The interaction of anionic azo dyes with hen egg-white lysozyme: 1

The interactions between seven anionic azo dyes and hen egg-white lysozyme were investigated by means of visible absorption spectroscopic and lytic activity measurements. The dyes, for which no report on the interaction has appeared so far, were bound with lysozyme to different extents as a result of the differences in their chemical structures. Although most of the dyes formed 11 complex with lysozyme, two of them behaved differently. From the measurements of the absorption, lytic inhibition toward cell walls and competitive binding with substrate analogues, it was concluded that a major binding site of these dyes on lysozyme is a charged lysine residue in the vicinity of the subsitesD, E andF, and, in the case of a dye that forms 21 complex with lysozyme, and additional binding site is in the vicinity of the subsite B.     

Charge-transfer interaction of some pyridinium salts with hen egg-white lysozyme

The charge-transfer interaction of pyridinium salts with lysozyme and L-tryptophan has been investigated by visible absorption, circular dichroism and fluorescence spectroscopy. Four quaternized and substituted pyridinium salts were used as electron acceptors. L-tryptophan was used as a model compound of electron donor for the purpose of the comparison with lysozyme. The binding constants obtained from absorption and circular dichroism spectra were 2.0–13 M^–1 and the sequence of the magnitude was found as EPCl(1-ethylpyridinium chloride) < MPCl(1-methylpyridinium chloride) < MNCl(1-methylnicotinamide chloride) < MNMCl(1-methyl-3-carbomethoxypyridinium chloride), which could be explained by the electron affinity of the pyridinium salt. The fluorescence spectra of lysozyme and L-tryptophan in the absence and presence of pyridinium salts were interpreted by Stern-Volmer plot. The static constants thus determined were in agreement with the binding constants obtained by other methods.     

Synthesis,characterization and dyeing assessment of novel acid azo dyes and mordent acid azo dyes based on 2-hydroxy-4-methoxybenzophenone-5-sulfonic acid on wool and silk fabrics

Novel acid mono azo and mordent acid mono azo dyes were synthesized by the coupling of diazonium salt solution of different aromatic amines with 2-hydroxy-4-methoxybenzophenone-5-sulfonic acid. The resulting dyes were characterized by spectral techniques like elemental analysis, IR, ¹H-NMR and UV visible spectroscopy. The dyeing performance of all the dyes was evaluated on wool and silk fabrics. The dyeing of chrome pre-treated wool and silk fabrics showed better hues on mordented fabrics. Dyeing of wool and silk fabrics resulted in pinkish blue to red shades with very good depth and levelness. The dyed fabrics showed excellent to very good light, washing, perspiration, sublimation and rubbing fastness.     

镍铁类水滑石对偶氮阴离子染料的吸附脱色作用

采用镍铁类水滑石作为吸附剂,对偶氮阴离子染料酸性大红G、活性艳红X-3B和直接耐酸大红4BS废水进行脱色处理,研究了时间、镍与铁的物质的量之比、初始pH和无机电解质添加剂等因素对脱色率的影响,并结合红外光谱和X射线衍射分析结果讨论了其吸附脱色机理.结果表明,三种染料在镍铁类水滑石上的吸附均为层间的阴离子交换吸附和外表面的吸附.通过阴离子交换进入层间后,不同于直接耐酸大红4BS阴离子,酸性大红G和活性艳红X-3B两种阴离子与水滑石层间水分子之间产生氢键作用;在化学键合过程中,染料分子被镍铁类水滑石表面Fe3+氧化,同时偶氮键断裂导致脱色.     

