Abstract
The combination of cross polarization, dipolar decoupling and magic angle spinning results in liquid-like high-resolution
13
C and
15
N n.m.r. spectra of a wide variety of solid materials. Structural determinations based on such
13
C n.m.r. spectra include the measurement of the extent to which pyrolysed polyacrylonitrile fibres (Orion) retain aliphatic character during the first step of the production of a carbon fibre, the determination of the chemical identity of the cross links formed from an acetyleneterminated polyimide resin, and the characterization of the metabolic products of a bacterial fermentation of wood lignin. All of these non-destructive analyses are performed on intact heterogeneous samples. The high resolution of the carbon experiment can also be exploited by obtaining
proton
spin-lattice relaxation parameters for chemically different protons in solids. Because of spin diffusion, these parameters are dependent on spatial proximity and so are helpful in measuring the homogeneity of solid blends of polymers such as poly(phenylene oxide) and polystyrene. High-resolution
13
C n.m.r. spectra of polymers can also be used for measuring microscopic chain dynamics.
13
C rotating-frame relaxation parameters observed for polycarbonate and poly (ethylene terephthalate) are related to the effects on motion of annealing, additives and structural substitutions. Individual relaxation rates are observed for individual carbons, so the behaviour of side groups is cleanly separated from that of the main chain. All of the line-narrowing and sensitivity-enhancing techniques applied to
13
C n.m.r. of solids work equally well for
15
N n.m.r. Use of
15
N rotating-frame and cross-polarization parameters leads to the assessment of the relative concentrations of
13
C -
15
N and
12
C -
15
N pair concentrations in the main chains of multiply labelled proteins. Such measurements can be used to characterize the rate of protein turnover in fully expanded soybean leaves, as well as the details of protein synthesis in cultured soybean cotyledons.
Cited by
53 articles.
订阅此论文施引文献
订阅此论文施引文献,注册后可以免费订阅5篇论文的施引文献,订阅后可以查看论文全部施引文献