The design of jobs is defined and its different implications. These aspects must be taken into consideration when applied to new automated systems, once it can occur workers in-adaptations to certain type of activity and tasks. Other concepts that emerge from this are the mental workload, stress, work accidents, shift work, or the physical environment that can reveal to become determinant in the process of job design. That means also the organizational design. In this sense, the manufacturing, organizational and individual dimensions, are the most meaningful in the mentioned process of organizational design. Are analyzed different application cases of robotized systems and their social effects, mostly those that are related to the dimensions of working conditions. Are particularly analyzed the new risk situations that occur with the use of robotic systems. One concludes on the need to take into consideration qualitative variables in the definition and design of robotic cells, jobs and production systems. This consideration influences directly in the labor productivity, in such way that the development of these methodologies of analysis can be considered as integrating the processes of technological innovation in manufacturing.

On photolysis of solutions of azulene and uranyl nitrate in alcohols, a dark, amorphous precipitate is formed. Various analytical techniques show that this is a mixture of a uranium salt and an organic component, suggested to be polyazulene. The effects of various parameters on the yield of the product have been studied and it is found that oxygen facilitates the reaction. Electron spin resonance studies show that the product is paramagnetic, in agreement with the established ease of oxidation of polyazulene, and suggest that it is formed via electron transfer from azulene to excited uranyl ion, followed by successive dimerizations and deprotonations of radical cation intermediates.

A soluble [NiFe] hydrogenase has been partially purified from the obligate thermophilic sulfate-reducing bacterium Thermodesulfobacterium mobile. A 17% purification yield was obtained after four chromatographic steps and the hydrogenase presents a purity index (A398 nm/A277 nm) equal to 0.21. This protein appears to be 75% pure on SDS-gel electrophoresis showing two major bands of molecular mass around 55 and 15 kDa. This hydrogenase contains 0.6-0.7 nickel atom and 7-8 iron atoms per mole of enzyme and has a specific activity of 783 in the hydrogen uptake reaction, of 231 in the hydrogen production assay and of 84 in the deuterium-proton exchange reaction. The H2/HD ratio is lower than one in the D2-H+ exchange reaction. The enzyme is very sensitive to NO, relatively little inhibited by CO but unaffected by NO2-. The EPR spectrum of the native hydrogenase shows the presence of a [3Fe-4S] oxidized cluster and of a Ni(III) species.

A novel iron-sulfur protein was purified from the extract of Desulfovibrio desulfuricans (ATCC 27774) to homogeneity as judged by polyacrylamide gel electrophoresis. The purified protein is a monomer of 57 kDa molecular mass. It contains comparable amounts of iron and inorganic labile sulfur atoms and exhibits an optical spectrum typical of iron-sulfur proteins with maxima at 400, 305, and 280 nm. Mossbauer data of the as-isolated protein show two spectral components, a paramagnetic and a diamagnetic, of equal intensity. Detailed analysis of the paramagnetic component reveals six distinct antiferromagnetically coupled iron sites, providing direct spectroscopic evidence for the presence of a 6Fe cluster in this newly purified protein. One of the iron sites exhibits parameters (delta EQ = 2.67 +/- 0.03 mm/s and delta = 1.09 +/- 0.02 mm/s at 140 K) typical for high spin ferrous ion; the observed large isomer shift indicates an iron environment that is distinct from the tetrahedral sulfur coordination commonly observed for the iron atoms in iron-sulfur clusters and is consistent with a penta- or hexacoordination containing N and/or O ligands. The other five iron sites are most probably high spin ferric. Three of them show parameters characteristic for tetrahedral sulfur coordination. In correlation with the EPR spectrum of the as-purified protein which shows a resonance signal at g = 15.3 and a group of signals between g = 9.8 and 5.4, this 6Fe cluster is assigned to an unusual spin state of 9/2 with zero field splitting parameters D = -1.3 cm-1 and E/D = 0.062. Other EPR signals attributable to minor impurities are also observed at the g = 4.3 and 2.0 regions. The diamagnetic Mossbauer component represents a second iron cluster, which, upon reduction with dithionite, displays an intense S = 1/2 EPR signal with g values at 2.00, 1.83, and 1.31. In addition, an EPR signal of the S = 3/2 type is also observed for the dithionite-reduced protein.

