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    32060 results match your criteria Analytical Chemistry [Journal]

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    DNA Microviscosity Characterization with Particle Diffusometry for Downstream DNA Detection Applications.
    Anal Chem 2017 Nov 17. Epub 2017 Nov 17.
    Analytical characterization of DNA microviscosity provides critical biophysical insights into nuclear crowding, nucleic acid-based pharmaceutical development, and nucleic acid-based biosensor device design. However, most viscosity characterization methods require large sample volumes and destructive testing. In contrast, particle diffusometry, permits in situ analysis of DNA microviscosity with short measurement times (8 seconds) using small volumes (< 3L) which are compatible with DNA preparatory procedures. Read More

    Acoustic Wave-Driven Functionalized Particles for Aptamer-Based Target Biomolecule Separation.
    Anal Chem 2017 Nov 17. Epub 2017 Nov 17.
    We developed a hybrid microfluidic device that utilized acoustic waves to drive functionalized microparticles inside a continuous flow microchannel and to separate particle-conjugated target proteins from a complex fluid. The acoustofluidic device comprised of an interdigitated transducer (IDT) that produced high-frequency surface acoustic waves (SAW) in a polydimethylsiloxane (PDMS) microfluidic channel. The SAW interacted with the sample fluid flow inside the microchannel and deflected particles from their original streamlines to achieve separation. Read More

    Ratiometric Fluorescence Sensing and Real-Time Detection of Wa-ter in Organic Solvents with One-Pot Synthesis of Ru@MIL-101(Al)-NH2.
    Anal Chem 2017 Nov 17. Epub 2017 Nov 17.
    Ratiometric fluorescence detection attracts much attention because of its decreased environment influence and easy-to-differentiate color and intensity change. Herein, a guest-encapsulation metal organic framework (MOF), Ru@MIL-NH2, is prepared with 2-aminoterephthalic acid, AlCl3, and Ru(bpy)32+ by simple one-pot method for ratiometric fluorescence sensing of water in organic solvents. The rational selection of excitation wavelength provides dual emission at 465 and 615 nm from Ru@MIL-NH2 under single excitation of 300 nm. Read More

    A Dual-Signal Readout Nanosphere for Rapid Point-of-Care Detection of Ebola Virus Glycoprotein.
    Anal Chem 2017 Nov 17. Epub 2017 Nov 17.
    Rapid detection of highly contagious pathogens is the key to increasing the probability of survival and reducing infection rates. We developed a sensitive and quantitative lateral flow assay for detection of EBOV glycoprotein with a novel multifunctional nanosphere (RNs@Au) as a reporter. Each RNs@Au contains hundreds of quantum dots and dozens of Au nanoparticles and can achieve enhanced dual-signal readout (fluorescence signal for quantitative detection and colorimetric signal for visual detection). Read More

    Effect of antigen retrieval methods on non-specific binding of anti-body-metal nanoparticle conjugates on FFPE tissue.
    Anal Chem 2017 Nov 17. Epub 2017 Nov 17.
    Immunohistochemical analysis of FFPE tissues provides important diagnostic and prognostic information in pathology. Metal nanoparticles (NPs) and in particular surface-enhanced Raman scattering (SERS) nanotags as a new class of labelling reagents are promising to be used for multiplexed protein profiling on tissue sections. However, non-specific binding of NPs onto the tissue specimens greatly hampers their clinical applications. Read More

    Raman Spectroscopy of Single Light-Absorbing Carbonaceous Particles Levitated in Air Using an Annular Laser Beam.
    Anal Chem 2017 Nov 17. Epub 2017 Nov 17.
    A laser trapping technique is a powerful means to investigate the physical and chemical properties of single aerosol particles in a non-contact manner. However, optical trapping of strongly light-absorbing particles such as black carbon or soot is quite difficult because the repulsive force caused by heat is orders of magnitude larger than the attractive force of radiation pressure. In this study, a laser trapping and Raman microspectroscopy system using an annular laser beam was constructed to achieve non-contact levitation of single light-absorbing particles in air. Read More

