高灵敏比色检测Cu~(2+)的反蛋白石结构光子晶体水凝胶膜

以丙烯酰胺(AM)和N-乙烯基咪唑(NVI)为双功能单体,借助"三明治"结构有效控制前驱液的填充,制备了可特异性识别Cu~(2+)的反蛋白石结构光子晶体水凝胶膜(PCHs).该PCHs具有相互贯通的三维有序大孔结构,可在Cu~(2+)缓冲溶液中快速响应,产生特征的布拉格(Bragg)衍射峰.随着Cu~(2+)浓度的增大(0~10-4mol/L),PCHs的Bragg衍射峰位移66 nm,并伴随着明显的颜色变化(由棕红色逐渐变为黄绿色).此外,PCHs在混合金属盐溶液中仍能实现对Cu~(2+)的特异性识别.PCHs对Cu~(2+)的特异识别性、快速响应及自表达的特点为Cu~(2+)现场快速检测提供了可能.     

氧化石墨烯/三角形金纳米片/Nafion复合膜修饰电极对L-色氨酸的灵敏检测

采用晶种生长法制备了形状均一、导电性良好的三角形金纳米片(Au TNPs),并以氧化石墨烯(GO)为载体,聚阴离子Nafion为保护剂,将其修饰在玻碳电极(GCE)表面,制得氧化石墨烯/三角形金纳米片/Nafion复合膜修饰电极(GO/Au TNPs/Nafion/GCE).利用扫描电子显微镜和原子力显微镜对纳米复合材料的形貌进行表征,采用循环伏安法(CV)和示差脉冲伏安法(DPV)探讨了L-色氨酸(L-Trp)在不同修饰电极上的电化学行为.结果表明,GO/Au TNPs/Nafion/GCE对L-Trp表现出良好的电催化氧化特性.在0.10 mol/L的PBS缓冲溶液(p H=3.5)中,该修饰电极的响应峰电流与L-Trp的浓度存在良好的线性关系,线性范围为4.000×10~(-8)~6.000×10~(-5)mol/L,检出限为1.000×10~(-8)mol/L(S/N=3).该电极具有良好的重现性、稳定性和抗干扰能力.将该电极用于猪血清样品中L-Trp的测定,回收率为93.1%~105.9%,说明该电极在健康养殖生化检测领域有潜在的应用价值.     

L-色氨酸分子印迹传感器敏感膜的制备与性能

以L-色氨酸(L-Trp)为模板分子, 邻苯二胺(o-PD)为功能单体, 在金电极表面原位合成了分子印迹聚合物敏感膜; 通过循环伏安法(CV)、 差示脉冲伏安法(DPV)和电化学阻抗谱法(EIS)考察了该电极的性能. DPV测试结果表明, 在1×10^-8~2×10^-7 mol/L范围内, 峰电流与L-Trp的浓度呈线性关系, 检出限为0.3×10^-8 mol/L; 选择识别性实验结果表明, L-Trp印迹敏感膜的印迹因子达到3.72, 相对于干扰物的选择因子均大于1, 对与L-Trp结构相似的L-酪氨酸(L-Tyr)的选择因子也达到2.30, 说明该印迹膜对L-Trp具有良好的选择性; 识别过程动力学研究结果表明, 印迹膜对L-Trp的识别是一个两步连续发生的过程, 即快结合过程和慢吸附过程.     

