Effect of Ca2+ and Zn2+ on UO2 dissolution rates

The dissolution of UO(2) in a continuously stirred tank reactor (CSTR) in the presence of Ca(2+) and Zn(2+) was investigated under experimental conditions relevant to contaminated groundwater systems. Complementary experiments were performed to investigate the effect of adsorption and precipitation reactions on UO(2) dissolution. The experiments were performed under anoxic and oxic conditions. Zn(2+) had a much greater inhibitory effect on UO(2) dissolution than did Ca(2+). This inhibition was most substantial under oxic conditions, where the experimental rate of UO(2) dissolution was 7 times lower in the presence of Ca(2+) and 1450 times lower in the presence of Zn(2+) than in water free of divalent cations. EXAFS and solution chemistry analyses of UO(2) solids recovered from a Ca experiment suggest that a Ca-U(VI) phase precipitated. The Zn carbonate hydrozincite [Zn(5)(CO(3))(2)(OH)(6)] or a structurally similar phase precipitated on the UO(2) solids recovered from experiments performed in the presence of Zn. These precipitated Ca and Zn phases can coat the UO(2) surface, inhibiting the oxidative dissolution of UO(2). Interactions with divalent groundwater cations have implications for the longevity of UO(2) and the mobilization of U(VI) from these solids in remediated subsurface environments, waste disposal sites, and natural uranium ores.     

Effects of Ca2+ and Mg2+ on defluoridation in the electrocoagulation process

Because aqueous ions can influence the defluoridation of the electrocoagulation (EC) process, the effects of Ca(2+) and Mg(2+) were investigated. The behaviors and mechanisms of EC defluoridation in Ca(2+)-containing systems were different from those in Mg(2+)-containing systems. An increase in Ca(2+) concentration improved the defluoridation efficiency (ε(F)), but it could not change the optimal molar ratio of OH(-) and F(-) to Al(3+) (r(OH+F)). The highest ε(F) can usually be obtained at r(OH+F) = 3 for defluoridation. Only a small portion of Ca(2+) entered into the flocs, and Ca(2+) could not influence the mechanism of EC defluoridation. For the Mg(2+)-containing system, the optimal r(OH+F) increased with increasing Mg(2+) concentration. The optimal r(OH+F) was maintained at 3 after the Mg(2+) concentration was corrected using the obtained correction coefficient of 0.3435. About 50% to 70% of the total Mg(2+) entered into the flocs. From the XRD analysis, it was found that some Mg-Al-F layered double hydroxides (LDHs) were formed by Mg(2+), F(-), and Al(3+) during electrolysis. It is proposed for the first time that the formation of Mg-Al-F LDH is one of the mechanisms for EC defluoridation in systems containing both F(-) and Mg(2+).     

生理条件下PDF对Pb2+、Cu2+、Zn2+、Ca2+的吸附研究

在生理条件下(pH2和pH7，37℃)，用马铃薯膳食纤维(PDF)对金属离了Pb^2 、Cu^2 、Zn^2 、Ca^2 进行吸附试验。结果表明，两种酸度条件下PDF对Pb^2 的吸附较大，对Cu^2 、Zn^2 的吸附较小，对Ca^2 吸附很小；PDF用量增大(减小)，吸附量(qe)减小(增大)。PDF对重金属离了的吸附表明PDF具有较好的生理活性。用作膳食纤维时应根据需求，按照已研究的用量与吸附量关系配制。其吸附作用是化学吸附与物理吸附的综合结果。PDF的疏松结构和红外光谱中较多的醛羧基团证明了这一点。吸附数据线形拟合表明物理吸附符合Ligniur单分子层吸附机理。     

