Tentative assignment for each carbon resonance in the natural abundance high resolution carbon-13 nuclear magnetic resonance Fourier transform spectrum at 25.2 MHz of the biologically active cyclic octapeptides, synthetic oxytocin (43 carbons) and lysine-vasopressin (46 carbons) and the cyclic dodecapeptide bacitracin (66 carbons) has been made using a number of different techniques. The 1% ass...

The 13C nuclear spin-lattice relaxation time Tl was studied in liquid CSa from -106°C to +35X! at resonance frequencies of 14, 30, and 62 MHz. The relaxation is caused by anisotropic chemical shift and spin-rotation interaction. It is shown that for linear molecules the spin-rotation constant C and the anisotropy of the chemical shift Aa can be obtained from the relaxation rates without use of ...

Carbon nanoparticles (CNPs) have been widely used in tumor drainage lymph node (TDLN) imaging, drug delivery, photothermal therapy, and so on. However, during the theranostic applications, the accumulation efficiency of CNPs in target organs is unknown yet, which largely hinders the extension of CNPs into clinical uses. Herein, we prepared skeleton-labeled 13C-CNPs that had identical properties...

Two new terpenoids, (+)-3-oxo-thermarol and 11-acetoxyeudesman-4alpha-methyl-5alpha-ol along with the (+)- thermarol were isolated from the aerial parts of Salzmmania nitida. The structures and unambiguous 1H and 13C chemical shift assignments were established by spectroscopic means, including homo and heteronuclear techniques.

A bidirectional synthesis of the originally proposed structures for the natural products elatenyne and a chloroenyne from Laurencia majuscula is described along with a reassessment of the structures of the halogenated enynes based upon a 13C NMR chemical shift/structure correlation.

The ionization behavior of cholic acid, deoxycholic acid, and chenodeoxycholic acid in a variety of physiologically important molecular environments was studied using 13C NMR spectroscopy. The apparent pKa of the carboxyl group was determined from titration curves obtained from the dependence of the carboxyl carbon chemical shift on pH. Using 90% 13C isotopic substitution of the carboxyl carbon...

Scoring permutations of experimental chemical shift deviations and DFT/GIAO calculated deviations of isotropic shieldings for sets of four diastereomers can help to assign their relative configurations. This method was exercised on a set of diastereomeric Cinchona alkaloid derivatives, where 13C NMR data always identified the proper configuration. The presented approach is also an attempt to qu...

Morphological imaging precedes lesion-specific visualization in magnetic resonance imaging (MRI) because of the superior ability of this technique to depict tissue morphology with excellent spatial and temporal resolutions. To achieve lesion-specific visualization of tumors by MRI, we investigated the availability of a novel polymer-based tracer. Although the 13C nucleus is a candidate for a de...

Fourier transform 13C NMR spectra of E. coli tRNA enriched on 13C in either position 2 of adenine (60 atom % 13C) or in position 2 of uracil (82%) and cytosine (63%) were taken at 25.16 MHz over the temperature range 10 degrees - 76 degrees. For C2 of adenine the peak as initially 5 ppm wide, but narrowed to 0.5 ppm as the molecule unfolded. C2 of uracil displayed behavior similar to that of ad...

The formation of monovalent and divalent salt complexes of maduramicin is described and the 13C NMR chemical shift assignments of these materials are tabulated and discussed. In the spectrum of the thallium salt, 20 of the 47 signals are split due to the thallium-carbon coupling. Similarly the preparation of both the free acid and the sodium salt complexes of the normal methyl and ethyl ketal d...