Nitrogen-14(^(14)N)overtone(OT)spectroscopy under fast magic angle spinning(MAS)conditions(>60 kHz)has emerged as a powerful technique for observing correlations and distances between ^(14)N and ^(1)H,owing to the ...Nitrogen-14(^(14)N)overtone(OT)spectroscopy under fast magic angle spinning(MAS)conditions(>60 kHz)has emerged as a powerful technique for observing correlations and distances between ^(14)N and ^(1)H,owing to the absence of the first-order quadrupolar broadenings.In addition,^(14)N^(OT) allows selective manipulation of ^(14)N nuclei for each site.Despite extensive theoretical and experimental studies,the spin dynamics of ^(14)N^(OT) remains under debate.In this study,we conducted experimental investigations to assess the spin dynamics of ^(14)N^(OT) using the rotational-echo saturation-pulse double-resonance(RESPDOR)sequence,which monitors population transfer induced by a^(14)N^(OT) pulse.The ^(14)N^(OT) spin dynamics is well represented by a model of a two-energy-level system.Unlike spin-1/2,the maximum excitation efficiency of ^(14)N^(OT) coherences of powdered solids,denoted by p,depends on the radiofrequency field(rf-field)strength due to orientation dependence of effective nutation fields even when pulse lengths are optimized.It is also found that the p factor,contributing to the ^(14)N^(OT) spin dynamics,is nearly independent of the B0 field.Consequently,the filtering efficiency of RESPDOR experiments exhibits negligible dependence on B0 when the ^(14)N^(OT) pulse length is optimized.The study also identifies the optimal experimental conditions for ^(14)N^(OT)/^(1)H RESPDOR correlation experiments.展开更多
Bile acids are the main body of enterohepatic circulation in vivo.They have essential functions such as emulsifying fat,bacteriostasis and regulating multiple metabolic pathways as signal molecules.However,the assignm...Bile acids are the main body of enterohepatic circulation in vivo.They have essential functions such as emulsifying fat,bacteriostasis and regulating multiple metabolic pathways as signal molecules.However,the assignments of NMR signals for some lowconcentration bile acids are still needed.This study combined 1D nuclear magnetic resonance(NMR)and 2D NMR techniques including 1He1H correlation spectroscopy(COSY),1He1H total correlation spectroscopy(TOCSY),1H J-resolved spectroscopy(J-Res),1He13C heteronuclear single quantum coherence spectroscopy(HSQC),and 1He13C heteronuclear multiple bond correlation spectroscopy(HMBC)to assign the 1H and 13C signals of six bile acids in aqueous solution at physiological pH(~7.4)and nine bile acids in methanol.These data are of importance to the NMR-based studies on lipid digestion,absorption,and metabolism.展开更多
用原子电性距离矢量(atom ic electronegativity d istance vector,AEDV)和原子杂化状态指数(atom ic hybrid i-zation state index,AHSI)对13个雄甾烯酮化合物中247个碳原子进行了结构表征,并与其核磁共振碳谱(13CNMR)建立了多元线性...用原子电性距离矢量(atom ic electronegativity d istance vector,AEDV)和原子杂化状态指数(atom ic hybrid i-zation state index,AHSI)对13个雄甾烯酮化合物中247个碳原子进行了结构表征,并与其核磁共振碳谱(13CNMR)建立了多元线性定量构谱相关(QSSR)模型;运用逐步回归结合统计检测,对模型变量进行了筛选,建模计算值、留一法(leave-one-out,LOO)交互校验(cross-validation,CV)预测值和留分法(leave-molecu le-out,LMO)交互校验预测值的复相关系数(R)分别为0.989 6,0.989 1和0.989 4。结果表明:AEDV,AHSI与13CNMR谱化学位移显著相关。展开更多
文摘Nitrogen-14(^(14)N)overtone(OT)spectroscopy under fast magic angle spinning(MAS)conditions(>60 kHz)has emerged as a powerful technique for observing correlations and distances between ^(14)N and ^(1)H,owing to the absence of the first-order quadrupolar broadenings.In addition,^(14)N^(OT) allows selective manipulation of ^(14)N nuclei for each site.Despite extensive theoretical and experimental studies,the spin dynamics of ^(14)N^(OT) remains under debate.In this study,we conducted experimental investigations to assess the spin dynamics of ^(14)N^(OT) using the rotational-echo saturation-pulse double-resonance(RESPDOR)sequence,which monitors population transfer induced by a^(14)N^(OT) pulse.The ^(14)N^(OT) spin dynamics is well represented by a model of a two-energy-level system.Unlike spin-1/2,the maximum excitation efficiency of ^(14)N^(OT) coherences of powdered solids,denoted by p,depends on the radiofrequency field(rf-field)strength due to orientation dependence of effective nutation fields even when pulse lengths are optimized.It is also found that the p factor,contributing to the ^(14)N^(OT) spin dynamics,is nearly independent of the B0 field.Consequently,the filtering efficiency of RESPDOR experiments exhibits negligible dependence on B0 when the ^(14)N^(OT) pulse length is optimized.The study also identifies the optimal experimental conditions for ^(14)N^(OT)/^(1)H RESPDOR correlation experiments.
文摘Bile acids are the main body of enterohepatic circulation in vivo.They have essential functions such as emulsifying fat,bacteriostasis and regulating multiple metabolic pathways as signal molecules.However,the assignments of NMR signals for some lowconcentration bile acids are still needed.This study combined 1D nuclear magnetic resonance(NMR)and 2D NMR techniques including 1He1H correlation spectroscopy(COSY),1He1H total correlation spectroscopy(TOCSY),1H J-resolved spectroscopy(J-Res),1He13C heteronuclear single quantum coherence spectroscopy(HSQC),and 1He13C heteronuclear multiple bond correlation spectroscopy(HMBC)to assign the 1H and 13C signals of six bile acids in aqueous solution at physiological pH(~7.4)and nine bile acids in methanol.These data are of importance to the NMR-based studies on lipid digestion,absorption,and metabolism.
文摘用原子电性距离矢量(atom ic electronegativity d istance vector,AEDV)和原子杂化状态指数(atom ic hybrid i-zation state index,AHSI)对13个雄甾烯酮化合物中247个碳原子进行了结构表征,并与其核磁共振碳谱(13CNMR)建立了多元线性定量构谱相关(QSSR)模型;运用逐步回归结合统计检测,对模型变量进行了筛选,建模计算值、留一法(leave-one-out,LOO)交互校验(cross-validation,CV)预测值和留分法(leave-molecu le-out,LMO)交互校验预测值的复相关系数(R)分别为0.989 6,0.989 1和0.989 4。结果表明:AEDV,AHSI与13CNMR谱化学位移显著相关。
