The ring-closing metathesis reaction of N,N-diallyltosylamide (2) catalyzed by [(η 6 -pcymene)(PCy 3 )RuCl(dCdCdCPh 2 )]X (X ) OTf (CF 3 SO 3 ) (1), PF 6 , BF 4 , SbF 6 ) and by [(η 6 -pcymene)(PCy 3 )RuCl(dCdCdC(p-Y-C 6 H 4 ) 2 ]OTf (Y ) MeO, Cl, F) complexes has been monitored in situ by 1 H NMR, in benzene-d 6 and in dichloromethane-d 2 , in the temperature range 33-58 °C. The reaction proceeds selectively to form N-tosyl-2,5-dihydropyrrole (3), in the case of complexes [(η 6 -p-cymene)(PCy 3 )RuCl(dCdCdCPh 2 )]X (X ) OTf, PF 6 ), under thermal activation, while lower reactivity and selectivity are exhibited by the other complexes. Evidence is given for an activation step leading to the catalytic species. Under pseudo-firstorder conditions, the metathesis reaction catalyzed by complex 1 is first-order in the diallylic substrate in benzene-d 6 above 50 °C when the propagation step is slower than the activation of the catalytic species. The reaction is zero-order in substrate at lower temperatures when the activation of the ruthenium complex is slower than the ring-closing metathesis process and faster in benzene-d 6 than in dichloromethane-d 2 . The presence of added p-cymene does not inhibit the reactivity, while inhibition occurs in the presence of added PCy 3 . In the latter case, the substrate is converted slowly into an isomeric product. When appropriate, the behavior of complex 1 as precatatyst is compared with that of other catalytic systems. 1 H NMR, FT-IR, and UV-visible analyses indicate that the activation process of complex 1 is characterized by an intramolecular transformation of the ruthenium-allenylidene group into the corresponding ruthenium-phenylindenylidene moiety.

W-band (95 GHz) HYSCORE and pulse ENDOR are used to characterize the nitrosyl d(1) heme complex (d(1)NO) of cd(1) nitrite reductase from Pseudomonas aeruginosa in the wild type and the Y10F mutant. The spectra and the derived (14)N hyperfine and quadrupole interactions were found to be the same for wt and Y10F. This suggests that Tyr10 does not influence the NO ligand orientation in the reduced state in solution. This study is the first application of HYSCORE at high fields and shows its potential for characterizing low gamma nuclei with large hyperfine couplings.

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SummaryThe structural and catalytic properties of Pseudomonas aeruginosa cd 1 nitrite reductase, a key enzyme in bacterial denitrification, are reviewed in this paper. The mechanism of reduction of nitrite to NO is discussed in detail with special attention to the structural interpretation of function. The ability to stabilize negatively charged molecules, such as the substrate (nitrite) and other ligands (hydroxide and cyanide), is a key feature of catalysis in cd 1 NIRs. The positive potential in the active site is largely due to the presence of the two conserved distal histidines, which are involved in both substrate binding and product release. IUBMB Life, 55: 617-621, 2003

We report on the use of one-dimensional photonic crystals to detect clinically relevant concentrations of the cancer biomarker ERBB2 in cell lysates. Overexpression of the ERBB2 protein is associated with aggressive breast cancer subtypes. To detect soluble ERBB2, we developed an optical set-up which operates in both label-free and fluorescence modes. The detection approach makes use of a sandwich assay, in which the one-dimensional photonic crystals sustaining Bloch surface waves are modified with monoclonal antibodies, in order to guarantee high specificity during the biological recognition. We present the results of exemplary protein G based label-free assays in complex biological matrices, reaching an estimated limit of detection of 0.5 ng/mL. On-chip and chip-to-chip variability of the results is addressed too, providing repeatability rates. Moreover, results on fluorescence operation demonstrate the capability to perform high sensitive cancer biomarker assays reaching a resolution of 0.6 ng/mL, without protein G assistance. The resolution obtained in both modes meets international guidelines and recommendations (15 ng/mL) for ERBB2 quantification assays, providing an alternative tool to phenotype and diagnose molecular cancer subtypes.