Fluorescence‐Labeled Bis‐benzamidines as Fluorogenic DNA Minor‐Groove Binders: Photophysics and Binding Dynamics

In recent decades there has been great interest in the design of highly sensitive sequence‐specific DNA binders. The eligibility of the binder depends on the magnitude of the fluorescence increase upon binding, related to its photophysics, and on its affinity and specificity, which is, in turn, determined by the dynamics of the binding process. Therefore, progress in the design of DNA binders requires both thorough photophysical studies and precise determination of the association and dissociation rate constants involved. We have studied two bis‐benzamidine (BBA) derivatives labeled by linkers of various lengths with the dye Oregon Green (OG). These fluorogenic binders show a dramatic fluorescence enhancement upon binding to the minor groove of double‐stranded (ds) DNA, as well as significant improvement in their sequence specificity versus the parent BBA, although with decreased affinity constants. Detailed photophysical analysis shows that static and dynamic quenching of the OG fluorescence by BBA through photoinduced electron transfer is suppressed upon insertion of BBA into the minor groove of DNA. Fluorescence correlation spectroscopy yields precise dynamic rate constants that prove that the association process of these fluorogenic binders to dsDNA is very similar to that of BBA alone and that their lower affinity is mainly a consequence of their weaker attachment to the minor groove and the resultant faster dissociation process. The conclusions of this study will allow us to go one step further in the design of new DNA binders with tunable fluorescence and binding properties.     

Natural aging of shape stabilized phase change materials based on paraffin wax

Natural aging of shape-stabilized phase change materials containing linear low density polyethylene (LLDPE), paraffin wax and expanded graphite (EG) in Qatari climate has been studied. It was found that expanded graphite significantly improved the performance of prepared SSPCMs in multiple ways. Firstly, EG suppressed leakage of paraffin wax from the compact shape of SSPCMs. The addition of 15 wt% of EG to shape stabilized phase change materials (SSPCMs) containing 50 wt% of wax caused a decreasing in the leakage of wax by 50% over 210 days of natural aging.Secondly, ∖expanded graphite enhanced the photochemical stability of the blends; this was confirmed by FTIR analysis, where carbonyl index decreased with EG content.     

石蜡相光度法测定混合稀土中的铈

系统研究了Ｃｅ（Ⅳ）－８－羟基喹啉体系在石蜡相中的显色反应。在ＮＨ４Ｃｌ－ＮＨ３（ｐＨ＝９．５）介质中,Ｃｅ（Ⅳ）－８－羟基喹啉有色络合物可定量被石蜡萃取,且固相色阶明显,铈量在０～１００ｕｇ／５０ｍＬ范围内符合比耳定律,从而建立了测量铈的新的固相分光光度法。其它稀土离子的干扰可通过双波长光度法测量扣除。方法应用于混合稀土合成样中铈的测定,结果满意。     

活性氧化铝吸附法测定蜂蜡中碳氢化合物含量

本文阐述了用活性氧化铝做吸附剂,成功地选择了各种条件来提取组成复杂的天然产物－蜡中的碳氢化合物,从而同碳氢化合物含量。用石蜡进行验证实验,准确度可达９９．５％以上。     

提高大功率快速熔断器熔断后高温绝缘能力的物理机制

研究石英砂及粘合剂高温电阻特性 ,指出减少粘合剂中离子浓度 ,是提高保险片熔断后高温绝缘性能的关键 ,并通过试验加以验证 .     

端羟基聚丁二烯/增塑剂共混物相容性的分子动力学模拟和介观模拟

应用分子动力学(MD)和介观动力学(MesoDyn)模拟方法对固体推进剂中端羟基聚丁二烯(HTPB)与增塑剂癸二酸二辛酯(DOS)、硝化甘油(NG)的相容性进行了研究. 采用MD模拟方法在COMPASS力场下, 对纯物质、HTPB/增塑剂共混物的密度、内聚能密度、溶度参数和共混物分子间的Flory-Huggins作用参数及结合能等进行了模拟计算, 通过比较溶度参数差值(Δδ)的大小、模拟前后体系密度变化情况均可以预测HTPB与增塑剂的相容性, 结合能的分析揭示了HTPB/增塑剂共混物组分间的相互作用及本质. 将Flory-Huggins作用参数转化为MesoDyn模拟的输入参数, 采用MesoDyn模拟方法对HTPB/增塑剂共混体系的介观形貌与动力学演变过程进行了研究, 通过模拟得到的等密度图、自由能密度和有序度参数等可以判断共混体系的相容性. MD和MesoDyn模拟结果均表明: HTPB/DOS属于相容体系, 而HTPB/NG属于不相容体系, 其结论与实验结果一致.     

用石蜡作碳源在高温高压下合成金刚石

用石蜡作炭源，从原子分子转化的角度，选择适当的氧化剂、触媒和组装方式，在高温高压下合成出了０．３ｍｍ大小的金刚石。     

Thermal stability of binder for mineral wool insulations

The boundary of the ‘analytical’ thermal stability of a phenol-formaldehyde-urea binder was determined, assuming the lack of nitrogen losses as a criterion of thermal stability.