HF/6‐31G* energy surfaces for disaccharide analogs

The HF/6‐31G* level of theory was used to calculate relaxed potential energy surfaces for 12 analogs of disaccharides. The analogs were made by replacing glucose with tetrahydropyran and fructose with 2‐methyltetrahydrofuran. Molecules had zero, one or two anomeric carbon atoms, and di‐axial, axial‐equatorial, and di‐equatorial linkages. Despite the absence of hydroxyl groups, the surfaces account well for conformations that are observed in crystals of the parent disaccharides. Thus, torsional energy and the simple bulk of ring structures are major factors in determining disaccharide conformation. The contour shapes around the global minima depend on the number of anomeric carbons involved in the linkage, while the presence of alternative minima that have relative energies less than 4 kcal/mol mostly requires equatorial bonds. However, molecules with two adjacent anomeric centers gave exceptions to these rules. Flexibility values related to a partition function show that the di‐axial trehalose analog is the most rigid. The di‐equatorial pseudodisaccharide analog with no anomeric centers is most flexible. Reproduction of these surfaces is proposed as a simple test of force fields for modeling carbohydrates. Also, these surfaces can be used in a simple hybrid method for calculating disaccharide energy surfaces. © 2000 John Wiley & Sons, Inc. * J Comput Chem 22: 65–78, 2001     

High resolution 1H NMR structural studies of sucrose octaacetate in supercritical carbon dioxide

High pressure (HP), high resolution (HR), proton nuclear magnetic resonance (1H NMR) spectroscopy has been utilized for the first time to investigate the solution structure of a carbohydrate based system, sucrose octaacetate (SOA), in supercritical CO2. The studies indicate that the average solution state conformation of the alpha-D-Glucopyranosyl ring of SOA in scCO2 medium is consistent with the 4C1 chair form, while the beta-D-fructofuranosyl ring adopts an envelope conformation. The investigations also suggest that scCO2 is a promising medium to study the solution structure and conformation of acetylated sugar systems. Spectral manifestations of a specific interaction between the acetate methyl protons and CO2 molecules are also presented.     

高效液相色谱法测定木奈果中的山梨醇和糖类

用高效液相色谱外标法测定了木奈果中的可溶性糖和山梨醇 ,采用 μ Spherogelcarbohydrate柱和示差折光检测器 ,以水为流动相 ,柱温 85℃。相关系数在 0 970 9以上 ,加标回收率为 75 0 0 %～ 88 37%。测定结果表明 ,可溶性糖在果肉中的累积依果肉不同的生长发育阶段有特征性的变化。     

Effect of microsphere size on the drug release and experimental characterization of an electrospun naringin‐loaded microsphere/sucrose acetate isobutyrate (SAIB) depot

The aims of this study were to prepare different sizes of electrospun naringin‐loaded microspheres (Ng‐ms) and investigate the effects of the particle size of these microspheres on drug release from naringin‐loaded microsphere/sucrose acetate isobutyrate (Ng‐m‐SAIB) hybrid depots to develop an improved drug delivery system for tissue engineering. Different sizes of microspheres were produced using electrospray methods by controlling electrospinning parameters. The Ng‐m‐SAIB depots were prepared by dispersing Ng‐ms in SAIB depots. The morphology and size distributions of the electrospun Ng‐ms were characterized by polarizing microscopy and scanning electron microscopy (SEM). To better understand the release behavior of Ng‐m‐SAIB, the porosity of SAIB depots was measured. Consequently, both small (2.51 ± 0.191 μm) and large (5.03 ± 0.172 μm) microspheres exhibited smooth surfaces and good monodispersity. The initial and long‐term drug release rates of the large microspheres were lower than those of small microspheres. On the first day after 2.5‐μm and 5‐μm Ng‐m‐SAIB depots were produced, the burst release reduced dramatically from 68.79% to 3.30% and from 63.20% to 0.00%, respectively. After 92 days of release, the drug release rate of 5‐μm Ng‐m‐SAIB was still lower than that of 2.5‐μm Ng‐m‐SAIB, with values of 58.54% and 63.93%, respectively. These results demonstrate that drug release from Ng‐m‐SAIB depots can be tailored solely by varying the size of the microspheres and that good drug release behavior occurred.     

