Analysis of therapeutic peptides in human urine by combination of capillary zone electrophoresis-electrospray mass spectrometry with preparative capillary isotachophoresis sample pretreatment

The presented study deals with the off-line coupling of preparative isotachophoresis (pITP) with on-line combination of capillary zone electrophoresis with electrospray mass spectrometric detection (CZE-ESI-MS) used for the analysis of therapeutic peptides (anserine, carnosine, and buserelin) in complex matrix (urine). Preparative capillary isotachophoresis, operating in a discontinuous fractionation mode in column-coupling configuration, served as a sample pretreatment technique to separation, and fractionation of mixture of therapeutic peptides present in urine at low concentration level. The fractions isolated by pITP procedure were subsequently analyzed by capillary zone electrophoresis with electrospray mass spectrometric detection. Acetic acid at 200 mmol L(-1) concentration served as background electrolyte in CZE stage and it is compatible with MS detection in positive ionization mode. In pITP fractionation procedure, sodium cation (10 mmol L(-1) concentration) as leading ion and beta-alanine as terminating ion (20 mmol L(-1) concentration) were used. While using CZE-ESI-MS, the limits of detection were 0.18 μg mL(-1) for carnosine, 0.17 μg mL(-1) for anserine and 0.64 μg mL(-1) for buserelin in water and 0.19 μg mL(-1) for carnosine, 0.50 μg mL(-1) for anserine and 0.74 μg mL(-1) for buserelin in 10 times diluted urine, respectively. The cleaning power of pITP sample pretreatment was proved as the peptides provided the higher MS signals at lower concentration levels resulting from the minimized matrix effects. The quality of obtained MS/MS spectra was very good so that they can provide information about the structure of analytes, and they were used for verification of the analytes identities. The pITP pretreatment improved the detection limits of the analyzed therapeutic peptides at least 25 times compared to the CZE-ESI-MS itself.     

Synthesis of (E)-2-(1-ferrocenylmethylidene)malonic acid derivatives by a cobalt-catalyzed domino reaction of ethyl diazoacetate, carbon monoxide and ferrocenylimines

The domino reaction of ethyl diazoacetate, carbon monoxide and ferrocenylimines was investigated in the presence of Co₂(CO)₈ as catalyst. In most cases the main products are 2-(1-ferrocenylmethylidene) malonates formed by an N(1)-C(4) cleavage of the primarily derived β-lactams. The latter compounds could only be isolated when the reaction was carried out at relatively low CO pressure, using an excess of ethyl diazoacetate. trans-N-(tert-Butyl)-3-ethoxycarbonyl-4-ferrocenyl-β-lactam proved to be the most stable one among these compounds and could be isolated in 55% yield. N-alkyl β-lactams were shown to undergo acidic cleavage leading to the E isomers of 2-(1-ferrocenylmethylidene) malonates as the main products. The structures of the two new compounds, (E)-2-ethoxycarbonyl-3-ferrocenyl-N-((R)-1-phenylethyl)-2-propenamide and trans-N-(tert-butyl)-3-ethoxycarbonyl-4-ferrocenyl-β-lactam were confirmed by X-ray crystallography. The relative thermodynamical stability of the products as well as the energetics of the acid-mediated cleavage of the β-lactam ring was elucidated with DFT calculations.     

Preparation and examination of multilayer graphene nanosheets by exfoliation of graphite in high efficient attritor mill

Graphene multilayers have been prepared by mechanical method based on milling graphite in high efficient attritor mill. The results showed that the best dispersion media is ethanol, and 10 hours of intensive milling proved to be the most efficient way to separate the graphite layers as it was shown by scanning electron microscopy and X-ray diffraction measurements.      

ℓ1-summability of higher-dimensional Fourier series

It is proved that the maximal operator of the ${?}_1$-Fejér means of a $d$-dimensional Fourier series is bounded from the periodic Hardy space $H_p\left({\mathbb{T}}^d\right)$ to $L_p\left({\mathbb{T}}^d\right)$ for all $d/(d+1)<p\le \infty$ and, consequently, is of weak type (1, 1). As a consequence we obtain that the ${?}_1$-Fejér means of a function $f\in L_1\left({\mathbb{T}}^d\right)$ converge a.e. to $f$. Moreover, we prove that the ${?}_1$-Fejér means are uniformly bounded on the spaces $H_p\left({\mathbb{T}}^d\right)$ and so they converge in norm $(d/(d+1)<p<\infty )$. Similar results are shown for conjugate functions and for a general summability method, called $\theta$-summability. Some special cases of the ${?}_1–\theta$-summation are considered, such as the Weierstrass, Picard, Bessel, Fejér, de la Vallée Poussin, Rogosinski and Riesz summations.     

On 2-level secret sharing

In this paper, using recent results in finite geometry, we study a certain class of 2-level shared secret schemes. We shall present upper bounds on both the number of participants in total and on the number of participants in the lower level, which constitute the only nontrivial cases, and construct examples for the extremal cases.     

New practical synthesis of 5‐formylindole

5‐Formylindole ( 2 ) was synthesized in good overall yield starting from 3‐methyl‐4‐nitrobenzaldehyde ( 4 ) by utilization of the Batcho‐Leimgruber indole synthesis.     

Bounded continuously distributed delays in dynamic oligopolies

This paper introduces a way of modelling bounded continuously distributed time lags in dynamic economic models. Past data are averaged only over a bounded interval thus avoiding the use of very old (“stale”) economic data and hence making dynamic economic models more realistic. Dynamic oligopolies are formulated and then examined under this new type of information lag. Stability analysis is presented and the possibility of the birth of limit cycles is examined. Some special cases are considered, the computational analysis of which illustrates the theoretical findings.     

On a-Posteriori Error Estimate of Approximate Solutions to a Mildly Nonlinear Nonpotential Elliptic Boundary Value Problem

The paper deals with the construction of a computable a-posteriori error estimate of the approximate solution to some nonpotential nonlinear elliptic boundary value problems. The convergence of the presented error estimate to the true error is proved. The method is illustrated on some numerical examples.     

An inter-comparison of far-infrared line-by-line radiative transfer models

A considerable fraction (>40%) of the outgoing longwave radiation escapes from the Earth's atmosphere-surface system within a region of the spectrum known as the far-infrared (wave-numbers less than 650 cm⁻¹). Dominated by the line and continuum spectral features of the pure rotation band of water vapor, the far-infrared has a strong influence upon the radiative balance of the troposphere, and hence upon the climate of the Earth. Despite the importance of the far-infrared contribution, however, very few spectrally resolved observations have been made of the atmosphere for wave-numbers less than 650 cm⁻¹. The National Aeronautics and Space Administration (NASA), under its Instrument Incubator Program (IIP), is currently developing technology that will enable routine, space-based spectral measurements of the far-infrared. As part of NASA's IIP, the Far-Infrared Spectroscopy of the Troposphere (FIRST) project is developing an instrument that will have the capability of measuring the spectrum over the range from 100 to 1000 cm⁻¹ at a resolution of 0.6 cm⁻¹. To properly analyze the data from the FIRST instrument, accurate radiative transfer models will be required. Unlike the mid-infrared, however, no inter-comparison of codes has been performed for the far-infrared. Thus, in parallel with the development of the FIRST instrument, an investigation has been undertaken to inter-compare radiative transfer models for potential use in the analysis of far-infrared measurements. The initial phase of this investigation has focused upon the inter-comparison of six distinct line-by-line models. The results from this study have demonstrated remarkably good agreement among the models, with differences being of order 0.5%, thereby providing a high measure of confidence in our ability to accurately compute spectral radiances in the far-infrared.