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
GuiLingJi(GLJ),a classic traditional Chinese medicine(TCM)formula,is composed of over 20 herbs,according to the Pharmacopeia of the People's Republic of China.Owing to its various activities,GLJ has been used in c...GuiLingJi(GLJ),a classic traditional Chinese medicine(TCM)formula,is composed of over 20 herbs,according to the Pharmacopeia of the People's Republic of China.Owing to its various activities,GLJ has been used in clinical settings for more than 400 years in China.However,the ambiguous chemical material basis limits the development of studies on the quality control and pharmacological mechanisms of GLJ.Therefore,comprehensive characterization of the multiple chemical components of GLJ is of great significance for the modernization of this formula.Given the great variety of herbs in GLJ,both UHPLCMS and ^(1)H NMR techniques were employed in this study.In addition,solvent extraction with different polarities was used to eliminate signal interference and the concentration of trace components.A variety of MS analytic methods were also used,including implementation of a self-built compound database,diagnostic ion filtering,mass defect filtering,and Compound Discoverer 3.0 analysis software.Based on the above strategies,a total of 150 compounds were identified,including 5 amino acids,13 phenolic acids and glycosides,11 coumarins,72 flavones,20 triterpenoid and triterpenoid saponins,23 fatty acids,and 6 other compounds.Moreover,13 compounds were identified by ^(1)H NMR spectroscopy.The UHPLC-MS and ^(1)H NMR results supported and complemented each other.This strategy provides a rapid approach to analyzing and identifying the chemical composition of Chinese herbal prescriptions.The current study provides basis for further research on the quality control and pharmacological mechanism of GLJ.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.
基金support from the Shanxi Provincial Science and Technology Key Research and Development Plan(Grant Nos.:201603D3113006 and 201903D311012)。
文摘GuiLingJi(GLJ),a classic traditional Chinese medicine(TCM)formula,is composed of over 20 herbs,according to the Pharmacopeia of the People's Republic of China.Owing to its various activities,GLJ has been used in clinical settings for more than 400 years in China.However,the ambiguous chemical material basis limits the development of studies on the quality control and pharmacological mechanisms of GLJ.Therefore,comprehensive characterization of the multiple chemical components of GLJ is of great significance for the modernization of this formula.Given the great variety of herbs in GLJ,both UHPLCMS and ^(1)H NMR techniques were employed in this study.In addition,solvent extraction with different polarities was used to eliminate signal interference and the concentration of trace components.A variety of MS analytic methods were also used,including implementation of a self-built compound database,diagnostic ion filtering,mass defect filtering,and Compound Discoverer 3.0 analysis software.Based on the above strategies,a total of 150 compounds were identified,including 5 amino acids,13 phenolic acids and glycosides,11 coumarins,72 flavones,20 triterpenoid and triterpenoid saponins,23 fatty acids,and 6 other compounds.Moreover,13 compounds were identified by ^(1)H NMR spectroscopy.The UHPLC-MS and ^(1)H NMR results supported and complemented each other.This strategy provides a rapid approach to analyzing and identifying the chemical composition of Chinese herbal prescriptions.The current study provides basis for further research on the quality control and pharmacological mechanism of GLJ.
