Two-dimensional 13C Nuclear Magnetic Resonance Research Articles

Detection of Labile Conformations of Elastin’s Prolines by Solid-State Nuclear Magnetic Resonance and Fourier Transform Infrared Techniques

Samples of native elastin are prepared with high levels of enrichment at its prolines, which are believed to play a major role in the elasticity of elastin. Major and minor populations of trans and cis isomers at the Xaa-Pro imide bonds are detected in two-dimensional 13C nuclear magnetic resonance (NMR) experiments. One- and two-dimensional 13C NMR and isotope-edited Fourier transform infrared experiments are also used to identify the prolines' folded and unfolded states, type II β-turn and random coil, respectively, at physiological temperatures. This study provides new details about elastin's conformational ensemble. In addition, the cis-trans isomerization of its abundant prolines provides an additional mechanism of fiber elongation in tissue.

Functional Groups Determine Biochar Properties (pH and EC) as Studied by Two-Dimensional 13C NMR Correlation Spectroscopy

While the properties of biochar are closely related to its functional groups, it is unclear under what conditions biochar develops its properties. In this study, two-dimensional (2D) 13C nuclear magnetic resonance (NMR) correlation spectroscopy was for the first time applied to investigate the development of functional groups and establish their relationship with biochar properties. The results showed that the agricultural biomass carbonized to biochars was a dehydroxylation/dehydrogenation and aromatization process, mainly involving the cleavage of O-alkylated carbons and anomeric O-C-O carbons in addition to the production of fused-ring aromatic structures and aromatic C-O groups. With increasing charring temperature, the mass cleavage of O-alkylated groups and anomeric O-C-O carbons occurred prior to the production of fused-ring aromatic structures. The regression analysis between functional groups and biochar properties (pH and electrical conductivity) further demonstrated that the pH and electrical conductivity of rice straw derived biochars were mainly determined by fused-ring aromatic structures and anomeric O-C-O carbons, but the pH of rice bran derived biochars was determined by both fused-ring aromatic structures and aliphatic O-alkylated (HCOH) carbons. In summary, this work suggests a novel tool for characterising the development of functional groups in biochars.

Comparison of the glycosaminoglycans isolated from the skin and head cartilage of Gould's arrow squid ( Nototodarus gouldi)

The glycosaminoglycans from the skin and head cartilage of the squid Nototodarus gouldi have been isolated and characterised by constituent disaccharide and neutral sugar analysis, 13C nuclear magnetic resonance (NMR) spectroscopy, anion exchange and size exclusion chromatography. The glycosaminoglycans from both tissues are chondroitin sulphate species. The skin consists principally of unsulphated but relatively highly glycosylated material. The chondroitin sulphate from the head cartilage is more highly sulphated, predominantly C-4,6diS (chondroitin sulphate E), with a higher molecular weight than the skin derived material but somewhat less highly glycosylated. To provide a standard for the assignment of the 13C NMR spectrum, C-4,6diS was chemically prepared from bovine tracheal chondroitin sulphate. This showed that it is not possible to distinguish between a mixture of the monosulphates, C-4S and C-6S, and the C-4,6diS by one-dimensional and simple two-dimensional 13C NMR techniques.