Mossbauer spectroscopy was used to study the tetraheme cytochrome c3 from Desulfovibrio baculatus (DSM 1743). Samples with different degrees of reduction were prepared using a redoxtitration technique. In the reduced cytochrome c3, all four hemes are reduced and exhibit diamagnetic Mossbauer spectra typical for low-spin ferrous hemes (S = 0). In the oxidized protein, the hemes are low-spin ferric (S = 1/2) and exhibit overlapping magnetic Mossbauer spectra. A method of differential spectroscopy was applied to deconvolute the four overlapping heme spectra and a crystal-field model was used for data analysis. Characteristic Mossbauer spectral components for each heme group are obtained. Hyperfine and crystal-field parameters for all four hemes are determined from these deconvoluted spectra.

The Desulfovibrio gigas aldehyde-oxido-reductase contains molybdenum and iron-sulfur clusters. Mossbauer spectroscopy was used to characterize the iron-sulfur clusters. Spectra of the enzyme in its oxidized, partially reduced and benzaldehyde-reacted states were recorded at different temperatures and applied magnetic fields. All the iron atoms in D. gigas aldehyde oxido-reductase are organized as [2Fe-2S] clusters. In the oxidized enzyme, the clusters are diamagnetic and exhibit a single quadrupole doublet with parameters (delta EQ = 0.62 +/- 0.02 mm/s and delta = 0.27 +/- 0.01 mm/s) typical for the [2Fe-2S]2+ state. Mossbauer spectra of the reduced clusters also show the characteristics of a [2Fe-2S]1+ cluster and can be explained by a spin-coupling model proposed for the [2Fe-2S] cluster where a high-spin ferrous ion (S = 2) is antiferromagnetically coupled to a high-spin ferric ion (S = 5/2) to form a S = 1/2 system. Two ferrous sites with different delta EQ values (3.42 mm/s and 2.93 mm/s at 85 K) are observed for the reduced enzyme, indicating the presence of two types of [2Fe-2S] clusters in the D. gigas enzyme. Taking this observation together with the re-evaluated value of iron content (3.5 +/- 0.1 Fe/molecule), it is concluded that, similar to other Mo-hydroxylases, the D. gigas aldehyde oxido-reductase also contains two spectroscopically distinguishable [2Fe-2S] clusters.

The magnetic properties of the nickel(II) site in active Desulfovibrio baculatus (DSM 1743) [NiFeSe] hydrogenase have been measured using the multifield saturation magnetization technique. The periplasmic [NiFeSe] hydrogenase was isolated from bacteria grown in excess selenium in the presence of 57Fe. Saturation magnetization data were collected at three fixed fields (1.375, 2.75, 5.5 tesla) over the temperature range from 2 to 100 K. Mossbauer and EPR spectroscopies were used to characterize the magnetic state of the two [4Fe-4S] clusters of the enzyme and to quantitate the small amounts of iron impurities present in the sample. The nickel(II) site was found to be diamagnetic (low spin, S = 0). In combination with recent results from extended x-ray absorption fine structure studies, this magnetic state indicates that the nickel(II) site of active D. baculatus [NiFeSe] hydrogenase is five-coordinate.

The effects of polyammonium macrocycles on the spectroscopic and photochemical properties of the Co(EDTA)- . I- ion-pair have been investigated. The addition of a macrocycle to aqueous solutions containing Co(EDTA)- and I- causes an increase of the absorbance in the region of the ion-pair charge-transfer band, as well as an increase of the quantum yield for the intramolecular photooxidation reduction of the ion-pair. Both these effects are mainly, if not only, due to an increase of the association constant between Co(EDTA)- and I-, caused by the positive charge of the macrocycle bound to the complex. On the contrary no change was observed on the intrinsic photoreactivity of the excited ion-pair. This last result is discussed in comparison with the effects already observed on the ligand photodissociation of MC excited states of Co(III) cyanide complexes.

The photochemistry of aqueous solutions of [Co(CN)5H2O]2- in the presence of the polyammonium macrocyclic receptor [32]ane-N8H88+ was studied. The quantum yield for cyanide release in free [Co(CN)5H2O]2- (PHI = 0.003 at 313 nm, pH 1.5) is reduced approximately threefold in the presence of the protonated macrocycle, which provides evidence for the formation of a supramolecular structure. Further evidence for the supramolecular structure is obtained from the thermal anation of [Co(CN)5H2O]2- with Br- (40-degrees-C, pH 1.0), the rate of which is increased in the presence of [32]ane-N8H88+, suggesting that the ligand water is not involved in hydrogen bonds with the macrocycle. These results are interpreted in terms of possible supramolecular structures.

