[en] Upon treatment of beef heart mitochondrial oligomycin sensitivity conferring protein (OSCP) with [¹⁴C]-N-ethylmaleimide ([¹⁴C]NEM) or dithiobis(nitro[¹⁴C] benzoate), 1 mol of either SH reagent was incorporated per mol of OSCP. Radiolabeling occurred at the level of the only cysteine residue, Cys-118, present in the OSCP sequence reported by Ovchinnikov et al.; it did not alter the biological activity of OSCP tested in a reconstituted F0-F1 system that catalyzed oligomycin-sensitive ATPase activity or ATP-Pi exchange. The parameters of [14C]NEM-OSCP binding to isolated beef heart mitochondrial F1 were assessed by equilibrium dialysis. Addition of trace amounts of Tween 20 prevented unspecific adsorption of OSCP. The binding curves showed that each F1 possesses a high-affinity OSCP binding site (K /sub d/ = 0.08 microM) and two low-affinity OSCP binding sites (K /sub d/ = 6-8 microM). Binding of OSCP to the high-affinity site on F1 is probably responsible for the ability of OSCP to confer oligomycin sensitivity to F1 in the ATPase complex

[en] Photolabeling of nucleotide binding sites in nucleotide-depleted mitochondrial F1 has been explored with 2-azido [alpha-³²P]adenosine diphosphate (2-N3[alpha-³²P] ADP). Control experiments carried out in the absence of photoirradiation in a Mg2+-supplemented medium indicated the presence of one high affinity binding site and five lower affinity binding sites per F1. Similar titration curves were obtained with [³H]ADP and the photoprobe 3'-arylazido-[³H]butyryl ADP [( ³H]NAP4-ADP). Photolabeling of nucleotide-depleted F1 with 2-N3[alpha-³²P]ADP resulted in ATPase inactivation, half inactivation corresponding to 0.6-0.7 mol of photoprobe covalently bound per mol F1. Only the beta subunit was photolabeled, even under conditions of high loading with 2-N3[alpha-³²P]ADP. The identification of the sequences labeled with the photoprobe was achieved by chemical cleavage with cyanogen bromide and enzymatic cleavage by trypsin. Under conditions of low loading with 2-N3[alpha-³²P]ADP, resulting in photolabeling of only one vacant site in F1, covalently bound radioactivity was located in a peptide fragment of the beta subunit spanning Pro-320-Met-358 identical to the fragment photolabeled in native F1. With a heavier load of photoprobe, leading to nearly 4 mol of photoprobe covalently bound per mol F1, an additional region of the beta subunit was specifically labeled, corresponding to a sequence extending from Gly-72 to Arg-83. The isolated beta subunit also displayed two binding sites for 2-N3-[alpha-³²P]ADP

[en] When beef heart mitochondrial F1-ATPase is photoirradiated in the presence of 2-azido[alpha-³²P]adenosine diphosphate, the beta subunit of the enzyme is preferentially photolabeled [Dalbon, P., Boulay, F., and Vignais, P. V. (1985) FEBS Lett. 180, 212-218]. The site of photolabeling of the beta subunit has been explored. After cyanogen bromide cleavage of the photolabeled beta subunit, only the peptide fragment extending from Gln-293 to Met-358 was found to be labeled. This peptide was isolated and digested by trypsin or Staphylococcus aureus V8 protease. Digestion by trypsin yielded four peptides, one of which spanned residues Ala-338-Arg-356 and contained all the bound radioactivity. When trypsin was replaced by V8 protease, a single peptide spanning residues Leu-342-Met-358 was labeled. Edman degradation of the two labeled peptides showed that radioactivity was localized on the following four amino acids: Leu-342, Ile-344, Tyr-345, and Pro-346

[en] [³²P]Azidonitrophenyl phosphate [(³²P]ANPP) is a photoactivatable analogue of Pi. It competes efficiently with Pi for binding to the F1 sector of beef heart mitochondrial ATPase and photolabels the Pi binding site located in the beta subunit of F1. By cleavage of the photolabeled beta subunit of F1 with cyanogen bromide, trypsin, and chymotrypsin, bound [³²P]ANPP was localized in a fragment spanning Thr 299-Phe 326. By Edman degradation of the radiolabeled tryptic peptide spanning Ile 296-Arg 337, [³²P]ANPP was found to be attached covalently by its photoreactive group to Ile 304, Gln 308, and Tyr 311. These results are discussed in terms of a model in which the phosphate group of [³²P]ANPP interacts with a glycine-rich sequence of the beta subunit, spanning Gly 156-Lys 162, which is spatially close to the photolabeled Ile 304-Tyr 311 segment of the same subunit

[en] We investigate the conformal invariance of massless Duffin-Kemmer-Petiau theory coupled to Riemannian spacetimes. We show that, as usual, in the minimal coupling procedure only the spin 1 sector of the theory-which corresponds to the electromagnetic field-is conformally invariant. We also show that the conformal invariance of the spin 0 sector can be naturally achieved by introducing a compensating term in the Lagrangian. Such a procedure-besides not modifying the spin 1 sector-leads to the well-known conformal coupling between the scalar curvature and the massless Klein-Gordon-Fock field. Going beyond the Riemannian spacetimes, we briefly discuss the effects of a nonvanishing torsion in the scalar case

[en] We study massless Duffin-Kemmer-Petiau (DKP) fields in the context of Einstein-Cartan gravitation theory, interacting via minimal coupling procedure. In the case of an identically vanishing torsion (Riemannian spacetimes) we show that there exist local gauge symmetries which reproduce the usual gauge symmetries for the massless scalar and electromagnetic fields. On the other hand, similarly to what happens with the Maxwell theory, a non-vanishing torsion, in general, breaks the usual U(1) local gauge symmetry of the electromagnetic field or, from a different point of view, imposes conditions on the torsion

[en] This document gathers several study reports in the field of fundamental research. The first part contains studies which more particularly addressed nuclear physics: study of fission and fission products by fission product distribution measurement and nuclear spectroscopy, study of light nuclei by fast neutrons, study of the neutron electric dipolar moment). The second part concerns condensed matter physics: defects and effects of radiations in solids (pure metals, alloys, semiconductors, ionic crystals, molecular crystals or ferro-electric crystals with hydrogen bond), magnetism (study of magnetic properties of different materials such as transition element compounds and alloys, rare earth compounds and alloys, and actinides; studies of other magnetism-related issues: two-dimensional magnetic order, magnetic wall structure, critical phenomenon and phase transformation, crystalline field in refractory metals, influence of conduction electrons, free-radicals in solid phase; crystal structure and properties of transition element compounds, alloys and complexes; studies of semiconductor properties and behaviour). The third part deals with physical chemistry and biophysics: studies of steady free radicals, use of free-radical spin markers in biology, stereochemistry and conformation studies, studies of vegetal macromolecules, theoretical chemistry, chemically-induced nuclear polarisation, organic and analytic electrochemistry, studies of organic photochemistry, proton dynamics in the hydrogen bond, studies of molecular movement, studies of polymers. The fourth part concerns biology: protein structure and functions, biological membrane structure and functions, radiobiology, vegetal physiology, medical research. The last chapters address advanced techniques, general services (electronic paramagnetic resonance) and applied research (pollution study: purification kinetics of river water in its torrential regime)