L-色氨酸在聚甲基红膜修饰电极上的电化学行为及其分析研究

用循环伏安法制备了聚甲基红膜修饰玻碳电极(PMRE/GCE)。研究了L-色氨酸(L-Trp)在该修饰电极上的电化学行为,探讨了不同缓冲溶液、pH以及扫描速率等的影响。实验表明:在pH=5.5的HAc-NaAc支持电解质中,L-Trp在PMRE/GCE上的电化学氧化反应是一不可逆过程,于0.783V(vs.SCE)处产生一灵敏的氧化峰,峰电流大大增加。氧化峰电流与L-Trp的浓度在2.0×10-6~1.0×10-3mol/L范围内呈良好的线性关系,检出限为8.0×10-7mol/L,样品检测平均回收率为100.16%。     

三聚氰胺分子印迹光子晶体水凝胶膜传感器的制备及应用

该文将光子晶体与分子印迹技术结合，制备了分子印迹光子晶体水凝胶膜（MIPHs）作为光学传感器，用于样品中三聚氰胺的快速识别检测。以三聚氰胺为模板分子，通过垂直沉降自组装、填充聚合、去除模板3个步骤，制备得到了反蛋白石结构的三聚氰胺MIPHs。扫描电子显微镜的形貌表征表明，MIPHs具有高度有序的三维大孔结构。该MIPHs作为光学传感器可以将三聚氰胺的分子特异识别过程转换成光学信号，在对目标分析物分析时具有选择性高、响应快、灵敏度高的优点。此外，可以根据MIPHs的颜色变化利用图像软件分析或裸眼识别的方式实现目标分析物快速识别。实验结果表明，在最优条件下，三聚氰胺浓度为10^-11~10^-6mol/L时，MIPHs的布拉格衍射峰位移从563 nm红移到608 nm，而对三聚氰胺的结构类似物没有明显响应。     

亚硝酸根和L-色氨酸在多壁碳纳米管、氧化石墨烯和羧甲基壳聚糖修饰的玻碳电极上的电化学行为及其含量测定

将氧化石墨烯(GO)、多壁碳纳米管(MWNTs)和羧甲基壳聚糖(CMCS)超声混合后滴涂到玻碳电极(GCE)基体上得到修饰电极(MWNTs/GO/CMCS/GCE),采用循环伏安法(CV)考察NO2-和L-色氨酸(L-Trp)在修饰电极上的电化学行为。计算得MWNTs/GO/CMCS/GCE的有效面积为3.243 0×10-6cm2,电极膜表面积明显增加,加速了电子转移,有利于被测物质的吸附和富集。结果表明:NO2-(在pH 4.7磷酸盐缓冲溶液中)和L-Trp(在pH 4.0乙酸-乙酸钠缓冲溶液中)在该修饰电极上分别有明显的电催化氧化作用;两者的浓度依次在1.0×10-7~3.5×10-1 mol·L-1和1.0×10-8~2.7×10-1 mol·L-1内与其相应的氧化峰电流值之间呈线性关系,其检出限(3S/N)依次为1.2×10-8,5.0×10-8 mol·L-1。方法用于腐败生菜中NO2-含量和模拟样品中L-Trp含量的CV测定,所得测定结果分别与紫外-可见分光光度法和荧光光度法的测定结果相符。     

L-色氨酸在金纳米粒子修饰电极上的电化学行为及其分析研究

制备了金纳米粒子修饰玻碳电极(Au/GCE),用循环伏安法研究L-色氨酸(L-Trp)在修饰电极上的电化学行为,以及支持电解质、溶液p H、扫描速率等对L-Trp伏安响应的影响。实验表明:在p H=3.5的HAcNa Ac支持电解质中,L-Trp在Au/GCE上有一灵敏的氧化峰(Epa=0.93)。氧化峰电流与L-Trp浓度在5.0×10-7~1.0×10-4mol·L-1范围内呈良好的线性关系,相关系数为0.9990,检出限1.6×10-7mol·L-1。测得L-Trp样品平均回收率为98%。     

