Manual de Direito do Trabalho
Xavier, Bernardo da Gama Lobo
2011-01-01
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Nitrogenase catalyzes the biological reduction of N2 to ammonia (nitrogen fixation). The metalloclusters associated with the nitrogenase components include the [4Fe-4S] cluster of the Fe protein, and the P-cluster [8Fe7S] and FeMo-cofactor [7Fe-9S-Mo-X-homocitrate], both contained within the MoFe protein. These metal-complexes play a vital role in enzyme activity during electron transport and substrate reduction. It is known that the FeMo-cofactor provides the site of substrate reduction, but the exact site of substrate binding remains a topic of intense debate. Some models for the substrate binding location favor the molybdenum atom, while other models favor one or more iron atoms within FeMo-cofactor. We have shown that the a-70 residue of the MoFe protein plays a significant role in defining substrate access to the active site: a-70...
Mycothiol (MSH), a low-molecular- weight thiol, is a primary reducing agent and essential for the survival of mycobacteria. The full pathway of MSH biosynthesis and detoxification includes various promising drug targets. Several metalloenzymes are involved in this pathway, such as a deacetylase (MshB) and mycothiol S-conjugate amidase (MCA). MshB catalyzes the deacetylation of GlcNAc-Ins to form GlcN-Ins and acetate. Mycothiol S-conjugate amidase (MCA) cleaves the amide bond of mycothiol S-conjugates of various drugs and toxins. The identification of the native co-factor is critical for the design of potent and effective inhibitors. Therefore, in this study, we identified the possible native co-factors of MshB and MCA from M. smegmatis and M. tuberculosis.
To reach our aim, we used a pull-down method to rapidly purify halo-MshB and hal...
The Casimir force for charge-neutral, perfect conductors of non-planar geometric configurations have been investigated. The configurations were: (1) the plate-hemisphere, (2) the hemisphere-hemisphere and (3) the spherical shell. The resulting Casimir forces for these physical arrangements have been found to be attractive. The repulsive Casimir force found by Boyer for a spherical shell is a special case requiring stringent material property of the sphere, as well as the specific boundary conditions for the wave modes inside and outside of the sphere. The necessary criteria in detecting Boyer's repulsive Casimir force for a sphere are discussed at the end of this thesis.
This thesis pursues the hints of a categorical delooping that are suggested when enrichment is iterated. At each stage of successive enrichments, the number of monoidal products decreases and the categorical dimension increases, both by one. This is mirrored by topology. When we consider the loop space of a topological space, we see that paths (or 1--cells) in the original are now points (or objects) in the derived space. There is also automatically a product structure on the points in the derived space, where multiplication is given by concatenation of loops. Delooping is the inverse functor here, and thus involves shifting objects to the status of 1--cells and decreasing the number of ways to multiply.
We define V-(n+1)--categories as categories enriched over V--n--Cat, the (k-n)--fold monoidal strict (n+1)--category of V--n--categor...
Multipath on far-field antenna ranges causes distortion of antenna pattern measurements: The multipath components have differing path lengths and hence can be separated by illuminating the antenna under test with short-duration pulses. Alternatively, antenna measurements can be made in the frequency domain, and the Fourier transform can be used to relate the frequency-domain measurements to the antennaâs time-domain response. The interference then can be removed with a time-domain gate, and transformed back into the frequency domain to yield improved CW antenna patterns. Virginia Tech has recently completed a major upgrade of their far-field antenna range and implemented a system to perform this data collection and data processing. This thesis describes the principles and implementation of the time-domain processing part of the system....
The phosphatidylinositol signaling pathway utilizes inositol-containing second messengers to mediate signaling events. The enzymes that metabolize phosphoinositides can in some cases serve to terminate the signaling actions of phosphoinositides. The inositol polyphosphate 5-phosphatases (5PTases) comprise a large protein family that hydrolyzes 5-phosphates from a variety of inositol phosphate and phosphoinositide substrates. I have examined the substrate specificity of the At5PTase11 protein from the model plant, Arabidopsis thaliana. The At5PTase11 gene (At1g47510) encodes an active 5PTase enzyme that can dephosphorylate the phosphoinositide substrates phosphatidylinositol 4,5-bisphosphate [PtdIns(4,5)P2], phosphatidylinositol 3,5-bisphosphate [PtdIns(3,5)P2], and phosphatidylinositol 3,4,5-trisphosphate [PtdIns(3,4,5)P3]. In addition...
Detailed studies are presented of thin films that self-assemble into the noncentrosymmetric structure required for second order nonlinear optical responses. Second harmonic generation is used as a probe of the second-order nonlinear optical susceptibility (c(2)) of ionic self-assembled monolayer (ISAM) films. Films produced from the ISAM technique are shown to possess significant c(2), with values presently comparable to quartz (c(2)=1.53*10-9 esu). These films show exceptional stability over time, with negligible decrease in c(2) after 26 months.
ISAM films self-assemble from polyelectrolyte solutions due to coulombic interactions between a charged substrate and the charged polymer in solution. This process is self-limiting since charge overcompensation at the surface restricts further deposition as like charges accumulate at the surf...
Mo-nitrogenase consists of two component proteins, the Fe protein and the MoFe protein. The site of substrate binding and reduction within the Mo-nitrogenase is provided by a metallocluster, the FeMo cofactor, located in the a-subunit of the MoFe protein. The FeMo cofactorâs polypeptide environment appears to be intimately involved in the delicate control of the MoFe proteinâs interactions with its substrates and inhibitors (Fisher K et al., 2000c). In this work, the a-subunit 278-serine residue of the MoFe protein was targeted because (i) a serine residue at this position is conserved both in the Mo-nitrogenase from all organisms examined and in the alternative nitrogenases (Dean, DR and Jacobson MR, 1992); (ii) its hydroxyl group hydrogen bonds to the Sg of the a-subunit 275-cysteine residue that directly ligates the FeMo cofactor; ...
This study is an investigation of the life of Benjamin Hallowell (1799-1877) a significant contributor to the spread of useful knowledge in the middle (1824-1877) of the nineteenth century. During this period the advancement of knowledge, once the domain of the landed gentry, became the province of the middle class citizen.
The majority of studies of individuals influential in the spread of knowledge center on persons who had a national influence or on those who were active in the northeastern United States where the leading educational efforts flourished. Using historical research, a methodical, critical gathering and interpretation of knowledge from past and present records, we examine Hallowell's work in establishing learning institutions.
Hallowell's life work was examined in the light of his use of adult education as a means of fu...