    Rapid Quantification of 4,4'-Methylenedianiline by Surface-Enhanced Raman Spectroscopy.
    Anal Chem 2017 Nov 17. Epub 2017 Nov 17.
    Methylenedianiline (MDA) is a common industrial chemical with health and product safety concerns. Common analysis methods require many steps including extraction and derivatization ending in GC-MS or HPLC analysis, which minimize its use as an on-line or at-line technique. The procedure can take hours, prohibiting its use as a real-time decision-making tool as well as using valuable resources and laboratory space. Read More

    Evaluating the Rate and Substrate Specificity of Laboratory Evolved XNA Polymerases.
    Anal Chem 2017 Nov 17. Epub 2017 Nov 17.
    Engineered polymerases that can copy genetic information between DNA and xeno-nucleic acids (XNA) hold tremendous value as reagents in future bio-technology applications. However, current XNA poly-merases function with inferior activity relative to their natural counterparts, indicating that current polymerase engineering efforts would benefit from new benchmark-ing assays. Here, we describe a highly parallel, low cost method for measuring the average rate and substrate specificity of XNA polymerases in a standard qPCR instrument. Read More

    LipidQC: Method Validation Tool for Visual Comparison to SRM 1950 Using NIST Interlaboratory Comparison Exercise Lipid Consensus Mean Estimate Values.
    Anal Chem 2017 Nov 17. Epub 2017 Nov 17.
    As advances in analytical separation techniques, mass spectrometry instrumentation, and data processing platforms continue to spur growth in the lipidomics field, more structurally unique lipid species are detected and annotated. The lipidomics community is in need of benchmark reference values to assess the validity of various lipidomics workflows in providing accurate quantitative measurements across the diverse lipidome. LipidQC addresses the harmonization challenge in lipid quantitation by providing a semi-automated process, independent of analytical platform, for visual comparison of experimental results of National Institute of Standards and Technology Standard Reference Material (SRM) 1950 Metabolites in Frozen Human Plasma against benchmark consensus mean concentrations derived from the NIST Lipidomics Interlaboratory Comparison Exercise. Read More

    Ratiometric Detection of Intracellular Lysine and pH with One-Pot Synthesized Dual Emissive Carbon Dots.
    Anal Chem 2017 Nov 16. Epub 2017 Nov 16.
    Recently, the development of new fluorescent probes for the ratiometric detection of target objects inside living cells has received great attention. Normally, the preparation, modification as well as conjugation procedures of these probes are complicated. On this basis, great efforts have been paid to establish convenient method for the preparation of dual emissive nanosensor. Read More

    An Optical Nanoantenna for Single Molecule-Based Detection of Zika Virus Nucleic Acids without Molecular Multiplication.
    Anal Chem 2017 Nov 16. Epub 2017 Nov 16.
    Due to the limited signal-to-background ratio, molecular diagnostics requires molecular amplification of the target molecules or molecular signal amplification after target recognition. For direct molecular detection, we demonstrate a purely physical fluorescence enhancement process which can elevate the fluorescence signal of single fluorescent dyes by several orders of magnitude. To this end, DNA origami-based optical antennas with a height of around 125 nm are used, which utilize metallic nanoparticles to create a hotspot where fluorescence signals are enhanced by plasmonic effects. Read More

    Simultaneous Analysis of a Non-Lipidated Protein and Its Lipidated Counterpart: Enabling Quantitative Investigation of Protein Lipidation's Impact on Cellular Regulation.
    Anal Chem 2017 Nov 16. Epub 2017 Nov 16.
    Here we introduce Protein-Lipidation Quantitation (PLQ) - the first method for quantitative analysis of both a substrate and a product of protein lipidation in a biologically relevant context. Such analysis is required to study roles of protein lipidation in cellular regulation. In PLQ, the substrate is fused with a fluorescent protein to facilitate quantitative detection of both the non-lipidated substrate and the lipidated product. Read More