Using 2D-NMR the four haems of Desulfovibrio vulgaris (Hildenborough) cytochromes, within the X-ray structure were fully cross-assigned according to their redox potential. The strategy used was based on a complete network of chemical exchange connectivities between the NMR signals obtained for all oxidation levels to the corresponding ones in the fully reduced spectrum [1992, Eur. J. Biochem., in press]. This unequivocal cross-assignment disagrees within earlier results obtained for the similar protein from Desulfovibrio vulgaris (Miyazaki F.) [1991, FEBS Lett. 285, 149–151]

Two-dimensional NMR has been used to make specific assignments for the four haems in Desulfovibrio vulgaris (Hildenborough) ferrocytochrome c3 and to determine their haem core architecture. The NMR signals from the haem protons were assigned according to type using two-dimensional NMR experiments which led to four sets of signals, one for each of the haems. Specific assignments were obtained by calculating the ring current shifts which arise from other haems and aromatic residues. Observation of interhaem NOEs confirmed the assignments and established that the relative orientation of the haems is identical to that found in the crystal structure of D. vulgaris (Miyazaki F.) ferricytochrome c3. Assignments were also made for all the aromatic residues except for the haem ligands and F20, which is shifted under the main envelope of signals. The NOEs observed between these aromatic protons and haem protons confirm the similarity between the structures in solution and in the crystal. The assignments reported here are the basis for the cross-assignments of the four microscopic haem redox potentials to specific haems in the protein structure.

A novel iron-sulfur protein was purified from the extract of Desulfovibrio desulfuricans (ATCC 27774) to homogeneity as judged by polyacrylamide gel electrophoresis. The purified protein is a monomer of 57 kDa molecular mass. It contains comparable amounts of iron and inorganic labile sulfur atoms and exhibits an optical spectrum typical of iron-sulfur proteins with maxima at 400, 305, and 280 nm. Mossbauer data of the as-isolated protein show two spectral components, a paramagnetic and a diamagnetic, of equal intensity. Detailed analysis of the paramagnetic component reveals six distinct antiferromagnetically coupled iron sites, providing direct spectroscopic evidence for the presence of a 6Fe cluster in this newly purified protein. One of the iron sites exhibits parameters (DELTA-E(Q) = 2.67 +/- 0.03 mm/s and delta = 1.09 +/- 0.02 mm/s at 140 K) typical for high spin ferrous ion; the observed large isomer shift indicates an iron environment that is distinct from the tetrahedral sulfur coordination commonly observed for the iron atoms in iron-sulfur clusters and is consistent with a penta- or hexacoordination containing N and/or O ligands. The other five iron sites are most probably high spin ferric. Three of them show parameters characteristic for tetrahedral sulfur coordination. In correlation with the EPR spectrum of the as-purified protein which shows a resonance signal at g = 15.3 and a group of signals between g = 9.8 and 5.4, this 6Fe cluster is assigned to an unusual spin state of 9/2 with zero field splitting parameters D = -1.3 cm-1 and E/D = 0.062. Other EPR signals attributable to minor impurities are also observed at the g = 4.3 and 2.0 regions. The diamagnetic Mossbauer component represents a second iron cluster, which, upon reduction with dithionite, displays an intense S = 1/2 EPR signal with g values at 2.00, 1.83, and 1.31. In addition, an EPR signal of the S = 3/2 type is also observed for the dithionite-reduced protein.

A c-type monoheme ferricytochrome c550 (9.6 kDa) was isolated from cells of Bacillus halodenitrificans sp.nov., grown anaerobically as a denitrifier. The visible absorption spectrum indicates the presence of a band at 695 nm characteristic of heme–methionine coordination. The mid-point redox potential was determined at several pH values by visible spectroscopy. The redox potential at pH 7.6 is 138 mV. When studied by 1H-NMR spectroscopy as a function of pH, the spectrum shows a pH dependence with pKa values of 6.0 and 11.0. According to these pKa values, three forms designated as I, II and III can be attributed to cytochrome c550. The first pKa is probably associated with protonation of the propionate groups. The second pKa value introduces a larger effect in the 1H-NMR spectrum and is probably due to the ionisation of the axial histidine. Studies of temperature variation of the 1H-NMR spectra for both the ferrous and ferri forms of the cytochrome were performed. Heme meso protons, the heme methyl groups, the thioether protons, two protons from a propionate and the methylene protons from the axial methionine were identified in the reduced form. The heme methyl resonances of the ferri form were also assigned. EPR spectroscopy was also used to probe the ferric heme environment. A signal at gmax∼ 3.5 at pH 7.5 was observed indicating an almost axial heme environment. At higher pH values the signal at gmax∼ 3.5 converts mainly to a signal at g∼ 2.96. The pKa associated with this change is around 11.3. The N-terminal sequence of this cytochrome was determined and compared with known amino acid sequences of other cytochromes.

