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The functional and structural significance of the intrasubunit disulfide bond in copper-zinc superoxide dismutase (SOD1) was studied by characterizing mutant forms of human SOD1 (hSOD) and yeast SOD1 lacking the disulfide bond. We determined x-ray crystal structures of metal-bound and metal-deficient hC57S SOD1. C57S hSOD1 isolated from yeast contained four zinc ions per protein dimer and was structurally very similar to wild type. The addition of copper to this four-zinc protein gave properly reconstituted 2Cu,2Zn C57S hSOD, and its spectroscopic properties indicated that the coordination geometry of the copper was remarkably similar to that of holo wild type hSOD1. In contrast, the addition of copper and zinc ions to apo C57S human SOD1 failed to give proper reconstitution. Using pulse radiolysis, we determined SOD activities of yeast and human SOD1s lacking disulfide bonds and found that they were enzymatically active at ∼10% of the wild type rate. These results are contrary to earlier reports that the intrasubunit disulfide bonds in SOD1 are essential for SOD activity. Kinetic studies revealed further that the yeast mutant SOD1 had less ionic attraction for superoxide, possibly explaining the lower rates. Saccharomyces cerevisiae cells lacking the sod1 gene do not grow aerobically in the absence of lysine, but expression of C57S SOD1 increased growth to 30-50% of the growth of cells expressing wild type SOD1, supporting that C57S SOD1 retained a significant amount of activity.

The RNA-binding protein EWS is a multifunctional protein with roles in the regulation of transcription and RNA splicing. It is one of the FET (FUS, EWS and TAF15) family of RNA binding proteins that contain an intrinsically disordered, low-complexity N-terminal domain. The FET family proteins are prone to chromosomal translocations, often fusing their low-complexity domain with a transcription factor derived DNA-binding domain, that are oncogenic drivers in several leukemias and sarcomas. The fusion protein disrupts the normal function of cells through non-canonical DNA binding and alteration of normal transcriptional programs. However, the exact mechanism for how the intrinsically disordered domain contributes to aberrant DNA binding and abnormal transcription is unknown. The purification and 1H, 13C, and 15N backbone resonance assignments of the amino terminal domain comprising 264 residues of EWS is described. This segment is common to all known EWS-fusions that are the hallmark of the pediatric cancer Ewing sarcoma. This domain is intrinsically disordered and features significant sequence degeneracy resulting in spectra with poor chemical shift dispersion. To alleviate this problem, the domain was divided into three overlapping fragments, reducing the complexity of the spectra and enabling almost complete backbone resonance assignment of the full domain. These solution NMR chemical shift assignments represent the first steps towards understanding, at atomic resolution, how the low-complexity domain of EWS contributes to the aberrant functions of its oncogenic fusion proteins. [ABSTRACT FROM AUTHOR]

Research has been conducted on the copper-zinc superoxide dismutase. The characterization of the truncated and full-length forms of the yeast copper chaperone for SOD has been carried out.

Force field analysis as a research tool is analyzed and discussed. Assessment in organizational change must consider three areas. The tool used must incorporate level analysis, diverse types of information from a plethora of variables and must account for dynamics of stability and change. A force field is constructed by choosing a change goal, actors of change, range of forces available and valuation of the forces according to their effectivity to change. The force must be potent and amenable to the actors.

The lack of correspondence between traditional economic development measures, such as GNP per capita, and human welfare measures, such as the PQLI, has been well documented in the literature. We devised and analyzed an economic development-welfare disparity measure, and found considerable geographic variability, with actual levels of human welfare much less than expected in many Middle Eastern and African countries, given the level of economic development. Exploratory correlation and regression analysis revealed that inequalities in the distribution of economic power and governmental expenditures contributed to the geographic variability. More importantly, each region improved its standing on the development-welfare disparity measure when relevant factors were controlled via multivariate regression. Key Words: economic development, human welfare, disparity measure, geographic variability.

