紫细菌光合反应中心电子激发态的理论研究

运用ZINDO和INDO/S两种量子化学理论方法, 对紫细菌(Rhodopseudomonas (Rps.) viridis) 光合反应中心色素分子簇的电子激发态进行了理论研究. 通过理论计算的电子激发态光谱与实验吸收光谱, Circular Dichroism光谱的比较, 对实验光谱重新进行了较为合理的归属. 考察了色素分子间相互作用、色素分子与蛋白质中氨基酸残基相互作用对激发态光谱的影响. 研究结果表明: Rps. viridis光合反应中心色素分子簇间的相互作用以及氨基酸残基与色素分子的作用, 对激发态光谱的性质具有一定的影响; 不考虑色素分子间相互作用以及色素分子与周围氨基酸残基的作用, 只基于单个色素分子(或其模型分子)理论计算进行光谱归属是不合理的.     

藻类光合天线系统的微观结构与整体功能

藻类天线系统广谱捕光、快速高效传能的特点使其成为自然界最理想的光合捕光系统．藻类天线系统内多种孤立色素蛋白聚集高分辨晶体结构测定使研究实现了微观水平,然而,藻类天线系统是多种藻胆蛋白和连接多肽有机组成的完整功能体,为建立局部微观结构和整体功能的联系,包括连接多肽在内的复合物研究将是突破点之一．藻类天线色素蛋白聚集体的脱辅基蛋白和连接多肽通过弱相互作用对色团光谱性质调制,实现了藻类天线系统由周边向核心“漏斗”式高效捕光和传能系统,因此,研究聚集体弱相互作用组装、脱辅基蛋白对色四光谱的微观调制是具有普遍意义的问题;同时对人工光能转换系统金色天线的设计和组装具有指导意义．无论是光合生物还是人工光能转换系统,天线系统和反应中心空间及能量优化匹配是实现高效光能利用的关键．生命系统在实现特定生物学功能时伴随的结构运动是普遍现象,这一现象的分子水平观察成为当前前沿性研究问题．藻类天线系统在类囊体膜上的运动性是近期观察到的事实,动态变化的机理、形态、驱动力、传能途径和方向以及生物学意义是有待深入探索的问题．     

从细胞色素c的还原检定融合膜电子递体的衔接

本文检定了呼吸电子递体细胞色素c(cyt.c)在残缺类囊体膜、嵴膜和其组合膜系中的氧化还原状态。结果:在光合电子传递条件下,残缺膜和嵴膜的组合膜系对cyt.c产生了很高的光下还原效应,而完整叶绿体和线粒体之混合系的效应则甚低。在分别用光合及呼吸电子传递抑制剂处理后以及进一步在两种抑制剂的共同作用后,融合膜系仍有较高的光下还原cyt.c的能力。结果表明:两种能量转换膜重组后形成了融合膜,膜双方的电子递体彼此衔接,且衔接的方式是多途径的。     

光合放氧复合物结构及其放氧机理的研究

光合水氧化是地球上最重要的生化过程之一.光合放氧生物包括光系统Ⅰ(PSⅠ)和光系统Ⅱ(PSⅡ)两种类型反应中心,光系统Ⅱ反应中心能以水作为电子给体,利用光能氧化水产生质子和氧气.对于水如何被氧化这个难题前人已做了大量的工作,但到目前为止放氧复合物(OEC)的结构及水氧化的机理仍不清楚.本文结合当前研究结果,就光合放氧复合物的结构及光合放氧机理进行了综述,希望能有助于推进这方面的工作.     

光合放氧复合物锰簇光组装*

在光系统II水氧化过程中, 由锰簇及其附近一个具氧化还原活性的酪氨酸Y_Z组成的光合放氧复合物通过4个连续的氧化还原反应将水裂解为质子和氧气。在光系统II的功能性组装过程中,光合放氧复合物锰簇是通过一个被称作光组装的过程形成的。结合当前的研究进展,本文详尽地介绍了光合放氧复合物锰簇光组装的动力学模型、与锰簇形成相关的蛋白及锰簇的外围配体、锰与去锰光系统II的结合特性、其它辅助因子对锰簇光组装的影响及锰簇光组装的机理。此外,结合我们的研究结果,对人工合成的锰化合物与去锰光系统II放氧复合物的光组装进行了综述和讨论。本文最后介绍了目前光合放氧复合物锰簇结构及功能研究中存在的一些问题,并对光合放氧复合物锰簇结构及功能研究的应用前景进行了展望。     

