[Per(6-deoxy) derivative of beta-cyclodextrin (B6): physicochemical characterization, haemolytic activity and membrane properties]. / Caractérisation physicochimique du dérivé amphiphile per(6-déoxy) de la bêta-cyclodextrine (B6) et étude de son activité hémolytique et de son action vis-à-vis des membranes.

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. This was achieved by using surface tension and haemolytic activity (i.e.DH50 determination, the concentration inducing 50% haemolysis) measurements,1H-31P-NMR and EPR spectroscopies. Whereas B6 solubility in the water is close to that of natural beta CD (about 5 g/L at 20 degrees C) and exhibits amphiphilic properties greater than those of beta CD (log P: -1.36 at 300 K), B6 forms micelles in aqueous solution of 20 molecules, even at low concentration 0.8mM. In addition, B6 exhibits tensioactive properties leading to solubilization and even, in some cases orientation of synthetic membranes. Although no complex formation with membrane components was observed, NMR and ESR showed interactions with the surface of the membrane. Subsequently, B6 exhibits an important haemolytic activity, whose mechanism, different from that of beta CD, is discussed.

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. Dipolar connectivity (nOesy) NMR experiments show that they are embedded at the chain level of the micelles/vesicles, without any inclusion complex formation. Changing the number of glucose building blocks (6,7 or 8) or/and the nature of the halogen nuclei at the positions 6 strongly modify cyclodextrin affinities and membrane interactions. For instance the per(6-bromo-6-desoxy)-cyclomaltohexaose (ABR) and -cyclomaltoheptaose (BBR) exhibit a selective affinity for cobalt (apparent Ka of 2500 and 790M(-1), respectively). In terms of interactions with membranes, alpha derivatives induce sterical hindrance at the phosphorus level while destructuring the chains. Other derivatives are located deeper and rigidify the most superficial part of the chain, suppressing the jump in membrane fluidity at transition temperature.

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. A 31P and 2HNMR study of phospholipid dispersions (dimyristoyl phosphatidyl cholin, DMPC) in the presence of AEOE was performed; it was found that, beside the typical lineshape of phospholipid bilayers, two new NMR lines were detected in the presence of AEOE: (a) an isotropic line consistent with a detergent effect (b) another isotropic resonance of 1 Hz linewidth over phase transition temperature (298 K), indicating a true solubilization. Coupling constant measurements confirmed that the main conformation at the polar head group level was close to that observed in chloroform/methanol solution. It was finally concluded that AEOE could form true solutions of DMPC, similarly to those induced by diethyl ether interactions with membranes, while giving soluble complexes.

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). It was found a three fold reduction of soman activity when measured in the presence of Ce-ACX complex. Conversely, Eu-ACX effect did not result in soman inhibition variation under physiological conditions. It is suggested that, considering usual organometallic complex of cyclodextrin, such direct complexes would be of interest in the design of pseudo-enzyme systems for phosphoester hydrolysis.

[In vitro uranyle affinity of per (3,6-anhydro-2-O-carboxyméthyle)-alpha-cyclodextrin and conditions required for in vivo application]. / Affinité in vitro de la per (3,6-anhydro-2-O-carboxyméthyle)-alpha-cyclodextrine pour les uranyles et conditions requises en vue d'une application in vivo.

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. Hence, a 1:1 stoechiometry and a high affinity for uranyle (6

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. Moreover, OCT exhibits detergent properties. Finally, OCT was successfully introduced in detergent solutions while keeping. Uranyl complexing properties. Possible applications of such models were also discussed.

1H-NMR study of heavy metals complexation with hexakis(3,6-anhydro) tetrakis(2A,B,D,E-O-octyl) cyclomaltohexaose (OCT).

The selection of the cations bound by hexakis (3,6-anhydro) tetrakis (2A,B,D,E-O-octyl) cyclomatohexaose (OCT) was performed by thin layer chromatography. The three cations selected, UO(2)2+, Pb2+ and Hg2+ were then studied by 1H-NMR. A 2:1 OCT/cation stoichiometry was identified in the cases of UO(2)2+ and Pb2+. While UO(2)2+ binding (logK around 6) followed a fast exchange kinetics, a slow or intermediate complexation was found with Pb2+ (logK = 5.6) and Pb2+, respectively. In the latter case, the poor solubility of Hg2+ precluded to propose neither a stoichiometry nor an estimation of the affinity constant.

