The normally underused ^1H-^15N HMBC spectra of thirteen C18-diterpenoid alkaloids have been determined for the first time. As a result, the significant effects of the substituents of nitrogen atoms, the conformations...The normally underused ^1H-^15N HMBC spectra of thirteen C18-diterpenoid alkaloids have been determined for the first time. As a result, the significant effects of the substituents of nitrogen atoms, the conformations of A ring, and protonation, on the nitrogen-15 chemical shifts are demonstrated.展开更多
THE ~15N NMR study is of general interest in the analysis of the protein conformations in solu-tions. When NMR is applied to the conformation study of macrobiomolecules, a heteronuclearmultiple quantum coherence (HMQC...THE ~15N NMR study is of general interest in the analysis of the protein conformations in solu-tions. When NMR is applied to the conformation study of macrobiomolecules, a heteronuclearmultiple quantum coherence (HMQC) spectrum of ~15N is usually measured first, so that theamide protons are assigned before other experiments, such as the total correlation展开更多
Apramycin is unique in the aminoglycoside family due to its octodiose moiety. However, either the biosynthesis process or the precursors involved are largely unknown. Addition of glycine, as well as serine or threonin...Apramycin is unique in the aminoglycoside family due to its octodiose moiety. However, either the biosynthesis process or the precursors involved are largely unknown. Addition of glycine, as well as serine or threonine, to the Streptomyces tenebrabrius UD2 fermentation medium substantially increases the production of apramycin with little effect on the growth of mycelia, indicating that glycine and/or serine might be involved in the biosynthesis of apramycin. The 13C-NMR analysis of [2-13C] glycine-fed (25% enrichment) apramycin showed that glycine specifically and efficiently incorporated into the only N-CH3 substituent of apramycin on the C7′ of the octodiose moiety. We noticed that the in vivo concentration of S-adenosyl methionine increased in parallel with the addition of glycine, while the addition of methione in the fermentation medium significantly decreased the productivity of apra-mycin. Therefore, the methyl donor function of glycine is proposed to be involved in the methionine cycle but methionine itself was proposed to inhibit the methylation and methyl transfer processes as previously reported for the case of rapamycin. The 15N NMR spectra of [2-13C,15N]serine labeled apramycin indicated that serine may also act as a limiting precursor contributing to the ―NH2 substituents of apramycin.展开更多
基金the National Natural Science Foundation of China (No.81273387) for the financial support of this research
文摘The normally underused ^1H-^15N HMBC spectra of thirteen C18-diterpenoid alkaloids have been determined for the first time. As a result, the significant effects of the substituents of nitrogen atoms, the conformations of A ring, and protonation, on the nitrogen-15 chemical shifts are demonstrated.
文摘THE ~15N NMR study is of general interest in the analysis of the protein conformations in solu-tions. When NMR is applied to the conformation study of macrobiomolecules, a heteronuclearmultiple quantum coherence (HMQC) spectrum of ~15N is usually measured first, so that theamide protons are assigned before other experiments, such as the total correlation
文摘Apramycin is unique in the aminoglycoside family due to its octodiose moiety. However, either the biosynthesis process or the precursors involved are largely unknown. Addition of glycine, as well as serine or threonine, to the Streptomyces tenebrabrius UD2 fermentation medium substantially increases the production of apramycin with little effect on the growth of mycelia, indicating that glycine and/or serine might be involved in the biosynthesis of apramycin. The 13C-NMR analysis of [2-13C] glycine-fed (25% enrichment) apramycin showed that glycine specifically and efficiently incorporated into the only N-CH3 substituent of apramycin on the C7′ of the octodiose moiety. We noticed that the in vivo concentration of S-adenosyl methionine increased in parallel with the addition of glycine, while the addition of methione in the fermentation medium significantly decreased the productivity of apra-mycin. Therefore, the methyl donor function of glycine is proposed to be involved in the methionine cycle but methionine itself was proposed to inhibit the methylation and methyl transfer processes as previously reported for the case of rapamycin. The 15N NMR spectra of [2-13C,15N]serine labeled apramycin indicated that serine may also act as a limiting precursor contributing to the ―NH2 substituents of apramycin.