2,4,6-三氯酚分子印迹光子晶体水凝胶传感器的研究

以SiO2三维光子晶体为模板,2,4,6-三氯酚为印迹分子,甲醇为溶剂,甲基丙烯酸为功能单体,乙二醇二甲基丙烯酸甲酯为交联剂,通过紫外光引发聚合,在2%氢氟酸溶液中去除光子晶体模板,0.015 mol/L NaOH溶液中洗脱印迹分子,制得2,4,6-三氯酚检测用分子印迹光子晶体水凝胶传感器。结果表明,传感器对2,4,6-三氯酚具有良好的响应与识别能力,在2,4,6-三氯酚浓度由0增加到6×10-4 mol/L过程中,吸收峰红移31 nm;浓度继续增加,吸收峰开始发生蓝移;当浓度增加到1×10-3 mol/L时,吸收峰蓝移56 nm,响应时间仅需要30 min。2,4,6-三氯酚分子印迹光子晶体水凝胶传感器具有高灵敏、高选择、易操作等优点,可实现对2,4,6-三氯酚的裸眼检测。     

抗坏血酸分子印迹电化学传感器的研制与应用

以抗坏血酸(AA)为模板分子,邻苯二胺(o-PD)为功能单体,采用循环伏安法(CV)在玻碳电极表面电聚合形成聚邻苯二胺(PPD)膜,经水将模板分子洗脱后,制得抗坏血酸分子印迹膜电极。优化的分子印迹条件为:以0.20 mol/L HAc-NaAc(pH 5.2)缓冲溶液为反应介质,o-PD和AA的摩尔比为1∶2,扫描电位为0~0.8 V,扫描速度为50 mV/s。利用CV、方波伏安法(SWV)和电流-时间曲线法(I~t)对该分子印迹传感器的电化学性能进行评价。该传感器的响应电流与AA浓度在低浓度区(1.0×10-6~1.0×10-3mol/L)和高浓度区(1.0×10-3~4.5×10-3mol/L)分别呈良好的线性关系,检出限为4.9×10-7mol/L。运用建立的方法对市售橙汁中的AA进行测定,并用2,6-二氯酚靛酚滴定法进行验证,结果表明,该传感检测技术快速、准确、成本低,适用于橙汁等食品中AA的测定。     

利用分子印迹传感器选择性测定绿麦隆

以绿麦隆为模板分子,邻氨基酚为功能单体,在金电极表面电聚合制得具有特异性识别孔穴的绿麦隆分子印迹膜。采用循环伏安、差分脉冲伏安法研究了印迹膜的性能、结构、分子印迹效应和模板分析物,并比较了传感器对其它结构相似化合物的选择性响应,发现该传感器对绿麦隆检测具有良好的选择性。绿麦隆浓度在3.0×10-7~1.5×10-6mol/L范围内与峰电流呈线性关系,检出限为1.0×10-7mol/L,在干扰物质共存情况下的回收率为105%~116%。     

Asymmetric catalysis as a method for the synthesis of chiral organophosphorus compounds

This review discusses methods for the metallo-, organo- and biocatalytic asymmetric synthesis of chiral organophosphorus compounds with many applications in stereoselective synthesis with references to updated literature reports as well as the author’s original research. Asymmetric catalytic hydrogenation and reduction with chiral organometallic complexes, together with actively used asymmetric organocatalytic versions of various reactions enable us to synthesize chiral organophosphonates and phosphinates with high enantioselectivity and purity. Asymmetric catalysis is also an effective tool to realize some classic reactions of phosphorus chemistry in a stereospecific manner.     

Study of intramolecular aminolysis in peptides containing N-alkylamino acids at position 2

Many peptides and proteins, containing N^α-alkylamino acids (including proline) at the second position, are prone to intramolecular aminolysis (IA) with elimination of N-terminal dipeptide sequence as 2,5-diketopiperazines (DKP). We synthesized a series of short peptides, containing N-alkylamino acids at position 2, and studied their stability in the presence of acetic acid and amines. The presence of side chains in the second and the third amino acid residues and alkylation at N^α of the third amino acid residue slowed down IA. N^α-Alkyl residue in the first amino acid residue impeded IA only in peptides, containing three or more residues. Side chains of the first amino acids did not affect significantly the cleavage rates. Acetic acid promoted IA more strongly than aqueous ammonia, while tertiary amines were less effective. Peptides with methionine-S-oxide residues were more labile than the unoxidized analogs, suggesting intramolecular assistance of the S-oxide group in aminolysis. Surprisingly, intermediate compounds of the formula Boc–Met-MeXaa-Sar–NHR underwent rapid cleavage (endopeptolysis) upon attempted acidolytic deprotection.     

