Comparison and correlation of in vitro, in vivo and in silico evaluations of alpha, beta and gamma cyclodextrin complexes of curcumin

In the present study investigated the effect of curcumin (CUR) alpha (α), beta (β) and gamma (γ) cyclodextrin (CD) complexes on its solubility and bioavailability. CUR the active principle of turmeric is a natural antioxidant agent with potent anti-inflammatory activity along with chemotherapeutic and chemopreventive properties. Poor solubility and poor oral bioavailability are the main reasons which preclude CUR use in therapy. Extent of complexation was β-CD complex (82 %) > γ-CD (71 %) > α-CD (65 %). Pulverization method resulted in significant enhancement of CUR (0.002 mg/ml) solubility with CUR α-CD complex (0.364 mg/ml) > CUR β-CD complex (0.186 mg/ml) > CUR γ-CD complex (0.068 mg/ml). Gibbs-free energy and in silico molecular docking studies favour formation of α-CD complex > β-CD complex > γ-CD complex. With reference to CUR, relative bioavailability of CUR α-CD, CUR β-CD and CUR γ-CD complexes were 460, 365 and 99 % respectively. CUR–CD complexes exhibited increased bioavailability with an increase in t_½, tmax, Cmax, AUC, Ka, and MRT; and a decrease in Ke, clearance and Vd values. AUC increase was CUR α-CD complex > CUR β-CD complex > CUR γ-CD complex. Significant difference (p < 0.05) was observed between CUR α-CD complex and CUR γ-CD complex by one-way ANOVA and Dunnett’s post hoc test for multiple comparison analysis. Correlation observed between in vitro, in vivo and in silico methods indicates potential of in silico and in vitro methods in CD selection.     

Facile Synthesis of Selectively Monoprotected Unsymmetrical 1,3-Diketones from 2,2-Dimethoxyethyl Esters

Selectively monoprotected unsymmetrical 1,3-diketones were obtained by the reaction of 2,2-dimethoxyethyl esters with enamines in the presence of dichlorobis(trifiuoro-methanesulfonato)titanium.     

A Single‐Crystalline Mesoporous Quartz Superlattice

There has been significant interest in the crystallization of nanostructured silica into α‐quartz because of its physicochemical properties. We demonstrate a single‐crystalline mesoporous quartz superlattice, a silica polymorph with unprecedentedly ordered hierarchical structures on both the several tens of nanometers scale and the atomic one. The mesoporous quartz superlattice consists of periodically arranged α‐quartz nanospheres whose crystalline axes are mostly oriented in an assembly. The superlattice is prepared by thermal crystallization of amorphous silica nanospheres constituting a colloidal crystal. We found that the deposition of a strong flux of Li⁺ only on the surface of silica nanospheres is effective for crystallization.     

Efficient Synthesis of the Disialylated Tetrasaccharide Motif in N‐Glycans through an Amide‐Protection Strategy

A disialylated tetrasaccharide, Neu5Ac(α2,3)Gal(β1,3)[Neu5Ac(α2,6)]GlcNAc ( 1 ), which is found at the termini of some N‐glycans, has been synthesized. Compound 1 was obtained through an α‐sialylation reaction between a sialic acid donor and a trisaccharide that was synthesized from the glycosylation of a sialylated disaccharide with a glucosaminyl donor. This synthetic route enabled the synthesis of the as‐described disialylated structure. A more‐convergent route based on the glycosylation of two sialylated disaccharides was also established to scale up the synthesis. Protection of the amide groups in the sialic acid residues significantly increased the yield of the glycosylation reaction between the two sialylated disaccharides, thus suggesting that the presence of hydrogen bonds on the sialic acid residues diminished their reactivity.     

