Ferric hydrogensulphate as a recyclable catalyst for the synthesis of fluorescein derivatives

Polycondensation reactions of phenols with phthalic anhydride were carried out in the presence of ferric hydrogensulphate under melt conditions. The reactions proceeded in short reaction times by using a catalytic amount of Fe(HSO₄)₃ and the corresponding fluorescein derivatives were obtained in high yields. The simplicity, scale-up, along with the use of an inexpensive, non-toxic, recyclable catalyst of an environmentally benign nature, are other remarkable features of the procedure. The absorption and emission properties of these fluorescein derivatives were studied.     

Application of Liquid-Liquid Microextraction-High-Performance Thin-Layer Chromatography for Preconcentration and Determination of Phenolic Compounds in Aqueous Samples

JPC – Journal of Planar Chromatography – Modern TLC - A novel liquid-phase microextraction method coupled with high-performance thin-layer chromatography (HPTLC) for preconcentration,...     

In Silico Identification of Tripeptides as Lead Compounds for the Design of KOR Ligands

The kappa opioid receptor (KOR) represents an attractive target for the development of drugs as potential antidepressants, anxiolytics and analgesics. A robust computational approach may guarantee a reduction in costs in the initial stages of drug discovery, novelty and accurate results. In this work, a virtual screening workflow of a library consisting of ~6 million molecules was set up, with the aim to find potential lead compounds that could manifest activity on the KOR. This in silico study provides a significant contribution in the identification of compounds capable of interacting with a specific molecular target. The main computational techniques adopted in this experimental work include: (i) virtual screening; (ii) drug design and leads optimization; (iii) molecular dynamics. The best hits are tripeptides prepared via solution phase peptide synthesis. These were tested in vivo, revealing a good antinociceptive effect after subcutaneous administration. However, further work is due to delineate their full pharmacological profile, in order to verify the features predicted by the in silico outcomes.     

Chromatographic separation of inorganic ions on thin layers of lanthanum silicate ion-exchanger

Summary Thin layers of lanthanum silicate have been used to study the chromatographic behaviour of 28 metal ions in aqueous and mixed systems. As³⁺, Mo⁶⁺, Sb³⁺, Ti⁴⁺ and others can be easily separated from a number of inorganic ions. Fast ternary and binary separations have also been achieved and various separations are discussed. It is shown that Alberti's relation is also obeyed by thin layers of lanthanum silicate. Presented at the 21^st ISC held in Stuttgart, Germany, 15^th–20^th September, 1996     

Quantitative Ion-Exchange TLC of p-Hydroxybenzoic Acid in the Presence of Preservatives

JPC – Journal of Planar Chromatography – Modern TLC - Rapid separation of p-hydroxybenzoic acid from methyl p-hydroxy-benzoate, ethyl p-hydroxybenzoate, propyl p-hydroxybenzoate,...     

Polarity‐based fractionation in proteomics: hydrophilic interaction vs reversed‐phase liquid chromatography

During recent decades, hydrophilic interaction liquid chromatography (HILIC) ahs been introduced to fractionate or purify especially polar solutes such as peptides and proteins while reversed‐phase liquid chromatography (RPLC) is also a common strategy. RPLC is also a common dimension in multidimensional chromatography. In this study, the potential of HILIC vs RPLC chromatography was compared for proteome mapping of human peripheral blood mononuclear cell extract. In HILIC a silica‐based stationary phase and for RPLC a C₁₈ column were applied. Then separated proteins were eluted to an ion trap mass spectrometry system. Our results showed that the HILIC leads to more proteins being identified in comparison to RPLC. Among the total 181 identified proteins, 56 and 38 proteins were fractionated specifically by HILIC and RPLC, respectively. In order to demonstrate this, the physicochemical properties of identified proteins such as polarity and hydrophobicity were considered. This analysis indicated that polarity may play a major role in the HILIC separation of proteins vs RPLC. Using gene ontology enrichment analysis, it was also observed that differences in physicochemical properties conform to the cellular compartment and biological features. Finally, this study highlighted the potential of HILIC and the great orthogonality of RPLC in gel‐free proteomic studies. Copyright © 2015 John Wiley & Sons, Ltd.     

Preparation of Constrained Unnatural Aromatic Amino Acids via Unsaturated Diketopiperazine Intermediate

Unnatural aromatic amino acids are useful tools in drug discovery, since their insertion in bioactive peptide sequences can change the side chains spatial orientation, the backbone conformation and above all, their bioactivity. In this communication, we propose a straightforward method to synthesize 2′,6′‐dimethyl‐tyrosine and 2′,6′‐dimehylphenyl‐alanine derivatives as handling building blocks for peptide synthesis via unsaturated diketopiperazine (DKP) intermediate.     

Topology of orbits and orbit spaces of some product G-manifolds

We give a topological classification of cohomogeneity two Riemannian G-manifolds of nonpositive curvature and their orbits, under the condition that \({M^{G} \neq \emptyset}\) and the universal Riemannian covering of M has a suitable decomposition.     

Evidence for twoρ′ (1600) resonances

The data on the reactionse ⁺ e ^?→π ⁺ π ^?, 2π ⁺2π ^?,π ⁺ π ^? π ⁰ π ⁰ andγp ⁺ γ ^? p, 2γ ⁺2γ ^? p,γ ⁺ γ ^? γ ⁰ γ ⁰ p are analysed. It is found that to obtain a consistent picture it is necessary to postulate two vector resonances with masses of 1.465±0.025 GeV and 1.700±0.025 GeV with widths of 0.235±0.025 GeV and 0.220±0.025 GeV respectively. A key feature in correlating all the data is the importance of off-diagonal terms in the photoproduction of states withJ ^p =1^? and a contribution from states withJ ^P ≠1^?. The results are compatible with thep-wave ππ scattering amplitude.