sodium-dodecyl-sulfate and betadex

A simple, low-cost and label-free strategy for detecting lithocholic acid (LCA) was designed at the liquid crystals (LCs)/aqueous interface via competitive host-guest inclusion. In this method, sodium dodecyl sulfate (SDS) was initially adsorbed on the fluid interface and induced LCs to adopt the homeotropic ordering. Inclusion complexation of SDS and β-cyclodextrin (β-CD) disturbed interaction between LCs and SDS and evoked LCs to keep a tilted alignment. When injecting LCA into the mixed solution of SDS and β-CD, SDS excluded from the cavity of β-CD by competitive host-guest inclusion and could be re-adsorbed at the LCs/aqueous interface, resulting in the orientational transition of LCs from tilted to homeotropic state. Correspondingly, a bright-to-dark optical response was observed under polarized optical microscope (POM). The as-prepared LCs-based sensor could detect LCA as low as about 2 μM in aqueous solution. Moreover, the practicability of the approach was validated by monitoring the known amount of LCA in human urine. This work offers an appealing approach for the detection of LCA which has a great potentiality in clinical diagnosis.

Topics: Adsorption; beta-Cyclodextrins; Biosensing Techniques; Humans; Limit of Detection; Liquid Crystals; Lithocholic Acid; Microscopy, Polarization; Sodium Dodecyl Sulfate; Water

A liquid crystals (LCs)-based sensing platform was constructed for simple, convenient, inexpensive and label-free detection of α-amylase, associated with disruption of host-guest interaction between sodium dodecyl sulphate (SDS) and β-cyclodextrin (β-CD). In the presence of SDS/β-CD solution, a bright optical image was observed corresponding to the tilted anchoring of LCs at the aqueous/LCs interface. While a black optical appearance was captured when the pre-incubated mixture containing SDS/β-CD complex and ≥0.0001 mg/mL α-amylase was transferred onto the fluid interface. The reason for this difference is that α-amylase could hydrolyze β-CD and subsequently destroy the host-guest interaction between SDS and β-CD. SDS molecules escaping from the cavity of β-CDs were adsorbed at the aqueous/LCs interface, which evoked the homeotropic state of LCs. In the case of α-amylase below 0.0001 mg/mL, a bright optical image was observed. Based on these, detection of α-amylase could be achieved and its detection limit was ∼0.0001 mg/mL (15 U/L). Moreover, this sensing platform was successfully utilized to monitor α-amylase in the body fluids, such as urine and saliva, indicating its potentiality in the relevant clinical diagnosis.

Topics: alpha-Amylases; beta-Cyclodextrins; Biosensing Techniques; Calibration; Humans; Limit of Detection; Liquid Crystals; Saliva; Sodium Dodecyl Sulfate

An alternative method for simultaneous baseline separation of α and β-acids homologues and isomers in hop by CD-MEKC with UV detection was proposed. The optimized background electrolyte was composed of 30 mmol/L sodium tetraborate solution, 45 mmol/L sodium dodecyl sulfate, 20 mmol/L β-cyclodextrin and 10% v/v acetonitrile. The instrumental conditions were evaluated by using a 3

Topics: Acids; beta-Cyclodextrins; Borates; Chromatography, Micellar Electrokinetic Capillary; Electrophoresis, Capillary; Humulus; Isomerism; Sodium Dodecyl Sulfate; Spectrophotometry, Ultraviolet

Proteins can readily assemble into rigid, crystalline and functional structures such as viral capsids and bacterial compartments. Despite ongoing advances, it is still a fundamental challenge to design and synthesize protein-mimetic molecules to form crystalline structures. Here we report the lattice self-assembly of cyclodextrin complexes into a variety of capsid-like structures such as lamellae, helical tubes and hollow rhombic dodecahedra. The dodecahedral morphology has not hitherto been observed in self-assembly systems. The tubes can spontaneously encapsulate colloidal particles and liposomes. The dodecahedra and tubes are respectively comparable to and much larger than the largest known virus. In particular, the resemblance to protein assemblies is not limited to morphology but extends to structural rigidity and crystallinity-a well-defined, 2D rhombic lattice of molecular arrangement is strikingly universal for all the observed structures. We propose a simple design rule for the current lattice self-assembly, potentially opening doors for new protein-mimetic materials.