Evolution of the electronic structure of Be clusters

Using a modified symbiotic genetic algorithm approach and many-body interatomic potential derived from first principles, we have calculated equilibrium geometries and binding energies of the ground-state and low-lying isomers of Be clusters containing up to 41 atoms. Molecular-dynamics study was also carried out to study the frequency of occurrence of the various geometrical isomers as these clusters are annealed during the simulation process. For a selected group of these clusters, higher-energy isomers were more often found than their ground-state structures due to large catchment areas. The accuracy of the above ground-state geometries and their corresponding binding energies were verified by carrying out separate ab initio calculations based on molecular-orbital approach and density-functional theory with generalized gradient approximation for exchange and correlation. The atomic orbitals were represented by a Gaussian 6-311G** basis, and the geometry optimization was carried out using the GAUSSIAN 98 code without any symmetry constraint. While the ground-state geometries and their corresponding binding energies obtained from ab initio calculations do not differ much from those obtained using the molecular-dynamics approach, the relative stability of the clusters and the energy gap between the highest occupied and the lowest unoccupied molecular orbitals show significant differences. The energy gaps, calculated using the density-functional theory, show distinct shell closure effects, namely, sharp drops in their values for Be clusters containing 2, 8, 20, 34, and 40 electrons. While these features may suggest that small Be clusters behave free-electron-like and, hence, are metallic, the evolution of the structure, binding energies, coordination numbers, and nearest-neighbor distances do not show any sign of convergence towards the bulk value. We also conclude that molecular-dynamics simulation based on many-body interatomic potentials may not always give the correct picture of the evolution of the structure and energetics of clusters although they may serve as a useful tool for obtaining starting geometries by efficiently searching a large part of the phase space.     

On the titanium oxide neutral cluster distribution in the gas phase: Detection through 118 nm single-photon and 193 nm multiphoton ionization

Titanium oxide clusters are generated in a supersonic expansion by laser ablation of the metal and reaction with oxygen (0.1-6%) in He expansion gas. Mass spectra of the titanium oxide clusters are observed by photoionization with lasers of three different wavelengths: 118, 193, and 355 nm. Only the 118 nm (10.5 eV) light can ionize Ti(m)O(n) neutral clusters without fragmentation. Both the 193 nm (6.4 eV) and 355 nm (3.5 eV) multiphoton ionization cause fragmentation of the neutral clusters during the ionization process and, thus, can complicate the determination of the stable neutral Ti(m)O(n) gas-phase species. Employing 118 nm single-photon ionization and line-width data, the Ti(m)O(2m) and Ti(m)O(2m+1) series are found to be the most stable neutral cluster species for high oxygen content in the expansion gas. Fragmentation during the multiphoton ionization process for 193 nm light yields the cluster ions Ti(m)O(2m-1,-2)+. These ions are formed by the loss of one or two oxygen atoms from Ti(m)O(2m,2m+1) neutral species. The dominant cluster growth process is suggested to be through the addition of TiO2 species. For low oxygen content (<2%) in the expansion gas, oxygen-deficient clusters of the form Ti(m)O(2m-1,-2) are also observed. These latter series are not fragmented by the 193 nm ionization process.     

Opening mechanism of internal nanoporosity of single-wall carbon nanohorn

Single-wall carbon nanohorn (SWNH), which is a tubular particle with a cone cap, was oxidized in an oxygen flow at various temperatures. N(2) adsorption at 77 K, thermogravimetry (TG), differential thermal analysis (DTA), transmission electron microscopy, and Raman spectroscopy measurements were carried out on the oxidized SWNHs. The specific surface area of the oxidized SWNHs can be controlled by oxidation temperature, giving the maximum value of 1420 m(2)/g. The pore size distribution by the BJH method and the comparison plot of the N(2) adsorption isotherms of SWNH oxidized at different temperatures against that of as-grown SWNH revealed the minimum oxidation temperature for opening internal nanopores. TG-DTA analyses determined the components of as-grown SWNH: amorphous carbon 2.5 wt %, defective carbon at the cone part 15 wt %, tubular carbon 70 wt %, and graphitic carbon 12 wt %. These systematic analyses provided the exact internal nanopore volume of 0.49 mL/g for pure SWNH particles.     

