Interaction of tri-O-methyl-β-cyclodextrin with drugs

Summary The effect of tri-O-methyl--cyclodextrin(methyl--CD) on the partition coefficients of drugs, such as p-nitrophenol, salicylic acid, benzoic acid, and aspirin, was studied at 25°C. The partition coefficients of these drugs were increased linearly with methyl--CD concentration. The increase of partition coefficients was interpreted by the 11 complex formation between methyl--CD and the drug in CHCl₃ phase.The interaction between p-nitrophenol and methyl--CD in solution was studied by UV and PMR spectroscopies. It was concluded that p-nitrophenol is included in the cavity of methyl--CD in both aqueous solution and CHCl₃ solution.Inclusion compounds of these drugs with methyl--CD in the solid state were studied by X-ray diffractometry, IR spectroscopy, and DSC measurements. 11 crystalline inclusion compounds were obtained from hot water. It is also suggested that amorphous inclusion compound was obtained by the grinding of drug with methyl--CD.The dissolution rate and the bioavailability of ketoprofen were significantly increased in the presence of methyl--CD. The bioavailability of ketoprofen after oral administration with methyl--CD to rats was 3.7 times that of ketoprofen alone.     

A software package for the evaluation of Zeeman AAS data using a Perkin-Elmer model 3600 data station

The Perkin-Elmer Zeeman/5000 Atomic Absorption Spectrometer is only able to perform a calibration with three single standards or a one-point standard addition. The accuracy and precision of these methods are inappropriate in ETA-AAS, a computer-based data management is essential.A software package for calibration and evaluation was developed using curve fitting by linear regression based on a leastsquares fit when absorbances were transformed by the Baule-Mitscherlich function. The total analytical range could be covered by this method whether peak area or peak height values were fitted. The maximum absorbance levels could be calculated, as well.Absorbance signals were collected and stored by the HGA-graphics software (modified by Perkin-Elmer Nederland B. V.). The Pecowriter software was used for identifying data and file manipulations. The results of the calibration and evaluation can be stored on disk and/or printed. Calibration curves can be plotted on hardcopy output. The Limit of Detection and the Characteristic Mass can be calculated.The use of the CALIBRATION program is demonstrated by the calibration curves for the determination of Pb, Cd, As, Se, Cr, Al, Cu and Ni using mostly STPF-conditions. The performance of the method evaluated by the root mean square percent deviation of the fit is equal to the traditional curve-fitting function as well as to rational or quadratic functions.The use of the EVALUATION program is demonstrated by the results of the direct determination of lead in mineral waters.     

电影胶片掉胶问题的研究

本文用凝胶层析法和紫外分光光度法对电影胶片掉胶问题进行了研究,得出初步结论: 1)证实了在电影胶片和加工药液中确实存在着可溶解的明胶(多肽)。 2)在室温下可从商品明胶分离得到“溶胶”和“凝胶”两个组份,“溶胶”由于复性能力较弱而易于降解。 3)提胶温度和深度是影响“溶胶”含量的重要工艺参数,先在45℃下萃取,再在50℃下提胶,可以得到“溶胶”含量很低的明胶产品,但随着提胶过程的继续进行,“溶胶”含量又将逐道增高。     

A quantum defect model for the s, p, d, and f Rydberg series of CaF

We present an improved quantum defect theory model for the "s," "p," "d," and "f" Rydberg series of CaF. The model, which is the result of an exhaustive fit of high-resolution spectroscopic data, parameterizes the electronic structure of the ten ("s"Σ, "p"Σ, "p"Π, "d"Σ, "d"Π, "d"Δ, "f"Σ, "f"Π, "f"Δ, and "f"Φ) Rydberg series of CaF in terms of a set of twenty μ(ll('))(Λ) quantum defect matrix elements and their dependence on both internuclear separation and on the binding energy of the outer electron. Over 1000 rovibronic Rydberg levels belonging to 131 observed electronic states of CaF with n? ≥ 5 are included in the fit. The correctness and physical validity of the fit model are assured both by our intuition-guided combinatorial fit strategy and by comparison with R-matrix calculations based on a one-electron effective potential. The power of this quantum defect model lies in its ability to account for the rovibronic energy level structure and nearly all dynamical processes, including structure and dynamics outside of the range of the current observations. Its completeness places CaF at a level of spectroscopic characterization similar to NO and H(2).     

