Structural analysis of two Torbanites at different evolutionary stagesInvestigation of the quantitative reliability of fa determination by 13C CP/MAS n.m.r.

Lipids and Macromolecular Lipids of the Hydrocarbon-rich Microalga Botryococcus braunii. Chemical Structure and Biosynthesis. Geochemical and Biotechnological Importance

“…Very closely related structures were thus observed in torbanites and in the resistant biopolymers, PRB A and PRB B respectively, from the A and B races as illustrated by the solid state 13C-NMR spectra in Fig. 19 (36,67,68,(80)(81)(82)(83)(84)(85). This chemical evidence definitely confirmed the correlation between B. braunii and torbanites so far based only on morphological similarities.…”

Carbon-13 solid-state NMR of Argonne-premium coals

“…12 The aromaticity, /a, has been reported for whole coals, macerals, soil, and other fossil fuel related materials.12-17 Other researchers have also used dipolar-dephasing (DD) tech-niques18-22 along with the normal CP/MAS integrations over selected chemical shift ranges to subdivide /a values into the amount of protonated and nonprotonated carbons. [23][24][25][26][27] The quantitative accuracy of these aromaticity values has been open to question for two reasons. First, competing effects in the spin dynamics of cross-polarization do not polarize all spins at the same rate and differences in the spin lattice relaxation in the rotating frame may alter the signals such that they do not achieve full polarization at the same contact time.…”