Complex palytoxin‐like profile of Ostreopsis ovata. Identification of four new ovatoxins by high‐resolution liquid chromatography/mass spectrometry

Over the past decades, Italian coastlines have been plagued by recurring presence of the benthic dinoflagellate Ostreopsis ovata. Such an alga has caused severe sanitary emergencies and economic losses due to its production of palytoxin‐like compounds. Previous studies have confirmed the presence of ovatoxin‐a (OVTX‐a) as the major toxin of the algal toxin profile together with small amounts of putative palytoxin (PLTX). In our ongoing research on O. ovata toxins we report herein on in‐depth investigation of an O. ovata culture carried out by high‐resolution (HR) liquid chromatography/mass spectrometry (LC/MS) and tandem mass spectrometry (MS²). Particularly, the presence of putative PLTX and OVTX‐a was confirmed and the occurrence in the extract of four new palytoxin‐like compounds, OVTX‐b, ‐c, ‐d, and ‐e, was highlighted. Elemental formulae have been assigned to the new ovatoxins and information has been gained about their structural features. A quantitative study of the O. ovata culture extract indicated that the whole of the new ovatoxins represents about 46% of the total toxin content and, thus, their presence has to be taken into account when LC/MS‐based monitoring programs of either plankton or contaminated seafood are carried out. Copyright © 2010 John Wiley & Sons, Ltd.     

Convex domains of Finsler and Riemannian manifolds

A detailed study of the notions of convexity for a hypersurface in a Finsler manifold is carried out. In particular, the infinitesimal and local notions of convexity are shown to be equivalent. Our approach differs from Bishop??s one in his classical result (Bishop, Indiana Univ Math J 24:169?C172, 1974) for the Riemannian case. Ours not only can be extended to the Finsler setting but it also reduces the typical requirements of differentiability for the metric and it yields consequences on the multiplicity of connecting geodesics in the convex domain defined by the hypersurface.     

Automated detection and characterization of graphene and few‐layer graphite via Raman spectroscopy

Several processes have to be automated in order to use graphene in future industrial applications. One of these is the detection and characterization of graphene and few‐layer graphite (FLG) flakes on a substrate. Raman spectroscopy is an ideal tool for this purpose, as it allows not only the identification of these graphitic materials on arbitrary substrates but also monitoring the quality of flakes within the sample. In this paper, we report how graphene and FLG crystallites can be automatically detected and characterized by monitoring the evolution of Raman bands. We present an algorithm that achieves this purpose and thus has special potential in industrial applications of graphene. Copyright © 2010 John Wiley & Sons, Ltd.     

Expedient synthesis of pseudo-Pro-containing peptides: towards constrained peptidomimetics and foldamers

The reaction of sulfonyl peptides containing L- or D-configured Ser or Thr with bis(succinimidyl) carbonate in the presence of a catalytic amount of a base affords, in solution or in the solid phase, the corresponding peptides with one or two, consecutive or alternate oxazolidin-2-ones (Oxd). The Oxd ring can be regarded to as a pseudo-Pro with an exclusively trans conformation of the preceding peptide bond; homochiral Oxd-containing peptides adopt extended conformations, while the presence of a D-configured Oxd favours folded conformations.     

Optimized use of reversible binding for fast and selective NMR localization of caged xenon

The NMR signal of hyperpolarized (129) Xe trapped in cryptophane cages in different solvents experiences different chemical shifts. An encoding method is presented that involves the optimal use of reversible Xe binding and efficiently uses hyperpolarization. This method is utilized in nanomolar imaging, subsecond imaging, and time-resolved studies while maintaining high spectral selectivity.     

Baeyer-Villiger oxidation in supercritical CO2 with potassium peroxomonosulfate supported on acidic silica gel

Supercritical carbon dioxide (scCO2) is an efficient reaction medium to perform the Baeyer-Villiger oxidation with hydrated silica-supported potassium peroxomonosulfate (h-SiO2.KHSO5) under flow-through conditions. Hydration modulates the reactivity of the active surface by softening the acidity of the KHSO4 present in the supported reagent. The reaction in scCO2 is much more efficient than in n-hexane under similar conditions, which is attributed to better transport and solvating properties of the supercritical medium with regard to n-hexane.     

Cauchy problem for nonlinear p-evolution equations

The local solvability of the Cauchy problem in Sobolev spaces is studied for a class of nonlinear partial differential equations incorporating weakly hyperbolic and Schrödinger equations.     

Prince Cangrande’s Collagen: Study of Protein Modification on the Mummy of the Lord of Verona,Italy (1291–1329 AD)

The natural mummy of prince Cangrande, Lord of Verona, Italy (1291–1329 AD) was studied. Two samples were taken: rib bone and muscle. These samples were cleaved with trypsin and analysed by liquid chromatographic methods coupled to mass spectrometry (Q-TOF, ion-trap). Special attention was devoted to nonenzymatic protein modification––the deamidation of asparagine and glutamine. A huge amount of collagen was determined in the tissues of the mummy (covering over 80 % of the sequence)––collagen type I was identified in the rib bone and collagen types I and III in the muscle. A high overall percentage of asparaginyl and glutaminyl residues were deamidated (up to 92 %). In agreement with the literature we can suppose that the deamidation of really old samples (at least 100-years-old) is mainly dependent on the burial conditions and/or thermal age and cannot serve as a precise “molecular clock”.     

Synthesis and Analysis of the Conformational Preferences of 5‐Aminomethyloxazolidine‐2,4‐dione Scaffolds: First Examples of β2‐ and β2, 2‐Homo‐Freidinger Lactam Analogues

Constrained peptidomimetic scaffolds are of considerable interest for the design of therapeutically useful analogues of bioactive peptides. We present the single‐step cyclization of (S)‐ or (R)‐α‐hydroxy‐β²‐ or α‐substituted‐α‐hydroxy‐β^{2, 2}‐amino acids already incorporated within oligopeptides to 5‐aminomethyl‐oxazolidine‐2,4‐dione (Amo) rings. These scaffolds can be regarded as unprecedented β²‐ or β^{2, 2}‐homo‐Freidinger lactam analogues, and can be equipped with a proteinogenic side chain at each residue. In a biomimetic environment, Amo rings act as inducers of extended, semi‐bent or folded geometries, depending on the relative stereochemistry and the presence of α‐substituents.