Classes Of Analytes Research Articles

A study of the methylene/perfluormethylene selectivity of porous polymer monolithic stationary phases exhibiting different fluorous/hydrophobic content

Porous polymer monolithic columns are prepared from a variety of monomers and cross-linkers and can be customized to exhibit different selectivities for separate analyte classes. The composition of the monolith can be precisely controlled by selecting different monomers and or cross-linker ratios. In this work monoliths exhibiting both fluorous and hydrophobic character were prepared using butyl methacrylate and its fluorous analogue (monomer) and 1,3-butanediol diacrylate and its fluorous analogue (cross-linker) in different ratios. The selectivity of the monoliths was probed using capillary electrochromatography with several fluorous and alkyl benzene analytes. Hydrophobic stationary phases exhibited greater methylene selectivity (α−CH2−) while those with increasing fluorous character show enhanced pefluoromethylene selectivity (α−CF2−). The Gibbs free energy change associated with the sorption of the analytes on each stationary phase composition can be calculated from migration times (i.e. capacity factor) for the addition of an individual −CF2− or −CH2− moiety. Furthermore, the Gibbs free energy change associated with a single −CF2− or −CH2− moiety (analyte) interacting with an individual −CF2− or −CH2− (stationary phase) can also be estimated by plotting fluorous column composition against ΔG−CH2−⁡or CF2−0. Furthermore ΔG−CH2−0 and ΔG−CF2−0 can be plotted versus H2O percentage in mobile phase, and a new concept, hypothetical water percentage (HWP) is proposed to evaluate the hydrophobicity/fluorophilicity of a stationary phase.

Nanostructured weathering steel for matrix-free laser desorption ionisation mass spectrometry and imaging of metabolites, drugs and complex glycans.

Weathering steel has been employed for the first time to prepare sample plates for matrix-free laser desorption ionisation mass spectrometry (LDI-MS) of small molecules up to a mass range of around 1500 Da. The effective UV absorption, heat conductivity and porosity of the nanostructured inner rust layer formed during passivation determine the excellent performance in LDI-MS for a broad range of different analyte classes. The inexpensive material was evaluated in a series of relevant analytical applications ranging from the matrix-free detection of serum metabolites, lactose quantification, lipid analysis in milk to the glycoprofiling of antibodies and imaging mass spectrometry of brain tissue samples.

Initial coefficient bounds for a subclass of $m$-fold symmetric bi-univalent functions

Let $\Sigma$ denote the class of functions $$f(z)=z+\sum_{n=2}^{\infty}a_nz^n$$ belonging to the normalized analytic function class $\mathcal{A}$ in the open unit disk $\mathbb{U}$, which are bi-univalent in $\mathbb{U}$, that is, both the function $f$ and its inverse $f^{-1}$ are univalent in $\mathbb{U}$. The usual method for computation of the coefficients of the inverse function $f^{-1}(z)$ by means of the relation $f^{-1}\big(f(z)\big)=z$ is too difficult to apply in the case of $m$-fold symmetric analytic functions in $\mathbb{U}$. Here, in our present investigation, we aim at overcoming this difficulty by using a general formula to compute the coefficients of $f^{-1}(z)$ in conjunction with the residue calculus. As an application, we introduce two new subclasses of the bi-univalent function class $\Sigma$ in which both $f(z)$ and $f^{-1}(z)$ are $m$-fold symmetric analytic functions with their derivatives in the class $\mathcal{P}$ of analytic functions with positive real part in $\mathbb{U}$. For functions in each of the subclasses introduced in this paper, we obtain the coefficient bounds for $|a_{m+1}|$ and $|a_{2m+1}|$.

The arithmetic Grothendieck-Riemann-Roch theorem for general projective morphisms

In this paper we generalize the arithmetic Grothendieck-Riemann- Roch Theorem to projective morphisms between arithmetic varieties that are not necessarily smooth over the complex numbers. The main ingredient is the theory of generalized holomorphic analytic torsion classes.

