Determination of hypaphorine and oligomeric stilbenes in the root of Caragana sinica by capillary electrophoresis with electrochemical detection

Capillary electrophoresis with electrochemical detection (CE-ED) was employed for the determination of hypaphorine (an alkaloid) and four oligomeric stilbenes (including pallidol, kobophenol A, miyabenol C and (+)--viniferin) in Radix seu Cortex Caraganae Sinicae, the root of Caragana sinica (Buc'hoz) Rehd. The effects of several important factors were investigated to find optimum conditions. The working electrode was a 300 μm diameter carbon disc electrode positioned opposite the outlet of capillary. The five analytes could be well separated within 12 min in a 40 cm length capillary at the separation voltage of 12 kV in a 100 mmol l⁻¹ borate buffer (pH 10.0). The response was linear over about three orders of magnitude for all investigated compounds with detection limits (S/N=3) ranging from 0.0385 to 0.111 mg l⁻¹. This proposed method has also been successfully applied to analyze the root of other Caragana plants.     

Analysis of oligomeric and monomeric carbohydrates from hydrothermal degradation of cotton-waste materials using HPLC and GPC

Summary The hydrolysis of different cotton materials under hydrothermal conditions was investigated. For the analysis of the resulting reaction products high-performance liquid chromatography and gel-permeation chromatography were applied. HPLC columns with ion exchange materials as stationary phases (HPX 87P and Shodex S801) enabled the separation of monomeric sugars and degradation products. Oligomeric sugars were analyzed using a gel column (Bio-Gel P-2) as well as a HPLC column (HPX 42A). Through identification of additional reaction products the mass balance of the hydrolysis can be improved and the analysis of the distribution of the oligomeric sugars gives information for the selection of the reaction conditions.     

Synthesis and application of novel fluoroalkyl end-capped cooligomers having adamantane as a pendant group

Fluoroalkyl end-capped cooligomers having adamantane as a pendant group [R_F-(Ad-HAc) _x –(Co-M) _y -R_F] were prepared by the reactions of fluoroalkanoyl peroxide with 3-hydroxy-1-adamantylacrylate (Ad-HAc) and comonomers (Co-M) such as acrylic acid (ACA), N,N-dimethylacrylamide (DMAA), and acryloylmorpholine (ACMO) under mild conditions. Thermogravimetric analyses (TGA) showed that thermal stability of R_F-(Ad-HAc) _x –(Co-M) _y -R_F was superior to that of the corresponding fluoroalkyl end-capped cooligomers having adamantane in the main chains [R_F-(Ad) _x –(Co-M) _y -R_F] and the fluoroalkyl end-capped homooligomers possessing no adamantyl segments [R_F-(M) _n -R_F]. It is interesting to note that fluoroalkyl end-capped Ad-Hac–DMAA cooligomer [R_F-(Ad-HAc) _x –(DMAA) _y -R_F] was found to form the nanometer size-controlled cooligomeric aggregates which consist of around 16 fluorinated cooligomeric molecules in methanol/water mixed solvents. Furthermore, these fluorinated cooligomeric aggregate could occupy around 320 ADMDD [5-(2-adamantylidene)-2,2-dimethyl-1,3-dioxane-4,6-dione] molecules as guest molecules per aggregate core, although ADMDD could not be encapsulated into the R_F-(Ad) _x –(Co-M) _y -R_F cooligomeric and R_F-(M) _n -R_F homooligomeric aggregate cores under similar conditions.     

Study of the mechanism of the emulsifier-free emulsion polymerization of the styrene/4-vinylpyridine system

For the emulsifier-free emulsion copolymerization of styrene with the water-soluble comonomer 4-vinylpyrindine (4VP), and using ammonium persulfate as an initiator, the kinetics, the content of 4VP, the molecular weight and the molecular weight distributions of the polymer at various conversions, and particle morphologies have been investigated. Based on the results obtained, the particle nucleation mechanism was discussed. Received: 9 September 1998 Accepted in revised form: 23 February 1999     

流动注射-抑制化学发光法测定葡萄籽提取物中原花青素

基于在碱性条件下,原花青素对H2O2-Luminol体系有显著的抑制作用,结合反相流动注射技术,首次建立了流动注射-抑制化学发光测定葡萄籽提取物中原花青素的含量;原花青素质量浓度在O．2～20．Omg／L范围与相对发光强度呈线性关系,检出限为O.lmg／L,采样频率为140次／h,对lO．Omg／L的原花青素平行测定11次,其RSD为1．2％,回收率为97％～103％;该方法用于原花青素的测定,结果令人满意。     