重稀土矿区芒萁稀土元素精细定位及光抑制对其光合活性的影响

分析了中国江西省龙南县足洞乡重稀土矿区及非矿区稀土元素富集植物芒萁体内稀土元素的精细定位及光抑制对芒萁光合特性影响。结果表明,稀土元素主要分布在芒萁的根部和叶片中,矿区芒萁叶片中的重稀土含量显著高于非矿区芒萁叶片。电镜观察表明,稀土元素主要分布在细胞壁外,细胞质中只含有微量稀土元素。与非矿区芒萁叶片相比,重稀土矿区芒萁叶片中的色素含量显著降低,但β-胡萝卜素含量显著增高。正常光照条件下,矿区芒萁光系统II(PS II)的光化学特性比非矿区芒萁略有提高。光抑制实验表明,400μmol photons.m-2.s-2的光照强度对矿区芒萁光化学活性影响很小而非矿区芒萁光化学活性显著下降。综上所述,矿区芒萁富集重稀土元素的机制是:(1)通过产生的稀土结合多糖、蛋白等物质将稀土元素固定在细胞壁外;(2)通过改变叶片内部的叶黄素循环色素含量避免高光强对光系统的伤害作用。     

细胞色素c氧化酶研究新进展

综述了细胞色素c氧化酶研究的新进展,重点评述了细胞色素c氧化酶晶体结构和各种谱学研究结果,质子传递途径、O2还原的催化机理以及与其相耦联的质子泵机理等方面的最新进展。     

光控纳米载体在药物释放中的应用

光敏感的纳米载体因其可从时间和空间上精确地控制药物的释放以实现对肿瘤的高效治疗,近年来逐渐成为生物医学领域的研究热点之一。本文综述了光敏感的纳米载体破裂从而释放出装载的药物的三种机理,主要包括：（1）光致异构化引发的纳米载体形态转变;（2）光反应引发的纳米载体降解;（3）光热引发的纳米载体破裂。本文简单介绍了这三种释放机理,例举了这三种释放机理所对应的光敏感材料,并阐述了其在药物运输、可控释放以及肿瘤治疗中的最新研究进展以及存在的问题,为光敏感纳米载体在生物体系中的应用提供参考,并对今后的发展作了展望。     

细胞色素c与Fe(EDTA)~(2-)类络合物的氧化还原反应的快速动力学研究

采用截流法对细胞色素c与一系列Fe(EDTA)~(2-)类络合物间的氧化还原反应进行了研究。在拟一级条件下,测定了络合物浓度、反应温度、离子强度等条件对反应速率的影响。结果表明,氧化态细胞色素c(Cytc(Ⅲ))与Fe(EDTA)~(2-),Fe(CDTA)~(2-)和Fe(IDA)~(2-)间的反应符合典型的“外轨型”机理。而细胞色素c-Fe(NTA)~-体系则表现出不同的行为,具有速率饱和现象、较负的活化熵△S~≠(以及较低的细胞色素c的总电荷值和结合部位电荷计算值。基于这些结果,提出了“半内轨型”反应动力学模式。     

丙烯酸酯类单体在空气中紫外固化的研究

辐射可固化涂层在空气中进行紫外光照射，其固化速率随光引发剂组份的增加开始近似线性增大，到某一点后出现突跃．通过对氧气存在下的聚合机理的研究，认为上述现象与氧气引起的自由基终止以及固化过程中的氧气消耗速率有关．根据文中推导的关系式作出的示意图与实验数据基本吻合．     

Photoinitiators for UV and visible curing of coatings: Mechanisms and properties

The radiation curing industry is one of the most rapidly developing fields in the entire coatings industry. The low toxicity, cheapness, speed, control and ease of formulation and operation are some of the main advantages of this growing technology. UV and/or visible light radiation is used to induce photochemical polymerization or crosslinking of a monomer, oligomer or prepolymer formulation containing a certain type of unsaturation, such as an acrylic group, and an appropriate initiator. The latter is used to absorb the light energy and transform it into active species, such as radicals or ions, capable of inducing such reactions. Applications extend to general coatings for paper, board, wood, tapes, compact discs and holograms, inks, photoresists for imaging processes and adhesives for welding and sealing in electronic circuit boards. The photoinitiator is the key to the control of these processes and, in recent years, has seen many new developments. These include the need for water-soluble, co-reactive and polymeric structures with low migration rates, as well as cheaper UV/ visible sensitizers with enhanced speed. New and effective cationic systems are also on the scene and, although expensive, are attracting significant academic and commercial interest.     

