L-谷氨酰胺在强酸性离子交换树脂上的稳定性

研究了谷氨酰胺在强酸性阳离子交换树脂「氢型」上离子交换时的化学稳定性,结果显示,在典型的及所述其他实验条件下,谷氨酰胺相当稳定。典型离交过程：１００ｍｌ去菌体谷氨酰胺发酵液含主要成份谷氨酰胺、谷氨酸和硫酸铵分别为３１２ｍｍｏｌ／Ｌ、６７．０ｍｍｏｌ／Ｌ和０．７５ｍｏｌ／Ｌ,离子交换柱床层体积２００ｍｌ,离交流速１．０ＢＶ／ｈ,０．５ｍｏｌ／Ｌ氨水洗脱流速０．５ＢＶ／ｈ。     

L-谷氨酰胺精制纯化技术研究

研究了将谷氨酰胺粗晶进一步精制纯化使其达到国外质量标准要求的方法,报道了对粗晶谷氨酰胺的脱色条件,粗晶谷氨酰胺溶解液上离子交换树脂柱分离的操作技术和用乙醇析晶后得到的纯品谷氨酰胺的质量情况。     

离子交换吸附L-色氨酸的研究

L-色氨酸是含吲哚环的芳香族氨基酸,也是人类必需的氨基酸之一,目前,工业上除部分采用化学合成法外,主要采用前体发酵法和酶促转化法生产。随着在医药、食品和饲料加工中应用的开拓,市场的需求量日益增加,色氨酸生产具有广阔的前途。     

氨基酸制备色谱-Dpsc离子交换树脂柱分离发酵L-缬氨酸

从苯乙烯、甲基丙烯酸甲酯、二乙烯苯合成了具有磺酸、羧酸功能基团的新型Dpsc离子交换树脂,并对其表征了选择性、分离度、理论等板高度。用新型Dpsc离子交换树脂在制备规模从发酵缬氨酸液中分离制备了L-缬氨酸,应用0.2mo·L-1NH4Cl和0.5mol·L-1NH4OH,流速6.0mL·min-1,温度25℃,梯度洗脱,减少保留体积4/5。     

离子交换法从生产胱氨酸废液中分离提取三种碱性氨基酸

本研究利用国产７３２阳离子交换树脂,从生产胱氨酸废液中提取了三种碱性氨基酸。通过实验确定了洗脱分离三种氨基酸：组氨酸、赖氨酸、精氨酸的较适宜工艺条件,并根据平衡原理和色谱理论探讨了洗脱剂阴离子和ｐＨ值对洗脱分离的影响规律。有如下关系：设单位体积中离子交换树脂吸附总量为Ｑ,则：注＊：Ｋ＝ｐ／ｑｐ、ｑ分别为氨基酸在固定相（树脂）和流动相）（洗脱剂）中所占分数。注：ｎ（ｍａｘ）＝ｒ／ｑ：指洗脱出氨基酸最大浓度时洗脱剂用量。其中γ表示理论塔板数。由（４）式可看出,Ｅ值增大时ｎ（ｍａｘ）减小,即洗脱剂用量减少,由（３）式可知,ｐＨ值直接影响Ｅ值大小,不同ｐＨ条件下对Ｅ的影响如图１。由图１可知,Ｅ值随ｐＨ变化存在一个突跃阶段。恰当地调节ｐＨ值,可大幅度提高洗脱剂的洗脱能力,从而降低洗脱剂用量,降低成本;同时使洗脱后氨基酸与洗脱剂的分离更容易;另外不同的氨基酸由Ｅ值表现出的突跃阶段所对应的ｐＨ范围是不同的,因此可以利用洗脱剂ｐＨ值的改变选择性地洗脱某种特定的氨基酸,使性质类似的三种碱性氨基酸得以分离,由图２表示的实验结果证实了这一点。１．２．洗脱剂中阴离子对阳离子交换树脂洗脱的影响。当洗脱剂阴离子为弱酸根离子（以Ｓ－表示?     

