S1.20 Divalent metal binding to bovine heart F1 ATPase: An FT-ESEEM study

The divalent metal binding sites of beef heart mitochondria F1ATPase were studied by FT-ESEEM spectroscopy, using Mn(II) as a paramagnetic probe, which replaces the naturally occurring Mg(II) and maintains the enzyme catalytic activity. Purified F1ATPase still containing three endogenous tightly bound nucleotides, named MF1(1,2), was obtained under mild conditions, whereas a harsher treatment gave a fully nucleotide depleted enzyme, named MF1(0,0). When MF1(1,2) was loaded with Mn(II) in 1:0.8 ratio, the spectrum showed evidence of a nitrogen interacting with the metal, while this interaction was not present in the spectrum of MF1(0,0) loaded with Mn(II) in the same ratio. However, when MF1(0,0) was loaded with 2.4 Mn(II), the spectrum showed metal-nitrogen interaction resembling that of MF1(1,2) loaded with Mn(II) in 1:0.8 ratio. When MF1(1,2) was loaded with 2.4 Mn(II) the metal-nitrogen interaction signal remained and a phosphorous coordination to the metal was also evident, indicating a binding of Mn2+ to a site containing a tightly bound nucleotide but metal free. These results strongly support the role of the metal alone in structuring the catalytic sites of the enzyme while ESEEM technique appears to be a sensitive and suitable spectroscopic method for conformational studies of MF1 with the advantage of using proteins in frozen solution

Understanding and controlling the efficiency of Au24M(SR)18 nanoclusters as singlet-oxygen photosensitizers

Atomically precise Au24M(SR)18 clusters were used as singlet-oxygen photosensitizers. Comprehensive kinetic analysis provided insights into the mechanism and driving-force dependence of the quenching of 1O2 by gold nanoclusters

Echo detected EPR as a tool for detecting radiation-induced defect signals in pottery

Archaeological fragments of pottery have been investigated by using CW-EPR and Echo Detected EPR (EDEPR). EDEPR allows to remove the CW-EPR dominant Fe(III) background spectrum, hiding much weaker signals potentially useful for dating purpose. EDEPR spectra attributed to a methyl radical and to feldspar defects have been recorded at room and low temperature for an Iron Age cooking ware (700 B.C.). A study on the dependence of EDEPR intensity over absorbed dose on a series of gamma-irradiated brick samples (estimated age of 562 +/- 140 B.C.) has confirmed the potential efficacy of the proposed method for spotting defect signals out of the strong iron background. (C) 2011 Elsevier Ltd. All rights reserved

Le analisi non invasive dei pigmenti nei Graduali D40, D41, D42 e D43 del Museo di Sal\uf2: risultanze e correlazioni

Le analisi non invasive condotte mediante spettroscopie FORS e XRF della tavolozza pittorica dei quattro Graduali miniati del Museo di Sal\uf2 hanno identificato i pigmenti impiegati dai miniatori, rivelando una ricca scelta di pigmenti (oltremare, cinabro, minio, ocre, verdigris, azzurrite, malachite), sapientemente usati tono su tono, con abbondante uso di oltremare. Le analisi hanno mostrato che tale pigmento assai prezioso fu impiegato non solo nelle vesti dei Santi pi\uf9 importanti, ma anche nei fregi e negli ornamenti, fatto indicativo di una committenza molto ricca

Electron Paramagnetic Resonance as a Probe for Metal Ions and Radicals in Paper

Electron Paramagnetic Resonance (EPR) is a technique devoted to the identification and characterization of paramagnetic species, i.e. chemical species with unpaired electrons. Very common paramagnetic species which can be detected through EPR in historic paper are Fe(III), Mn(II), Cu(II) ions and radicals, where Fe(III), Cu(II) and radicals play a relevant role in paper degradation. Specifically, Fe(III) is almost ubiquitous in historic paper. Here we propose an overview of the EPR signals in historic and artificially aged paper, and in particular, we would like to show how a deep analysis of EPR signals from paper could provide useful information about the paper's origin and unique indications of the degradation and oxidation level of the paper

Characterization of ancient and modern papers by CW-EPR spectroscopy

Several old (15th to 18th century), new (1900\u20131950) and recently produced (after 1990) papers have been investigated by X-band continuous-wave electron paramagnetic resonance (EPR) spectroscopy. Signals from Cu(II), Fe(III), Mn(II) and radicals are apparent. A clear-cut distinction is observed between recently produced papers and the other samples: recent papers show just EPR signals from Mn(II) and sometimes small signals from Fe(III) in rhombic site, while the older samples show usually strong signals from Fe(III), Mn(II), Cu(II) and radicals. Furthermore, Mn(II) EPR signals from recent papers are characterized by small zero-field splitting (ZFS) parameters, indicating Mn(II) in high-symmetry sites, while older samples show broader Mn(II) EPR signals, typical for Mn(II) in low-symmetry sites (increased ZFS parameters)

Spin concentration in a possible ESR dosimeter: An electron spin echo study on X-irradiated ammonium tartrate

Several single crystals and powder samples of ammonium tartrate, recently proposed as a possible ESR dosimeter, have been X-irradiated with different doses. The total radical concentration has been determined by quantitative cw ESR, by comparison with a standard. The samples have been studied by electron spin echo spectroscopy. The two-pulse echo decay has been obtained and simulated by a single exponential function for different values of the microwave power of the pulses and for different pulse lengths. The dependence of the phase memory time TM on the microwave power has been exploited to get information on the contribution of the instantaneous diffusion to spin dephasing. At room temperature in the range of radical concentrations of 1E18-1E19 spins/cm3 the instantaneous diffusion is the dominant spin dephasing mechanism. The linear dependence of the instantaneous diffusion on the total concentration of the radicals is in agreement with the theory. From the latter result we conclude that the average radical-radical distance corresponds to a random distribution of the radicals in the matrix. A simple method of measuring the radical concentration by the ESE decays in powder samples of irradiated ammonium tartrate is described

Probing firing-induced changes in non-carbonate clay through 55Mn EPR techniques

Non-carbonate clay samples, fired in steps of 50 \ub0C between 600 \ub0C and 1000 \ub0C, were examined through electron paramagnetic resonance (EPR) techniques (X- and Q-Band pulsed- and cw-EPR). X-band pulsed EPR and Q-Band pulsed- and cw-EPR techniques were able to spot 55Mn(II) signals out of the large iron background in the full range of firing temperatures, allowing one to follow the phase transformations through the evolution of the manganese signal. Q-Band pulsed EPR turned out to be particularly suitable to detect even small amounts of this ion in calcite, while the 55Mn hyperfine coupling constant, determined through Q-Band cw-EPR, could be used to detect transitions to the glassy phase