Lianglin Zhang,Shuwei Lin,Yi Li,Baozong Li,Yonggang Yang
Four Ala–Ala dipeptides with a semi-perfluoroalkyl chain were synthesized. The intermolecular hydrogen bonding among amide groups and carboxyl groups as well as the hydrophobic association of semi-perfluoroalkyl chains drove the self-assembly of dipeptides. Homochiral dipeptides were able to self-assemble into coiled nanoribbons in a mixed solvent of DMSO/H2O (5/5, v/v), while entangled twisted nanofibers formed for heterochiral ones in a mixed solvent of DMSO/H2O (4/6, v/v). The handedness of self-assemblies and the stacking chirality of phenylene groups were controlled by the chirality of the alanine residue at the C-terminal. The vibration circular dichroism investigation indicated that the helicity of the semi-perfluoroalkyl chain was controlled by the handedness of dipeptide self-assemblies. The X-ray diffraction study showed that homochiral and heterochiral dipeptides underwent distinct molecular packing during the self-assembly. Our results clearly demonstrated that, through supramolecular self-assembly, the chirality transferred from the amino acid building block to the self-assemblies and eventually to the semi-perfluoroalkyl chain.
Shuwei Lin,Qiyun Tong,Pan Jiang,Baozong Li,Yi Li,Yonggang Yang
Three dipeptides based on the Ala–Ala building block with different substituent positions of the dodecyloxy group on the benzoyl residue at the N terminus were designed and synthesized (ortho-, meta- and para-16). All of them were able to spontaneously self-assemble in the mixed solvent of methanol and water (6/4, v/v). However, three dipeptides underwent a distinct kinetically controlled self-assembling process. The spectroscopic study also revealed that, for ortho-16, the phenylene groups and the peptide sequence loosely packed, while meta- and para-16 stacked into well-ordered structures with the formation of parallel β-sheets through supramolecular self-assembly. Intramolecular hydrogen bonding and steric hindrance of the dodecyloxy side chain were proposed to lead to the different self-assembling behaviour of the three isomers.
The effect of steaming treatment on salmon quality was explored by different multi-omics and electronic sensory system in this study. A comparison between conventional steaming (CS) and anaerobic steaming (AS) was conducted in organoleptic quality of salmon. Twelve key volatile compounds were identified, which contributed to the flavor difference. The concentrations of hexanal, (E)-2-octen-1-al, and decanal in AS salmon were significantly lower than in CS salmon, which account for 68.9–80.5 % of the latter. During steaming, the fatty acids and diacylglycerols decreased significantly by 37.4 % and 57.9 %, respectively. Anaerobic steaming limited the degradation of some oxidized lipids, further reduced some volatile secondary oxidation products. Nucleotides and derivatives, succinic acid, glutamic acid, hydroxyproline and betaine contributed to the saltness, umami, richness of steamed salmon. Metabolomics data revealed that the higher creatinine, Ala-Ala and Ala-Leu provided more umami and less bitterness to AS salmon.
危险品化学品经营许可证（带存储）