meso-四(4-硝基苯基)卟啉(TNPP)分光光度法检测蜂胶中的铅含量

本实验研究了铅与非水溶性试剂meso-四(4-硝基苯基)卟啉(TNPP)的显色反应。采取分光光度法,测定了温度、酸碱度、辅助络合剂的添加等多个方面的因素对络合物的生成量及稳定性的影响,确定了反应进行的最适条件,建立起一种新型的测定蜂胶原料中铅污染程度的分析方法。实验发现,用邻二氮菲、酒石酸钾钠溶液作联合遮蔽剂,在盐酸羟胺存在的条件下,meso-四(4-硝基苯基)卟啉(TNPP)能与铅生成淡黄色络合物,该反应需在50℃水浴中加热20min即可生成完全。实验测得,该络合物的最大吸收波长在673nm处,络合比为1:1,且当铅含量在0～10μg/ml范围内时,测得的标准工作曲线呈线性关系,相关系数为R=0.9865,服从比尔定律。本实验通过传统的干法灰化法消化样品,以达到富集铅离子的目的,操作简单,重现性好,可将其用于食品中痕量铅的测定,结果令人满意。     

meso-四(4-氨苯基)卟啉测定小麦面粉中痕量铅的研究

建立了一种测定小麦面粉中痕量铅的新方法,研究了在Tween-80存在下,铅与非水溶性试剂meso-四(4-氯苯基)卟啉的显色反应条件,提出了一个高灵敏度测定铅的分光光度法.络合物的最大吸收波长为466nm,组成摩尔比为1:1,铅含量在0～6mg/10mL范围内有较好的线性关系,表观摩尔吸光系数为1.74 × 105L·mol-1·cm-1,并将其应用于面粉中痕量铅的测定,结果令人满意.     

铅与meso-四(4-磺酸苯基)卟啉的显色系统研究及其在食品中铅的检测应用

本文采用吸光光度法,研究并优化了了铅与水溶性络合剂meso-四(4-磺酸苯基)卟啉(TPPS4)的显色条件,实验表明,在碱性条件(pH12)下,用邻二氮菲、硫氰酸铵、酒石酸钾钠作联合掩蔽剂,盐酸羟胺作辅助络合剂,铅与TPPS4需12min即可生成淡紫色络合物,该络合物的吸收峰为465nm,络合比为1:1。当铅含量在0～0.2μg/ml范围内时,萃取曲线符合比尔定律,用APDC/MIBK体系萃取样品中的铅离子,与TPPS4络合后比色测定几种食品中的铅,结果可行。     

TNPP(四硝基卟啉)测定奶粉中锌的含量

本实验研究了锌与非水溶性试剂TNPP(四硝基卟啉)的显色反应。采取分光光度泫,测定了酸碱度、放置时间等多个方面的因素对络合物的生成量及稳定性的影响,确定了反应进行的最适条件,建立测定食品中锌含量的分析方法。实验发现,在盐酸羟胺存在的条件下,TNPP(四硝基卟啉)能与锌在微酸性介质(pH6)中生成淡紫色络合物,该反应在60℃下只需在加热15min即可生成完全,经实验测得,该络合物的最大吸收波长在536nm处,络合比为1∶1,且当锌含量在0～10μg／ml范围内时,测得的曲线呈线性关系,服从比尔定律。并将其用于食品中痕量锌的测定,结果令人满意。     

Meso-四-(3,5-二溴-4-羟基苯)卟啉分光光度法测定虾中铅的含量

研究了溴代卟啉试剂meso-四-(3,5-二溴-4-羟基苯)卟啉分光光度法测定虾中铅的含量.应用分光光度计测定了meso-四-(3,5-二溴-4-羟基苯)的用量、氢氧化钠及增敏剂的用量、温度、时间等5个因素对生成配合物的影响,确定了反应进行的最佳条件,建立起一种的测定虾中铅含量的方法.在本实验条件下,所得的最佳参数为:0.3mol/L NaOH的用量为0.40mL,沸水浴加热时间为3min.实验测得,生成配合物的最大吸收波长在479nm处,铅含量在0.1～1.0μg/mL范围内服从比尔定律,标准曲线的回归方程为:y=0.9237+0.0115(R=0.9995),表观摩尔系数为1.528×108L/(mol· cm).本实验采用传统的干法灰化法消化样品,沉淀法富集铅离子,操作简单,重现性好,用于虾中铅的测定,结果令人满意.     

水溶性meso-四(4-氯-3-磺酸钠基苯基)卟啉测定食品中铅(Ⅱ)含量的研究

研究了meso-四(4-氯-3-磺酸钠基苯基)卟啉(p-C1TPPS4)与铅(Ⅱ)显色反应.结果表明,不需加热即可完成络合,表观摩尔吸光系数2.51×105L/mol·cm,线性范围为0～6 μg/10ml,抗干扰能力强.应用该方法首次测定食品中痕量铅(Ⅱ),结果令人满意.     

