Inhomogeneously Broadened Spin-Label Spectra

摘要: Inhomogeneous broadening of the ESR lines nitroxide spin labels due to hyperfine structure is a pest that has complicated work labelers since shortly after beginning spin-label era (Plachy and Kivelson, 1967; Poggi Johnson, 1970) continually until present (for example, Jolicoeur Friedman, 1971; Kovarskii et al, 1972; Bullock 1975; Ahn, 1976; Freed, Lim Jones Schwartz, 1981; Ottaviani 1983; More 1984; Lee Shetty, 1985). It problem can been solved rigorously for number by combining NMR, ESR, chemical substitution techniques (Kreilick, Briere 1967, 1970; Michon Rassat, Chiarelli 1973; Barbarin 1978a, 1978b; Labsky 1980; Windle, Ottaviani, 1987). These taken together establish patternof given label simulation fine tunes coupling constants in set experimental conditions. To proceed with rigor, this tuning must be done because vary temperature 1967,1970; Atherton, 1987) solvent (Briere Eaton Also, effectivespacing varies concentration—a variation depends strongly on 1967). The effective spacing alignment an ordered fluid (Polnaszek Bales 1984) one imagine it might other parameters as well. Thus, but remarkable precision some cases, notably having particularly simple patterns or ones give partially resolved spectra. tedious procedure, unavoidable if high required experiment involving In most literature, spectra are unresolved, either intrinsically nature experiment, artificially, oxygen paramagnetic species. unresolved procedures correct inhomogeneity become quite remarkably accurate.