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Michael W Crowder - One of the best experts on this subject based on the ideXlab platform.

  • spectroscopic studies on cobalt ii substituted metallo β lactamase imis from aeromonas veronii bv sobria
    Biochemistry, 2005
    Co-Authors: Patrick A Crawford, Narayan Sharma, Kewu Yang, Brian Bennett, Michael W Crowder
    Abstract:

    In an effort to probe the structure of a group Bb metallo-beta-lactamase, Co(II)-substituted ImiS was prepared and characterized by electronic absorption, NMR, and EPR spectroscopies. ImiS containing 1 equiv of Co(II) (Co(II)(1)-ImiS) was shown to be catalytically active. Electronic absorption studies of Co(II)(1)-ImiS revealed the presence of two distinct features: (1) an intense sulfur to Co(II) ligand to metal charge transfer band and (2) less intense, Co(II) ligand field transitions that suggest 4-coordinate Co(II) in Co(II)(1)-ImiS. (1)H NMR studies of Co(II)(1)-ImiS suggest that one histidine, one aspartic acid, and one cysteine coordinate the metal ion in Co(II)(1)-ImiS. The addition of a second Co(II) to Co(II)(1)-ImiS did not result in any additional solvent-exchangeable NMR resonances, strongly suggesting that the second Co(II) does not bind to a site with histidine ligands. EPR studies reveal that the metal ion in Co(II)(1)-ImiS is 4-coordinate and that the second Co(II) is 5/6 coordinate. Taken together, these data indicate that the catalytic site in ImiS is the consensus Zn(2) site, in which Co(II) (and by extrapolation Zn(II)) is 4-coordinate and bound by Cys221, His263, Asp120, and probably one solvent water molecule. These studies also show that the second, inhibitory metal ion does not bind to the consensus Zn(1) site and that the metal ion binds at a site significantly removed from the active site. These results give the first structural information on metallo-beta-lactamase ImiS and suggest that the second metal binding site in ImiS may be targeted for inhibitors.

  • over expression purification and characterization of metallo beta lactamase imis from aeromonas veronii bv sobria
    Protein Expression and Purification, 2004
    Co-Authors: Patrick A Crawford, Narayan Sharma, Sowmya Chandrasekar, Tara K Sigdel, Timothy R Walsh, James Spencer, Michael W Crowder
    Abstract:

    The gene from Aeromonas veronii bv. sobria encoding the metallo-beta-lactamase ImiS was subcloned into pET-26b, and ImiS was over-expressed in BL21(DE3) Escherichia coli and purified using SP-Sepharose chromatography. This protocol yielded over 5 mg of ImiS per liter of growth culture under optimum conditions. The biochemical properties of recombinant ImiS were compared with those of native ImiS. Recombinant and native ImiS have the same N-terminus of A-G-M-S-L, and CD spectroscopy was used to show that the enzymes have similar secondary structures. Gel filtration chromatography revealed that both enzymes exist as monomers in solution. MALDI-TOF mass spectra showed that the enzymes have a molecular mass of 25,247 Da, and metal analyses demonstrated that both as-isolated enzymes bind ca. 0.7 mol of Zn(II). Metal titrations demonstrate that the maximum activity of recombinant ImiS occurs when the enzyme binds one equivalent of zinc. Steady-state kinetic studies reveal that recombinant ImiS is a carbapenemase like native ImiS and that the recombinant enzyme exhibits similar kcat and K(m) values for the substrates tested, as compared to the native enzyme. This over-expression protocol now allows for detailed spectroscopic and mechanistic studies on ImiS as well as site-directed mutants of ImiS to be prepared for future structure/function studies.

M. Darouach - One of the best experts on this subject based on the ideXlab platform.

  • further enhancement on robust h_ infty control design for discrete time singular systems
    IEEE Transactions on Automatic Control, 2014
    Co-Authors: Mohammed Chadli, M. Darouach
    Abstract:

    This note deals with the robust H∞ control design for uncertain discrete-time singular systems. Necessary and sufficient conditions for the admissibility for these systems are formulated in strict linear matrix inequalities (LMIs) formulation. Then both state feedback and static output feedback controllers are studied and robust necessary and sufficient design conditions are expressed in terms of strict bilinear matrix inequalities (BMIs). Robust H∞ controllers are designed for uncertain singular systems including uncertainties on matrix E. LMI design conditions are also proposed. An illustrative example is provided to show the effectiveness of the proposed approach.

  • Linear functional observers for systems with delays in State variables: the discrete-time case
    IEEE Transactions on Automatic Control, 2005
    Co-Authors: M. Darouach
    Abstract:

    This note extends to the discrete-time case the design of linear functional state observers, recently developed for continuous-time delay systems. Sufficient conditions for the stability dependent of delays and stability independent of delays are derived using linear and bilinear matrix inequalities [(LMIs) and (BMIs)] formulations.

