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PubMed1995

Cyclodextrins as protein folding aids.

Aggregation of proteins is a frequent occurrence during their transition from random coil to native structure. The influence of cyclodextrins in the refolding of carbonic anhydrase under aggregating conditions was studied. Cyclodextrin prevented formation of protein aggregates during renaturation of carbonic anhydrase. In addition, over 90% of active enzyme was recovered even at protein concentrations as high as 67 microM. The enhanced protein reactivation by cyclodextrins may be due to their ability to bind to hydrophobic sites in protein folding intermediate(s) followed by their subsequent removal as the protein refolds.

Animals↗
PubMed2001

Stereoselective reduction with NADH model BNAH through chiral induction in cyclodextrins.

Stereoselective reductive debromination-cyclopropanation of 2-bromo-1-phenylethylidene-malononitrile and 2-bromo-1-beta-naphthylethylidenemalononitrile by coenzyme NADH model BNAH through chiral induction in cyclodextrins is reported. The matching between substrates and cyclodextrins, the substituent effect, and the effect of cyclodextrin concentration on the optical yields have been investigated.

Cyclodextrins↗
PubMed2004

The HPLC resolution of N-2,4-dinitrophenylated amino acids and peptides stereoisomers on naphthylethylcarbamate-beta-cyclodextrin bonded phase using the acetonitrile-based mobile phase: evidence for the chiral recognition pattern.

A facile method of enantioresolving a variety of alpha-amino acids and peptides on naphthylethylcarbamate-beta-cyclodextrin bonded phases (i.e., SN- and RN-beta-CDs) under the elution of acetonitrile-based mobile phase makes use of 2,4-dinitrofluorobenzene (DNFB) as the tagging reagent, which undergoes nucleophilic substitution by the free amino group in alkaline medium to give a N-2,4-dinitrophenyl (DNP) derivative. The resolution is better obtained on RN-beta-CD phase and fails to reproduce on the intact beta-cyclodextrin bonded phase under the same chromatographic conditions, which strongly suggests that the observed resolution should be due to the interaction of analyte with naphthylethylcarbamate moiety, not with the residual secondary hydroxyl groups on the beta-cyclodextrin.

Acetonitriles↗
PubMed2006

Structures of inclusion complexes of halogenbenzoic acids and alpha-cyclodextrin based on AM1 calculations.

Semi-empirical quantum mechanics calculations using AM1 (Austin Method 1) were carried out for various host-guest combinations of alpha-cyclodextrin and mono-halogen benzoic acids. The energetically favorable inclusion structures were identified. The AM1 results show that alpha-cyclodextrin complexes with mono-halogen benzoic acid acids (where the halogen is chlorine, bromide, iodine) as guest compounds are more stable in the "head first" position than in the "tail-first" position for meta and para isomers while ortho mono-halogen benzoic acids complexes with alpha-cyclodextrin are more stable in "tail-first" position. The calculated structures were found to be in good agreement with those obtained from crystallographic databases.

Benzoic Acid↗
PubMed1992

Distribution of substituents in O-(2-hydroxypropyl) derivatives of cyclomalto-oligosaccharides (cyclodextrins: influence of increasing substitution of the base used in the preparation, and of macrocyclic size.

Samples of O-(2-hydroxypropyl)derivatives of cyclomaltoheptaose (beta-cyclodextrin) with increasing substitution were prepared by withdrawing aliquots at different times from a reaction mixture containing cyclomaltoheptaose and an excess of (S)-propylene oxide in 0.39 M aqueous sodium hydroxide. The distributions of substituents between the different molecules and between the different alpha-D-glucopyranosyl residues in these samples were determined by mass spectrometry and methylation analysis, respectively. The solubilities of the samples and their association constants with phenolphthalein were also determined. The relative reactivities at O-2 and O-3 versus O-6, calculated using Spurlin's equations, decreased with increasing degree of substitution, probably because of steric hindrance. No significant differences were observed when different strong bases were used as promoters of the hydroxypropylation of cyclomaltoheptaose. The hydroxypropylation of cyclomaltohexaose (alpha-cyclodextrin) and cyclomalto-octaose (gamma-cyclodextrin) was briefly investigated.

Carbohydrate Conformation↗
PubMed1994

Separation and characterization of five positional isomers of trimaltosyl-cyclomaltoheptaose (trimaltosyl-beta-cyclodextrin).

