PREPARATION AND CELL COMPATIBILITY OF FUNCTIONALIZED BIODEGRADABLE POLY(DL-LACTIDE-co-RS-β-MALIC ACID)

In order to create a functionalized biodegradable polymer for vascular tissue engineering application,poly(DL- lactide-co-RS-β-malic acid)(PDLLMAc)was synthesized.PDLLMAc was obtained after hydrogenolysis of poly(DL- lactide-co-RS-β-benzyl malolactonate)(PDLLMA),which was from the ring-opening polymerization of DL-lactide(DLLA) and RS-β-benzyl malolactonate(MA)using stannous octoate as catalyst.The copolymers were characterized by ~1H-NMR, FTIR,GPC and DSC.The tensile strength and water uptake of the copoly...

Equilibrium of Extraction of Succinic, Malic, Maleic and Fumaric Acids with Trioctylamine

Extraction equilibrium features of succinic acid, malic acid,maleic acid and fumaric acid were investi- gated systematically withtrioctylamine (TOA) in chloroform, 4-methyl-2-pentanone (MIBK) and1-octanol. Fourier transform-infrared (FTIR) spectroscopic analysisof organic samples loaded with the acid shows that amine forms 1:1complex of ion-pair association with succinic acid, malic acid andmaleic acid, and 1:1, 2:1 complex of ion-pair association withfumaric acid. It is proposed that the complex forms depend on thesecond dissociation constant of the dibasic acid, pK_a2.

Trace determination of cobalt ion by using malic acid-malonic acid double substrate oscillating chemical system

A novel kinetic method for determination of trace amounts of cobalt ion was proposed and validated. The method is based on adding malic acid into classical Belousov-Zhabotinskii （B-Z） oscillating chemical system to form a double substrate one. The results showed that when the concentration of cobalt ion was in the range of 5.27× 10^-8 to 5.37 × 10^-12 mol L^-1, the change of the oscillating period was directly proportional to the negative logarithm of cobalt ion concentration. The sensitivity and precision of the developed method were quite satisfactory. The limit of detection was down to 5.20 × 10^-13 mol L^-1 which was a highest sensitivity found for determination of metal ions using oscillating chemical reaction so far. Some factors influencing the determination were also examined. The method has been successfully used to determine cobalt ion in vitamin B12 injection.

PbPH5,an H^(+)P-ATPase on the tonoplast,is related to malic acid accumulation in pear fruit

Organic acid content is one of the most important factors influencing fruit flavors.The predominant organic acid in most pear cultivars is malic acid,but the mechanism controlling its accumulation remains unclear.In this study,by comparing gene expression levels and organic acid contents,we found that the expression of PbPH5,which encodes a P_(3A)-ATPase,is highly correlated with malic acid accumulation in four different pear species,with correlation coefficients of 0.932**,0.656*,0.900**,and 0.518*(*,P<0.05;**,P<0.01)for Pyrus bretschneideri Rehd.,P.communis Linn.,P.pyrifolia Nakai.,and P.ussuriensis Maxim.,respectively.Moreover,the overexpression of PbPH5 in pear significantly increased the malic acid content.In contrast,silencing PbPH5 via RNA interference significantly decreased both its transcript level and the pear fruit malic acid content.A subcellular localization analysis indicated that PbPH5 is located in the tonoplast.Additionally,a phylogenetic analysis indicated that PbPH5 is a PH5 homolog gene that is clustered with the Petunia hybrida,Malus domestica,and Citrus reticulata genes.Considered together,these findings suggest that PbPH5 is a functionally conserved gene.Furthermore,the accumulation of malic acid in pear fruit is at least partly related to changes in the PbPH5 transcription levels.

