微量光度滴定法测定咔咯化合物的质子化和去质子化常数

采用微量光度滴定法测定了两种具有不同取代基的新型咔咯化合物,三(4-氯苯基)咔咯(化合物1)和三(2,4-二氯苯基)咔咯(化合物2)在非水溶剂中的质子化和去质子化常数。结果表明:化合物1和化合物2在二氯甲烷中均可以与三氟乙酸反应得到一个质子生成正一价阳离子,其质子化常数(lgKb)分别为4.2和4.0。在甲醇溶液中,化合物1和化合物2与氢氧化钠反应时可以失去一个质子生成负一价阴离子,其去质子化常数(lgKa)分别为3.4和3.5。而在二氯甲烷中与碱反应时,化合物1和化合物2均能够一步失去两个质子生成负二价阴离子,其累积去质子化常数(lgβ2)分别为7.9和11.0。     

金属硫蛋白加质子常数及与Cd(II)络合常数测定

用pH计和Cd离子选择电极测定了金属硫蛋白的加质子常数及其与Cd(Ⅱ)的络合常数, 用改进的简化络合模型处理实验结果, 得到了去金属硫蛋白(apo MT)中6类不同的加质子基团的数目及其加质子常数。对Cd(Ⅱ)滴定数据的计算表明, MT中两个结构域——α和β对Cd(Ⅱ)的络合常数相差约1000倍。从热力学定量描述了MT中两个结构域结合金属离子选择优先顺序。     

The Determination of the Protonation Constants of A New Macrocyclic Dinucleating Ligand, BDBPH

One of our current interests focuses on the design and synthesis of polyaza macrocyclic ligands, the determination of their protonation constants, and the stabilities of corresponding metal complexes. Two polyazadiphenol macrocycles, R(babp)2(dfc)21 and [24]RBPyBC2, one octaazamacrocycle, BPBD3,4, and several hexaaza macrocyclic ligands, BFBD5, BMXD6, and OBISDIEN7, have been reported recently. We have also reported the synthesis of a new dinucleating 24-membered hexaazadiphenol macr…     

氨基酸质子化反应的滴定量热测定

在298．2K和0．1mol•dm－3（KNO3）离子强度的实验条件下，用常规滴定量热法测定了八种氨基酸羧基质子化反应的平衡常数和反应焓变；用扩展的滴定量热法测定了这些氨基酸氨基质子化反应的平衡常数和反应焓变；并讨论了各热力学性质之间的关系．     

Critical Evaluation of Protonation Constants. Literature Analysis and Experimental Potentiometric and Calorimetric Data for the Thermodynamics of Phthalate Protonation in Different Ionic Media

The protonation constants of phthalate were determined in aqueous NaCl (0.1 ≤ I ≤ 5,mol⋅L⁻¹) and in aqueous Me₄NCl (0.1 mol⋅L⁻¹ ≤ I ≤ 3,mol⋅L⁻¹) at t = 25,^∘C. Experimental data were employed in conjunction with literature data from studies in different ionic media (Et₄NI: 0 ≤ I ≤ 1,mol⋅L⁻¹; NaClO₄: 0.05 mol⋅L⁻¹ ≤ I ≤ 2,mol⋅L⁻¹)to study the dependence on ionic strength using different models, such as the SIT and Pitzer equations, and an Extended Debye-Hückel type equation. Experimental calorimetric data in NaCl and protonation constants at different temperatures in Et₄NI (5 ≤ t ≤ 45^∘C) and in NaClO₄ (15 ≤ t ≤ 35 ^∘C) were also used to study their dependence on temperature. Recommended equilibrium data are reported together with a short discussion of a prospective protocol for drawing these data.     

高效液相色谱法测定羊水中兴奋性氨基酸、抑制性氨基酸的含量

建立了反相高效液相色谱法测定羊水中兴奋性氨基酸天门冬氨酸、谷氨酸,抑制性氨基酸甘氨酸含量的方法,色谱柱为LUNAC18柱(4.6mm×250mm,5μm),流动相为乙腈水(V/V),按低压梯度洗脱,梯度系统0～4min,乙腈40%;4～20min,乙腈40%～52%;20～30min,乙腈52%～60%;30～40min,乙腈60%～40%。流速0.8mL/min,柱温40℃,紫外检测波长260nm;进样量10μL。结果显示,天门冬氨酸、谷氨酸和甘氨酸三者的线性范围均为2.5～85mg/L;标准加入的回收率为99.6%～102.6%。本方法灵敏度高、测定结果可靠。用本方法对201例不同孕期的羊水作兴奋性和抑制性氨基酸检测,发现羊水中3种氨基酸随妊娠进展而增加的趋势,胎儿畸形或宫内缺氧时羊水中这3种氨基酸水平明显升高。     

