Isotope-enriched proteins

Grzesiek S, Kuboniwa H, Hinck AP, Bax A. Mutiple-quantum line narrowing for measurement of Ha-Hp J couplings in isotopically enriched proteins. J Am Chem Soc 1995 117 5312-5315. 

Proteins that are to be studied by NMR must be specially prepared. Natural proteins almost exclusively contain 12C and 14N, neither of which is an NMR-active isotope. For analysis, the protein must be enriched with 13C and 15N. Isotopically-enriched proteins can be isolated from bacteria that are grown in the presence of 13C-enriched glucose and 15NH4C1. The resulting proteins are then handed off to the NMR experts. 

Montelione GT, Lyons BA, Emerson SD, Tashiro M (1992) An efficient triple resonance experiment using carbon-13 isotropic mixing for determining sequence-specific resonance assignments of isotopically enriched proteins. J Am Chem Soc 114 10974-10975... 

Solid-state NMR experiments for structure determination of uniformly N isotopically enriched proteins have been considered in a minireview by Bockmann." This article highlights the fact that the development of complementary protocols to measure and assign distance restraints has enabled several high-resolution protein structures to be determined by solid-state NMR spectroscopy with a precision approaching that obtained by NMR spectroscopy in solution. 

Solid State NMR Studies of Uniformly Isotopically Enriched Proteins... 

The use of species-specific spiking greatly enhances the traceability of the analytical procedure and improves the reliability of the results. On the other hand, the use of isotopically enriched metalloproteins provides a means to evaluate the analytical conditions, under which the metal center is most stable. Despite all the advantages of species-specific spiking for ICP-MS, it has to be mentioned that huge effort is necessary to produce and characterize an isotopically enriched protein spike. Therefore, this approach might be sensible in practice for the assay of only a few proteins or biomarkers. ... 

Our results do not support the protein stress model. However, this model may apply in cases where stress is intermittent and results in tissue loss, as observed in the study of crows (Hobson and Clark 1992). Low protein levels throughout life after weaning may have produced overall slow and reduced rate of growth rather than tissue loss. Adult rats fed protein-deficient diets after maturation show systematic losses of nitrogen from most tissues that are in proportion to their turnover rates and masses (Uezu et al. 1983). Perhaps tissue nitrogen isotope enrichment may occur under these conditions. New experiments are needed to evaluate this hypothesis. 

Modern Methods for the Expression of Proteins in Isotopically Enriched Form... 

---