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Molecular chaperones are diverse families of proteins that play key roles in protein homeostasis. They assist the folding of client proteins or prevent them from irreversible aggregation under stress conditions. Diverse chaperone families contribute to different aspects of protein homeostasis by interacting with a wide range of client proteins. Despite the vital roles of chaperones in cell survival, the molecular mechanisms underlying chaperone functions remain elusive, due to the non‐specificity of chaperone‐client interactions and the intrinsic flexibility of the clients. Our understanding of the chaperone functional mechanisms, especially regarding chaperone‐client interactions, has greatly expanded in recent years, thanks to the significant contribution from various NMR studies. Solution NMR methods have unique advantages in characterizing disordered protein structures, detecting weak and non‐specific interactions, and probing conformational dynamics of proteins and protein complexes, etc., and therefore are especially powerful in the studies of chaperone structure‐function relationships. In this review, we summarize some of the current knowledge of molecular chaperones, with emphasis on common features of chaperone‐client interactions and examples on a number of specific systems in which solution NMR methods were used to provide essential insights into their functional mechanisms. [ABSTRACT FROM AUTHOR]

A holistic and comparative quality assessment of vinegars from different countries is needed with international trade of vinegar become frequent. In this study, compounds characterization and comparison of commercial-grade Chinese cereal and European grape vinegars were performed using 1H NMR spectroscopy coupled with principal component analysis (PCA) and orthogonal projection to latent structures discriminate analysis (OPLS-DA). The results showed that Balsamic vinegars of Modena were clearly discriminated by higher amount of fructose and glucose, while Chinese aromatic vinegar and aged vinegars were characterized by higher amount of amino acids, volatile compounds, succinate and betaine. On the other hand, flavoring compounds in Chinese rice vinegar and European wine vinegars are less than the others. These characteristic components are associated with the special raw materials and producing process of each types of vinegar and endow them special flavor. The results obtained in this study provide a global insight into vinegar through a 1H NMR based compounds analysis that allows a holistic quality assessment and comparison of vinegars from different manufacture origins. [ABSTRACT FROM AUTHOR]

The influenza fusion peptide located at the N-terminus of the hemagglutinin HA2 subunit initiates the fusing process of the viral membrane with the host cell endosomal membrane. It had been reported that the structure of a 20-residue H3 subtype fusion peptide (H3-HAfp20) was significantly different with that of a H1 subtype 23-residue one (H1-HAfp23). The sequential difference between the 12th and 15th residues of H1 and H3 subtypes could not fully explain the conformational variation. The first and last three amino acids of H3-HAfp23 involved in formation of hydrogen bonds may play an important role in fusion process. To confirm this hypothesis, we investigate the structures of H3-HAfp23 peptide and its mutants, G1S and G1V, in dodecylphosphatidyl choline micelles by using heteronuclear NMR technology. The results demonstrate that, similar to H1-HAfp23 but significantly different with H3-HAfp20, H3-HAfp23 also has tight helical hairpin structure with the N- and C-terminuses linked together because of the hydrogen bonds between Gly1 and the last three amino acids, Trp21-Tyr22-Gly23. Although the 'hemifusion' G1S and lethal G1V mutants have hairpin-like helical structures, the distances between the N- and C-terminuses are increased as shortage of the hydrogen bonds and the larger kink angle between the antiparallel helices. The paramagnetic ion titration experiments show that the terminuses are inserted into the dodecylphosphatidyl choline micelles used as solving media. These may imply that the tight helical hairpin structure, especially the closed conformation at terminus, plays an important role in fusion activity. Copyright © 2014 European Peptide Society and John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]