5、10、15、20-四-(对-三甲铵苯基)卟吩分光光度法测定蜂蜜中的微量铅

<正> 近年来国内已开始应用卟啉类试剂测定多种金属元素,武汉大学化学系已用自己合成的四-(对-三甲铵苯基)卟吩(简称卟啉),以离子交换分离干扰元素后测定了铅,并研究了在催化剂存在下测定水样中的锌。作者用此试剂测定出口蜂蜜中的锌时,可以不分离基质而直接测定,但测定铅时,遇到样品基质的干扰。本工作对样品处理上作了些试验。曾经发现祥品存在还原糖等还原物质时,能阻止卟啉—铅络合物的形成。因而提出加入适量     

四-(4-三甲铵苯基)卟啉测定食品中的超痕量锌

以水溶性α,β,γ,δ-四-(4-三甲铵苯基)卟啉[T-4-TAP)P]作显色剂,测定食品中的痕量锌。对实验条件及共存离子的干扰进行了探讨。室温下,在弱酸性介质中,经7-碘-8羟基卟啉-5-磺酸催化,反应生成1:1络合物。最大吸收波长为422nm摩尔吸收系数为4.0×10~5 1·mo1~(-1)·cm~(-1),桑德尔指数为0.16ng·cm~(2-1),变异系数为1.6—3.7%,回收率为90.8%。本方法适用于分析食品中的痕量锌。     

卟啉分光光度法测定豆类微量Cu(Ⅱ)含量

以meso-四(4-氯-3-磺酸钠基苯基)卟啉为显色剂,采用分光光度法,研究了该试剂与Cu(Ⅱ)络合反应,以及各种因素对吸光度的影响,从而确定了最佳测定条件.在pH条件为5.0、β-环糊精、盐酸羟胺介质中沸水浴加热5 min,卟啉与Cu(Ⅱ)可完全络合.络合后再加入(1+1)HCl,在423 nm处测定络合物的吸光度,表观摩尔吸光系数为4.12×105L·mol-1·cm-1,线性范围为0～1.2 μg/10mL,抗干扰能力强.该法首次应用于测定豆类中微量Cu(Ⅱ)含量,测定结果满意,有利于建立适合小企业采用的微量铜测试方法.     

四-(对甲基苯基)-卟啉柱前衍生,高效液相色谱法测定食品中痕量铅、镉、汞

研究了用四-(对甲基苯基)-卟啉柱前衍生,高效液相色谱法测定食品中痕量铅、镉、汞的方法。食品样品用湿法消化后,消化液中的铅、镉、汞用四-(对甲基苯基)-卟啉(T4MPP)柱前衍生,然后用甲醇(内含0.01mol/L四氢吡咯-醋酸缓冲盐)和四氢呋喃(内含0.01mol/L四氢吡咯-醋酸缓冲盐)为流动相梯度洗脱,WatersXterraTMRP18(3.9150mm,5μm)色谱柱为固定相分离铅、镉、汞的T4MPP络合物,用二极管矩阵检测器检测,铅、镉、汞含量在0.01～3mg/L范围内与峰面积成线性关系,根据信噪比(S/N=3),方法检测限为:铅2.3μg/L、镉1.8μg/L和汞2.5μg/L,方法相对标准偏差为2.1%～3.5%,标准回收率为93%～106%,该方法用于测定食品中的铅、镉、汞,结果令人满意。     

响应面法优化水溶性大豆多糖- 铁(Ⅱ)配合的合成工艺

优化水溶性大豆多糖-铁(Ⅱ)配合物的合成工艺,在单因素试验基础上,应用响应面法二次回归正交旋转组合试验设计,分析水溶性大豆多糖与催化剂柠檬酸三钠的质量比、pH值、反应时间及温度对配合物铁含量的影响,建立相应的预测模型。方差分析结果表明：质量比、pH值对铁含量有显著影响。优化所得的较优工艺参数为水溶性大豆多糖与柠檬酸三钠质量比1.89:1、pH3.89、反应时间1.56h、温度60.6℃。对应的铁含量的预测值为23.08%,实际平均值为21.89%。结果表明：应用响应面法所得到的水溶性大豆多糖-铁(Ⅱ)配合物的合成工艺参数是可行的。     

