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Analytical Chemistry

M Rachel Mehaffey, James D Sanders, Dustin D Holden, Carol L Nilsson, Jennifer S Brodbelt
Unraveling disease mechanisms requires a comprehensive understanding of how the interplay between higher-order structure and protein-ligand interactions impacts the function of a given protein. Recent advances in native mass spectrometry (MS) involving multi-modal or higher energy activation methods have allowed direct interrogation of intact protein complexes in the gas phase, allowing analysis of both composition and subunit connectivity. We report a multi-stage approach combining collisional activation and 193 nm ultraviolet photodissociation (UVPD) to characterize single amino acid variants of the human mitochondrial enzyme branched-chain amino acid transferase 2 (BCAT2), a protein implicated in chemotherapeutic resistance in glioblastoma tumors...
July 17, 2018: Analytical Chemistry
Shuxia Guo, Achim Kohler, Boris Zimmermann, Ralf Heinke, Stephan Stöckel, Petra Roesch, Juergen Popp, Thomas Wilhelm Bocklitz
The chemometric analysis of Raman spectra of biological materials is hampered by spectral variations due to the instrumental setup that overlay the subtle biological changes of interest. Thus, an established statistical model may fail when applied to Raman spectra of samples acquired with a different device. Therefore, model transfer strategies are essential. Herein we report a model transfer approach based on extended multiplicative signal correction (EMSC). As opposed to existing model transfer methods, the EMSC based approach does not require group information of the secondary datasets, thus no extra measurements are required...
July 17, 2018: Analytical Chemistry
Marta Podrażka, Emilia Witkowska Nery, Aleksandra Pacowska, Damien W M Arrigan, Martin Jönsson-Niedziółka
While ion transfer studies were shown to be a promising method for fundamental electrochemistry, pharmacokinetic studies and sensing, they suffer from inherent instability of the interface formed between the organic and aqueous phases. This limits to some extent the range of solvents which can be used and confines these studies to the laboratory. We propose here the use of paper, which has revolutionized the way we think of miniaturized analytical devices during the last decade, as a perfect substrate for ion transfer studies across the liquid-liquid interface...
July 17, 2018: Analytical Chemistry
Sheila Maibom-Thomsen, Søren Heissel, Ejvind Mørtz, Peter Hojrup, Jakob Bunkenborg
Protein sequencing by mass spectrometry has transformed the field of biopharmaceutical analysis but a missing part in the analytical toolkit is the ability to distinguish between the isomeric residues isoleucine and leucine since it is a requisite for efficient analysis of the primary structure of proteins. To address this need, we have developed a novel mass spectrometric method that combines reductive dimethylation and MS3 fragmentation with LCMS peptide mapping. The dimethylation of peptide N-termini leads to intense a1 ions upon collision induced fragmentation and further fragmentation of the isoleucine/leucine a1-ion leads to informative spectra with fragments that can discriminate between the two isomers...
July 17, 2018: Analytical Chemistry
Yanan Zhang, Shan Guo, Zhuoran Jiang, Guobin Mao, Xinghu Ji, Zhike He
A ratiometric fluorescent sensor for mercury ions (Hg2+) has been constructed via covalent functionalization of silicon nanodot (SiND) with Hg2+-specific 6-carboxy-X-rhodamine (Rox)-tagged DNA. For the Rox-DNA functionalized SiND, the red fluorescence of Rox can be quenched by the blue-emitting SiND in the presence of Hg2+ due to structural change in DNA, which serves as the response signal. Meawhile, the fluorescence of SiND is insensitive to Hg2+ and acts as the reference signal. The wavelength difference in the optimal emission peak is as large as 190 nm between SiND (425 nm) and Rox (612 nm), which can efficaciously exclude the interference of the two emission peaks, and facilitates dual-color visualization of Hg2+ ions...
July 17, 2018: Analytical Chemistry
Marcel Kwiatkowski, Dennis Krösser, Marcus Wurlitzer, Pascal Steffen, Andrei Barcaru, Christoph Krisp, Péter Horvatovich, Rainer Bischoff, Hartmut Schlüter
The complexity of mammalian proteomes is a challenge in bottom-up proteomics. For a comprehensive proteome analysis, multidimensional separation strategies are necessary. Online 2D-LC-MS/MS combining SCX in the first dimension with RP chromatography in the second dimension provides a powerful approach to analyze complex proteomes. Although the combination of SCX with RP chromatography provides a good orthogonality, only a moderate separation is achieved in the first dimension for peptides with two (+2) or three (+3) positive charges...
