In vivo lifetimes of the three color-sectors in bioluminescence emissions of the firefly Luciola praeusta at different temperatures

Bioluminescence emissions from fireflies have been well-studied for over a century. From the apparent features of the emitted light, conclusions have been drawn and hypotheses put forward on the characteristics of the highly efficient light emitting system. The basic emitter oxyluciferin, being chemically unstable, is difficult to study in isolation and, therefore, its analogs have been prepared and analyzed. In this letter, the lifetimes of the excited-state emitter oxyluciferin are measured, and an inference is drawn on the chemiluminescence reaction in vivo. The light from the Indian species of firefly Luciola praeusta contains three color-sectors: green, yellow, and red, and hence three optical filters are used to study time-resolved emissions from these sectors at different temperatures. All the three color-sectors are observed to be temperature sensitive in the time domain. An exponential variation of lifetime with temperature is observed for the emissions in these three regions.     

氘代甲基萤火虫荧光素的全合成

以2-氰基-6-甲氧基苯并噻唑为原料,经脱甲基、氘甲基化,与D-半胱氨酸盐酸盐水合物反应合成了新化合物——氘代甲基萤火虫荧光素,总收率46%,对映选择性100%,其结构经1H NMR,FT-IR和MS表征。     

中华黄萤荧光素酶的性质

近年来,萤火虫荧光素酶催化的生物发光反应被广泛的应用到ATP检测、细菌数目检测、环境监测和其他生物学研究之中。通过对中华黄萤荧光素酶的性质研究,发现其分子量为6 400左右,是一种非典型的Michaelis-Menten氏酶,对底物之一的ATP动力学曲线为S型。最适反应温度为20～25℃,对温度极其敏感,当反应温度高于30℃时,该酶的活性快速失活。该荧光素酶的最适pH=6.5。随着pH值的下降该荧光素酶生物发光的最大发射光波长没有明显的红移现象。Mg²⁺和Mn²⁺对该酶活性的激活效果比较接近,最佳的激活浓度均在1mmol/L附近,而Ca²⁺最佳的激活浓度则小于1 mmol/L,且激活的效果只有Mg²⁺作用效果的50%左右。和Hg²⁺、Cd²⁺等离子一样,Cu²⁺会在一定程度上抑制该荧光素酶的活性。该酶的稳定性较差,对盐浓度和光照比较敏感,高浓度的盐类和长时间的日光照射能够使酶失活。谷胱甘肽(GSH)和二硫苏糖醇(DTT)是该酶较好的保护剂,可以提高该酶在一定时间内的稳定性,其中前者的作用效果要好于后者。     

面向不确定需求租户集的云服务智能匹配模型

为了解决云计算环境下由海量租户集和资源集间的不确定性因素引起的高质量云服务获取困难的问题,提出了一种描述动态异构租户集不确定性需求的方法.在此基础上,构建属性权重完全未知情况下的云服务智能匹配模型,排除了租户提交权值造成的偏差.神经网络以属性区间计算的相离度作为输入,服务满意度为输出来动态模拟租户集的不确定需求,运用萤火虫算法求解模型获取最优服务组合.最后,实例验证了神经网络的可靠性以及算法的有效性.实验结果表明,模型能有效获取高质量的云服务组合,优于传统的匹配方法.     

Back electron transfer in electron-exchange chemiluminescence of oxyaryl-substituted spiroadamantyl dioxetane, an analog of firefly bioluminescence

The viscosity dependence of the excitation yield of the singlet oxybenzoate anion, an emitter of electron-exchange chemiluminescence of oxyaryl-substituted spiroadamantyl dioxetane, a chemical analog of firefly bioluminescence, was studied. At 299, K the excitation yield increases from 8 to 23% as the content of diphenylmethane in its mixture with benzene increases to 97%. This effect was quantitatively interpreted in terms of a probabilistic model of the solvent-cage effect, assuming that the chemiexcitation results from the back electron transfer between the products of chemically initiated decomposition of the starting reagent. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 4, pp. 655–661, April, 2000.     