钙和镁型离交树脂的制备及其二混蜜脱盐

比较了镁型和钙型离子交换树脂的制备及其对二混蜜脱钾钠的效果,探讨钙型树脂替代耗用大量Mg^2＋再生剂的传统镁型树脂对二混蜜脱盐以提高糖分回收率的可行性。结果表明,相同的静态吸附和洗脱条件下,钠型BK001树脂对Ca^2＋的吸附量大于Mg^2＋,但Mg^2＋型树脂对二混蜜脱钾钠效果稍好于Ca^2＋型树脂;动态的钙型树脂对二混蜜脱钾钠效果好于静态的镁型树脂。故钙型BK001树脂可用于二混蜜脱钾钠的糖分回收工艺。     

Ca2+、Mg2+及食盐对浸酸铬鞣的影响

研究了水中Ca2+、Mg2+和NaCl的含量对猪皮浸酸铬鞣的影响.通过正交试验和扩大试验研究发现,Ca2+、Mg2+和NaCl对浸酸铬鞣的影响趋势为Mg2+＞NaCl＞Ca2+.当水中Ca2+、Mg2+含量分别达到质量浓度为80 mg/L和30 mg/L时,铬吸收率大于95%,坯革的Ts均达到100℃以上.坯革粒面平细、染色均匀,物理机械性能达到同类产品指标.NaCl质量浓度高于65 g/L时,不利于铬的吸收和结合.试验结果表明水中Ca2+、Mg2+含量分别达到质量浓度为80 mg/L和30 mg/L时,对猪皮浸酸铬鞣无不良影响.     

Uptake of divalent ions (Mn+2 and Ca+2) by heat-set whey protein gels

Divalent salts are used commonly for gelation of polymer molecules. Calcium, Ca(+2), is one of the most common divalent ions that is used in whey protein gels. Manganese, Mn(+2), is also divalent, but paramagnetic, enhancing relaxation decay rates in magnetic resonance imaging (MRI) and can be used as a probe to understand the behavior of Ca(+2) in whey protein gels. The objective of this study was to investigate the diffusion of Ca(+2) and Mn(+2) ions in heat-set whey protein gels by using MRI and nuclear magnetic resonance (NMR) relaxometry. Whey protein gels were immersed in solutions containing MnCl(2) and CaCl(2) at neutral pH. Images obtained with gels immersed in MnCl(2) solution revealed a relaxation sink region in the gel's surface and the thickness of the region increased with time. These "no signal" regions in the MR images were attributed to uptake of Mn(+2) by the gel. Results obtained with CaCl(2) solution indicated that since Ca(+2) did not have the paramagnetic effect, the regions where Ca(+2) diffused into the gel exhibited a slight decrease in signal intensity. The relaxation spectrums exhibited 3 populations of protons, for gels immersed in MnCl(2) solution, and 2 populations for gels in CaCl(2) solution. No significant change in T(2) distributions was observed for the gels immersed in CaCl(2) solution. The results demonstrated that MRI and NMR relaxometry can be used to understand the diffusion of ions into the whey protein gel, which is useful for designing gels of different physical properties for controlled release applications. PRACTICAL APPLICATION: Design of food systems for delivery of bioactive compounds requires knowledge of diffusion rates and structure. Utilizing magnetic resonance imaging the diffusion rates of ions can be measured. Relaxation spectra could yield information concerning molecular interactions.     

金属离子Cu2+、Ca2+和Mg2+对抗蚜威与DNA结合作用的影响

在人体生理酸度(pH7.4)下,运用紫外、荧光光谱法和DNA 熔点实验研究抗蚜威与小牛胸腺DNA 的作用方式以及Cu2+、Ca2+ 和Mg2+ 分别对两者结合的影响。溴化乙锭(EB)竞争实验和DNA 熔点测定结果表明,抗蚜威主要是通过嵌插方式与DNA 碱基发生作用。3 种金属离子均能与抗蚜威络合,络合物的生成使体系的紫外吸收峰强度和形状发生改变,并能不同程度地猝灭DNA-EB 复合物的荧光;Cu2+、Ca2+ 的存在使DNA- 抗蚜威复合物的结合常数呈现先减弱后增强的趋势,而Mg2+ 的参与能增强两者之间的结合。由此推断出,金属离子对抗蚜威与DNA 结合的影响主要取决于金属离子与DNA 的碱基和磷酸基团间结合的相对亲和比。     