Trace amounts of trimaltosyl-cyclomaltoheptaoses (trimaltosyl-beta-cyclodextrins, trimaltosyl-beta CDs) were found in a mixture of maltosyl-cyclomaltoheptaoses (maltosyl-beta-cyclodextrins, maltosyl-beta CDs) prepared from maltose and cyclomaltoheptaose (beta-cyclodextrin, beta CD) through the reverse action of Klebsiella pneumoniae pullulanase. Five positional isomers of trimaltosyl-beta CD were isolated by high-performance liquid chromatography (HPLC) on a reversed-phase column and a graphitized carbon column. For the structural analysis of 6(1), 6(2), 6(3)-, 6(2), 6(5)-, and 6(1), 6(3), 6(5)-tri-O-maltosyl-beta CDs, an enzymic method using glucoamylolysis, followed by hydrolysis with Bacillus subtilis saccharifying alpha-amylase, was applied. Although 6(1), 6(2), 6(4)- and 6(1), 6(2), 6(6)-substituted isomers were indistinguishable by this method, these isomers were distinguished clearly by digestion of branched oligosaccharides produced from each isomer by the aforesaid method, with B. stearothermophilus neopullulanase or with glucoamylase. The resulting hydrolysates were analyzed by HPLC on an amino derivatized column and by fast-atom bombardment spectrometry (FABMS). The chromatographic behavior and spectral data (13C NMR and FABMS) of five positional isomers of trimaltosyl-beta CD are described.

Carbohydrate Conformation↗
PubMed1995

Separation of cyclodextrins and their derivatives by thin-layer and preparative column chromatography.

Cyclodextrins, their derivatives and products of their partial hydrolysis are clearly separated by chromatography on silica gel by mobile phases containing aqueous ammonia and organic solvent (acetonitrile or 1-propanol). This system allows separation of compounds with different numbers of substituents on cyclodextrin, but does not allow the separation of isomers; the system can be used both for thin-layer chromatography and for preparative column chromatography. The isomers in the fraction thus obtained can be in some cases separated, after peracetylation, by chromatography on silica gel using a mobile phase consisting of methanol and dichloromethane. This chromatographic sequence potentially yields derivatives of cyclodextrins in quantities which enable evaluation of their solubilization and biological properties.

Acetylation↗
PubMed1994

High-performance liquid chromatographic separation of cis-trans isomers of proline-containing peptides. II. Fractionation in different cyclodextrin systems.

beta-Cyclodextrin-bonded silica is demonstrated to be a suitable stationary phase for high-performance liquid chromatography of conformational isomers of proline-containing peptides. In contrast to reversed-phase chromatography, the principle of inclusion complexation shows significant selectivities in conformer resolution based on a variety of interactions. New results of inclusion HPLC of biologically active oligopeptides related to beta-casomorphin on stationary phases containing bonded cyclodextrins of different internal diameters indicate a steric discrimination process during the conformer separation. beta-Cyclodextrin used as a mobile phase additive in reversed-phase systems is shown to offer the opportunity to investigate conformational changes using commercially available reversed-phase columns.

Amino Acid Sequence↗
PubMed1990

Cyclodextrin chiral stationary phases for liquid chromatographic separations of drug stereoisomers.

Many active drugs are racemic mixtures. Because the two enantiomers of a racemate often cause different pharmacological responses, the use of optically pure isomers is desirable and may be soon required. Cyclodextrin-bonded silica gel can be used as chiral stationary phase (CSP) in liquid chromatography. The enantiomers of 25 different racemic drugs were separated on such CSPs in the reversed-phase mode. The principal features of the cyclodextrin chiral recognition mechanism are recalled and some information on future trends for cyclodextrin CSPs is provided.

Chromatography, Liquid↗
PubMed1990

Inclusion complexation of doxorubicin and daunorubicin with cyclodextrins.

The interaction of alpha-, beta- and gamma-cyclodextrins with the anthracycline antibiotics doxorubicin and daunorubicin was investigated by LC, circular dichroism (CD) and absorption spectroscopy. All studies were performed in aqueous media at different temperatures and pH values. The anthracyclines complex only with gamma-cyclodextrin. Lineweaver-Burk and Scott's plots were used to calculate the stability constants of the anthracycline-gamma-cyclodextrin inclusion complexes.

Chromatography, High Pressure Liquid↗
PubMed2006

Role of simvastatin and methyl-beta-cyclodextrin [corrected] on inhibition of poliovirus infection.

