Crystallization, preliminary X-ray analysis and molecular-replacement solution of the carboxy form of haemoglobin I from the fish Brycon cephalus

Haemoglobin, the 'honorary enzyme' [Brunori (1999), Trends Biochem. Sci. 24, 158-161], constitutes a prime prototype for allosteric models. Here, the crystallization and preliminary X-ray analysis of haemoglobin I from the South American fish Brycon cephalus are reported. X-ray diffraction data have been collected to 2.5 Angstrom resolution using synchrotron radiation (LNLS). Crystals were determined to belong to the space group P6(1)22 and preliminary structural analysis revealed the presence of one dimer (alpha beta) in the asymmetric unit. The structure was determined using standard molecular-replacement techniques.

Spectroscopic and electrochemical characterization of polyaniline and a ruthenium complex, mer-[RuCl3(dppb)(py)], in the form of Langmuir-Blodgett films

Langmuir monolayers and Langmuir-Blodgett (LB) films have been produced from polyaniline and a biphosphinic ruthenium complex, referred to as Rupy. Strong, repulsive interaction between the two components led to a nonlinear change in area per molecule and surface potential with the concentration of Rupy in the mixed film. Molecular interaction was also denoted in the spectroscopic and electrochemical properties of the Y-type LB transferred films. The Raman spectra of mixed PANI-Rupy films indicated that the degree of oxidation of PANI increased linearly with the concentration of Ropy. With PANI being increasingly oxidized by presence of Rupy, the electroactivity of the mixed films decreased with the amount of Rupy, to become undetectable when the mixed LB film is 501 mol in Rupy. The presence of Rupy caused the electrical properties of the mixed LB films to be less sensitive to environmental changes. The electrical capacitance of a mixed film changed only by 15% when the sample was taken from vacuum to air, whereas the change was 215% for a pure PANI LB film.

Bioremediation of direct dyes in simulated textile effluents by a paramorphogenic form of Aspergillus oryzae

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

The influence of hydrogen plasma pre-treatment on the structure of BDND electrode surface applied for phenol detection

The surface properties of boron-doped nanocrystalline diamond films treated with H(2) plasma was investigated in regard to their electrochemical response for phenol oxidation. The surface of these films is relatively flat formed by crystallites with sizes of about 40 nm. X-ray photoelectron spectroscopy analyses showed that electrode surface has a high amount of C-H bonds. This behavior is in agreement with Mott-Schottky plot measurements concerning the flat band potential that presented a value as expected for hydrogenated diamond surface. This electrode presented the phenol detection limit of 0.08 mg L(-1) for low phenol concentrations from 40 to 250 mu mol L(-1).

Mechanistic approach to predict real machining time for milling free-form geometries applying high feed rate

An accurate estimate of machining time is very important for predicting delivery time, manufacturing costs, and also to help production process planning. Most commercial CAM software systems estimate the machining time in milling operations simply by dividing the entire tool path length by the programmed feed rate. This time estimate differs drastically from the real process time because the feed rate is not always constant due to machine and computer numerical controlled (CNC) limitations. This study presents a practical mechanistic method for milling time estimation when machining free-form geometries. The method considers a variable called machine response time (MRT) which characterizes the real CNC machine's capacity to move in high feed rates in free-form geometries. MRT is a global performance feature which can be obtained for any type of CNC machine configuration by carrying out a simple test. For validating the methodology, a workpiece was used to generate NC programs for five different types of CNC machines. A practical industrial case study was also carried out to validate the method. The results indicated that MRT, and consequently, the real machining time, depends on the CNC machine's potential: furthermore, the greater MRT, the larger the difference between predicted milling time and real milling time. The proposed method achieved an error range from 0.3% to 12% of the real machining time, whereas the CAM estimation achieved from 211% to 1244% error. The MRT-based process is also suggested as an instrument for helping in machine tool benchmarking.