Topics: beta-Cyclodextrins; Capsid; Capsid Proteins; Liposomes; Micelles; Microscopy, Atomic Force; Microscopy, Electron, Transmission; Molecular Mimicry; Molecular Structure; Nanostructures; Scattering, Radiation; Sodium Dodecyl Sulfate; X-Ray Diffraction

Sodium dodecyl sulphate (SDS) including β-cyclodextrin (β-CD) (β-CDSDS) was used to detect cholesterol at the 4-cyano-4'-pentylbiphenyl (5CB)/aqueous interface in transmission electron microscopy (TEM) grid cells. The β-CD acts as a host for SDS (guest). The guest SDS enclosed within the β-CD cavity was replaced with cholesterol by injecting cholesterol solution into the TEM cell at concentrations greater than 3 μM. The replacement of SDS with cholesterol was confirmed by pH measurement and high performance liquid chromatography (HPLC). The SDS excluded from the β-CD altered the planar orientation of the 5CB confined within the TEM grid cell to a homeotropic orientation. This planar-to-homeotropic transition was observed using a polarized optical microscope under crossed polarizers. This convenient TEM grid cell provides a new method for the selective detection of cholesterol without immobilization of the detecting receptors (enzyme, antibody, or aptamer) or the use of sophisticated instruments.

Topics: beta-Cyclodextrins; Biosensing Techniques; Cholesterol; Chromatography, High Pressure Liquid; Hydrogen-Ion Concentration; Liquid Crystals; Microscopy, Electron, Transmission; Sodium Dodecyl Sulfate; Water

The mechanism by which the protein bovine serum albumin undergoes unfolding induced by the anionic surfactant sodium dodecyl sulphate (SDS) and then the subsequent refolding brought in by β-Cyclodextrin (β-CD) was studied by steady-state fluorescence, time resolved measurements and Circular Dichroism (CD) spectroscopy. The prominent findings of this investigation are (i) SDS unfolds the protein in a sequential manner passing through three different phases of binding of SDS followed by a saturation phase; (ii) the refolding process is initiated through inclusion/removal of SDS molecules by β-CD and hence this also seems to happen in a phased manner; (iii) the process of refolding seems to be reversible to the unfolding process but the protein does not regain all its structure on refolding; (iv) however, CD results reveal almost 100% recovery of the secondary structure lost during SDS induced unfolding. We have conclusively proved that there is a marginal structural gain of the native protein at low surfactant concentration and β-CD also induces a marginal structural loss to the native protein. The unfolding process induced by SDS seems to be spontaneous and the binding of SDS to BSA is rather strong, as revealed by thermodynamic parameters.

Topics: Animals; beta-Cyclodextrins; Cattle; Circular Dichroism; Protein Folding; Serum Albumin, Bovine; Sodium Dodecyl Sulfate; Spectrometry, Fluorescence; Thermodynamics

The absorption and fluorescence characteristics of 4-(p-N,N-dimethyl-aminophenylmethylene)-2-phenyl-5-oxazolone (DPO) have been investigated in different solvents. DPO dye exhibits a large red shift in both absorption and emission spectra as solvent polarity increases, indicating a large change in the dipole moment of dye molecules upon excitation due to an intramolecular charge transfer interaction. The fluorescence quantum yield depends strongly on the properties of the solvents. Crystalline solids of DPO gave strong red emission at 605nm due to the excitation of molecular aggregates. The absorption and fluorescence emission spectral properties of DPO have also been investigated in organized media of aqueous micellar and β-cyclodextrin (β-CD) solutions. The critical micelle concentrations (CMCs) of SDS and CTAB as well as the binding constants of DPO in micellar solution and β-cyclodextrin have been also determined.