    Hexavalent Chromium as an Electrocatalyst in DNA Sensing.
    Anal Chem 2017 Nov 16. Epub 2017 Nov 16.
    We report for the first time the use of hexavalent chromium (Cr(VI)) as an electrocatalyst in electrochemical DNA sensing. For both stem-loop probe and linear probe electrochemical DNA sensors, the increase in probe rigidity upon target hybridization alters the accessibility of Cr(VI) to the methylene blue label on the surface-immobilized DNA probes. This change results in an enhancement in the electrocatalytic current when the sensors are interrogated using cyclic voltammetry at a slow scan rate. Read More

    A Versatile Probe for Caffeine Detection in Real-Life Samples via Excitation Triggered Alteration in Sensing Behavior of Fluorescent Organic Nanoaggregates.
    Anal Chem 2017 Nov 16. Epub 2017 Nov 16.
    Excitation triggered alteration in the sensing behavior of fluorescent nanoaggregates was explored in water, considering caffeine as the 'target analyte'. Merely by changing the excitation wavelength, we could specifically excite either the monomeric species or the fluorescent nanoaggregates. The monomer showed highly sensitive interaction with caffeine despite poor selectivity, while the 'strongly associated' fluorescent nanoaggregates displayed relatively high selectivity with low sensitivity. Read More

    Accurate quantification of nucleic acids using hypochromicity measurements in conjunction with UV spectrophotometry.
    Anal Chem 2017 Nov 16. Epub 2017 Nov 16.
    UV absorbance spectrophotometry is widely used for the quantification of nucleic acids. For accurate quantification it is important to determine the hypochromocity of the oligonucleotide or complex nucleic acid structure. The use of thermal denaturation studies in conjunction with UV spectrophotometry to determine hypochromicity requires prolonged, elevated temperatures, which may cause partial hydrolysis of RNA. Read More

    The Effect of Pressure and Temperature on Mid-Infrared Sensing of Dissolved Hydrocarbons in Water.
    Anal Chem 2017 Nov 15. Epub 2017 Nov 15.
    Attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy using a polymer coated internal reflection element/waveguide is an established sensor platform for the detection of a range of organic and hydrocarbon molecules dissolved in water. The polymer coating serves two purposes: to concentrate hydrocarbons from the aqueous phase and to exclude water along with other interfering molecules from the surface of the internal reflection element. Crucial to reliable quantification and analytical performance is the calibration of the ATR-FTIR sensor which is commonly performed in water under mild ambient conditions (i. Read More

    Cellular Analysis Using Microfluidics.
    Anal Chem 2017 Nov 15. Epub 2017 Nov 15.
    Cells are the fundamental building blocks of life. Changes within a cell can propagate throughout much larger, more complex systems. Understanding how these changes arise internally within a cell and how cellular signals are transmitted through larger systems of cells, whether those systems be an organ, organism or a larger environmental assemblage, are critical, for example, to understanding how diseases arise and spread and how cells communicate and coordinate their actions. Read More

    Direct Analysis of Lignin Phenols in Freshwater Dissolved Organic Matter.
    Anal Chem 2017 Nov 15. Epub 2017 Nov 15.
    A novel approach for the analysis of dissolved lignin in freshwaters is presented. Lignin concentrations in natural waters are low and a lignin extraction is usually required to obtain sufficient sample for analysis. In this method, extraction and dry down of the dissolved lignin are omitted and alkaline CuO oxidation is directly performed using 15 mL water sample in a microwave digestion system, thus reducing the required amount of sample and its preparation time considerably. Read More

    Novel Aerosol Phase Extraction Method for the Determination of Ca, K, Mg and Na in Biodiesel Through Inductively Coupled Plasma Atomic Emission Spectrometry.
    Anal Chem 2017 Nov 15. Epub 2017 Nov 15.
    A novel extraction method was developed, optimized and validated for the elemental analysis of organic samples. The method, called aerosol phase extraction (APE), was based on the nebulization of the extracting aqueous solution (0.1 mol L-1 nitric acid) on the sample. Read More

