Novel Conformational Transitions of Human Cytochrome P450 2C8 during Thermal and Acid-induced Unfolding

Transitions among various heme coordination/spin states, heme environments and protein conformations of human cytochrome P450 2C8 were investigated under different denaturing conditions by means of electronic absorption and circular dichroism spectroscopies. It is the first report of it's kind. Our results indicated that the thermal and acid‐induced denaturation could convert P450 2C8 to various P420 forms. In the thermal unfolding process, the ferric P420 thermal form emerged with weakened Fe‐S (thiolate) bond. An absorption band at ca. 425 nm of the ferrous P420 2C8 thermal form was observed, suggesting that the axial Cys435 was protonated or displaced by other ligand. Moreover, the new coordination bond was stabilized when the temperature was cooled down. When binding with CO, the ferrous P420 2C8 thermal form had the protonated thiol of Cys435 as the axial ligand. X‐ray structure of P450 2C8 suggested that the specific structure of the β‐bulge where the axial cysteine ligand located might be the reason of the formation of these P420 2C8 thermal forms. In the acid‐induced unfolding studies, we found that at pH 3.0 the heme could be irreversibly released from the heme pocket of ferric and ferrous P450 2C8. Interestingly, the released heme could form a new coordination bond with an unidentified ligand at the surface of partially unfolded protein when binding with CO at reduced state.     

Preparation, spectral and biological investigation of formaldehyde-based ligand containing piperazine moiety and its various polymer metal complexes

A novel tetradentate salicylic acid-formaldehyde ligand containing piperazine moiety (SFP) was synthesized by condensation of salicylic acid, formaldehyde and piperazine in presence of base catalyst, which was subjected for the preparation of coordination polymers with metal ions like manganese(II), cobalt(II), copper(II), nickel(II) and zinc(II). All the synthesized polymeric compounds were characterized by elemental analysis, IR, (1)H NMR and electronic spectral studies. The thermal stability was determined by thermogravimetric analysis and thermal data revealed that all the polymer metal complexes show good thermal stability than their parent ligand. Electronic spectral data and magnetic moment values revealed that polymer metal complexes of Mn(II), Co(II) and Ni(II) show an octahedral geometry while Cu(II) and Zn(II) show distorted octahedral and tetrahedral geometry respectively. The antimicrobial screening of the ligand and coordination polymers was done by using Agar well diffusion method against various bacteria and fungi. It was evident from the data that antibacterial and antifungal activity increased on chelation and all the polymer metal complexes show excellent antimicrobial activity than their parent ligand.     

溶剂热法合成锐钛矿型二氧化钛纳米晶的形状演化规律

以钛酸四丁酯为前驱体,乙醇为溶剂,月桂酸和十二胺为共同稳定剂,采用溶剂热法制备了不同形状的锐钛矿型二氧化钛纳米晶。利用透射电子显微镜(TEM)、选区电子衍射(SAED)、X射线衍射(XRD)、傅里叶变换红外(FTIR)光谱和热失重-差热分析(TG-DTA)等技术对纳米晶的结构、尺寸、形貌及形状进行了系统的表征,并探讨了月桂酸与十二胺不同配比时纳米晶的形状演化规律。结果表明:用溶剂热法在不同配比情况下获得的二氧化钛均为锐钛矿相;在月桂酸与十二胺总摩尔量不变的情况下,随着十二胺含量的增加,二氧化钛纳米晶的形状由球形逐渐演化为棒状,且结晶化程度在两者摩尔比为1:1时最好;月桂酸与十二胺稳定剂与纳米晶内核之间以桥接配位体的形式结合,且稳定剂在样品中的含量约为5%。     

The protective effect of salicylic acid on lysozyme against riboflavin-mediated photooxidation