Topics: Absorption; beta-Cyclodextrins; Cetrimonium; Cetrimonium Compounds; Coloring Agents; Dimethylformamide; Dioxanes; Electrons; Hexanes; Kinetics; Methanol; Micelles; Oxazolone; Quantum Theory; Sodium Dodecyl Sulfate; Solubility; Solutions; Solvents; Spectrometry, Fluorescence; Time Factors

The interactions of bovine serum albumin (BSA) with ionic surfactants (sodium dodecyl sulfate, SDS, and cetyltrimethylammonium bromide, CTAB) and β-cyclodextrin (β-CD) have been investigated by electron paramagnetic resonance (EPR) and circular dichroism measurements. The spin probe selected to report on the interaction of albumin with surfactants and/or β-CD was 4-N,N-dimethyl hexadecyl ammonium-2,2,6,6-tetramethylpiperidine-1-oxyl iodide (CAT16), on account of (a) its balance between electrostatic and hydrophobic character and (b) the ability of BSA to form complexes with various organic molecules. The distribution of the spin probe among different environments in solutions containing only BSA was confirmed by the existence of two components in the EPR spectra: one revealing a restricted mobility of the spin probe, attributed to the protein-spin probe complex, and another one showing free movement, attributed to the spin probe in solution. The presence of surfactants and/or β-CD alters the distribution of CAT16 between various compartments in each system. Formation of protein aggregates as a result of thermal denaturation was evidenced by the appearance of an immobilized component in the EPR spectrum. This component is not present in the EPR spectra of CAT16 in protein/surfactant or protein/cyclodextrin solutions. Circular dichroism spectra of BSA provided information about changes in the secondary structure of the protein induced by the presence of surfactants and/or cyclodextrin in solution. The results demonstrate that β-CD hinders the interaction between the employed surfactants and the protein. The cationic surfactant (CTAB) induces changes in protein conformation at a lower concentration compared to the anionic surfactant (SDS).

Topics: Animals; beta-Cyclodextrins; Cattle; Cetrimonium; Cetrimonium Compounds; Circular Dichroism; Electron Spin Resonance Spectroscopy; Ions; Serum Albumin, Bovine; Sodium Dodecyl Sulfate; Solutions; Surface-Active Agents

An extensive dynamic and structural characterization of the supramolecular complexes that can be formed by mixing α-, β-, and γ-cyclodextrin (CD) with sodium dodecyl sulfate (SDS) in water at 283, 298, and 323 K was performed by means of computational molecular dynamics simulations. For each CD at the three temperatures, seven different initial conformations were used, generating a total of 63 trajectories. The observed stoichiometries, intermolecular distances, and relative orientation of the individual molecules in the complexes, as well as the most important interactions which contribute to their stability and the role of the solvent water molecules were studied in detail, revealing clear differences and similarities between the three CDs. Earlier reported findings in the inclusion complexes field are also discussed in the context of the present results. For any of the three native cyclodextrins, the CD(2)SDS(1) species in the head-to-head conformation appears to be a promising building block for nanotubular aggregates both in the bulk and at the solution/air interface, as earlier suggested for the case of α-CD. Moreover, the observed noninclusion arrangements involving β-CD are proposed as the seed for the premicellar (β-CD)-induced aggregation of SDS described in the literature.

Topics: alpha-Cyclodextrins; beta-Cyclodextrins; gamma-Cyclodextrins; Molecular Dynamics Simulation; Sodium; Sodium Dodecyl Sulfate; Temperature; Time Factors

