A local balance property of episturmian words

We prove that episturmian words and Arnoux-Rauzy sequences can be characterized using a local balance property. We also give a new characterization of epistandard words and show that the set of finite words that are not factors of an episturmian word is not context-free

Quasiperiodic Sturmian words and morphisms

AbstractWe characterize all quasiperiodic Sturmian words: A Sturmian word is not quasiperiodic if and only if it is a Lyndon word. Moreover, we study links between Sturmian morphisms and quasiperiodicity

A Coloring Problem for Sturmian and Episturmian Words

We consider the following open question in the spirit of Ramsey theory: Given an aperiodic infinite word $w$, does there exist a finite coloring of its factors such that no factorization of $w$ is monochromatic? We show that such a coloring always exists whenever $w$ is a Sturmian word or a standard episturmian word

On Quasiperiodic Morphisms

Weakly and strongly quasiperiodic morphisms are tools introduced to study quasiperiodic words. Formally they map respectively at least one or any non-quasiperiodic word to a quasiperiodic word. Considering them both on finite and infinite words, we get four families of morphisms between which we study relations. We provide algorithms to decide whether a morphism is strongly quasiperiodic on finite words or on infinite words.Comment: 12 page

Free and immobilized matrix molecules: impairing ionization by quenching secondary ion formation in laser desorption MS

Within the last 25 years, matrix-assisted laser desorption ionization (MALDI) has become a powerful analytical tool in mass spectrometry (MS). While the method has been successfully applied to characterize large organic molecules such as proteins, sugars and polymers, its utilization for small molecules (≤ 600 Da) is significantly impaired by the coformation of matrix ions. Reducing or eliminating matrix-related signals has been subject of many studies. Some of which propose the enhancement of so-called matrix suppression effects, while others suggest the replacement of matrix molecules by materials such as microporous silicon. Alternatively, the immobilization of matrix molecules by utilizing them as self-assembled monolayers (SAMs) has been discussed. In continuation of this research, the current manuscript focuses on the elucidation of ion formation processes occurring on the surface of light absorbing SAMs. Ion yields obtained by free and immobilized matrix molecules as well as those generated by matrix-free gold film-assisted laser desorption ionization (GF-LDI) were compared. Experiments showed that the formation of strong analyte signals essentially required the presence of free matrix molecules, while the immobilization of the latter severely impaired ionization. The observed effect inversely correlated with the surface coverage of SAMs determined by cyclic voltammetry (CV). Based on these findings, the MS signal generated on light absorbing SAMs could be used supplementary to CV for determining the surface coverage of light absorbing SAMs

First 2-Hydroxy-3-Methylbut-3-Enyl Substituted Xanthones Isolated From Plants: Structure Elucidation, Synthesis and Antifungal Activity

Two new 2-hydroxy-3-methylbut-3-enyl substituted xanthones, ( - )-caledol 1 and ( - )-dicaledol 2 were isolated from a dichloromethane extract of the leaves of Calophyllum caledonicum (Clusiaceae). Compounds 1 and 2 are the first 2-hydroxy-3-methylbut-3-enyl substituted xanthones isolated from natural source. Their structures were elucidated by means of combined analytical methods including HRFABMS, 1D and 2D NMR spectroscopies and also confirmed by total synthesis using biomimetic ortho -prenylphenols photooxygenation ( 1 O 2 ) as a key step. The antifungal activity against Aspergillus fumigatus is reported

A promising method for efficient analysis of secondary metabolites in plant extracts by a matrix-free Desorption/Ionization on self-Assembled Monolayer Surfaces (DIAMS) technique

Plants are one of the major sources for the biologically active organic compounds and play a key role in medicinal chemistry for the treatment of various diseases [1]. DIAMS method is able to determine the secondary metabolites of complex vegetal extracts. The high throughput analyses of vegetal extracts are relatively difficult to perform in MALDI mass spectrometry, since the preparation of the sample involves the co-crystallization of the matrix with the analyte. Moreover irradiation of the matrix ion produces many low-m/z vs high-intensity ions preventing the detection of low molecular weight molecules such as secondary metabolites. We have developed a matrix-free alternative to MALDI analyses by the means of an original desorption/ionization on self-assembled monolayers surfaces (DIAMS) technique [2]. Monolayers were formed by using novel thiophene and coumarin-triazole analogues that absorbs the laser beam at 337nm. We herein disclose our findings with respect to the DIAMS method which is well suitable for the detection and quantification of the low molecular weight compounds that are present in plant extracts. Some of the isoquinoline alkaloids from the root extracts of Thalictrum flavum have been detected by the DIAMS method. Indeed, this technique would be promising suitable for the qualitative and quantitative analysis of polar and non-polar organic components that are widely distributed in the plants, without any preliminary chromatographic resolution [3]

Advanced glycation inhibition and protection against endothelial dysfunction induced by coumarins and procyanidins from Mammea neurophylla.

Advanced glycation end-products (AGEs) are associated with many pathogenic disorders such as pathogenesis of diabetes or endothelial dysfunction leading to cardiovascular events. Therefore, the identification of new anti-AGE molecules or extracts aims at preventing such pathologies. Many Clusiaceae and Calophyllaceae species are used in traditional medicines to treat arterial hypertension as well as diabetes. Focusing on these plant families, an anti-AGE plant screening allowed us to select Mammea neurophylla for further phytochemical and biological studies. Indeed, both DCM and MeOH stem bark extracts demonstrated in vitro their ability to prevent inflammation in endothelial cells and to reduce vasoconstriction. A bioguided fractionation of these extracts allowed us to point out 4-phenyl- and 4-(1-acetoxypropyl)coumarins and procyanidins as potent inhibitors of AGE formation, potentially preventing endothelial dysfunction. The fractionation steps also led to the isolation of two new compounds, namely neurophyllols A and B from the DCM bark extract together with thirteen known mammea A and E coumarins (mammea A/AA, mammea A/AB, mammea A/BA, mammea A/BB, mammea A/AA cycloD, mammea A/AB cycloD, disparinol B, mammea A/AB cycloE, ochrocarpin A, mammea A/AA cycloF, mammea A/AB cycloF, mammea E/BA, mammea E/BB) as well as δ-tocotrienol, xanthones (1-hydroxy-7-methoxyxanthone, 2-hydroxyxanthone) and triterpenes (friedelin and betulinic acid). During this study, R,S-asperphenamate, previously described from fungal origin was also purified