Currently there is only one method of treatment for human schistosomiasis, the drug praziquantel. Strong selective pressure has caused a serious concern for a rise in resistance to praziquantel leading to the necessity for additional pharmaceuticals, with a distinctly different mechanism of action, to be used in combination therapy with praziquantel. Previous treatment of Schistosoma mansoni included the use of oxamniquine (OXA), a prodrug that is enzymatically activated in S. mansoni but is ineffective against S. haematobium and S. japonicum. The oxamniquine activating enzyme was identified as a S. mansoni sulfotransferase (SmSULT-OR). Structural data have allowed for directed drug development in reengineering oxamniquine to be effective against S. haematobium and S. japonicum. Guided by data from X-ray crystallographic studies and Schistosoma worm killing assays on oxamniquine, our structure-based drug design approach produced a robust SAR program that tested over 300 derivatives and identified several new lead compounds with effective worm killing in vitro. Previous studies resulted in the discovery of compound CIDD-0066790, which demonstrated broad-species activity in killing of schistosome species. As these compounds are racemic mixtures, we tested and demonstrate that the R enantiomer CIDD-007229 kills S. mansoni, S. haematobium and S. japonicum better than the parent drug (CIDD-0066790). The search for derivatives that kill better than CIDD-0066790 has resulted in a derivative (CIDD- 149830) that kills 100% of S. mansoni, S. haematobium and S. japonicum adult worms within 7 days. We hypothesize that the difference in activation and thus killing by the derivatives is due to the ability of the derivative to fit in the binding pocket of each sulfotransferase (SmSULT-OR, ShSULT-OR, SjSULT-OR) and to be efficiently sulfated. The purpose of this research is to develop a second drug to be used in conjunction with praziquantel to treat the major human species of Schistosoma. Collectively, our findings show that CIDD-00149830 and CIDD-0072229 are promising novel drugs for the treatment of human schistosomiasis and strongly support further development and in vivo testing. Author summary: Schistosomiasis affects more than 229 million people in 78 countries of the world. The main treatment is Mass Drug Administration with praziquantel. With donations to the World Health Organization, approximately 250 million tablets of praziquantel are being administered in sub-Saharan Africa where about 90% of the cases of schistosomiasis occur. The concern with a monotherapy is the development of drug resistance. The need for new drugs with a different mode of action to be used in combination with praziquantel is great. In this regard, we have taken oxamniquine, a drug that was previously used to treat Schistosoma mansoni but was ineffective against S. haematobium and S. japonicum, and determined the enzyme responsible for activation of oxamniquine as a sulfotransferase. With this knowledge and the sulfotransferase crystal structure, we were able to determine the mode of action of the drug and develop an iterative approach of soaking oxamniquine derivatives into sulfotransferase crystals, determining structure function relationships, synthesizing new derivatives and testing them in an in vitro killing assay. The most effective derivatives are soaked into new crystals and the process repeated. We have identified two derivatives, CIDD-0072229 and CIDD-149830 that will kill S. haematobium and S. japonicum in addition to S. mansoni. CIDD-149830 will kill 100% of the worms of all three species within 7 days. [ABSTRACT FROM AUTHOR]

Molecular beams have been used to search for evidence for a weakly bound molecular precursor in (the interaction of O[SUB2] with Al(111). The experiments are consistent with a precursor whose binding energy is smaller than 0.1 eV. The total reflectivity as a function of incidence angle shows a pronounced dip at 25° for E[SUBtrans] between 90 and 300 meV. This feature corroborates an earlier observation by &Oml;sterlund et al. in sticking measurements. Modeling using a reduced dimensionality potential energy surface shows a similar behavior which is caused by steering into a shallow molecular adsorption well located at the same site in the unit cell as the maximum in the barrier towards dissociative adsorption. This effect is not observed if the molecular adsorption well is located at the same site as the minimum energy pathway to dissociative adsorption. [ABSTRACT FROM AUTHOR]

Experiments, for the electron stimulated desorption of CO molecules from Ru(0001) [Wurm et al., Phys. Rev. Lett. 74, 2591 (1995)] are rationalized with the help of quantum wave packet methods using a bimodal two-state model. Besides a vibrational population inversion for the desorbing molecule we also find a small amount of dissociation, and an experimentally observed positive correlation between vibrational state and kinetic energy of the desorbing molecules. The role of vibrational excitation of the initial state is discussed. Classical trajectory calculations are found to be in good agreement with quantum dynamics thus allowing for a systematic exploration of the sensitivity of the results on details of the potential energy surfaces. [ABSTRACT FROM AUTHOR]

The characteristics, as well as the structural and biophysical properties of His46Arg (H46R) and His48Gln (H48Q), two pathogenic superoxide dismutase (SOD1) mutations are discussed. These variants are shown to exhibit an ablated copper-binding site and are also able to form stable heterocomplexes with copper chaperone for SOD1.

