A rigorous framework to interpret water relaxivity. The case study of a Gd(III) complex with an alpha-cyclodextrin derivative.

We present a general theoretical framework suitable for an economical, but rigorous, analysis of the relaxivity and EPR data of paramagnetic metal complexes. This framework is based on the so-called Grenoble method that properly accounts for the fluctuations of the "static" zero-field splitting Hamiltonian and avoids the misinterpretation of experimental data, which occurs with the Solomon, Bloembergen, and Morgan (SBM) formalism and may lead to erroneous conclusions. The applicability of the SBM approximation is discussed.

[Per(6-deoxy) derivative of beta-cyclodextrin (B6): physicochemical characterization, haemolytic activity and membrane properties].

Natural beta-cyclodextrin bears an internal crown consisting of six primary alcohol groups. Their removal leads to per(6-deoxy)beta-cyclodextrin (B6). The physicochemical properties of B6 and its interactions with membranes were investigated to give an evaluation of haemolytic activity and complexing properties of this chemical species.

Hexakis (3,6-anhydro)-tetrakis[2(I,II,IV,V)-O-(2-ethoxyethyl)] derivatives of (3,6-anhydro)-alpha-cyclodextrin exhibits novel cation affinities and tensioactive properties on membranes.

The synthesis of hexakis (3,6-anhydro)-tetrakis[2(I,II,IV,V)-O-(2-ethoxyethyl)] cyclomaltohexaose (AEOE) was designed to obtain cation complexing properties. 1H NMR study showed ionic radius dependence of AEOE cation affinity, markedly observed for Cs+ and Rb+. Besides, AEOE was found haemolytic (HC50 = 9 mM) and superficial tension measurements revealed positive tensio active properties.

Cerebral blood volume quantification in a C6 tumor model using gadolinium per (3,6-anhydro) alpha-cyclodextrin as a new magnetic resonance imaging preclinical contrast agent.

In magnetic resonance imaging (MRI), cerebral blood volume (CBV) quantification is dependent on the MRI sequence and on the properties of the contrast agents (CAs). By using the rapid steady-state T(1) method, we show the potential of gadolinium per (3,6-anhydro) alpha-cyclodextrin (Gd-ACX), a new MRI paramagnetic CA (inclusion complex of Gd(3+) with per (3,6-anhydro)-alpha-cyclodextrin), for the CBV quantification in the presence of blood-brain barrier lesions. After biocompatibility and relaxivity experiments, in vivo experiments on rats were performed on a C6 tumor model with 0.

Physicochemical properties and membrane interactions of per(6-desoxy-6-halogenated) cyclodextrins.

Per(6-iodo-6-desoxy) cyclodextrins are synthesis intermediates used in the design of the cation chelating per(3,6-anhydro) cyclodextrins. The modifications of the properties of these molecules resulting from the nature of the halogen substituant and also the number of osidic building blocks were investigated by varying both factors, using 1H and 31P-NMR and EPR spectroscopies. These nearly water insoluble molecules exhibits no complexing properties (for both ionic and apolar structures) but can be partially solubilized in micelles of detergent (sodium dodecyl sulfate) and also in phospholipid vesicles.

Inclusion complexes of trivalent lutetium cations with an acidic derivative of per(3,6-anhydro)-alpha-cyclodextrin.

The cyclodextrin derivative (hexakis (2-O-carboxymethyl-3,6-anhydro)-alpha-cyclodextrin) forms mono- and bimetallic complexes with lutetium(III) in aqueous solution; the X-ray structure of the binuclear complex [Lu2(ACX)(H2O)2] is the first example of a lanthanide-cyclodextrin inclusion complex.

Hydrolytic properties of per (3,6-anhydro, 2-O-carboxymethyl) alpha cyclodextrin complexes of Ce (III) and Eu (III): application to soman (GD) degradation.

Per (3,6-anhydro-2-O-carboxymethyle) alpha-cyclodextrin ([ACX]) is a polydentate analog of EDTA, a well-known cation chelating reagent. ACX exhibits strong affinities in vitro for uranyl, cobalt and also for lanthanids such as Europium and Cerium. The hydrolytic activities of ACX-Eu and ACX-Ce complex were directly tested on an organophosphorous compound: the neurotoxic Soman (GD), an inhibitor of acetylcholinesterase (ACHE from rat brain).

