Evaluation of the oxidase like activity of nanoceria and its application in colorimetric assays

Nanomaterial-based enzyme mimics have attracted considerable interest in chemical analysis as alternative catalysts to natural enzymes. However, the conditions in which such particles can replace biological catalysts and their selectivity and reactivity profiles are not well defined. This work explored the oxidase like properties of nanoceria particles in the development of colorimetric assays for the detection of dopamine and catechol. Selectivity of the system with respect to several phenolic compounds, the effect of interferences and real sample analysis are discussed. The conditions of use such as buffer composition, selectivity, pH, reaction time and particle type are defined. Detection limits of 1.5 and 0.2 μM were obtained with nanoceria for dopamine and catechol. The same assay could be used as a general sensing platform for the detection of other phenolics. However, the sensitivity of the method varies significantly with the particle type, buffer composition, pH and with the structure of the phenolic compound. The results demonstrate that nanoceria particles can be used for the development of cost effective and sensitive methods for the detection of these compounds. However, the selection of the particle system and experimental conditions is critical for achieving high sensitivity. Recommendations are provided on the selection of the particle system and reaction conditions to maximize the oxidase like activity of nanoceria.     

小火试金分离富集火焰原子吸收光谱法测定矿石样品中的金

研究建立了一种有别于传统火试金的分离富集方法--小火试金分离富集矿石中的金，并采用火焰原子吸收光谱仪对金含量进行检测的方法。在小火试金条件的选择中，分别对小火试金熔剂比例、灰吹温度、保护剂用量进行了讨论，确定了这三个参数的最佳值分别为：硼砂-纯碱-黄丹-淀粉比例5∶5∶10∶1，900 ℃，10 mg，将3 g样品经焙烧后，在最佳小火试金条件下分离富集金，铅扣经灰吹得到金、银合金粒，经稀硝酸溶解后，加入盐酸将银与金分离，用火焰原子吸收分光光度计对溶液中的金进行测定，工作中探讨了原子吸收光谱仪测定金的各种影响因素，包括仪器参数优化、线性范围、干扰离子等。干扰实验表明其他共存贵金属元素对金的测量不产生影响，在选定的仪器条件下，对标准样品及某矿送检的金矿石样本中的金进行测定，结果与标准值一致，相对标准偏差（n=11）在0.72%～5.49%之间，方法回收率在98.82%～99.20%之间。此方法稳定可靠，准确度高，对0.X~XX.0 mg·kg-1的矿石中金含量均适用，拓展了火焰原子吸收测量金的含量范围，并且大大降低了传统火试金法对人及环境的伤害和污染，原子吸收光谱法具有响应快、灵敏度高、准确性好等优点，为进一步研究用此法开展其他贵金属的检测奠定了技术基础。     

Influence of the Insertion Method of Aryl-Extended Calix[4]pyrroles into Liposomal Membranes on Their Properties as Anion Carriers

We disclose the results of our investigations on the influence that the insertion method of aryl-extended calix[4]pyrrole into liposomal membranes exerts on their properties as anion carriers. We use the standard HPTS assay to assess the transport properties of the carriers. We show that the post-insertion of the carrier, as DMSO solution, assigns better transport activities to the “two-wall” α,α-aryl-extended calix[4]pyrrole 1 compared to the “four-wall” α,α,α,α-counterpart 2 . Notably, opposite results were obtained when the carriers were pre-inserted into the liposomal membranes. We assign this difference to an improved incorporation of carrier 2 into the membrane when delivered by the pre-insertion method. On the other hand, carrier 1 shows comparable levels of transport independently of the method used for its incorporation. Thus, an accurate comparison of the chloride transport activities featured by these two carriers demands their pre-incorporation in the liposomal membranes. In contrast, using the lucigenin assay with the pre-insertion method both carriers displayed similar transport efficiencies.     

Zelkovamycin is an OXPHOS Inhibitory Member of the Argyrin Natural Product Family

Natural products (NPs) are an important inspirational source for developing drugs and chemical probes. In 1999, the group of Ōmura reported the constitutional elucidation of zelkovamycin. Although largely unrecognized so far, this NP displays structural similarities as well as differences to the argyrin NP family, a class of peptidic NPs with promising anticancer activities and diverse mode-of-action at the molecular level. By a combination of structure elucidation experiments, the first total synthesis of zelkovamycin and bioassays, the zelkovamycin configuration was determined and its previously proposed molecular structure was revised. The full structure assignment proves zelkovamycin as an additional member of the argyrins with however unique OXPHOS inhibitory properties. Zelkovamycin may therefore not only serve as a new starting point for chemical inhibitors of the OXPHOS system, but also guide customized argyrin NP isolation and biosynthesis studies.     