烟丝膨胀前后某些重要香味成分和常规成分的分析研究

本文对5种叶组的烟丝在不同膨胀方法下,膨胀前后的22种重要香味成分和糖、氮、烟碱等常现成分进行了分析研究。烟丝经同时蒸馏萃取法抽提并用酸、碱溶液处理后,对中性抽提物用毛细管气相色谱法和气相色谱/质谱法做定性与定量分析。共测定了糠醛等22种重要香味成分的含量,并根据国标测定了总糖、总氮和烟碱的含量。结果表明,烟丝在膨胀后,各种香味成分和常规成分都有不同程度的损失,损失程度与膨胀方法及其工艺条件有关。      

Ca2+对菠萝蛋白酶热稳定性和二级结构的影响

研究了Ca2+对菠萝蛋白酶活性及远紫外圆二色谱的变化.在37℃下,Ca2+与酶作用1h后,5～10mmol/L Ca2+对酶的活性均有促进作用,其中当Ca2+浓度为2mmoL/L时.促进作用最明显.在60℃下,Ca2+浓度为3mmol/L时,对菠萝蛋白酶的热稳定化效果最好,处理100min后仍然能保留68%的活性;菠萝蛋白酶在60℃下活性的半衰期为86min,除Ca2+浓度为1mmoVL外,其他浓度(2、3、4、5mmol/L)的Ca2+与菠萝蛋白酶作用后,酶的半衰期均有所延长.由圆二色谱曲线发现,菠萝蛋白酶在波长209nm与221am处有明显的负峰.与Ca2+作用后菠萝蛋白酶的α-螺旋、β-转角和无规则卷曲均有所变化,其中,在37℃下加入Ca2+后,菠萝蛋白酶的α-螺旋均减少,而β-转角有所增加.在70℃下处理1h,Ca2+对菠萝蛋白酶二级结构也有所影响.无Ca2+处理的菠萝蛋白酶和加入4mmol/L Ca2+的菠萝蛋白酶的α-螺旋分别减少为34.90%和35.60%,而β-转角则有所增加,分别为26.30%和25.10%.圆二色谱结果表明,α-螺旋结构对菠萝蛋白酶的稳定性起关键作用.     

Ca2+激活生物酶对苎麻纤维脱胶的工艺参数优化

利用Ca2+对生物酶进行有效激活,以提高苎麻生物酶脱胶效果,优化脱胶工艺中Ca2+浓度、pH值、通气量等工艺参数,经过Box-Behnken试验设计和SAS软件分析,得出最优工艺条件为:果胶酶、半纤维素酶浓度分别为12、4 mg/mL,酶处理时间5 h,酶处理温度50°C,Ca2+浓度4.23 mg/mL,pH值4.8,通气量9.2 dm3/min.利用最优工艺处理后的精干麻的残胶率为1.96%,断裂强力为64.5 cN,纤维平均细度为0.457 tex.     

采后Ca2+处理对小油菜衰老进程的影响

以白菜型油菜(Brassica campestris L,品种"五月慢",俗称小油菜)为实验材料,以不同浓度的CaCl2溶液作为ca2 来源,研究Ca2 处理对小油菜衰老进程的影响.结果表明:0.25%～0.35%的CaCl2溶液能在一定程度上延长小油菜的贮藏期;用0.3%的CaCl2溶液处理小油菜,测定其细胞膜渗透率,说明在贮藏后期钙能够有效降低膜透性,延缓细胞衰老.     

