An Investigation of the N-Arylsulfonylation of 2-Azetidinones

N-Arylsulfonylation of 2-azetidinones can lead to the diastereoselective formation of oligomerization products. However, a simple increase of arylsulfonyl chloride concentration minimized oligomerization and allowed preparation of 1-arylsulfonyl-2-azetidinones in good yield.     

Spatial energy estimates in dynamical problems for a semi-infinite piezoelectric beam

The behaviour of the total energy for a semi-infinite piezoelectricbeam, with uniform or variable cross-section, in dynamical conditionsis investigated. Precisely, we obtain some estimates in termsof the data for the energy of the portion of the body at distancegreater than z from the base and for its norm in L¹(0,t) (wheret is an arbitrary positive time). We obtain some estimates whichdepend on the initial data if t z/V (where V is a computablepositive material constant); if t > z/V, by using also theKorn inequality, we show that the bounds depend on all the data.Under mild hypotheses on the initial data we derive the asymptoticbehaviour of the energy as z +. All possible combinations ofboundary conditions are examined and the kind of the estimateis formally the same for all the problems whether the beam isa cylinder or not.     

Spectroscopic characterization of a high-potential lipo-cupredoxin found in Streptomyces coelicolor

For many streptomycetes, a distinct dependence on the "bioavailability" of copper ions for their morphological development has been reported. Analysis of the Streptomyces coelicolor genome reveals a number of gene products encoding for putative copper-binding proteins. One of these appears as an unusual copper-binding protein with a lipoprotein signal sequence and a cupredoxin-like domain harboring a putative Type-1 copper-binding motif. Cloning of this gene from S. coelicolor and subsequent heterologous expression in Escherichia coli has allowed for a thorough spectroscopic interrogation of this putative copper-binding protein. Optical and electron paramagnetic resonance spectroscopies have confirmed the presence of a "classic" Type-1 copper site with the axial ligand to the copper a methionine. Paramagnetic NMR spectroscopy on both the native Cu(II) form and Co(II)-substituted protein has yielded active-site structural information, which on comparison with that of other cupredoxin active sites reveals metal-ligand interactions most similar to the "classic" Type-1 copper site found in the amicyanin family of cupredoxins. Despite this high structural similarity, the Cu(II)/(I) midpoint potential of the S. coelicolor protein is an unprecedented +605 mV vs normal hydrogen electrode at neutral pH (amicyanin approximately +250 mV), with no active-site protonation of the N-terminal His ligand observed. Suggestions for the physiological role/function of this high-potential cupredoxin are discussed.