REPAIR OF 313-NM INDUCED LESIONS AND PHOTOPROTECTION IN YEAST CANDIDA GUILLIERMONDII

Abstract. The present communication is concerned with the effects of near-UV radiation (300–380 nm) on yeast Candida guilliermondii. It was found that certain doses of 313 nm irradiation caused inactivation of the yeast which was exhibited in a way different from the lethal action of far-UV radiation. It was also found that the cells inactivated by 313 nm are capable of recovering vitality, if incubated for some time in a non-nutrient medium. The yeast inactivated by far-UV radiation also proved to be capable of recovering, though to a lesser degree. Both 334 nm radiation and non-lethal doses at 313 nm induced the photoprotective effect against far-UV damage. The effect was exhibited if there was a certain time interval (2–4 h) between the exposures to photoprotective light and subsequent far-UV radiation. Within this time interval the extent of photoprotection was dependent on temperature.     

The damage repair role of He-Ne laser on plants exposed to different intensities of ultraviolet-B radiation

Light-grown broad bean (Vicia faba L.) seedlings were subjected to different intensities of UV-B radiation (0, 0.05, 0.15, 0.45, 0.90, 1.45 and 1.98 W m(-2)) for 7 h under photosynthetically active radiation (70 micromol m(-2) s(-1)) and then exposed to He-Ne laser (632.8 nm, 5.43 mW mm(-2)) radiation for 5 min or red light radiation for 4 h without ambient light radiation. When He-Ne laser radiated leaves were treated using lower intensity UV-B, the activities of superoxide dismutase (EC 1.15.1.1), ascorbate peroxidase (EC 1.11.1.11) and catalase (EC 1.11.1.6) improved significantly. Moreover, the UV-B-injured plants treated with laser light recovered faster from UV-B treatment because the concentration of malondialdehyde and the rate of electrolyte leakage from leaf disks reached control levels (no UV-B or laser treatment) early compared with those exposed only to ambient light or in dark conditions. Laser treatment, however, had no repair effect on seedling damage induced by higher UV-B radiation (1.45 and 1.98 W m(-2)), even with higher laser flux rates and longer laser treatment. In addition, the red light treatment had no repair effect on UV-B-induced damage. Meanwhile, the long-term physiological effect of He-Ne laser treatment on UV-B damaged plants was presented and evaluated. The results showed that the laser had a long-term positive physiological effect on the growth of UV-B-damaged plants. With the exception of the severe damage caused by higher UV-B radiation, a laser with the proper flux rate and treatment time can repair UV-B-induced damage and shorten the recovery time.     

Oxygen Inhibition and Coating Thickness Effects on Uv Radiation Curing of Weatherfast Clearcoats Studied by Photo-DSC

Radiation curing is an environmentally-friendly technology. Furthermore, radiation curing is a faster, energy saving and more efficient industrial process than the heat-curable process. One of the most important requirements for the widespread application of UV curable coatings in the coating industry is that they are stable vs. atmospheric degradation. Today's state of the art in oxidative drying and thermosetting coatings is the use of light stabilizers to protect polymers vs. the damage of outdoor exposure. Oxygen has a detrimental effect on the cure response of free radical systems, especially in thin-film coatings. Differential photocalorimetry (photo-DSC) was used to investigate the oxygen effect and the use of light stabilizers on UV curing of photocurable formulations based on acrylate materials. Coating thickness influence was also considered. This revised version was published online in August 2006 with corrections to the Cover Date.     

Photoreactivation in Paramecium tetraurelia under conditions of various degrees of ozone layer depletion

Photoreactivation (PR) is an efficient survival mechanism that helps protect cells against the harmful effects of solar-ultraviolet (UV) radiation. The PR mechanism involves photolyase, just one enzyme, and can repair DNA damage, such as cyclobutane-pyrimidine dimers (CPD) induced by near-UV/blue light, a component of sunlight. Although the balance of near-UV/blue light and far-UV light reaching the Earth's surface could be altered by the atmospheric ozone layer's depletion, experiments simulating this environmental change and its possible effects on life have not yet been performed. To quantify the strength of UVB in sunlight reaching the Earth's surface, we measured the number of CPD generated in plasmid DNA after UVB irradiation or exposure to sunlight. To simulate the increase of solar-UV radiation resulting from the ozone layer depletion, Paramecium tetraurelia was exposed to UVB and/or sunlight in clear summer weather. PR recovery after exposure to sunlight was complete at a low dose rate of 0.2 J/m2 x s, but was less efficient when the dose rate was increased by a factor of 2.5 to 0.5 J/m2 x s. It is suggested that solar-UV radiation would not influence the cell growth of P. tetraurelia for the reason of high PR activity even when the ozone concentration was decreased 30% from the present levels.     

