Substitution and derivatization reactions of a water soluble iron(II) complex containing a self-assembled tetradentate phosphine ligand

Facile substitution reactions of the two water ligands in the hydrophilic tetradentate phosphine complex cis-[Fe{(HOCH2)P{CH2N(CH2P(CH2OH)2)CH2}2P(CH2OH)}(H2O)2](SO4) (abbreviated to [Fe(L1)(H2O)2](SO4), 1) take place upon addition of Cl-, NCS-, N3(-), CO3(2-) and CO to give [Fe(L1)X2] (2, X = Cl; 4, X = NCS; 5, X=N3), [Fe(L1)(kappa2-O(2)CO)], 6 and [Fe(L1)(CO)2](SO4), 7. The unsymmetrical mono-substituted intermediates [Fe(L1)(H2O)(CO)](SO(4)) and [Fe(L(1))(CO)(kappa(1)-OSO(3))] (8/9) have been identified spectroscopically en-route to 7. Treatment of 1 with acetic anhydride affords the acylated derivative [Fe{(AcOCH2)P{CH2N(CH2P(CH2OAc)2)CH2}2P(CH2OAc)}(kappa2-O(2)SO2)] (abbreviated to [Fe(L2)(kappa2-O(2)SO2)], 10), which has increased solubility over 1 in both organic solvents and water. Treatment of 1 with glycine does not lead to functionalisation of L1, but substitution of the aqua ligands occurs to form [Fe(L(1))(NH(2)CH(2)CO(2)-kappa(2)N,O)](HSO(4)), 11. Compound 10 reacts with chloride to form [Fe(L(2))Cl(2)] 12, and 12 reacts with CO in the presence of NaBPh4 to form [Fe(L2)Cl(CO)](BPh4) 13b. Both of the chlorides in 12 are substituted on reaction with NCS- and N3(-) to form [Fe(L2)(NCS)2] 14 and [Fe(L2)(N3)2] 15, respectively. Complexes 2.H2O, 4.2H2O, 5.0.812H2O, 6.1.7H2O, 7.H2O, 10.1.3CH3C(O)CH3, 12 and 15.0.5H2O have all been crystallographically characterised.     

High-density targeting of a viral multifunctional nanoplatform to a pathogenic, biofilm-forming bacterium

Nanomedicine directed at diagnosis and treatment of infections can benefit from innovations that have substantially increased the variety of available multifunctional nanoplatforms. Here, we targeted a spherical, icosahedral viral nanoplatform to a pathogenic, biofilm-forming bacterium, Staphylococcus aureus. Density of binding mediated through specific protein-ligand interactions exceeded the density expected for a planar, hexagonally close-packed array. A multifunctionalized viral protein cage was used to load imaging agents (fluorophore and MRI contrast agent) onto cells. The fluorescence-imaging capability allowed for direct observation of penetration of the nanoplatform into an S. aureus biofilm. These results demonstrate that multifunctional nanoplatforms based on protein cage architectures have significant potential as tools for both diagnosis and targeted treatment of recalcitrant bacterial infections.     

MSE with mass defect filtering for in vitro and in vivo metabolite identification

Metabolite identification studies involve the detection and structural characterization of the biotransformation products of drug candidates. These experiments are necessary throughout the drug discovery and development process. The use of high-resolution chromatography and high-resolution mass spectrometry together with data processing using mass defect filtering is described for in vitro and in vivo metabolite identification studies. Data collection was done using UPLC coupled with an orthogonal hybrid quadrupole time-of-flight mass spectrometer. This experimental approach enabled the use of MS(E) data collection (where E represents collision energy) which has previously been shown to be a powerful approach for metabolite identification studies. Post-acquisition processing with a prototype mass defect filtering program was used to eliminate endogenous interferences in the study samples, greatly enhancing the discovery of metabolites. The ease of this approach is illustrated by results showing the detection and structural characterization of metabolites in plasma from a preclinical rat pharmacokinetic study.     

