Amplification reactions in microanalysis. A survey

Amplification reactions have been known for a long time, even if not always under this name. They are an alternative to analyze very small amounts of substance. Definitions and basic terms are given and the various possibilities for such reactions so far known are discussed, not all of the methods described here are of practical use.     

Review: Amplification reactions; origins and definitions-progress and present status

Amplification reactions provide a chemical means of enhancing the sensitivity of an analytical measurement. This review describes the various types of amplification reactions currently available, proposes a systematic classification scheme for them and also provides a comprehensive account of amplification reactions for a wide variety of analytes.     

Amplification of asymmetric induction in sequential reactions of bis-diazoacetates catalyzed by chiral dirhodium(II) carboxamidates

[reaction: see text] Two sequential intramolecular carbon-hydrogen insertion or cyclopropanation reactions of bis-diazoacetates using chiral dirhodium(II) carboxamidate catalysts are reported. The initial metal carbene transformation forms an excess of one enantiomer that with the second transformation further enhances stereocontrol (kinetic amplification). Diastereoselectivity and enantioselectivity for product formation are controlled by the catalyst.     

Ultrasensitive Fluorescence Polarization Aptasensors Based on Exonuclease Signal Amplification and Polystyrene Nanoparticle Amplification

Here, we combine T7 exonuclease (T7 Exo) signal amplification and polystyrene nanoparticle (PS NP) amplification to develop novel fluorescence polarization (FP) aptasensors. The binding of a target/open aptamer hairpin complex or a target/single‐stranded aptamer complex to dye‐labeled DNA bound to PS NPs, or the self‐assembly of two aptamer subunits (one of them labeled with a dye) into a target/aptamer complex on PS NPs leads to the cyclic T7 Exo‐catalyzed digestion of the dye‐labeled DNA or the dye‐labeled aptamer subunit. This results in a substantial decrease in the FP value for the amplified sensing process. Our newly developed aptasensors exhibit a sensitivity five orders of magnitude higher than that of traditional homogeneous aptasensors and a high specificity for the target molecules. These distinct advantages of our proposed assay protocol make it a generic platform for the design of amplified aptasensors for ultrasensitive detection of various target molecules.     

Response Amplification of an Ion-Selective Electrode

Abstract

The response of an ion-selective electrode can be amplified by connecting the cell, which is composed of an ion-selective electrode and a reference electrode, in series. For a cell using 1, 2 or 3 valinomycin electrodes connected in series, the response slopes to 1 × 10^?5 ?1 × 10^?1 M K⁺ were 58, 116 and 174 mV/activity decade (a.d.) at 25°C, respectively. This amplification method would especially be useful for accurate determinations with electrodes in the range of low concentrations outside the Nernstian response or for determinations of polyvalent ions, in which both cases exhibit small emf response changes in changing the ion concentration.     

单细胞核酸编码扩增成像分析

单细胞成像可在单细胞水平观测目标物位置、 确定目标物含量, 在生命科学与临床医学研究领域应用广泛. 核酸编码扩增技术利用特定分子反应将待测目标识别转化为核酸条码的扩增, 具有探针种类多、 易编程、 反应条件温和及信号放大效率高等特点, 在单细胞低丰度、 高灵敏、 多目标物成像中优势显著, 为理解细胞状态、 探索生命过程提供了新思路. 本文综合评述了核酸编码扩增在单细胞荧光成像领域的研究进展, 以目标物的编码方式为分类依据, 系统阐述了固定细胞原位成像和活细胞成像中不同目标物编码与扩增成像方式的区别, 并对活细胞成像中多重检测面临的问题以及未来发展前景进行了展望.     

The Macromolecular Route to Chiral Amplification

Cooperative phenomena, described by one-dimensional statistical physical methods, are observed between the enantiomeric characteristics of monomeric materials and the polymers they produce. The effect of minute energies associated with this amplified chirality, although currently not interpretable, can be easily measured. Nonlinear relationships between enantiomeric excess or enantiomeric content and polymer properties may offer the possibility of developing chiral catalysts and chiral chromatographic materials in which the burden of large enantiomeric excess or content may be considerably alleviated. New approaches to information and sensor technology may become possible.     

Amplification of chirality in liquid crystals

The amplification of molecular chirality by liquid crystalline systems is widely applied in investigations towards enantioselective solvent-solute interactions, chiral supramolecular assemblies, smart materials, and the development of liquid crystal displays. Here we present an overview of recent achievements in the development of new chiral dopant systems for the generation of cholesteric liquid crystalline phases. Based on a distinction between shape-persistent and bistable dopants, several dopant classes will be discussed.     