Toward multimarker and functional assays from crude cell lysates: controlling spacing and signal amplification in DNA-CT–based bioelectrochemical devices

DNA-based electrochemical biosensors that rely on charge transport through DNA (DNA-CT) to detect biomarkers of interest have shown great promise in proof-of-principle studies because of their specificity, sensitivity, and low cost. However, this approach has not translated successfully into real clinical applications. One significant barrier has been the need to measure biomarkers in unpurified, complex cell and tissue lysates, which is difficult with DNA-modified electrodes because of crowding and nonspecific adhesion of biomolecules to the surface. Here, we discuss recent achievements in the control of DNA monolayer formation and the amplification of DNA CT signals that help to facilitate the detection of meaningful biomarkers from unprocessed, clinically relevant lysate samples.     

Assays for determination of matrix metalloproteinases and their activity

Matrix metalloproteinases (MMPs) are involved in many physiological and pathological processes. Due to their ability to cleave and to remodel components of surrounding tissues, MMPs may affect cell migration, differentiation, growth, inflammatory processes, neovascularization, wound healing, apoptosis, the uterine cycle and many other actions within the body, including those needed for tumorigenesis and other diseases.MMPs can therefore be used as potential markers for detecting various cancers, neurodegenerative, and immune and cardiovascular diseases. Numerous MMP assays were developed for clinical and research purposes, but far more attention has been devoted to understanding their biological functions.Due to differences in methodology, results obtained in various laboratory settings are difficult to compare because of the lack of standards and analytical methods of validation. Limits of detection of particular methods used for identifying MMPs are also disputable.Enzymatic, immunochemical and fluorimetric methods are particularly suitable for clinical use. In-vivo imaging methods offer many potential advantages in cancer research and diagnostics. Other methods are subject to investigation [e.g., phage display, multiple-enzyme/multiple-reagent assay system (MEMRAS) and activity-based profiling].     

Effect of 1,10-phenanthroline on DNA binding,DNA cleavage,cytotoxic and lactate dehydrogenase inhibition properties of Robson type macrocyclic dicopper(II) complex

DNA targeting macrocyclic dicopper(II) complex, [Cu₂L(H₂O)₂](phen)₂(ClO₄)₂ (L = μ-11,23-dimethyl-3,7,15,19-tetraazatricyclo-[19.3.1.1^9,13,21] he p t a c o s a-1(24), 2, 7, 9, 11, 13(26), 14, 19, 21(25), 22-decaene-25,26-diol) (2), has been synthesized and characterized. This has been synthesized by reacting a Robson type macrocyclic precursor dicopper(II) complex [Cu₂L(H₂O)₂](ClO₄)₂ (1) and 1,10-phenanthroline in ethanol. Solution ESR, electronic, and ESI-MS spectral studies suggest that 1,10-phenanthroline replaces coordinated water in 1, giving 2. The influence of the phenanthroline on DNA binding, cleavage, and anticancer properties of 2 have been investigated. Complex 2 displays better DNA binding and cleavage than 1. The dicopper(II) complexes 1 and 2 show cytotoxicity in human cervical HeLa cancer cells, giving IC₅₀ values of 79.41 and 15.82 μM, respectively. Antiproliferative properties of 1 and 2 were confirmed by Trypan Blue exclusive assay and lactate dehydrogenase enzyme level in HeLa cancer cell lysate and content media.     

An Assay for Screening Potential Drug Candidates for Alzheimer's Disease That Act as Chaperones of the Transthyretin and Amyloid-β Peptides Interaction

The protein transthyretin (TTR) modulates amyloid-β (Aβ) peptides deposition and processing and this physiological effect is further enhanced by treatment with iododiflunisal (IDIF), a small-molecule compound (SMC) with TTR tetramer stabilization properties, which behaves as chaperone of the complex. This knowledge has prompted us to design and optimize a rapid and simple high-throughput assay that relies on the ability of test compounds to form ternary soluble complexes TTR/Aβ/SMC that prevent Aβ aggregation. The method uses the shorter Aβ(12–28) sequence which is cheaper and simpler to use while retaining the aggregation properties of their parents Aβ(1–40) and Aβ(1–42). The test is carried out in 96-plate wells that are UV monitored for turbidity during 6 h. Given its reproducibility, we propose that this test can be a powerful tool for efficient screening of SMCs that act as chaperones of the TTR/Aβ interaction that may led to potential AD therapies.     

Synthesis of novel cytotoxic 3-azolylsteroids via Cu-catalyzed C–N coupling

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Antioxidant activity evaluation by physiologically relevant assays based on haemoglobin peroxidase activity and cytochrome c-induced oxidation of liposomes

Two new protocols for exploring antioxidant-related chemical composition and reactivity are described: one based on a chronometric variation of a haemoglobin ascorbate peroxidase assay and one based on cytochrome c-induced oxidation of lecithin liposomes. Detailed accounts are given on their design, application, critical correlations with established methods and mechanisms. These assays are proposed to be physiologically relevant and bring new information regarding a real sample, both qualitative and quantitative. The well-known assays used for evaluation of antioxidant (re)activity are revisited and compared with these new methods. Extracts of the Hedera helix L. are examined as test case, with focus on seasonal variation and on leaf, fruit and flower with respect to chromatographic, spectroscopic and reactivity properties. According to the set of assays performed, winter are the most antioxidant, followed by summer leaves, and then by flowers and fruits.