[en] In the present study, e.s.r. spectra have been observed following γ-irradiation of dilute frozen solutions of tetrolic acid, MeC≡CCO₂H, in CFCl₃ at 77 K. A typical spectrum is shown which we interpret in terms of an isotropic quartet from the parent radical cation. MeC≡CCo₂H^+·, and an anisotropic triplet arising from the propargyl radical, ·CH₂C≡CCO₂H, formed by deprotonation of the parent cation. This appears to be the first example of an alkyne radical cation to be observed in a CFCl₃ matrix. (author)

[en] From the coupling constants obtained from a wide variety of β-muonium-substituted alkyl radicals and their protiated analogues, we conclude that the preference for the conformation in which the β-C-Mu bond eclipses the singly occupied orbital depends largely on hyperconjugative effects, although steric effects become more important as the size of the substituents at the radical centre is increased. Cyclic radicals, including the β-muonium-substituted cyclopentyl and cycloheptyl radicals, are discussed with respect to the 'limiting isotope ratio' towards which all alkyl radicals should tend at high temperatures, according to hyperconjugation theory. We conclude that the value of this limiting ratio is 1.18 ± 0.05. (author)

[en] Exposure of dilute solutions of Me₃SiC≡CH in CD₃OD to ⁶⁰Co γ-rays at 77 K gave mainly H(D)C=(dC/dt)SiMe₃ radicals together with traces of H₂C=(dC/dt)SiMe₃. The relative concentration of the latter increased markedly on annealing, presumably via proton transfer. The results suggest that electron addition is followed by protonation and hence that the anion of HC≡CSiMe₃ is strongly basic. The β-proton hyperfine coupling of 59 G for the monodeuterio derivative is equal to that for the two β-protons in H₂C=(dC/dt)SiMe₃, and also equals the ²H coupling after correction for the difference in proton/deuteron magnetogyric ratios. Hence the radical must be linear, the SOMO being, nominally, the in-plane 2p orbital on the carbon atom bound to silicon. The β-proton coupling for the radical Me₃Si(H)C=(dC/dt)SiMe₃ formed similarly from Me₃SiC≡CSiMe₃ is much greater (76 G), suggesting that this radical is bent, with a trans configuration, favouring overlap with the C-H bonding orbital. Exposure of the pure liquids to a beam of positive muons gave the corresponding muonated radicals, H(μ)C=(dC/dt)SiMe₃ and Me₃Si(μ)C=(dC/dt)SiMe₃. The muon-electron hyperfine couplings, corrected for the difference in the magnetic moments, were both greater than the corresponding proton couplings by a factor of 1.14; reasons for this enhancement are discussed. (author)

[en] On γ-irradiation of dilute solutions of propiolic acid in CFCl₃ at 77 K, no e.s.r. spectrum assignable to the parent cation was detected. Instead, a triplet was observed with a coupling of 5.8 G, which we assign to the dimer cation (HC≡CCO₂H)₂ sup(+.). On similar treatment, the esters MeC≡CCO₂Me and HC≡CCO₂Me gave only the rearranged cations: RC≡CC(=OH)OCH₂. (author)

No abstract available

[en] This paper describes work performed by the Office of Civilian Radioactive Waste Management (OCRWM) Management and Operating (M ampersand O) Contractor. The work presented in this paper resulted from waste stream analyses conducted in support of the M ampersand O Phase 1 and 2 Repository Thermal Loading Studies. These analyses integrated system design with underground design. The Phase 1 study in particular examined the effects of various system configurations and operating concepts on the waste stream arriving at the proposed repository at Yucca Mountain

[en] Isolated rat pancreatic islets were pulse-labeled for 5 min with [³H]leucine then chased for 25 min, during which time endogenously labeled [³H]proinsulin becomes predominantly compartmented in immature secretory granules. The islets were then homogenized in isotonic sucrose (pH 7.4) and a beta-granule preparation obtained by differential centrifugation and discontinuous sucrose gradient ultracentrifugation. This preparation was enriched 8-fold in beta-granules. Aside from contamination with mitochondria and a limited number of lysosomes, the beta-granule preparation was essentially free of any other organelles involved in proinsulin synthesis and packaging (i.e. microsomal elements and, more particularly, Golgi complex). Conversion of endogenously labeled [³H]proinsulin was followed in this beta-granule fraction for up to 2 h at 37 degrees C in a buffer (pH 7.3) that mimicked the cationic constituents of B-cell cytosol, during which time 92% of the beta-granules remained intact. Proinsulin conversion was analyzed by high performance liquid chromatography. The rate of proinsulin conversion to insulin was stimulated by 2.2 +/- 0.1-fold (n = 6) (at a 60-min incubation) in the presence of ATP (2 mM) and an ATP regenerating system compared to beta-granule preparations incubated without ATP. This ATP stimulation was abolished in the presence of beta-granule proton pump ATPase inhibitors (tributyltin, 2.5 microM, or 1,3-dicyclohexylcarbodiimide, 50 microM). Inhibitors of mitochondrial proton pump ATPases had no effect on the ATP stimulation of proinsulin conversion. When granules were incubated in a more acidic buffer, proinsulin conversion was increased relative to that at pH 7.3. At pH 5.5, ATP no longer stimulated conversion, and tributyltin and 1,3-dicyclohexylcarbodiimide had no effect

[en] Sulphur centred radicals of the type R₂C(Mu)-S· have been observed by the μSR technique, during the irradiation of a number of thiocarbonyl compounds with positive muons; such thiyl radicals, RS·, have never been detected by e.s.r. spectroscopy in the liquid phase. (author)

[en] According to TF-μSR measurements and PM3 M.O.calculations, free radicals formed by muonium addition to styrene, 1-vinylnaphthalene and 2-vinylnaphthalene are of the arylethyl type ( ArCHCH₂Mu·) since it is energetically considerably more favourable for Mu· to add to the vinyl group than to the aromatic rings. In contrast, Mu· adds to 9-vinylanthracene at the 10-position yielding the 4-vinyldibenzocyclohexadienyl radical, which is more stable by ca 7 kcal/mol than the 9-anthrylethyl radical.For diacetylenes (i.e. MeC₄Me) the propensity for muonium addition is to the terminal carbon atoms, but the choice is less clear for Me₃SiC₄SiMe₃. For PhC₄Ph, 3 radicals are detected and are assigned to the C1, C2 and ortho ring adducts, with the couplings (and yields): 334 (5.7%), 389 (4.2%), 439 (3.6%)

[en] Published in summary form only