A NEW CHEMICAL OSCILLATOR WITH A MACROCYCLIC COPPER（Ⅱ） COMPLEX AS THE CATALYST AND MALIC ACID AS THE SUBSTRATE

A new Belousov-Zhabotinskii oscillator in the malic acid-NaBrO3-H2SO4-[CuL](CIO4) 2 system, where L is 5. 7, 12, 14-tetraethyl-7, 14-dimethyl-1, 4, 8, 11-tetraazacyclotetradeca-4,11-diene, is reported

A convenient synthesis of methyl 2-hydroxy-4-oxo-4-(substituted phenyl) butanoates from malic acid

A synthesis of methyl 2-hydroxy-4-oxo-4-（substituted phenyl）butanoates has been accomplished using Friedel-Crafts acylation of substituted benzenes with 2-acetoxybutanoyl chloride. The key feature of this strategy is that various 4-arylbutanoates can be obtained conveniently, which are important intermediates for the synthesis of biologically active compounds including ACE inhibitors.？2009 Yong Sup Lee. Published by Elsevier B.V. on behalf of Chinese Chemical Society. All rights reserved.

Complexation of Molybdenum (Ⅵ) with R-and S-malic Acid, The Crystal Structure of (NH_4)_4[(MoO_2)_4O_3(R-mal)_2]·6H_2O

Ammonium tetramolybdate ( NH4 )4[(MoO2)4O3 (R-mal)2]·6H2O(mal= malic acid)and (NH4)4[(MoO2)4O3(S-mal)2)·6H2O have been prepared by the reaction of R and S-malic acid with ammonium heptamolybdate, respectively. The two complexes are enantiomeric and isomorphous. The complex of Risomer crystallizes in monoclinic space group C2 with unit cell parameters:a = 14. 591 (2 ), b = 10. 108(2), c=11. 464(2), β=121. 48(1)°, V=1441. 9(4),Z=2, Fω=1002. 13, Dc=2. 308, Dm=2. 3 g/cm3. F(000) = 988, MoKα radiation (λ=0. 71073 ), μ (MoKα) = 17. 7 cm-1. Final R=0. 027 for 1491 reflections with I>2. 5 σ(I). Analysis of molecular structure reveals that the complex anion contains a (Mo2O5)O(Mo2O5)core with the bridging oxo-group passing through two-fold axis. Each molybdenum is hexacoordinated , and the malate ligand is quadridentated to two molybdenum atoms by the deprotonated hydroxy-, α- and β-carboxylate groups. Principal dimensions are:[Mo=O(t)]av, 1. 705(6); [Mo-O(b)]av, 1. 920(6); Mo-O(hydroxy). 1. 925(6);Mo-O(α-carboxy), 2. 226 (6), and [Mo-O(β-carboxy)av, 2. 296 (5).Lattice water is distributed throughout the cell and together with various types of the anion oxygens, making H-bonding.

Effect of Phenolic Compounds on the Growth and L-Malic Acid Metabolism of Oenococcus oeni

The effect of some phenolic compounds recurrent in wines on technological features of Oenococcus oeni was studied in order to individuate those strains to be utilized as starter in the deacidification of aged red wines. For this purpose, the growth and the L-malic acid metabolism of 100O. oeni strains, previously isolated from different wines, was assayed in a synthetic medium added with ethanol, malic acid and phenol carboxylic （gallic, caffeic, p-coumaric and ferulic） acids or flavonoids （catechin and quercetin） at different concentrations. Results evidenced a different sensitivity of strains to each assayed compound. All the compounds restrained or stimulated the growth of 57 and 11 strains respectively, while no effect was detected on 6 strains. The remaining 26 strains showed a different behaviour： all were restrained by ferulic acid and stimulated by gallic acid and catechin. As for caffeic acid, 17 out of 26 strains were restrained, while 9 strains were stimulated. The main result obtained in this study was the establishment of a relationship between the effect of phenolic compounds on the O. oeni growth and the behaviour of the malolactic fermentation. This study may enrich the selection criteria of strains for the deacidification of aged red wines.