Amidoamine calix[4]resorcinarene-based oligomers and polymers as efficient sorbents of azo dyes from water

The sorption behaviour of three kinds of macrocyclic sorbents – amidoamine tetradodecyloxyphenylencalix[4]resorcinarene 1 and tetramethyloxyphenylencalix[4]-resorcinarene 2; composition of calix[4]resorcinarene 1+2, and novel P.1 and P.2 polymers with amidoamine calix[4]resorcinarene units towards three water-soluble azo dyes – methyl orange (MO), acid orange (AO5) and Congo red (CR) was studied. All sorbents form supramolecular complexes with the aforesaid dyes. The best sorbent for MO was shown to be polymer P.1, for the AO5 – composition 1+2 and for the CR – macrocycle 2, with high sorption capacities (373, 497 and 625 mg/g, respectively). The main factor in the binding of dyes by all studied sorbents proved to be surface electrostatic interactions. In addition to the Coulomb interactions, the most important factor for the polymers appeared to be the ‘net’ structure of the polymer with a high concentration of binding sites, providing electrostatic, hydrogen, dipole–dipole and hydrophobic interaction. Hydrophobic substituents in the sorbents exert a significant influence on the dye sorption. The increase of the sorbents' hydrophobicity leads to a lower sorption capacity for MO and CR and a higher sorption capacity for AO5. It was shown that sorption efficiency of the sorbent depends on the ‘dye–sorbent’ structure conformity.     

Diffusion of nonionic azo dyes in nylon-6

Diffusion of 2,4-dinitroaniline and three nonionic azo dyes in Nylon-6 film was studied by analysis of the concentration-distance curves (profiles) of penetrants in the polymer. Actual diffusivities D_(c) of penetrants in polymer, diffusion coefficients as a function of the concentration C_f of penetrant in polymer, were calculated from the profile. It was found that D_(c) is almost constant or decreases gradually with decreasing C_f in the range of high-medium C_f but decreases appreciably with decreasing C_f at low C_f. The change in D_(c) with C_f was explained in terms of the dual-mode sorption-diffusion model. The penetrants diffuse in the polymer as two distinct species, i.e., a dissolved species and an adsorbed species. The former is the penetrant taken up by the polymer by a partition mechanism (dissolved species) and the latter is that taken up by Langmuir sorption (adsorbed species). The actual diffusivity D_P(c) of the dissolved species decreases with decreasing C_f. While the actual diffusivity D_L(c) of the adsorbed species normally increases gradually with decreasing C_f. D_P(c) is usually larger than D_L(c). © 1993 John Wiley & Sons, Inc.     

Photochromic properties of thienylpyrrole azo dyes in solution

The photochromic behaviour of thienylpyrrole azo dyes in THF solutions was studied for the first time. The photochromic properties are strongly dependent on the substitution pattern on the dyes. Nitro-substituted thienylpyrrole azo dyes are particularly interesting since they exhibit very fast colouration/decolouration processes. The activation energies of these compounds are among the lowest values reported for heterocyclic azo dyes. These compounds show aggregation phenomena in freshly prepared solutions of THF, which lead to variable photochromic behaviours. Only after 1-5 h the solutions reach equilibrium and then reproducible photochromic behaviour can be observed.     

Keggin和Dawson结构多金属氧酸盐光催化脱色偶氮染料

The investigation photocatalytic degradation of three azo dyes solution(Acid Mordant Navy Blue RRN,Acid Mordant Black PV,Acid Mordant Brown RH) under UV light irradiation using the polyoxometalates as catalyst was reported in this article.The research results showed that the photocatalytic activity of Keggin catalyst is higher than that of Dawson,and the catalyst α-H4SiW12O40 had the best efficiency to the photocatalytic decoloration of RRN.In 350 mg·L-1(30 mL) RRN solution,the optimum reaction condition wa...     

