Molecular mechanics calculations on carbonyl compounds. III. Cycloketones

Molecular mechanics (MM4) calculations were carried out on cycloketones for ring sizes ranging from 4 to 11 carbon atoms. The MM4 relative energies for the various conformations of the cycloketones were compared to density functional theory (DFT) calculations (B3LYP/6‐31G*), which were also carried out in this work. For small ring sizes (n=4–6), calculated molecular geometries, dipole moments, moments of inertia, and vibrational spectra were compared to experimental data. The axial–equatorial energy differences in methyl‐substituted cyclohexanones were also calculated by MM4 and compared to ab initio, DFT, and experimental results. The results of the MM4 studies on cycloketones showed significant improvement from those of MM3 calculations performed in parallel with the MM4 calculations. © 2001 John Wiley & Sons, Inc. J Comput Chem 22: 1451–1475, 2001     

Molecular mechanics calculations on carbonyl compounds. IV. Heats of formation

Molecular mechanics (MM4) calculations on the heats of formation of aldehydes and ketones were carried out for a total of 59 compounds (10 aldehydes and 49 ketones). Optimization of the heat of formation parameters was obtained by a least squares fit to the experimentally known heats of formation. With the optimized MM4 heat of formation parameters, the MM4 calculated heats of formation showed significant improvement over those of MM3. The standard and weighted root mean square deviations for the MM4 values were 0.35 and 0.31 kcal mol^?1, respectively, whereas for the MM3 values they were 0.42 and 0.39 kcal mol^?1, respectively. © 2001 John Wiley & Sons, Inc. J Comput Chem 22: 1476–1483, 2001     

Studies on chemistry and immuno‐ modulating mechanism of a glycoconjugate from Lycium barbarum L.

The detailed structure of an O‐glycan derived from the fruit of Lycium barbarum L. was elucidated based on glycosidic linkage analysis, complete and partial acid hydrolysis, ¹H‐NMR and ¹³C NMR spectroscopy. According to the experiments, the carbohydrate was in the form of polysacchride (arabinogalactan) chains with highly branched 3, 4‐galactans and terminal arabinofuranosyl substituents. The immuno‐modulating mechanism of glycoconjugate and its glycan were investigated using tritium thymidine incorporation assay, flow cytometry assay and electrophoretical mobility shift assay (EMSA). The results suggested that the immunoactive components of the fruit of Lycium barbarum L. could enhance the splenocyte proliferation in normal mice and the effects of glycan chain were stronger than those of glycoconjugate. The target cell was most likely to be B‐lymphocyte, on which existed receptor binding site acting with the glycan. In addition, the immuno‐stimulatory effect of glycoconjugate (LbGp4) and its glycan (LbGp4‐OL) was associated with activating the expression of nuclear factor KB (NF‐KB) and activator protein 1 (AP‐1).     

A phase separation fluoroimmunoassay of estradiol

A competitive indirect fluoroimmunoassay of free estradiol (E₂) was established based on the thermal sensitivity of hydrogel–‐poly‐N‐isopropylacrylamide. Free estradiol was covalently bound to bovine serum albumin (BSA) to form complete antigen (E₂‐BSA), which was in turn labeled by fluorescein isothiocyanate (FTTC) as the fluorescence probe. The anti‐ E₂ monoclonal antibody (McAb) was prepared by an in vivo method, and coupled with N‐isopropylacrylamide (NIPA) to make an immune copolymer, poly‐N‐isopropylacylamidemonoclonal antibody (pNIPA‐McAb), for the determination of free E₂. The immunoassay method was based on the competitive binding of free E₂ and fluoresceinated antigen (E₂‐BSA‐FTTC) with limited amount of pNIPA‐McAb. When the immunological reaction was over, precipitation and centrifugal procedures were carried out to separate pNIPA‐McAb‐E₂‐BSA‐FTTC from other constituents in solution. The precipitate pNIPA‐McAb‐E₂‐BSA‐FTTC was dissolved in solution and then the fluorescence intensity was measured. The calibration curve covered a range of 78–500 ng/mL for free E₂. The recoveries were 91.2–107.2%.     

Reaction of HCFC‐133a (CF3CH2C1) or HFC‐134a (CF3CH2F) with alcohols or phenols in DMSO in the presence of KOH

In an open glassware, heating a gas HCFC‐133a (CF₃CH₂C1) or HFC‐134a (CF₃CH₂F), KOH and a phenol (or an alcohol) in DMSO at 80°C gave ethers ROCF₂CH₂X and (E/Z)‐ROCF = CHX (X = Cl, F) in moderate yields.     