反相高效液相色谱法测定3种中成药中的葛根素

 建立了测定小儿清感灵片、步长新脑心通胶囊和感冒清热颗粒 3种中成药中葛根素含量的反相高效液相色谱方法。采用APEXODS色谱柱 ,以醋酸铵缓冲液 (10 0mmol/L ,pH 5 0 ) 甲醇 (体积比为 75∶2 5 )的混合溶液为流动相 ,检测波长为 2 5 0nm ,流速为 0 8mL/min。葛根素在 2mg/L～ 2 0mg/L时其色谱峰面积与质量浓度的线性关系良好 (r =0 9999) ;上述 3种中成药中的葛根素含量分别为 3 48mg/g ,1 0 8mg/ g及 1 5 2mg/ g(蔗糖型 ) ;其加样回收率分别为 99 0 % ,93 4%和 97 5 %。该法简便、快速、专属性强 ,可以作为多种中药制剂中葛根素含量的测定方法。     

General properties of the hartree-fock problem demonstrated on the frontier orbital model

The general Hartree-Fock energy in the frontier orbital model in the terms of independent variables is given. The existence conditions for extrema of this expression are derived and their relation with various types of solutions of the HF problem as RHF, UHF and complex wavefunctions is shown. The connection between overall properties of the energy surface and the local properties i.e. the stability and instability conditions of various kinds is demonstrated. The conditions for the occurrence of strange HF solutions are expressed in terms of quantities characterizing the correlation effects. This shows explicitly that the lack of respecting the electronic correlation is the reason for the occurrence of the strange HF solutions for the molecular configurations which exhibit a certain amount of diradical character.The summary of the results has been presented at the 6th Jerusalem Symposium on Quantum Chemistry and Biochemistry and at the I. Congress of Quantum Chemistry, Menton, July 1973.On leave of absence from Institute Rudjer Bokovi, Zagreb, Yugoslavia.     

试论化学教学中的"自我对话"教育

“自我对话”教育强调学习者的主体作用和能动作用,它符合新课程理念和建构主义学习理论。实施“自我对话”教育必须注意激发学生的“自我对话”意识,并通过学前“知我性对话”、学中“生成性对话”和学后“反思性对话”等形式加以落实。     

Computer-aided library search of combined LC-Retention and diode-array-UV-spectral data

An automated library search system for computer-aided identification of organic compounds using combined UV-spectral and LC-retention data, as acquired by HPLC with linear diodearray-UV-detection, is presented.The keystone of the system is a set of similarity indices which have been developed on the basis of mathematical-statistical models of the reproducibility of the spectral and retention data. The similarity indices have the form of a significance probability, a quantity originating from the general theory of hypothesis testing. The output of the LC-UV retrieval system is a compound identity or a list of identities (if any) for which the relevant similarity index has a value above a preset threshold. The data base used in this investigation contained 186 sets of UV-spectral and LC-retention data of 74 organophosphorus pesticides measured from standard solutions under various experimental conditions. A test set consisted of 186 alternative data sets of the same compounds as contained in the data base, however measured under different experimental conditions. The performance of the LC-UV reproducibility-based retrieval (LUVRR) system was evaluated using recall/reliability plots. The results appeared to be quite promising: for 95% of the unknowns, the target reference (correct positive) was on top of the hit list with a similarity index value being significantly higher than values found for false positives.The software is written in Pascal. The present (experimental) version of the system runs on a Data General Eclipse MV/4000 minicomputer.     

Chitosan–Carrageenan Gels

Phase behavior of the systems during the formation of polyelectrolyte complexes obtained by mixing of aqueous solutions of chitosan and -, -, or -carrageenan was studied. The gelation was shown to occur throughout the whole bulk solution at chitosan and -carrageenan concentrations higher than 0.1 and 0.3 wt %, respectively. At lower polysaccharide concentrations, the polyelectrolyte complexes precipitated. The study was performed at the polysaccharide concentrations not higher than 1 wt %. The gel systems were investigated by the dynamic rheology method. The mechanical characteristics of -carrageenan-containing gels were found to be mainly governed by the chitosan content; the viscosity of these gels was independent of temperature. Gels obtained with - and -carrageenans were sensitive to temperature because of the helix–coil conformational transitions in their molecules. The mechanical strength and stiffness of gels increase in the ––-carrageenan series. This effect was explained by the formation of additional crosslinks by double helixes of - and -carrageenan molecules.     

Interactions of amphiphilic drugs withα-,β-, andγ-cyclodextrins

The association of several amphiphilic drugs with -, -, and -cyclodextrins has been measured by use of drug-sensitive electrodes. Drugs investigated are hydrochlorides of chlorpromazine, dibucaine, tetracaine, and procaine, and valethamate bromide. Each drug forms the drug:cyclodextrin=11 complex with - and -cyclodextrin, and both the 11 and 21 complex with -cyclodextrin, except valethamate which only forms the 11 complex. The strength of the 11 complex formations is in the order of CyD>-CyD>-CyD. The association constant of the 21 complex in drug--CyD is larger than that of 11 complex. The free energy change of the conplex formation has a positive correlation with that of the micelle formation of drugs. The deviation from this relation is explained in terms of fittability of the bulky hydrophobic group of drugs into the cyclodextrin's cavity. The free energy change for the complex formation between chlopromazine or valethamate and -CyD is governed by the enthalpy term and not by the entropy term which controls the surfactant--CyD interactions.     

