Formation Of Β-cyclodextrin Research Articles

Complex Formation of β-Cyclodextrin with Benzoic Acid and Rutin in Water–Ethanol Solvents: Thermal and Thermodynamic Characteristics

Complex Formation of β-Cyclodextrin with Benzoic Acid and Rutin in Water–Ethanol Solvents: Thermal and Thermodynamic Characteristics

Genomic sequencing of Gracilibacillus dipsosauri reveals key properties of a salt-tolerant α-amylase.

Gracilibacillus dipsosauri is a moderately-halophilic Gram-positive bacterium which forms an extracellular α-amylase that is induced by starch, repressed by D-glucose, and active in 2.0M KCl. Previous studies showed that while enzyme activity could be measured with the synthetic substrate 2-chloro-4-nitrophenyl-α-D-maltotrioside (CNPG3), other assays were inconsistent and the protein showed aberrant mobility during nondenaturing gel electrophoresis. To clarify the properties of this enzyme, the genome of G. dipsosauri was sequenced and was found to be 4.19Mb in size with an overall G+C content of 36.9%. A gene encoding an α-amylase composed of 691 amino acids was identified. The protein was a member of the glycosyl hydrolase 13 family, which had a molecular mass of 77,396 daltons and a pI of 4.39 due to an unusually large number of aspartate and glutamate residues (95/691 or 13.7%). BLAST analysis of the amino acid sequence revealed significant matches to other proteins with cyclodextrin glycosyltransferase activity. Partial purification of the protein from G. dipsosauri showed that fractions catalyzing the hydrolysis of CNPG3 and p-nitrophenyl-D-maltoheptoside also catalyzed the formation of β-cyclodextrin but not α-cyclodextrin or γ-cyclodextrin. Formation of β-cyclodextrin was not stimulated by high salt concentrations but did occur with rice, potato, wheat, and corn starches and amylopectin. These studies explain the unusual features of the α-amylase from G. dipsosauri and indicate it should be classified as EC 2.4.1.19. The availability of the complete genomic sequence of G. dipsosauri will provide the basis for studies on other enzymes from this halophile which may be useful for biotechnology.

Retention of Cyclodextrins under the Conditions of Reversed-Phase Chromatography and Determining the Stability Constants of Inclusion Complexes of Antocyanins with β-Cyclodextrein

The chromatographic behavior of α, β, and γ-cyclodextrins on three types of reversed-phase chromatography of stationary phases—С4, С8, and С18—is investigated. Patterns of sorption are determined experimentally, and modeling is used to determine the nature of interaction between cyclodextrins and grafted phases. Based on the obtained results and considering experiments on the formation of a complex of β-cyclodextrin and n-hexane, it is suggested that the probability of modifying surfaces of the C4 phase with cyclodextrins in aqueous–acetonitrile mobile phases with low contents (from 5 vol %) of organic modifier is low, and the C18 phase could be used without surface modification of the sorbent when the acetonitrile content is above 10 vol %. To corroborate these conclusions, the constants of complex formation of β-cyclodextrin with some anthocyanins are determined by adding β-cyclodextrin to the mobile phase under the conditions of chromatography on the C4 phase; the same is impossible using the C18 phase.

Экспериментальные исследования антиоксидантной активности комплекса β-циклодекстрин – гистохром

На основе сравнительных экспериментальных исследований гистохрома синтезирован комплекс β-циклодекстрин – гистохром в соотношении 2:1. В экспериментах на длительность сохранения антиоксидантного эффекта комплекс β-циклодекстрин – гистохром при сравнении с эквимолярной дозой гистохрома показал пролонгацию антиоксидантной активности с 6 до 16 дней по сравнению с гистохромом. На основании результатов 1H ядерной магнитной резонансной спектрометрии показано формирование комплекса β-циклодекстрин – гистохром. Проведено компьютерное моделирование комплекса β-циклодекстрин – гистохром, показавшее наименьшую энергию при формировании комплекса «голова-к-хвосту».