Computation and interpretation of molecular Omega intracules

The Omega intracule is a three-dimensional function that describes the relative positions, momenta, and directions of motion of pairs of electrons in a system. In this paper, we describe the computation of the Omega intracule for a molecular system whose electronic wave function is expanded in a Gaussian basis set. This is followed by implementation details and numerical tests. Finally, we use the Omega intracules of a number of small systems to illustrate the power of this function to extract simple physical insights from complicated wave functions.     

New synthesis of nanopowders of proton conducting materials. A route to densified proton ceramics

Low temperature routes have been developed for the preparation of BaCe_0.9Y_0.1O_2.95 (BCY10) and BaZr_0.9Y_0.1O_2.95 (BZY10) in the form of nanoparticulate powders for use after densification as ceramic membranes for a proton ceramic fuel cell. These methods make use on the one hand of the chelation of metal (II), (III) and (IV) ions by acrylates (hydrogelation route) and on the other of the destabilisation and precipitation of micro-emulsions. Both routes lead to single phase yttrium doped barium cerate or zirconate perovskites, as observed by X-ray diffraction, after thermal treatment at 900 °C for 4 h for BCY10 and 800 °C for BZY10. These temperatures, lower than those usually used for preparation of barium cerate or zirconate, lead to oxide nanoparticles of size <40 nm. Dense ceramics (?95%) are obtained by sintering BCY10 pellets at 1350 °C and BZY10 pellets at 1500 °C for 10 h. The water uptake of compacted samples at 500 °C is 0.14 wt% for BCY10 and 0.26 wt% for BZY10. Total conductivities in the range 300-600 °C were determined using impedance spectroscopy in a humidified nitrogen atmosphere. The total conductivity was 1.8×10⁻² S/cm for BCY10 and 2×10⁻³ S/cm for BZY10 at 600 °C. The smallest perovskite nanoparticles and highest conductivities were obtained by hydrogelation of precursor barium, zirconium, cerium and yttrium acrylates.     

Cognitive‐Performance Recovery of Alzheimer's Disease Model Mice by Modulation of Early Soluble Amyloidal Assemblies

A rationally designed oligomerization inhibitor interacts with early intermediate assemblies of amyloid‐β polypeptide (Aβ) through the aromatic elements and inhibits their assembly into the toxic oligomers that cause Alzheimer's disease by a unique C^α‐methylation β‐breakage strategy. The electrostatic potential of the low‐energy conformation of the dipeptide inhibitor bound to Aβ is shown.

     

Binding of muscimol-conjugated quantum dots to GABAC receptors

Functionalization of highly fluorescent CdSe/ZnS core-shell nanocrystals (quantum dots, qdots) is an emerging technology for labeling cell surface proteins. We have synthesized a conjugate consisting of approximately 150-200 muscimols (a GABA receptor agonist) covalently joined to the qdot via a poly(ethylene glycol) (PEG) linker (approximately 78 ethylene glycol units) and investigated the binding of this muscimol-PEG-qdot conjugate to homomeric rho1 GABAC receptors expressed in Xenopus oocytes. GABAC receptors mediate inhibitory synaptic signaling at multiple locations in the central nervous system (CNS). Binding of the conjugate was analyzed quantitatively by determining the fluorescence intensity of the oocyte surface membrane in relation to that of the surrounding incubation medium. Upon 5- to 10-min incubation with muscimol-PEG-qdots (34 nM in qdot concentration), GABAC-expressing oocytes exhibited a fluorescent halo at the surface membrane that significantly exceeded the fluorescence of the incubation medium. This halo was absent following muscimol-PEG-qdot treatment of oocytes lacking GABAC receptors. Incubation of the oocyte with free muscimol (100 microM-5 mM), PEG-muscimol (500 microM), or GABA (100 microM - 5 mM) substantially reduced or eliminated the fluorescence halo produced by muscimol-PEG-qdots, and the removal of GABA or free muscimol led to a recovery of muscimol-PEG-qdot binding. Unconjugated qdots and PEG-qdots that lacked conjugated muscimol neither exhibited significant binding activity nor diminished the subsequent binding of muscimol-PEG-qdots. The results indicate that muscimol joined to qdots via a long-chain PEG linker exhibits specific binding activity at the ligand-binding pocket of expressed GABAC receptors, despite the presence of both the long PEG linker and the sterically bulky qdot.