The 5-deoxy-5-methylthio-xylofuranose residue in mycobacterial lipoarabinomannan. absolute stereochemistry, linkage position, conformation, and immunomodulatory activity

Mycobacteria produce a cell-surface glycoconjugate, lipoarabinomannan (LAM), which has been shown to be a potent modulator of the immune response that arises from infection by these organisms. Recently, LAM from the human pathogens Mycobacterium tuberculosis and M. kansasii has been shown to contain an unusual 5-deoxy-5-methylthio-xylofuranose (MTX) residue as well as its corresponding oxidized counterpart, 5-deoxy-5-methylsulfoxy-xylofuranose (MSX). To date, the absolute configuration of these residues and their linkage position to the polysaccharide are unknown, as is their biological role. Through the combined use of chemical synthesis and NMR spectroscopy, we have established that the MTX/MSX residues in these glycoconjugates are of the d-configuration and that they are linked alpha-(1-->4) to a mannopyranose residue in the mannan portion of the glycan. Conformational analysis of the MTX/MSX residue using NMR spectroscopy showed differences in ring conformation and as well as in the rotamer populations about the C-4-C-5 bond, as compared to the parent compound, methyl alpha-d-xylofuranoside. Two of the synthesized disaccharides, 3 and 34, were tested in cytokine induction assays, and neither led to the production of TNF-alpha or IL-12p70. In contrast, both demonstrated modest inhibitory properties when these same cytokines were induced using a preparation of Interferon-gamma and Staphylococcus aureus Cowan strain (SAC/IFN-gamma). These latter observations suggest that this motif may play a role in the immune response arising from mycobacterial infection.     

New Insights into Buffer-Ionic Salt Interactions: Solubilities,Transfer Gibbs Energies,and Transfer Molar Volumes of TAPS and TAPSO from Water to Aqueous Electrolyte Solutions

The solubilities of N-[tris(hydroxymethyl)methyl]-3-aminopropanesulfonic acid (TAPS) or N-[tris(hydroxymethyl)methyl]-3-amino-2-hydroxypropanesulfonic acid (TAPSO) in water and in aqueous solutions of CH₃COOK (KAc), KBr, KCl, or NaCl were determined from density measurements at 298.15 K. The solubilities of TAPS in aqueous solution decrease with increasing concentration of the salts (salting-out effect), whereas those of TAPSO increase with increasing concentration of the salts (salting-in effect). The solubility and density data were further used to calculate the apparent transfer Gibbs energies, Δ_tr G, and transfer molar volumes, D_trV_f^o\Delta_{\mathrm{tr}}V_{\phi}^{\mathrm{o}}, of these buffers from water to aqueous electrolyte solutions at 298.15 K. The contributions of various functional groups of TAPS, TAPSO, and the related buffers (tris(hydroxymethyl)aminomethane, TRIS, and N-tris[hydroxymethyl]-4-amino-butanesulfonic acid, TABS) to the transfer properties were systematically estimated from the calculated Δ_tr G and D_trV_f^o\Delta_{\mathrm{tr}}V_{\phi}^{\mathrm{o}}.     

Isolation of aureol from Smenospongia sp. and cytotoxic activity of some aureol derivatives

The sesquiterpene aureol (1) was isolated by chromatographic fractionation of a non-polar extract from Smenospongia sp. Methylation of aureol yielded 5'-O-methyl-aureol (2) while the prepared acylation products of aureol were 5'-O-acetyl-aureol (3), 5'-O-benzoyl-aureol (4), 5'-O-(4-fluoro-benzoyl)-aureol (5), 5'-O-(4-chlorobenzoyl)-aureol (6), 5'-O-(4-methylbenzoyl)-aureol (7), 5'-O-nicotinoyl-aureol (8), aureol-N,N-dimethylthiocarbamate (9), 5'-O-(2-furoylcarbonyl)-aureol (10), 5'-O-(2-thienoylcarbonyl-aureol (11). The structures of aureol as well as its ten derivatives were established through spectral analysis. The in vitro cytotoxic activities of the eleven compounds were evaluated against Hepa59T/VGH, KB and Hela tumor cell lines.     