Use of a Packed Minicolumn Connected to a Syringe for Determination of Trace Elements in Biological and Water Samples by Flame Atomic Absorption Spectrometry

In this study, a syringe-connected minicolumn resin was used for the separation and enrichment of cadmium, copper, nickel and zinc prior to their determination by flame atomic absorption spectrometry. The proposed technique was compared with classical batch and column techniques in terms of rapidness, simplicity, enrichment and risk of contamination. The minicolumn was filled with Chromosorb-103 resin and connected to a syringe. If the samples were treated with ammonium pyrrolidine dithiocarbamate or 8-hydroxyquinoline, the analytes were quantitatively retained at pH2 and pH5 on the resin, respectively. On the other hand, if no chelating agent was added, the analytes were quantitatively retained at pH10. The analytes retained by the resin were quantitatively eluted by drawing and discharging nitric acid in acetone. The analytes in spiked river-water samples and in certified standard reference Bovine-Liver (NIST SRM 1577 b) were quantitatively (94%) recovered. The relative standard deviations for the determinations were found to be 1.0–10%.     

Complex formation between polyethylene oxide-containing nonionic surfactants and α- and β-cyclodextrins

The inclusion complexes based on polyethylene oxide (PEO)-containing nonionic surfactants and ()-cyclodextrins (CD) were synthesized. Their composition and crystal structure were studied. The inclusion complexes of the surfactants with -CD form a crystal structure similar to that of the -CD—PEO complex. The inclusion complexes of the nonionic surfactants with -CD form a structure similar to that of the -CD—PEO complex. The structural models of the crystalline complexes were proposed. The micelle-forming abilities of the surfactants in dilute solutions in the presence of CD were studied. The CD binding to a surfactant molecule in aqueous solutions begins from the PEO fragment. Possible reasons for the formation of inclusion complexes between noncomplementary surfactant and -CD molecules were discussed. The thermal stability was studied, and the possibility of thermal dissociation of the pseudo-complementary -CD—surfactant complexes was shown.     

A microcalorimetric study of the different states of argon and nitrogen adsorbed AT 77 K on silicalite-I and ZSM-5

The adsorption of argon and nitrogen on a series of MFI-type zeolites (silicalite-I (Si/Al>1000) and HZSM-5 (16相似文献   

Thermal degradation of single 7-cholesteryl acetate hydroperoxide

Summary The thermal degradation products of the 7- and 7-cholesteryl 3-acetate hydroperoxides obtained by thermal oxidation of cholesteryl 3-acetate are reported and discussed. The hydroperoxides were degraded in both the vapour and condensed phases. The main components identified were 7-ketocholesteryl 3-acetate, 7- and 7-hydroxycholesteryl 3-acetates and the products generated from the loss of the hydroperoxide group and/or of acetic acid. Remarkable is the finding of the epoxy-hydroxy derivatives of cholesteryl acetate among the degradation products.     

Surface Tension and 1H NMR Studies on Inclusion Complexes of β-Cyclodextrin with Sodium Alkyl Sulfonate

The inclusion complexes of -CD with sodium octylsulfonate (C8As), sodium dodecyl sulfonate (C12As), andsodium hexadecyl sulfonate (C16As) in aqueous solutions havebeen studied by surface tension measurement at the air/water interfaceand 1H NMR spectroscopy at 323 K.At fixed concentrations of the surfactants, the surface tensions firstincrease with the increase of -CD concentrations,then they attain a maximum. The surface tension curves of the surfactantsin the presence of -CD are higher than those in the absence of-CD. The values increase with increasing -CD concentrations foreach surfactant. The apparent critical micelle concentrations (CMC) of thesurfactants vary linearly with -CD concentrations.A 1H NMR study shows that the signals of theinner H-3 and H-5 of -CDshift upfield upon addition of the surfactants.The magnitude of the chemicalshift changes (= CD obs)varies as a functionof the concentrations of the surfactants. From therelationships between the chemicalshift changes of H-3 or H-5 inside the -CD cavityand guest/host molar ratios, a 1:1 stoichiometry foreach inclusion complex is assumed. The associationconstants of the inclusion complexes have beendetermined by 1H NMR spectroscopy.     

Total chromatographic optimization (TOCO) I. Simultaneous optimization of many variables in liquid chromatography

Summary The following chromatographic variables are totally optimized based on the recently developed information theory of optimization: mobile phase composition, column length, flow rate, wavelength, and the amount of internal standard. The optimal internal standard is selected from among six candidates. Two types of optimal conditions (- and -optimals) are proposed: the -optimal is defined as the most precise analysis (the maximal ) while the -optimal is the most efficient (rapid) analysis (the maximal ). The observation times for the determination of an antipyretics mixture (three components) in liquid chromatography are ca. 50 s for the -optimal and ca. 8 min for the -optimal. The reliability of the - and -optimals is verified by experiments.     

