A detailed analysis of backbone amide NH chemical shift temperature gradients (∆δ/∆T values) for proteins and highly cross-linked peptides reveals that hydrogen-bonded exchange-protected NHs are characterized by ∆δ/∆T values of -2.0 ( 1.4 ppb/°C while exposed NHs typically display gradients of -6.0 f -8.5 ppb/°C; however, numerous exceptions to these generalizations occur. For partially folded peptides (rather than proteins), exceptions are more common than concordance with this rule; ∆δ/∆T values ranging from -28 to +12 ppb/°C have been observed. In the case of the peptide systems for which exchange protection data is available, the common practice of assuming that a ∆δ/∆T value less negative than -4 ppb/°C indicates that the NH is sequestered from solvent is shown to have zero predictive validity. The analysis of the data for partially folded peptides, protein fragments, and other peptides which are expected to display minimal structuring reveals a significant correlation between ∆δ/∆T and the deviation of δ NH from the random coil reference shift. The analysis was facilitated by plotting NH chemical shift deviations (NH-CSD) Versus the ∆δ/∆T values. Using such plots, slow-exchanging hydrogen-bonded sites in proteins can be determined with much higher confidence than using the value of the gradient alone. For peptides, the occurrence of large shift deviations and abnormal gradients are diagnostic for partial structuring at lower temperatures which becomes increasingly randomized on warming. A good correlation coefficient (R g 0.75) for NH-CSD and ∆δ/∆T values indicates that essentially all of the NH shift deviation from reference values is due to the concerted formation of a single structured state on cooling. Correlation coefficients greater than 0.95 were observed for both helix and -hairpin forming peptides. The slope of the correlation plot (parts per thousand/°C) is a measure of the decrease in the population of the structured state upon warming. A detailed model which rationalizes the effects of conformational equilibria upon NH shifts is presented. A positive ∆Cp for unfolding is required to rationalize the linearity of δ NH with temperature that is routinely observed for partially structured peptides. This analysis suggests that ordered states of short peptides achieve significant populations in water only when the hydrophobic effect favors the structured state. This conclusion is pertinent to the current questions concerning the temporal sequence of secondary Versus tertiary structure formation during protein folding. Further, it is suggested that the use of NMR parameters (scalar and dipolar couplings) to derive the structural preferences of protein fragments which might serve a "seeding" role in the folding pathway is justified only when the CSD/gradient plot displays both a correlation coefficient greater than 0.70 and significant NH-CSD values (|CSD| > 0.3).With the development of 2D NMR methods, peptide/protein structure elucidation has been dominated by methods based on NOE-derived distance const...
The phase diagrams of the CH 3 CH 2 OH + Cs 2 SO 4 + H 2 O system were determined at (10, 30, and 50) °C. The binodal curves were given using a five-parameter equation. The tie lines were correlated by the Othmer-Tobias and Bancroft equations. Samples of the solid phase analyzed by thermogravimetric analysis showed that it was the anhydrous salt.
Distributed Internet of things (IoT) is becoming an important technology with the popularization of intelligent devices, which builds a bridge between physical networks and social networks. Therefore, how to ensure the security of IoT is an urgent problem. As an effective measure to improve physical layer security, cooperative jamming has been extensively adopted to reduce the eavesdropper's ability to listen to the transmitted signals. Over the past decades, there has been lots of research on cooperative jamming in the single physical layer network. Meanwhile, some works use game theory to analyze the strategies of jammers and legitimate channels. However, these studies assume that the system is ideal and static, which does not conform to the real-world environment. On the other hand, they often ignore the social relationships that exist in the network, nor do they consider the impact of social relationships on the game. In this paper, we first establish a two-layer network model, which includes a physical layer and a social layer. Then we combine a two-layer network with game theory. In the single jamming node scenario, the jamming node is the leader and the legitimate channel is the follower, so we establish a Stackelberg game. Noting the influence of social strength on the game, we rewrite the benefit function of the jamming node. Our experiment results show the relationship between a legitimate channel's benefit and its purchase power quantity. At the same time, we can find those good social relationships can significantly improve the security rate of the communication system.
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