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In this study, the Henry's law methodology is applied to predict the release of odorants present in single and multicomponent fragrance mixtures diluted in mineral oil, a simplified matrix used in cosmetic products. To attain this goal, the experimental Henry's law constant (H) of each odorant in each studied fragrance system (containing one, two, three, or four odorants) was first evaluated by plotting their liquid phase and experimental vapor phase concentrations assessed by headspace gas chromatography. From that point, the H value of each odorant in the multicomponent fragrance system was predicted from its corresponding Hexp in the single fragrance component system. The theoretical vapor-phase concentrations were also calculated using the activity coefficients for vapor-liquid equilibria by applying the thermodynamic UNIFAC model. The odor intensity and character of the studied fragrance systems were assessed through the Stevens's power law and Strongest Component models (psychophysical models). This study confirmed that the headspace concentrations and odor intensity of each odorant present in a multicomponent fragrance mixture dissolved in mineral oil can be efficiently predicted from its corresponding H determined when present alone in the simplified matrix, for low concentrations. Also, comparing both methodologies, UNIFAC and Henry's law, it was concluded that Henry's law is a better predictive model for the vapor-liquid equilibria, showing lower deviations from the experimental data. Therefore, the proposed predictive mathematical model can be attractive for the assessment of sensory quality of multicomponent fragrance systems in early formulation stages. [ABSTRACT FROM AUTHOR]

Productdesign and engineering is one of the novel paradigms ofthe 21st century, aiming for the development of novel added-valueproducts for consumers. Its application to the fragrance businessfor the purpose of enhancing the design and performance of perfumedproducts is of prime interest because nowadays three-fourths of consumergoods contain fragrances in their composition. Furthermore, fragrancedesign and classification is still performed on a trial-and-errorbasis which consequently increases products’ time to marketand consumption of raw materials. The Perfumery Radar methodologywas developed in the recent past as a tool for fragrance design andclassification with predictive capabilities. In this study, we extendit to the Perfumery Radar 2.0, which uses typical olfactory familiesused by the industry but also introduces outer and inner layers fora detailed description of the odor space of fine fragrances. Furthermore,we fully validated this methodology with sensorial classificationsof perfumers using several formulated fragrances with known compositionsand physicochemical properties with very good predictive accuracy.Finally, and for the first time, we applied the Perfumery Radar 2.0to 36 commercial fragrances differing in gender (feminine, masculine,and unisex) and covering the odor space. Correlations between olfactoryfamilies or odor descriptors with gender trends as well as with richerolfactory families such as chypre and fougère were also derived. [ABSTRACT FROM AUTHOR]

In this work a previous model developed to account forthe odorintensity of liquid perfumes was validated using sensory evaluationsperformed by two different panels, one of professional perfumers andanother of nontrained individuals (consumers). For that purpose, severalfragrance mixtures containing three perfumery raw materials (havingdifferent physicochemical properties) and a solvent were formulatedattending to the expertise of experienced perfumers. These mixtureswere then placed on textiles, allowed to evaporate, and then weresubjected to experimental olfactory evaluations, being their perceivedintensity rated by perfumers and nontrained panelists. The perceivedodor intensity of these samples was also predicted using our modelthat considers fragrance release and intensity perception. The resultsobtained show a good correlation with the ratings from both perfumersand nontrained panelists. In this way, it was shown that odor intensitycan be predicted using a structured model which accounts for the evaporationand olfactory perception of fragrances. [ABSTRACT FROM AUTHOR]

Several predictive GEmethods based on the group-contribution concept have been tested for prediction of multicomponent vapor–liquid equilibria (VLE) of fragrance mixtures. The evaluation covered 24 binary, 20 ternary, and 21 quaternary mixtures combining six different fragrances typically used in perfume formulation and ethanol as the solvent. The selected predictive methods are the original UNIFAC (updated to the last revision), the UNIFAC-Dortmund, the ASOG, and the A-UNIFAC. The equilibrium compositions were experimentally measured at 23 °C by headspace gas chromatography (HS-GC). For each liquid composition, the corresponding experimental and predicted vapor compositions were compared. This study confirmed that the UNIFAC method is the best predictive model for prediction of VLE, while the A-UNIFAC performed poorer than other evaluated methods for the mixtures studied in this work. Moreover, from the vapor composition the odor intensity and character of the fragrance mixtures was calculated using a previous developed model which considers the Stevens’ power law for the olfaction intensity scale and the stronger component model for quality perception. In this way, the odor intensity and character of fragrance mixtures was predicted and compared to experimental and sensorial evaluations. From this work it can be concluded that the UNIFAC and UNIFAC-Dortmund methods allow obtaining optimal predictions of the character of the fragrance mixtures with an agreement of 95.4% when compared to experimental measurements. [ABSTRACT FROM AUTHOR]