    Direct Exosome Quantification via Bivalent-Cholesterol-Labeled DNA Anchor for Signal Amplification.
    Anal Chem 2017 Nov 15. Epub 2017 Nov 15.
    Exosomes, as an important subpopulation of extracellular vesicles (EVs), play an important role in intercellular communications in various important pathophysiological processes, especially cancer-related. However, reliable and convenient quantitative methods for their determination are still technically challenging. In this study, we developed an efficient and direct method by combining immunoaffinity and lipid membrane surface modification into a single platform for specific isolation and accurate quantification of exosomes. Read More

    Dissolution of Pt during Oxygen Reduction Reaction Produces Pt Nanoparticles.
    Anal Chem 2017 Nov 15. Epub 2017 Nov 15.
    Department of Chemistry and Biochemistry, Queens College-CUNY , Flushing, New York 11367, United States.
    The loss of Pt during the oxygen reduction reaction (ORR) affects the performance and economic viability of fuel cells and sensors. Our group previously observed the dissolution of Pt nanoelectrodes at moderately negative potentials during the ORR. Here we report a more detailed study of this process and identify its product. Read More

    Determination of Cancer Cell Based pH-Sensitive Fluorescent Carbon Nanoparticles of Cross-linked Polydopamine by Fluorescence Sensing of Alkaline Phosphatase Activity on Coated Surfaces and Aqueous Solution.
    Anal Chem 2017 Nov 15. Epub 2017 Nov 15.
    The tumor-specific sensitive fluorescence sensing of cellular alkaline phosphatase (ALP) activity based on host-guest specific and pH sensitive by ere conducted on coated surfaces and aqueous states. Cross-linked fluorescent nanoparticles (C-FNP) consisting of β-cyclodextrin (β-CD)/boronic acid (BA) and fluorescent hyaluronic acid [FNP(HA)] were conjugated to fluorescent polydopamine [FNP(pDA)]. To determine the quenching effect of this system, hydrolysis of 4-nitrophenyl phosphate (NPP) to 4-nitrophenol (NP) was performed in the cavity of β-CD in the presence of ALP activated photo-induced electron transfer (PET) between NP and C-FNP. Read More

    Instantaneous Colorimetric and Fluorogenic Detection of Phosgene with a Meso-Oxime-BODIPY.
    Anal Chem 2017 Nov 15. Epub 2017 Nov 15.
    The meso-oxime-substituted-1,3,5,7-tetramethyl BODIPY (1-oxime) was developed into a colorimetric and fluorogenic probe to selectively detect and quantify phosgene. The fast (< 10 s) and sensitive (LOD = 0.09 ppb) phosgene detection is achieved by the conversion of the meso-oxime to the meso-nitrile, resulting in a large fluorescence turn-on response. Read More

    Enzyme-free Nucleic Acid Amplification Assay Using a Cellphone-Based Well Plate Fluorescence Reader.
    Anal Chem 2017 Nov 14. Epub 2017 Nov 14.
    Nucleic acids, DNA and RNA, provide important fingerprint information for various pathogens and have significant diag-nostic value; however, improved approaches are urgently needed to enable rapid detection of nucleic acids in simple point-of-care formats with high sensitivity and specificity. Here, we present a system that utilizes a series of toehold-triggered hy-bridization/displacement reactions that are designed to convert a given amount of RNA molecules (i.e. Read More

    Synchrotron-based high angle resolution and high lateral resolution X-ray diffraction reveals lead white pigment qualities in Old Masters paintings.
    Anal Chem 2017 Nov 14. Epub 2017 Nov 14.
    Micro-samples collected on 28 major paintings by Old European Masters dating from the Middle Ages to the late 19th c. were analyzed using Synchrotron-based X-ray diffraction. Two complementary analytical configurations were used at beamlines ID22 (high-angle resolution) and ID21 (high lateral resolution), in order to highlight markers of the different grades of the lead white pigments (mixture of cerussite PbCO3 and hydrocerussite Pb3(CO3)2(OH)2). Read More