Preliminary Study on Lipase-catalyzed Synthesis of Polyesters Containing L-Malic Acid Units

Terpolymer of 1, 8-octanediol, adipic acid, and L-malic acid was synthesized via a lipase-catalyzed direct polycondensation. The products were characterized by GPC and 1H NMR. The results indicated that the molecular weight of the prepared polymers decreased with increasing L-malic acid content in the monomer feed ratio, and that change in the L-malic acid content from 0 to 20 mol % did not remarkably influenced on the molecular weight distribution Mw /Ma of the prepared samples. The 1H NMR spectra of the obtained copolymer samples showed that hydroxyl groups of L-malic acid did not take part in the polymerization reaction.

Highly selective/enantioselective Pt-ReOx/C catalyst for hydrogenation of L-malic acid at mild conditions

The catalyst preparation strategy was based on a strict introduction sequence of rhenium and platinum precursors and their strong interaction with carbon support resulted in the formation of 0.5 nm Pt-Re Ox species of atomic dispersion, where platinum is metallic, while monolayer rhenium is partially oxidized（Re2＋）. The reaction kinetics was studied taking into account the process of L-malic acid association leading to the formation of inactive cyclic oligomeric species. High TOFs（ca. 50 h-1）, selectivities（ca. 99%）and stability of Pt-Re Ox/C catalysts in aqueous-phase hydrogenation of L-malic acid, which are close to those of the homogeneous pincer type complexes, were revealed at mild conditions（T = 90–130 ℃）. Taking into account that（i） hydrogenation reaction occurred 2–3 orders of magnitude faster than its racemization and（ii） association of L-malic acid dominates at low temperatures and in a concentrated solution,special reaction conditions that allow obtaining chemically and optically（ee 〉 99%） pure（S）-3-hydroxy-γ-butyrolactone and（S）-1,2,4-butanetriol were found. Basing on HAADF-STEM, EDX, XPS, and kinetic studies, the structure of active species and basic reaction pathways are proposed.

DL-苹果酸-丙酮-BrO_3^--Mn^(2+)-H_2SO_4化学振荡反应诱导期的新特征及其动力学研究

在前文研究工作的基础上,较详细地研究了DL-苹果酸(以下简称DL-MA)、丙酮(以下简称Act)参与下的新型化学振荡反应及各种影响因素,对各主要参与反应物质在诱导期中的作用、起振原因、诱导期的新特征和可能反应机理进行了较为深入的研究,分别获得DL-MA,KBrO_3,MnSO_4的浓度对诱导期影响的拟合方程t_(IN)(C_(DL-MA))=-0.051+0.096/(C_(DL-MA)-0.181)(有Act存在时)t_(IN)(C_(DL-MA))=-0.24+0.224/(C_(DL-MA)-0.0485)(无Act存在时)t_(IN)(C_(KBrO_3))=73.429C_(KBrO_3)+1.275t_(IN)(C_(MnSO_4))=99.5c_(MnSO_4)+4.2(式中t_(IN)表示诱导期,C_(DL-MA),C_(KBrO_3),C_(MnSO_4)分别表示DL-MA,KBrO_3,MnSO_4的浓度)以及诱导期的表观活化参数为E_(IN)=68.50kJ·mol^(-1).

稀土、钙的DL-苹果酸和L-羟脯氨酸混配配合物研究

在模拟生理条件下（３７℃，０１５ｍｏｌ·Ｌ－１ＮａＣｌ），用ｐＨ电位法测定了１４种稀土、钙的ＤＬ苹果酸和Ｌ羟脯氨酸二元、三元配合物的稳定常数，用计算机优化确定了二元体系，苹果酸配合物存在１１０１、１１００和１２００型，羟脯氨酸配合物存在１０１０型混配配合物，苹果酸配合物的稳定常数大于羟脯氨酸。三元体系中仅生成１１１２型混配配合物。各体系中稀土配合物稳定常数均大于钙的。讨论了各物种随ｐＨ的转化过程，探讨了生物体内稀土与钙可能发生的竞争、取代作用及特点。