聚天冬氨酸酸解离常数的测定

采用pH电位滴定法，利用先进的BEST程序，针对聚羧酸在水溶液中解离及平衡常数测定的复杂性，构建了聚天冬氨酸（PASP）在水溶液中解离的H4L和H2L两种模型，分别测得了相应的各级酸解离常数，并得到了PASP在不同pH条件下的物种分布曲线。在35℃，I=0．1时，对于H4L模型，各级酸解离常数的pK,值为：2．27、3．66、4．22、5．40；对于H2L模型，相应的pK,值为2．92、4．84。研究结果表明，两种模型计算结果均能与实验结果很好吻合，但H4L模型误差更小，因此是一种更为合理的模型。     

异丙基膦酸单(1-已基-4-乙基)辛酯的某些基本常数的测定

用两相滴定法测定异丙基膦酸单（１－己基－４－乙基）辛酯（ＰＴ－２，ＨＬ）在水中的溶解度Ｓ，在水中的解离常数Ｋ在水－正庚烷中的分配常数Ｋｄ及二聚常数Ｋ２，利用ＳＯＬＷＲ计算程序，简单快速地处理两相滴定数据，得到结果为：Ｓ＝３．６８ × １０－５ｍｏｌ／Ｌ，ｐＫａ＝５．４９，ｌｏｇ Ｋ２＝４． ６７，ＩｏｇＫｄ＝ ２． ６７（２５±０． ５℃）．     

新型2-苯并噻唑磺酰脲氨基酸及其甲酯衍生物的合成与抗肿瘤活性

以2-巯基苯并噻唑为原料,经弱氧化和氨化制得2-苯并噻唑次磺酰胺（2）; 2经高锰酸钾氧化制得2-苯并噻唑磺酰胺（3）; 3与氯甲酸乙酯反应制得2-苯并噻唑磺酰胺甲酸乙酯（4）; 4与L-氨基酸甲酯反应制得一系列2-苯并噻唑磺酰脲氨基酸甲酯（6a~6j）; 6经水解合成了10个新型的2-苯并噻唑磺酰脲氨基酸（7a~7j）,其结构经¹H NMR, IR和ESI-MS表征。并研究了6和7对Cdc25B的抑制活性。结果表明:在用药浓度为20 μg·mL^-1时,6c, 6j, 7d, 7h和7j对Cdc25B抑制活性较好,抑制率分别为78.1%, 71.2%, 65.6%, 57.2%和65.9%。     

Hydrolysis of Lipophilic Amino Acid Esters Catalyzed by Metallomicelles

Metallomicelles as the model of hydrolytic metalloenzymes have begun recently¹. Examples are the metal-ion complexes of lipophilic imidazoles² and pyridines³ co-micelled with surfactants. Herein we report the complexes of a novel macrocyclic 12-membered di-oxotetraamine ligand bearing bis-hydroxy groups as functional pendants which can mimic the catalytic function of carboxypeptidase A in micellar media.     

Exotic Amino Acids. 8. Synthesis of Monomethyl Esters of N-Arylaminomethylenemalonic Acids

N-Arylaminomethyleneisopropylidenemalonates, obtained from ethoxymethyleneisopropylidenemalonate and aromatic amines, underwent methanolysis to form monomethyl esters of N-arylaminomethylenemalonic acids. The conditions of their formation and their yields depend on the nature and positions of the substituents in the aromatic ring of the initial amine.     

An Investigation of Protonation Sites and Conformations of Protonated Amino Acids by IRMPD Spectroscopy

The protonation sites and structures of a series of protonated amino acids (Gly, Ala, Pro, Phe, Lys and Ser) are investigated by means of infrared multiple‐photon dissociation (IRMPD) spectroscopy and electronic‐structure calculations. The IRMPD spectra of the protonated species are recorded using the combination of a free‐electron laser (FEL) and an electrospray‐ion‐trap mass spectrometer. The structures of different possible isomers of these protonated species are optimized at the B3LYP/6‐311+G(d, p) level of theory and the IR spectra calculated using the same computational method. For every amino acid studied herein, the current results indicate that a proton is bound to the α‐amino nitrogen, except for lysine, in which the protonation site is the amino nitrogen in the side chain. According to the calculated and experimental IRMPD results, the structures of the protonated amino acids may be assigned unambiguously. For Gly, Ala, and Pro, in each of the most stable isomers the protonated amino group forms an intramolecular hydrogen bond with the adjacent carbonyl oxygen. In the case of Gly, the isomer containing a proton bound to the carbonyl oxygen is theoretically possible. However, it does not exist under the experimental conditions because it has a significantly higher energy (i.e. 26.6 kcal mol^?1) relative to the most stable isomer. For Ser and Phe, the protonated amino group forms two intramolecular hydrogen bonds with both the adjacent carbonyl oxygen and the side‐chain group in each of the most stable isomers. In protonated lysine, the protonated amino group in the side chain forms two hydrogen bonds with the α‐amino nitrogen and the carbonyl oxygen, which is a cyclic structure. Interestingly, for protonated lysine the zwitterionic structure is a local minimum energy isomer, but the experimental spectrum indicates that it does not exist under the experimental conditions. This is consistent with the fact that the zwitterionic isomer is 9.2 kcal mol^?1 higher in free energy at 298 K than the most stable isomer. The carbonyl stretching vibration in the range of 1760–1800 cm^?1 is especially sensitive to the structural change. In addition, IRMPD mechanisms for the protonated amino acids are also investigated.     