On the line of a previous work on the spectral properties of some of heteroaryl chalcone, the absorption and fluorescence emission spectral properties of 3-(4'-dimethylaminophenyl)-1-(2-furanyl)prop-2-en-1-one (DMAFP), have been investigated in organized media of aqueous micellar and beta-cyclodextrin (beta-CD) solutions. While the absorption spectra are less sensitive to the nature of the added surfactant or beta-CD, the characteristics of the intramolecular charge transfer (ICT) fluorescence are highly sensitive to the properties of the medium. The ICT maximum is strongly blue-shifted with a great enhancement in the fluorescence quantum yield on adding micellar or beta-CD. This indicates the solubilization of DMAFP in the micellar core and formation of an inclusion complex with beta-CD. The critical micelle concentrations (CMC) as well as the polarity of the micellar core of SDS, CTAB and TX-100 have been determined. The CMC values are in good agreement with the reported values while the polarity is lower indicating that DMAFP molecules are incorporated in the micellar core not at the micellar interface. The inclusion constants of binding of DMAFP in micellar or beta-CD have been also determined. The thermodynamic parameters of formation of DMAFP:CD inclusion complex have been calculated from the temperature dependence of the fluorescence spectra of the formed complex. The highly negative value of formation entropy (DeltaS=-98.0Jmol(-1)K(-1)) reflects the high restrictions imposed on the movement of both the host and included guest molecules which is consistent with the increase of the fluorescence yield and blue shift of the fluorescence maximum.

Topics: beta-Cyclodextrins; Carcinogens; Chalcone; Dioxanes; Fluorescence; Furans; Micelles; Sodium Dodecyl Sulfate; Solutions; Spectrophotometry, Ultraviolet; Surface-Active Agents; Viscosity; Water

Chiral separations of three hydroxyflavanone aglycones, including 2'-, 3'-, and 4'-hydroxyflavanone, in capillary zone electrophoresis (CZE) using randomly sulfate-substituted beta-cyclodextrin (S-beta-CD) or dual cyclodextrin (CD) systems consisting of S-beta-CD and a neutral CD at low pH were investigated. The results indicate that S-beta-CD is an excellent chiral selector for enantioseparation of 2'-hydroxyflavanone and is a good chiral selector for 3'-hydroxyflavanone. Depending on the concentration of S-beta-CD ranging from 2.0 to 0.75% (w/v), the enantioresolution values were 10.5-19.5 and 1.8-3.4 for 2'- and 3'-hydroxyflavanone, respectively. The enantiomers of 4'-hydroxyflavanone could be effectively separated with S-beta-CD at a concentration of 2.0% (w/v) within 20 min. The enantioselectivity and enantioresolution follow the order 2'-hydroxyflavanone>>3'-hydroxyflavanone>4'-hydroxyflavanone. Alternatively, with the addition of sodium dodecyl sulfate (SDS) monomers at low concentrations in the electrophoretic system, enantioselectivity of these hydroxyflavanone aglycones could be enhanced with dual CD systems. In this case, SDS monomer acted as a complexing agent probably first with S-beta-CD and then subsequently with the analytes for increasing the effective electrophoretic mobility of the analytes towards the anode and as a selectivity controller for affecting the selectivity of hydroxyflavanones. Better enantioseparation between 2'-hydroxyflavanone and 3'-hydroxyflavanone could be achieved with a dual CD system consisting of S-beta-CD and gamma-CD than that with S-beta-CD and beta-CD. In addition, possible chiral recognition mechanisms of hydroxyflavanones are discussed.

Topics: beta-Cyclodextrins; Buffers; Electrophoresis, Capillary; Flavanones; Hydrogen-Ion Concentration; Molecular Structure; Sodium Dodecyl Sulfate; Stereoisomerism; Sulfates

A micellar electrokinetic capillary chromatography (MECC) method has been developed for the determination of the four isoflavones, i.e. biochanin A, formononetin, genstein and daidzein in red clover (Trifolium Pratense L.). The effect of running buffer pH and concentration were investigated. An electrolyte composed of 30 mm borate, 20 mm sodium dodecyl sulfate (SDS) and 4 mg/mL HP-beta-CD containing 5% (v/v) ethanol at pH 10.1 provides a satisfactory separation for all the analytes. The applied voltage was 25 kV, and the capillary temperature was kept constant at 25 degrees C with a UV detection at 254 nm. The relative standard deviations (RSD) of the migration time and peak area were less than 1.73 and 3.94% (intra-day), and 2.29 and 4.38% (inter-day), respectively, under the optimized separation conditions. Regression equations revealed a good linear relationship between the peak area of each compound and its concentration. The contents of the four compounds in red clover were successfully determined with satisfactory repeatability and recovery.