谷氨酰胺发酵条件的研究

以黄色短杆菌ＳＧｒ和ＤＯＮｒ抗性菌株作为生产菌株,在１６升罐对产谷氨酰胺的发酵条件进行了研究。试验结果,产谷氨酰胺５．２２％,周期４４ｈ,转化率３３．３％。该变异菌株具有工业化开发的价值。     

从发酵液中提取谷氨酰胺工艺的改进

为提高谷氨酰胺的提取收率,采用单根弱碱性阴离子交换树脂柱方法来分离提取谷氨酰胺,得到了符合质量要求的谷氨酰胺结晶纯品,采用该法可大量减少酸碱用量并使发酵液中氨酰胺的总提取收率达到57．7％－61．7％。     

肝素纯化工艺中离子交换树脂的选择与应用研究

研究比较了5种树脂对肝素的吸附能力,从中选出S5428阴离子交换树脂来纯化肝素。通过对各因素的研究,确定了树脂对肝素的静态、动态吸附以及解吸的最佳条件。结果表明:静态吸附的温度45℃,pH 8.0的条件下吸附2 h,肝素的吸附率为90.5%;层析柱的动态吸附温度45℃,肝素溶液进样浓度1.0 mg/mL,进样速度1.5 mL/min,树脂柱能处理1.5 BV肝素液而不发生泄露,吸附量为3.05 mg/mL,达到饱和吸附时可处理4BV的料液,吸附量为9.18 mg/mL;采用2.0 mol/L NaCl洗脱,洗脱流速1.5 mL/min,肝素解吸率可达95.8%,肝素效价可达150 U/mg,效价回收率98%。     

Ion exchange of amino acids at a natural organic ion exchanger: Thermodynamics and energetics

The thermodynamics and energetics of the ion exchange of four amino acids at a cellulosic ion exchanger have been studied. Experimental work included determination of ion exchange isotherms and the use of high-sensitivity titration microcalorimetry. A rigorous thermodynamic analysis of the data was developed allowing calculation of the standard free energy, the standard enthalpy, and standard entropy of exchange, and also the differential free energy, incremental enthalpy, and incremental entropy of exchange. The results show that the relative contributions of the enthalpy and entropy to the overall free energy differ markedly for the chosen amino acids. The reasons for these differences are analyzed and discussed. A knowledge of these fundamental thermodynamic properties indicates the solution conditions likely to give enhanced affinity of the ion exchanger for selected amino acids. The experimental techniques and analysis procedures developed are generally applicable to ion exchange separations of biomolecules. (c) 1995 John Wiley & Sons, Inc.     

Taste Mask, Design and Evaluation of an Oral Formulation Using Ion Exchange Resin as Drug Carrier

The purpose of this research was to mask the bitter taste of Diphenhydramine Hydrochloride (DPH) using cation exchange resins. Indion 234 and Tulsion 343 that contained crosslinked polyacrylic backbone were used. The drug resin complexes (DRC) were prepared by batch process by taking drug: resin ratios 1:1, 1:2, and 1:3. The optimum drug: resin ratio and the time required for maximum complexation was determined. The drug resinates were evaluated for the drug content, taste, micromeritic properties drug release and X-ray diffraction (PXRD). Effervescent and dispersible tablets were developed from optimum drug: resin ratios of 1:2 and 1:1. The formulations were evaluated for uniformity of dispersion, disintegration time, and in vitro dissolution. The X-ray diffraction study confirmed the monomolecularity of entrapped drug in the resin beads. The taste evaluation depicted the successful taste masking of DPH with drug resin complexes. The drug release of 95% in 15 min was observed for effervescent and dispersible tablets.     

离子交换法与氨基酸的分离纯化

离子交换法广泛用于氨基酸的分离纯化。文章综述了离子交换法与氨基酸的分离纯化,包括分离纯化单一氨基酸及对氨基酸混合物进行分组分离纯化。     

Assessment of Phytotoxicity of Chromium in Flooded Soils using Embedded Selective Ion Exchange Resin Method

Chromium present in the forms of Cr(VI) or Cr(III) in soils. Since the toxicity and mobility of Cr(VI) are higher than those of Cr(III), it would be important to estimate soil Cr(VI) accurately in order to assess the phytotoxicity of Cr. Soil redox potential can influence the distribution of Cr between Cr(VI) and Cr(III) forms, and thus an in situ method which is not affected by the soil redox condition is needed for determining Cr(VI) availability in paddy fields. In this study, the Cu-saturated selective ion exchange resin (DOWEX M4159), serving as an infinite sink, was embedded in soils to extract available Cr(VI) from three representative saturated soils with different amounts of Cr(VI). The results suggested that Cr(VI) reduction occurred in the flooded soils, and the acid environment favored the adsorption and reduction of Cr(VI). There was a significant dose-response relationship between the soil resin-extractable Cr(VI) and the plant height of rice seedlings for test soils. The experimental results suggested that the embedded selective ion exchange resin method could be a suitable in situ method for assessing the phytotoxicity of Cr in flooded soils.     