A QM/MM Study on the Initiation Reaction of Firefly Bioluminescence—Enzymatic Oxidation of Luciferin

Among all bioluminescent organisms, the firefly is the most famous, with a high luminescent efficiency of 41%, which is widely used in the fields of biotechnology, biomedicine and so on. The entire bioluminescence (BL) process involves a series of complicated in-vivo chemical reactions. The BL is initiated by the enzymatic oxidation of luciferin (LH₂). However, the mechanism of the efficient spin-forbidden oxygenation is far from being totally understood. Via MD simulation and QM/MM calculations, this article describes the complete process of oxygenation in real protein. The oxygenation of luciferin is initiated by a single electron transfer from the trivalent anionic LH₂ (L³⁻) to O₂ to form ¹[L^•2−…O₂^•−]; the entire reaction is carried out along the ground-state potential energy surface to produce the dioxetanone (FDO⁻) via three transition states and two intermediates. The low energy barriers of the oxygenation reaction and biradical annihilation involved in the reaction explain this spin-forbidden reaction with high efficiency. This study is helpful for understanding the BL initiation of fireflies and the other oxygen-dependent bioluminescent organisms.     

Blind and Secured Adaptive Digital Image Watermarking Approach for High Imperceptibility and Robustness

In the past decade, rapid development in digital communication has led to prevalent use of digital images. More importantly, confidentiality issues have also come up recently due to the increase in digital image transmission across the Internet. Therefore, it is necessary to provide high imperceptibility and security to digitally transmitted images. In this paper, a novel blind digital image watermarking scheme is introduced tackling secured transmission of digital images, which provides a higher quality regarding both imperceptibility and robustness parameters. A block based hybrid IWT- SVD transform is implemented for robust transmission of digital images. To ensure high watermark security, the watermark is encrypted using a Pseudo random key which is generated adaptively from cover and watermark images. An encrypted watermark is embedded in randomly selected low entropy blocks to increase the security as well as imperceptibility. Embedding positions within the block are identified adaptively using a Blum–Blum–Shub Pseudo random generator. To ensure higher visual quality, Initial Scaling Factor (ISF) is chosen adaptively from a cover image using image range characteristics. ISF can be optimized using Nature Inspired Optimization (NIO) techniques for higher imperceptibility and robustness. Specifically, the ISF parameter is optimized by using three well-known and novel NIO-based algorithms such as Genetic Algorithms (GA), Artificial Bee Colony (ABC), and Firefly Optimization algorithm. Experiments were conducted for the proposed scheme in terms of imperceptibility, robustness, security, embedding rate, and computational time. Experimental results support higher effectiveness of the proposed scheme. Furthermore, performance comparison has been done with some of the existing state-of-the-art schemes which substantiates the improved performance of the proposed scheme.     

激光供能无人机的一种优化跟踪算法

航天事业的发展以及新能源技术的开发,使得小型电动无人机在现代战争、科学研究等方面具有较高的应用价值。激光无线能量传输技术能有效解决小型电动无人机续航时间短的问题,极大提高了无人机的工作能效。以无人机激光供能系统结构原理为基础,针对小型电动无人机激光无线供能的特点,提出了一种最大功率点优化跟踪方法:即采用恒定电压法（CV法）和萤火虫算法（FA法）相结合的优化控制算法,在激光投射到无人机上的光伏电池板上后,通过对无人机激光无线充电过程中最大功率点的跟踪,提高激光利用率及充电稳定性。并且通过数值仿真,验证了所提算法的准确性和适用性。     

Oligo(ethylene imine)-grafted glycidyl methacrylate linear and star homopolymers: Odd–even correlated transfection efficiency

The present study aims to investigate an odd–even effect of the number of ethylene imine units in the side-groups of totally abiotic synthetic polymers on their efficiency in DNA transfection. A library of fifteen polymers was fabricated. Two star homopolymers and one linear homopolymer based on glycidyl methacrylate were synthesized and used as precursors to which five linear oligo(ethylene imine)s (OEI) were grafted. The number of ethylene imine groups of the OEIs was varied. Specifically, ethylene diamine, diethylene triamine, triethylene tetramine, tetraethylene pentamine, and pentaethylene hexamine were used. Each of these fifteen OEI-grafted polymers was evaluated in terms of their efficiency to transfer plasmid DNA encoding firefly luciferase in C2C12 mouse myoblast cells. The transfection efficiency displayed an odd-even pattern, with all OEI-grafted polymers with an odd number of ethylene imine repeating units exhibiting higher transfection efficiency compared with those possessing an even number of ethylene imine repeating units. The odd–even effect was more pronounced for the star polymers with longer arms (degree of polymerization, DP = 100), while in case of the linear polymers, the odd–even effect was only observed for the lowest polymer loading. The cytotoxicity of the OEI-grafted polymers also followed an odd–even pattern, with the OEI-grafted star polymers with an arm DP of 100 and the linear polymers clearly presenting an odd-even effect, while the cytotoxicity of the OEI-grafted star polymers with an arm DP of 20 slightly increased with the number of ethylene imine repeating units.