Development of N,N-bis(perfluoroalkanesulfonyl)squaramides as new strong Brønsted acids and their application to organic reactions

New strong Brønsted acids derived from a squaric acid scaffold bearing different perfluoroalkanesulfonyl groups have been developed and applied to several organic reactions. These squaramides are bench-stable and exhibit much higher reactivities in several organic reactions than squaric acid itself. N,N-Bis(trifluoromethanesulfonyl)squaramide 2a was applied to the Mukaiyama aldol reaction and Mukaiyama Michael reaction. Mechanistic studies revealed that the Brønsted acid might be the predominant catalyst through direct protonation of carbonyl compound by the acid itself rather than the silylated Brønsted acid. The utility of this acid 2a was further extended to Hosomi-Sakurai allylation of aldehydes and a carbonyl-ene reaction. Furthermore, other squaramides 2b and c bearing longer perfluoroalkyl chains have been developed, which are also bench-stable and displayed similar reactivities with squaramide 2a in several organic reactions.     

Fucoidan-Degrading Fungal Strains: Screening,Morphometric Evaluation,and Influence of Medium Composition

Ten different fungal strains from the genus Aspergillus, Penicillium, and Mucor were screened for fucoidan hydrolyzing ability aiming to find microorganisms able to produce sulfated fucan-degrading enzymes. Screening was carried out by measuring the strains kinetic and morphometric behavior over plate assays using Laminaria japonica fucoidan as only carbon source, testing three nitrogen sources (urea, peptone, and sodium nitrate). The selected fungal strains were subsequently used in submerged fermentations, which were performed for (1) selection of the strains able to growth over fucoidan medium and (2) media selection, testing the synergy of fucoidan with other sugars for inducing high enzyme titles. Radial expansion and hyphae parameters were observed for Aspergillus niger PSH, Mucor sp. 3P, and Penicillium purpurogenum GH2 grown only over fucoidan-urea medium. A. niger PSH showed the maximum enzymatic activity values, which were significantly different (p < 0.05) from those achieved by the other selected fungi. Sucrose addition to fucoidan media proportioned the highest fucoidanase activity values for this fungal strain. This research allowed establishing optimal conditions for metabolites synthesis by fungal stains able to act toward fucoidan ramified matrix.     

Expression and Immunogenicity of a Recombinant Chimeric Protein of Human Colorectal Cancer Antigen GA733-2 and an Fc Antibody Fragment in Stably Transformed Drosophila melanogaster S2 Cells

Human colorectal cancer antigen GA733-2 fused to the immunoglobin Fc fragment (GA733-2-Fc) was expressed in stably transformed Drosophila melanogaster S2 cells, and the immunogenicity of recombinant GA733-2-Fc was investigated in mice. Recombinant GA733-2-Fc was secreted into a culture medium with a molecular mass of approximately 65 kDa. Recombinant GA733-2-Fc was purified to homogeneity using affinity fractionation with Protein A sepharose 4 Fast Flow. Recombinant GA733-2-Fc proteins elicited production of specific antibodies against recombinant GA733-2 by immunization through an intraperitoneal route. Recombinant GA733-2-Fc-induced antibodies showed a binding activity to human colorectal carcinoma HCT-116 cells. Secretory recombinant GA733-2-Fc from Drosophila S2 cell systems can be used as an effective experimental antigen for research in cancer vaccine development.     

Direct synthesis of hydrogen peroxide from hydrogen and oxygen over insoluble Pd<Subscript>0.15</Subscript>M<Subscript>2.5</Subscript>H<Subscript>0.2</Subscript>PW<Subscript>12</Subscript>O<Subscript>40</Subscript> (M = K,Rb, and Cs) heteropolyacid catalysts

Palladium-containing insoluble heteropolyacid (HPA) catalysts (Pd_0.15M_2.5H_0.2PW₁₂O₄₀) were prepared by an ion-exchange method using various alkaline metal ions (M = K⁺, Rb⁺, and Cs⁺) (denoted as Pd-KPW, Pd-RbPW, and Pd-CsPW). They were then applied to the direct synthesis of hydrogen peroxide from hydrogen and oxygen. Conversion of hydrogen over the catalysts was almost identical with no great difference, while selectivity for hydrogen peroxide increased in the order of Pd-KPW < Pd-RbPW < Pd-CsPW. As a consequence, yield for hydrogen peroxide increased in the order of Pd-KPW < Pd-RbPW < Pd-CsPW. It was found that yield for hydrogen peroxide increased with increasing Pd 3d_5/2 binding energy of the catalyst. Among the catalysts tested, Pd-CsPW catalyst with the highest Pd 3d_5/2 binding energy showed the highest yield for hydrogen peroxide.     