Quantitative Phase Analyses Through The Rietveld Method with X-Ray Powder Diffraction Data of Heat-Treated Carbamazepine Form III

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Crystal structure of the triclinic form of (2tbpo·H +)2tetrachlorocuprate(II){[(PhCH2) 3PO]2H}2CuCl4: The presence of extremely short O-H-O interactions

The structure of {[(PhCH2)3PO]2H} 2CuCl4 has been shown to contain four [(PhCH 2)3PO]2H+ cations with extremely short O-H-O distances of 2.295, 2.364, 2.394, and 2.404 Å, respectively.

Use of lipopolysaccharides to characterize Bradyrhizobium spp.

Three methods of extraction of lipopolysaccharide (LPS) were compared-the conventional hot phenol-water method with 40% phenol, a modified form of this method using 10% phenol, and the hot saline method. Good recovery of LPS was achieved by each of the three methods, with the LPS found in the aqueous phase with the two phenol-based procedures. The application of SDS-PAGE to the LPS extracts, followed by silver staining, showed similar banding with all three methods of extraction. When the hot saline extraction LPS fraction from eight strains of Bradyrhizobium spp. and eight strains of Bradyrhizobium japonicum was compared with SDS-PAGE, characteristic profiles were achieved. Serological analysis of eight strains of Bradyrhizobium spp., using antisera prepared against whole cells in agglutination reactions, showed extensive sharing of antigens. When antisera was prepared using outer membrane LPS, extracted by the hot saline method, the amount of cross-reaction was reduced greatly. The results indicated that LPS provide an efficient means of obtaining monospecific antisera to be used for serological identification of strains of Bradyrhizobium spp. and that the hot saline extraction method is recommended for a fast, simple and efficient way to obtain LPS and characterize this bacterium.

Occurrence of form PIIcf sieve-element plastids in Xyris species (Xyridaceae)

Mature leaf fragments from eight species of Xyris from the Serra do Cipo, State of Minas Gerais, Brazil, were prepared by the usual methods for electron microscopy. Ultrastructural analysis of phloem shows the occurrence of nacreous walls with a polylamellate structure in the sieve-elements of X. tortilis and plastids similar to P-plastids, form PIIcf in the sieve-elements of all investigated species.

Interaction in culture medium of acttnomycetes and native fungi wtth rhizobia that form nodules in Neonotonia wighth lackley (perennial soybean)

The relationship between soil fungi and actinomycetes, with rhizobia that produce nodulation in Neonotonia wightii (perennial soybean) was studied in culture medium in order to obtain material to be used in mixed inoculations of this legume. A field experiment was designed to provide soil samples and isolate microorganisms belonging to these groups that are capable of interfering in the development of two selected rhizobium strains. Results show that the Bradyrhizobium strains used in the experiment, which are efficient in nodulation of Neonotonia wightii, are highly sensitive to substances produced in the culture medium by actinomycetes and fungi.

Relativistic quark spin coupling effects in the nucleon electromagnetic form factors

We investigate the effect of different forms of relativistic spin coupling of constituent quarks in the nucleon electromagnetic form factors. The four-dimensional integrations in the two-loop Feynman diagram are reduced to the null-plane, such that the light-front wave function is introduced in the computation of the form factors. The neutron charge form factor is very sensitive to different choices of spin coupling schemes, once its magnetic moment is fitted to the experimental value. The scalar coupling between two quarks is preferred by the neutron data, when a reasonable fit of the proton magnetic momentum is found. (C) 2000 Elsevier Science B.V.

Electromagnetic form factor of the pion in the space- and time-like regions within the front-form dynamics

The pion electromagnetic form factor is calculated in the space- and time-like regions from -10 (GeV/c)2 up to 10 (GeV/c)2, within a front-form model. The dressed photon vertex where a photon decays in a quark-antiquark pair is depicted generalizing the vector meson dominance ansatz, by means of the vector meson vertex functions. An important feature of our model is the description of the on-mass-shell vertex functions in the valence sector, for the pion and the vector mesons, through the front-form wave functions obtained within a realistic quark model. The theoretical results show an excellent agreement with the data in the space-like region, while in the time-like region the description is quite encouraging. © 2003 Elsevier B.V. All rights reserved.