On codimension one foliations with prescribed cuspidal separatrix

In this paper, we will construct a pre-normal form for germs of codimension one holomorphic foliation having a particular type of separatrix, of cuspidal type. As an application, we will explain how this form could be used in order to study the analytic classification of the singularities via the projective holonomy, in the generalized surface case. We will also give an application to the analytic classification of singularities, and a sufficient condition, in the quasi-homogeneous, three-dimensional case, for these foliations to be of generalized surface type.

Novel liquid chromatography–mass spectrometry method shows that vitamin E deficiency depletes arachidonic and docosahexaenoic acids in zebrafish (Danio rerio) embryos

To test the hypothesis that embryogenesis depends upon α-tocopherol (E) to protect embryo polyunsaturated fatty acids (PUFAs) from lipid peroxidation, new methodologies were applied to measure α-tocopherol and fatty acids in extracts from saponified zebrafish embryos. A solid phase extraction method was developed to separate the analyte classes, using a mixed mode cartridge (reverse phase, π–π bonding, strong anion exchange), then α-tocopherol and cholesterol were measured using standard techniques, while the fatty acids were quantitated using a novel, reverse phase liquid chromatography–mass spectrometry (LC–MS) approach. We also determined if α-tocopherol status alters embryonic lipid peroxidation products by analyzing 24 different oxidized products of arachidonic or docosahexaenoic (DHA) acids in embryos using LC with hybrid quadrupole-time of flight MS. Adult zebrafish were fed E− or E+ diets for 4 months, and then were spawned to obtain E− and E+ embryos. Between 24 and 72 hours post-fertilization (hpf), arachidonic acid decreased 3-times faster in E− (21pg/h) compared with E+ embryos (7pg/h, P<0.0001), while both α-tocopherol and DHA concentrations decreased only in E− embryos. At 36hpf, E− embryos contained double the 5-hydroxy-eicosatetraenoic acids and 7-hydroxy-DHA concentrations, while other hydroxy-lipids remained unchanged. Vitamin E deficiency during embryogenesis depleted DHA and arachidonic acid, and increased hydroxy-fatty acids derived from these PUFA, suggesting that α-tocopherol is necessary to protect these critical fatty acids.

Chemical and technical challenges in the analysis of central carbon metabolites by liquid-chromatography mass spectrometry

This review deals with chemical and technical challenges in the analysis of small-molecule metabolites involved in central carbon and energy metabolism via liquid-chromatography mass-spectrometry (LC-MS). The covered analytes belong to the prominent pathways in biochemical carbon oxidation such as glycolysis or the tricarboxylic acid cycle and, for the most part, share unfavorable properties such as a high polarity, chemical instability or metal-affinity. The topic is introduced by selected examples on successful applications of metabolomics in the clinic. In the core part of the paper, the structural features of important analyte classes such as nucleotides, coenzyme A thioesters or carboxylic acids are linked to "problematic hotspots" along the analytical chain (sample preparation and-storage, separation and detection). We discuss these hotspots from a chemical point of view, covering issues such as analyte degradation or interactions with metals and other matrix components. Based on this understanding we propose solutions wherever available. A major notion derived from these considerations is that comprehensive carbon metabolomics inevitably requires multiple, complementary analytical approaches covering different chemical classes of metabolites.

Voltage-step pulsed electromembrane as a novel view of electrical field-induced liquid-phase microextraction

In the present work, the effect of application of voltage steps on extraction efficiency of pulsed electromembrane extraction (PEME) was investigated for the first time. The effects of voltage variations including initial and final voltages, number of steps between the initial and final voltages as well as their time durations were studied on the extraction efficiencies of three different classes of analytes. These classes include amitriptyline (AMI) and nortriptyline (NOR) as more hydrophobic analytes, diclofenac (DIC) and mefenamic acid (MEF) as acidic drugs and salbutamol (SB) and terbutaline (TB) as hydrophilic compounds. It was anticipated that the application of high voltages is not necessary at the beginning of the extraction, since large amounts of target analytes exist around the supported liquid membrane (SLM)/sample solution interface. So, they could be easily transferred into the acceptor phase utilizing lower voltages. Results showed that the benefits of voltage-step PEME (VS-PEME) are more obvious in systems with low electrical resistance (regarding the SLM composition). Efficiencies of VS-PEME for extraction of AMI and NOR (96% and 89% for AMI and NOR, respectively) were comparable with those achieved from applying a constant voltage (95% for AMI and 83% for NOR). However, recoveries from the VS-PEME of DIC and MEF (53% and 44% for DIC and MEF, respectively) were significantly higher than those from the application of a constant voltage (33% for DIC and 31% for MEF). Also, recoveries obtained from the VS-PEME for SB and TB were approximately 3 orders of magnitude greater than those from a constant voltage. Moreover, it was demonstrated that in all cases analytes could effectively be extracted at the beginning of extraction by applying low voltages.