Tridentate Schiff base (H(2)L) ligand was synthesized via condensation of o-hydroxybenzaldehyde and 2-aminothiophenol. The metal complexes were prepared from reaction of the ligand with corresponding metal salts presence of substituted pyridine in two different solvents (MeOH or MeCN). The ligand and metal complexes were then characterized by using FTIR, TGA, (1)H NMR and (13)C NMR spectroscopies. The FTIR spectra showed that H(2)L was coordinated to the metal ions in tridentate manner with ONS donor sites of the azomethine N, deprotonated phenolic-OH and phenolic-SH. Furthermore, substituted pyridine was coordinated to the central metal atoms. The thermal behavior of the complexes was investigated by using TGA method and dissociations indicated that substituted pyridine and ligand were leaved from coordination. This coordination of the metal complexes was correlated by (1)H NMR and (13)C NMR. Finally, electrochemical behavior of the ligand and a Ni(II) complex were investigated.     

Crystallization of polypropylenewith a minute amount of β-nucleator

Triammonium-N-dithiocarboxyiminodiacetate, (NH₄)₃L, a new dithiocarbamato derivative of iminodiacetate, has been synthesized. The coordination properties of the ligand were tested in reactions with copper(II), nickel(II) and palladium(II) salts in acidic solutions. Complexes with a general formula M(H₂L)₂ were obtained, with the coordination taking place through the sulfur atoms of the dithiocarbamate moiety. The new compounds were characterized by elemental analysis, UV/VIS and IR spectroscopy, thermal analysis and magnetic measurements. In addition, the ligand was characterized by ¹H- and ¹³C-NMR spectroscopy and molar conductivity measurements. The copper(II) complex is paramagnetic, while the nickel(II) and palladium(II) compounds are diamagnetic. The thermal decomposition of all compounds is continuous and the thermal stability of the complexes is higher than that of the ligand, as expected.     

Synthesis, crystal structure, thermal and luminescence properties of CuX(2,3-dimethylpyrazine) (X=Cl, Br, I) coordination polymers

Three new coordination polymers based on CuI and 2,3-dimethylpyrazine (2,3-dmpyz) were prepared, structurally characterized and investigated for their thermal and luminescence properties. In the ligand rich 2:3 compound [(CuI)2(2,3-dmpyz)3] (CuI)2 dimers are found, which are connected by the N-donor ligands into chains, whereas in the structure of the 1:1 intermediate [(CuI)(2,3-dmpyz)] (CuI)4 tetramers are found, which are also connected into chains. The crystal structure of the ligand deficient 2:1 compound [(CuI)2(2,3-dmpyz)] is built up of CuI double chains, which are connected by the 2,3-dmpyz ligands into layers. Thermal decomposition of results in its direct transformation into the ligand deficient compound , without the formation of the 1:1 compound as an intermediate. A similar thermal reactivity is found for compound , which transforms into on heating. Stirring of a crystalline suspension of pure or in acetonitrile, always leads to a transformation into the ligand deficient compound indicating that compound is the most stable of all the coordination polymers, whereas compounds and are metastable. The luminescence properties of the CuCl and CuI coordination polymers were investigated at 298 and 77K. It was observed that the emission maxima strongly depends on the nature of the halide atom and the composition and structure of the coordination polymers. In addition, several of these compounds show luminescence thermochromism. These results are compared with those obtained for the previously reported CuCl and CuBr(2,3-dimethylpyrazine) coordination polymers.     

Acetylferrocenyl-3-hydroxyl-2-naphthoylhydrazone and its transition metal complexes

Summary Acetylferrocenyl-3-hydroxyl-2-naphthoylhydrazone and its transition metal coordination compounds were prepared. The composition and properties of the ligand and the nature of metal to ligand bonding in its coordination compounds were characterized by elemental analyses, i.r. spectra, n.m.r. spectra, u.v.-vis. spectra, thermal analyses and molar conductivities.     