Patrick A Crawford - One of the best experts on this subject based on the ideXlab platform.

  • spectroscopic studies on cobalt ii substituted metallo β lactamase imis from aeromonas veronii bv sobria
    Biochemistry, 2005
    Co-Authors: Patrick A Crawford, Narayan Sharma, Kewu Yang, Brian Bennett, Michael W Crowder
    Abstract:

    In an effort to probe the structure of a group Bb metallo-beta-lactamase, Co(II)-substituted ImiS was prepared and characterized by electronic absorption, NMR, and EPR spectroscopies. ImiS containing 1 equiv of Co(II) (Co(II)(1)-ImiS) was shown to be catalytically active. Electronic absorption studies of Co(II)(1)-ImiS revealed the presence of two distinct features: (1) an intense sulfur to Co(II) ligand to metal charge transfer band and (2) less intense, Co(II) ligand field transitions that suggest 4-coordinate Co(II) in Co(II)(1)-ImiS. (1)H NMR studies of Co(II)(1)-ImiS suggest that one histidine, one aspartic acid, and one cysteine coordinate the metal ion in Co(II)(1)-ImiS. The addition of a second Co(II) to Co(II)(1)-ImiS did not result in any additional solvent-exchangeable NMR resonances, strongly suggesting that the second Co(II) does not bind to a site with histidine ligands. EPR studies reveal that the metal ion in Co(II)(1)-ImiS is 4-coordinate and that the second Co(II) is 5/6 coordinate. Taken together, these data indicate that the catalytic site in ImiS is the consensus Zn(2) site, in which Co(II) (and by extrapolation Zn(II)) is 4-coordinate and bound by Cys221, His263, Asp120, and probably one solvent water molecule. These studies also show that the second, inhibitory metal ion does not bind to the consensus Zn(1) site and that the metal ion binds at a site significantly removed from the active site. These results give the first structural information on metallo-beta-lactamase ImiS and suggest that the second metal binding site in ImiS may be targeted for inhibitors.

  • over expression purification and characterization of metallo beta lactamase imis from aeromonas veronii bv sobria
    Protein Expression and Purification, 2004
    Co-Authors: Patrick A Crawford, Narayan Sharma, Sowmya Chandrasekar, Tara K Sigdel, Timothy R Walsh, James Spencer, Michael W Crowder
    Abstract:

    The gene from Aeromonas veronii bv. sobria encoding the metallo-beta-lactamase ImiS was subcloned into pET-26b, and ImiS was over-expressed in BL21(DE3) Escherichia coli and purified using SP-Sepharose chromatography. This protocol yielded over 5 mg of ImiS per liter of growth culture under optimum conditions. The biochemical properties of recombinant ImiS were compared with those of native ImiS. Recombinant and native ImiS have the same N-terminus of A-G-M-S-L, and CD spectroscopy was used to show that the enzymes have similar secondary structures. Gel filtration chromatography revealed that both enzymes exist as monomers in solution. MALDI-TOF mass spectra showed that the enzymes have a molecular mass of 25,247 Da, and metal analyses demonstrated that both as-isolated enzymes bind ca. 0.7 mol of Zn(II). Metal titrations demonstrate that the maximum activity of recombinant ImiS occurs when the enzyme binds one equivalent of zinc. Steady-state kinetic studies reveal that recombinant ImiS is a carbapenemase like native ImiS and that the recombinant enzyme exhibits similar kcat and K(m) values for the substrates tested, as compared to the native enzyme. This over-expression protocol now allows for detailed spectroscopic and mechanistic studies on ImiS as well as site-directed mutants of ImiS to be prepared for future structure/function studies.

Bohong Wang - One of the best experts on this subject based on the ideXlab platform.

François Bergeron - One of the best experts on this subject based on the ideXlab platform.

  • project management information systems an empirical study of their impact on project managers and project success
    International Journal of Project Management, 2008
    Co-Authors: Louis Raymond, François Bergeron
    Abstract:

    Project management information systems (Pmis) usually acquired by organizations as software packages are meant to provide managers with the decision-making support needed in planning, organizing, and controlling projects. However, the actual contribution of Pmis to project success or performance is still unknown. The purpose of this study is to empirically assess the quality of the Pmis presently used in organizations and to examine their impact on project managers and project performance, based on a Pmis success model. This model is composed of five constructs: the quality of the Pmis, the quality of the Pmis information output, the use of the Pmis, the individual impacts of the Pmis and the impacts of the Pmis on project success. Analysis of questionnaire data obtained from 39 project managers confirms the significant contribution of Pmis to successful project management. Improvements in effectiveness and efficiency in managerial tasks were observed here in terms of better project planning, scheduling, monitoring, and control. Improvements were also observed in terms of timelier decision-making. Advantages obtained from Pmis use are not limited to individual performance but also include project performance. These systems were found to have direct impacts on project success, as they contribute to improving budget control and meeting project deadlines as well as fulfilling technical specifications.