Two birds with one stone: Doing metabolomics with your proteomics kit

Proteomic research facilities and laboratories are facing increasing demands for the integration of biological data from multiple ‘-OMICS’ approaches. The aim to fully understand biological processes requires the integrated study of genomes, proteomes and metabolomes. While genomic and proteomic workflows are different, the study of the metabolome overlaps significantly with the latter, both in instrumentation and methodology. However, chemical diversity complicates an easy and direct access to the metabolome by mass spectrometry (MS). The present review provides an introduction into metabolomics workflows from the viewpoint of proteomic researchers. We compare the physicochemical properties of proteins and peptides with metabolites/small molecules to establish principle differences between these analyte classes based on human data. We highlight the implications this may have on sample preparation, separation, ionisation, detection and data analysis. We argue that a typical proteomic workflow (nLC-MS) can be exploited for the detection of a number of aliphatic and aromatic metabolites, including fatty acids, lipids, prostaglandins, di/tripeptides, steroids and vitamins, thereby providing a straightforward entry point for metabolomics-based studies. Limitations and requirements are discussed as well as extensions to the LC-MS workflow to expand the range of detectable molecular classes without investing in dedicated instrumentation such as GC-MS, CE-MS or NMR.

Life quality and health in adolescents and emerging adults with epilepsy during the years of transition: a scoping review

The aims of this study were to (1) search the literature in order to identify the challenges facing adolescents and emerging adults with epilepsy; and (2) categorize these issues within both the framework of the International Classification of Functioning, Disability and Health (ICF) and an empirical model of quality of life (QOL) in childhood epilepsy. We systematically searched PsycINFO, Ovid MEDLINE and Web of Science for studies reporting on QOL and health identified in people with epilepsy aged 12 to 29years. Studies were limited to those that were published in the last 20years in English, presenting the patient perspective. Data were extracted and charted using a descriptive analytical method. Identified issues were classified according to the ICF and QOL frameworks. Fifty four studies were identified. Another 62 studies with potentially useful information were included as an addendum. The studies highlight a range of psychosocial issues emphasizing peer acceptance, social isolation, and feelings of anxiety, fear, and sadness. The ICF and QOL constructs represent useful starting points in the analytical classification of the potential challenges faced by adolescents with epilepsy. Progress is needed on fully classifying issues not included under these frameworks. We propose to expand these frameworks to include comorbidities, impending medical interventions, and concerns for future education, employment, marriage, dignity, and autonomy.

Subpicogram Per Milliliter Detection of Interleukins Using Silicon Photonic Microring Resonators and an Enzymatic Signal Enhancement Strategy

The detection of biomolecules at ultralow (low to subpicogram per milliliter) concentrations and within complex, clinically relevant matrices is a formidable challenge that is complicated by limitations imposed by the Langmuir binding isotherm and mass transport, for surface-based affinity biosensors. Here we report the integration of an enzymatic signal enhancement scheme onto a multiplexable silicon photonic microring resonator detection platform. To demonstrate the analytical value of this combination, we simultaneously quantitated levels of the interleukins IL-2, IL-6, and IL-8 in undiluted cerebrospinal fluid in an assay format that is multiplexable, relatively rapid (90 min), and features a 3 order of magnitude dynamic range and a limit of detection ≤1 pg/mL. The modular nature of this assay and technology should lend itself broadly amenable to different analyte classes, making it a versatile tool for biomarker analysis in clinically relevant settings.