Electronic structure and models of monooxygenase inductor receptor from a number of polychlorinated polycyclic compounds. 5. MNDO calculations of halogen derivatives of azoxybenzenes

The MNDO method has been used to calculate the electronic and geometric structure of 3,3,4,4-tetraehloroazoxybenzene (TCAOB), 3,3,4,4-tetrachloro-6-hydroxyazobenzene (TCHAB), and 2,3,7,8-tetrachlorodibenzofuran (TCDF). The TCAOB exists in the gas phase in the form of two configurations, one nonplanar and one nearly planar. The latter is approximately 4 kcal/mole less stable than the first. The oxidation of 3,3,4,4-tetrachloroazobenzene (TCAB) to TCAOB is endothermic only in the case of the acton of hydrogen peroxide, not molecular oxygen. The isomerization of TCAOB to TCHAB proceeds with a gain in energy (–62 kcal/mole); however, the reaction from the ground state of the TCAOB molecule is symmetry-forbidden and is possible only from an excited state of the TCAOB. The process of oxidation of TCAOB and TCHAB by molecular oxygen to form TCDF or 2,3,7,8-tetrachlorobenzo-p-dioxin is energy-favorable; this is important in judging the biological action of TCAOB.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 1, pp. 101–105, January, 1991.     

Ruthenium(III)-catalyzed oxidation of substituted ethanols by sodium N-bromo-p-toluenesulfonamide in hydrochloric acid medium

The kinetics of oxidation of substituted alcohols, RCH2CH2OH (R = H-, OEt-, OMe-, NH2-, Cl- and Br-) by sodium N-bromo-p-toluenesulfonamide or bromamine-T (BAT), catalyzed by ruthenium(III) chloride in the presence of HCl, has been studied at 303K. The reaction rate shows first order dependence each on [BAT], [alcohol] and [RuIII]. The reaction rate is inversely dependent on [H+]. Addition of halide ions and the reduction product, p-toluenesulfonamide has no significant effect on the rate. Composite activation parameters H, S and G were computed by studying the reaction at different temperatures (298–313K). The rate decreased in D2O medium and the solvent isotope effect k(H2O)|k(D2O) = 1.63 and 1.68 for EtOH and BrCH2CH2OH respectively. Proton inventory studies have been made in H2O–D2O mixtures for both alcohols. The conjugate acid, TsNHBr, is assumed to be the reactive species. The rates do not correlate satisfactorily with Taft substituent constants. The protonation constant (25.3) of monobromamine-T has been evaluated. From enthalpy-entropy relationships and Exner correlations, the isokinetic temperature () was found to be 368 K, which is much higher than the experimental temperature, indicating that enthalpy factors control the rate. The proposed reaction mechanisms and the derived rate laws are consistant with the observed kinetic data. The rate of oxidation of alcohols RCH2CH2OH follows the order: H > Br > OEt > OMe > Cl > NH2.     

Reactions of Chelates with Macrocyclic Ligands. Complexation between Tetraphenylporphine and Cu(II) Complexes with α-Amino Acids

The reactions of tetraphenylporphine (H₂TPP) with copper(II) chelates in DMSO were studied. -Amino acids (glycine, -alanine, valine, leucine, tyrosine, and glutamine) were used as chelating ligands. The study of the reaction kinetics showed that Cu(II) chelates with alanine and the other amino acids are less reactive in these reactions than acetylacetonates, -nitroso--naphtholates, and hydroxyquinolates. The exception is a Cu(II) complex with tyrosine. The relationship between the structure of the above chelates and the rate of their reactions with porphyrin was determined.     

Inhibitory Effect of Cyclodextrins on the Discoloration Reaction of an Anthocyanidin, Pelargonidin Chloride, in Acidic Media

An anthocyanidin, pelargonidin (PG), loses its color with time in acidic media. The rate determining step of the discoloration reaction at pH 1–4 is the nucleophilic attack of the OH^- ion on PG to give a hemiacetal, which readily isomerizes to the corresponding -diketone. Native, branched, and methylated cyclodextrins (CDs) form inclusion complexes with PG to retard the discoloration. The inhibitory effect (copigmentation) of CDs on the PG discoloration is slight in -CD, significant in - and -CDs, and the largest in heptakis(2,6-dimethyl)--CD (DM--CD). The -CD and DM--CD include the phenyl moiety of PG, whereas -CD includes the benzopyrylium moiety of PG. The CD cavities protect the reaction site of included PG from the attack of the OH^- ion.