Sucrose‐Assisted Loading of LiFePO4 Nanoparticles on Graphene for High‐Performance Lithium‐Ion Battery Cathodes

A simple approach for loading LiFePO₄ (LFP) nanoparticles on graphene (G) that could assemble amorphous LiFePO₄ nanoparticles into a stable, crystalline, graphene‐modified layered materials (G‐S‐LFP, S=sucrose) by using graphene as building block and sucrose as a linker has yet to be developed. On the basis of differential scanning calorimetric and transmission electron microscopy analysis of the samples from controlled experiment, a possible mechanism was proposed to explain the “linker” process of LFP and graphene with sucrose as the linker. The electrochemical properties of the samples as cathode material for lithium‐ion batteries were studied by cyclic voltammogrametry and galvanostatic methods. Results showed that G‐S‐LFP displayed superior lithium‐storage capability with current density changes randomly form 0.5 to 10 C. The significant improvement for rate and cycle performance could be attributed to the high conductivity of the graphene host, the high crystallinity, and the layered structure.     

Fabrication and characterization of jute fabrics reinforced polypropylene-based composites: effects of ionizing radiation and disaccharide (sucrose)

Composites were prepared successfully by compression molding technique using jute fabrics (reinforcing agent) and polypropylene (matrix). Jute fabrics were treated with disaccharide (sucrose) solution and composites were fabricated with the treated fabric and polypropylene. The fiber content of the prepared composites was 40% by weight. It was found that the sucrose (2% solution) decreased the tensile strength (TS) and elongation at break about 6% and 37%, respectively, but tensile modulus and impact strength improved about 27% and 32%, respectively. When gamma radiation was applied through the untreated and treated composites the mechanical properties were improved much higher in non-treated Jute/PP-based composites than that of sucrose treated composites. For 5.0?kGy gamma dose the highest mechanical properties were observed for non-treated composites. At 5.0?kGy gamma dose the improvement of TS was 14% and 2% for non-treated and sucrose treated composites, respectively. The water uptake property of the sucrose treated composites was performed up to 10 days and composites absorbed 18% water. The functional groups of the both composites were analyzed by Fourier transform infrared spectroscopy machine. The scanning electron microscopic images of the both composites were taken for the surface and fiber adhesion analysis.     

蔗糖酯的相溶法合成研究

本法以蔗糖、棉籽油为原料。首先使用苛性钾与脂肪酸乙酯反应生成部分中性皂作为乳化剂，并加入一定量的蔗糖，使蔗糖和脂肪酸乙酯在较低温度下既可达到相溶状态，进而在均相下发生酯交换反应合成蔗糖酯。适宜的反应条件为：蔗糖：脂肪酸乙酯＝1：0．8；皂用量15％，催化剂用量2％；反应温度135℃；反应时间165min；压力≤666Pa。所得产品HLB值高于14。     

Thermodynamics of transfer of sodium chloride from water to aqueous sucrose at 25°C

Enthalpies of transfer of sodium chloride over the mixed-solvent range from pure water to mole fraction sucroseX ₃=0.05 (50 wt. %) were determined calorimetrically at 25°C. These were combined with free energies of transfer at constant molality (per 100 g of mixed solvent) calculated from isopiestic activity coefficients to yield negative entropies of transfer. The positive free energy is approximately a linear function ofX ₃, and the negative enthalpies show that the free energies and activity coefficients of NaCl increase with temperature. The enthalpy behavior of NaCl in aqueous hydrogen peroxide and the urea is very similar to that in the present study, indicating the possibility of rough colligative effect for such systems.     

Precise determination of low level sucrose amorphism by microcalorimetry

The DSC curve of freeze-dried amorphous sucrose shows the glass transition, the crystallization and the melting (just before decomposition) of the sample. Sucrose crystallization occurs below 100°C: this phenomenon can therefore be observed with the microcalorimeter Setaram Micro-DSC used in the scanning mode. Mixtures of amorphous and crystalline sucrose in known proportions were used to calibrate the instrument. Low level amorphism (down to about 0.5%) could be detected and quantitatively evaluated on the basis of the crystallization enthalpies determined. The calibration curve obtained can be applied to determine the degree of amorphism in milled sucrose. A simple gravimetric method, based on the desorption of water induced by recrystallization of the amorphous layer can be used to obtain similar data more rapidly. This simple method is particularly useful for controlling the amorphism on line during a process, and is also briefly described.     

A Modulated Differential Scanning Calorimetric study

Modulated Differential Scanning Calorimetry^? has been applied to frozen sucrose solutions in the concentration range 10–80% w/w. The results from this study present, for the first time, information on the reversing and non-reversing nature of events that occur in these solutions. The study demonstrates the potential benefits of this new technique to help separate complex transitions that can occur in the total heat-flow curves obtained using traditional differential scanning calorimetry. The results illustrate how this new technique can separate the different enthalpic events, which relate to the glass transition and the onset of ice dissolution that occurs during the heating of these frozen systems, by nature of their “reversing” and “non-reversing” contributions to the total heat flow.