Effects of Substituent and Solvent on Inclusion Complexation of β-Cyclodextrins with Azobenzene Derivatives

The equilibrium constants (K) for the inclusion complex formationof β-cyclodextrin (β-CD) with Methyl Orange (MO) and substituted azoanilinium chlorides were determinedspectrophotometrically. Based on the results, the substituent effecton the inclusion complexation of β-CD with azoanilinium chlorides was discussed indetail. Further, the solvent effects on the inclusion complexation of MO with β-CD andheptakis(2,6-di-O-methyl)-β-cyclodextrin (DM-β-CD) wereexamined in aqueous organic mixtures with water-miscible organic compounds(dimethylsulfoxide, acetonitrile, N,N-dimethylformamide, and acetone). It was found that the K value for the inclusion complexformation with β-CD and DM-β-CD decreases remarkably with increasing ratioof organic solvents, dependent of the surface tension of solvent mixtures.

The role of intra- and intermolecular hydrogen bonds in the formation of β-cyclodextrin head-to-head and head-to-tail dimers. The results of ab initio and semiempirical quantum-chemical calculations

The conformation of a free β-cyclodextrin molecule optimized by the MNDO/PM3 quantum-chemical calculations has C7 symmetry. The “right” orientation of the interglucose hydrogen bonds in β-cyclodextrin, in which the 2-OH groups act as the proton donors and the O atoms of the nearby 3"-OH groups function as the proton acceptors, is advantageous for thermodynamic reasons. The ring of seven H bonds thus formed stabilizes the symmetrical form of β-cyclodextrin. The β-cyclodextrin head-to-head dimer has D7 symmetry and consists of molecules whose 2-OH groups partcipate as proton donors in the formation of fourteen complementary intermolecular hydrogen bonds. The energy of H bonds in the β-cyclodextrin monomer and dimer was estimated to be 1.0--1.4 kcal mol–1. Of the two possible β-cyclodextrin dimers, the “head-to-tail” dimer is more thermodynamically stable. The thermodynamic preference of the right orientation of the inter-glucose H bonds in β-cyclodextrin was confirmed by the MP2/6-31G(d,p)//6-31G(d,p) abinitio calculations for maltose (α-glucodioside). The maltose molecule with inter-glucose H bonds of the type 2-OH→O(3")-H is more stable than the structure with the H-(2)O←H-O(3") orientation of H bonds with a difference of ∼2.7 kcal mol–1. According to the MNDO/PM3 method, the maltose structure with the right H bond orientation is more stable by ∼3.1 kcal mol–1.

β-Cyclodextrin Inclusion Complexes of Aromatic Amines and Nitrocompounds and their Photoinduced Electron Transfer Reaction with the Tris(2,2'-bipyridine)ruthenium(II) Complex

The formation of β-cyclodextrin (β-CD) inclusioncomplexes of aromatic amines and nitrocompounds have been studied by absorptionand emission spectral methods. Among the different compounds studied, p-nitrobenzoic acid showed the smallest Kf value. 3,5-dinitrobenzoic acid showed the highest Kf value due to the formation of a hydrogenbond between the nitro group and the hydrogen in the hydroxyl groupof CD, and this is not possible with p-nitrobenzoic acid. The lower Kf values in the range 60–70 observed for ortho substituted compounds indicate the steric effect imposed by the ortho substitution of the compound. The para substituted compounds showed higher Kf values in the range 110–130 due to the hydrophobic effect and also due tothe absence of a steric effect. The lifetime of the Ru(II) complex is not affected by the presence of β-CD. When the aromatic amines and nitrocompounds are used as quenchers for the excited state [Ru(bpy)3]2+, the quenching rate constant (kq) values are not significantly affected by the presence of β-CD. This indicates that the electron donor or electronacceptor groups are not included into the cavity of β-CD.