Cleavage of thiamine pyrophosphate by sulfite in saccharomyces cerevisiae

Summary Sulfite at low concentrations ( 1 mM caused a cleavage of thiamine in vitro depending upon time, pH value, and temperature. Thiamine monophosphate (TMP) and thiamine pyrophosphate (TPP) were also cleaved, but the reaction rates were slower. For the separation and determination of thiamine, TMP and TPP in yeast high-performance liquid chromatography (HPLC) was used. Thiamine and its phosphate esters were converted into the corresponding fluorescent thiochrome derivatives by alkaline oxidation, adsorbed on an amino-phase HPLC column and eluted with acetonitrile/100 mM-potassium phosphate buffer, pH 7.5 (40+60, v/v) as solvent system. In yeast TPP represented about 73% of the sum of all thiamine compounds, thiamine and TMP 26% and 1%, respectively. During long-term incubations of yeast (up to 24 hours) 2 mM-sulfite decreased the intracellular content of TPP and also of ATP depending upon the pH value of the medium. The decreasing effect of sulfite on the ATP content was faster and stronger than on the TPP content. Two TPP-dependent enzymes, pyruvate decarboxylase [EC.4.1.1.1] and transketolase [EC.2.2.1.1] were inactivated by sulfite within 1 hour to 58% and 13% of the initial values, respectively.

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Thiaminpyrophosphatspaltung durch sulfit in saccharomyces cerevisiae

Zusammenfassung Zur Spaltung von Thiamin in vitro genügen geringe Sulfitkonzentrationen (1 mM). Das Ausmaß der Spaltung hängt ab von der Zeit, der Temperatur und vom pH-Wert. Gespalten werden auch Thiaminmonophosphat (TMP) und Thiaminpyrophosphat (TPP), wenn auch mit geringerer Reaktionsgeschwindigkeit. Zur Trennung and Bestimmung des Thiamins and seiner Phosphatester in Hefe wurde eine HPLC-Methode angewandt. Thiamin, TMP and TPP wurden durch alkalische Oxidation in die entsprechenden fluorescierenden Thiochromderivate umgewandelt, dann an einer HPLC-Saule mit Aminophase adsorbiert und mit Acetonitril/100 mM-Kaliumphosphatpuffer, pH 7,5 (40+60, v/v) als Laufmittel eluiert. In Hefe lagen 73 % der Summe aller Thiaminverbindungen als TPP, 26% als Thiamin und 1% als TMP vor. Im Verlauf von Langzeitinkubationen (bis zu 24 Stunden) von Hefezellen mit 2 mm-Sulfit verringerte sich deren Gehalt an TPP und auch an ATP stark, und zwar in Abhängigkeit vom pH-Wert des Mediums. Der Verlust an ATP erfolgte rascher und in größerem Umfang als der Verlust an TPP. Durch Sulfit wurde die Aktivitat zweier von TPP als Cofaktor abhängiger Enzyme, der Pyruvatdecarboxylase [EC.4.1.1.1] und der Transketolase [EC.2.2.1.1] auf 58% bzw. 13% reduziert.

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Abbreviations used: HPLC high performance liquid chromatography - TMP thiamine monophosphate - TPP thiamine pyrophosphate - TTP thiamine triphosphate     

Preparation of galactosylated chitosan/tripolyphosphate nanoparticles and application as a gene carrier for targeting SMMC7721 cells

Nanoparticles composed of galactosylated chitosan (GC) and tripolyphosphate (TPP) were prepared and their application as potential gene carriers for targeting SMMC7721 cells was investigated. The results showed that at certain pH (5.5-6.2) of GC solutions, small and stable nanoparticles were obtained at an optimal weight ratio of 5:1 (GC/TPP). Transmission electron microscope (TEM) revealed formation of spherical particles. The optimal pH of cell culture environment for transfection was from 6.4 to 6.7, which was the same pH as the polymer complex formation of GC/TPP solutions. The charge ratio of GC/TPP to DNA (N/P) at 10:1, 20:1 and 30:1 were checked for transfection and under optimized conditions, the GC/TPP-DNA nanoparticles successfully transfected 6.8% of the SMMC7721 cells as represented by overexpression of enhanced green fluorescent protein (EGFP), which showed a much more higher efficiency when compared to 0.6% of GC/DNA transfection under the same conditions. The presented results indicate that the GC/TPP nanoparticles might be very attractive to be used as a gene delivery carrier for hepatocyte targeting, thus warranting further in vivo or clinical investigations.     

Tripolyphosphate hydrolysis by bovine fast and slow myosin subfragment 1 isoforms

