Retention characteristics of protonated mobile phases injected into deuterated mobile phases in capillary liquid chromatography (LC) using on-line nuclear magnetic resonance (NMR) detection

The behavior of protonated binary solvents injected into deuterated binary mobile phases in capillary LC is studied with NMR. Specifically, the solvent elution is followed on-flow with a capillary LC coupled to a 900 nL volume microcoil NMR probe. A range of identical composition 5% protonated (and 95% deuterated) solvents is injected into composition-matched deuterated mobile phases of CD(3)CN/D(2)O and CD(3)OD/D(2)O. The protonated components separate for all solvent combinations except at 80% CD(3)CN/20% D(2)O and similar to 72% CD(3)OD/28% D(2)O where only a single retention time is observed. The more hydrophilic protonated component, HOD, elutes first with higher percentages of hydrophilic solvent, D(2)O, in the mobile phase whereas retention is reversed with the higher percentage of the more hydrophobic solvent (CD(3)CN and CD(3)OD) in the mobile phase. The hydrophilic/hydrophobic nature of the chromatographic system as a function of mobile phase composition is characterized by following the retention times of protonated solvents.     

Measuring D-amino acid-containing neuropeptides with capillary electrophoresis

Neuropeptides are heavily posttranslationally modified (PTM) gene products that are often characterized by a variety of mass spectrometric approaches. Recently, the occurrence of amino acids in the D-form has been documented in several neuropeptides. As this modification has no associated mass shift, this particular PTM is difficult to evaluate using mass spectrometry (MS) alone. Here we demonstrate several approaches using capillary electrophoresis (CE) with absorbance and laser-induced fluorescence (LIF) for the separation of native and derivatized molluscan peptides containing D-amino acids. The combination of peptide derivatization followed by CE/LIF is well suited for single cell measurements because of its ability to characterize the peptides in such small samples. In order to verify this approach, the D-Trp-containing peptide NdWFa (NH2-Asn-D-Trp-Phe-CONH2), present in individual neurons from the marine mollusk Aplysia californica, has been characterized. The mass spectra show that NdWFa and/or NWFa are present in specific neurons; CE/LIF analysis of these cells demonstrates that NdWFa is the dominant form of the peptide.     

A one‐step matrix application method for MALDI mass spectrometry imaging of bacterial colony biofilms

Matrix‐assisted laser desorption/ionization imaging of biofilms cultured on agar plates is challenging because of problems related to matrix deposition onto agar. We describe a one‐step, spray‐based application of a 2,5‐dihydroxybenzoic acid solution for direct matrix‐assisted laser desorption/ionization imaging of hydrated Bacillus subtilis biofilms on agar. Using both an optimized airbrush and a home‐built automatic sprayer, region‐specific distributions of signaling metabolites and cannibalistic factors were visualized from B. subtilis cells cultivated on biofilm‐promoting medium. The approach provides a homogeneous, relatively dry coating on hydrated samples, improving spot to spot signal repeatability compared with sieved matrix application, and is easily adapted for imaging a range of agar‐based biofilms. Copyright © 2016 John Wiley & Sons, Ltd.     

Contributions of capillary electrophoresis to neuroscience

Capillary electrophoresis (CE) is a small-volume separation approach amenable to the analysis of complex samples for their small molecule, peptide and protein content. A number of the features of CE make it a method of choice for addressing questions related to neurochemistry. The figures of merit inherent to CE that make it well suited for studying cell-to-cell and intracellular signaling include small sample volumes, high separation efficiency, the ability for online analyte concentration, and compatibility with sensitive and high-information content detection methods. A variety of instrumental aspects are detailed, including detection methods and sampling techniques that are particularly useful for the analysis of signaling molecules. Studies that have used these techniques to increase our understanding of neurobiology are emphasized throughout. One notable application is single neuron chemical analysis, a research area that has been greatly advanced by CE.     