Topics: beta-Cyclodextrins; Boric Acids; Chromatography, Micellar Electrokinetic Capillary; Hydrogen-Ion Concentration; Isoflavones; Medicago; Reproducibility of Results; Sensitivity and Specificity; Sodium Dodecyl Sulfate; Spectrophotometry, Ultraviolet

In this study, a rapid MEKC method using 40 mM sodium borate buffer containing 50 mM SDS as surfactant was developed for the analysis of aristolochic acid (AA) in Aristolochia plants. Baseline separation of AA-I and AA-II was achieved within 3 min with high separation efficiency, satisfactory sensitivity, repeatability, and recovery. Resolution between AA-I and AA-II is above 5 and great performance with higher than 200,000 theoretical plate numbers was obtained. The detection limits (based on 3 S/N) were both 1.0 microg/mL. Two kinds of AA in 35 herbal samples of Aristolochia plants were successfully determined. The competition mechanism between beta-CD and SDS was also investigated by changing the content ratio of beta-CD and SDS.

Topics: Antiviral Agents; Aristolochia; Aristolochic Acids; beta-Cyclodextrins; Chromatography, Micellar Electrokinetic Capillary; Sodium Dodecyl Sulfate

Based on the fact that tolnaftate degrade to beta-naphthol sodium (RONa) at 5.00 mol/L NaOH solution and RO(-) was protonated to ROH after being acidified and adjusted to the pH 4.50 by acetic acid-sodium acetate buffer solution, we studied and discussed the mechanism of the supramolecular multirecognition interaction among the anionic surfactants sodium lauryl sulfate (SLS), beta-cyclodextrin (beta-CD), and beta-naphthol (ROH) by means of fluorescence spectrum, surface tension of the solution, infrared spectrograms, and (1)HNMR spectroscopy. The apparent formation constant of the ternary inclusion complex was determined to be (5.48 +/- 0.13) x 10(3) L(2)/mol(2). The thermodynamic parameters (DeltaG degrees, DeltaH degrees, DeltaS degrees ) for the formation of the inclusion complexes were obtained from the van't Hoff equation. It was indicated that the multiple and synergistic protection effect of SLS and beta-CD on the excited singlet state ROH played very important roles in the enhancement of the fluorescence of ROH. Results showed that, at room temperature, the naphthalene ring of ROH and the hydrophobic hydrocarbon chain of SLS were included into the cavity of beta-CD to form a ROH/SLS/beta-CD ternary inclusion complex with stoichiometry of 1:1:1, which provided effective protection for the excited state of ROH and increased the fluorescent intensity of ROH obviously.

Topics: Anions; beta-Cyclodextrins; Hydrolysis; Macromolecular Substances; Molecular Structure; Naphthols; Sensitivity and Specificity; Sodium Dodecyl Sulfate; Spectrometry, Fluorescence; Surface-Active Agents; Tolnaftate

The interaction of hen egg-white lysozyme with sodium n-dodecyl sulfate (SDS) as an anionic surfactant was investigated by UV-vis spectrophotometry at different pHs at 25 degrees C using HCl/glycine and NaOH/glycine for acidic and basic pH ranges, respectively. Analysis of the spectral data using chemometric method gave the evidence for the existence of intermediate components during the cited interaction. Results also indicated a connection between turbidity of the protein solution upon interaction with SDS and distribution of our newly found intermediates. As intermediates are important in aggregation of proteins, beta-cyclodextrin was employed as an anti-aggregation agent and the results obtained for the lysozyme-SDS-beta-cyclodextrin ternary system were compared with those obtained in the absence of beta-cyclodextrin on distribution and mole fraction of intermediates with. It is also shown that as the distribution of intermediates broadens in a range of SDS concentrations, the turbidity and aggregation state of solution are reduced.

