微胶囊固定的糖甙酶的失活机理研究

在文献 [1 ]的基础上 ,进一步优化了微胶囊包埋糖甙酶的工艺条件。试验了三种成膜材料 :聚烯丙胺盐酸盐(PAAHC)、聚乙烯亚胺 (PEI)和聚乙二醇 (PEG)。实验结果表明 :PEG是一种较合适的包膜材料 ,用 PEG制备的微胶囊在反应开始时有较大的反应速度 ,降低缓冲液的浓度和交联剂的量制备的微胶囊可以有效地提高反应速度。用四种具有不同催化活性的微胶囊的重复使用试验表明 :重复使用的周期相差可达六倍 ,但总的产量大致相同。这一结果说明 ,用微胶囊包埋的葡糖甙酶失活的主要原因不是有机溶剂的影响而是催化作用本身     

Application of a UV–vis detection-HPLC method for a rapid determination of lycopene and β-carotene in vegetables

The purpose of this paper is to optimize an HPLC method for the determination of lycopene and β-carotene in vegetables and compare it with a spectrophotometric standard method. Among the different conditions studied the most suitable ones for our samples were: extraction with hexane/acetone/ethanol (50:25:25 v/v/v), evaporation of the hexane layer, dissolution of the dry extract in THF/ACN/methanol (15:30:55 v/v/v) and injection on a C18 column with methanol/ACN (90:10 v/v) + TEA 9 μM as mobile phase (Φ = 0.9 ml/min) and λ_detection = 475 nm. Samples considered for analysis were: tomato, carrot, pepper, watermelon, persimmon and medlar. The HPLC method proposed showed adequate reproducibility (RSD < 10.5%), accuracy (100–109% recovery) and sensitive detection limits (0.6 μM for lycopene; 0.3 μM for β-carotene), with a simple preparation of the samples (one step direct extraction) and short run times (10 min) for the quantification of lycopene and β-carotene.     

Comparison of 2 electronic cowside tests to detect subclinical ketosis in dairy cows and the influence of the temperature and type of blood sample on the test results

The objective of this study was to determine the suitability of 2 electronic hand-held devices [FreeStyle Precision (FSP), Abbott GmbH & Co. KG, Wiesbaden, Germany and GlucoMen LX Plus (GLX), A. Menarini GmbH, Vienna, Austria] for measuring β-hydroxybutyrate (BHBA) in dairy cows. Three experiments were conducted to evaluate (1) the diagnostic performance of the devices, (2) the effect of the type of blood sample, and (3) the influence of the ambient temperature on the determined results. A total of 415 blood samples from lactating Holstein and Simmental cows were collected and analyzed with both devices (whole blood) and in a laboratory (serum). Correlation coefficients between whole-blood and serum BHBA concentrations were highly significant, with 94% for the FSP and 80% for the GLX device. Based on thresholds for subclinical ketosis of 1.2 and 1.4 mmol of BHBA/L, results obtained with the hand-held devices were evaluated by receiver operating characteristics analyses. This resulted in adjusted thresholds of 1.2 and 1.4 mmol/L for the FSP and 1.1 and 1.3 mmol/L for the GLX device. Applying these thresholds, sensitivities were 98 and 100% for the FSP and 80 and 86% for the GLX device, respectively. Corresponding specificities were 90 and 97% for the FSP and 87 and 96% for the GLX device, respectively. Additionally, concentrations of BHBA were tested with both devices in whole blood, EDTA-added whole blood, and in their resulting serum and plasma, collected from 65 animals. Determined BHBA concentrations were similar within each device for whole and EDTA-added blood, and in serum and plasma, but differed between whole blood and serum and between EDTA-added blood and plasma. Blood samples with low (0.4 mmol/L), medium (1.1 mmol/L), and high (1.6 mmol/L) BHBA concentrations were stored between +5 to +32°C and analyzed repeatedly at temperature levels differing by 4°C. Additionally, devices and test strips were stored at equal conditions and used for measurement procedures. Storage temperature of the devices and test strips did not influence the differences between the results of the laboratory and the devices, whereas the temperature of the blood samples caused significant differences. Although the level of agreement between the laboratory and the GLX device was lower than for the laboratory and the FSP device, both devices are useful tools for monitoring subclinical ketosis in dairy cows. Due to their effects on the determined results, the type and temperature of the tested sample should be considered.     

石英微天平对β-环糊精衍生物分子的识别

在石英晶体谐振器的金电极表面修饰末端含巯基的 β -环糊精衍生物 (β-CDd) ,用石英晶体微天平 (QCM )在线监测苯系和萘系衍生物与之发生包结反应的过程 ,探讨了温度、浓度、取代基数目和位置对包结反应平衡常数和速率常数的影响。结果表明 :所形成的包结配合物的化学计量均为 1∶1;形成动力学过程符合Langmuir吸附方程 ;β -环糊精对客体分子大小、取代基数目、位置等都有良好的选择识别功能。     

基于不完全β分布的二项分布参数的Bayesian估计

将β分布推广到不完全β分布,给出了二项分布的可靠度的先验分布为不完全β分布时的一些结论,并讨论了在基于二项分布可靠性增长模型中的应用.     