A novel integrated method realizing iteratively optimized modeling for proximity field patterning nanolithography

Processing methods used in photonics and nanotechnology have many limitations hindering the ability to realize devices and restricting the actual number of applications. An ideal processing method should require low-cost equipment, be able to produce very fine details, and be scalable to process large area specimens in an acceptable amount of time. Proximity field nanopatterning (PnP) is a lithography method possessing these features. By using interference patterns produced by a two-dimensional phase mask, the technique is able to generate a submicron detailed exposure on a millimeter-size slab of light sensitive photopolymer, which is then developed like a photographic plate to reveal three-dimensional interference patterns from the phase mask. While it is possible to use computer aided simulations to obtain the interference patterns produced by a mask with a certain pattern, the inverse problem of producing a mask for a desired interference pattern cannot be solved in the same way due to the intricacies of light interactions involved in producing the final interference pattern. An alternative method is to iteratively optimize the phase mask so that the interference patterns obtained converge to the desired pattern. The method is elaborated in this article.     

Metal chelates of Triazine-Schiff-bases: Complex formation of 3-(α-phenyl)ethylidenehydrazino-5,6-diphenyl-1,2,4-triazine with copper(II)

Summary Complex formation of copper(II)-ions with 3-(-Phenyl)ethylidenehydrazino-5,6-diphenyl-1,2,4-triazine (BHT) has been investigated using UV-VIS-, IR-, and electrochemical methods. Optimal pH for the 1:1 complex formation (and therefore for analytical applications) was found at 5.4. This complex could be isolated. The acid dissociation constant of the free ligand ispK _a=13.60; formation constants for 1:1 and 1:2 complexes were found to be logK ₁=12.0 and logK ₂=10.4, respectively. Polarographic reduction of both the free ligand and the Cu(II)-complexes is irreversible, diffusion controlled and like the stability of the complexpH-dependent.In course of absence of the Faculty of Education, Ain Schams University, Roxy, Cairo, Egypt.     

Guaianolide Sesquiterpene Lactones from Centaurothamnus maximus

Centaurothamnus maximus (family Asteraceae), is a leafy shrub indigenous to the southwestern Arabian Peninsula. With a paucity of phytochemical data on this species, we set out to chemically characterize the plant. From the aerial parts, two newly identified guaianolides were isolated: 3β-hydroxy-4α(acetoxy)-4β(hydroxymethyl)-8α-(4-hydroxy methacrylate)-1αH,5αH, 6αH-gual-10(14),11(13)-dien-6,12-olide (1) and 15-descarboxy picrolide A (2). Seven previously reported compounds were also isolated: 3β, 4α, 8α-trihydroxy-4-(hydroxymethyl)-lαH, 5αH, 6βH, 7αH-guai-10(14),11(13)-dien-6,12-olide (3), chlorohyssopifolin B (4), cynaropikrin (5), hydroxyjanerin (6), chlorojanerin (7), isorhamnetin (8), and quercetagetin-3,6-dimethyl ether-4’-O-β-d-pyranoglucoside (9). Chemical structures were elucidated using spectroscopic techniques, including High Resolution Fast Atom Bombardment Mass Spectrometry (HR-FAB-MS), 1D NMR; ¹H, ¹³C NMR, Distortionless Enhancement by Polarization Transfer (DEPT), and 2D NMR (¹H-¹H COSY, HMQC, HMBC) analyses. In addition, a biosynthetic pathway for compounds 1–9 is proposed. The chemotaxonomic significance of the reported sesquiterpenoids and flavonoids considering reports from other Centaurea species is examined.     

