The linear relationship between the chemical shift of the resenant nucleus and the localvan der Waals steric energy calculated by molecular mechanics with MM2 force field wasextended to various organophosphorus compou...The linear relationship between the chemical shift of the resenant nucleus and the localvan der Waals steric energy calculated by molecular mechanics with MM2 force field wasextended to various organophosphorus compounds including alkyl-phosphates, -phosphonates,-phosphinates as well as -phosphine oxides. The conformational equilibria of a series of alkylO,O-1,3--propylene-and O, O-1,4-butylenephosphonates were studied by the molecular mechanicscalculations and the dynamic ^(31)P NMR spectroscopic method. As shown by these experimentaldata, the former existed in a chair form, and the latter in a twist boat form with an equatorialalkyl group in both configurations, either in gaseous state or in non-polar solvent.展开更多
Alpine tundra ecosystems have specific vegetation and environmental conditions that may affect soil phosphorus （P） composition and phosphatase activities. However, these effects are poody understood. This study used...Alpine tundra ecosystems have specific vegetation and environmental conditions that may affect soil phosphorus （P） composition and phosphatase activities. However, these effects are poody understood. This study used NaOH-EDTA extraction and solution ^31P nuclear magnetic resonance （NMR） spectroscopy to determine soil P composition and phosphatase activities, including acid phosphomonoesterase （AcP）, phosphodiesterase （PD） and inorganic pyrophosphatase （IPP）, in the alpine tundra of the Changbai Mountains at seven different altitudinal gradients （i.e., 2000 m, 2100 m, 2200 m, 2300 m, 2400 m, 2500 m, and 2600 m）. The results show that total P （TP）, organic P （OP）, OP/TP, NaOH-EDTA extracted P and AcP, PD, and IPP activities over the altitude range of 2500-2600 m are significantly lower than those below 2400 m. The dominant extracted form of P is OP （73%0-83%） with a large proportion of monoesters （65%0-72%）, whereas inorganic P is present in lower proportions （17%-27%）. The activity of AcP is significantly positively correlated with the contents of soil OP, total carbon （TC）, total nitrogen （TN）, and TP （P 〈 0.05）, indicating that the AcP is a more sensitive index for responding P nutrient storage than PD and IPP. Soil properties, P composition, and phosphatase activities decrease with increased altitude and soil pH. Our results indicate that the distribution of soil P composition and phosphatase activities along altitude and AcP may play an important role in P hydrolysis as well as have the potential to be an indicator of soil quality.展开更多
文摘The linear relationship between the chemical shift of the resenant nucleus and the localvan der Waals steric energy calculated by molecular mechanics with MM2 force field wasextended to various organophosphorus compounds including alkyl-phosphates, -phosphonates,-phosphinates as well as -phosphine oxides. The conformational equilibria of a series of alkylO,O-1,3--propylene-and O, O-1,4-butylenephosphonates were studied by the molecular mechanicscalculations and the dynamic ^(31)P NMR spectroscopic method. As shown by these experimentaldata, the former existed in a chair form, and the latter in a twist boat form with an equatorialalkyl group in both configurations, either in gaseous state or in non-polar solvent.
基金National Natural Science Foundation of China(No.41171241)
文摘Alpine tundra ecosystems have specific vegetation and environmental conditions that may affect soil phosphorus （P） composition and phosphatase activities. However, these effects are poody understood. This study used NaOH-EDTA extraction and solution ^31P nuclear magnetic resonance （NMR） spectroscopy to determine soil P composition and phosphatase activities, including acid phosphomonoesterase （AcP）, phosphodiesterase （PD） and inorganic pyrophosphatase （IPP）, in the alpine tundra of the Changbai Mountains at seven different altitudinal gradients （i.e., 2000 m, 2100 m, 2200 m, 2300 m, 2400 m, 2500 m, and 2600 m）. The results show that total P （TP）, organic P （OP）, OP/TP, NaOH-EDTA extracted P and AcP, PD, and IPP activities over the altitude range of 2500-2600 m are significantly lower than those below 2400 m. The dominant extracted form of P is OP （73%0-83%） with a large proportion of monoesters （65%0-72%）, whereas inorganic P is present in lower proportions （17%-27%）. The activity of AcP is significantly positively correlated with the contents of soil OP, total carbon （TC）, total nitrogen （TN）, and TP （P 〈 0.05）, indicating that the AcP is a more sensitive index for responding P nutrient storage than PD and IPP. Soil properties, P composition, and phosphatase activities decrease with increased altitude and soil pH. Our results indicate that the distribution of soil P composition and phosphatase activities along altitude and AcP may play an important role in P hydrolysis as well as have the potential to be an indicator of soil quality.
