DyP-Type Peroxidases: Recent Advances and Perspectives

In this review, we chart the major milestones in the research progress on the DyP-type peroxidase family over the past decade. Though mainly distributed among bacteria and fungi, this family actually exhibits more widespread diversity. Advanced tertiary structural analyses have revealed common and different features among members of this family. Notably, the catalytic cycle for the peroxidase activity of DyP-type peroxidases appears to be different from that of other ubiquitous heme peroxidases. DyP-type peroxidases have also been reported to possess activities in addition to peroxidase function, including hydrolase or oxidase activity. They also show various cellular distributions, functioning not only inside cells but also outside of cells. Some are also cargo proteins of encapsulin. Unique, noteworthy functions include a key role in life-cycle switching in Streptomyces and the operation of an iron transport system in Staphylococcus aureus, Bacillus subtilis and Escherichia coli. We also present several probable physiological roles of DyP-type peroxidases that reflect the widespread distribution and function of these enzymes. Lignin degradation is the most common function attributed to DyP-type peroxidases, but their activity is not high compared with that of standard lignin-degrading enzymes. From an environmental standpoint, degradation of natural antifungal anthraquinone compounds is a specific focus of DyP-type peroxidase research. Considered in its totality, the DyP-type peroxidase family offers a rich source of diverse and attractive materials for research scientists.     

Photofading of anthraquinone disperse dyes in epoxy resin films: Photoreduction,energy transfer and photostabilisation processes

The photofading of three anthraquinone disperse dyes, 1- and 2-piperidino- and 1-hydroxy-4-(p-toluidino)-anthraquinone has been examined in a number of epoxy resin systems using UV-visible absorption spectroscopy. Compared with a relatively inactive polymer system such as cellulose triacetate the epoxy resins accelerate photofading through a reduction mechanism, which is, in turn, dependent on the structure of the dye and functionality of the hardener. A number of stabiliser systems are examined on the fading rate of one of the dyes and one of them, an N-oxy radical, is highly effective in inhibiting photoreduction. A regenerative mechanism involving the hydroxylamine is discussed. Evidence for a triplet-to-singlet energy transfer process from the polymer to the 2-piperidino derivative is also presented.     

Azo and anthraquinone dye decolorization in relation to its molecular structure using soluble Trichosanthes dioica peroxidase supplemented with redox mediator

In this study we investigated the decolorizing ability of Trichosanthes dioica-derived soluble peroxidase on structurally complex azo and anthraquinone dyes in the presence of redox mediators. Our results show that riboflavin acted as a better redox mediator than antraquinone-2, 6-disulfonate (AQDS). Riboflavin served as an efficient electron transferor than AQDS in the reduction of azo dyes, by contrast with anthraquinone dyes. Although the extent of decolorization (expressed as percent dye decolorization) varied from one dye to the other, maximum decolorization was achieved for the case when suspensions containing 0.45 EU (Enzyme Units)/ml and 0.2 mM riboflavin at pH 5.0 were incubated for 2 h at 40 °C.     

Measurement and correlation of solubility of disperse anthraquinone and azo dyes in supercritical carbon dioxide

The solubility of three disperse anthraquinone dyes and two azo dyes in supercritical CO₂ was measured. The tested dyes are Celliton fast blue B, l-amino-2-methylanthraquinone, 1-methylaminoanthraquinone, disperse Red 1 and 4-[4-(phynylazo)phenylazo]-o-cresol. Solubility measurements were made at 313.15-393.15 K and 10-25 MPa in a high-temperature autoclave phase equilibrium apparatus. Pure physical properties of the dyes such as critical constants, molar volumes and vapor pressures were estimated based on semi-empirical methods. Also, the data were quantitatively modeled by both an empirical density correlation and a quantitative equation of state recently proposed by the present authors based on nonrandom lattice theory. We found that anthraquinone disperse dyes in general show higher solubility than azo disperse dyes in supercritical CO₂ within the experimental ranges.     

