Hydrophilic properties as a new contribution for computer-aided identification of short peptides in complex mixtures

A new method to predict elementary amino acid (AA) composition of peptides (molar mass <1,000 g/mol) is described. This procedure is based on a computer-aided method using three combined analyses-reversed phase liquid chromatography (RPLC), hydrophilic interaction chromatography (HILIC) and capillary electrophoresis coupled with mass spectrometry-and using a software calculating all possible amino acid combinations from the mass of any given peptide. The complementarity between HILIC and RPLC was demonstrated. Peptide retention prediction in HILIC was successfully modelled, and the achieved prediction accuracy was as high as r2=0.97. This mathematical model, based on amino acid retention contributions and peptide length, provided the information about peptide hydrophilicity that was not redundant with its hydrophobicity. Correlations between respectively the hydrophobicity coefficients and RPLC retention time, hydrophilicity and HILIC retention time, and electrophoretic mobility and migration time were used for ranking all potential AA combinations corresponding to the given mass. The essential contribution of HILIC in this identification strategy and the need to combine the three models to significantly increase identification capabilities were both shown. Applied to an 18-standard peptide mixture, the identification procedure enabled the actual AA combination determination of the 14 di- to pentapeptides, in addition to an over 98 % reduction of possible combination numbers for the four hexapeptides. This procedure was then applied to the identification of 24 unknown peptides in a rapeseed protein hydrolysate. The effective AA composition was found for ten peptides, whereas for the 14 other peptides, the number of possible combinations was reduced by over 95 % thanks to the association of the three analyses. Finally, as a result of the information provided by the analytical techniques about peptides present in the mixture, the proposed method could become a highly valuable tool to recover bioactive peptides from undefined protein hydrolysates.     

A new approach for the estimation of the melting enthalpy of metastable crystalline compounds using differential scanning calorimetry

This article focuses on the development of an innovative method, based on thermodynamic considerations and with the use of Differential Scanning Calorimetry (DSC), for the estimation of the melting enthalpy of crystalline compounds which are metastable near their melting temperature. The curves obtained, at various heating rates, are analysed in two steps. In the first step, the area of a zone generated by the melting endothermic peak is calculated following a specific method. In the second step, the melting enthalpy is extracted from this area through an enthalpy balance. This method is applied to both identified crystallographic forms, named form I and form II, respectively, of Etiracetam (UCB Pharma). The results show that the melting enthalpy of the stable form II compare well with the ones obtained using conventional methods. The curves of the metastable form I present thermal instabilities (partial solid–solid polymorphic transition and beta-recrystallization) near the form I melting peak leading to difficulties for a direct determination of the melting enthalpy by conventional methods. The proposed method is therefore very useful for the estimation of the form I melting enthalpy.     

Vapor hydration of SON68 glass from 90 °C to 200 °C: A kinetic study and corrosion products investigation

Corrosion of nuclear waste glass in unsaturated conditions is expected to occur upon the closure of the repository galleries during disposal cell saturation in the proposed French disposal site. The objectives of the present work were to determine the alteration kinetics of the SON68 reference in such conditions. Vapor hydration tests were conducted using thin, polished SON68 glass coupons contained in stainless steel autoclaves. Temperatures ranged between 90 °C and 200 °C and the relative humidity (RH) was maintained at 91 ± 1%. Additional experiments at 175 °C and 80, 85, 90 and 95% RH were also conducted to assess the role of RH on the glass corrosion rate. The nature and extent of corrosion have been determined by characterizing the reacted glass surface with scanning electron microscopy (SEM), transmission electron microscopy (TEM), and energy dispersive X-ray spectroscopy (EDS). Elemental profiling of the glass hydrated at 90 °C was studied by TOF-SIMS. The chemical composition of the external layer depends on experimental conditions. The hydration rate at 90 °C (TOF-SIMS analysis) is 10 × higher than the generally accepted final rate of SON68 in water at 90 °C (~ 10^? 4 g m^? 2 d^? 1). This may indicate that the glass hydration process cannot be simulated by experiments in aqueous solution with a high S/V ratio. Subsequent leaching (corrosion in an aqueous solution) of samples weathered in water vapor showed dissolution rate values higher than those of pristine glass. This result indicates that mobile elements are trapped within the alteration products during the hydration step and it gives insight into mobility variations of the considered elements.     

A constraint programming approach for a batch processing problem with non-identical job sizes

This paper presents a constraint programming approach for a batch processing machine on which a finite number of jobs of non-identical sizes must be scheduled. A parallel batch processing machine can process several jobs simultaneously and the objective is to minimize the maximal lateness. The constraint programming formulation proposed relies on the decomposition of the problem into finding an assignment of the jobs to the batches, and then minimizing the lateness of the batches on a single machine. This formulation is enhanced by a new optimization constraint which is based on a relaxed problem and applies cost-based domain filtering techniques. Experimental results demonstrate the efficiency of cost-based domain filtering techniques. Comparisons to other exact approaches clearly show the benefits of the proposed approach: it can optimally solve problems that are one order of magnitude greater than those solved by a mathematical formulation or by a branch-and-price.     

