Over the last decade, a wide variety of new foods have been introduced into the global marketplace, many with health benefits that exceed those of traditional foods. Simultaneously, a wide range of analytical technologies has evolved that allow greater capability for the determination of food composition. Nuclear magnetic resonance (NMR), traditionally a research tool used for structural elucidation, is now being used frequently for metabolomics and chemical fingerprinting. Its stability and inherent ease of quantification have been exploited extensively to identify and quantify bioactive components in foods and dietary supplements. In addition, NMR fingerprints have been used to differentiate cultivars, evaluate sensory properties of food and investigate the influence of growing conditions on food crops. Here we review the latest applications of NMR in food analysis. Published 2016. This article is a U.S. Government work and is in the public domain in the USA.
The cDNA of UVI31+ was cloned from C. reinhardtii and expressed in E. coli from where the protein was purified to homogeneity. The purified protein exhibited beta-lactamase activity (Manuscript in preparation). However, UVI31+ has no homology with the known β-lactamases. In order to understand the structural basis of the ability of UVI31+ to hydrolyze β-lactam antibiotics, we in parallel, set out to structurally characterize it by NMR. Its β-lactamase activity in relation to the solution structure by NMR is likely to provoke deeper understanding of its mechanism and facilitate the rationalization of other functions of the protein, if any. In this endeavor, we report almost complete sequence-specific backbone (1)H, (13)C and (15)N NMR assignments of UVI31+.
Neuronal calcium sensor-1 (NCS-1) interacts with many membranes and cytosolic proteins, both in a Ca(2+)-dependent and in a Ca(2+)-independent manner, and its physiological role is governed by its N-terminal myristoylation. To understand the role of myristoylation in altering Ca(2+) response and other basic biophysical properties, we have characterized the Ca(2+) filling pathways in both myristoylated (myr) and non-myristoylated (non-myr) forms of NCS-1. We have observed that Ca(2+) binds simultaneously to all three active EF-hands in non-myr NCS-1, whereas in the case of myr NCS-1, the process is sequential, where the second EF-hand is filled first, followed by the third and fourth EF-hands. In the case of myr NCS-1, the observed sequential Ca(2+) binding process becomes more prominent in the presence of Mg(2+). Besides, the analysis of (15)N-relaxation data reveals that non-myr NCS-1 is more dynamic than myr NCS-1. The overall molecular tumbling correlation time increases by approximately 20% upon myristoylation. Comparing the apo forms of non-myr NCS-1 and myr NCS-1, we found the possibility of existence of some substates, which are structurally closer to the holo form of the protein. There are more such substates in the case of non-myr NCS-1 than in the case of the myr NCS-1, suggesting that the former accesses larger volumes of conformational substates compared with the latter. Further, the study reveals that the possibility of Ca(2+) binding simultaneously to different parts of the protein is more favourable in non-myr NCS-1 than in myr NCS-1.
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