Novel Hybrid Polymer Composites Based on Anthraquinone and Eco-Friendly Dyes with Potential for Use in Intelligent Packaging Materials

This study aimed to present the influence of bio-based and anthraquinone dyes and their combinations on the optical properties of ethylene-propylene (EPM) composites after thermo-oxidative and climatic aging. Therefore, the chosen polymer was filled with a natural, plant-origin flavonoid—quercetin, and with two commercial anthraquinone dyes (C.I. Solvent Yellow 163 and C.I. Solvent Red 207). The manufactured polymer composites were subjected to accelerated aging tests: weathering and thermo-oxidation, respectively. Examination of the materials’ properties indicated that the combination of synthetic and natural dyes can result in better resistance to oxidizing agents and higher thermal stability of ethylene-propylene products. Moreover, color change of quercetin-containing samples due to exposure to simulated atmospheric conditions could be a promising solution for use as aging indicators in intelligent packaging materials that will inform about the ongoing degradation process. Another interesting finding is that these samples exhibited good fungistatic activity against Candida albicans yeast and Aspergillus niger mold. Overall, this novel solution based on hybrid polymer composites containing natural and commercial dyes is a more environmentally friendly alternative to traditional materials used in the plastic packaging industry with better and more desirable properties.     

含羧甲磺酰基水溶性分散染料的研究

本文提出一类含有羧甲磺酰基（—SO_2CH_2COOH）的新的水溶性分散染料。利用应用时的高温,它转变为不溶性的分散染料。因此,在成品加工时不必进行砂磨,不需要扩散剂。它在弱酸、中性和碱性中都可使用,并适用于纯涤纶和涤/棉织物的印花和轧染。     

Photostability of Anthraquinone and Azo Dyes in N-Ethylacetamide (Nylon Model)

Measurements of the quantum yields of photodegradation of anthraquinone and azo dyes in N-ethylacetamide (nylon model) and triplet sensitisation of dye fading showed that the photochemical reactions are initiated by an upper excited n-π* triplet state. The primary photochemical reaction with both anthraquinone and azo dyes involves hydrogen abstraction from the amide so/vent. In some cases oxygen retards dye fading by reoxidation of the reduced structures. In other cases oxygen accelerates the photochemical reaction via free-radical initiated oxidation reactions. The quantum yields of dye fading are strongly wavelength dependent. On exposure to a simulated sunlight spectrum photodegradation is mostly caused by radiation in the region 300–400 nm. While unsubstituted anthraquinone is very photoreactive, amino-substituted anthraquinones are much more photostable in N-ethylacetam/de. Photostability of mono- and di-substituted anthraquinone derivatives increases with the electron-donating power of substituent groups. Azo dyes with increased conjugation such as diazo and naphthazo structures are more photostable than simple azobenzene derivatives. Certain electron-withdrawing substituents, which do not affect dye colour, improve the ‘oxidative’ photostability of both anthraquinone and azo dyes. A cobalt premetallised azo dye (C.I. Acid Red 182) is very photostable in N-ethylacetamide, showing the effect of metal chelates on photostability. The low values of quantum yields for the dye solutions are comparable with those of acid and disperse dyes in nylon films, indicating that N-ethylacetamide is a suitable nylon model for mechanistic studies of dye fading.     

Photocatalytic Discoloration of Dyes: Relation between Effect of Operating Parameters and Dye Structure

The process of TiO₂/UV photocatalytic discoloration of wastewaters containing organic dyes is influenced by a number of variables. In this paper, the effects of some of these parameters, i.e., mass of catalyst, initial dye concentration, and pH, were related to the structural nature of the dyes investigated, azo and anthraquinone dyes, two families that are representative of about 75 % of the dyes marketed nowadays. Both bibliographical and own experimental data were used to analyze and discuss the photocatalytic discoloration in terms of dye structure and degradation pathways. It is shown that azo dyes (Methyl Orange, Metanil Yellow, Acid Orange 7, and Reactive Red 120) are more easily discolored than Reactive Blue 19 (anthraquinone dye), due to the higher molecular stability of the latter. It is also shown that azo dye discoloration is more influenced by the initial dye concentration, whereas recalcitrant anthraquinone dyes (Reactive Blue 19) mainly demand for basic pH values to generate enough OH^• radicals. Concerning TiO₂ loading, both the bibliographical and current research data showed no effect of this variable in the experimental range analyzed.     

Publication Sponsored by ETAD The Adsorption of Dyes on Activated Sludge

Effluents from textile dyeing and printing processes usually contain dissolved or suspended dyes in small quantities. One of the treatments which may be applied to such effluent is passage through a biological treatment plant in which colour removal proceeds via adsorption on activated sludge. An indication was sought as to the likely efficacy of such a plant in dealing with intermittent influxes of dyes at concentrations similar to those to be expected in practice. A simple test method is described which enables the tendency of a dye to be removed by adsorption on activated sludge to be categorized. Application of the test to six classes of dyes by some of the member firms of ETAD has indicated that the adsorption depends on the class of dye and to structural differences within the classes.     