在胆汁酸盐背景中n种氨羧配位剂的加质子常数及其钙配合物稳定常数

为测定在胆酸盐和脱氧胆酸盐存在下氨提配位剂的加质子常数和钙配合物稳定常数,对常规电住法做了一些修正。用所建立的方法测定了EDTA、DTPA、EGTA及NTA的有关常数及其随胆汁酸浓度的变化。     

Lactonization and Protonation of Gluconic Acid: A Thermodynamic and Kinetic Study by Potentiometry,NMR and ESI-MS

In acidic aqueous solutions, the protonation of gluconate is coupled with the lactonization of gluconic acid. With a decrease of pC _H, two lactones (δ- and γ-) are sequentially formed. The δ-lactone forms more readily than the γ-lactone. In 0.1 mol⋅L⁻¹ gluconate solutions, if pC _H>2.5 then only the δ-lactone is generated. When the pC _H is decreased below 2.0, formation of the γ-lactone is observed although the δ-lactone still predominates. In solutions with I=0.1 mol⋅L⁻¹ NaClO₄ and room temperature, the deprotonation constant of the carboxylic group was determined to be log ₁₀ K _a=3.30±0.02 using the NMR technique, and the δ-lactonization constant obtained by batch potentiometric titrations was log ₁₀ K _L=−(0.54±0.04). Using ESI-MS, the rate constants for the δ-lactonization and the reverse hydrolysis reaction at pC _H≈5.0 were estimated to be k ₁=3.2×10⁻⁵ s⁻¹ and k ₋₁=1.1×10⁻⁴ s⁻¹, respectively.     

一些土壤和有机肥中氨基酸测定方法研究

一些土壤和有机肥中氨基酸测定方法研究袁吕江，熊凤麒，王正银（西南农业大学中心实验室重庆６３０７１６）（西南农业大学土化系重庆６３０７１６）关键词液相色谱法，氨基酸，土壤，有机肥１前言我国耕作土含氮量为０．４～３．８ｇ／ｋｇ［１］，其中９０％～９８％为...     

Catalytic Hydrolysis of Lipophilic Amino Acid Esters by Metallomicelles as Carboxypeptidase A Models

Metallondcellesasthemodelofhydrolyticmetalloenzymes.havebegunrecently'.Exam-plesarethemetal-ioncomplexesoflipophilicinddazoles2andpyridines'co-ndcelledwithsurfactantS.Hereinwereportthecomplexesofanovelmacrocyclicl2-membereddioxotetradrineligandbearingbis-hydroxygroupsasfunctionalpendantSwhichcanmindcthecatalyticfunctionofcarboxypeptidaseAinndcellarmedia.2,6-Dioxo-l,4,7,lo-tetraazacyclo1(O.2Og,1.onuno1)'anddodecylglycidylether(O.54g,2.2nunol)'wererefluxedinEtOH(3OoInL)for24h.Thesolventwase…     

4-二甲基氨基吡啶催化合成N-保护氨基酸三氟乙酯

合成了6个未见文献报道的N-保护氨基酸三氟乙酯。4-二甲基氨基吡啶对N-保护氨基酸三氟乙酯的合成具有较高的催化活性,使三氟乙酯的合成产率大大增加。     

氨基膦酸及其酯的合成

综述了α－氨基膦酸及其酯的合成方法,介绍了近年来发展的不对称合成法,并对各种方法的优劣作了评述。     

高效液相色谱化学发光检测法测定氨基酸

本文根据铜与氨基酸组成的１：１不饱和络合物对Ｌｕｍｉｎｏｌ－Ｈ２Ｏ２化学发光体系的催化活性，设计了一种新型氨基酸高效液相色谱化学发光检测器，即在色谱柱后安装一个氢氧化铜柱，从柱后流出的氨基酸通过氢氧化铜柱时，产生配合溶解形成氨基酸－铜（１：１）络合物，进行化学发光检测，１４种常见氨基酸的检测限均在ｐｍｏｌ级，已用于血清、尿和啤酒中氨基酸的测定。     

阴离子色谱-积分脉冲安培法测定珍稀药材金线莲中游离氨基酸

定性及定量分析珍稀药材金线莲中的游离氨基酸.方法：将高效阴离子交换色谱-积分脉冲安培检测法应用于珍稀药材金线莲游离氨基酸的分析测定.结果：17种氨基酸的检出限在0.23～3.37 pmol之间,峰面积校正曲线的线性范围为2～3个数量级,5次平行测定的峰面积的相对标准偏差RSD在0.96％～4.2％之间.结论：方法适用于...