Comparative study on pore structures of mesoporous ZSM-5 from resorcinol-formaldehyde aerogel and carbon aerogel templating

Resorcinol-formaldehyde aerogels and carbon aerogels of different mesoporosities have been used as templates for preparing bimodal zeolites of mesopores. Samples were thoroughly characterized with X-ray diffraction, field emission scanning electron microscopy, thermogravimetric analysis, X-ray photoelectron spectroscopy, N(2) adsorption at 77 K, as well as FT-IR spectroscopy and (29)Si nuclear magnetic resonance spectroscopy. The mesoporous ZSM-5 zeolites have additional mesopores of 9-25 nm in widths and 0.07-0.2 cm(3)/g in volumes, besides their perfect inherent micropores. Experimental results show the mesoporous systems of the finally obtained zeolites can be influenced by proper preparation of resorcinol-formaldehyde aerogels and carbon aerogels through solution chemistry. Consequently, zeolites of tunable mesoporosities can be prepared with this unique methodology.     

Clustering of Ti on a C60 surface and its effect on hydrogen storage

Recent efforts in finding materials suitable for storing hydrogen with large gravimetric density have focused attention on carbon-based nanostructures. Unfortunately, pure carbon nanotubes and fullerenes are unsuitable as hydrogen storage materials because of the weak bonding of the hydrogen molecules to the carbon frame. It has been shown very recently that coating of carbon nanostructures with isolated transition metal atoms such as Sc and Ti can increase the binding energy of hydrogen and lead to high storage capacity (up to 8 wt % hydrogen, which is 1.6 times the U.S. Department of Energy target set for 2005). This prediction has led to a great deal of excitement in the fuel cell community [see The Fuel Cell Review, http://fcr.iop.org/articles/features/2/7/4]. However, this prediction depends on the assumption that the metal atoms coated on the fullerene surface will remain isolated. Using first-principles calculations based on density functional theory, we show that Ti atoms would prefer to cluster on the C60 surface, which can significantly alter the nature of hydrogen bonding, thus affecting not only the amount of stored hydrogen but also their thermodynamics and kinetics.     

Effect of the graft density of cellulose diacetate-modified layered perovskite nanosheets on mechanical properties of the transparent organic–inorganic hybrids bearing covalent bonds at the interface

Transparent organic–inorganic hybrids with a whitish colour were prepared from cellulose diacetate (CDA) nanosheets derived from Dion–Jacobson-type ion-exchangeable layered perovskite HLaNb₂O₇·xH₂O (HLaNb) to prepare CDA-based hybrids bearing covalent bonds between HLaNb nanosheets and CDA matrices for improved mechanical properties. An n-decoxy derivative of HLaNb (C10_HLaNb) was exfoliated in acetonitrile by ultrasonication. TEM and AFM images revealed that C10_HLaNb was exfoliated into individual nanosheets. In order to explore the local environment around HLaNb nanosheets, a very small amount of CDA was reacted with a C10_HLaNb nanosheet dispersion [molar ratio COH:(NbOH + NbOC₁₀H₂₁) = 4:1] at 80 °C, and solid-state ¹³C NMR with cross polarization and magic angle spinning techniques showed that an alcohol-exchange-type reaction was proceeded to graft the CDA chains to the HLaNb nanosheets via new Nb–O–C covalent linkages. The CDA-based hybrids were prepared by dispersing 5 mass% of HLaNb nanosheets in CDA and subsequent heating at 80 °C for 1–7 days to cause a grafting reaction, and the product prepared by a 1-day grafting reaction exhibited improved mechanical properties compared to neat CDA; the Young’s modulus, tensile strength and toughness increased by 18, 34 and 78%, respectively. The mechanical properties deteriorated with further extension of the reaction period, however. In addition, a hybrid film prepared by mixing CDA and a C10_HLaNb nanosheet dispersion exhibited only a slight improvement in mechanical properties. These results clearly indicate that formation of an appropriate number of Nb–O–C bonds at the nanosheet/CDA interfaces is effective for improving mechanical properties.