UV–vis,IR and 1H NMR spectroscopic studies and characterization of ionic-pair crystal violet–oxytetracycline

The present study shows the formation and characterization of the ionic-pair between the antibiotic oxytetracycline and the dye crystal violet in ammonia solution pH 9.0 ± 0.2 extracted into chloroform. The characterization was demonstrated using UV–vis spectrophotometry, ¹H NMR, measurement of relaxation times T₁ and IR spectroscopy, using a comparison between the signals of individual pure compounds with the signals with the mixture CV–OTC in different alkaline media. The formation of ionic-pair was also corroborated by new signals and chemical shifts. (2D) NMR spectroscopy experiments show that the interaction is electrostatic.     

Interaction between the mouse homologue of CD99 and its ligand PILR as a mechanism of T cell receptor-independent thymocyte apoptosis

Here, we show that the interaction between two membrane proteins, the mouse homologue of CD99 (designated D4) and its ligand, paired immunoglobulin-like type 2 receptor (PILR), is one of the major mechanisms of thymocyte apoptosis. Using the polymeric fusion protein of PILR and IgG1 (PILR-Ig), we demonstrated that D4 ligation in the absence of T cell receptor (TCR) engagement leads to the induction of apoptosis, mainly at the double-positive stage of thymocytes. This was further confirmed by a blocking study in which blocking the interaction between D4 and PILR by soluble D4 protein led to reduced apoptosis in the fetal thymic organ culture with wild type and TCRα^-/- mice. Furthermore, the dissection of intracellular signaling pathway demonstrated that D4 cross-linking led to caspase activation without any change in mitochondrial membrane potential. Based on these data, we propose a mechanism for thymocyte depletion in which the interaction between D4 and PILR delivers an active signal.     

Conformational Studies of (±)‐11,12‐Didehydro‐11‐deoxycorynoline and (+)‐11,13‐Didehydro‐11‐deoxychelidonine,Hexahydrobenzo[c]phenanthridine‐Type Alkaloid Derivatives,by X‐Ray Crystal Structure and NMR Analyses

The X‐ray crystal analyses of the two 11‐deoxy‐didehydrohexahydrobenzo[c]phenanthridine‐type alkaloid derivatives 3 and 4 , derived from (±)‐corynoline ( 1 ) and (+)‐chelidonine ( 2 ), established their structures as (±)‐(5bRS,12bRS)‐5b,12b,13,14‐tetrahydro‐5b,13‐dimethyl[1,3]benzodioxolo[5,6‐c]‐1,3‐dioxolo[4,5‐i]phenanthridine ( 3 ) and (+)‐rel‐(12bR)‐7,12b,13,14‐tetrahydro‐13‐methyl[1,3]benzodioxolo[5,6‐c]‐1,3‐dioxolo[4,5‐i]phenanthridine ( 4 ). The conformations of 3 and 4 in CDCl₃ were determined on the basis of ¹H‐ and ¹³C‐NMR spectroscopy.     

Characterisation of five coins from the archaeological heritage of Portugal

This paper reports a study carried out on three Roman and two Portuguese coins found in the archaeological site of São Pedro, in Fronteira (Alentejo, Portugal). The three Roman coins have been identified as a Follis, an AE 2 and an AE 3 (bronze alloys), while the Portuguese coins have been identified as a Ceitil (copper) and the “6 vinténs” (Ag–Cu alloy). Scanning electron microscopy (SEM) coupled to energy dispersive spectroscopy (EDS) has allowed the semi-quantitative determination of the elemental composition of both the corrosion products and the alloy used in the manufacture of the coins. The crystalline corrosion products constituents of the patinas were identified by X-ray powder diffraction spectroscopy (XRD). The more deteriorated coin, the AE 3, was submitted to electrochemical studies in Na₂SO₄ aqueous solution and the corresponding data analysed. After 3 weeks, the E _OCP was still quite stable, ranging between ?0.050 and ?0.070 V vs. SCE; the corrosion resistance, R _p, was of the order of 5 to 3?×?10³ Ω. Chemical treatment of the sample by 1-h immersion in 0.1 M NaOH produced a more active surface, with R _p showing a decrease of a factor of about ten. On the other hand, it was concluded from voltammetric data that polarisations of E _a?≥?0.050 V vs. SCE led to copper oxidation, with no reduction of the other corrosion products.     

Electrochemical study of dopamine and noradrenaline at the water/1,6-dichlorohexane interface

Interfaces between two immiscible electrolyte solutions are recognized as a simplified model for biological systems and they can be of great relevance to the characterization of biomolecules and their role in biological systems. In this work, ion transfer and facilitated ion transfer of protonated catecholamines (dopamine and noradrenaline) by dibenzo-18-crown-6 are investigated at the water/1,6-dichlorohexane interface. The formation constant of the complex between both dopamine and noradrenaline with dibenzo-18-crown-6 was evaluated and the experimental conditions for the analytical determination of those catecholamines are established. These results can improve the understanding of the pharmacodynamics of the catecholamines, and contribute to the study of their interaction with biological membranes. Furthermore it can be used to develop an alternative method for the determination of neural signal transmission catecholamines.