in the nucleus as an ～55-kDa mature nuclear clusterin (nCLU) form. These two isoform sets have opposing cell functions: pro-survival and pro-death, respectively. Although much is known about the regulation and function of sCLU as a pro-survival factor, the regulation and function of endogenous nCLU in cell death are relatively unexplored. Here, we show that depletion of endogenous nCLU protein using siRNA specific to its truncated mRNA increased clonogenic survival of ionizing radiation (IR)-exposed cells. nCLU-mediated apoptosis was Bax-dependent, and lethality correlated with accumulation of mature nCLU protein. nCLU accumulation was regulated by CRM1 because binding between CRM1 and nCLU proteins was significantly diminished by leptomycin B (LMB), and nuclear levels of nCLU protein were significantly enhanced by LMB and IR co-treatment. Moreover, LMB treatment significantly enhanced IR-induced nCLU-mediated cell death responses. Importantly, bax(-/-) and bax(-/-)/bak(-/-) double knock-out cells were resistant to nCLU-mediated cell death, whereas bak(-/-) or wild-type bax(+/+)/bak(+/+) cells were hypersensitive. The regulation of nCLU by CRM1 nuclear export/import may explain recent clinical results showing that highly malignant tumors have lost the ability to accumulate nCLU levels, thereby avoiding growth inhibition and cell death.     

PBP Active Site Flexibility as the Key Mechanism for β-Lactam Resistance in Pneumococci

Penicillin-binding proteins (PBPs), the main targets of β-lactam antibiotics, are membrane-associated enzymes that catalyze the two last steps in the biosynthesis of peptidoglycan. In Streptococcus pneumoniae, a major human pathogen, the surge in resistance to such antibiotics is a direct consequence of the proliferation of mosaic PBP-encoding genes, which give rise to proteins containing tens of mutations. PBP2b is a major drug resistance target, and its modification is essential for the development of high levels of resistance to piperacillin. In this work, we have solved the crystal structures of PBP2b from a wild-type pneumococcal strain, as well as from a highly drug-resistant clinical isolate displaying 58 mutations. Although mutations are present throughout the entire PBP structure, those surrounding the active site influence the total charge and the polar character of the region, while those in close proximity to the catalytic nucleophile impart flexibility onto the β3/β4 loop area, which encapsulates the cleft. The wealth of structural data on pneumococcal PBPs now underlines the importance of high malleability in active site regions of drug-resistant strains, suggesting that active site “breathing” could be a common mechanism employed by this pathogen to prevent targeting by β-lactams.     

敦煌绿洲夏季典型晴天地表辐射和能量平衡及小气候特征

 利用“我国西北干旱区陆-气相互作用试验”加强期(IOP)在甘肃省敦煌绿洲观测的资料,系统地分析了夏季典型晴天敦煌地表辐射收支和地表能量平衡特征及小气候特征,结果发现：敦煌绿洲总辐射特别大,其峰值高达1 038.1 w·m-2;地表净辐射也高于其它地区,白天能超过600 w·m-2;在地表能量分配中,感热、潜热和地热流量的日积分值的量级相当,白天地热流量比潜热要大,几乎与感热相当;地表反照率除中午比较接近荒漠戈壁的值外,其它时候均明显比荒漠戈壁的值小;Bowen比在白天1～2之间,比一般灌溉地区要大。地表能量不平衡差额较大,这可能与水平热通量的影响有很大关系。另外,还首次发现了比较可观的下沉气流,部分证实了绿洲与荒漠之间存在的热力环流。     

CPR-C4 is a highly conserved novel protease from the Candidate Phyla Radiation with remote structural homology to human vasohibins

The Candidate Phyla Radiation is a recently uncovered and vast expansion of the bacterial domain of life, made up of largely uncharacterized phyla that lack isolated representatives. This unexplored territory of genetic diversity presents an abundance of novel proteins with potential applications in the life-science sectors. Here, we present the structural and functional elucidation of CPR-C4, a hypothetical protein from the genome of a thermophilic Candidate Phyla Radiation organism, identified through metagenomic sequencing. Our analyses revealed that CPR-C4 is a member of a family of highly conserved proteins within the Candidate Phyla Radiation. The function of CPR-C4 as a cysteine protease was predicted through remote structural similarity to the Homo sapiens vasohibins and subsequently confirmed experimentally with fluorescence-based activity assays. Furthermore, detailed structural and sequence alignment analysis enabled identification of a noncanonical cysteine-histidine-leucine(carbonyl) catalytic triad. The unexpected structural and functional similarities between CPR-C4 and the human vasohibins suggest an evolutionary relationship undetectable at the sequence level alone.     

同步辐射在显微CT中的应用

计算机X射线断层成像技术（CT）是利用X射线的穿透能力对物体进行扫描,所得信号经过反投影的算法而得到物体二维分布的一种成像方法,已经在医学诊断、工业探伤等领域广泛应用。但是由于实验室光源的低通量,光源点大小及其单色性等限制了其向高分辨发展,通常其分辨率在0．5mm左右。利用微焦点X射线源作为光源的显微CT分辨率可以达到微米量级,但是由于其光通量低且为非单色光,对不同样品有不同程度的束线硬化,影响了其真实分辨率。同步辐射作为一种新兴的光源有高亮度、高光子通量、高准直性、高极化性、高相干性及宽的频谱范围的特点,配合高分辨的X射线探测器,可以发展同步辐射显微CT,其分辨率可达10μm以下。利用同步辐射的高空间相干性开展位相衬度显微CT的研究,对低吸收物质也可以清晰三维成像。新建的上海光源的X射线成像及生物医学应用线站开展了三维显微CT方面的研究,经过初步试验,得到了较好的结果。