Topics: Animals; beta-Cyclodextrins; Circular Dichroism; Hydrogen-Ion Concentration; Muramidase; Sensitivity and Specificity; Sodium Dodecyl Sulfate; Spectrophotometry, Ultraviolet

A cyclodextrin-modified micellar electrokinetic chromatographic (CD-MEKC) method for the determination of the most important potential impurities of methotrexate (MTX): 2,4-diamino-6-(hydroxymethyl)pteridine, aminopterine hydrate, 4-[N-(2-amino-4-hydroxy-6-pteridinylmethyl)-N-methylamino] benzoic acid, 4-[N-(2,4-diamino-6-pteridinylmethyl)-N-methylamino] benzoic acid, and the distomer D-MTX is presented. The MEKC separation of these compounds was optimized by applying a step-by-step approach. The addition of beta-CD to a conventional MEKC system, based on sodium dodecyl sulfate (SDS) as surfactant, showed to be essential for the enantioresolution of racemic MTX as well as for the separation of the achiral impurities. To achieve high-resolution factor between the peaks adjacent to the main component (L-MTX), as required in the analysis of related impurities, the separation conditions were stressed; in particular, the addition of methanol to the CD-MEKC system resulted in a very effective choice. Under the optimized final conditions (100 mM SDS and 45 mM beta-CD in a mixture of 50 mM borate buffer, pH 9.30-methanol (75:25 v/v)), the method was validated showing a general adequate accuracy (93-106% recovery) in the determination of L-MTX related substances at the impurity level of 0.12% w/w with a relative standard deviation (RSD)% lower than 8% (n = 4). The method was successfully applied to the analysis of pharmaceuticals (tablets and injections) which showed to contain the distomer D-MTX as major impurity and aminopterine hydrate as a further related substance in the commercial tablets.

Topics: beta-Cyclodextrins; Chromatography, Micellar Electrokinetic Capillary; Drug Contamination; Electrolytes; Methotrexate; Molecular Structure; Reproducibility of Results; Sensitivity and Specificity; Sodium Dodecyl Sulfate; Solvents; Stereoisomerism; Surface-Active Agents

An approach to the chiral separation of racemic mixtures of amino acids by means of micellar electrokinetic chromatography after derivatization with a new triazine spectroscopic reagent, 3-(4,6-dichloro-1,3,5-triazinylamino)-7-dimethylamino-2-methylphenazine (DTDP), has been evaluated. It was found that the derivatives of the aliphatic amino acids such as serine, valine and arginine, could produce a strong UV absorption at 282 nm, whose apparent molar absorptivities are of 10(-4) M(-1) cm(-1), and thus the concentration of the amino acids down to 3 x 10(-7) M can still give a detectable signal (S/N = 3). Beta-Cyclodextrin (beta-CD) added to the buffer system was used as a chiral selector, and separation conditions were optimized. The presence of an organic modifier (2-propanol) was also a prerequisite for the chiral separation. The best results for the chiral separation of DTDP-amino acids were achieved in a mixed sodium dodecylsulfate-beta-CD-borate-2-propanol medium at pH 9.0. Compared to some of the commonly used derivatization methods, the present one offers a relatively stable derivative and strong UV absorption for the spectroscopically inert amino acids, thus enabling amino acids to be separated and detected by CE even with a simpler UV detector.

Topics: Amino Acids; beta-Cyclodextrins; Chromatography, Micellar Electrokinetic Capillary; Cyclodextrins; Hydrogen-Ion Concentration; Indicators and Reagents; Sensitivity and Specificity; Sodium Dodecyl Sulfate; Spectrophotometry, Ultraviolet; Triazines

The influence of beta-cyclodextrin (beta-CD) on the critical micelle concentration (CMC) of sodium dodecyl sulfate (SDS) was investigated by capillary electrophoresis using anionic chlorophenols as probe molecules at pH 7.0. The variations of the electrophoretic mobility of probe molecules as a function of surfactant concentration in both premicellar and micellar regions in the absence and presence of beta-CD was analyzed. The results indicate that, as a consequence of a strong inclusion complexation between beta-CD and SDS, the encapsulation of beta-CD with probe molecules is greatly diminished, or even vanished, in the presence of SDS. The complexes formed between beta-CD and SDS monomers exist predominantly in the form of a 1:1 stoichiometry, while the complexes with a 2:1 stoichiometry reported previously in the literature as a minor component may exist by less than 10%. The elevation of the CMC value of SDS depends not only on the concentration of beta-CD in the buffer electrolyte but also on methanol content in the sample solution. The binding constants of probe molecules to beta-CD, to surfactant molecules, and to the complexes formed between beta-CD and SDS are reported.