Synthesis of Nonionic Oligomeric Manganese(Ⅱ) Complexes and Investigation of Their Toxicity and Τ1-Relaxation Enhancement

Six nonionic oligomeric manganese(Ⅱ) complexes with oligomeric phosphate-polyglycol-EDTA ester ligands were synthesized and characterized. The longitudinal relaxivities of these complexes were measured. One of these complexes, which showed the highest relaxivity, was chosen to be used in the acute toxicity test and the Τ1-weighted imaging experiment. It has been found that compared to Gd-DTPA, this nonionic oligomeric Mn(Ⅱ) complex exhibits no acute toxicity, generates highly enhanced MRI signals and increases the intention time in the rat liver tissue.     

CCD阵列检测-流动注射分析保健食品中原花青素

建立了原花青素的流动注射分析方法。利用原花青素在强酸介质中,铁离子的催化下形成红色花色素,以NH4Fe(SO4)2、盐酸、乙醇的混合溶液为载流,用流动注射-二极管阵列检测器扫描待测物的吸收光谱图,测定最大吸收波长(545 nm)处的吸光度值。优化了影响显色反应的有关因素及流动注射参数,原花青素的浓度在0.010~0.20 mg.mL-1的范围内呈良好的线性关系。方法检出限为5μg.mL-1,加标回收率为82.47%~98.18%,相对标准差1.5%~4.9%。本文所建立的分析方法灵敏、准确,采样频率为10 samples.h-1,并已成功用于保健食品中原花青素的检测。     

Mechanism and prediction of retention of oligomers in normal-phase and reversed-phase HPLC

Summary The simultaneous dependence of the retention in oligomeric series on the number of repeat structural units and on the mobile phase composition may be described by very similar equations for reversed-phase and for normal-phase systems.In reversed-phase systems, the separation selectivity of the individual oligomers is determined mainly by the size and by the polarity of the repeat structural unit, but the influence of a bulky and polar structural residue may also become important so that even reversed order of elution may be observed for oligomeric series with the same oligomeric units but significantly different end groups. For example, oligoethylene glycols are eluted in the order of increasing size of the oligomers, whereas ethoxylated nonylphenols are eluted in the order of decreasing size.In normal-phase systems, the separation selectivity in oligomeric series depends on the adsorption energy and on the adsorbed area of the oligomeric unit. If the oligomeric unit is small, the concentration of the polar solvent in the binary organic mobile phase has only a minor effect on retention and selectivity, which may be controlled by taking account of the nature of the adsorbent and of the polar solvent or by varying the proportion of two polar solvents in a ternary mobile phase.     

Autoxidation of giant extracellular hemoglobin of Glossoscolex paulistus: molecular mechanism and oligomeric implications

Giant extracellular hemoglobins present high redox stability due to their supramolecular architecture, high number of polypeptide chains and great compaction of protein subunits. The oligomeric assembly and the changes in the polypeptidic structure can influence the autoxidation rate of the heme proteins, being that different nucleophiles can act in this process due to pH alterations. In the present work, we have studied the autoxidation rate of whole Glossoscolex paulistus (HbGp) giant extracellular hemoglobin, as well as the autoxidation rate of the isolated d monomer of HbGp studied regarding pH variations. The kinetic decay behavior is dependent on pH, presenting mono-exponential or bi-exponential character, depending on the oligomeric state of the protein. Thus, the oligomeric dissociation in specific pH values demonstrated a bi-exponential kinetic decay. A mono-exponential kinetic behavior was verified in the pH range of 5.9–7.3, which is assigned to the native whole protein. In alkaline medium, the presence of hydroxide ions leads the autoxidation of whole hemoglobin to a complex behavior, which is described by the combination of two first-order kinetics. The slow process occurs due to the d monomer autoxidation. At pH 7.0, the kinetic is mono-exponential, indicating a highly conserved oligomeric structure. In acid medium, the proton-catalyzed autoxidation occurs both on the whole hemoglobin and in the d monomer. It has been found that proximal and distal histidines develop determinant roles regarding the autoxidation rate, being that the distal histidine controls the contact of ligands with the ferrous center through a very interesting “swinging door” mechanism. Despite the significant sensitivity of the distal histidine to the presence of protons, water molecules and anions, the influence of chemical changes around the heme, such as pH changes, is much more effective in hemoproteins without this amino acid as distal residue. This fact denotes the ability of HbGp to adapt to environmental disturbances caused by the presence of the distal histidine, which is responsible for the great redox and oligomeric stabilities encountered in HbGp.