Efficient preparation of carbohydrate- and related polyol-amphiphiles by hydrazone ligation

The hydrazone ligation can be used to couple clustered-glycosides or glycomimetics functionalized with a hydrazino group with lipophilic glyoxylyl acid derivatives to give the corresponding amphiphiles in high yield and purity.     

Cohomological properties of the quantum shuffle product and application to the construction of quasi-Hopf algebras

For a commutative algebra the shuffle product is a morphism of complexes. We generalize this result to the quantum shuffle product, associated to a class of non-commutative algebras (for example all the Hopf algebras). As a first application we show that the Hochschild-Serre identity is the dual statement of our result. In particular, we extend this identity to Hopf algebras. Secondly, we clarify the construction of a class of quasi-Hopf algebras.     

On the preparation of carbohydrate-protein conjugates using the traceless Staudinger ligation

[reaction: see text] The nature of a linker used for preparing glycoconjugate vaccines is of utmost importance as it may lead to immunogenic biomolecules. We report the conjugation of carbohydrate haptens to protein carriers leading to potential vaccines using the traceless Staudinger ligation. The ligation relies on the selective transfer of a phosphane substituent to an azide to form a native amide bond in the final product upon release of an oxidized phosphane byproduct. We designed new phosphino-functionalized cross-linkers suitable for protein carrier derivatization. We evaluated their utility in preparing conjugates using both synthetic and purified bacterial carbohydrates. The use of a borane-protected phosphane which is deprotected at the time of the ligation reaction led to the best results observed thus far in terms of stability toward oxidation and reactivity.     

Digests or extracts?—Some interesting but conflicting results for three widely differing polluted sediment samples

Three sets of samples have been investigated in some detail. One set is from a river polluted by mine workings, containing substantial levels of Fe, Mn,Cu, Zn and Ni with traces of many other metals. The second set consists of typical estuarine sediments contaminated from a wide range of industrial sources, and the third set consists of oily drilling cuttings from the sea bottom in the vicinity of a North Sea oil production platform.These samples have been subjected to treatment 1) with EDTA at two different pH's (extracts) 2) with HNO₃/H₂O₂ 3) with HNO₃/HCl and 4) with HNO₃/HCl/HF (digests). EDTA recoveries, compared toaqua regia digests, are often very reproducible, not dependent on pH, and usually significantly low. Nitric/peroxide andaqua regia digests often give very close results suggesting that these are meaningful values indicating the maximum levels of polluting metals in the sediments. However, the triple acid digest with HF does sometimes give higher values (and reasonable agreement for CRM's such as MESS-1) but with poorer reproducibility.     

Single-run analysis of retinal isomers, retinol and photooxidation products by high-performance liquid chromatography

A high-performance liquid chromatographic (HPLC) procedure was developed to allow the rapid separation, in a single run, of a mixture of the main retinal isomers (all-trans, 13-cis, 9-cis), all-trans-retinol, and of the two major photooxygenated photoproducts (5,8-peroxyretinal and 5,6-epoxyretinal). The mixture was separated by HPLC on an octadecyl (ODS) column with 16% (v/v) diethyl ether in hexane as mobile phase and anthracene as the internal standard. A commercial type cosmetic formulation containing 0.05% all-trans-retinal was analyzed successfully for this analyte.     

Synthesis of new crosslinkable co-polymers containing a push-pull zinc porphyrin for non-linear optical applications

In this paper, the synthesis of a crosslinkable co-polymer containing new push-pull arylethynyl zinc porphyrins is described. The synthesis of porphyrin chromophores, analogous to Therien's porphyrin (J. Am. Chem. Soc.1996, 118, 1497-1503) functionalized with a methacrylic polymerizable group and a carboxylic acid crosslinking group was achieved with a new synthetic procedure leading to a higher overall yield compared to what was previously reported in the literature for similar and simpler structures. Radical copolymerization of the porphyrin chromophore with glycidyl methacrylate has then been carried out with success. This work opens a perspective on the possibility to integrate porphyrinic chromophore with high first-order molecular quadratic hyperpolarizability coefficient in opto-electronic devices.     

Photoinduced electron transfer in platinum(II) terpyridinyl acetylide complexes connected to a porphyrin unit

A series of six new dyads consisting of a zinc or magnesium porphyrin appended to a platinum terpyridine acetylide complex via a para-phenylene bisacetylene spacer are described. Different substituents on the 4' position of the terpyridinyl ligand were explored (OC7H15, PO3Et2, and H). The ground-state electronic properties of the dyads are studied by electronic absorption spectroscopy and electrochemistry, and they indicate some electronic interactions between the porphyrin subunit and the platinum complex. The photophysical properties of these dyads were investigated by steady-state, time-resolved, and femtosecond transient absorption spectroscopy in N,N-dimethylformamide solution. Excitation of the porphyrin unit leads to a very rapid electron transfer (2-20 ps) to the nearby platinum complex followed by an ultrafast charge recombination, thus preventing any observation of the charge separated state. The variation in the rate of the photoinduced electron transfer in the series of dyads is consistent with Marcus theory. The results underscore the potential of the para-phenylene bisacetylene bridge to mediate a rapid electron transfer over a long donor-acceptor distance.     

Analysis of serotonin in brain microdialysates using capillary electrophoresis and native laser-induced fluorescence detection

Serotonin or 5-hydroxytryptamine (5-HT) is a major neurotransmitter in the central nervous system. In this work, a method for analyzing 5-HT in brain microdialysis samples using a commercially available capillary electrophoresis (CE) system has been developed. A pH-mediated in-capillary preconcentration of samples was performed, and after separation by capillary zone electrophoresis, native fluorescence of 5-HT was detected by a 266 nm solid-state laser. The separation conditions for the analysis of 5-HT in standard solutions and microdialysates have been optimized, and this method has been validated on both pharmacological and analytical bases. Separation of 5-HT was performed using a 80 mmol/L citrate buffer, pH 2.5, containing 20 mmol/L hydroxypropyl-beta-cyclodextrin (HP-beta-CD) and +30 kV voltage. The detection limit was 2.5 x 10(-10) mol/L. This method allows the in vivo brain monitoring of 5-HT using a simple, accurate CE measurement in underivatized microdialysis samples.     

Marine Exopolysaccharide Complexed With Scandium Aimed as Theranostic Agents

(1) Background: Exopolysaccharide (EPS) derivatives, produced by Alteromonas infernus bacterium, showed anti-metastatic properties. They may represent a new class of ligands to be combined with theranostic radionuclides, such as ⁴⁷Sc/⁴⁴Sc. The goal of this work was to investigate the feasibility of such coupling. (2) Methods: EPSs, as well as heparin used as a drug reference, were characterized in terms of molar mass and dispersity using Asymmetrical Flow Field-Flow Fractionation coupled to Multi-Angle Light Scattering (AF4-MALS). The intrinsic viscosity of EPSs at different ionic strengths were measured in order to establish the conformation. To determine the stability constants of Sc with EPS and heparin, a Free-ion selective radiotracer extraction (FISRE) method has been used. (3) Results: AF4-MALS showed that radical depolymerization produces monodisperse EPSs, suitable for therapeutic use. EPS conformation exhibited a lower hydrodynamic volume for the highest ionic strengths. The resulting random-coiled conformation could affect the complexation with metal for high concentration. The LogK of Sc-EPS complexes have been determined and showing that they are comparable to the Sc-Hep. (4) Conclusions: EPSs are very promising to be coupled with the theranostic pair of scandium for Nuclear Medicine.