    Quantifying missing (phospho)proteome regions with the broad-specificity protease subtilisin.
    Anal Chem 2017 Nov 14. Epub 2017 Nov 14.
    Despite huge efforts to map the human proteome using mass spectrometry the overall sequence coverage achieved to date is still below 50%. Reasons for missing areas of the proteome comprise protease-resistant domains including the lack/excess of enzymatic cleavage sites, non-unique peptide sequences, impaired peptide ionization/separation and low expression levels. To access novel areas of the proteome the beneficial use of enzymes complementary to trypsin, such as Glu-C, Asp-N, Lys-N, Arg-C, LysArginase has been reported. Read More

    Elucidating Protein- Ligand Recognition with Combined Surface Plasmon Resonance and Surface Enhanced Raman Spectroscopy.
    Anal Chem 2017 Nov 14. Epub 2017 Nov 14.
    The ability to distinguish between specific and non-specific binding is important for assessing the interactions between protein receptors and ligands. Surface plasmon resonance (SPR) spectroscopy is an advanced tool to measure the binding events, yet the ability to distinguish between specific and non-specific binding remains a limitation. To address this problem, we use SPR spectroscopy correlated with surface enhanced Raman scattering (SERS). Read More

    Photoelectrochemical Immunoassays.
    Anal Chem 2017 Nov 14. Epub 2017 Nov 14.
    As an essential direction of photoelectrochemical (PEC) bioanalysis, PEC immunoassays have attracted substantial research scrutiny for its desirable combination of the inherent sensitivity of the PEC bioanalysis and the specific bioaffinity properties of the immunomolecules. The past five years have witnessed substantial advances toward the development of PEC immunoassays, and numerous approaches to advanced PEC immunoassays have been established. Although the summaries on specific topics, such as the PEC DNA biosensors, PEC aptasensing, PEC enzymatic biosensors or the general development of PEC bioanalysis, have been presented in previous reviews, no in-depth survey has yet been made for addressing specifically on the important category of PEC immunoassays. Read More

    Evaluating the effect of phosphorylation on the structure and dynamics of Hsp27 dimers by means of ion mobility mass spectrometry.
    Anal Chem 2017 Nov 14. Epub 2017 Nov 14.
    The quaternary structure and dynamics of the human small heat-shock protein Hsp27 is linked to its molecular chaperone function and influenced by post-translational modifications, including phosphorylation. Phosphorylation of Hsp27 promotes oligomer dissociation and can enhance chaperone activity. This study explored the impact of phosphorylation on the quaternary structure and dynamics of Hsp27. Read More

    Time-Dependent Determination of Unbiased Selectivity Coefficients of Ion-Selective Electrodes for Multivalent Ions.
    Anal Chem 2017 Nov 14. Epub 2017 Nov 14.
    A new method for the determination of unbiased low selectivity coefficients for two of the most prevalent cases of multivalent ions (zi = 2, zj = 1 and zi = 1, zj = 2) was theoretically and experimentally substantiated. The method is based on eliminating the primary ion concentration near the membrane by extrapolating the linearized time-dependencies of selectivity coefficients determined by the separate solutions method (KijPot(SSM))) as a function of t^-1/3 or t^-1/6, depending on the charge combination of the two ions, to infinite time. The applicability of the method is demonstrated for ionophore-based Mg2+-, Ca2+- and Na+-selective electrodes. Read More

    Confocal Raman Microscopy for the Determination of Protein and Quaternary Ammonium Ion Loadings in Biocatalytic Membranes for Electrochemical Energy Conversion and Storage.
    Anal Chem 2017 Nov 14. Epub 2017 Nov 14.
    The need to immobilize active enzyme, while ensuring high rates of substrate turnover and electronic charge transfer with an electrode, is a centrally important challenge in the field of bioelectrocatalysis. In this work, we demonstrate the use of confocal Raman microscopy as a tool for quantitation and molecular-scale structural characterization of ionomers and proteins within biocatalytic membranes to aid in the development of energy efficient biofuel cells. A set of recently available short side chain Aquivion ionomers spanning a range of equivalent weight (EW) suitable for enzyme immobilization was investigated. Read More