Three membrane-bound redox complexes have been reported in Desulfovibrio spp., whose genes are not found in the genomes of other sulfate reducers such as Desulfotalea psycrophila and Archaeoglobus fulgidus. These complexes contain a periplasmic cytochrome c subunit of the cytochrome c3 family, and their presence in these organisms probably correlates with the presence of a pool of periplasmic cytochromes c3, also absent in the two other sulfate reducers. In this work we report the isolation and characterization of the first of such complexes, Tmc from D. vulgaris Hildenborough, which is associated with the tetraheme type II cytochrome c3. The isolated Tmc complex contains four subunits, including the TpIIc3 (TmcA), an integral membrane cytochrome b (TmcC), and two cytoplasmically predicted proteins, an iron–sulfur protein (TmcB) and a tryptophan-rich protein (TmcD). Spectroscopic studies indicate the presence of eight hemes c and two hemes b in the complex pointing to an α2βγδ composition (TmcA2BCD). EPR analysis reveals the presence of a [4Fe4S]3+ center and up to three other iron–sulfur centers in the cytoplasmic subunit. Nearly full reduction of the redox centers in the Tmc complex could be obtained upon incubation with hydrogenase/TpIc3, supporting the role of this complex in transmembrane transfer of electrons resulting from periplasmic oxidation of hydrogen. [ABSTRACT FROM AUTHOR]

Rhodothermus marinus, a thermohalophilic Gram negative bacterium, contains a type I NADH/ quinone oxidoreductase (complex I). Its purification was optimized, yielding large amounts of pure and active protein. Furthermore, the stoichiometry of NADH oxidation and quinone reduction was shown to be 1:1. The large amounts of protein enabled a thorough characterization by electron paramagnetic resonance (EPR) spectroscopy at different temperatures and microwave powers, using NADH, NADPH, and dithionite as reducing agents. A minimum of two [2Fe-2S]²+/¹+ and four [4Fe-4S]²+/¹+ centers were observed in the purified complex. Redox titrations monitored by EPR spectroscopy made possible the determination of the reduction potentials of the iron–sulfur centers; with the exception of one of the [4Fe-4S]²+/¹+ centers, which has a lower reduction potential, all the other centers have reduction potentials of -240 ± 20 mV, pH 7.5. [ABSTRACT FROM AUTHOR]

The thermal unfolding of the plastocyanin from Phormidium laminosum, a thermophilic cyanobacterium, is herein described. The main objective of this work is to identify structural factors responsible for the higher stability observed in proteins from thermophilic organisms. With the aid of fluorescence spectroscopy, EPR, and NMR, the factors influencing the unfolding process of the protein were investigated, and procedures for its study have been standardized. The different spectroscopic techniques used provided consistent results showing that the thermal unfolding of plastocyanin is irreversible under all the conditions investigated and that this irreversibility does not appear to be related to the presence of oxygen. The oxidized plastocyanin species has proven to be more stable than the reduced one, with respect to both the required temperature for protein unfolding (up to a 9 °C difference between the two forms) and the kinetics of the process. The behavior of this plastocyanin contrasts with that of other cupredoxins whose unfolding had previously been studied. The unfolding pH dependence and kinetic studies indicate a process with a tight control around the physiological pH in which plastocyanin plays its redox role and the protein's isoelectric point (5.2), suggesting a close compromise between function and stability. [ABSTRACT FROM AUTHOR]