July 17, 2018: Analytical Chemistry
Ahmad Kenaan, Cheng Jin, Qi Daizong, Di Chen, Daxiang Cui, Jie Song
The development of spatiotemporal drug delivery system with long release profile, high loading efficiency, and robust therapeutic effect is still a challenge. Liposomal nanocarriers have secured a fortified position in the biomedical field over decades. Herein, liposomal binary mixtures of 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) and photo-polymerizable 1,2-bis(10,12-tricosadiynoyl)-sn-glycero-3-phosphocholine (DC8,9PC) phospholipids were prepared for drug delivery applications. The diacetylenic groups of DC8,9PC produce intermolecular cross-linking following UV irradiation...
July 16, 2018: Analytical Chemistry
Daniel P Veghte, Swarup China, Johannes Weis, Peng Lin, Mallory Hinks, Libor Kovarik, Sergey A Nizkorodov, Mary K Gilles, Alexander Laskin
Environmental transmission electron microscopy was employed to probe transformations in the size, morphology, and composition of individual atmospheric particles as a function of temperature. Two different heating devices were used and calibrated in this work: a furnace heater and a Micro Electro Mechanical System heater. The temperature calibration utilized sublimation temperatures of NaCl, glucose, and ammonium sulfate particles, and the melting temperature of tin. Volatilization of Suwanee River Fulvic Acid was further used to validate the calibration up to 800 °C...
July 16, 2018: Analytical Chemistry
Valérie Geertsen, Elodie Barruet, Frédéric Gobeaux, Jean-Luc Lacour, Olivier Taché
Small Angle X-rays Scattering Spectroscopy (SAXS) is the method of choice for nanoparticle diameter and concentration determination. It is metrologically traceable for spherical nanoparticle mean diameter determination and does not require any sample preparation or calibration. On the other hand, Single Particle ICPMS (SPICPMS) is still under developments and requires involved process clarification and accuracy improvement. The strategy of this study is the comparison of the two techniques to study comprehensively SPICPMS performance and observe phenomena otherwise hidden...
July 16, 2018: Analytical Chemistry
Daniela-Lee Smith, Michael Goetze, Gene Hart-Smith, Marc R Wilkins, Tara Bartolec
This study investigated the enzyme-substrate interaction between the Saccharomyces cerevisiae arginine methyltransferase Hmt1p and nucleolar protein Npl3p, using chemical crosslinking-mass spectrometry (XL-MS). We show that XL-MS can capture transient inter-protein interactions that occur during the process of methylation, involving a disordered region in Npl3p with tandem SRGG repeats, and confirm that Hmt1p and Npl3p exist as homo-multimers. Additionally, the study investigated the interdependencies between variables of an XL-MS experiment, that lead to the identification of identical or different crosslinked peptides...
July 13, 2018: Analytical Chemistry
Oskar Knittelfelder, Sofia Traikov, Olga Vvedenskaya, Andrea Schuhmann, Sandra Segeletz, Anna Shevchenko, Andrej Shevchenko
Shotgun analysis provides a quantitative snapshot of the lipidome composition of cells, tissues or model organisms, however it does not elucidate the spatial distribution of lipids. Here we demonstrate that shotgun analysis could quantify low-picomole amounts of lipids isolated by laser capture microdissection (LCM) of hundred micrometer-sized histological zones visualized at the cryosections of tissues. We identified metabolically distinct periportal ( pp) and pericentral ( pc) zones by immunostaining of 20 µm-thick cryosections of a healthy mouse liver...
July 13, 2018: Analytical Chemistry
Jinqi Deng, Mingzhu Yang, Jing Wu, Wei Zhang, Xingyu Jiang
Immunoassays whose readouts rely on chemiluminescence are increasingly useful for a broad range of analytical applications, but they are rarely made into point-of-care (POC) format because of the complex reagents required (some reagents have to be stored in low temperatures, and some reagents have to be freshly made right before the assay). This study reports a self-contained chemiluminescent lateral flow assay (CLFA), which prestores all necessary reagents. This CLFA contains three parts: the normal lateral flow assay (LFA) strip, the chemiluminescence substrate pad, and the polycarbonate (PC) holder...
July 13, 2018: Analytical Chemistry
Shamayeeta Ray, Tamasri Senapati, Subhankar Sahu, Rajdip Bandyopadhyaya, Ruchi Anand
Phenol and its derivatives constitute a class of highly toxic xenobiotics that pollute both river and groundwater. Here, we use a highly stable enzyme based in vitro biosensing scaffold to develop a chip-based environmental diagnostic for in situ accurate, direct detection of phenol selectively down to 10 ppb. Mesoporous silica nanoparticles (MCM41) having a pore diameter of 6.5 nm was screened and found to be the optimal solid support for creation of a robust immobilized protein based sensor, which retains stability, enzyme activity, sensitivity and selectivity at par with solution format...