Synthesis of 4‐halo‐2 (5H)‐furanones and their suzuki‐coupling reactions with organoboronic acids. A general route to 4‐aryl‐2 (5 H) ‐furanones

4‐Halo‐2(5H)‐furanones were prepared by the halolactonization of 2,3‐allenoic acids. The subsequent Suzuki coupling reaction of 4‐halo 2(5H)‐furanones with aryl boronic acids was carried out to produce 4‐aryl‐2(5H)‐furanones in excellent yields.     

Density Functional Study on the Reactivity of Carbenes Toward 1,2‐H Shifts

The 1,2‐H shift reactions of simple carbenes (CH₂Y‐C‐X) have been studied using density functional theory (DFT). The influence of the substituent X and Y groups on the activation energy (Ea) of 1,2‐H shifts were examined. The ‘by stander’ Y substituents lower E_a in the order of Me, F > Cl, Br > H. Our analysis shows that the X effect is more significant than the by stander Y effect. X substitutions increase E_a of carbenes in the order of F > Cl > Br > Me > H. The influence of X on E_a is governed by the singlet‐triplet energy separation (ΔE_S‐T) of the carbene, i.e., E_a of a carbene is larger as its ΔE_S‐T in creases due to an X substitution. The X effect was also found to be related to the magnitude of the exothermicity: Ea of reaction is smaller when the reaction is more exothermic. Origin of the Y effect is attributed to the inter play between two factors: ‘lateness’ of transition state on the potential energy surface, and the exothermicity of the reaction.     

Synthesis and Spectroscopy of Novel‐α‐Pyrazolylglycine Derivatives

The synthesis of α‐pyrazolylglycine derivatives(7a‐d) with different substituents, starting from glycine have been pre pared. The spectroscopy of intermediate compounds and the final amino acids have been discussed.     

Polymer Coated Piezoelectric Quartz Crystal Protein Bio‐Sensors

A polymer coated piezoelectric crystal detection system with a home‐made computer interface for signal acquisition and data processing was prepared as a liquid chromatographic detector for various proteins. Various polymers, e.g., polyvinyl aldehhyde (polyacrolein) (PVA), polyacrylamide/glutaldehyde (PAA/GA) and bio‐gel A, were used as coating materials on quartz crystals for adsorption of various protein molecules, e.g., catalase (CA), hemoglobin (Hb), α‐chymotrypsin (Ch), albumin (Ab). The frequency responses of the polyacrlein coated piezoelectric detector for various proteins were in the order: catalase> hemoglobin> α‐chymotrypsin > albumin. In contrast, the order of the frequency responses of bio‐gel A and polyacrylamide/glutaldehyde coated piezoelectric crystals for these proteins were: hemoglobin> catalase > α‐chymotrypsin ≥ albumin and hemoglobin > albumin > catalase. The polyacrolein coated piezoelectric crystal protein detector exhibited a good linear frequency response with a high sensitivity of about 2.5×10³ Hz/(mg/mL) for catalase. In addition, bio‐gel A and polyacrylamide/glutaraldehyde coated crystals were sensitive to hemoglobin with sensitivities of about 4.5×10³ Hz/(mg/mL) and 3.0×10³ Hz/(mg/mL), respectively. Study of the interference of various organic molecules, e.g., alcohols, amines, ketones and carboxylic acids, in the detection of proteins with theses polymer coated crystals was also made. The polyacrolein coated crystal for proteins under went less interference from various organic molecules than bio‐gel A or polyacrylamide/glutaraldehyde coated crystals. Effects of coating load, concentration of proteins and flow rate of liquid chromatographic eluent were also investigated and discussed.     

Indirect Determination of Ascorbic Acid with Ammonium Sulfate and Ethanol by Extraction and Flotation of Copper

A new method of indirect determination of ascorbic acid with ammonium sulfate and ethanol by extraction and flotation of copper in the presence of thiocyanate has been studied in this paper. The study shows that a small amount of Cu(II) is reduced to Cu(I) by ascorbic acid, then Cu(I) precipitates with SCN^?. In the course of phase separation of ethanol from water, the precipitated CuSCN is extracted and stays in the interface of ethanol and water. A good linear relationship is observed between the extraction yield of Cu(II) and the amount of ascorbic acid. The detection limit for ascorbic acid is 1 10^?5 M. Every parameter has been optimized and the reaction mechanism has been studied. The method is simple, rapid (5 min) and suffers from few interferences of common anions and cations. It has been successfully applied for the determination of ascorbic acid in pharmaceuticals and fruits.