Different coordination modes of 2-(diphenylphosphino)azobenzenes in complexation with hard and soft metals

Control of coordination modes of a ligand in metal complexes is significant because the coordination modes influence catalytic properties of transition metal catalysts. Reactions of 2-diphenylphosphinoazobenzenes, which are in equilibrium with the inner phosphonium salts, with ZnCl(2), W(CO)(5)(THF), and PtCl(2)(cod) gave three different coordination types of metal complexes with distinctive UV-vis absorptions. All the complexes were characterized by X-ray crystallographic analyses. In the zinc and tungsten complexes, the source molecule functions as an amide ligand and a phosphine ligand, respectively. In the platinum complex, the phosphorus molecule works as a tridentate ligand with formation of a carbon-platinum bond.     

壳寡糖锌(Ⅱ)配合物的合成与结构表征

以壳寡糖(COS)为配位体,锌(Ⅱ)离子为配位离子,在均相反应条件下合成了壳寡糖锌(Ⅱ)配合物(COS-Zn),并优化了配合物的合成条件.利用红外光谱法(FT-IR)、差热分析法(DTA)和元素分析(EA)进行结构表征,并对配位机理进行了初步探讨.     

Calculation of the equilibrium constants and cooperative parameters of formation of Cu(II) chloride complexes in nonaqueous solvents

Copper(II) distributions over chloride complexes in various organic solvents were analyzed in terms of a modified matrix model. The equilibrium coordination constants of a first ligand and the corrections for the mutual influence between the ligands during the complexation were calculated. It was demonstrated that displacement of the solvent molecule by a chloride ion from the inner coordination sphere of the Cu(II) ion is always of anticooperative character. In MeCN, addition of a chloride ion to a copper ion follows the simplest additive scheme of coordination of the ligand with equivalent coordination vacancies. Possible reasons for nonadditive complexation in DMF, DMSO, trimethyl phosphate, and propylene carbonate are discussed.     

配位聚合物{[Cu_2(nbdo)_2·(H_2O)_2]·2(H_2O)}_n的热稳定性以及荧光性能和储氢性能(英文)

合成了一种新的以柔性羧酸为配体的铜配位聚合物,考察了其热稳定性能、荧光性能及储氢能力.结果表明,配体2-硝基-苯-1,4-二(氧乙酸)表现出较好的柔韧性;该结构在温度低于541 K的环境中比较稳定,当温度高于541 K迅速发生分解并伴随着轻微的爆轰.配合物的荧光光谱与配体的相比有所蓝移.与此同时,该配合物的储氢能力随着氢气压力的增加而提高;当氢气压力为5.0 MPa时储氢能力可达0.42%.     

一维发光镉配位聚合物的合成、晶体结构及识别性能

采用芳香取代的咪唑二羧酸配体2-(对氰基)苯基-4,5-咪唑二羧酸(p-CNPhH₃IDC) ,在含氮螯合配体 2,2'-联吡啶(2,2'-bipy)的存在下,利用水热反应,制备了一个具有混合配体的一维链状配位聚合物:[Cd(p-CNPhHIDC)(2,2'-bipy)]_n(1)。 通过元素分析、傅里叶变换红外光谱仪以及单晶X射线衍射等技术手段研究了配位聚合物1的结构和性能。 结果表明,该配位聚合物稳定性较好,在231.6 ℃前结构稳定。 经乙睛、甲醇、乙醛等溶剂浸泡后,配位聚合物1的荧光强度发生了一定程度的减弱(乙醛和CH₂Cl₂)或增强(DMF、硝基苯、丙酮),仅有吡啶溶剂使其荧光发射波长发生了60 nm的蓝移,显示其对吡啶有比较好的识别作用。     

Chelation behaviour of nitroso- pyrazolones with Mn(II), Co(II), Ni(II), Cu(II) AND Zn(II)