The results of classical trajectory (CT) calculations on the sticking of protons to the basal plane (0001) face of crystalline ice, for normal incidence at a surface temperature of 80 K are presented. The calculation is performed for moderately low incidence energies (E(sub i)) ranging from 0.05 to 4.0 eV.

Do mutations required for adaptation occur de novo, or are they segregating within populations as standing genetic variation? This question is key to understanding adaptive change in nature, and has important practical consequences for the evolution of drug resistance. We provide evidence that alleles conferring resistance to oxamniquine (OXA), an antischistosomal drug, are widespread in natural parasite populations under minimal drug pressure and predate OXA deployment. OXA has been used since the 1970s to treat Schistosoma mansoni infections in the New World where S. mansoni established during the slave trade. Recessive loss-of-function mutations within a parasite sulfotransferase (SmSULT-OR) underlie resistance, and several verified resistance mutations, including a deletion (p.E142del), have been identified in the New World. Here we investigate sequence variation in SmSULT-OR in S. mansoni from the Old World, where OXA has seen minimal usage. We sequenced exomes of 204 S. mansoni parasites from West Africa, East Africa and the Middle East, and scored variants in SmSULT-OR and flanking regions. We identified 39 non-synonymous SNPs, 4 deletions, 1 duplication and 1 premature stop codon in the SmSULT-OR coding sequence, including one confirmed resistance deletion (p.E142del). We expressed recombinant proteins and used an in vitro OXA activation assay to functionally validate the OXA-resistance phenotype for four predicted OXA-resistance mutations. Three aspects of the data are of particular interest: (i) segregating OXA-resistance alleles are widespread in Old World populations (4.29–14.91% frequency), despite minimal OXA usage, (ii) two OXA-resistance mutations (p.W120R, p.N171IfsX28) are particularly common (>5%) in East African and Middle-Eastern populations, (iii) the p.E142del allele has identical flanking SNPs in both West Africa and Puerto Rico, suggesting that parasites bearing this allele colonized the New World during the slave trade and therefore predate OXA deployment. We conclude that standing variation for OXA resistance is widespread in S. mansoni. It has been argued that drug resistance is unlikely to spread rapidly in helminth parasites infecting humans. This is based, at least in part, on the premise that resistance mutations are rare or absent within populations prior to treatment, and take a long time to reach appreciable frequencies because helminth parasite generation time is long. This argument is critically dependent on the starting frequency of resistance alleles–if high levels of "standing variation" for resistance are present prior to deployment of treatment, resistance may spread rapidly. We examined frequencies of oxamniquine resistance alleles present in Schistosoma mansoni from Africa and the Middle East where oxamniquine has seen minimal use. We found that oxamniquine resistance alleles are widespread in the Old World, ranging from 4.29% in the Middle East to 14.91% in East African parasite populations. Furthermore, we show that resistance alleles from West African and the Caribbean schistosomes share a common origin, suggesting that these alleles travelled to the New World with S. mansoni during the transatlantic slave trade. Together, these results demonstrate extensive standing variation for oxamniquine resistance. Our results have important implications for both drug treatment policies and drug development efforts, and demonstrate the power of molecular surveillance approaches for guiding helminth control. [ABSTRACT FROM AUTHOR]

A two-dimensional, two-state model is used to model the UV-laser-induced photodesorption dynamics of NH3 and ND3 from Cu(111) by solving the nuclear time-dependent Schrödinger equation. By projecting the asymptotic wave functions on the asymptotic (‘‘umbrella’’) eigenstates of NH3/ND3, we find that the molecules leave the surface vibrationally hot, in agreement with experimental data. Within individual asymptotic tunneling doublets, however, the desorbates are clearly non-Boltzmann with molecules of ‘‘gerade’’ symmetry desorbing with increased probability. Our study correlates this parity selection with details of the electronic ground state potential energy surface. An experimentally observed strong isotope effect in the desorption yields for the different isotopomers is traced back mainly to differences between the vibrational frequencies of the ‘‘umbrella’’ mode, in accord with earlier, classical models. Additionally, small tunneling and moderate zero-point contributions are observed. Finally, the possibility of bond and isotope selective photochemistry at surfaces, based on a two-photon IR+UV strategy is demonstrated. © 1995 American Institute of Physics. [ABSTRACT FROM AUTHOR]