Beyond Xeroderma Pigmentosum: DNA Damage and Repair in an Ecological Context. A Tribute to James E. Cleaver

The ability to repair DNA is a ubiquitous characteristic of life on Earth and all organisms possess similar mechanisms for dealing with DNA damage, an indication of a very early evolutionary origin for repair processes. James E. Cleaver's career (initiated in the early 1960s) has been devoted to the study of mammalian ultraviolet radiation (UVR) photobiology, specifically the molecular genetics of xeroderma pigmentosum and other human diseases caused by defects in DNA damage recognition and repair. This work by Jim and others has influenced the study of DNA damage and repair in a variety of taxa. Today, the field of DNA repair is enhancing our understanding of not only how to treat and prevent human disease, but is providing insights on the evolutionary history of life on Earth and how natural populations are coping with UVR‐induced DNA damage from anthropogenic changes in the environment such as ozone depletion.     

Autophagy in UV Damage Response

UV radiation exposure from sunlight and artificial tanning beds is the major risk factor for the development of skin cancer and skin photoaging. UV‐induced skin damage can trigger a cascade of DNA damage response signaling pathways, including cell cycle arrest, DNA repair and, if damage is irreparable, apoptosis. Compensatory proliferation replaces the apoptotic cells to maintain skin barrier integrity. Disruption of these processes can be exploited to promote carcinogenesis by allowing the survival and proliferation of damaged cells. UV radiation also induces autophagy, a catabolic process that clears unwanted or damaged proteins, lipids and organelles. The mechanisms by which autophagy is activated following UV exposure, and the functions of autophagy in UV response, are only now being clarified. Here, we summarize the current understanding of the mechanisms governing autophagy regulation by UV, the roles of autophagy in regulating cellular response to UV‐induced photodamage and the implications of autophagy modulation in the treatment and prevention of photoaging and skin cancer.     

The role of multifunctional acrylates in radiation grafting and curing reactions

Multifunctional acrylates (MFAs) are used extensively in radiation rapid cure (RRC) formulations involving u.v. and EB processing to achieve fast rates of polymerization and cross-linking if required. For certain RRC applications, the ability to achieve concurrent grafting with cure can lead to improved properties of the finished product. In the current work the effect of MFAs on concurrent grafting during the curing process is evaluated from a basic study of the role of these MFAs on a typical grafting reaction initiated by u.v. or ionizing radiation. The model used for the grafting work was the copolymerization of styren to the polyolefins and cellulose. It is found that the presence of the MFA and related polyfunctional monomers (PFMs) in additive amounts in the styrene grafting solution enhances the copolymerization yield under certain radiation conditions. Synergistic effects of the MFAs and PFMs with other additives such as mineral acids, inorganic salts (e.g. lithium perchlorate) and specific organic compounds (e.g. urea) were observed in the model grafting reactions. When additives such as silanes and fluorinated alkyl esters, which are important in RRC formulations to achieve slip and flow in the cured film, are incorporated into the model grafting monomer solution, the former additive retards copolymerization whereas the latter enhances it. The inclusion of MFAs in these monomer solutions leads to large increases in graft with both silanes and fluorinated alkyl esters. The result implies that MFAs, in addition to speeding cure and cross-linking in RRC processes, may also enhance adhesion to certain substrates because of an increase in concurent grafting during cure. A mechanism for these additive effects in concurrent grafting and curing is proposed.     

电子束固化环氧树脂的物理特征及其分析

分析了环氧树脂电子束辐射固化的物理特征 ,电子束辐射固化过程受活性中心扩散控制 ,整个固化区域由片层状结构组成 .与电子能量沉积分布相对应 ,环氧树脂辐射固化度的最高值是在一定深度而不是在辐射表面出现 .对电子束辐射环氧树脂体系的固化过程进行了模型解释 ,固化区域大小主要由电子的能量传递范围和浓度决定 ,反应活性中心的扩散作用影响较弱     

New Developments in Photoinitiators

New developments of photoinitiators are the base for the further extension of the radiation curing technology. Three different approaches are presented: The optimized combination of a bisacylphosphine oxide photoinitiator with a suitable stabilizer package allows the UV curing of clear coatings with an excellent performance in outdoor use. The design of new oxime ester derivatives allowed the introduction of a new tailor-made photoinitiator for color filter resists applications that considerably improves the color quality of the color filter. A novel photoinitiator class capable of releasing strong amine bases opens new opportunities for expanding radiation curing into resins types that crosslink by base-catalyzed processes.