Infrared (IR), nuclear magnetic resonance (NMR), thermogravimetric analysis (TG), derivative thermogravimetric analysis (DTG), differential thermal analysis (DTA) and molar conductivity studies have been carried out on the chelates of Mn(II), Co(II), Ni(II), Cu(II) and Zn(II) with 3-methyl- and 3-phenyl-4-nitroso-5-pyrazolones. The solid chelates were synthesized, separated, analyzed and their structures were elucidated. The data obtained show that almost all of the prepared chelates contain water molecules in their coordination sphere. The initial stage in the thermal decomposition process of these chelates shows the presence of water molecule, the second denotes to the intermediate products. The final decomposition products were found to be the respective metal oxides. The NMR spectrum of 3-methyl-4-nitroso-5-pyrazolone ligand shows the existence of the oxime rather than the nitroso form. 3-phenyl-4-nitroso-5-pyrazolone acts as a neutral bidentate ligand whereas 3-methyl-4-nitroso-5-pyrazolone acts as monobasic bidentate ligand bonded to the metal ions through the two oxygen atoms of the carbonyl and nitroso groups. The solid chelates prepared behave as non-electrolytes in DMF solution. The coordination numbers of the obtained chelates using 3-methyl-4-nitroso-5-pyrazolone are four on applying the mole ratio 1:1 and six on using 1:2 mole ratio. In case of using the ligand 3-phenyl-4-nitroso-5-pyrazolone the coordination number is six in both cases. This revised version was published online in August 2006 with corrections to the Cover Date.     

New Regional Editor

The complexes Mn(II), Co(II), Ni(II), Cu(II) and Zn(II) with 3-(anilinomethylene)-2-methoxychroman-4-one were synthesized and characterized by elemental analysis, conductivity, infrared and UV?CVis spectroscopy, ¹H NMR, X-ray diffraction patterns, magnetic susceptibility and thermal analysis (TG/DTG/DSC). The X-ray analysis shows that the studied compounds crystallize in the triclinic crystal system and they are no isostructural complexes. The unit cell parameters for these chelates were presented. The molecules of solvent are in the outside coordination sphere of the complexes. The chelates have different thermal stability and they decompose in air atmosphere in three steps. The coordination of metal ions is through nitrogen atom from ligand and oxygen atom present in 4-position of ??-pyrone. The studied chelates have electrolyte (1:1) and non-electrolyte nature. They are high-spin complexes with octahedral coordination and the weak ligand fields.     

Synthesis of a One‐dimensional Coordination Polymer Based on Copper(II) Nitrate and 1,2‐Bis(5‐monomethylhydrazinyl‐1H‐tetrazolyl)ethane

A one‐dimensional coordination polymer based on copper(II) nitrate and 1,2‐bis(5‐monomethylhydrazinyl‐1H‐tetrazolyl)ethane as ligand was prepared. The thermal and physical stability was determined by differential scanning calorimetry and BAM methods. The polymer was investigated by vibrational spectroscopy and single X‐ray diffraction. Moreover, the ligand itself and the 1,2‐bis(1H‐tetrazolyl)ethane were characterized as energetic material by bomb calorimetric measurements along with calculations using the EXPLO5 software. Both compounds have moderate energetic properties along with a high thermal and physical stability. These findings render these compounds into promising environment friendly gas generating agents.     

4-cyanoimidazolate: a new pseudo-cyanide?

Because of its exobidentate nature, pK(a), and electronic properties, 4-cyanoimidazole has been examined as a ligand and as a pseudo-cyanide. The ligand reacts readily as an anion with both cobalt and nickel ions in solution to form coordination polymers. The magnetic susceptibility and thermal stability of these materials are reported. 4-Cyanoimidazolate forms a hexakis complex with nickel, to form the first observed hexakis imidazolate nickelate complex.     