Subtilisin-catalyzed religation of proteolyzed hen egg-white lysozyme: investigation of the role of disulfides

Background: The use of proteases to form, instead of break, peptide bonds has expanded the repertoire of techniques available for protein semisynthesis. Several groups have previously reported the use of proteases in aqueous-organic solvents to form single amide bonds within proteins, but low yields and lengthy reaction times make this an impractical approach to protein synthesis. We recently found that proteolyzed triose phosphate isomerase can be re-ligated rapidly and efficiently by subtilisin, in mixed aqueous-organic solvent systems.Results: We now report the use of subtilisin to resynthesize hen egg-white lysozyme from a mixture of its proteolyzed fragments in high yield and with rapid reaction times. This enzymatic religation can also be achieved after reduction of the four disulfide bonds present in lysozyme, with the same efficiency as that observed for the disulfide-containing proteolysis mixture.Conclusions: For egg-white lysozyme, the subtilisin religation reaction can be used to re-synthesize a proteolyzed protein even after reduction of disulfide bonds. The utility of this reaction in more generalized protein semisynthesis reactions is currently being explored.     

Dual-mode sorption of nonionic azo dyes by Nylon 6

Sorption isotherms of 2,4-dinitroaniline and three 4-amino-azobenzene derivatives (nonionic dyes with adequate solubility in water) on Nylon 6 (film and fiber) from water were determined at various temperatures. The observed isotherms were curved, not linear. They were very well described in terms of the dual-mode sorption model, Nernst-type partitioning, plus Langmuir sorption. The contribution of the Langmuir sorption to the total dye sorption decreased with increasing temperature. The saturation value for the Langmuir sorption increased with the crystallinity of Nylon 6 film, suggesting that the Langmuir sorption is associated with the crystalline phase.     

Synthesis,structural characterization and molecular modelling of bidentate azo dye metal complexes: DNA interaction to antimicrobial and anticancer activities

A novel azo dye ligand, namely 1‐[(5‐mercapto‐1H‐1,2,4‐triazole‐3‐yl)diazenyl]naphthalen‐2‐ol (HL), was synthesized. Mn²⁺, Co²⁺, Ni²⁺, Cu²⁺ and UO₂²⁺ complexes were also prepared by the treatment of HL with Mn(CH₃COO)₂?4H₂O, Co(CH₃COO)₂?4H₂O, Ni(CH₃COO)₂?4H₂O, Cu(CH₃COO)₂?H₂O, CuCl₂?2H₂O, Cu(NO₃)₂?6H₂O and UO₂(NO₃)₂?6H₂O. The structures of these metal chelates were confirmed using elemental, spectral, magnetic moment, molar conductance and thermal analyses. The analytical data confirmed the formation of the chelates in 1:1 (metal‐to‐ligand) ratio having the formula [ML(H₂O)X]Y?H₂O, where M is Mn²⁺, Co²⁺, Ni²⁺, Cu²⁺ or UO₂²⁺; X is Cl^?, NO₃^? or CH₃COO^?; and Y is H₂O. The azo compound acts in a monobasic bidentate manner via the nitrogen and oxygen atoms of azo and hydroxyl groups, respectively. All complexes were found to have tetrahedral structures, except the UO₂²⁺ complex that showed octahedral geometry. The mode of interaction between the synthesized complexes and calf thymus DNA was explored by the aid of absorption spectroscopy and viscosity measurements. The azo dye and its chelates were evaluated against the growth of various bacterial and fungal strains (Escherichia coli, Staphylococcus aureus, Aspergillus flavus and Candida albicans) with insight gained into the effect of type of metal centre, type of coordinated anion and position of the metal in the periodic table on the activity of the complexes. The geometric structure of the complexes was optimized using molecular modelling. The in vitro cytotoxicity of the synthesized compounds was tested against HEPG2 cell line.     