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. The mechanism proposed was an increased membrane diffusion by endocytosis of the complex, leading to higher amounts of intracellular lead.

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. These factors of charge and orientation of dipole moment seem to play a key role in the interaction of phospholipids with alpha-CD and reflect very well the experimentally observed selectivity of the phospholipid -alpha-CD approach. However, with this approach, there is no evidence for the formation of a complex with the phospholipid headgroup (except for phosphatidylinositol) that results from electrostatic forces. Rather, after a possible extraction of the lipid from the membrane, a classical inclusion of the sn-2 chain in the cavity of alpha-CD occurs. This step depends on the alkyl chain length and saturation state of the lipids as well as on their organization (i.e., as vesicles or dispersions). Based on our results, chemical modifications of the alpha-CD molecule to control the hemolytic properties of alpha-CD are discussed.

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). The product of cyclisation at a single glucopyranosyl unit was obtained in the treatment of the above diisothiocyanate with mixed (H+, HO-) ion-exchange resin. Under identical reaction conditions, 6,6'-dideoxy-6,6'-diisothiocyanatosucrose yielded exclusively the product of intramolecular cyclisation at the D-glucopyranosyl moiety, while derivatives of alpha-D-fructofuranose beta-D-fructopyranose 1,2':2,1'-dianhydride and cyclomaltooligosaccharides remained unchanged.

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. The original synthetic method for beta-CDSO3- is based on sulphonation of the periodated beta-CD in the phase transfer medium. As a consequence of their size and of their multicharged character, beta-CDSO3-s are fixed dopants. The stability of the beta-CDSO3- entrapment is checked by Optical Beam Deflection (mirage effect) measurements. The ionic movements associated with the switching of the beta-CDSO3- doped PPy (PPy+, beta-CDSO3-) film appear to be mainly due to cations with this technique. Cyclic voltammetry experiments confirm the entrapment of neutral NMP by simply dipping the PPy+, beta-CDSO3- film in a CH3CN solution containing NMP. Repeated electrochemical cycling of such a reservoir electrode indicates the progressive elimination of NMP from the (PPy+, beta-CDSO3- [NMP]) film.

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. 6-Chloro-6-deoxy and 6-deoxy-6-iodo derivatives of 2 were also prepared by direct halogenation, and further converted into the 6-S-heptyl-6-thio, 6-azido-6-deoxy and then 6-amino-6-deoxy derivatives of 2. Reaction of chloromethyloxirane with 1 or 2 yielded hydrophilic polymers. The 6,6'-di-S-heptyl-6,6'-dithio derivative of 1 displayed liquid crystal properties. The 6,6'-dideoxy-6,6'-diiodosucrose precursor was prepared by the reaction of Garegg's iodine-imidazole-triphenylphosphine reagent with sucrose in N,N-dimethylformamide solution.

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. Preparative fractionation of dp 2-11 glycosyl fluoride oligosaccharides, obtained after 18 h of fluorolysis, was achieved by gel-permeation chromatography on Bio-Gel P-4 with aqueous acetic acid-ammonium acetate as eluent. Hydrolysis of the anomeric fluoride, with either aqueous perchloric acid, or by a sequence involving formation of the C-2 N-trifluoroacetate and subsequent simultaneous hydrolysis of the glycosyl fluoride and the amide substituent with aqueous methanol, yielded the free beta-(1-->4)-linked 2-amino-2-deoxy-D-glucopyranosyl oligosaccharides which were separated, for dp 2-11, by the same gel-exclusion technique. Both oligosaccharide series, either free or in the form of their alpha-glycopyranosyl fluorides, were fully characterized.

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.

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.

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. In addition, chitinase induction in melon plants by these oligosaccharides was both local and systemic.