Regulation of Arabidopsis cryptochrome 2 by blue-light-dependent phosphorylation

Cryptochromes are blue/ultraviolet-A light receptors that mediate various light responses in plants and animals. But the initial photochemical reaction of cryptochrome is still unclear. For example, although most photoreceptors are known to undergo light-dependent protein modification such as phosphorylation, no blue-light dependent phosphorylation has been reported for a cryptochrome. Arabidopsis cryptochrome 2 (cry2) mediates light regulation of seedling development and photoperiodic flowering. The physiological activity and cellular level of cry2 protein are light-dependent, and protein protein interactions are important for cry2 function. Here we report that cry2 undergoes a blue-light-dependent phosphorylation, and that cry2 phosphorylation is associated with its function and regulation. Our results suggest that, in the absence of light, cry2 remains unphosphorylated, inactive and stable; absorption of blue light induces the phosphorylation of cry2, triggering photomorphogenic responses and eventually degradation of the photoreceptor.     

Structure of full-length Drosophila cryptochrome

The cryptochrome/photolyase (CRY/PL) family of photoreceptors mediates adaptive responses to ultraviolet and blue light exposure in all kingdoms of life. Whereas PLs function predominantly in DNA repair of cyclobutane pyrimidine dimers (CPDs) and 6-4 photolesions caused by ultraviolet radiation, CRYs transduce signals important for growth, development, magnetosensitivity and circadian clocks. Despite these diverse functions, PLs/CRYs preserve a common structural fold, a dependence on flavin adenine dinucleotide (FAD) and an internal photoactivation mechanism. However, members of the CRY/PL family differ in the substrates recognized (protein or DNA), photochemical reactions catalysed and involvement of an antenna cofactor. It is largely unknown how the animal CRYs that regulate circadian rhythms act on their substrates. CRYs contain a variable carboxy-terminal tail that appends the conserved PL homology domain (PHD) and is important for function. Here, we report a 2.3-? resolution crystal structure of Drosophila CRY with an intact C terminus. The C-terminal helix docks in the analogous groove that binds DNA substrates in PLs. Conserved Trp?536 juts into the CRY catalytic centre to mimic PL recognition of DNA photolesions. The FAD anionic semiquinone found in the crystals assumes a conformation to facilitate restructuring of the tail helix. These results help reconcile the diverse functions of the CRY/PL family by demonstrating how conserved protein architecture and photochemistry can be elaborated into a range of light-driven functions.     

B2SINE RNA和HEXIM1蛋白相互作用的研究

构建了带FLAG多肽标签的hHEXIM1( HMBA-inducible protein 1)蛋白真核表达载体,在人胚胎肾细胞(human embryonic kidney 293 cells,HEK293 cells)中检测蛋白表达正确后,将该质粒转入小鼠的成纤维细胞(NIH3T3细胞)中,进行anti-FLAG的免...     

Antigen-specific interaction between T and B cells

It is well known that B cells require T-cell help to produce specific antibody. Classic experiments suggested that antigen-specific helper T cells interact with antigen-specific B cells via an antigen 'bridge', the B cells binding to one determinant on an antigen molecule (the 'hapten'), while the T cells at the same time recognize another determinant (the 'carrier'). T-helper cells bind specifically to antigen-presenting cells (APC), which have picked up and processed the appropriate antigen, and this interaction, like the interaction of T-helper cells with specific B cells, is restricted by products encoded by the major histocompatibility complex (MHC). Whereas conventional APC such as macrophages display no binding specificity for antigen, B cells have clonally distributed antigen-specific surface immunoglobulin receptors which would be expected to enhance their capacity to present antigen to T cells. These findings are difficult to reconcile with the simple 'antigen bridge' mechanism of interaction, because it is hard to visualize how the bimolecular complex (processed antigen plus MHC molecule) on the APC surface can resemble the trimolecular complex (antigen bound to surface immunoglobulin plus MHC molecule) on the B-cell surface. To address this problem, we have cloned and immortalized human antigen-specific B cells with Epstein-Barr virus (EBV) and analysed their interaction with T-cell clones specific for the same antigen. We report here that surface immunoglobulin is indeed involved in the uptake and concentration of antigen, allowing specific B cells to present antigen to T cells with very high efficiency. However, the antigen must first be internalized and processed by specific B cells and it is then presented to T cells in an MHC-restricted manner indistinguishable from that characteristic of conventional APC.     

细菌光敏色素AphA的克隆表达及重组新方法

通过PCR技术，从蓝藻PCC7120中扩增出细菌光敏色素Apha的基因aphA，进而构建aphA的缺失突变体aphA(N-25/C-445)．二者分别转人表达载体pET30a中，在宿主菌中获得高效表达，获得的脱辅基蛋白与CpcA进行体外重组．在本体外重组体系中，以藻蓝蛋白α亚基(CpeA)，在光敏色素自身作用或者藻蓝蛋白裂合酶的帮助下从CpcA上捕获胆色素完成重组．藻蓝蛋白裂合酶CpcE／F能很大程度增强光敏色素脱辅基蛋白从CocA夺取PCB的能力．该结果对于研究细菌光敏色素的色素来源及生理生化机理都具有重要意义．     

用DFT和MP2方法研究原子簇NiB2,Ni2B2,Ni3B2,Ni4B2

为了考察不同方法、不同基函数对计算结果的影响,选择了原子簇NiB2,Ni2B2,Ni3B2,Ni4B2模型,用DFT(Lanlldz,Lanl2dz)和MP2(Lanl1dz,Lanl2dz)方法对其进行高水平的量子化学计算.结果表明:DFT方法和MP2方法的定性结果一致,计算结果存在一定差别,基函数对MP2方法的结果影响较小.     