    Solid, Semi-Solid, and Liquid Phase States of Individual Submicrometer Particles Directly Probed Using Atomic Force Microscopy.
    Anal Chem 2017 Nov 14. Epub 2017 Nov 14.
    Currently, the impact of various phase states of aerosols on the climate is not well understood, especially for submicrometer sized aerosol particles that typically have extended life time in the atmosphere. This is largely due to the inherent size-limitations present in current experimental techniques that aim to directly assess the phase states of fine aerosol particles. Here-in we present a technique that uses atomic force microscopy (AFM) to directly probe for the phase states of individual, submicrometer particles by using nanoindentation and nano-Wilhelmy methodologies as a function of relative humidity (RH) and ambient temperature conditions. Read More

    Multidimensional Spectral Fingerprints of a New Family of Coherent Analytical Spectroscopies.
    Anal Chem 2017 Nov 14. Epub 2017 Nov 14.
    Triply Resonant Sum Frequency (TRSF) and Doubly Vibrationally Enhanced (DOVE) spectroscopies are examples of a recently developed family of Coherent Multidimensional Spectroscopies (CMDS) that are analogous to current analytical spectroscopies. They are based on creating quantum mechanical superposition states that are fully coherent and lack intermediate quantum state populations that cause quenching or other relaxation effects. They provide multidimensional spectral fingerprints consisting of mixtures of vibrational and electronic states. Read More

    Peptide Arrays: Development and Application.
    Anal Chem 2017 Nov 14. Epub 2017 Nov 14.
    Peptide arrays are an exciting and rapidly growing technology with a broad range of applications in the basic and applied life sciences. Peptide arrays have been under development for approximately twenty-five years, and commercial versions have been available for the past decade. The arrays typically comprise hundreds to thousands of distinct peptide sequences, and have proven important for determining substrate specificities of enzymes, profiling antibodies and mapping epitopes, studying ligand-receptor interactions and identifying ligands that mediate cell adhesion. Read More

    Raman-DIP (Deuterium Isotope Probing) Reveals Microbial Metabolism at the Single-Cell Level.
    Anal Chem 2017 Nov 14. Epub 2017 Nov 14.
    We illustrate that single-cell Raman microspectroscopy, coupled with deuterium isotope probing (Raman-DIP), provides a culture-independent and non-destructive approach to probe metabolic pathways of carbon substrates at the single-cell level. We find a clearly distinguishable C-D vibration band at 2070 - 2300 cm-1 in single-cell Raman spectra (SCRS) when Escherichia coli used deuterated glucose and Pseudomonas sp. used deuterated naphthalene as sole carbon sources. Read More

    A high time resolution optical sensor for monitoring atmospheric nitrogen dioxide.
    Anal Chem 2017 Nov 14. Epub 2017 Nov 14.
    High-time resolution monitoring nitrogen dioxide (NO2) is of great importance for studying the formation mechanism of aerosol and improving air quality. Based on the Griess-Saltzman (GS) reaction, a portable NO2 optical sensor was developed by employing a porous polypropylene membrane tube (PPMT) integrated gas permeation collector and detector. The PPMT was filled with GS reagents and covered with a coaxial jacket tube for gas collection. Read More

    Ultra-flat, Pristine and Robust Carbon Electrode for Fast Electron Transfer Kinetics.
    Anal Chem 2017 Nov 14. Epub 2017 Nov 14.
    Electron-beam (E-beam) deposition of carbon on a gold substrate yields a very flat (0.43 nm of root-mean-square roughness), amorphous carbon film consisting of a mixture of sp2 and sp3 hybridized carbon with sufficient conductivity to avoid ohmic potential error. E-beam carbon (eC) has attractive properties for conventional electrochemistry, including low background current and sufficient transparency for optical spectroscopy. Read More