Topics: beta-Cyclodextrins; Cyclodextrins; Electrophoresis, Capillary; Evaluation Studies as Topic; Methanol; Micelles; Sodium Dodecyl Sulfate

Electrokinetic chromatography (EKC) using micelles of bile salts alone or mixed with sodium dodecyl sulfate (SDS) and neutral, anionic, or cationic cyclodextrins (CDs) in the separation buffer has been employed in order to achieve fast enantiomeric separation of basic drugs. A study of the enantiomeric separation ability of these chiral selectors concerning four basic drugs (epinephrine, terbutaline, clenbuterol, and salbutamol) has been carried out under different experimental conditions. The best chiral selectors to perform the enantiomeric separation of these drugs were neutral beta-CD derivatives, specifically permethylated beta-CD PM-beta-CD. The effect of the PM-beta-CD concentration, temperature, and applied voltage on the enantiomeric resolution of the basic drugs was investigated. The use of a 25 mM ammonium acetate buffer (pH 5.0), 30 mM in PM-beta-CD together with an applied voltage of 20 kV and a temperature of 15 degrees C enabled the individual and fast enantiomeric separation of epinephrine, norepinephrine, terbutaline, clenbuterol, and salbutamol each one into its two enantiomers in less than 3 min. The EKC method was validated (precision and accuracy) to quantitate terbutaline in a pharmaceutical preparation, obtaining a limit of detection of 4 microg/mL.

Topics: Albuterol; beta-Cyclodextrins; Bile Acids and Salts; Buffers; Chromatography; Chromatography, Micellar Electrokinetic Capillary; Clenbuterol; Cyclodextrins; Epinephrine; Indicators and Reagents; Methylation; Pharmaceutical Preparations; Sensitivity and Specificity; Sodium Dodecyl Sulfate; Stereoisomerism; Terbutaline

Micellar electrokinetic chromatography (MEKC) was used for the chiral separation of uncharged analytes (C- and N-protected amino acids). Sodium dodecyl sulfate (SDS) was the micelle forming agent, and different cyclodextrin (CD) derivatives were added as chiral selectors. Suitable conditions for the enantioseparation were found by variation of the separation conditions. The influence of addition of organic solvents like acetonitrile or methanol, and other chiral additives (camphor-10-sulfonic acid, malic acid) was examined. The addition of an organic modifier resulted in different effects on micelle formation, and thereby on the separation. The used chiral additives did not improve the selectivity. Furthermore, dependence of the electroosmotic flow (EOF), and the capacity factors on the concentration of CDs was investigated. Increasing the CD concentration, both the EOF to a smaller extent as well as the capacity factors decrease. Nevertheless, the enantioseparation is improved with a CD-concentration up to 30 mM. Higher CD-concentrations reduce the separation of the analytes.

Topics: Acetonitriles; Amino Acids; beta-Cyclodextrins; Chromatography, Micellar Electrokinetic Capillary; Cyclodextrins; Esters; gamma-Cyclodextrins; Indicators and Reagents; Sensitivity and Specificity; Sodium Dodecyl Sulfate; Solvents; Stereoisomerism

The possible competitive displacement of a drug from its cyclodextrin-based inclusion complex by a third substance was investigated by studying the dissolution behaviour of tolbutamide-beta-cyclodextrin inclusion complex in demineralised water and in aqueous solution of different surfactants. Physical mixtures and kneaded systems were prepared in 1:1 and 1:2 drug-beta-cyclodextrin mol/mol ratios and they were characterised by hot-stage microscopy, differential scanning calorimetry, and X-ray powder diffractometry. The release behaviour of tolbutamide from its inclusion complex was studied by studying the dissolution of the binary systems in water and in aqueous solutions of three surfactants: polysorbate 20, poloxyl 23-lauryl ether, and sodium lauryl sulphate. When demineralised water was used as the dissolution media, the fastest dissolution of tolbutamide was obtained from 1:2 kneaded system followed by 1:1 kneaded system. The presence of poloxyl 23-lauryl ether and sodium lauryl sulphate in the media caused a decrement in the rate and extent of dissolution of the drug from both kneaded systems in comparison with that obtained from the same systems in water. However, the release of tolbutamide from the kneaded systems remains unaffected when polysorbate 20 was present in the dissolution media. Results of this study suggest that the simultaneous presence of beta-cyclodextrin and surfactants of proper molecular structure in a pharmaceutical formulation can give rise to an unexpected dissolution of the drug.