Capillary Electrophoresis Analysis of Conventional Splicing Assays: IARC Analytical and Clinical Classification of 31BRCA2Genetic Variants

Rare sequence variants in "high-risk" disease genes, often referred as unclassified variants (UVs), pose a serious challenge to genetic testing. However, UVs resulting in splicing alterations can be readily assessed by in vitro assays. Unfortunately, analytical and clinical interpretation of these assays is often challenging. Here, we explore this issue by conducting splicing assays in 31 BRCA2 genetic variants. All variants were assessed by RT-PCR followed by capillary electrophoresis and direct sequencing. If assays did not produce clear-cut outputs (Class-2 or Class-5 according to analytical International Agency for Research on Cancer guidelines), we performed qPCR and/or minigene assays. The latter were performed with a new splicing vector (pSAD) developed by authors of the present manuscript (patent #P201231427 CSIC). We have identified three clinically relevant Class-5 variants (c.682-2A>G, c.7617+1G>A, and c.8954-5A>G), and 27 analytical Class-2 variants (not inducing splicing alterations). In addition, we demonstrate that rs9534262 (c.7806-14T>C) is a BRCA2 splicing quantitative trait locus.

The discrimination of interaural level difference sensitivity functions: development of a taxonomic data template for modelling

BackgroundA major cue for the position of a high-frequency sound source in azimuth is the difference in sound pressure levels in the two ears, Interaural Level Differences (ILDs), as a sound is presented from different positions around the head. This study aims to use data classification techniques to build a descriptive model of electro-physiologically determined neuronal sensitivity functions for ILDs. The ILDs were recorded from neurons in the central nucleus of the Inferior Colliculus (ICc), an obligatory midbrain auditory relay nucleus. The majority of ICc neurons (~ 85%) show sensitivity to ILDs but with a variety of different forms that are often difficult to unambiguously separate into different information-bearing types. Thus, this division is often based on laboratory-specific and relatively subjective criteria. Given the subjectivity and non-uniformity of ILD classification methods in use, we examined if objective data classification techniques for this purpose. Our key objectives were to determine if we could find an analytical method (A) to validate the presence of four typical ILD sensitivity functions as is commonly assumed in the field, and (B) whether this method produced classifications that mapped on to the physiologically observed results.MethodsThe three-step data classification procedure forms the basic methodology of this manuscript. In this three-step procedure, several data normalization techniques were first tested to select a suitable normalization technique to our data. This was then followed by PCA to reduce data dimensionality without losing the core characteristics of the data. Finally Cluster Analysis technique was applied to determine the number of clustered data with the aid of the CCC and Inconsistency Coefficient values.ResultsThe outcome of a three-step analytical data classification process was the identification of seven distinctive forms of ILD functions. These seven ILD function classes were found to map to the four “known” ideal ILD sensitivity function types, namely: Sigmoidal-EI, Sigmoidal-IE, Peaked, and Insensitive, ILD functions, and variations within these classes. This indicates that these seven templates can be utilized in future modelling studies.ConclusionsWe developed a taxonomy of ILD sensitivity functions using a methodological data classification approach. The number and types of generic ILD function patterns found with this method mapped well on to our electrophysiologically determined ILD sensitivity functions. While a larger data set of the latter functions may bring a more robust outcome, this good mapping is encouraging in providing a principled method for classifying such data sets, and could be well extended to other such neuronal sensitivity functions, such as contrast tuning in vision.

A new strategy to eliminate sample mixing during in-tube solid phase microextraction