离子色谱法同时测定环保型电镀抛光液中氨基磺酸和DL-苹果酸

采用Metrosep A Supp5150阴离子分离柱,以3.2mmol/L Na2CO3-1.0mmol/L NaHCO3为淋洗液,氨基磺酸和DL-苹果酸可得到很好的分离,使用离子色谱为检测手段可实现环保型电镀抛光液中氨基磺酸和DL-苹果酸的同时测定。两者的线性范围分别为1.6～175mg/L和3.2～175mg/L;检出限分别为0.4mg/L和0.8mg/L;相对标准偏差分别小于1.1%和0.9%(n=9);氨基磺酸的加标回收率在97%～103%之间,DL-苹果酸的加标回收率在93%～105%之间。方法用于新型电镀抛光液中氨基磺酸和DL-苹果酸的同时测定,具有很好的实用性。对实现抛光液中氨基磺酸和DL-苹果酸的在线监测具有实际意义。

DL-苹果酸对白云母可浮性的抑制机理

在油酸钠体系下研究了DL-苹果酸对白云母可浮性的影响,采用FTIR和XPS等方法研究了DL-苹果酸与白云母的作用机理。结果表明,DL-苹果酸可显著抑制白云母的可浮性,DL-苹果酸在溶液中生成的C_4H_5O_5^-、C_4H_4O_5^(2-) 等离子与矿浆中的油酸根等离子发生竞争吸附,并且C_4H_5O_5^-、C_4H_4O_5^(2-) 等离子吸附在白云母表面会导致白云母表面的ζ电位负向增大,进而会削弱油酸根等离子在白云母表面的静电吸附作用。此外,含有羟基等强烈亲水基团的C_4H_5O_5^-、C_4H_4O_5^(2-) 等离子吸附在白云母表面会使白云母表面亲水,因此白云母的可浮性受到抑制。

顺序注射化学发光联用技术测定DL-苹果酸的初步研究

基于硫酸介质中高锰酸钾直接氧化DL-苹果酸产生化学发光的原理，结合顺序注射进样技术，初步建立了测定DL-苹果酸的自动化方法．对进样顺序、体积、流速和浓度各因素进行了优化，在156μL进样体积下，方法的线性范围为1．0×10^-4～1．0×10^-2mol／L，检出限为（3σ）为5．0×10^-5mol／L，方法的相对标准偏差为1．3％（5．0×10^-3mol／L，n=11）．采样频率为84个／h．

检测DL-苹果酸的高锰酸钾化学发光体系

利用高锰酸钾化学发光体系测定了DL-苹果酸 ,测得该物质的浓度与其对应的化学发光峰值在一定范围内存在较好的线性关系。测定DL-苹果酸的线性范围在1.0×10-6～1.0×10-2mol·L-1;相对标准偏差为1.4%(n=8) ,检出限为1.0×10-9mol·L-1。测定实际苹果汁与饮料 ,结果良好。实验表明 ,该法线性范围宽、重现性好、操作简便。文中还探讨了该体系的自催化属性。

药典级DL-苹果酸的合成及精制工艺

采用正交设计试验研究了药典级 DL-苹果酸的合成工艺。考察了反应物配料浓度、反应时间、反应温度等因素对转化率及选择性的影响。优化了合成工艺及精制方法 。

Structural Basis for the Interaction of 14-3-3<i>β</i>with Tricarboxylic Acid Cycle Intermediate Malate

The protein family of 14-3-3(s) has risen to a position of higher importance as an adaptor protein in cell biology. The seven highly conserved human 14-3-3 proteins coordinate diverse cellular processes including apoptosis, DNA damage response, protein trafficking, and others. In liver hepatocytes, 14-3-3β binds to Ser196-phosphorilated glucose-responsive carbohydrate response element-binding protein (ChREBP) to inhibit converting excess carbohydrate to fat by regulating the nuclear/cytosol trafficking of ChREBP. Here, we report X-ray crystal structures of homodimeric mammalian 14-3-3β in its apo, Malate-bound forms. The determined apo structure was captured with one monomer in the closed state, whereas the other one had an open conformation. Strikingly, 14-3-3β binds Malate dynamically with a double-closed state, which is distinct from all previously characterized 14-3-3(s) and target ligand-binding modes. Malate docks into a first-time observed cofactor pocket located at the concaved interface of 14-3-3β helices α2, α3, α4 through mainly electrostatic and hydrogen interactions. Such a Tricarboxylic Acid Cycle intermediate Malate bond model might offer a new approach to further analyze insulin-independent 14-3-3/ChREBP pathway of de novo fat synthesis in the liver.