Topics: beta-Cyclodextrins; Calorimetry, Differential Scanning; Cyclodextrins; Dosage Forms; Polidocanol; Polyethylene Glycols; Polysorbates; Sodium Dodecyl Sulfate; Solubility; Solutions; Surface-Active Agents; Thermodynamics; Tolbutamide; Water; X-Ray Diffraction

Topics: Amino Acids; beta-Cyclodextrins; Buffers; Chromatography, Micellar Electrokinetic Capillary; Cyclodextrins; Hydrogen-Ion Concentration; Indicators and Reagents; Selenium Compounds; Sodium Dodecyl Sulfate; Stereoisomerism; Taurodeoxycholic Acid

Enantiomeric separation of 21 amino acids derivatized with fluoresceine isothiocyanate isomer I (FITC) has been studied by micellar electrokinetic chromatography using beta- and gamma-cyclodextrin (CD) as chiral selectors. Chiral resolution of 21 FITC derivatives of amino acids was achieved with both beta- and gamma-CD in 100 mM borate buffer (pH 9.5) containing 30 mM sodium dodecyl sulfate (SDS). The effects of CD concentration, SDS concentration and organic modifiers' concentration as well as capillary length were investigated. Chiral recognition capability of beta- and gamma-CD was compared. Gamma-CD was found to be a better chiral selector than beta-CD in terms of chiral resolution capability for FITC-amino acids.

Topics: 2-Propanol; Acetonitriles; Amino Acids; beta-Cyclodextrins; Chromatography; Cyclodextrins; Fluorescein-5-isothiocyanate; gamma-Cyclodextrins; Isomerism; Sodium Dodecyl Sulfate; Time Factors

We recently reported a new approach to protein refolding that utilizes a pair of low molecular weight folding assistants, a detergent and a cyclodextrin (Rozema, D., and Gellman, S. H. (1995) J. Am. Chem. Soc. 117, 2373-2374). Here, we provide a detailed study of carbonic anhydrase B (CAB) refolding assisted by these "artificial chaperones." When CAB is heated in the presence of a competent detergent, or when guanidinium-denatured CAB is diluted to nondenaturing guanidinium concentration in the presence of such a detergent, the detergent forms a complex with the non-native protein, thereby preventing aggregation. CAB is unable to refold from the detergent-complexed state, but folding can be induced by introduction of a cyclodextrin, which strips the detergent away from the protein. Use of artificial chaperones provides excellent yields of reactivated CAB under conditions that lead to little or no reactivation in the absence of the refolding assistants. Our studies show that the detergent can capture the unfolded protein even at submicellar concentrations, but that not all CAB-detergent complexes lead efficiently to refolded enzyme upon introduction of the stripping agent. Effective refolding appears to require that detergent stripping occur as rapidly as possible; intrinsically slow methods of detergent removal (dialysis or use of macroscopic adsorbents) are less effective than cyclodextrin at inducing renaturation upon detergent removal. The detailed characterization of artificial chaperone-assisted CAB refolding reported here should guide the application of this strategy to other proteins.

Topics: beta-Cyclodextrins; Carbonic Anhydrases; Cetrimonium; Cetrimonium Compounds; Chaperonins; Circular Dichroism; Cyclodextrins; Detergents; Guanidine; Guanidines; Hot Temperature; Kinetics; Protein Conformation; Protein Denaturation; Protein Folding; Sodium Dodecyl Sulfate; Thermodynamics