Symmetry breaking during the formation of beta-cyclodextrin-imidazole inclusion compounds: capillary electrophoresis study.

A mathematical model was developed for the estimation of binding constants by capillary electrophoresis. The effective electrophoretic mobility in a solute mixture is dependent on the cyclodextrin concentration in the background electrolyte (BGE) as well as the stoichiometry and the binding constant of the guest-cyclodextrin complex. As well, a determination of the degree of complexation, nc (the percent of complexed guest) could be carried out. The model was applied to a series of imidazole derivatives. Thermodynamic data for the solute complexation mechanism were calculated. Different van't Hoff plot shapes of the degree of complexation were observed with different BGE pH values, indicating a change in the solute complexation mechanism. Enthalpy-entropy compensation revealed that the solute complexation mechanism was independent of the imidazole derivative molecular structure, the same at pH = 4.5, 5.0, 5.5, 6.0, and 6.5 but changed at pH = 7.0 and 7.5. Topological defects formed during a symmetry-breaking transition could be responsible for the modification of the structure of the cyclodextrin cavity and explained the nc variations in relation to pH and temperature.

Fluorescence Studies of the Effects of t-Butyl Functionalities on the Formation of Ternary β-Cyclodextrin Complexes with Pyrene

The effects of t-butyl (TB) compounds on the formation of β-cyclodextrin (CD)/pyrene complexes have been examined by monitoring changes in the fluorescence I/III band ratio of 1.0 × 10−7 M pyrene in 0.075 M of the t-butyl compounds and in various concentrations of β-CD in a solvent mixture consisting of 60% v/v methanol/40% water solution. For the compounds tested, the strongest effects were observed in the presence of the following (in decreasing order): TB-carbamate, TB-carbazate, TB-( N-hydroxy) carbamate, TB-( N-butoxy carbonyl) glycine, and TB-formate. In terms of enhancement of the pyrene/β-CD binding constant, all exhibited effects stronger than those previously reported for t-butyl alcohol. In contrast, TB-amine, TB-acetic acid, and TB-acetoacetate exhibited very little effect. There appears to be a relationship between the chemical structure of the modifier molecules and the magnitude of their concomitant effects on the I/III ratio. In fact, the t-butyl modifiers which exhibited moderate to strong effects have a common caboxy, –C–O–, skeleton attached to the t-butyl moiety in their general structure: (CH3)3C–O–R. The modifier effect was also found to be independent of the pH of the solutions. A detailed explanation has been offered for the observed changes in the I/III ratio relative to t-butyl functionalities.

Retention behavior of β-cyclodextrin complexes of anthracene and pyrene using reversed-phase liquid chromatography: The effects of tert.-butanol and cyclopentanol

The effects of tert.-butanol and cyclopentanol on the formation of β-cyclodextrin (β-CD)-anthracene and β-CD-pyrene complexes have been studied using reversed-phase liquid chromatography. The retention times of anthracene and pyrene were monitored when eluted in a C 18 column with mobile phase mixtures consisting of methanol, water, β-CD, and a small amount of tert.-butanol or cyclopentanol. Plots of capacity factor of anthracene versus concentration of β-CD in the mobile phase in methanol-water mixtures and in mixtures containing 1% (v/v) cyclopentanol or tert.-butanol as secondary modifiers showed very similar trends. This suggests that anthracene forms weak complexes with β-CD, and that the presence of these secondary mobile phase modifiers have little effect on the β-CD-anthracene inclusion reaction. In contrast, pyrene showed no discernable change in retention time with increases in β-CD concentration. However, in the presence of 1% (v/v) tert.-butanol or cyclopentanol, capacity factor of pyrene decreased drastically, more in 1% (v/v) cyclopentanol than in 1% (v/v) tert.-butanol. Formation of a ternary β-CD-pyrene-alcohol complex has been proposed to explain the effects.