Allopurinol complexes with first row transition metal perchlorates

Summary Complexes of allopurinol (apH) with Fe^III and several 3d metal(II) (e.g. Fe, Co, Ni and Cu) perchlorates were prepared. The solid complexes isolated included two monomeric hexacoordinated adducts of the type [Fe(apH)₃-(OClO₃) (OH₂)₂]ClO₄ and [Fe(apH)₃(OClO₃)₂(OH₂)]ClO₄, involving N(8)-bound neutral apH ligands, and polymeric Co, Ni or Cu complexes containing both neutral apH and monoanionic ap^- ligands. The latter three complexes involved both N(8)-bound terminal apH and N(1), N(8)- or N(1), N(9)-bound bridging ap^- ligands, and were of the following types: [(apH)₂Cu(ap)] _n (ClO₄) _n , tetrahedral; [(apH)(H₂O)(OClO₃)Co(ap)] _n , pentacoordinated; and [(apH)₂(H₂O)(OClO₃)Ni(ap)] _n , hexacoordinated.Presented in part at the 203rd. American Chemical Society National Meeting; see Ref. 1.     

Prediction of the orientations of adsorbed protein using an empirical energy function with implicit solvation

When simulating protein adsorption behavior, decisions must first be made regarding how the protein should be oriented on the surface. To address this problem, we have developed a molecular simulation program that combines an empirical adsorption free energy function with an efficient configurational search method to calculate orientation-dependent adsorption free energies between proteins and functionalized surfaces. The configuration space is searched systematically using a quaternion rotation technique, and the adsorption free energy is evaluated using an empirical energy function with an efficient grid-based calculational method. In this paper, the developed method is applied to analyze the preferred orientations of a model protein, lysozyme, on various functionalized alkanethiol self-assembled monolayer (SAM) surfaces by the generation of contour graphs that relate adsorption free energy to adsorbed orientation, and the results are compared with experimental observations. As anticipated, the adsorbed orientation of lysozyme is predicted to be dependent on the discrete organization of the functional groups presented by the surface. Lysozyme, which is a positively charged protein, is predicted to adsorb on its 'side' on both hydrophobic and negatively charged surfaces. On surfaces with discrete positively charged sites, attractive interaction energies can also be obtained due to the presence of discrete local negative charges present on the lysozyme surface. In this case, 'end-on' orientations are preferred. Additionally, SAM surface models with mixed functionality suggest that the interactions between lysozyme and surfaces could be greatly enhanced if individual surface functional groups are able to access the catalytic cleft region of lysozyme, similar to ligand-receptor interactions. The contour graphs generated by this method can be used to identify low-energy orientations that can then be used as starting points for further simulations to investigate conformational changes induced in protein structure following initial adsorption.     

A Remark on Real Parameter Global Bifurcation

We study the nonlinear eigenvalue problem F(x,) = L()x +R(x,) = 0 where F : X × R X with X a Hilbert space. IfL() is a polynomial in , then it is shown that 0> 0 is a global bifurcation point of the eigenvalue problem provided astandard transversality condition is satisfied, the dimension of the nullspace of L(0) is an odd number and L() is composed of asequence of positive operators on the finite dimensional null space ofL(0).     

Aberration-correction results from a segmented microelectromechanical deformable mirror and a refractive lenslet array

Quadratic aberration is successfully corrected with a segmented microelectromechanical deformable mirror in conjunction with a refractive lenslet array. Use of the lenslet array greatly improves the effective fill factor of the correcting element. Experimental results show correction approaching the diffraction limit for an extreme spherical aberration.     

Separation of Bioactive Prostaglandins and their Metabolites by Reversed-Phase Thin-Layer Chromatography

JPC – Journal of Planar Chromatography – Modern TLC - Prostaglandins are biological lipid mediators that control a variety of physiological and pathophysiological processes. They...     

Evaluating use of ferricyanide-mediated respiration bioassays to quantify stimulatory and inhibitory effects on Escherichia coli populations

A number of recent studies have utilised ferricyanide as a respiratory mediator for microbial-based assays for determining water quality parameters such as biochemical oxygen demand (BOD) and toxicity. The majority of assays published to date obtain a result by determining the difference in ferrocyanide accumulation between a test sample and one or more control samples. However, a validation of the relationship between ferrocyanide accumulation and standard measures of cell density or viability has not yet been performed. To this end, a rapid microbially catalysed ferricyanide-mediated respiration (FM-RES) assay was compared with standard plate count (SPC) and spectrophotometer (OD₆₀₀) measurements on a growing batch culture of Escherichia coli. Good agreement was observed between all techniques, with predictable deviations noted in different phases of the growth curves. Standardised FM-RES assays showed excellent correlations with the SPC method under controlled conditions, indicating that short-term changes in microbial activity are due to a change in per-cell respiration, rather than changes in cell numbers. The FM-RES assay was then used to observe the changes in the respiration of E. coli induced by the addition of a glucose-glutamic acid (GGA) mixture, 3,5-dichlorophenol (3,5-DCP) and Ag⁺ in various combinations and concentrations. Stimulation of respiration was pronounced in the presence of GGA while both 3,5-DCP and, in particular, Ag⁺ demonstrated inhibitory respiratory effects. The results highlight the validity and suitability of ferricyanide-mediated respiration bioassays, with appropriate modification, to monitor either stimulatory effects on microbial populations, such as occurs with BOD, or inhibitory effects, such as occurs with toxicity assays.     

Structure-based design of supercharged, highly thermoresistant antibodies

Mutation of surface residues to charged amino acids increases resistance to aggregation and can enable reversible unfolding. We have developed a protocol using the Rosetta computational design package that "supercharges" proteins while considering the energetic implications of each mutation. Using?a homology model, a single-chain variable fragment antibody was designed that has a markedly enhanced resistance to thermal inactivation and displays an unanticipated ≈30-fold improvement in affinity. Such supercharged antibodies should prove useful for assays in resource-limited settings and for developing reagents with improved shelf lives.     

EELV secondary payload adapter (ESPA) static qualification tests,part 4 of 4

Experimental Techniques -