Formal total synthesis of (+/-)-estrone and zirconocene-promoted cyclization of 2-fluoro-1,7-octadienes and ru-catalyzed ring closing metathesis

A new and diastereoselective method for the synthesis of the estrone skeleton from a substituted styrene based on sequential 3-fold use of Cp 2ZrBu 2 (oxidative addition-alkylation and two cyclization-alkylation sequences) and a ruthenium complex catalyzed RC-metathesis of a sterically hindered diene was developed. The prepared estratetraene was obtained in 7 steps from a commercially available starting material and thus the overall synthesis of estrone could be accomplished in 9 steps. Moreover, we have also found that the course of the reaction of substrates bearing the 2-halo-1,7-diene moiety with Cp 2ZrBu 2, i.e., cyclization or oxidative addition to the C-X bond, could be controlled by the nature of the halogen leaving group.     

Dependence of the L-alanyl-L-alanine conformation on molecular charge determined from ab initio computations and NMR spectra

The l-alanyl-l-alanine (AA) molecule behaves differently in acidic, neutral, and basic environments. Because of its molecular flexibility and strong interaction with the aqueous environment, its behavior has to be deduced from the NMR spectra indirectly, using statistical methods and comparison with ab initio predictions of geometric and spectral parameters. In this study, chemical shifts and indirect spin-spin coupling constants of the AA cation, anion, and zwitterion were measured and compared to values obtained by density functional computations for various conformers of the dipeptide. The accuracy and sensitivity of the quantum methods to the molecular charge was also tested on the (mono)-alanine molecule. Probable AA conformers could be identified at two-dimensional potential energy surfaces and verified by the comparison of the computed parameters with measured NMR data. The results indicate that, whereas the main-chain peptide conformations of the cationic (AA+) and zwitterionic (AAZW) forms are similar, the anion (AA-) adopts also another, approximately equally populated conformer in the aqueous solution. Additionally, the NH2 group can rotate in the two main chain conformations of the anionic form AA-. According to a vibrational quantum analysis of the two-dimensional energy surfaces, higher-energy conformers might exist for all three charged AA forms but cannot be detected directly by NMR spectroscopy because of their small populations and short lifetimes. In accord with previous studies, the NMR parameters, particularly the indirect nuclear spin-spin coupling constants, often provided an excellent probe of a local conformation. Generalization to peptides and proteins, however, has to take into account the environment, molecular charge, and flexibility of the peptide chain.     

ProteinQuant Suite: a bundle of automated software tools for label-free quantitative proteomics

In simplifying the evaluation and quantification of high-throughput label-free quantitative proteomic data, we introduce ProteinQuant Suite. It comprises three standalone complementary computer utilities, namely ProtParser, ProteinQuant, and Turbo RAW2MGF. ProtParser is a filtering utility designed to evaluate database search results. Filtering is performed according to different criteria that are defined by the end-user. ProteinQuant then utilizes this parsed list of peptides and proteins in conjunction with mzXML or mzData files generated from the raw files for quantification. This quantification is based on the automatic detection and integration of chromatographic peaks representative of the liquid chromatography/mass spectrometry (LC/MS) elution profiles of identified peptides. Turbo RAW2MGF was developed to extend the applicability of ProteinQuant Suite to data collected from different types of mass spectrometers. It directly processes raw data files generated by Xcalibur, a ThermoElectron data acquisition software, and generates a MASCOT generic file (MGF). This file format is needed since the protein identification results generated by the database search employing this file format include information required for the precise identification and quantification of chromatographic peaks. The performance of ProteinQuant Suite was initially validated using LC/MS/MS generated for a mixture of standard proteins as well as standard proteins spiked in a complex biological matrix such as blood serum. Automated quantification of the collected data resulted in calibration curves with R(2) values higher than 0.95 with linearity spanning over more than 2 orders of magnitude with peak quantification reproducibility better than 15% (RSD). ProteinQuant Suite was also applied to confirm the binding preference of standard glycoproteins to Con A lectin using a sample consisting of both standard glycoproteins and proteins.     

Comparison of chemical composition and free radical scavenging ability of glycosidically bound and free volatiles from Bosnian pine (Pinus heldreichii Christ. var. leucodermis)

The results obtained show that Bosnian pine is rich in glycosidically bound volatile compounds with strong free radical scavenging properties. Since volatiles can be released from nonvolatile glycoside precursors, these compounds can be considered as a hidden potential source of antioxidant substances and may contribute to the total free radical scavenging ability of Bosnian pine.     

Laser-induced photofragmentation of neutral and acidic glycans inside an ion-trap mass spectrometer

Permethylated acidic and neutral N-glycans representing different types of glycan structures, such as linear and branched sialylated structures, high-mannose type and fucosylated complex type, were photodissociated with 157 nm vacuum ultraviolet light in a linear ion trap. Cross-ring fragments corresponding to high-energy fragmentation pathways were observed in abundance for all studied structures. Some product ions appear diagnostic for a linkage of sialic acid residues and the glycan antenna to which these residues are attached. A conclusive assignment of the fucosylation site of the studied glycan structure has been facilitated through measurement of cross-ring fragmentation resulting from photodissociation.     

Lattice energy calculation for quantitatively-modeled Perovskite distortion

In case of reactions, it is a necessary condition that the free energy of formation, Δ_fG, of the product is lower than the total free energies of formation of the reactants. The free energy of all reactions and/or all compounds have not been determined in the literature. In this paper, we report the formation, stability, and reactions for all compounds based on their free energies. However, it also seems possible to discuss them based on their lattice energies, because it can be calculated for many compounds if their composition, structure and their lattice parameters are known. Also, we can discuss the formation, stability, etc., for compounds excluding small effects due to temperature and entropy. As a result of the calculations, the lattice energy correlates with the perovskite distortion.     

Structural analysis of sulfated glycans by sequential double-permethylation using methyl iodide and deuteromethyl iodide

MALDI mass spectrometric characterization of sulfated glycans is often challenging due to their low ionization response in the positive ion mode. Here we demonstrate a new analytical approach, allowing the measurement of sulfated glycans by substituting the sulfate group with a deuteromethyl group. Sulfated glycan samples are initially permethylated before the methanolytic cleavage of their sulfate groups. Desulfated and permethylated glycans are then subjected to another permethylation step using deuteromethyl iodide to label the hydroxyl groups resulting from methanolysis. The number of attached sulfate groups is subsequently calculated from the mass-shift resulting from the chemical cleavage of these sulfate groups. The position of the sulfate substitution is then determined by collision-induced dissociation (CID) tandem mass spectrometry of permethylated and permethylated plus deuteromethylated samples. The described approach was initially optimized and validated using linear standard glycans, while its effectiveness has also been demonstrated here for the N-glycans derived from bovine thyroid-stimulating hormone (bTSH).     

Non-noble metal catalyst for a future Pt free PEMFC

We have investigated the possibility of developing high-performance, cost-effective and durable non-noble Co metal electrocatalyst for PEMFC. In this work we applied electrodeposition process for PEMFC electrode preparation that is very efficient and far simpler than any other investigated method. The fuel cell with electrodeposited Co as anode catalyst has shown satisfying performance level. In determining FC’s operating conditions, subsequent electrochemical impedance and output power measurements were done, which enable the insight into the Co catalyst based anode behavior. Structure analysis of the electrodeposited anode layer was done by means of SEM and EDS technique. Although the Pt catalyst has higher efficiency, its cost performance ratio is significantly lower than for the Co catalyst, thus this investigation gives interesting possibilities in area of stationary fuel cell application.