Silver and palladium complexes of some aromatic azo and azoxy compounds

The complexing ability of derivatives of azobenzene (I) is well known (I) and responsible for the production of a wide variety of dyestuffs and analytical chemicals. While the azo group generally participates in the coordination, the determination of the degree of its interaction is complicated by other functional groups which are also coordinated with the transition metal. In a previous publication (2), we reported the preparation of the silver and palladium complexes of benzo[c]cinnoline (II) and proposed that these results might be used to explain the electron donor properties of azobenzene. We are now reporting the preparation of some additional complexes with ligands containing the azo group.     

Direct determination of the configuration of a benzenediazotate: The crystal structure of sy2-sodium benzenediazotate-4-sulphonate

The crystal structure of $\text{syn}$-sodium benzenediazotate-4-sulphonate shows this to be the $\text{cis}$- and not the $\text{trans}$-isomer     

Structure and magnetism of a new pyrazolate bridged iron(II) spin crossover complex displaying a single HS-HS to LS-LS transition

The dinuclear iron(II) complex [(pypzH)(NCSe)Fe([micro sign]-pypz)(2)Fe(NCSe)(pypzH)].2H(2)O displays a single, sharp spin crossover transition between the [HS-HS] and [LS-LS] states and is structurally characterised above and below the T(1/2)= 225 K value     

Different forms of perturbation theory for the calculation of the correlation energy

Different forms of perturbation theory for the calculation of correlation energy in both closed-and open-shell systems are discussed. For closed-shell systems, Epstein–Nesbet perturbation theory is compared with Møller–Plesset (MP ) perturbation theory based on canonical Hartree–Fock orbitals and with MP theory based on internally consistent SCF orbitals. The traditional MP theory gives superior results despite its use of an inferior zeroth-order Hamiltonian. This behavior is rationalized in terms of the larger denominators present in the traditional MP theory. These conclusions are used to support the restricted open-shell perturbation methods proposed recently by Murray and Davidson, and these new methods are compared with spin-restricted Epstein–Nesbet theory and the unrestricted MP (UMP ) approach. © 1992 John Wiley & Sons, Inc.     

Characterization of dynamic and steady-state protein phosphorylation using a fluorescent phosphoprotein gel stain and mass spectrometry

Protein phosphorylation plays a vital role in the regulation of most aspects of cellular activity, being key to propagating messages within signal transduction pathways and to modulating protein function. Pro-Q Diamond phosphoprotein gel stain is suitable for the fluorescence detection of phosphoserine-, phosphothreonine-, and phosphotyrosine-containing proteins directly in sodium dodecyl sulfate (SDS)-polyacrylamide gels. The technology is especially appropriate for profiling steady-state and dynamic phosphorylation on a proteome-wide scale, as demonstrated through detection of the native phosphorylation of cardiac mitochondrial phosphoproteins and changes in this profile arising from the activity of a protein kinase. For example, Pro-Q Diamond phosphoprotein gel stain was employed to demonstrate that among the 46 subunits of the mitochondrial respiratory chain complex, NADH:ubiquinone oxidoreductase (complex I), a 42 kDa subunit is phosphorylated in the steady-state. However, exposure of mitochondria to cAMP-dependent protein kinase increases phosphorylation of this 42 kDa subunit and results in de novo phosphorylation of an 18 kDa subunit as well. Since Pro-Q Diamond dye binds to phosphorylated residues noncovalently, the staining technology is fully compatible with modern microchemical analysis procedures, such as peptide mass profiling by matrix assisted laser desorption/ionization-time of flight (MALDI-TOF) mass spectrometry and post-source decay analysis of peptide phosphorylation.     

Cyclophosphamides from aminosugars and aminonucleosides

Condensation of bis-(2-chloroethyl)phosphoramidic dichloride with 3′-amino-3′-deoxy-N,N-dimethyladenosine afforded the 2′,3′-cyclicphosphorodiamidate (III). By an improved synthesis, methyl 3-amino-3-deoxy-β-D-ribofuranoside was obtained as a model compound for conversion to the analogous 2,3-cyclicphosphorodiamidate (XII). Existence of the latter as two diastereomers due to phosphorus asymmetry was shown by nmr analysis, using comparison with the 5-(O-p-nitrobenzoate) (XIII) as a basis for assignments.     

Rotavap simulation and the estimation of boiling points

A Java applet that predicts solute losses during evaporation from a binary or ternary mixture has been developed which gives good agreement with experiment and can be used to estimate the boiling points of solutes, making use of information which is often collected and then discarded (http://www.ch.cam.ac.uk/magnus/rotavap/).     

MO Study of flavin–protein interactions in flavodoxin catalysis

MINDO /3 calculations have been performed on the Clostridium MP flavodoxin active site (a complex of the redox active coenzyme flavin mononucleotide sandwiched between the side chains of methionine and tryptophan) at various redox levels using coordinates derived from x-ray diffraction studies of the holoenzyme. Frontier orbital indices were calculated and indicate that reduction of the flavin is accompanied by induced polar states in the amino acid side chains. This stabilization of charge by the amino acid side chains could account for the reaction rate enhancement of flavin reduction catalyzed by flavodoxin. Frontier orbitals for free flavin, for the flavodoxin bound flavin without the amino acid side chains, and for the oxidized Desulfovibrio vulgaris flavodoxin active site were computed for comparison.     

Synthesis of 2-amino-4-pyrimidinones from resin-bound guanidines prepared using bis(allyloxycarbonyl)-protected triflylguanidine

We have synthesized novel heterocyclic compounds from resin-bound guanidines. For this purpose, an amine immobilized on a solid support was acylated with protected amino acids. Following the deprotection, the liberated amines were guanidinylated utilizing a new member of the family of diurethane-protected triflyl guanidine reagents, N,N'-bis(allyloxycarbonyl)-N' '-triflylguanidine. The deprotected guanidines were subsequently regioselectively cyclized with beta-keto esters yielding novel compounds containing heterocyclic structures in high purities.     

Particle velocity measurements in induction plasma spraying

Laser Dopple anemometry (LDA) measurements of the particle velocity are carried out during an induction plasma spraying operation. The velocity of nickel alloy particles, or molten droplets, at the exit of an induction plasma torch prior to impact on the substrate is shown to vary with the plasma and powder injection conditions. Plasma spraying under soft vacuum (150–450 Torr) gives rise to substantially higher particle velocities (40–60 m/sec) compared to those attained at atmospheric pressure (10–20 m/sec).