低分子量有机酸(苹果酸)对方解石-氟的吸附/沉淀反应影响

低分子量有机酸常对矿物的表面反应(吸附/沉淀)产生影响,从而影响矿物的溶解、矿化等过程,进而影响环境地球化学进程中元素的迁移稳定性。苹果酸作为一种广泛存在于自然界中的有机酸,是植物通过代谢过程分泌的副产品。通过批量平衡法开展了苹果酸对方解石-氟的吸附/沉淀反应的影响研究,旨在深入理解有机酸在地球化学过程中的作用。结果表明:①初始pH值为7.7条件下,对于低浓度氟(≤5 mg·L^(-1)),随着苹果酸浓度的升高,其对氟去除的抑制作用呈增强趋势;对于中、高浓度氟(25或60 mg·L^(-1)),氟去除主导机制为CaF 2沉淀反应,苹果酸的抑制作用对其影响不大,但其表面吸附反应导致pH值升高和钙浓度下降。②初始pH值为8.3条件下,对于低浓度氟(≤20 mg·L^(-1)),苹果酸对氟去除仍有抑制作用;苹果酸与Ca 2+的络合反应促使pH值和钙浓度上升;对于中浓度氟(60 mg·L^(-1)),氟去除主导机制为CaF 2沉淀反应,20 mg·L^(-1)苹果酸已对其产生抑制作用,随着苹果酸浓度继续升高,pH值先降后升,钙浓度持续上升,彰显了苹果酸络合反应的效应;对于高浓度氟(100 mg·L^(-1)),100 mg·L^(-1)苹果酸能极大抑制CaF 2沉淀反应,对应的pH值未超过无苹果酸时,对应的钙浓度仍低于其空白背景值,暗示了CaF 2沉淀反应的主导性。③初始pH值为8.7条件下,对于低浓度氟(≤5 mg·L^(-1)),苹果酸对氟去除的抑制作用有所减弱,但其络合反应产生的效应十分显著,导致pH值和钙浓度上升;对于高浓度氟(240 mg·L^(-1)),氟去除主导机制为CaF 2沉淀反应,该反应随着苹果酸浓度的升高而受到抑制,对应的钙浓度不断上升彰显苹果酸络合反应的效应,而pH值的下降也表明了CaF 2沉淀反应的主导性。本研究深入探讨了氟元素在方解石矿物界面上的吸附、迁移和转化过程,为理解氟的迁移稳定性提供了新的视角和理论基础,同时对富含有机酸环境中方解石矿物的稳定性评估具有重要意义,也为氟在其他矿物上的迁移转化研究提供借鉴。

外源有机酸对复垦土壤中重金属Cr的活化效果研究

为了探究低分子有机酸(柠檬酸和苹果酸)对Cr污染土壤中Cr形态分布的影响,以淮南市潘一矿煤矸石山周边的复垦土壤为研究对象,通过模拟不同浓度Cr污染土壤,分析柠檬酸(CA)和苹果酸(MA)对土壤中Cr赋存形态的影响机制。结果表明:(1)随着外源Cr浓度的增加,土壤中Cr的活性有效提高。(2)柠檬酸和苹果酸的加入均可增加土壤中可交换态Cr的占比,即Cr的有效性得到提高,且随着柠檬酸和苹果酸浓度的升高,对土壤中Cr活化效果持续上升,柠檬酸的活化效果优于苹果酸。(3)随着老化时间的延长,有机酸对Cr的活化效果会减弱,弱结合态Cr将逐渐向强结合态Cr转化。因此,土壤重金属Cr污染修复中,可以考虑选用活化效果较好的柠檬酸作为修复辅助剂,来提升土壤Cr修复效率。研究结果可为矿区复垦土壤重金属Cr污染修复提供指导。