Confirmation of peak assignments in capillary electrophoresis using immunoprecipitation. Application to D-aspartate measurements in neurons

Capillary electrophoresis (CE) with laser-induced fluorescence (LIF) detection is a powerful tool for analysis of samples ranging from tissue extracts to single cells. However, accurate peak identification in electropherograms is challenging when complex biological samples are analyzed, as often matching a migration time between an analyte and corresponding standard may be insufficient to confirm the peak's identity. A method which combines single-step immunoprecipitation and CE-LIF analysis for investigation of the chiral amino acids in single cells and small tissue samples is demonstrated. D-Aspartate (D-Asp) has been reported in the central nervous system of the invertebrate neurobiological model Aplysia californica. In order to confirm the identity of D-Asp signal in the complex electropherograms of nerve tissue extracts and individual neurons, anti-D-Asp serum, preincubated with L-Asp conjugate, is added to the sample. This selectively binds the free D-Asp, creating an antibody-antigen complex with a migration time similar to that of antibody alone, but not that of D-Asp. The complete disappearance of the putative D-Asp peak confirms its identity and validates that there are no other detectable analytes co-migrating with D-Asp in the electropherogram.     

Capillary electrophoresis of ultrasmall carboxylate functionalized silicon nanoparticles

Capillary electrophoresis is used to separate ultrasmall ( approximately 1 nm) carboxylate functionalized Si nanoparticles (Si-np-COO(-)) prepared via hydrosilylation with an omega-ester 1-alkene. The electropherograms show a monodisperse Si core size with one or two carboxylate groups added to the surface. On-column detection of their laser-induced fluorescence demonstrates that the individual Si-np-COO(-) have narrow emissions (full width at half maximum = 30-40 nm) with a nearly symmetric lineshape. Preparative scale electrophoresis should be a viable route for purification of the Si-np-COO(-) for further study and future applications.     

Assaying neurotransmitters in and around single neurons with information-rich detectors

Techniques to study the chemical environment in and around individual neurons are reviewed, with an emphasis on methods to assay single cells for neurotransmitters and neuromodulators that do not require analyte preselection. Current capabilities of capillary-based microseparations and mass spectrometry are highlighted for this application. Methods to combine multiple analytical techniques to provide chemical, spatial and temporal information are described.     

MALDI Mass Spectrometry Imaging of Neuronal Cell Cultures

Mass spectrometry imaging (MSI) provides the ability to detect and identify a broad range of analytes and their spatial distributions from a variety of sample types, including tissue sections. Here we describe an approach for probing neuropeptides from sparse cell cultures using matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) MSI—at single cell spatial resolution—in both MS and tandem MS modes. Cultures of Aplysia californica neurons are grown on an array of glass beads embedded in a stretchable layer of Parafilm M. As the membrane is stretched, the beads/neurons are separated physically and the separated beads/neurons analyzed via MALDI TOF MS. Compared with direct MS imaging of samples, the stretching procedure enhances analyte extraction and incorporation into the MALDI matrix, with negligible analyte spread between separated beads. MALDI tandem MSI using the stretched imaging approach yields localization maps of both parent and fragment ions from Aplysia pedal peptide, thereby confirming peptide identification. This methodology represents a flexible platform for MSI investigation of a variety of cell cultures, including functioning neuronal networks.     

地方高校化工专业学生创新创业能力提升模式探索

针对当前地方高校化工类专业创新创业人才供需现状,结合地方高校实际,提出了化工专业学生虚拟公司设计实训、校内仿真实训、校内外实践基地一体化创新创业能力提升实践教学模式,具有"内外结合、虚实结合、阶梯式推进"等特色。经探索,采用该模式可走出一条具有地方高校特色的实践教学新路径,可形成工科专业实践教学的示范模式,对于提升地方高校的竞争力具有积极意义。     

铁的析氢腐蚀实验探究

针对析氢腐蚀实验中出现的异常现象,依据金属电化学腐蚀原理,通过实验探究确定影响析氢腐蚀实验的主要因素——氧气。在此基础之上,设计出演示吸氧腐蚀、析氢腐蚀的套管实验以及析氢腐蚀的微型化实验方案。