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11.
Chen H Li G Zhang FF Sun L Chen HL Zhang SY 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2003,59(12):2767-2774
Time resolved photoacoustic calorimetry (PAC) was applied to a study of the photolysis of a coenzyme B(12) analog 2',5'-dideoxyadenosylcobalamin, which lacks an -OH group at the 2' position of ribofuranose ring. In aqueous solution, we report for the first time the quantum yield Phi(d) (0.25+/-0.02), Co-C bond dissociation energy (BDE; 31.8+/-2.5 kcal mol(-1)) and reaction volume change deltaV(R) (6.5+/-0.5 ml mol(-1)) due to conformation changes of the corrin ring and its side chains accompanying the cleavage of the Co-C bond. These values for the analog are very similar to those for the natural cofactor. Based our results and previous studies, a possible explanation for the similarity in their structure and properties versus the large difference in their enzymatic activity is discussed. 相似文献
12.
通过仿真计算分析了激光在光束控制系统通道内传输所产生的热效应及其对远场光束质量的影响。激光传播由近轴波方程描述,用快速傅里叶变换技术求解;激光热效应引起的流场密度变化采用完全Navier-Stokes方程计算。计算给出了不同波长、不同吸收系数条件下的远场光斑情况。计算结果表明,在典型的工作条件和状态下,较高能量激光在光束控制系统通道内产生的热效应影响不容忽视,它会明显降低远场目标处的能量集中度,增大光斑的发散。 相似文献
13.
Mingfei Ji Zongtao Chai Jie Chen Gang Li Qiang Li Miao Li Yelei Ding Shaoyong Lu Guanqun Ju Jianquan Hou 《Molecules (Basel, Switzerland)》2022,27(13)
Small ubiquitin-related modifier (SUMO)-specific protease 1 (SENP1) is a cysteine protease that catalyzes the cleavage of the C-terminus of SUMO1 for the processing of SUMO precursors and deSUMOylation of target proteins. SENP1 is considered to be a promising target for the treatment of hepatocellular carcinoma (HCC) and prostate cancer. SENP1 Gln597 is located at the unstructured loop connecting the helices α4 to α5. The Q597A mutation of SENP1 allosterically disrupts the hydrolytic reaction of SUMO1 through an unknown mechanism. Here, extensive multiple replicates of microsecond molecular dynamics (MD) simulations, coupled with principal component analysis, dynamic cross-correlation analysis, community network analysis, and binding free energy calculations, were performed to elucidate the detailed mechanism. Our MD simulations showed that the Q597A mutation induced marked dynamic conformational changes in SENP1, especially in the unstructured loop connecting the helices α4 to α5 which the mutation site occupies. Moreover, the Q597A mutation caused conformational changes to catalytic Cys603 and His533 at the active site, which might impair the catalytic activity of SENP1 in processing SUMO1. Moreover, binding free energy calculations revealed that the Q597A mutation had a minor effect on the binding affinity of SUMO1 to SENP1. Together, these results may broaden our understanding of the allosteric modulation of the SENP1−SUMO1 complex. 相似文献
14.
利用光栅最小偏向角法测光波波长 总被引:1,自引:0,他引:1
本文导出斜入射时,光栅谱线存在最小偏向角的条件及最小偏向角与波长间的关系,据此精确测定了光波波长,并在实验中通过与垂直入射法的比较显出其优越性。 相似文献
15.
Yanlin Feng Jiali Lin Gang He Li Liang Qijun Liu Jun Yan Qian Yao 《Molecules (Basel, Switzerland)》2022,27(15)
Pomegranate peel extract (PPE), which is abundant in polyphenols, holds immerse prospects for the treatment of airway infection. In this study, water and ethanol of 30%, 50%, and 80% were used to prepare PPE. A total of 18 phenols belonging to 8 categories of polyphenols were identified in PPE by HPLC-MS/MS. The PPE from the four extraction solvents possessed different antioxidant, antibacterial, and anti-inflammatory activities. Principal component analysis revealed that though total flavonoids (TFs), total polyphenols (TPs), and total tannins (TTs) were responsible for the reducing power of PPE, only TFs contributed to the effect of PPE in inhibiting lipid membrane peroxidation. TPs, TTs, and punicalagin were positively correlated with the antibacterial strength against S. aureus while TTs alone contributed to the inhibition of methicillin-resistant S. aureus, implying the crucial role of TT in suppressing bacteria. Meanwhile, TTs was associated with the prevention of IL-6 release. The PPE with higher contents of TPs, TTs, and punicalagin had a weaker capacity to decrease nitric oxide secretion. PPE of 30% ethanol gained the highest integrated score due to its stronger antioxidant, antibacterial, and anti-inflammatory activities. It is a suitable candidate for the therapy of respiratory tract infection. 相似文献
16.
对微结构的制作、微装配系统进行了研究. 采用飞秒激光双光子聚合微加工技术制作有底座、精细的三维立体“拱形”微结构, 其高250μm、长300μm、厚50μm. 将此微结构与实验室自主搭建的二维微装配平台相结合, 利用自主编程的人机交互界面驱动步进电机, 远程操控微装配设备; 将荧光闪烁陶瓷粉末装配到微结构中, 对装配后的微结构进行荧光光谱表征发现, 纯荧光粉末和微结构中的荧光粉末的发射光谱在测量误差范围内基本一致, 表明荧光粉末的光学性质未发生改变. 利用该装置可以将各类微纳米级材料和微结构进行装配, 形成含有不同材料的微结构系统. 相似文献
17.
Analytical performance study of solar blind non-line-of-sight ultraviolet short-range communication links 总被引:5,自引:0,他引:5
Motivated by recent advances in solid-state incoherent ultraviolet sources and solar blind detectors, we study communication link performance over a range of less than 1 km with a bit error rate (BER) below 10(-3) in solar blind non-line-of-sight situation. The widely adopted yet complex single scattering channel model is significantly simplified by means of a closed-form expression for tractable analysis. Path loss is given as a function of transceiver geometry as well as atmospheric scattering and attenuation and is compared with experimental data for model validation. The BER performance of a shot-noise-limited receiver under this channel model is demonstrated. 相似文献
18.
为了解决运动参数光电探测过程中的相机标定问题,制作一种两端及中间各安装一个红外反光标记球的一维标定物.不需要其它复杂标定装置,只要将这种特制的一维标定物在测量空间内多次随意移动并摄取其图像,即可实现标定.算法首先假定主点位于像面中心附近的某个位置,再求出焦距、旋转矩阵、平移向量和比例因子,最后通过评价函数将相机标定转换成寻找两相机最佳主点对的非线性最小化问题.在传统进化策略中引进个体的自我改进系数、个体间距离等概念,提出了求取子代个体间的欧式距离并排序的方法,设计了搜索最佳主点对的改进型进化策略算法.与传统标定方法相比,基于一维标定物的方法克服了多相机场合的遮挡问题,改进进化策略的引入打破了一维标定物需做某种特殊运动的限制,使一维标定物自由运动时相机内、外参数的同时求解成为可能,改进的模拟退火进化策略改善了算法的全局收敛性能并加快了收敛速度. 相似文献
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