Phosphopeptide enrichment with stable spatial coordination on a titanium dioxide coated glass slide

Recent advances in phosphoproteomics have established powerful tools to analyze phosphorylation events. However, their spatial localization is lost due to sample homogenization procedures prior to the analysis. Imaging mass spectrometry (IMS) has emerged as a method to visualize the spatial distribution of molecules in tissue samples, but its application is still limited to relatively abundant molecules. Due to low phosphorylation stoichiometry, direct detection and imaging of protein phosphorylation by MS has not been achieved yet. Therefore we have developed a novel phosphopeptide enrichment strategy as a potential tool for in situ affinity imaging MS (AIMS). A specific type of titanium dioxide (TiO₂)‐coated glass slides was designed and validated with casein tryptic digests for their ability to selectively retain phosphopeptides while maintaining their spatial coordination. Copyright © 2009 John Wiley & Sons, Ltd.     

Improving the algorithm of Bafna and Pevzner for the problem of sorting by transpositions: a practical approach

In computational biology, genome rearrangements is a field in which we investigate the combinatorial problem of sorting by transpositions. This problem consists in finding the minimum number of transpositions (mutational event) that transform a chromosome into another. Bafna and Pevzner [SIAM J. 11 (2) (1998) 224–240] proposed a 1.5-approximation algorithm to solve this problem, using a structure called cycle graph. In this work, we first present results that allowed us to implement their algorithm, maintaining the 1.5-approximation ratio. The present implementation runs in O(n³) time complexity, noting that we created a data structure to store the cycle graph in memory in O(n) time complexity. The results obtained from the program allowed us to propose heuristics, that further improved the performance of the original algorithm. Comparing our experimental results with the best results published so far, we achieved better performance. Besides, we developed a program to visualize the cycle graphs and the transpositions indicated by the algorithm. This work targets to contribute for discovering the complexity of the problem of sorting by transpositions, which remains open.     

Global smooth solutions for a quasilinear fractional evolution equation

The global existence of smooth solutions to a class of quasilinear fractional evolution equations is proved. The proofs are based on L^p(L^q) L^p(L^q) maximal regularity results for the corresponding linear equations.     

Discussion of parameters associated with the determination of arsenic by electrothermal atomic absorption spectrometry in slurried environmental samples

A slurry sampling – fast program procedure has been developed for the determination of arsenic in plants, soils and sediments by electrothermal atomic absorption spectrometry. Efficiencies of various single and mixed modifiers for thermal stabilization of arsenic and for a better removal of the matrix during pyrolysis step were compared. The influence of the slurry concentration, amounts of modifier and parameters of the pyrolysis step on the As integrated absorbance signals have been studied and a comparison between fast and conventional furnace programs was also made. The ultrasonic agitation of the slurry followed by a fast electrothermal program using an Ir/Mg modifier provides the most consistent performance in terms of precision and accuracy. The reliability of the whole procedure has been compared with results obtained after application of a wet digestion method with an HF step and validated by analyzing eleven certified reference materials. Arsenic detection and quantitation limits expressed on dry sample matter were about 30 and 100 μg kg^–1, respectively.     

New Phenolic Compounds from the Roots of Lentil (Lens culinaris)

While lentil (Lens culinaris) seeds are phytochemically well characterized, very little is known about secondary metabolites from lentil roots. Our research on lentil roots led to isolation of five phenolic compounds and five group B soyasaponins. Their structures were established using NMR spectroscopy and mass spectrometry. Four phenolics have not been hitherto described in the literature: 4‐O‐β‐d ‐glucopyranosyl‐2‐methoxybenzoic acid, (αS)‐4,4′‐di‐O‐β‐d ‐glucopyranosyl‐α,2′‐dihydroxydihydrochalcone, (αS)‐4′‐O‐β‐d ‐glucopyranosyl‐α,2′,4‐trihydroxydihydrochalcone, and keto‐2‐hydroxyglycitein. The DPPH^? radical‐scavenging activity of the purified phenolic compounds was additionally evaluated.     