Cells exposed to simvastatin or to methyl-beta-cyclodextrin show reduced poliovirus infection, without alteration in virus binding or on the kinetics of genome entry, suggesting that the steps which are altered are those post uncoating and genome entry. Reduction of infection by cyclodextrin is reversed by increasing MOI whereas that produced by simvastatin treatment is not, suggesting that the effects on infection are not due to a reduction in cholesterol. The differences in the characteristics of inhibition can be explained by the differential effects of the compounds. Cyclodextrin inhibits the store-operated calcium channels, suggesting that reduction in infection is through translational inhibition. Simvastatin produces vesicles from internal membranes which cannot sustain viral RNA synthesis, reducing infection through reduced transcription. The results indicate that the impact on viral infection by the cholesterol-modifying agents is due to the cellular changes produced rather than due to disruption of the cholesterol-rich domains.

Antiviral Agents↗
PubMed2004

Spectroscopic and electrochemical study of Rose Bengal in aqueous solutions of cyclodextrins.

The interaction of Rose Bengal (RB) in aqueous solution of LiClO4 0.1 M with alpha-cyclodextrin (alpha-CD), hydroxypropyl-beta-cyclodextrins (HP-beta-CD) and hydroxypropyl-gamma-cyclodextrins (HP-gamma-CD) were studied by spectrophotometric measurements. The presence of Induced Circular Signals and the results of the analysis of the modifications in the absorbance spectra of RB produced by the presence of CDs in solution indicate that RB forms inclusion complexes only with HP-beta-CD and with HP-gamma-CD.

Circular Dichroism↗
PubMed2005

Synthesis of creatinine-imprinted poly(beta-cyclodextrin) for the specific binding of creatinine.

An artificial receptor for creatinine was synthesized by the method of molecularly imprinted polymer (MIP). beta-Cyclodextrin was used as a monomer cross-linked with epichlorohydrin in the presence of creatinine, which was a template for the imprinting. Different molar ratios of monomer to template were used to synthesize the polymers so that better specific adsorption ability towards creatinine could be achieved. The results showed that to carry out the polymerization with a molar ratio of monomer to template of 3:2 and monomer to cross-linking agent of 1:10 was proper. N-hydroxysuccinimide and 2-pyrrolinidone were used as the analogues of creatinine in the adsorption experiments of multi-component solutions to reveal the specific recognition ability of the molecularly imprinted poly(beta-cyclodextrin) (poly(beta-CD)) for the template molecule, creatinine. One such detection interference of creatinine was creatine, which also co-exists in serum. Hence, adsorption experiments of creatinine/creatine binary mixture were also carried out to investigate and confirm the specific binding of the creatinine-imprinted poly(beta-cyclodextrin) towards creatinine. The hydroxyl groups of the imprinted poly(beta-CD) was further capped by chlorotrimethylsilane (CTMS) to investigate the interaction between creatinine and the imprinted poly(beta-CD). The adsorption resulting from the mixture solution by MIPs suggested that the creatinine-imprinted poly(beta-CD) demonstrated superior binding effect for the target molecule, creatinine, rather than creatine, N-hydroxysuccinimide and 2-pyrrolinidone.

Binding Sites↗
PubMed2005

Efficient fluorescent sensors of oligopeptides by dithiobis(2-benzoylamide)-bridged bis(beta-cyclodextrin)s: structure in solution, binding behavior, and thermodynamic origin.

Two 6,6'-bis(beta-cyclodextrin)s linked by 2,2'-dithiobis[2-(benzoylamino)ethyleneamino] and 2,2'-dithiobis[2-(benzoylamino)diethylenetriamino] bridges (1 and 2) have been synthesized as cooperative multipoint recognition receptor models for non-aromatic oligopeptides. Their structures in solution and inclusion complexation mechanism are comprehensively investigated by means of circular dichroism, 2D NMR spectra and temperature-dependent fluorescence titrations. The results show that the cooperative 'host-linker-guest' binding mode and the extensive desolvation effect jointly contribute to the guest-induced fluorescence enhancement of bis(beta-cyclodextrin)s. Further examinations on the binding behavior of hosts 1-2 with a series of di- and tri-peptides demonstrate that bis(beta-cyclodextrin) 1 can recognize not only the size/shape of oligopeptides but also the dipeptide sequence, giving an exciting residue selectivity up to 37.5 for Gly-Gly-Gly/Glu-Glu pair and a high sequence selectivity up to 5.0 for Gly-Leu/Leu-Gly pair. These fairly good selectivities are discussed from the viewpoint of cooperative binding, multiple recognition and induced-fit interactions between host and guest.

Fluorescent Dyes↗
PubMed2005

Nonaqueous synthesis of a selectively modified, highly anionic sulfopropyl ether derivative of cyclomaltoheptaose (beta-cyclodextrin) in the presence of 18-crown-6.