[In vitro uranyle affinity of per (3,6-anhydro-2-O-carboxyméthyle)-alpha-cyclodextrin and conditions required for in vivo application].

Per (3.6-anhydro-2-O-carboxymethyle)- alpha-cyclodextrin ([1]) is a polydentate analog of EDTA, a well-known cation chelating reagent. [1] exhibits strong affinities in vitro for lanthanids, cobalt and also for uranyl cations.

Is uranyl scavenger hexakis(3,6-anhydro) tetrakis(2A,B,D,E-O-octyl) cyclomaltohexaose (OCT) relevant with biosystems?

Hexakis(3,6-anhydro)tetrakis(2A,B,D,E-O-octyl) cyclomatohexaose (OCT) has been recently shown as a powerful cryptant for lead, mercury, and especially for uranyl. As previous results have been obtained in an organic solvent (methanol), a similar evaluation of OCT complex formation was achieved in aqueous medium and in the presence of membrane-mimicking systems such as phospholipid vesicles, liposomes and micelles. It was found that OCT, while completely insoluble in water, forms solid gel structures when in equimolar mixtures of water and methanol.

Interaction of per 3,6-anhydro-alpha cyclodextrins (alpha 36CD) and lead-alpha 36CD complex with biological systems.

The interactions of per (3,6 anhydro) alpha cyclodextrin (alpha 36CD) and of lead-alpha 36CD complex with biological systems were tested by NMR, ESR and electronic microscopy using erythrocytes and model membranes. It was found that the haemolytic activity of alpha 36CD alone was seven fold lower than that of natural alpha cyclodextrin (evaluated by the concentration inducing 50% haemolysis, DH50 = 35 mM). Conversely, the formation of the complex resulted in an increase of haemolytic properties, with DH50 of 1 mM.

Mechanism of alpha-cyclodextrin induced hemolysis. 2. A study of the factors controlling the association with serine-, ethanolamine-, and choline-phospholipids.

A nuclear magnetic resonance (NMR) spectroscopy and molecular modeling study of the interaction between alpha-cyclodextrin (alpha-CD) and phospholipids with serine, ethanolamine, or choline headgroups is presented. The experimental approach is based on 31P and 1H NMR measurements on small unilamellar vesicles (SUV), multilamellar systems (MLV), and aqueous suspensions of lipids using a direct complex preparation with alpha-CD. Molecular dynamics computer simulations are used to investigate the trajectory of alpha-CD in the vicinity of a membrane surface and the influence of the charge and dipole moment of the phospholipid headgroups.

Isothiocyanates and cyclic thiocarbamates of alpha,alpha'-trehalose, sucrose, and cyclomaltooligosaccharides.

6,6'-Dideoxy-6,6'-diisothiocyanato-alpha,alpha'-trehalose (4), 6-deoxy-6-isothiocyanato-alpha-D-fructo-furanose beta-D-fructopyranose 1,2':2,1'-dianhydride (11), 6,6'-dideoxy-6,6'-diisothiocyanatosucrose (16), and per(6-deoxy-6-isothiocyanato)-cyclomaltohexaose (23), -cyclomaltoheptaose (27), and -cyclomaltooctaose (31) have been prepared in high yield by reaction of the corresponding amino sugars with thiophosgene. In the absence of base, all isothiocyanates were stable and could be stored and acetylated without decomposition. In the presence of triethylamine, 6,6'-dideoxy-6,6'-diisothiocyanato-alpha,alpha'-trehalose underwent intramolecular cyclisation involving HO-4 to give the corresponding bis(cyclic thiocarbamate).

Incorporation of sulphonated cyclodextrins into polypyrrole: an approach for the electro-controlled delivering of neutral drugs.