Hydrolytic and redox transformations of chromium(III) bis-oxalato complexes with glutaminic acid and glutamine: a kinetic,UV–Vis and EPR,study

The title complexes have been synthesized, chromatographically isolated and characterized by their ligands to metal ratio determinations and spectroscopic analyses. The kinetics of the first aquation stage, i.e., the amino acid chelate ring opening via the Cr–N bond cleavage, has been studied spectrophotometrically in acidic and alkaline media. Hydrogen peroxide oxidizes the complexes in alkaline media to CrO ₄ ^2? anion and a relatively stable Cr(V) complex. Consecutive biphasic kinetics through two first-order steps were observed for the base hydrolysis and the oxidation process, whereas the acid-catalyzed aquation obeys a simple first-order pattern. Based on the kinetic and spectroscopic data, mechanisms of the coordinated amino acid liberation and chromium(III) oxidation are discussed.     

Flow in a Paper‐based Bioactive Channel – Study on Electrochemical Detection of Glucose and Uric Acid

Although paper‐based analysis is known for centuries, only during the last decade this simple substrate became an object of detailed microfluidic studies. In order to obtain optimum performance and separation of the analytes in a microfluidic channel, devices should be optimized, both in terms of architecture and paper properties. Enzyme immobilization methods can not only increase the storage stability but also have an impact on the flow in paper matrix, providing additional charges, and changing the porous structure of paper. Therefore it should be guaranteed that the method of choice will not obstruct the flux in the final device. Paper‐based device proposed in this study was composed of a bioactive channel, Pt working electrode, pencil drawn pseudo‐reference electrode, a buffer filled sponge providing the wicking solution and a stack of wicking pads to guarantee continuous flow. Based on our previous research we chose 4 methods of enzyme immobilization relying on different phenomena (adsorption, covalent linkage, layer‐by‐layer, capsules). Different channel architectures were also evaluated in order to achieve optimum time of the enzymatic reaction, separation of peaks and the time of measurement. Experimental results were compared with computer simulations. Final device could quantify glucose (2.0–10.0 mmol L^?1) and uric acid (0.1–1.2 mmol L^?1) in their clinical range with good repeatability.     

Matrix Recrystallization for MALDI-MS Imaging of Maize Lipids at High-Spatial Resolution

Matrix recrystallization is optimized and applied to improve lipid ion signals in maize embryos and leaves. A systematic study was performed varying solvent and incubation time. During this study, unexpected side reactions were found when methanol was used as a recrystallization solvent, resulting in the formation of a methyl ester of phosphatidic acid. Using an optimum recrystallization condition with isopropanol, there is no apparent delocalization demonstrated with a transmission electron microscopy (TEM) pattern and maize leaf images obtained at 10 μm spatial resolution.

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Anthocyanins profile,total phenolics and antioxidant activity of two Romanian red grape varieties: Fetească neagră and Băbească neagră (<Emphasis Type="Italic">Vitis vinifera</Emphasis>)

The phenolic composition of Feteasc? neagr?and B?beasc? neagr? grapes from Dealul Bujorului vineyard (south-east Romania) was studied using the spectrophotometric and high-performance liquid chromatographic (HPLC) methods. The results revealed significant differences between these cultivars. Total anthocyanins ranged from 0.22–5.98 mg g^?1 DW berries in B?beasc? neagr? grapes to 0.54–18.54 mg g^?1 DW berries in Feteasc? neagr?. Both cultivars were characterised by an interesting anthocyanin profile for winemaking with a prevalence of malvidin-3-glucoside. The skins and seeds both had small amounts of flavonoids. In contrast with B?beasc? neagr?, Feteasc? neagr? had more flavonoids in the seeds (69 %) than in the skins. Statistically significant correlations were observed between antioxidant activity and total anthocyanin content in both varieties. The antioxidant activity was also found to be highly correlated to the total phenolic compounds content.