During in-tube solid phase microextraction, sample mixing with mobile phase contained in the autosampler tubing during extraction may result in some amount of sample becoming entrained in the mobile phase rather than returning to the sample vial or being directed to waste after extraction. In cases where target analytes have relatively low affinity for the sorbent on the wall of the capillary, mixing can impact data quality. Where the sample contains components that may interfere with either the separation (e.g. proteins) or detection (e.g. ions with MS detection), additional difficulties can arise. In the current research, the magnitude of the sample mixing effect was illustrated by analyzing ranitidine and a series of polycyclic aromatic hydrocarbons (PAH). The sample volume equivalent of mixing was calculated as 37μL for ranitidine and 20μL for PAHs using the same inner diameter of capillary. To address this issue, a novel approach involving adding a switching valve located between the metering pump and the capillary was developed. Capillary flush conditions, draw/eject speed and extraction time were optimized for ranitidine with the result that in the final method, no mixing of sample with mobile phase was apparent in the detected amounts. To provide information on a compound class with intermediate polarity, two β-blockers were also extracted using the optimized washing conditions respectively. The results indicated that the issue of sample mixing had been resolved for these as well. Finally, in-tube SPME calibration of these three analyte classes was shown to be highly linear, providing further indication that sample mixing was not impacting data quality. Available literature on the subject was surveyed, and a discussion on the rational selection of conditions to guide method development was also provided.

Topological and analytical classification of vector fields with only isochronous centres

We study vector fields on the plane having only isochronous centres. The most familiar examples are isochronous vector fields, they are the real parts of complex polynomial vector fields on having all their zeroes of centre type. We describe the number of topologically inequivalent isochronous (singular) foliations that can appear for degree s, up to orientation preserving homeomorphisms. For each s, there exists a real analytic variety parametrizing the isochronous vector fields of degree s, the group of complex automorphisms of the plane acts on it. Furthermore, if , then is a non-singular real analytic variety of dimension , and their number of connected components is bounded by . An explicit formula for the residues of the rational 1-form, canonically associated with a complex polynomial vector field with simple zeroes, is given. A collection of residues (i.e. periods) does not characterize an isochronous vector field, even up to complex automorphisms of . An exact bound for the number of isochronous vector fields, up to , having the same collection of residues (periods) is given. We develop several descriptions of the quotient space using residues, weighted s-trees and singular flat Riemannian metrics associated with isochronous vector fields.

Supergravity solutions of two M2 branes

We present an exact analytic class of solutions for a system of two membranes in eleven-dimensional supergravity. One brane in the system is completely localized along the overall and relative transverse coordinates while the other brane in the system is localized only along the overall transverse coordinates. The membrane configuration preserves four supersymmetries. Moreover we find some approximate solutions for the system of two membranes with a Bianchi space as the overall transverse space to both membranes. All supergravity solutions preserve 1/8 of the supersymmetry. Upon dimensional reduction, the solutions provide intersecting configurations of three D-branes in type IIA supergravity.

4-Phenyl-α-cyanocinnamic Acid Amide: Screening for a Negative Ion Matrix for MALDI-MS Imaging of Multiple Lipid Classes

Matrix-assisted laser desorption/ionization imaging mass spectrometry (MALDI-IMS) has become a method of choice in lipid analysis, as it provides localization information for defined lipids that is not readily accessible with nonmass spectrometric methods. Most current MALDI matrices have been found empirically. Nevertheless, preferential matrix properties for many analyte classes are poorly understood and may differ between lipid classes. We used rational matrix design and semiautomated screening for the discovery of new matrices suitable for MALDI-IMS of lipids. Utilizing Smartbeam- and nitrogen lasers for MALDI, we systematically compared doubly substituted α-cyanocinnamic acid derivatives (R(1)-CCA-R(2)) with respect to their ability to serve as negative ion matrix for various brain lipids. We identified 4-phenyl-α-cyanocinnamic acid amide (Ph-CCA-NH2) as a novel negative ion matrix that enables analysis and imaging of various lipid classes by MALDI-MS. We demonstrate that Ph-CCA-NH2 displays superior sensitivity and reproducibility compared to matrices commonly employed for lipids. A relatively small number of background peaks and good matrix suppression effect could make Ph-CCA-NH2 a widely applicable tool for lipid analysis.