July 13, 2018: Analytical Chemistry
Soroush Kahkeshani, Janay Elise Kong, Qingshan Wei, Derek Tseng, Omai Brandt Garner, Aydogan Ozcan, Dino Di Carlo
We present an approach to estimate the concentration of a biomolecule in a solution by sampling several nanoliter-scale volumes and determining if the volumes contain any biomolecules. In this method, varying volume fractions (nanoliter-scale) of a sample of nucleic acids are introduced to an array of uniform volume reaction wells (100 μL), which are then fluorescently imaged to determine if signal is above a threshold after nucleic acid amplification, all without complex instrumentation. The nanoliter volumes are generated and introduced using the simple positioning of a permanent magnet, and imaging is performed with a cellphone-based fluorescence detection scheme, both methods suitable for limited-resource settings...
July 13, 2018: Analytical Chemistry
Wen Chen, Cai Gao, Xianjun Liu, Feng Liu, Fenglin Wang, Li-Juan Tang, Jian-Hui Jiang
Subcellular viscosity is essential for cell functions and may indicate its physiological status. We screen two fluorescent probes by engineering tetraphenylethene (TPE) for measuring viscosity in mitochondria and lysosomes, respectively. These two probes are only weakly emissive in nonviscous medium and the emission signals are greatly enhanced in viscous medium due to the restriction of intramolecular motion. The presence of pyridium has endowed one probe with mitochondrial specificity, while the presence of indole ring has granted the other probe with lysosome-targeting ability...
July 13, 2018: Analytical Chemistry
Bo Wu, Yi Lin, Bowen Li, Chenyue Zhan, Fang Zeng, Shuizhu Wu
Squaraine dyes have excellent photostability with intensive absorption and strong fluorescence in the near infrared (NIR) region. However, they display a strong tendency to aggregate in aqueous media due to their poor water solubility, often causing fluorescence quenching that severely limits their in-vivo applications especially for detecting/imaging diagnostic enzymes. In this work, an oligo(ethylene glycol)-functionalized squaraine fluorophore has been developed as a NIR fluorescent probe, which can detect/image the activities of diagnostic enzyme (leucine aminopeptidase) both in vitro and in vivo...
July 13, 2018: Analytical Chemistry
Liang Liu, Mathieu Etienne, Alain Walcarius
Scanning electrochemical probe techniques have been widely applied for analyzing the local electrochemical activity of surfaces and interfaces. In this work, we develop a new concept of carrying out local electrochemical measurements by localizing both the electrode and the electrolyte. This is achieved through a gel probe, which is prepared by electrodepositing chitosan-gelatin gel on a micro-disk electrode. It is positioned in contact with the sample surface by shear force feedback. The preliminary results indicate that the topography of the sample can be mapped by tapping the probe and recording the coordinates at a given normalized shear force signal, while the local electrochemical activity can be retrieved from local measurements with the probe touching the sample surface...
July 13, 2018: Analytical Chemistry
Hongding Zhang, Yujie Liu, Kun Zhang, Ji Ji, Jianwei Liu, Baohong Liu
Single-molecule fluorescence imaging is a promising strategy for biomolecule detection. However, the accuracy of single-molecule method is often compromised by the false-positive events at the ultralow sample levels that are caused by the non-specific adsorption of the fluorescent labeled probe and other fluorescent impurities on the imaging surface. Here, we demonstrate an ultrasensitive single molecule detection assay based on dual-color fluorescent colocalization of spilt aptamers that was implemented to the measurement of adenosine triphosphate (ATP)...
July 13, 2018: Analytical Chemistry
Yenleng Pak, Sang Jun Park, Qingling Xu, Hwan Myung Kim, Juyoung Yoon
The ratiometric fluorescent probe B6S, which contains pyrene as a fluorophore and imidazoline-2-thione as a reactive site, was developed for detection of hypochlorite (OCl-). B6S displays a high specificity toward OCl- in contrast to other ROS and RNS. The probe has a low detection limit and operates under biological conditions. Moreover, the low cytotoxicity of B6S enables it to be utilized effectively for OCl- imaging in living cells and tissues by using two-photon microscopy. The findings indicate that B6S has the capability of serving as a probe to explore the biological functions of OCl- in living system...
July 13, 2018: Analytical Chemistry
Nan Xiang, Xin Shi, Yu Han, Zhiguo Shi, Fengtao Jiang, Zhonghua Ni
Low-cost, easy-to-use cell concentration tools are in urgent demand for biomedical diagnosis in resource-poor settings. Herein, we propose a novel inertial microfluidic syringe cell (IMSC) concentrator that employs inertial focusing to increase cell concentration through ordering the cell and removing the cell-free fluid. A three-part structure, consisting of a cap-shaped upper housing, a circular gasket and a lower housing with a spiral channel, is adopted for simple fabricating and assembling, which enables the seamless translation of our IMSC concentrator into commercial outcomes without additional redesigning...
July 12, 2018: Analytical Chemistry
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