Effects of Arachidonic Acid on the Lysosomal Ion Permeability and Osmotic Stability

In this study, we investigated the effects of arachidonic acid, a PLA₂-produced lipid metabolite, on the lysosomal permeability, osmotic sensitivity and stability. Through the measurements of lysosomal β-hexosaminidase free activity, membrane potential, intralysosomal pH, and lysosomal latency loss in hypotonic sucrose medium, we established that arachidonic acid could increase the lysosomal permeability to both potassium ions and protons, and enhance the lysosomal osmotic sensitivity. As a result, the fatty-acid-promoted entry of potassium ions into the lysosomes via K⁺/H⁺ exchange, which could produce osmotic imbalance across their membranes and osmotically destabilize the lysosomes. In addition, the enhancement of lysosomal osmotic sensitivity caused the lysosomes to become more liable to destabilization in osmotic shock. The results suggest that arachidonic acid may play a role in the lysosomal destabilization.     

Using the Selective Ion Exchange Resin Extraction and XANES Methods to Evaluate the Effect of Compost Amendments on Soil Chromium(VI) Phytotoxicity

The Cu-saturated selective ion exchange resin (DOWEX M4195) extraction method was used to investigate the effects of two amendments, 5 and 15% organic matter in the form of hog-dung compost (HC) or cattle-dung compost (CC), on Cr(VI) bioavailability in three soils spiked with various levels of Cr(VI). The results showed that addition of composts could decrease the amounts of resin-extractable Cr(VI) in Cr(VI)-spiked soils, and the CC amendment decreased resin-extractable Cr(VI) more than the HC amendment. The X-ray Absorption Near-edge Structure spectroscopy (XANES) method was used to examine the distribution of Cr(III) and Cr(VI) species in Cr(VI)-spiked soils that were affected by compost amendments, and to elucidate the mechanisms for the decrease of resin-extractable Cr(VI) due to the application of composts. The XANES results suggested that the decrease in the amounts of resin-extractable Cr(VI) after compost addition was mainly due to the reduction of Cr(VI) to Cr(III). The amounts of soil resin-extractable Cr(VI) were also correlated with wheat seedling growth in order to evaluate the effect of compost amendments on decreasing the phytotoxicity of soil Cr(VI). The results showed that there was a sigmoidal relationship between soil resin-extractable Cr(VI) and the plant height of wheat seedlings and the obtained effective concentrations of resin-extractable Cr(VI) resulting in 10 and 50% growth inhibition (EC₁₀ and EC₅₀) were 76 and 191 mg kg⁻¹ respectively. The above results suggested that the resin extraction method was a useful tool for assessing Cr(VI) phytotoxicity and that addition of composts would enhance Cr(VI) reduction to Cr(III) in soils and thus relieve Cr(VI) phytotoxicity.     

Ab initio Models for Six-Center Multiple Proton Exchange and Ion Pair Formation Assisted by Lewis Acids

High level ab initio and density functional calculations, extrapolated to QCISD(T)/6-311+G(3df,2p)//MP2/6-31+G^**+ZPE, reveal that cyclic ion pairs can form in the hydrogen bonded complexes of haloboric acids BH_nX_3-n–HX, X=F, Cl, with Lewis bases HX, H₂O, CH₃OH, and NH₃, even in isolation (e.g., in the gas phase). The intrinsic acidities (deprotonation energies) required for protonation of these bases with formation of gas phase ion pairs are calculated to be <295 kcal/mol for water, <301 kcal/mol for methanol, and <306 kcal/mol for ammonia; such values are common for acidic sites in zeolites. All gas phase ion pairs prefer symmetric bidentate or tridentate structures. In the other cases where hydrogen bonded complexes prevail, symmetric ion pair-like transition structures for multiple hydrogen exchange are computed.Supplementary material to this paper is available in electronic form at http://dx.doi.org/10.1007/s0089400060563