Robust identification of binding hot spots using continuum electrostatics: application to hen egg-white lysozyme

Binding hot spots, protein regions with high binding affinity, can be identified by using X-ray crystallography or NMR spectroscopy to screen libraries of small organic molecules that tend to cluster at such hot spots. FTMap, a direct computational analogue of the experimental screening approaches, uses 16 different probe molecules for global sampling of the surface of a target protein on a dense grid and evaluates the energy of interaction using an empirical energy function that includes a continuum electrostatic term. Energy evaluation is based on the fast Fourier transform correlation approach, which allows for the sampling of billions of probe positions. The grid sampling is followed by off-grid minimization that uses a more detailed energy expression with a continuum electrostatics term. FTMap identifies the hot spots as consensus clusters formed by overlapping clusters of several probes. The hot spots are ranked on the basis of the number of probe clusters, which predicts their binding propensity. We applied FTMap to nine structures of hen egg-white lysozyme (HEWL), whose hot spots have been extensively studied by both experimental and computational methods. FTMap found the primary hot spot in site C of all nine structures, in spite of conformational differences. In addition, secondary hot spots in sites B and D that are known to be important for the binding of polysaccharide substrates were found. The predicted probe-protein interactions agree well with those seen in the complexes of HEWL with various ligands and also agree with an NMR-based study of HEWL in aqueous solutions of eight organic solvents. We argue that FTMap provides more complete information on the HEWL binding site than previous computational methods and yields fewer false-positive binding locations than the X-ray structures of HEWL from crystals soaked in organic solvents.     

Enhancement of the photochromic switching speed of bithiophene azo dyes

A series of heteroaryl substituted bithiophene azo dyes in solution were irradiated with visible light to promote the azo E-Z isomerization and then the kinetics of the thermal Z-E back reaction was studied. The speed of this process is strongly influenced by the nature of the aromatic ring linked to the NN function. While thiazole bithiophene azo dyes exhibit high switching speeds between the two isomers, but limited interconversion, for benzothiazole and substituted thiadiazole bithiophene azo dyes the switching between the two photoisomers can be performed in 3 s with a significant conversion of the trans-isomer to the thermal unstable cis-isomer (19-21%) and therefore a notable variation of the visible spectrum is observed.     

The association of inclusion complexes of cyclodextrins with azo dyes

OrangeII (4) and cyclodextrin (CD) form 2 : 1 and 2 : 2 complexes. The complexes self-associate and microscopy indicates the formation of a fibroid aggregate. In the induced c.d. spectrum, the ^* band of this complex appears at 500 nm in solution, but in the aggregate it changes to aJ-band due to the head-to-tail stacking of4 and aH-band due to its parallel stacking; this indicates that the aggregation expands not only in the direction of the symmetry axis of the CD, but also in the other two dimensions.²H-NMR spectroscopy from deuteron exchange and solvation between the aggregate and deuterium oxide exhibits quadrupole splitting in the region of 0–0.2 KHz. The orientation behavior obtained from this splitting suggests the formation of a liquid-crystaloid substance.¹³C-T ₁ NMR indicates that molecules4 and CD show the sameT ₁ values even at 333 K; this complex behaves like a single molecule. The behaviors of other azo dye-CD complexes are also discussed.DeceasedDedicated to Professor József Szejtli.     

液液萃取-分散液液微萃取-气相色谱-质谱联用测定纺织废水中痕量禁用偶氮染料

建立了液液萃取-分散液液微萃取-气相色谱-质谱联用技术测定纺织废水中痕量偶氮染料的方法。废水中的偶氮染料在碱性条件下经连二亚硫酸钠还原成芳香胺后,先用叔丁基甲醚液液萃取、盐酸反萃进行预浓缩及净化;再以乙腈-氯苯体系进行分散液液微萃取,气相色谱-质谱测定。对前处理条件进行了优化,考察了酸碱度及盐效应对芳香胺萃取效率的影响,结果表明:液液萃取过程中加入30 g NaCl,分散液液微萃取过程中加入1 mL 5 mol/L的NaOH调节体系至碱性才能达到较好的萃取效率。在优化的实验条件下,21种目标物均呈现良好的线性关系,其中13种芳香胺的线性范围为0.05～10μg/L, 7种芳香胺的线性范围为0.05～5μg/L, 2,4-二氨基苯甲醚的线性范围为20～100μg/L,相关系数为0.996～0.999。20种芳香胺的检出限可达0.05μg/L, 2,4-二氨基苯甲醚检出限为20μg/L。印染、机织、印花等实际废水加标试验表明,方法的回收率为75.6%～115.1%。该方法富集倍数高,检出限低,适用于纺织废水中痕量禁用偶氮染料的检测。     