Polyphosphates are used in the meat industry to increase the water holding capacity of meat products. Tripolyphosphate (TPP) is a commonly used polyphosphate and it is metabolized into pyrophosphate and monophosphate in meat. The enzymes responsible for its metabolism have not been fully characterized. The motor domain of myosin (subfragment 1 or S1) is a likely candidate. The objectives of this study were to determine if bovine S1 hydrolyzes TPP, to characterize the TPPase activity of the fast (cutaneous trunci) and slow (masseter) isoforms, and to determine the influence of pH on S1 TPPase activity. S1 hydrolyzed TPP and in comparison with ATP as substrate, it hydrolyzed TPP 16–32% more slowly. Fast S1 hydrolyzed both substrates faster compared to slow S1 and the difference between the isoforms was greater with TPP as the substrate. The V_max was 0.94 and 5.0 nmol Pi/mg S1 protein/min while the K_m was 0.38 and 0.90 mM TPP for slow and fast S1, respectively. Pyrophosphate was a strong inhibitor of TPPase activity with a K_i of 88 and 8.3 μM PPi for fast and slow S1 isoforms, respectively. Both ATPase and TPPase activities were influenced by pH with the activity being higher at low pH for both fast and slow S1 isoforms. The activity at pH 5.4 was 1.5 to 4-fold higher than that at pH 7.6 for the different isoforms and substrates. These data show that myosin S1 readily hydrolyzes TPP and suggest that it is a major TPPase in meat.     

Interfacial and Foaming Properties of Two Types of Total Proteose-Peptone Fractions

Total proteose-peptone (TPP) fractions were extracted from skimmed milk (UHT) and whey protein concentrate (WPC) on a laboratory scale. Protein solutions (0.1 %, 0.5 %, and 1 % w/w) were characterized as function of pH: 4.0, 4.6–4.7 (native pH), and 7.0. Their foaming capacities and stabilities were studied. Beforehand, the surface properties that govern them were investigated, notably the kinetics of adsorption and mechanical properties of monolayer films at the air–water interface involved in the formation and the stability of foams respectively. The TPP extracted from skimmed milk showed the lowest values as well as a significant reduction in surface tension and presented a good mechanically resistant film. The TPP extracted from WPC presented a better foaming capacity and stability which was unexpected. However, foaming properties and surface properties of TPP fractions depended on the pH. The considerable influence of extraction source and method on proteose-peptone’s properties were highlighted.     

pH值过程控制优化低聚异麦芽糖铁配合物的制备工艺

以低聚异麦芽糖和三氯化铁为原料,以铁含量、产率和反应时间为指标,采用pH值过程控制来制备低聚异麦芽糖铁配合物,筛选出最佳的工艺条件;以粒径、Zeta电位、多分散指数、电导率来展现最佳工艺条件下反应过程的变化情况,并用红外光谱和差示扫描量热分析对最佳工艺条件下制备的产物进行表征。结果表明：当反应起始pH 12.1、反应过程pH值控制为11.5时,制得的低聚异麦芽糖铁配合物的铁含量可达43.16%,产率为96.35%,反应时间缩短为1 h,相比于未控制反应过程pH值的工艺（铁含量为37.14%,反应时间为2.7 h）,铁含量提高了16.21%,反应时间缩短了62.96%,低聚异麦芽糖与Fe3＋发生了配位反应,表明该工艺具有较高的应用价值。     

Effect of Phosphate Type and Concentration, Salt Level and Method of Preparation on Binding in Restructured Beef Rolls

The effect of combinations of phosphate type [tetrasodium pyrophosphate (PP), sodium tripolyphosphate (TPP), sodium tetrapolyphosphate (TTPP), and sodium-hexametaphosphate(HMP)], phosohate concentration (0.125%-0.500%). and salt level (0.6%-2.0%) on the binding in restructured beef rolls was studied. The rolls were prepared either with or without a homogenate that contained all the added salts. Preparation method had little effect on binding. The effectiveness of the phosphates was: PP > TPP > TTPP > HMP. Changes in binding produced by varying phosphate type, phosphate concentration and salt level could be explained in terms of changes in ionic strength and pH. Between 90% and 96% of the variation in binding could be explained in terms of these two variables.     

Simple Method for Measuring the Peroxide Value in a Colored Lipid

We developed a simple method for quantification of the peroxide value (PV) in colored lipids on the basis of the reaction between triphenylphosphine (TPP) and oxidized oil to afford triphenylphosphineoxide (TPPO). Diphenylphosphineoxide (DPPO) was employed as internal standard. The formed TPPO was analyzed by high-pressure liquid chromatography–UV spectroscopy with absorption at 260 nm. The conditions that gave the highest correlative calibration curve between the peak area on the chromatogram and peroxide value were identified: the optimum TPP–oxidized oil mix ratio, reaction temperature, and reaction time were found to be 2:1, 40 °C, and 30 min, respectively. Linear calibration curves, passing through the origin, were obtained for PV versus TPPO and TPPO versus DPPO. The quantification limit for this method was 2.01 pmol hydroperoxyl group, which corresponds to a PV value of 0.2 meq/kg in a 10-mg oil sample. This method was used to measure the PV in colored fats and oils or lipids extracted from dark meat and processed food containing a coloring agent. Though the official method could not measure the PVs in the colored lipids, the method proposed here, which uses an inexpensive chemical reagent and machine, could. The developed method could play an important role for food quality control.