Click‐coupling of anthraquinone dyes with β‐cyclodextrin: formation of polymeric superstructures

Two novel cyclodextrin‐modified anthraquinone dyes were synthesized and investigated for their complexation behaviour and formation of superstructures. Therefore, 1‐fluoro‐4‐N‐(propargylamino)anthraquinone and 1,4‐bis(propargyloxy)anthraquinone were prepared via nucleophilic aromatic displacement and subsequently covalently ‘click‐coupled’ in a copper(I)‐catalysed azide–alkyne cycloaddition with β‐cyclodextrin monoazide. Both the propargyl‐modified precursor and the click‐coupled anthraquinone dyes were evaluated as hosts and guests, respectively, in β‐cyclodextrin interactions. The anthraquinone dye bearing two cyclodextrins, 1,4‐bis((1‐β‐cyclodextrin‐1H‐1,2,3‐triazol‐5‐yl)methoxy)anthraquinone, enables the reversible formation of supramolecular crosslinked poly[(N,N‐dimethyl acrylamide)‐co‐(N‐(ferrocenoylmethyl)acrylamide)] ( 11 ), whereas the monofunctionalized compound 1‐fluoro‐4‐(((1‐β‐cyclodextrin‐1H‐1,2,3‐triazol‐5‐yl)methyl)amino)anthraquinone can be supramolecularly linked to 11 resulting in coloured polymers. These features of β‐cyclodextrin‐linked anthraquinone dyes can be verified with either ¹H ¹H NMR rotating frame nuclear Overhauser effect spectroscopy or the naked eye. © 2016 Society of Chemical Industry     

Synthesis of polycondensable anthraquinone dyes and coloured nylon fibres: III

A series of 1,5-diaryl- and 1,8-diaryl-substituted anthraquinone dyes, which contain −COOH or −NH₂ groups, were prepared. The aryl-substituted anthraquinone dyes possess excellent thermostability and will keep their original colour in polycondensation with caprolactam at 260–280°C. With different aryl substituents the anthraquinone dyes exhibit different colours and can be used to prepare a series of coloured nylon-6 fibres. ©1997 SCI     

偶氮染料的光敏性研究

合成了单偶氮蒽醌、双偶氮蒽醌和双偶氮芴酮三个系列偶氮染料,并以此制成了功能分离型双层光电导体。蒽醌类单偶氮染料扩大取代基的共轭体系,可以提高光敏值,最大可由Ix.S2800提高到Ix.S62,含-NO_2的染料光敏性最高,最低为-OCH_3。蒽醌双偶氮类染料取代基对光敏性的影响与蒽醌单偶氮类染料相同,前者的光敏性高于取代基相同的后者。取代基对芴类双偶氮染料光敏性的影响与前两类不同,含-Cl取代时光敏性最高,含-NO_2最低。染料的光敏性排序为:芴酮类>双偶氮蒽醌类>单偶氮蒽醌类。     

Variations in diffusion coefficient of disperse dyes in single PET fibres: monitored and interpreted by confocal laser scanning microscopy

A novel method is proposed for determining the diffusion coefficient (D) of disperse dyes in PET fibres. Concentration-distance profiles are recorded on optical sections of single fibres by confocal laser scanning microscopy. This allows for an accurate value of the true diffusion coefficient in the fibres as well as for a founded insight in the dye diffusion process and its interrelation with the glass transition, which is not possible by the commonly used methods. At 130 °C, the common industrial dyeing temperature, the diffusion coefficient showed to be constant for the dyes tested, with D being about five times larger for the anthraquinone dye than for the benzodifuranone dye. At 100-110 °C, near to the start of the glass transition region of the fibres, D could no longer be regarded as a constant for the anthraquinone dye but was concentration dependent. This was explained by the plasticising effect of the anthraquinone dye.     

Direct Observation of Triplet Reactions of Anthraquinone Vat Dyes Using Nanosecond Laser Photolysis

The triplet-triplet spectra of three commercial anthraquinone vat dyes (C.I. 67300, C.I. 59100 and C.I. 60515) were studied in solution at room temperature using laser photolysis. The triplet states of these dyes react with oxygen, and the rate constants for the quenching process were measured, together with the rates of energy transfer from the triplet state to anthracene. These observations are considered in relation to the photoreactivity of these dyes.     