A highly anionic cyclomaltooligosaccharide (cyclodextrin, CD) derivative containing sulfopropyl functional groups on the primary face of the CD was synthesized. Heptakis(2,3-di-O-methyl)cyclomaltoheptaose [heptakis(2,3-di-O-methyl)-beta-cyclodextrin] was reacted with 1,3-propane sultone and potassium hydride (KH) in anhydrous tetrahydrofuran in the presence of 18-crown-6 to yield highly substituted potassium heptakis(2,3-di-O-methyl-6-O-sulfopropyl)cyclomaltoheptaose [heptakis(KSPDM)-beta-CD] with an average degree of substitution (DSCE) of 6.9 as determined by inverse detection capillary electrophoresis (CE). The principal species in the product is the fully substituted heptakis(KSPDM)-beta-CD. Complete NMR assignments of the hydrogen and carbon atoms are made using a combination of gCOSY and gHSQC. In the absence of 18-crown-6, the reaction generates a mixture of multiply charged derivatives with average DSCE of 4.1. The possible roles of the crown ether in the reaction are discussed. The ROESY NMR spectrum of the inclusion complex that forms between heptakis(KSPDM)-beta-CD and 2-naphthoic acid in D2O reveals that 2-naphthoic acid inserts with the carboxyl group toward the derivatized primary rim of the cyclodextrin.

Anions↗
PubMed2005

Solubility of cyclomaltooligosaccharides (cyclodextrins) in H2O and D2O: a comparative study.

Cyclomaltooligosaccharides (cyclodextrins, CDs) are cyclic oligomers having six, seven, or eight units of alpha-D-glucose, named as cyclomaltohexaose (alpha-CD), cyclomaltoheptaose (beta-CD) and cyclomaltooctaose (gamma-CD), respectively. The molecule of CD has a cavity in which the interior is hydrophobic relative to its outer surface. The solubility of cyclodextrins in water is unusual, as an irregular trend is observed in the series of the cyclic oligomers of glucose. beta-CD is at least nine times less soluble than the others CDs. This intriguing behavior has been investigated, and some interesting explanations in terms of the effect caused by CD on the water lattice structure have been proposed. In this work a comparative study on the solubility of alpha, beta, and gamma-cyclodextrins was carried out in H2O and D2O and reveals a much lower solubility of the three CDs in D2O. The solid-phase structure of the CDs in equilibrium with the solution is quite similar with both solvents. The results are discussed in terms of the CD molecular structure and the differences in the hydrogen bonds formed between H2O and D2O.

Cyclodextrins↗
PubMed2006

The crystal structure of the 1:1 inclusion complex of beta-cyclodextrin with benzamide.

The 1:1 inclusion complex of beta-cyclodextrin and benzamide was prepared and characterized by single crystal X-ray diffraction, PXRD, TGA, and IR. This complex crystallizes in the monoclinic P2(1) space group with unit cell constants a=15.4244(16), b=10.1574(11), c=20.557(2)A, beta=110.074(2) degrees , V=3025.1(6)A(3). The guest molecule projects into the beta-cyclodextrin cavity from the primary hydroxyl side. The amide group protrudes from the primary hydroxyl side and forms hydrogen bonds with the adjacent beta-cyclodextrin molecule. There are six crystallized water molecules, which play crucial roles in crystal packing.

Benzamides↗
PubMed2005

Non-aqueous capillary electrophoretic enantiomer separations using the tetrabutylammonium salt of heptakis(2,3-O-diacetyl-6-O-sulfo)-cyclomaltoheptaose, a single-isomer sulfated beta-cyclodextrin highly-soluble in organic solvents.

The tetrabutylammonium salt of heptakis(2,3-di-O-acetyl-6-O-sulfo)-cyclomaltoheptaose, a single-isomer sulfated beta-cyclodextrin that is adequately soluble in a number of protic and aprotic polar solvents was synthesized on the large scale and used for the capillary electrophoretic separation of the enantiomers of weak bases in acidic acetonitrile background electrolytes. The effective mobilities and separation selectivities observed for these analytes followed trends similar to those found with other single-isomer sulfated cyclodextrins in acidic methanol background electrolytes. Enantiomer separations obtained with the tetrabutylammonium and sodium salts of heptakis(2,3-di-O-acetyl-6-O-sulfo)-cyclomaltoheptaose were different indicating, for the first time, that selection of the counter ion of the single-isomer sulfated cyclodextrin is also of importance for the separation of enantiomers.

Buffers↗