Adenylyl sulfate (APS) reductase, the key enzyme of the dissimilatory sulfate respiration, catalyzes the reduction of APS (the activated form of sulfate) to sulfite with release of AMP. A spectroscopic study was carried out with the APS reductase purified from the extremely thermophilic sulfate-reducing archaebacterium Archaeoglobus fulgidus DSM 4304. Combined ultraviolet/visible spectroscopy and low temperature electron paramagnetic resonance (EPR) studies were used in order to characterize the active centers and the reactivity towards AMP and sulfite of this enzyme. The A. fulgidus APS reductase is an iron-sulfur flavoprotein containing two distinct [4Fe-4S] clusters (Centers I and II) very similar to the homologous enzyme from Desulfovibrio gigas. Center I, which has a high redox potential, is reduced by AMP and sulfite, and Center II has a very negative redox potential.

The single iron site of rubredoxin was replaced by nickel and cobalt. The near-infrared/visible/UV spectra of these metal derivatives show ligand-field transitions and charge-transfer bands which closely resemble those of simple tetrathiolate complexes, indicating a tetrahedral arrangement of the sulfur cysteinyl ligands around the metal core. The 1H NMR spectra of the nickel and cobalt derivatives reveal extremely low-field contact shifted resonances of one proton intensity assigned to beta-CH2 and alpha-CH cysteinyl protons. Other well resolved resonances shifted out of the main protein spectral envelope are also observed and probably arise from contact plus pseudocontact shift mechanisms. Rubredoxins from different sulfate reducers were metal substituted and assignments of aliphatic protons are tentatively proposed, taking advantage of the amino acid sequence homologies. The present data is promising in terms of structural analysis of the coordination sphere of the metal core. It was also shown that replacement of the iron atom of desulforedoxin, a close analogue of rubredoxin, by cobalt and nickel was possible.

Following the discovery of the tetraheme cytochrome c3 in the strict anaerobic sulfate-reducing bacteria (Postgate, J.R. (1954) Biochem. J. 59, xi; Ishimoto et al. (1954) Bull. Chem. Soc. Japan 27, 564-565), a variety of c-type cytochromes (and others) have been reported, indicating that the array of heme proteins in these bacteria is complex. We are proposing here a tentative classification of sulfate- (and sulfur-) reducing bacteria cytochromes c based on: number of hemes per monomer, heme axial ligation, heme spin state and primary structures (whole or fragmentary). Different and complementary spectroscopic tools have been used to reveal the structural features of the heme sites.

The direct unmediated electrochemical response of the tetrahemic cytochrome c3 isolated from sulfate reducers Desulfovibrio baculatus (DSM 1743) and D. vulgaris (strain Hildenborough), was evaluated using different electrode systems [graphite (edge cut), gold, semiconductor (InO2) and mercury)] and different electrochemical methods (cyclic voltammetry and differential pulse voltammetry). A computer program was developed for the theoretical simulation of a complete cyclic voltammetry curve, based on the method proposed by Nicholson and Shain [Nicholson, R.S. & Shain, I. (1964) Anal. Chem. 36, 706-723], using the Gauss-Legendre method for calculation of the integral equations. The experimental data obtained for this multi-redox center protein was deconvoluted in to the four redox components using theoretically generated cyclic voltammetry curves and the four mid-point reduction potentials determined. The pH dependence of the four reduction potentials was evaluated using the deconvolution method described.

E.p.r. spectra of reduced iron-sulphur centres of the aldehyde oxidoreductase (iron-molybdenum protein) of Desulfovibrio gigas were recorded at X-band and Q-band frequencies and simulated. Results are consistent with the view that only two types of [2Fe-2S] clusters are present, as in eukaryotic molybdenum-containing hydroxylases. The data indicate the Fe/SI centre to be very similar, and the Fe/SII centre somewhat similar, to these centres in the eukaryotic enzymes.