    On-line Differential Thermal Isotope Analysis of Hydration Water in Minerals by Cavity Ring-down Laser Spectroscopy.
    Anal Chem 2017 Nov 13. Epub 2017 Nov 13.
    We have developed a new method for measuring the isotopic composition (δ18O and δD) of different types of bonded water (e.g., molecular water, hydroxyl) contained in hydrated minerals by coupling a thermal gravimeter (TG) and a cavity ringdown laser spectrometer (CRDS). Read More

    Drift Tube Ion Mobility: How to Reconstruct Collision Cross Section Distributions from Arrival Time Distributions?
    Anal Chem 2017 Nov 13. Epub 2017 Nov 13.
    Ion mobility spectrometry allows one to determine ion collision cross sections, which are related to ion size and shape. Collision cross sections (CCS) are usually discussed based on the peak center, yet the width of each peak contains further information on the distribution of collision cross sections of each conformational ensemble. Here, we analyze how to convert arrival time distributions (ATD) to CCS distributions (CCSD). Read More

    An innovative in situ ball mill for X-ray diffraction.
    Anal Chem 2017 Nov 13. Epub 2017 Nov 13.
    The renewed interest of mechanochemistry as an eco-friendly synthetic route has inspired original methodologies to probe reactions, with the aim to rationalize unknown mechanisms. Recently, Friščić et al. [Nat Chem 2013, 5, 66-73] monitored the progress of milling reactions by synchrotron X-ray Powder Diffraction (XRPD). Read More

    A paper-plastic hybrid microfluidic device for smartphone based colorimetric analysis of Urine.
    Anal Chem 2017 Nov 13. Epub 2017 Nov 13.
    In this work, a disposable paper-plastic hybrid microfluidic lab-on-a-chip (LOC) has been developed and successfully applied for the colorimetric measurement of urine by the smartphone-based optical platform using an "UrineAnalysis" Android app. The developed device was cost-effectively implemented as a stand-alone hybrid LOC by incorporating the paper-based conventional reagent test strip inside the plastic-based LOC microchannel. The LOC device quantitatively investigated the small volume (40 µL) of urine analytes for the colorimetric reaction of glucose, protein, pH and red blood cell (RBC) in integration with the finger-actuating micro pump. Read More

    Environmental Nuclear Magnetic Resonance Spectroscopy: An Overview and A Primer.
    Anal Chem 2017 Nov 13. Epub 2017 Nov 13.
    NMR spectroscopy is a versatile tool for the study of structure and interactions in environmental media such as air, soil, and water as well as monitoring the metabolic responses of living organisms to an ever changing environment. Part review, part perspective and part tutorial, this feature is aimed at non-specialists who are interested in learning more about the potential and impact of NMR spectroscopy in environmental research. Read More

    Single-Walled Carbon Nanotubes Probed with Insulator-based Dielectrophoresis.
    Anal Chem 2017 Nov 13. Epub 2017 Nov 13.
    Single-walled carbon nanotubes (SWNTs) offer unique electrical and optical properties. Common synthesis processes yield SWNTs with large length polydispersity (several tens of nanometers up to centimeters) and heterogeneous electrical and optical properties. Applications often require suitable selection and purification. Read More

    Antibody-templated assembly of an RNA mimic of Green Fluorescent Protein.
    Anal Chem 2017 Nov 13. Epub 2017 Nov 13.
    One of the most intriguing ways through which Nature achieves regulation of biological pathways encompasses the coordination of non-covalent interactions that bring biomolecules to be co-localized in a designated restricted space. This nano-confinement leads to a drastic increase in the effective local concentration of the species involved, which ultimately triggers reactions that would otherwise not occur at the low concentrations found in cells. Inspired by this mechanism, we have explored the possibility of using antibodies as bivalent biomolecular substrates for the templated assembly of a functional RNA structure. Read More