The electro-controlled delivery of drugs based on the doping-dedoping mechanism of Electro-Conducting Polymers is restricted to charged substances acting as dopants. In order to overcome this limitation, this study presents an approach where the trapping/delivering is based on host-guest interaction. As an example of a neutral guest, the molecule N-methylphenothiazine (NMP) is encapsulated in the host, heptasulphonated beta-cyclodextrin (beta-CDSO3-), which is tailor-made to dope PPy.

Difructose dianhydrides from sucrose and fructo-oligosaccharides and their use as building blocks for the preparation of amphiphiles, liquid crystals, and polymers.

Controlled selective protonic activation of the fructosyl moiety in sucrose and fructo-oligosaccharides, with pyridinium poly (hydrogen fluoride) at 20 degrees C, yielded either the kinetic product alpha-D-fructofuranose beta-D-fructofuranose 1,2':2,1'-dianhydride (1), or its thermodynamically more stable isomer alpha-D-fructofuranose beta-D-fructopyranose 1,2':2,1'-dianhydride (2), depending on the hydrogen fluoride-pyridine ratio. A similar reaction was performed with 6,6'-dichloro-6,6'-dideoxysucrose, or 6,6'-dideoxy-6,6'-diiodosucrose, using a slightly higher ratio of HF, resulting in the corresponding 6-deoxy-6-halo-alpha-D-fructofuranose 6'-deoxy-6'-halo-beta-D-fructofuranose 1,2':2,1'-dianhydride derivatives. Both 6,6'-dihalides were converted, upon action of the appropriate nucleophile, into the difructofuranose dianhydride derivatives bearing the 6,6'-di-S-heptyl-6,6'-dithio, 6,6'-diazido-6,6'-dideoxy and then 6,6'-diamino-6,6'-dideoxy functionalities.

A convenient access to beta-(1-->4)-linked 2-amino-2-deoxy-D-glucopyranosyl fluoride oligosaccharides and beta-(1-->4)-linked 2-amino-2-deoxy-D-glucopyranosyl oligosaccharides by fluorolysis and fluorohydrolysis of chitosan.

beta-(1-->4)-Linked 2-amino-2-deoxy-D-glucopyranosyl oligosaccharides, in the form of their alpha-glucopyranosyl fluorides at the reducing end, were obtained by fluorolysis of chitosan in anhydrous hydrogen fluoride at room temperature. The average dp depended on the reaction time and was conveniently monitored by 13C NMR spectroscopy, using the signal ratios for beta-(1-->4) bonded C-1 at approximately 98.5 ppm and the C-1 doublet for the terminal glycosyl fluoride moiety at approximately 104 ppm.

Hydrogen fluoride-mediated synthesis of 1-thiotrehaloses involving reaction of D-glucose with hydrogen sulfide.

Hydrogen sulfide reacted with D-glucose in hydrogen fluoride solution to yield preponderantly alpha,alpha-1-thiotrehalose, beta,beta-1-thiotrehalose, and the alpha,beta anomer. Conditions were found under which the thiotrehaloses were obtained in the respective proportions of 8:5:5.

Steric and electronic effects in the formation of dihexulose dianhydrides. Reaction of racemic sorbose in anhydrous hydrogen fluoride and a facile synthesis of D-sorbose.

Treatment of DL-sorbose with anhydrous hydrogen fluoride gave a high yield of alpha-D-sorbopyranose alpha-L-sorbopyranose 1,2':2,1'-dianhydride. Similarly a mixture of D-fructose and D-sorbose gave a good yield of beta-D-fructopyranose alpha-D-sorbopyranose 1,2':2,1'-dianhydride. The formation of these products compared to the more complicated mixtures of compounds obtained by treatment of L-sorbose or D-fructose with hydrogen fluoride, is discussed in terms of conformations, and steric and electronic factors.

Chitin oligosaccharides as elicitors of chitinase activity in melon plants.

Chitin oligosaccharides elicited chitinase activity in melon plants. Hexamer to nonamer were the most efficient elicitors: hexamer for maximal stimulation of colorimetrically assessed chitinase activity, heptamer for maximal stimulation of radiochemically assessed chitinase activity. Chitinase elicitation was a rapid response to these elicitors: it occurred within 6 hours after treatment and was maximal at 12-24 hours.