Catalytic potential of cauliflower (Brassica oleracea) bud peroxidase in decolorization of synthetic recalcitrant dyes using redox mediator

We investigated the effect of cauliflower (Brassica oleracea) bud peroxidase along with redox mediators on decolorization of dyes (Reactive Red 2, Reactive Black 5, Reactive Blue 4, Disperse Orange 25 and Disperse Black 9). Results indicated that among the chosen mediators, 1-hydroxybenzotriazole (HOBT) followed by riboflavin were most effective for dye decolorization. At 0.36 EU/ml and with 0.8 mM HOBT in conjunction with 0.75 mM H₂O₂ the soluble cauliflower bud peroxidase proteins could decolorize the dyes. The enzyme worked in a broader range of pH and temperature and was adequately effective in batch processes when used with organic contaminants (dioxane and dimethylformide), detergents (Triton X-100 and sodium dodecyl sulfate), sodium chloride and heavy metals including zinc and cadmium chloride. Thus peroxidase from cauliflower bud is a better choice than other vegetable peroxidases as it is sufficiently thermostable, operates in a wide range of pH, economic and effective with low concentration of redox mediators in decolorizing recalcitrant synthetic dyes. Such peroxidases with better catalytic activity have potential of being used on a large scale.     

A Glutathione Peroxidase Gene from Litopenaeus vannamei Is Involved in Oxidative Stress Responses and Pathogen Infection Resistance

In shrimp, several glutathione peroxidase (GPX) genes have been cloned and functionally studied. Increasing evidence suggests the genes’ involvement in white spot syndrome virus (WSSV)- or Vibrio alginolyticus-infection resistance. In the present study, a novel GXP gene (LvGPX3) was cloned in Litopenaeus vannamei. Promoter of LvGPX3 was activated by NF-E2-related factor 2. Further study showed that LvGPX3 expression was evidently accelerated by oxidative stress or WSSV or V. alginolyticus infection. Consistently, downregulated expression of LvGPX3 increased the cumulative mortality of WSSV- or V. alginolyticus-infected shrimp. Similar results occurred in shrimp suffering from oxidative stress. Moreover, LvGPX3 was important for enhancing Antimicrobial peptide (AMP) gene expression in S2 cells with lipopolysaccharide treatment. Further, knockdown of LvGPX3 expression significantly suppressed expression of AMPs, such as Penaeidins 2a, Penaeidins 3a and anti-lipopolysaccharide factor 1 in shrimp. AMPs have been proven to be engaged in shrimp WSSV- or V. alginolyticus-infection resistance; it was inferred that LvGPX3 might enhance shrimp immune response under immune challenges, such as increasing expression of AMPs. The regulation mechanism remains to be further studied.     

Dye diffusion studies in PET fibres by confocal laser scanning microscopy and the interrelation with the glass transition

Confocal laser scanning microscopy (CLSM) is used to monitor the dye penetration in poly(ethylene terephthalate) fibres during a common commercial dyeing process. The study of optical sections of fibres dyed for prolonged times in the dyeing process allows for a qualitative interpretation of the dye diffusion process, which is not possible by other techniques. A major dissimilarity was revealed between the diffusional behaviours of the two dye classes studied. The anthraquinone dyes showed a much lower temperature onset of dye penetration during the dyeing process than the benzodifuranone dyes (approximately 110 °C vs. 130 °C). Modulated differential scanning calorimetry was used to permit an understanding for this lower temperature onset and thus for the distinction in the driving forces of the dyeing mechanism between both dye classes. These driving forces were further shown to be similar for both the conventional textile fibres and the microfibres studied.     

Substituted benzylidene Cyanines

Eight new chain substituted benzylidene cyanine dyes have been prepared by condensing 4-dimethylamino-2′-nitrobenzophenone and 4-dimethylamino-3′,5′-dinitrobenzophenone H90 H90 V 3 with methiodides of quinaldine and 6-haloquinaldines, in H90 H90 V 3 absolute ethanol, using piperidine as a basic catalyst. The optical absorption and H90 H90 V 3 extra sensitisation data of the dyes have been recorded and compared with those H90 H90 V 3 of their methin analogues. H90 H90 V 3The dyes absorb at longer wavelengths than their unsubstituted analogues, contrary to earlier observations. The dyes obtained from the 2′-nitroketone are H90 H90 V 3 good sensitisers, whereas those obtained from the 3′,5′-dinitroketone, are densensitisers. H90 H90 V 3