Applications of Loop-Mediated Isothermal DNA Amplification

During the last 10 years, with the development of loop-mediated isothermal amplification (LAMP) method, it has been widely applied in nucleic acid analysis because of its simplicity, rapidity, high efficiency, and outstanding specificity. This method employs a DNA polymerase and a set of four specially designed primers that recognize a total of six distinct sequences on the target DNA. Expensive equipment are not necessary to acquire a high level of precision, and there are fewer preparation steps compared to conventional PCR and real-time PCR assays. This paper briefly summarized the applications of LAMP method in pathogenic microorganisms, genetically modified ingredients, tumor detection, and embryo sex identification.     

Amplification of chirality in dynamic supramolecular aggregates

The quest to understand the origin of chirality in biological systems has evoked an intense search for nonlinear effects in catalysis and pathways to amplify slight enantiomeric excesses in racemates to give optically pure molecules. The amplification of chirality in polymeric systems as a result of cooperative processes has been intensely investigated. Ten years ago, this effect was shown for the first time in noncovalent dynamic supramolecular systems. Since then, it has become clear that a subtle interplay of noncovalent interactions such as hydrogen-bonding, pi-pi stacking, and hydrophobic interactions is also sufficient to observe amplification of chirality in small molecules. Here we summarize the results obtained over the past decade and the general guidelines we can deduce from them. Predicting amplification of chirality is still impossible, but it appears to be a balance between different types of interactions, the formation of an intrinsically chiral object, and cooperative aggregation processes.     

Mechano-Activated Self-Immolation of Hydrogels via Signal Amplification

Cellular organisms possess intricate mechano-adaptive systems that enable them to sense forces and process them with (bio)chemical circuits for functional adaptation. Inspired by such processes, this study introduces a hydrogel system capable of mechanically activated and chemically transduced self-destruction. Our judiciously designed hydrogels can mechanically generate radicals that are processed and amplified in a self-propagating radical de-crosslinking reaction, ultimately leading to mechanically triggered self-immolation. We put such systems to work in mechano-induced debonding, and in a bilayer actuator, where swelling-induced bending generates sufficient force for selective degradation of one layer, leading to autonomous self-regulation associated with unbending. Our work helps define design criteria for molecularly controlled adaptive and self-regulating materials with embodied mechano-chemical information processing, and showcases their potential for adhesives and soft robotics.     

Amplification of chirality in hydrogen-bonded tetrarosette helices

The amplification of chirality in hydrogen-bonded tetrarosette assemblies under thermodynamic equilibrium is described. The extent of the chiral amplification obtained by means of "sergeants-and-soldiers" experiments depends only on the structure of the assembly and it is independent of the methodology used for the formation of the tetrarosette assemblies. The difference in free energy (deltaG(o)(M/P)) between the M- and P-diastereomeric helices is up to 40 times higher than for double rosette assemblies.     

量热分析化学放大方法及技术

该文从提高选择性、灵敏度和分析性能的角度,在富集、缓冲液放大、非水溶液体系、级联反应等方面评述了量热分析化学热焓放大的原理、方法以及关键技术,其中,富集是通过集聚提升待测物浓度来提高反应焓变;缓冲液放大利用缓冲液的质子焓变增强反应焓变;非水溶液体系可从热容量的角度提升量热灵敏度;级联反应由系列反应或循环完成,最终焓变是系列反应焓变的叠加,达到热焓放大目的。通过结合最新的研究成果和应用进一步阐明化学放大方法实现热焓放大能有效改善和提高量热分析系统的信噪比和降低检出限,并大大加强量热分析方法在现场、实际试样分析测试中的固有应用优势。同时,对当前存在的问题、挑战及未来的研究方向进行了探讨,并展望了其发展趋势和前景。     

Amplification of Chirality in Helical Supramolecular Columns

Strong amplification of chirality occurs in dynamic, but highly ordered, helical columns in n-butanol, for which one chiral seed molecule suffices to render a column of 400 molecules to become homochiral. The chiral columns are formed in a thermally dependent stepwise process. The transition from achiral stacks to helical columns is highly cooperative owing to well-defined intermolecular interactions. `Sergeant and Soldiers' measurements allow for the calculation of the association constant and cooperativity length of the homochiral segments. The `Sergeant and Soldiers' data on the number of molecules within a column show a strikingly good match with data obtained from a theoretical model describing the self-assembly of the discotic molecules as a function of temperature and concentration.     

Plasmonic Nanobiosensor with Chain Reaction Amplification Mechanism

Herein we demonstrate a plasmonic nanobiosensor that explores chain reaction amplification mechanisms to transduce chemical signals released in biocatalytic reactions, turning optical signals into a visual spectral range. The sensor has a very simple design: gold nanoparticles resting in the surface of a grafted P2VP film. Changes in the gold nanoparticles’ position causes changes in the plasmon coupling mode. This is detected by means of a maximum absorbance shift.