Natural and artificial light-harvesting systems utilizing the functions of carotenoids

Carotenoids are essential pigments in natural photosynthesis. They absorb in the blue–green region of the solar spectrum and transfer the absorbed energy to (bacterio-)chlorophylls, and so expand the wavelength range of light that is able to drive photosynthesis. This process is an example of singlet–singlet energy transfer and so carotenoids serve to enhance the overall efficiency of photosynthetic light reactions. Carotenoids also act to protect photosynthetic organisms from the harmful effects of excess exposure to light. In this case, triplet–triplet energy transfer from (bacterio-)chlorophyll to carotenoid plays a key role in this photoprotective reaction. In the light-harvesting pigment–protein complexes from purple photosynthetic bacteria and chlorophytes, carotenoids have an additional role, namely the structural stabilization of those complexes. In this article we review what is currently known about how carotenoids discharge these functions. The molecular architecture of photosynthetic systems will be outlined to provide a basis from which to describe the photochemistry of carotenoids, which underlies most of their important functions in photosynthesis. Then, the possibility to utilize the functions of carotenoids in artificial photosynthetic light-harvesting systems will be discussed. Some examples of the model systems are introduced.     

Synthesis,characterization, powder XRD and antimicrobial-antioxidant activity evaluation of trivalent transition metal macrocyclic complexes

The in vitro antimicrobial and antioxidant activities of metal complexes derived from 1,8-diaminonaphthalene and 5,5-dimethylcyclohexane-1,3-dione were evaluated. The complexes were synthesized by template method in the presence of trivalent metal salts, resulting in the formation of tetraaza macrocyclic complexes of the type [M (C₃₆H₃₆N₄) X] X₂, where M = Cr(III), Fe(III) and X = Cl^–, NO₃^–, CH₃COO^–. The synthesized complexes were characterized with the aid of elemental analyses, molar conductance measurements, magnetic susceptibility measurements, electronic, IR, mass and powder XRD studies. Based on various studies, a five-coordinated square pyramidal geometry was proposed for these complexes. The X-ray diffraction studies suggest a monoclinic crystal system for the complexes.     

Interrelationship between total volatile organic compounds emissions,structure and properties of natural rubber/polycaprolactone bio-blends cross-linked with peroxides

Natural rubber/polycaprolactone (NR/PCL) bio-based blends with different organic peroxides were prepared using an internal batch mixer and subsequently cross-linked at 170 °C. Two types of commonly used organic peroxides, dicumyl peroxide and di(tert-butylperoxyisopropyl)benzene peroxide, were applied as free-radical initiator. Cross-linking efficiency of NR/PCL blends were investigated using oscillating disc rheometer measurements, followed by infrared spectroscopy, thermogravimetric analysis, differential scanning calorimetry, dynamic mechanical analysis and tensile testing. Total volatile organic compounds (TVOCs) emissions were determined using headspace analysis integrated with gas chromatography with flame ionization detector. Determined TVOCs emissions varying in range 21.6–52.1 μg/g and generally value of this parameter decreased with increasing content of PCL phase in studied blends or with application of more efficient di(tert-butylperoxyisopropyl)benzene peroxide as cross-linking agent. It was found that increasing of TVOCs parameter indicated deterioration of mechanical properties of NR/PCL blends, which corresponded with the changes in chemical structure and thermal properties of cross-linked NR/PCL. This confirms that evaluation of TVOCs parameter is interesting alternative for “conventional methods” to characterization of the studied bio-based blends.     