    Optically detected magnetic resonance for selective imaging of diamond nanoparticles.
    Anal Chem 2017 Nov 13. Epub 2017 Nov 13.
    While there is great interest in understanding the fate and transport of nanomaterials in the environment and in biological systems, the detection of nanomaterials in complex matrices by fluorescence methods is complicated by photodegradation, blinking, and by the presence of natural organic material and other fluorescent background signals that hamper detection of fluorescent nanomaterials of interest. Optically detected magnetic resonance (ODMR) of nitrogen-vacancy (NV) centers in diamond nanoparticles provides a pathway toward background-free fluorescence measurements, as the application of a resonant microwave field can selectively modulate the intensity from NV centers in the diamond in nanodiamonds of various diameters in complex materials systems using on-resonance and off-resonance microwave fields. This work represents the first investigation showing how nanoparticle diameter impacts the Nv center lifetime and thereby directly impacts the accessible contrast and signal-to-noise ratio when using ODMR to achieve background-free imaging of Nv-nanodiamonds in the presence of interfering fluorophores. Read More

    Structural and Functional Characterization of a Hole-Hole Homodimer Variant in a "Knob-Into-Hole" Bispecific Antibody.
    Anal Chem 2017 Nov 12. Epub 2017 Nov 12.
    Bispecific antibodies have great potential to be the next-generation biotherapeutics due to their ability to simultaneously recognize two different targets. Compared to conventional monoclonal antibodies, knob-into-hole bispecific antibodies face unique challenges in production and characterization due to the increase in variant possibilities, such as homodimerization in covalent and non-covalent forms. In this study, a storage- and pH-sensitive hydrophobic interaction chromatography (HIC) profile change was observed for the hole-hole homodimer, and the multiple HIC peaks were explored and shown to be conformational isomers. Read More

    Endoplasmic reticulum directed ratiometric fluorescent probe for quantitively detection of basal H2O2.
    Anal Chem 2017 Nov 13. Epub 2017 Nov 13.
    The ER has a central role in the fine tuning of environmental and internal stimuli. We herein report a rati-ometric fluorescent probe, α-Naph, capable of determining basal H2O2 in ER. The probe specifically response to H2O2. Read More

    pDeep: Predicting MS/MS Spectra of Peptides with Deep Learning.
    Anal Chem 2017 Nov 10. Epub 2017 Nov 10.
    In tandem mass spectrometry (MS/MS)-based proteomics, search engines rely on comparison between an experimental MS/MS spectrum and the theoretical spectra of the candidate peptides. Hence accurate prediction of the theoretical spectra of peptides appears to be particularly important. Here we present pDeep, a deep neural network- based model for the spectrum prediction of peptides. Read More

    Smart Chiral Sensing Platform with Alterable Enantioselectivity.
    Anal Chem 2017 Nov 17. Epub 2017 Nov 17.
    Advanced Catalysis and Green Manufacturing Collaborative Innovation Center, Changzhou University , Changzhou 213164, China.
    A quinine (QN)-based chiral sensing platform with alterable enantioselectivity is constructed for electrochemical chiral recognition of tryptophan (Trp) isomers. The electrochemical signals of l- and d-Trp on the QN modified electrode depend closely on temperature, and more particularly are reversed at certain temperatures, which could be attributed to the temperature-sensitive H-bonds and π-π interactions between QN and the Trp isomers. The mechanisms of the reverse chiral recognition are investigated by density functional theory (DFT), variable-temperature UV spectra, and variable-temperature (1)H NMR spectra. Read More

    Graphdiyne as Electrode Material: Tuning Electronic State and Surface Chemistry for Improved Electrode Reactivity.
    Anal Chem 2017 Nov 10. Epub 2017 Nov 10.
    Graphdiyne (GDY) is recently synthesized two-dimensional carbon allotrope with hexagonal rings cross-linked by di-acetylene through introducing butadiyne linkages (-C≡C-C≡C-) to form 18-C hexagons and is emerging to be fundamentally interesting and particularly useful in various research fields. In this study, we for the first time find that GDY can be used as an electrode material with reactivity tunable by electronic states and surface chemistry of GDY. To demonstrate this, GDY is oxidized into graphdiyne oxide (GDYO) that is then chemically and electrochemically reduced into chemically reduced GDYO (cr-GDYO) and electrochemically reduced GDYO (er-GDYO), respectively. Read More

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