Spectral and thermal studies for some transition metal complexes of bis(benzylthiocarbohydrazone) focusing on EPR study for Cu(II) and VO2+

The coordination behavior of bis (benzylthiocarbohydrazone) as a macrocyclic ligand (H(2)BBTC), towards Co(II), Ni(II), Cu(II) nitrates, Cd(II) and Pt(IV) chlorides as well as VO(2+) sulphate has been investigated. The elemental analysis, magnetic moments, spectral (UV-vis, IR, (1)H NMR and EPR) with thermal studies were used to characterize the isolated complexes. The IR spectra showed that the ligand acts as a binegative hexadentate donor through NH groups and thiol S atoms. Electronic and magnetic data proposed the octahedral structure for all complexes under investigation, except VO(2+), is a square-pyramidal geometry. EPR spectra for VO(2+) and Cu(II) reveal data confirmed the proposed structures. The ionization constants (pK(1)=8.3 and pK(2)=7.7) of the ligand and the stability constants of its complexes in solution were determined. The TG analysis for most complexes supports the absence of solvent molecules in or out the coordination sphere through the high thermal stability observed on the thermal curves for the investigated complexes.     

Synthesis and luminescent properties of novel lanthanide(III) beta-diketone complexes with nitrogen p,p'-disubstituted aromatic ligands

Tris-beta-diketonate lanthanide(III) complexes (Ln = Eu, Er, Yb, Tb), of general formula [Ln(acac)3 L(m)], with chelating ligands such as 4,7-disubstituted-1,10-phenanthrolines and 4,4'-disubstituted-2,2'-bipyridines, have been synthesized and fully characterized. The inductive effects of the para-substituents on the aromatic N-donor ligands have been investigated both in the solid and in the solution states. Single-crystal X-ray structures have been determined for the diethyl 1,10-phenanthroline-4,7-dicarboxylate europium and 4,4'-dimethoxy-2,2'-bipyridine erbium derivatives, revealing a distorted square antiprismatic geometry around the lanthanide atom in both cases. The influence exerted by the p,p'-substituents with respect to the nitrogen coordinating atoms on the Ln-N bond distances is discussed comparing the geometrical parameters with those found for the crystal structures containing the fragments [Ln(III)(phen)] and [Ln(III)(bipy)] obtained from the Cambridge Structural Database. The influence exerted by the electron-attracting groups on the coordination ability of the ligands, that in some cases becomes lack of coordination of the lanthanide ions, has been also detected in solution where the loss of the ligand has been followed by UV-vis spectroscopy. Moreover, the use of relatively long alkoxy chains as substituents on the 1,10-phenanthroline ligand led to the formation of a promesogenic lanthanide complex, whose thermal behavior is encouraging for the synthesis of new lanthanide liquid-crystalline species.     

金属螯合亲和色谱中固定金属与蛋白质的作用

在不同PHNaCl的磷酸缓冲体系，比较了牛血清蛋白（BSA）、核糖核酸酶（RNase)、细色素C（Cyt-C)和溶菌酶（Lys)在IDA裸柱和一些金属螯合柱上的保留特性，考察了固定金属对蛋白质保留行为的影响，指出蛋白质在强结合IDA－Cu柱上的保留主要受固定金属和蛋白质间配位作用支配，在弱亲和的IDA－Ni,IDA-Co和IDA－Zn柱上的保留主要受静电作用控制，配位作用为辅，讨论了金属螯合亲和色谱中影响蛋白质和金属配位的主要因素，金属离子的电荷和半径，配位原子对中心离子外层d轨道的影响，以及蛋白质表面配位的组氨酸数目，离解常数和取向，影响金属螯合配体和蛋白质静电作用的主要因素为溶液的PH和蛋白质的等电点pI.     

A novel metal-organic network with high thermal stability: nonlinear optical and photoluminescent properties

A novel zinc(II) 4-(5H-tetrazol)benzoic coordination polymer with an in situ generated tetrazole ligand exhibits the gsi (gamma-silicon) topology and high thermal stability; this compound possesses second-order nonlinear optical and interesting heat-induced photoluminescent properties.