Predicted binding rate of new cephalosporin antibiotics by a 3D-QSAR method: a new approach

Abstract  

Antibiotics are chemotherapeutic agents with activity against microorganisms, for example bacteria, fungi, or protozoa, used for the treatment of many types of diseases. Binding of antibiotics to serum proteins in human plasma is a major determinant of their pharmacodynamic and pharmacokinetic behavior and, consequently, can affect their systemic distribution in the body. Here, the predicted binding rates of ceftazidime and 13 other pharmacological agents classified as antibiotics to plasma proteins (percentage fraction bound; PFB) were evaluated by use of 3D-QSAR models. We attempted to establish the contribution of hydrogen bond donor/acceptor and hydrophobic properties supplied by electrostatic fields to the PFB. Significant cross-validated correlation q ² (0.5–0.7) and the fitted correlation r ² (0.7–0.97) coefficients revealed that these models have reasonable power to predict the design 19 new antibiotics using ceftazidime as template, these compounds being our suggestion for further studies.     

Nuclear magnetic resonance of intermetallic compounds Gd2Ni17−xAlx

²⁷Al Knight shifts vs temperature and magnetic susceptibility for the intermetallic compounds Gd₂Ni_17?xAl_x (x = 17; 16.2; 16; 15) are presented. The results are discussed in terms of the uniform polarization model fo the conduction electrons by the 4f and 3d spins localized on the Gd and Ni ions. The phenomenological exchange constants J_sf and J_sd range between ?1.80×10^?3 and 1.19×10^?3 eV and ?0.63×10^?3 and ?0.52×10^?3 eV, respectively.     

Spin waves and electronic interactions in La2CuO4

The magnetic excitations of the square-lattice spin-1/2 antiferromagnet and high- T(c) parent compound La2CuO4 are determined using high-resolution inelastic neutron scattering. Sharp spin waves with absolute intensities in agreement with theory including quantum corrections are found throughout the Brillouin zone. The observed dispersion relation shows evidence for substantial interactions beyond the nearest-neighbor Heisenberg term which can be understood in terms of a cyclic or ring exchange due to the strong hybridization path around the Cu4O4 square plaquettes.     

Interplay between composition,structural dynamics and thermodynamic data in amino acid nitrates

Journal of Thermal Analysis and Calorimetry - A systematic thermodynamic study has been performed for a series of nitrates having cations derived from the α-amino acids glycine (Gly),...     

Star-shaped molecule of MnII4O6 core with an St=10 high-spin state. A theoretical and experimental study with XPS, XMCD, and other magnetic methods

We report a comprehensive study of the electronic and magnetic properties of a star-shaped molecule comprising a MnII4O6 core. One feature of this compound is weak magnetic coupling constants compared to other similar polyoxo compounds. This leads to complicated low-lying magnetic states in which the ground state is not well separated from the upper-lying states, yielding a high-spin molecule with a giant magnetic moment of up to 20 microB/formula unit. We apply X-ray diffraction and magnetometry as well as other X-ray spectroscopic techniques, namely, X-ray photoelectron spectroscopy, X-ray magnetic circular dichroism, and X-ray emission spectroscopy. We compare our experimental results with ab initio electronic band structure calculations as well as the localized electronic structure around the Mn2+ ions with charge-transfer multiplet calculations.     

X-ray photoelectron spectroscopy and magnetism of Mn1−xAlxNi alloys

X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), magnetization and magnetic susceptibility of Mn_1−xAl_xNi alloys are reported. A change in the crystallographic structure takes place around x=0.4 from CuAuI to CsCl (B2) structure type. For x0.5 a mixed B2+L2₁ state exists which incorporates antiferromagnetic (B2) and ferromagnetic (L2₁) parts. A direct evidence for the existence of local moments on Mn sites in Mn_1-xAl_xNi alloys is given by the exchange splitting of XPS Mn 3s and Mn 2p3/2 core levels. The gradual filling of the Ni 3d band as the Al concentration increases can be explained by the hybridization of the Ni 3d band and Al 3sp states.     

Spin waves and revised crystal structure of honeycomb iridate Na2IrO3

We report inelastic neutron scattering measurements on Na2IrO3, a candidate for the Kitaev spin model on the honeycomb lattice. We observe spin-wave excitations below 5 meV with a dispersion that can be accounted for by including substantial further-neighbor exchanges that stabilize zigzag magnetic order. The onset of long-range magnetic order below T(N)=15.3 K is confirmed via the observation of oscillations in zero-field muon-spin rotation experiments. Combining single-crystal diffraction and density functional calculations we propose a revised crystal structure model with significant departures from the ideal 90° Ir-O-Ir bonds required for dominant Kitaev exchange.     

de Haas-van Alphen study of the Fermi surfaces of superconducting LiFeP and LiFeAs

We report a de Haas-van Alphen oscillation study of the 111 iron pnictide superconductors LiFeAs with T(c) ≈ 18 K and LiFeP with T(c) ≈ 5 K. We find that for both compounds the Fermi surface topology is in good agreement with density functional band-structure calculations and has almost nested electron and hole bands. The effective masses generally show significant enhancement, up to ~3 for LiFeP and ~5 for LiFeAs. However, one hole Fermi surface in LiFeP shows a very small enhancement, as compared with its other sheets. This difference probably results from k-dependent coupling to spin fluctuations and may be the origin of the different nodal and nodeless superconducting gap structures in LiFeP and LiFeAs, respectively.