Thermodynamic study of the second-stage dissociation of N,N-bis-(2-hydroxyethyl)glycine (bicine) in water at different ionic strength and different solvent mixtures

The second stage dissociation constant pK2 of N,N-bis-(2-hydroxyethyl)glycine (bicine) has been determined in aqueous solution at different ionic strengths and different temperatures, using pH-metric technique. The thermodynamic quantities (deltaG(o), deltaH(o), and deltaS(o)) have been studied and discussed. Evaluation of the effect of organic solvent of the medium on the dissociation processes have also been reported and discussed. The organic solvents used were methanol, dimethylsulfoxide (DMSO), and dioxane. The pK2 for the ionization in water +10, +20, +30, +40, and +50 wt % dioxane has been determined at five different temperatures from 15 to 35 degrees C at intervals of 5 degrees C. The thermodynamic quantities were calculated. The implications of the results with regard to specific solute-solvent interactions (particularly stabilization of zwitterionic species) are also discussed.     

Synthesis of 1,3,4‐Oxadiazole Acyclo C‐Nucleosides Bearing 5‐Methylthio{7‐substituted‐1,2,4‐triazolo[1,5‐d]tetrazol‐6‐yl}moieties

Oxidative cyclization of the sugar hydrazones ( 3_a‐f ) derived from {7H‐1,2,4‐triazolo[1,5‐d]tetrazol‐6‐ylsulfanyl}acetic acid hydrazide ( 1 ) and aldopentoses 2_a‐c or aldohexoses 2_d‐f with bromine in acetic acid in the presence of anhydrous sodium acetate, followed by acetylation with acetic anhydride gave the corresponding 2‐(per‐O‐acetyl‐alditol‐l‐yl)‐5‐methylthio{7H‐1,2,4‐triazolo[1,5‐d]tetrazol‐6‐yl}‐1,3,4‐oxadiazoles ( 5_a‐f ). Condensative cyclization of the sugar hydrazones ( 3_a‐f ) by heating with acetic anhydride gave the corresponding 3‐acetyl‐2‐(per‐O‐acetyl‐alditol‐1‐yl)‐2,3‐dihydro‐5‐methylthio{7‐acetyl‐1,2,4‐triazolo[1,5‐d]tetrazol‐6‐yl}‐1,3,4‐oxadiazoles ( 11_a‐f ). De‐O‐acetylation of the acyclo C‐nucleoside peracetates ( 5 and 11 ) with methanolic ammonia afforded the hydrazono lactones ( 7 ) and the acyclo C‐nucleosides ( 12 ), respectively. The structures of new oxadiazole derivatives were confirmed by analytical and spectral data.     

Nitric oxide measurements in biological samples

The crucial role of nitric oxide (NO) in controlling many physiological functions in mammals is now established. To aid understanding this crucial role, sensitive and selective methods for its in vivo and in vitro detection are vital. The unique chemical and physical properties of NO set the tone for its detection strategies. This review summarizes different techniques and methodologies used in measuring NO in biological samples. Those include gas and liquid phase chemiluminescence, electron spin resonance spectroscopy, UV-visible spectroscopy, fluorescence, electrochemical sensors, and reporter cell assay. The principles, applications, merits, and limitations of each technique are discussed.     

Three New Cadinene Derivatives from Xenia Puerto‐Galerae

Chromatographic investigation of an acetone extract of the octocoral Xenia puerto‐galerae afforded three new cadinene sesquiterpenes; 8‐epi‐xenitorin A ( 1 ), 10‐epi‐xenitorin C ( 2 ), and 7‐isopropenyl‐4,10‐dimethyl‐2,3,4,5‐tetrahydronaphthalene ( 3 ), in addition to four known cadinene analogs ( 4 , 11–13 ) and six xenicanes ( 5–10 ). The structures were elucidated through spectroscopic analysis, especially 2D NMR. A biogenetic pathway of 1–3 and analogs was proposed.