滩羊肉嫩度形成中Ca2+的信号转导作用

以6月龄滩羊背最长肌为研究对象,测定4 ℃贮藏0,96,192 h时剪切力、线粒体Ca2+水平、钙蛋白酶-1及细胞凋亡效应酶-3活性。基于同位素标记相对和绝对定量技术(iTRAQ)结合多维液相色谱-串联质谱(LC-MS/MS)技术,研究贮藏期间Ca2+信号通路及凋亡调节信号转导通路蛋白质表达量的变化情况。结果表明:4 ℃贮藏期间,滩羊肉剪切力先降低后升高,线粒体Ca2+含量先升高后降低,钙蛋白酶-1活性持续降低,细胞凋亡效应酶-3活性先上升后下降。滩羊肉剪切力与Ca2+水平呈显著负相关,与钙蛋白酶-1活性呈极显著正相关,与细胞凋亡效应酶-3活性呈极显著负相关。蛋白质组学分析表明:Ca2+跨膜转运ATP酶利用ATP水解的能量驱动Ca2+跨膜运输,电压依赖性阴离子通道蛋白贮藏初期上调表达,为Ca2+流入线粒体提供渠道,导致线粒体Ca2+超载、线粒体功能紊乱,使线粒体复合体表达量上升。同时,VDAC异常表达促使CYTC释放至胞浆,最终激活细胞凋亡效应酶-3,水解结构蛋白质。另外,Ca2+可间接导致肌动蛋白表达量下调,引起细胞收缩,从而影响肉的嫩度。本研究结果证实Ca2+在肉品嫩度形成过程中起重要的信号转导作用。     

HYDROLYSIS OF Z-DISC ACTIN BY Ca2+-ACTTVATED PROTEASE1

A 42,000 dalton protein has been identified in chicken breast muscle which differs from actin in that it is soluble at low ionic strength and insoluble in 1 MKI solutions. This protein is readily hydrolysed by Ca⁺⁺-activated neutral protease from chicken breast muscle, and is not present in Ca⁺⁺-activated neutral protease treated myofibrils. This protein may be involved in the integrity of the Z—disc in skeletal muscle.     

Ca2+对双酶法水解玉米淀粉的影响

考察了α-淀粉酶和β-淀粉酶的酶学性质,探讨了Ca^2＋/淀粉于50℃和pH4．5的条件下的β-淀粉酶热稳定性。研究表明,向可溶性淀粉溶液中添加30mmol／LCa^2＋,能大大提高β-淀粉酶的活性和稳定性;而液化过程中的外加Ca^2＋盐可使还原性糖的生成量略有提高。双酶法（α-淀粉酶和β-淀粉酶）水解玉米淀粉液的对照实验显示,向底物中加一定量的钙盐,可以获得更多的可发酵性还原糖。     

Degumming of ramie bast fibers by Ca2+-activated composite enzyme

In recent years, special attention has been paid to the application of biotechnology in the textile industry. In this study, composite enzyme (contained pectatelyase/hemicellulase/laccase) was employed to degum the ramie bast successfully. Interestingly, the activities of enzymes were enhanced by promotion of Ca²⁺ activated remarkably. The test of degummed ramie fiber performance demonstrated that fiber fineness, breaking strength, whiteness, and residual gum of fibers have greatly improved. Further, the structure and morphous of the fibers before and after degumming was examined and analyzed. The results showed that the gum, hemicellulose, and lignin were removed effectively and treated fibers had the typical cellulose I structure suitable for direct textile and other applications. These outcomes suggested that Ca²⁺-activated composite enzyme could degum the gum of ramie bast effectively, which provided a method to improve the quality of ramie fibers and a theoretical basis for flax degumming technique on an environmentally-friendly basis.     

宰后肌肉僵直过程中游离钙离子的作用及影响其变化的因素

游离钙离子在肌肉僵直化过程中起着至关重要的作用。在宰后肌肉僵直过程中游离钙离子的变化与其他的生理生化指标变化的关系进行了研究,并对游离钙离子变化的影响因素进行了阐述。