用DFT和MP2方法研究原子簇NiB2,Ni2B2,Ni3B2,Ni4B2

为了考察不同方法、不同基函数对计算结果的影响,选择了原子簇NiB2,Ni2B2,Ni3B2,Ni4B2模型,用DFT(Lanlldz,Lanl2dz)和MP2(Lanl1dz,Lanl2dz)方法对其进行高水平的量子化学计算.结果表明:DFT方法和MP2方法的定性结果一致,计算结果存在一定差别,基函数对MP2方法的结果影响较小.     

XCBL及其在B2B电子商务中的应用

介绍了由CommerceOne提出的电子商务的数据交换标准——XCBL(XML Common Business Library).文中对电子商务数据交换标准的发展及XCBL的发展、基本结构模型及其特点进行了介绍.对以XCBL为标准的电子商务数据交换的具体应用进行了探讨,提供了具体的开发模型和开发方法,对XCBL及其发展提出了自已的观点和看法.     

XCBL及其在B2B电子商务中的应用

介绍了由CommerceOne提出的电子商务的数据交换标准———XCBL(XMLCommonBusinessLibrary) .文中对电子商务数据交换标准的发展及XCBL的发展、基本结构模型及其特点进行了介绍 .对以XCBL为标准的电子商务数据交换的具体应用进行了探讨 ,提供了具体的开发模型和开发方法 ,对XCBL及其发展提出了自已的观点和看法     

具有自主复制功能的水稻高度重复序列ARS2的结构和功能分析

对一个水稻珍汕９７Ａ不育系核ＤＮＡ来源的具有自主复制功能的高度重复顺序片段ＡＲＳ２（全长４７２０ｂｐ）进行了亚克隆构建和测序,获得了它的全顺序。     

B282C电子商务模式与基于J2EE设计架构的电子商务平台

B282C电子商务模式是互联网信息时代市场新型商务交易需求与电子信息技术开发利用的产物．基于J2EE电子商务平台开发技术架构的B282C电子商务平台具有稳定运行、交互性能高、易于维护、可扩展和安全性良好的特点,可以较好地满足当前电子商务交易复杂的企业级应用需要．     

Functional interaction between human T-cell protein CD4 and the major histocompatibility complex HLA-DR antigen

Mature T cells segregate phenotypically into one of two classes: those that express the surface glycoprotein CD4, and those that express the glycoprotein CD8. The CD4 molecule is expressed primarily on helper T cells whereas CD8 is found on cytotoxic and suppressor cells. A more stringent association exists, however, between these T-cell subsets and the major histocompatibility complex (MHC) gene products recognized by their T-cell receptors (TCRs). CD8+ lymphocytes interact with targets expressing class I MHC gene products, whereas CD4+ cells interact with class II MHC-bearing targets. To explain this association, it has been proposed that these 'accessory' molecules bind to monomorphic regions of the MHC proteins on the target cell, CD4 to class II and CD8 to class I products. This binding could hold the T cell and its target together, thus improving the probability of the formation of the trimolecular antigen: MHC: TCR complex. Because the TCR on CD4+ cells binds antigen in association with class II MHC, it has been difficult to design experiments to detect the association of CD4 with a class II molecule. To address this issue, we devised a xenogeneic system in which human CD4 complementary DNA was transfected into the murine CD4-, CD8- T-cell hybridoma 3DT-52.5.8, the TCR of which recognizes the murine class I molecule H-2Dd. The murine H-2Dd-bearing target cell line, P815, was cotransfected with human class II HLA-DR alpha, beta and invariant chain cDNAs. Co-culture of the parental T-cell and P815 lines, or of one parental and one transfected line resulted in a low baseline response. In contrast, a substantial increase in response was observed when CD4+ 3DT-52.5.8 cells were co-cultured with HLA-DR+ P815 cells. This result strongly indicates that CD4:HLA-DR binding occurs in this system and that this interaction augments T-cell activation.     

B(X)上的某些连续线性泛函的表示

设又是一个Banach空间，B(x)表示x上的有界线性算子全体，定义了B(x)上某些算子拓扑，并且给出了在这些拓扑下B(X)上的连续线性泛函的表示公式．     

TiO2机能性粉末除臭实验

对制作球状光触媒TiO2材料过程中所产生的机能性粉末进行了研究,并进行了密闭空间内的香烟烟味的除臭实验。从所得臭味浓度与所经时间的曲线图看出,具有机能性粉末的除臭效果非常明显,除臭时间很短且除臭彻底。     

C2B

<正>@钱志新:新一代制造业有四大特点:一是智能制造,由软件主导的产品制造;二是互联制造,互联网重构制造业;三是定制制造,C2B成为未来的主流模式;四是绿色制造,全过程的绿色化制造。(博导,南京大学教授、高级工程师)@王高俊医药营销观察与思考:互联网让管理的重点从B2C到C2B,组织架构也会由金字塔变成网状,产品也从点到面、从市场化到社会化转变。(前亿利天然药业集团副总经理)