Specific features of adsorption of azo dyes on fly ash

A possibility to utilize fly ash (FA) formed at coal-fired power plants as a cheap adsorbent for the purification of wastewater containing azo dyes methylene blue (MB) and methyl red (MR) was considered. The effect of an FA additive on the adsorption capacity of active carbon was studied. The efficiency of FA as an adsorbent for the purification of aqueous solutions from MB and MR was shown. The adsorption is also fairly efficient when active carbon is partially replaced by FA. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp. 545–548, March, 2007.     

A facile ratiometric and colorimetric azo-dye possessing chemosensor for Ni2+ and AcO− detection

A new tailor-made colorimetric chemosensor 1, containing pyridine and benzothiazole moieties connected through an azo (–N = N–) linkage has been synthesised. In 9:1 (v/v) aqueous THF (pH 7.0 HEPES buffer), it showed a conspicuous naked-eye colour change upon binding to Ni²⁺ (colourless to light green) and AcO^?  (colourless to orange) resulting in their ratiometric sensing. The cation and anion recognition property of the chemosensor 1 was monitored by UV–vis spectral analysis and ¹H NMR titrations.     

UV/H2O2/草酸铁络合物光降解偶氮蓝染料的研究

光氧化法是近年来日益受人们重视的一种治理染料废水的新方法,而现有方法光量子效率低、光能耗大、处理费用高。已有研究表明草酸铁络合物有较高的光降解效率。而在到达地面的太阳辐射中,紫外辐射只占4％左右,所以研究弱紫外辐射下光降解染料废水意义重要。本文用6W低压汞灯光源,过氧化氢．草酸铁络合物光降解水溶液中的偶氮蓝染料,考察pH值、H2O2浓度、染料浓度及光强等因素对降解结果的影响,探讨以自然光为光源催化降解偶氮蓝染料的可行性。     

Interactions of di- and trivalent anionic azo dyes with polycations of integral type

The spectral changes of Crystal Ponceau 6R and Ponceau 4R induced by the interaction with polycations having N,N-dimethyl-2-hydroxypropane-1,3-diylammonium chloride units in the main chain were followed. The stoichiometry of the polycation-dye complex related to the dye structure was elaborated by UV-VIS spectrophotometry and viscosimetric measurements. Formation of a tricomponent complex between the polycation/dye complex and poly(sodium acrylate) was also revealed.     

亚精胺对溶菌酶构象及催化性能的影响

聚乙烯亚胺是典型的聚阳离子基因载体材料,但是具有一定的细胞毒性,以小分子多胺为基础制备易降解的高分子材料是降低聚乙烯亚胺类基因载体材料的细胞毒性和提高基因转染效率的重要方法。为深入了解聚乙烯亚胺类基因载体材料与生物大分子的相互作用,本文综合应用吸收光谱、共振瑞利散射、圆二色谱和荧光光谱研究典型小分子多胺化合物亚精胺与溶菌酶的相互作用及其对酶的构象、催化活性和催化动力学的影响和机理。亚精胺是两亲性分子,其氨基基团易于质子化而具有较强的静电结合和氢键形成能力,亚甲基基团则具有一定的疏水性。亚精胺较小的分子尺寸和两亲性使其可以穿透进入溶菌酶的疏水核心,与溶菌酶肽链的非特异性结合导致溶菌酶二级结构由α-螺旋向β-折叠和β-转角转变,并导致溶菌酶表面疏水性略微增强。亚精胺与溶菌酶的结合降低了溶菌酶对底物溶壁微球菌的亲和力和最大反应速率,低浓度的亚精胺对溶菌酶的活性具有显著的抑制作用。