Design and characterization of libraries of molecular fragments for use in NMR screening against protein targets

We have designed four generations of a low molecular weight fragment library for use in NMR-based screening against protein targets. The library initially contained 723 fragments which were selected manually from the Available Chemicals Directory. A series of in silico filters and property calculations were developed to automate the selection process, allowing a larger database of 1.79 M available compounds to be searched for a further 357 compounds that were added to the library. A kinase binding pharmacophore was then derived to select 174 kinase-focused fragments. Finally, an additional 61 fragments were selected to increase the number of different pharmacophores represented within the library. All of the fragments added to the library passed quality checks to ensure they were suitable for the screening protocol, with appropriate solubility, purity, chemical stability, and unambiguous NMR spectrum. The successive generations of libraries have been characterized through analysis of structural properties (molecular weight, lipophilicity, polar surface area, number of rotatable bonds, and hydrogen-bonding potential) and by analyzing their pharmacophoric complexity. These calculations have been used to compare the fragment libraries with a drug-like reference set of compounds and a set of molecules that bind to protein active sites. In addition, an analysis of the overall results of screening the library against the ATP binding site of two protein targets (HSP90 and CDK2) reveals different patterns of fragment binding, demonstrating that the approach can find selective compounds that discriminate between related binding sites.     

Continuous sample deposition from reversed-phase liquid chromatography to tracks on a matrix-assisted laser desorption/ionization precoated target for the analysis of protein digests

Peptide mass fingerprinting by matrix-assisted laser desorption/ionization (MALDI)-mass spectrometry (MS) is one of the standard high-throughput methods for protein identification today. Traditionally this method has been based on spotting peptide mixtures onto MALDI targets. While this method works well for more abundant proteins, low-abundance proteins mixed with high-abundance proteins tend to go undetected due to ion suppression effects, instrumental dynamic range limitations and chemical noise interference. We present an alternative approach where liquid chromatography (LC) effluent is continuously collected as linear tracks on a MALDI target. In this manner the chromatographic separation is spatially preserved on the target, which enables generation of off-line LC-MS and LC-MS/MS data by MALDI. LC-MALDI sample collection provides improved sensitivity and dynamic range, spatial resolution of peptides along the sample track, and permits peptide mass mapping of low-abundance proteins in mixtures containing high-abundance proteins. In this work, standard and ribosomal protein digests are resolved and captured using LC-MALDI sample collection and analyzed by MALDI-TOF-MS.     

Thermochemistry of fluorine compounds: IV. Rubidium tetrafluoroiodate

From measurement of the heat of hydrolysis, at 25°C , the enthalpy of formation of rubidium tetrafluoroiodate is derived: ΔH°_f [RbIF₄, cryst.]₂₉₈= ?191.12±4.43 kJ mol^?1. Heat capacity measurements for RbIF₄ over the range 273–303 K are also reported.     

Mai?analytische Bestimmung von Schwefels?ure, Salpeters?ure und salpetriger S?ure in Misch- und Abfalls?uren

Ohne Zusammenfassung     

Integral equation formulation for buoyancy-driven convection problems

An integral equation formulation for buoyancy-driven convection problems is developed and illustrated. Buoyancy-driven convection in a bounded cylindrical geometry with a free surface is studied for a range of aspect ratios and Nusselt numbers. The critical Rayleigh number, the nature of the cellular motion, and the heat transfer enhancement are computed using linear theory. Green's functions are used to convert the linear problem into linear Fredholm integral equations. Theorems are proved which establish the properties of the eigenvalues and eigenfunctions of the linear integral operator which appears in these equations.