The aa[sub 3]-type quinol oxidase from Acidianus ambivalens is a divergent member of the hemecopper oxidases superfamily, namely, concerning the putative channels for intraprotein proton conduction. In this study, we used electrochemically induced FTIR difference spectroscopy to identify residues involved in redox-coupled protonation changes. In the spectral region characteristic for the v(C=O) mode from protonated aspartic or glutamic acid side chains, a number of prominent features can be observed between 1790 and 1710 cm[sup -1], clearly indicating the reorganization or protonation of more than four protonatable residues upon electron transfer. A direct comparison of the Fourier-transform infrared difference spectra at different pH values reveals the noteworthy high pK of >8 for some of these residues, and the protonation of two of them. These acidic residues may play a role in the proton transport to the oxygen reducing site, in proton pumping pathways, or in protonation reactions concomitant with quinone reduction. Whereas the residues contributing between 1790 and 1750 cm[sup -1] have the typical position of an aspartic/glutamic acid side chain buried in the protein, a position closer to the surface is suggested for the residues contributing below approximately 1730 cm[sup -1] The possible involvement of residues contributing between 1750 and 1720 cm[sup -1] in the quinone binding site is demonstrated on the basis of experiments in the presence and absence of ubiquinone-2 and of the native electron carrier of the A. ambivalens respiratory chain, caldariella quinone. Most signals seen here are not observable in comparable spectra of typical members of the heme copper oxidase superfamily and thus reflect unique features of the enzyme from the hyperthermoacidophilic archaeon A. ambivalens. [ABSTRACT FROM AUTHOR]

The article offers information on Superoxide reductase (SOR) and Superoxide dismutase (SOD). Superoxide is formed in all living organisms that come in contact with air, and it may act as a signaling agent, a toxic species, or a harmless intermediate. Over the time Superoxide decomposes spontaneously. Its levels are limited in -vivo by SOR and SOD.

A sulfide:quinone oxidoreductase (SQR) was isolated from the membranes of the hyperthermoa-cidophilic archaeon Acidianus ambivalens, and its X-ray structure, the first reported for an SQR, was determined to 2.6 A resolution. This enzyme was functionally and structurally characterized and was shown to have two redox active sites: a covalently bound FAD and an adjacent pair of cysteine residues. Most interestingly, the X-ray structure revealed the presence, of a chain of three sulfur atoms bridging those two cysteine residues; The possible implications of this observation in the catalytic mechanism for sulfide oxidation are discussed, and the role of SQR in the sulfur dependent bioenergetics of A. ambivalens, linked to oxygen reduction, is addressed. [ABSTRACT FROM AUTHOR]

Monoheme cytochromes of the C-type are involved in a large number of electron transfer processes, which play an essential role in multiple pathways, such as respiratory chains, either aerobic or anaerobic, and the photosynthetic electron transport chains. This study reports the biochemical characterization and the crystallographic structure, at 1.23 A resolution, of a monoheme cytochrome c from the thermohalophilic bacterium Rhodothermus marinus. In addition to an a-helical core folded around the heme, common for this type of cytochrome, the X-ray structure reveals one unusual ct-helix and a unique N-terminal extension, which wraps around the back of the molecule. Based on a thorough structural and amino acid sequence comparison, we propose R. marinus cytochrome c as the first characterized member of a new class of C-type cytochromes. [ABSTRACT FROM AUTHOR]

A comprehensive study of the thermodynamic redox behavior of the hemes from the cbb3 oxygen reductase from Bradyrhizobium japonicum was performed. This enzyme is a member of the C-type heme-copper oxygen reductase superfamily and has three subunits with six redox centers: four low-spin hemes and a high-spin heme and one copper ion, composing the site where oxygen is reduced. In this analysis, the visible spectra and redox properties of the five heme centers were deconvoluted. Their redox profiles and the pH dependence of the midpoint reduction potentials (redox-Bohr effect) were investigated. The reference reduction potentials (defined for a state where all centers are reduced) and homotropic interaction potentials were determined in the framework of a model of pairwise interacting redox centers. At pH 7.7, the reference reduction potentials for the three hemes c are 390, 300, and 220 mY, with low interaction potentials between them, weaker than -15 mV. For hemes b and b3, reference reduction potentials of 375 and 290 mV, respectively, were obtained; these two redox centers show an interaction potential weaker than -60 mV. The midpoint reduction potentials of all five hemes are pH-dependent. The study of these thermodynamic parameters is important in understanding the coupling mechanism of the redox and chemical processes during oxygen reduction. The analysis of the thermodynamic redox behavior of the cbb3 oxygen reductase contributes to the investigation of the mechanism of electron transfer and proton translocation by heme-copper oxygen reductases in general and indicates a thermodynamic coupling for the electron and proton transfer mechanisms. [ABSTRACT FROM AUTHOR]