The dynamics of activated associative desorption is discussed with particular reference to the system H2–Cu and to the partitioning of the energy released among the various product degrees of freedom. It is argued that a simple theory based on transition-state concepts should hold for this system because the potential energy surface (PES) divides naturally into reactant and product regions, separated by a ‘‘seam’’ or ‘‘ridge’’ at which it is reasonable to assume a thermal distribution of desorbing trajectories. Using a PES constructed in accordance with available electronic structure calculations we consider the angular distributions and translational, vibrational, and rotational energy distributions of the desorbing molecules. It is shown that, whereas the rotational energy reflects the surface temperature, the vibrational energy is markedly enhanced because the energetically low-lying regions of the ridge in the PES correspond to an H–H bond distance that is distended as compared with the gas-phase equilibrium separation. The enhancement is found to be a strong function of the surface temperature. The translational energy, however, is found to be only very weakly dependent on the temperature. These results are discussed in connection with available data. [ABSTRACT FROM AUTHOR]

A quantum wave packet calculation for the activated dissociative adsorption of H2 is presented. Restricting the motion of the molecule to lie within a plane normal to the surface we have treated all four molecular degrees of freedom exactly. We compare results obtained using two-, three-, and four-dimensional simulations on the same potential and show that by restricting the molecular orientation, important dynamical effects are lost. The potential employed in the calculations has been obtained using the effective medium approximation. In the simulations it has been possible to treat dissociation, rotations and diffraction on an equal footing. By including a rotational degree of freedom, it is seen that strong orientational effects occur near to the transition state and result in an anisotropic selectivity in the dissociation. By examining the state-to-state scattering probabilities, it is possible to use the nonreacting (scattered) fraction to provide information on the reactive potential energy surface. [ABSTRACT FROM AUTHOR]

Background: For over two decades, a racemic mixture of oxamniquine (OXA) was administered to patients infected by Schistosoma mansoni, but whether one or both enantiomers exert antischistosomal activity was unknown. Recently, a ~30 kDa . ansoni foransferase (SmSULT) was identified as the target of OXA action. Methodology/Principal Findings: Here, we separate the OXA enantiomers using chromatographic methods and assign their optical activities as dextrorotary [(+)-OXA] or levorotary [(-)-OXA]. Crystal structures of the parasite enzyme in complex with optically pure (+)-OXA and (-)-OXA) reveal their absolute configurations as S- and R-, respectively. When tested in vitro, S-OXA demonstrated the bulk of schistosomicidal activity, while R-OXA had antischistosomal effects when present at relatively high concentrations. Crystal structures R-OXA•SmSULT and S-OXA•SmSULT complexes reveal similarities in the modes of OXA binding, but only the S-OXA enantiomer is observed in the structure of the enzyme exposed to racemic OXA. Conclusions/Significance: Together the data suggest the higher schistosomicidal activity of S-OXA is correlated with its ability to outcompete R-OXA binding the sulfotransferase active site. These findings have important implications for the design, syntheses, and dosing of new OXA-based antischistosomal compounds. [ABSTRACT FROM AUTHOR]

Abstract. Model studies are presented, each of which employs a different approach to solving the problem of nonadiabatic dynamics occurring at a solid surface. The jumping wave packet-type approach involving dynamics on two potential energy surfaces punctuated by Franck-Condon transitions was applied to the dynamics of CO desorbed from Ru following energetic electron bombardment. Classical dynamics was also employed in this system to gain a more detailed understanding of the factors important to the final molecular state distribution. To study charge transfer from an alkali-halide surface to a scattering atom, we have used full multi-surface quantum dynamics. A simple, but effective, analysis method was used to make a more detailed connection between the potential energy surfaces and the dynamics. To study the fate of the transferred electron and to model how this depends on substrate and projectile species, we have used a four-dimensional wave packet implementation in which two of the dimensions explicitly account for the electron dynamics. Finally, we consider the famous electron-hole pair excitation problem, from a density functional theory perspective. Spin nonadiabaticity is found to be a new important feature in gas-metal surface interactions. [ABSTRACT FROM AUTHOR]

No abstract available for this article. [ABSTRACT FROM PUBLISHER]

No abstract available for this article. [ABSTRACT FROM PUBLISHER]

No abstract available for this article. [ABSTRACT FROM PUBLISHER]

Three major types of organizational change are identified (alterations in behavior, technology, and structure), and the respective impact of each is explored. The difficulties in assessing the significance of a change idea are noted, and some criteria are suggested by which such an assessment can be made (eg., the number of organizational elements affected by the change). The paper concludes by noting practice implications stemming from an understanding of the types of change and their significance for those participants who have limited formal power. [ABSTRACT FROM PUBLISHER]