Use of a capillary electrophoresis instrument with laser-induced fluorescence detection for DNA quantitation. Comparison of YO-PRO-1 and PicoGreen assays

Highly selective and sensitive assays are required for detection and quantitation of the small masses of DNA typically encountered in clinical and forensic settings. High detection sensitivity is achieved using fluorescent labeling dyes and detection techniques such as spectrofluorometers, microplate readers and cytometers. This work describes the use of a laser-induced fluorescence (LIF) detector in conjunction with a commercial capillary electrophoresis instrument for DNA quantitation. PicoGreen and YO-PRO-1, two fluorescent DNA labeling dyes, were used to assess the potential of the system for routine DNA analysis. Linearity, reproducibility, sensitivity, limits of detection and quantitation, and sample stability were examined for the two assays. The LIF detector response was found to be linear (R2 > 0.999) and reproducible (RSD < 9%) in both cases. The PicoGreen assay displayed lower limits of detection and quantitation (20 pg and 60 pg, respectively) than the YO-PRO-1 assay (60 pg and 260 pg, respectively). Although a small variation in fluorescence was observed for the DNA/dye complexes over time, quantitation was not significantly affected and the solutions were found to be relatively stable for 80 min. The advantages of the technique include a 4- to 40-fold reduction in the volume of sample required compared to traditional assays, a 2- to 20-fold reduction in the volume of reagents consumed, fast and automated analysis, and low cost (no specific instrumentation required).     

Hybrid Bis-Histidine Phenanthroline-Based Ligands to Lessen Aβ-Bound Cu ROS Production: An Illustration of Cu(I) Significance

We here report the synthesis of three new hybrid ligands built around the phenanthroline scaffold and encompassing two histidine-like moieties: phenHH, phenHGH and H’phenH’, where H correspond to histidine and H’ to histamine. These ligands were designed to capture Cu(I/II) from the amyloid-β peptide and to prevent the formation of reactive oxygen species produced by amyloid-β bound copper in presence of physiological reductant (e.g., ascorbate) and dioxygen. The amyloid-β peptide is a well-known key player in Alzheimer’s disease, a debilitating and devasting neurological disorder the mankind has to fight against. The Cu-Aβ complex does participate in the oxidative stress observed in the disease, due to the redox ability of the Cu(I/II) ions. The complete characterization of the copper complexes made with phenHH, phenHGH and H’phenH’ is reported, along with the ability of ligands to remove Cu from Aβ, and to prevent the formation of reactive oxygen species catalyzed by Cu and Cu-Aβ, including in presence of zinc, the second metal ions important in the etiology of Alzheimer’s disease. The importance of the reduced state of copper, Cu(I), in the prevention and arrest of ROS is mechanistically described with the help of cyclic voltammetry experiments.     

Determination of the rheological properties of aqueous solutions of branched PEO‐PPO‐PEO copolymers. Confrontation with small‐angle neutron scattering studies.

The physico‐chemical properties of Tetronic^® 908 in aqueous solution have been explored on a wide range of temperature and concentration. This system presents interesting rheological properties depending on the polymer concentration in solution, and temperature. For weight percentage p comprised between 5% and 20%, the viscosity of the solution passes through a maximum. Small angle neutron scattering experiments show that the increase in the viscosity is due to the progressive aggregation of the chains. For higher weight percentages, the viscosity of the system diverges and the mixture becomes “gel‐like”. SANS studies of the same solution indicate that the micelles are organized in a cubic structure. We have developed a model which suitably describes the SANS curves of the system in the region where micelles are formed. It allows the calculation of several parameters (volume fraction of the micelles, size, composition). The evolution of these parameters with temperature and polymer concentration is detailed. Comparisons with models of literature are discussed.     

Electron-induced mass spectrometry of 1,2-dihydropyridine derivatives

The electron-induced mass spectrometry of 1-substituted-4-phenyl-1,2-dihydropyridines is characterized by a [M-1] peak that accounts for the base peak, and a fragment corresponding to the loss of the N-substituent in every example examined.     

The “Historical Materials BAG”: A New Facilitated Access to Synchrotron X-ray Diffraction Analyses for Cultural Heritage Materials at the European Synchrotron Radiation Facility

The European Synchrotron Radiation Facility (ESRF) has recently commissioned the new Extremely Brilliant Source (EBS). The gain in brightness as well as the continuous development of beamline instruments boosts the beamline performances, in particular in terms of accelerated data acquisition. This has motivated the development of new access modes as an alternative to standard proposals for access to beamtime, in particular via the “block allocation group” (BAG) mode. Here, we present the recently implemented “historical materials BAG”: a community proposal giving to 10 European institutes the opportunity for guaranteed beamtime at two X-ray powder diffraction (XRPD) beamlines—ID13, for 2D high lateral resolution XRPD mapping, and ID22 for high angular resolution XRPD bulk analyses—with a particular focus on applications to cultural heritage. The capabilities offered by these instruments, the specific hardware and software developments to facilitate and speed-up data acquisition and data processing are detailed, and the first results from this new access are illustrated with recent applications to pigments, paintings, ceramics and wood.