Superoxide reductases (SORs), iron-centered enzymes responsible for reducing superoxide (O2-) to hydrogen peroxide, are found in many anaerobic and microaerophilic prokaryotes. The rapid reaction with an exogenous electron donor renders the reductase activity catalytic. Here, we demonstrate using pulse radiolysis that the initial reaction between O2 and Archaeoglobus fulgidus neelaredoxin, a one-iron SOR, leads to a short-lived transient that immediately disappears to yield a solvent-bound ferric species in acid–base equilibrium. Through comparison of wild-type neelaredoxin with mutants lacking the ferric ion coordinating glutamate, we demonstrate that the remaining step is related to the final coordination of this ligand to the oxidized metal center and kinetically characterize it for the first time, by pulse radiolysis and stopped-flow kinetics. The way exogenous phosphate perturbs the kinetics of superoxide reduction by neelaredoxin and mutant proteins was also investigated. [ABSTRACT FROM AUTHOR]

Sulfate-reducing organisms use sulfate as an electron acceptor in an anaerobic respiratory process. Despite their ubiquitous occurrence, sulfate respiration is still poorly characterized. Genome analysis of sulfate-reducing organisms sequenced to date permitted the identification of only two strictly conserved membrane complexes. We report here the purification and characterization of one of these complexes, DsrMKJOP, from Desulfovibrio desulfuricans ATCC 27774. The complex has hemes of the c and b types and several iron-sulfur centers. The corresponding genes in the genome of Desulfovibrio vulgaris were analyzed. dsrM encodes an integral membrane cytochrome b; dsrK encodes a protein homologous to the HdrD subunit of heterodisulfide reductase; dsrJ encodes a triheme periplasmic cytochrome c; dsrO encodes a periplasmic FeS protein; and dsrM encodes another integral membrane protein. Sequence analysis and EPR studies indicate that DsrJ belongs to a novel family of multiheme cytochromes c and that its three hemes have different types of coordination, one bis-His, one His/Met, and the third a very unusual His/Cys coordination. The His/Cys-coordinated heme is only partially reduced by dithionite. About 40% of the hemes are reduced by menadiol, but no reduction is observed upon treatment with H2 and hydrogenase, irrespective of the presence of cytochrome c3. The aerobically isolated Dsr complex displays an EPR signal with similar characteristics to the catalytic {4Fe-4S]3+ species observed in heterodisulfide reductases. Further five different [4Fe-4S]3+/1+ centers are observed during a redox titration followed by EPR. The role of the DsrMKJOP complex in the sulfate respiratory chain of Desulfovibrio spp. is discussed. [ABSTRACT FROM AUTHOR]

The aa3 type B oxygen reductase from the thermophilic archaeon Acidianus ambivaleris (QO) was immobilized on silver electrodes and studied by potential-dependent surface-enhanced resonance Raman (SERR) spectroscopy. The immobilized enzyme retains the native structure at the level of the heme pockets and exhibits reversible electrochemistry. From the potential dependence of specific spectral marker bands, the midpoint potentials of hemes a and a3 were unambiguously determined for the first time, being 320 ± 20 mV for the former and 390 ± 20 mV for the latter. Both hemes could be treated as independent one-electron Nernstian redox couples, indicating that the interaction potential is smaller than 50 mV. The reversed order of the midpoint potentials compared to those of type A (mitochondrial-like) oxidases, as well as the lack of substantial Coulombic interactions, suggests a different mechanism of electroprotonic energy transduction. In contrast to type A enzymes, a-a3 intraprotein electron transfer in QO is already guaranteed by the order of the midpoint potentials at the onset of enzyme reduction and, therefore, does not require a complex network of cooperativities to ensure exergonicity. In the immobilized state, conformational transitions of the QO a3-CUB active site, which are believed to be essential for proton translocation, are drastically slowed compared to those in solution. We ascribe this finding to the effect of the interfacial electric field, which is of the same order of magnitude as in biological membranes. These results suggest that the membrane potential may play an active role in the regulation of the enzymatic activity of QO. [ABSTRACT FROM AUTHOR]

Investigates the ligand-binding dynamics and the reaction of cytochrome caa[sub 3] from the thermophilic bacterium Rhodothermus marinus. Characteristics of thermophilic enzymes; Observation of heme c; Comparison of the slower transmission time of bovine enzyme.