Inkjet-Printed Paper-Based Colorimetric Sensor Array for the Discrimination of Volatile Primary Amines

This paper describes a colorimetric sensor array for the discrimination of volatile amines. Analyte discrimination is achieved by combining two functional elements: (1) a "chemical class-selective" single chromogenic sensing dye with selectivity for amines in general, encapsulated into (2) polymer nanoparticles with different polarities. The resulting array has the ability to distinguish one closely related amine from another, relying on a polarity-based approach. In order to achieve reproducible, cost efficient, and flexible sensor array fabrication with the potential for mass production, inkjet-printing technology combined with standard copy paper as a sensor substrate is applied. Printing of 6 types of inks, which are prepared by mixing two dye encapsulating nanoparticles of different polarity in different mixture ratios, results in a colorimetric sensor array with a polarity gradient. Seven primary amines with increasing alkyl chain lengths have been selected to demonstrate the performance of the sensor array. The RGB color differences (ΔR, ΔG, ΔB) of the sensor array spots before and after gas exposure were analyzed by principal component analysis (PCA) and agglomerative hierarchical clustering (AHC) analysis. Under the selected measurement conditions, results of PCA and AHC analysis indicated high discrimination ability with high reproducibility of the sensor array down to amine concentrations of 50 ppm. The discrimination ability was maintained at relative humidities between 10% and 80%. Furthermore, the sensor array showed no significant response to common volatile organic compounds, confirming the high selectivity toward amines. This is, to the best of our knowledge, the first report of a colorimetric sensor array with selectivity for a specific chemical class of analytes and the ability to discriminate compounds of the same class, which is obtained by simply mixing two types of single dye-encapsulating polymer nanoparticles.

On the subfields of cyclotomic function fields

Let $K = \mathbb {F}_q(T)$ be the rational function field over a finite field of $q$ elements. For any polynomial $f(T)\in \mathbb {F}_q[T]$ with positive degree, denote by $\Lambda _f$ the torsion points of the Carlitz module for the polynomial ring $\mathbb {F}_q[T]$. In this short paper, we will determine an explicit formula for the analytic class number for the unique subfield $M$ of the cyclotomic function field $K(\Lambda _P)$ of degree $k$ over $\mathbb {F}_q(T)$, where $P\in \mathbb {F}_q[T]$ is an irreducible polynomial of positive degree and $k>1$ is a positive divisor of $q-1$. A formula for the analytic class number for the maximal real subfield $M^+$ of $M$ is also presented. Futhermore, a relative class number formula for ideal class group of $M$ will be given in terms of Artin $L$-function in this paper.

Qualitative Identification of Carboxylic Acids, Boronic Acids, and Amines Using Cruciform Fluorophores

Molecular cruciforms are X-shaped systems in which two conjugation axes intersect at a central core. If one axis of these molecules is substituted with electron-donors, and the other with electron-acceptors, cruciforms' HOMO will localize along the electron-rich and LUMO along the electron-poor axis. This spatial isolation of cruciforms' frontier molecular orbitals (FMOs) is essential to their use as sensors, since analyte binding to the cruciform invariably changes its HOMO-LUMO gap and the associated optical properties. Using this principle, Bunz and Miljanić groups developed 1,4-distyryl-2,5-bis(arylethynyl)benzene and benzobisoxazole cruciforms, respectively, which act as fluorescent sensors for metal ions, carboxylic acids, boronic acids, phenols, amines, and anions. The emission colors observed when these cruciform are mixed with analytes are highly sensitive to the details of analyte's structure and - because of cruciforms' charge-separated excited states - to the solvent in which emission is observed. Structurally closely related species can be qualitatively distinguished within several analyte classes: (a) carboxylic acids; (b) boronic acids, and (c) metals. Using a hybrid sensing system composed from benzobisoxazole cruciforms and boronic acid additives, we were also able to discern among structurally similar: (d) small organic and inorganic anions, (e) amines, and (f) phenols. The method used for this qualitative distinction is exceedingly simple. Dilute solutions (typically 10(-6) M) of cruciforms in several off-the-shelf solvents are placed in UV/Vis vials. Then, analytes of interest are added, either directly as solids or in concentrated solution. Fluorescence changes occur virtually instantaneously and can be recorded through standard digital photography using a semi-professional digital camera in a dark room. With minimal graphic manipulation, representative cut-outs of emission color photographs can be arranged into panels which permit quick naked-eye distinction among analytes. For quantification purposes, Red/Green/Blue values can be extracted from these photographs and the obtained numeric data can be statistically processed.