Finite strain response, microstructural evolution and β→α phase transformation of crystalline isotactic polypropylene

An experimental study of the finite strain response of annealed α and β crystalline isotactic polypropylene (iPP) was conducted over a range of temperatures (25, 75, 110 and 135 °C) using uniaxial compression tests. Uniaxial compression results indicate nearly identical macroscopic stress vs. strain behavior for α-iPP and for β-iPP to true strains in excess of −1.1 at room temperature despite the different initial morphologies. At larger compressive strains (>1.2), β-iPP shows more rapid strain hardening. The orientation of crystalline planes during straining differs at room temperature from that at high temperature, indicating a change of slip mechanisms as temperature increases. In addition, strain-induced crystallization occurred at the highest temperature examined in α-iPP. A continuous transformation of β crystals to α crystals with inelastic deformation at room temperature was observed and it was facilitated at higher deformation temperatures. Scanning electron microscopy (SEM) observations of deformed β-iPP provide strong evidence that the transformation is achieved via a solid-to-solid mechanism despite the different helical hands in α and β crystal structures. Molecular simulations were used to investigate a conformational defect in the 3₁ helical chains of β-iPP, characterized by a 120° helical jump. The propagation of this conformational defect along molecular chains provides the reversal of helical hand required by the solid-to-solid transformation. The β→α phase transformation in iPP is proposed to be accomplished via a solid transformation that includes slip along β(110) and β(120) planes during shear of the crystal lattice.     

Enhancing electrorheological behaviors with formation of β-cyclodextrin supramolecular complex

According to the point that the host structure and the properties can be easily modified by the formation of host-guest complex, the supramolecular complexes of β-cyclodextrin cross-linking polymer/1-(2-pyridlazo)-2-naphthol (β-CDP-PAN) particles were synthesized. Then the electrorheological properties of the suspensions of β-CDP-PAN particles in silicone oil have been investigated under DC electric fields. It was found that the yield stress of the typical β-CDP-PAN ER fluid was 6.16 KPa in 5 kV/mm, which is much higher than that of pure β-cyclodextrin polymer (β-CDP), that of pure 1-(2-pyridlazo)-2-naphthol (PAN) as well as that of the mixture of the host with the guest (β-CDP+PAN). The structure of β-CDP-PAN was characterized by the fluorescence analysis and IR spectrometry, respectively. The results confirmed that the naphthalene ring of PAN is included in the cavity of β-CDP. Just as expected, the improvement of dielectric constant, conductivity and loss tangent of β-CDP resulted in good ER effect of β-CDP-PAN. Furthermore, it was found that the cross-linking degree (CLD) of the polymer strongly influences the ER behavior of β-CDP-PAN and β-CDP. When CLD remains in the range of 4-6, β-CDP-PAN exhibits much stronger ER effect, and for β-CDP, its suitable range is 5-8.     

Electrochemical and DFT studies of β-amino-alcohols as corrosion inhibitors for brass

The electrochemical performance of 1-diethylamino-propan-2-ol (EAP) and 1,3-bis-diethylamino-propan-2-ol (DEAP) for brass in simulated atmospheric water is evaluated by potentiodynamic curves and electrochemical impedance spectroscopy (EIS). The experimental results show that the investigated compounds, which can effectively retard the anodic dissolution of brass, are anodic inhibitors. Furthermore, the inhibition efficiency of DEAP is higher than that of EAP at the same concentration. This observation is supported by density functional theoretical (DFT) parameters such as the highest occupied molecule energy level (E_HOMO), the lowest unoccupied molecule energy level (E_LUMO), the energy difference (ΔE) between E_HOMO and E_LUMO, Mulliken charges and the HOMO orbital.     

超滤分离里氏木霉木聚糖酶的研究

研究了进料速度、操作压力、木聚糖酶活大小对内切-β-木聚糖酶和β-木糖苷酶超滤分离的影响。结果表明,用超滤的方法可以将内切-β-木聚糖酶和β-木糖苷酶很好地分离,内切-β-木聚糖酶活的收率随着进料速度的提高而增加,当进料速度从 300mL/min 提高到 450 mL/min 时,内切-β-木聚糖酶活的收率从 79.21%提高到 91.35%;内切-β-木聚糖酶活的收率随着操作压力的提高而降低,当操作压力从 4 kPa 提高到15 kPa 时,内切-β-木聚糖酶活的收率从 89.91%下降到 66.48%,而且操作压力越大越容易阻塞超滤膜;内切-β-木聚糖酶活的收率随着酶活的降低而增加,当总木聚糖酶活一定时,木聚糖酶活从 45.18 IU/mL 下降到 22.59 IU/mL 时,内切-β-木聚糖酶活的收率从 82.63%提高到 89.91%,木聚糖酶活较低时,酶液的体积增大,超滤时间过长,也会导致内切-β-木聚糖酶活收率降低。因此,在木聚糖酶活较低的情况下(酶活为22.59 IU/mL),温度为 25℃时,内切-β-木聚糖酶和β-木糖苷酶的适宜的分离条件为:压力为 4 kPa,进料速度为 450 mL/min,内切-β-木聚糖酶活的收率为 91.35%。     

储藏条件对啤酒花化学组成的影响

研究了香型啤酒花扎一(SA-1)和苦型啤酒花奴革特(Nugget)、齐洛克(Ch inook)、马可波罗(M arco Polo)、青岛大花(Tsingdao flower)5个啤酒花品种在不同的储藏条件下其化学组成的变化。这些啤酒花样品分别在-10~-12℃、0~2℃和室温(20℃左右)3种条件下避光保存180 d,并定期对其主要成分α-酸、β酸、啤酒花多酚和储藏指数等指标进行分析。结果表明:样品中的各组分都发生了不同程度的质量劣变,这些变化不仅和储藏条件有关,也与品种有关。室温下储藏的啤酒花的酿造价值下降最为严重,而较低的储藏温度也只能在一定程度上减缓其氧化的速率。香型啤酒花扎一的损失率最高,在室温下储存120 d时,其α-酸的质量分数只有采收时的45.53%;合葎草酮质量分数较低的苦型啤酒花奴革特的损失率最低,在低于2℃的储存条件下,即使保存时间已达到180 d,它也还有采收时α-酸量的77.23%。