Tuning the properties of a black TiO2-Ag visible light photocatalyst produced by a rapid one-pot chemical reduction

A highly efficient black TiO₂-Ag photocatalytic nanocomposite, active under both UV and visible light illumination, was synthesized by decorating the surface of 25 nm TiO₂ particles with Ag nanoparticles. The material was obtained via a rapid, one-pot, simple (surfactant and complexing agent free) chemical reduction method using silver nitrate and formaldehyde as a metal salt and reducing agent, respectively. The nanocomposite shows an increase of over 800% in the rate of photocatalytic methylene blue dye degradation, compared to commercial unmodified TiO_2, under UV-VIS illumination. Unlike pure TiO₂, the nanocomposite exhibits visible light activation, with a corresponding drop in optical reflectance from 100% to less than 10%. The photocatalytic properties were shown to be strongly enhanced by post-reduction annealing heat treatments in air, which were observed to decrease, rather than coarsen, silver particle size, and increase particle distribution. This, accompanied by a variation in the silver surface oxidation states, appear to dramatically affect the photocatalytic efficiency under both UV and visible light. This highly active photocatalyst could have wide ranging applications in water and air pollution remediation and solar fuel production.     

Identification of potential inhibitor and enzyme-inhibitor complex on trypanothione reductase to control Chagas disease

Chagas is a parasitic disease with major threat to public health due to its resistance against commonly available drugs. Trypanothione reductase (TryR) is the key enzyme to develop this disease. Though this enzyme is well thought-out as potential drug target, the accurate structure of enzyme-inhibitor complex is required to design a potential inhibitor which is less available for TryR. In this research, we aimed to investigate the advanced drug over the available existing drugs by designing inhibitors as well as to identify a new enzyme-inhibitor complex that may act as a template for drug design. A set of analogues were designed from a known inhibitor Quinacrine Mustard (QUM) to identify the effective inhibitor against this enzyme. Further, the pharmacoinformatics elucidation and structural properties of designed inhibitor proposed effective drug candidates against Chagas disease. Molecular docking study suggests that a designed inhibitor has higher binding affinity in both crystal and modeled TryR and also poses similar interacting residues as of crystal TryR-QUM complex structure. The comparative studies based on in silico prediction proposed an enzyme-inhibitor complex which could be effective to control the disease activity. So our in silico analysis based on TryR built model, Pharmacophore and docking analysis might play an important role for the development of novel therapy for Chagas disease. But both animal model experiments and clinical trials must be done to confirm the efficacy of the therapy.     

Photochemical tuning of materials: A click chemistry perspective

Light driven reactions are perpetual tools for environment sustainability. As an external trigger, most of the photon driven reactions are stereoselective, precise, efficient and offer temporal control for biomolecules. The photoinduced reactions are key to unique molecular transformations that include click and unclick reactions. Since 2003, there has been an exponential rise research papers citing light driven reactions. This review considers the light promoted development and modification of reactions that fall under the criteria of ‘Click’ series of transformations. The review lays emphasis on the light induced biochemical, carbohydrate modification, surface labelling, bioconjugation, polymer modification, dendrimer synthesis, [4 + 2] and [2 + 2] reaction, thiol–ene/yne coupling, Cu assisted cycloaddition, strain-promoted azide alkyne cycloaddition (SPAAC), nitro photoclick and photounclick reactions published in last one and half decade. This series of photoclick reactions use short wavelength radiations and are instant, clean, and near to perfect for transforming reactants to the desirable products.     

Simultaneous estimation of detection sensitivity and absolute copy number from digital PCR serial dilution

Digital polymerase chain reaction (dPCR) is a refinement of the conventional PCR approach to nucleic acid detection and absolute quantification. Digital PCR works by partitioning a sample of DNA or cDNA into many individual, parallel PCR reactions. Current quantification methods rely on the assumption that the PCR reactions are always able to detect single target molecules. When the assumption does not hold, the copy numbers will be severely underestimated. We developed a novel dPCR quantification method which determines whether the single copy assumption is violated or not by simultaneously estimating the assay sensitivity and the copy numbers using serial dilution data sets. The implemented method is available as an R package “digitalPCR”.