Displacement affinity chromatography of protein phosphatase one (PP1) complexes

Background  

Protein phosphatase one (PP1) is a ubiquitously expressed, highly conserved protein phosphatase that dephosphorylates target protein serine and threonine residues. PP1 is localized to its site of action by interacting with targeting or regulatory proteins, a majority of which contains a primary docking site referred to as the RVXF/W motif.     

Homolytic displacement at carbon: XI. Intramolecular homolytic displacement as a route to cyclopentane and tetrahydrofuran derivatives from hex-5-enyl- andhex-3-oxo-5-enylcobaloximes

5-Methylhex-5-enylcobaloxime reacts with carbon tetrachloride and with fluorotrichloromethane at 80–100°C to give substantially pure 1-methyl-1-(β,β,β-trichloroethyl)- and 1-methyl-1-β-fluoro-β,β-dichloroethyl)-cyclopentane. Hex-5-enylco-baloxime also gives trichloroethylcyclopentane from carbon tetrachloride, but the yield is dependent on the concentration of carbon tetrachloride. Similar cyclisation to give trichloroethyl- or fluorodichloroethyltetrahydrofuran is observed in the reactions of hex-3-oxo-5-enylcobaloxime with carbon tetrachloride and fluorotrichloromethane. However, no cyclisation was observed in the reactions of the ester, hex-2-one-3-oxo-5-enylcobaloxime, with carbon tetrachloride. These reactions are believed to take place by attack of a polyhalogenomethyl radical at the terminal unsaturated carbon of the organic ligand, followed either by an intramolecular homolytic displacement in which the carbon radical at position-5 attacks carbon-1 with displacement of cobaloxime(II), or by a halogen atom abstraction.     

The phase-dependent photochemical reaction dynamics of halooxides and nitrosyl halides

Recent progress in understanding the phase-dependent reactivity of halooxides and nitrosyl halides is outlined. Halooxide reactivity is represented by the photochemistry of chlorine dioxide (OClO) and dichlorine monoxide (ClOCl). The gas phase photochemical dynamics of OClO are contrasted with the dynamics in condensed environments. The role of excited-state symmetry in defining the reaction dynamics and the observation of photoisomerization resulting in the production of ClOO are discussed. The current understanding of the excited-state reaction dynamics of ClOCl and evidence for photoisomerization of this species resulting in the production of ClClO are outlined. Finally, the photochemical reaction dynamics of the nitrosyl halide ClNO are presented. The main difference between the gas and condensed phase reaction dynamics of this species is that whereas photodissociation to form Cl and NO dominates the gas phase reaction dynamics, photoisomerization resulting in ClON production occurs to an appreciable extent in condensed environments. The observation of photoisomerization for OClO, ClOCl and ClNO suggests that this process is a general feature of the condensed phase reaction dynamics for smaller halooxides and nitrosyl halides. Finally, future areas for study in both halooxide and nitrosyl halide photoreactivity are outlined.     

Oxymetallation: XIX. Preparation of the first oxymercurials derived from cyclopropane

Three oxymercurials, RO(CH₂)₃HgBr where R = Bu^tO, BrHg(CH₂)₃, and Ac, have been isolated from the reaction of cyclopropane with mercury(II) acetate, t-butyl hydroperoxide, and 60% aqueous perchloric acid (20 mol%) in dichloromethane for 5 d, followed by anion exchange with aqueous potassium bromide.     

Techniques for high power microwave sources at high average power

Experiments on CLIA (compact linear induction accelerator), capable of generating 750 kV and 10 kA into a matched load using magnetic switching to produce 60 ns long pulses, are described. As a first application, the authors used CLIA to drive a water-cooled L-band magnetron at repetition rates as high as 250 Hz with no breakdown or pulse shortening. This gives an average power of 6.3 kW. A short burst at 1 kHz demonstrates operation that would translate to an average power of approximately 25 kW. In this regime operation is not limited by gas build-up, electrode erosion or microwhisker depletion. Currently, the authors are operating on CLIA with a high current relativistic klystron. Beams with modulated current powers of approximately 1 GW have been generated at 100 Hz for bursts as long as 5000 pulses. It is concluded that there are no apparent obstacles to much higher average powers at higher peak powers     

Evaluation of gel permeation chromatography to Fourier transform infrared spectrometric detection using a modified thermospray for analysis of polystyrene samples

A heated gas flow modified thermospray was used to couple gel permeation chromatography (GPC) to Fourier transform infrared spectrometry (FTIR) for the analysis of the standard polystyrene samples. Effluents from the GPC column were evaporated and the solutes were deposited as a series of spots on the surface of a moving stainless steel belt (0.025 mm thickness × 13 mm width). The belt continuously transferred the spots into the diffuse reflectance (DRIFT) accessory of the FTIR spectrometer, enabling identification of the deposited solutes by measurement of the diffuse reflectance IR spectrum. The IR spectra of the separated components showed excellent agreement of the spectral features to those of standard FTIR spectra and no thermal degradation was observed. Received: 20 May 1996 / Revised: 17 October 1996 / Accepted: 28 November 1996     

A Synthesis of an Ionomycin Calcium Complex

Caught in the middle : The ionomycin calcium complex (see structure; O red, Ca green) was the target of an approach featuring the efficient asymmetric synthesis of an allene by a copper(I)‐mediated anti‐selective S_N2′ reaction, a highly stereoselective gold(III)‐catalyzed cycloisomerization of an α‐hydroxyallene, and a Rh‐catalyzed rearrangement of an α‐diazo‐β‐hydroxyketone.

     

Free radical rearrangements of organocobaloximes: alkynyl to cycloalkylidene and hexenyl to cyclopentylmethyl

Under irradiation by tungsten light in pyridine solution, several substituted alkylcobaloximes undergo rearrangement to more stable substituted alkyl- or alkenyl-cobaloximes. When the same reactions are carried out in the presence of carbon tetrachloride or chloroform, no rearranged organocobaloximes are obtained, but a variety of organic products are obtained derived from the interception of transient organic radicals by the halogenated solvent. The rearrangements are rationalised in terms of a reversible homolysis of the carbon-cobalt bond, rearrangement of the organic radical and recapture by the cobalt(II) fragment to give complexes that are more stable to irradiation than their precursors.     

Purity measurement by differential scanning calorimetry: An alternative method of computation

The established procedure for the estimation of purity from differential calorimetric melting range results involves empirical linearization of the data, which can be time consuming and may introduce a subjective element into the calculation. This is sometimes thought to be a disadvantage of the method. A modification of the procedure has been developed which avoids this difficulty and offers advantages in ease of data logging and of overall computer programming.     

Evaluation of gel permeation chromatography to Fourier transform infrared spectrometric detection using a modified thermospray for analysis of polystyrene samples

A heated gas flow modified thermospray was used to couple gel permeation chromatography (GPC) to Fourier transform infrared spectrometry (FTIR) for the analysis of the standard polystyrene samples. Effluents from the GPC column were evaporated and the solutes were deposited as a series of spots on the surface of a moving stainless steel belt (0.025 mm thickness × 13 mm width). The belt continuously transferred the spots into the diffuse reflectance (DRIFT) accessory of the FTIR spectrometer, enabling identification of the deposited solutes by measurement of the diffuse reflectance IR spectrum. The IR spectra of the separated components showed excellent agreement of the spectral features to those of standard FTIR spectra and no thermal degradation was observed.