Electron paramagnetic resonance （EPR） and optical absorption studies were carried out at room temperature on copper doped mixed alkali cadmium phosphate （LiNaCdP） glasses to understand the nature and symmetry of d...Electron paramagnetic resonance （EPR） and optical absorption studies were carried out at room temperature on copper doped mixed alkali cadmium phosphate （LiNaCdP） glasses to understand the nature and symmetry of dopant. Three samples with varying concentrations of alkali ions have been prepared. The spin Harniltonian parameters obtained from room temperature EPR spectra are： gli=2.437, 9⊥=2.096, A‖=117×10-4 cm-1, A⊥=26×10-4 cm-1 for LiNaCdP1, g‖=2.441, g⊥=2.088, A‖=121×10-4 cm-1, A⊥=25×10-4 cm-1 for LiNaCdP2and g‖=2.433,g⊥=2.096, A‖=125×10 4cm-1, A⊥=32×10-4cm-1 for LiNaCdP3. TheseEPR results indicate that the dopant Cu2＋ ion enters the glass matrix into a tetragonally elongated octahedral site. The bonding parameters evaluated by correlating optical and EPR data suggest that bonding between the central metal ion and ligands is partially covalent. The mixed alkali effect in cadmium phosphate glasses was reported.展开更多
A simple theoretical method is introduced for studying the interrelation between electronic and molecular structures.By diagonalizing the 120 × 120 complete energy matrices,the relationships between zero-field sp...A simple theoretical method is introduced for studying the interrelation between electronic and molecular structures.By diagonalizing the 120 × 120 complete energy matrices,the relationships between zero-field splitting （ZFS） parameter D and local distortion parameter △θ for Cr^3＋ ions doped,separately,in α- and β- alums are investigated.Our results indicate that there exists an approximately linear relationship between D and △θ in a temperature range 4.2-297 K and the signs of D and △θ are opposite to each other.Moreover,in order to understand the contribution of spin-orbit coupling coefficient ζ to ZFS parameter D,the relation between D and ζ is also discussed.展开更多
Site-directed spin-labeling with continuous wave electron paramagnetic resonance spectroscopy was used to monitor autoproteolysis of HIV-1 protease, an enzyme essential for viral maturation. Two protein constructs wer...Site-directed spin-labeling with continuous wave electron paramagnetic resonance spectroscopy was used to monitor autoproteolysis of HIV-1 protease, an enzyme essential for viral maturation. Two protein constructs were examined, namely subtype F and the circulating recombinant form CRF01_A/E. As the protease undergoes self-cleavage, protein unfolds and small peptide fragments containing the spin label are generated, which collectively give rise to a sharp spectral component that is easily discernable in the high-field resonance line in the EPR spectrum. By monitoring the intensity of this spectral component over time, the autoproteolytic stability of each construct was characterized under various conditions. Data were collected for samples stored at 4 °C, 25 °C, and 37 °C, and on a subtype F HIV-1 protease sample stored at 25 °C and containing the FDA-approved protease inhibitor Tipranavir. As expected, the rate of autoproteolysis decreased as the storage temperature was lowered. Minimal autoproteolysis was seen for the sample that contained Tipranavir, providing direction for future spectroscopic studies of active protease samples. When compared to standard methods of monitoring protein degradation such as gel electrophoresis or chromatographic analyses, spin-labeling with CW EPR offers a facile, real-time, non-consuming way to monitor autoproteolysis or protein degradation. Additionally, mass spectrometry studies revealed that the N-termini of both constructs are sensitive to degradation and that the sites of specific autoproteolysis vary.展开更多
Penguin and skua in the maritime Antarctic have high salt loadings in the body due to almost exclusive diet consumption of marine invertebrates.However,the storage and turnover of sodium and potassium in these animals...Penguin and skua in the maritime Antarctic have high salt loadings in the body due to almost exclusive diet consumption of marine invertebrates.However,the storage and turnover of sodium and potassium in these animals are poorly investigated.Here we determined the concentration and microscopic distribution of the two elements in the bones of penguin and skua.The average concentrations of sodium and potassium in penguin bone were comparable with that in skua bone（0.18% and 0.82% for penguin bone;0.19% and 0.76% for skua bone in dry weight）.The ratios of sodium to calcium and potassium to calcium（0.0330 and 0.0075 for penguin,0.0335 and 0.0082 for skua in average by weight） were somewhat higher than the reported ratios for terrestrial animals,indicating these marine animals＇ bone enrichment of salt.The ratios of sodium to potassium in average by weight were 6.75 and 4.65 for penguin and skua,respectively.This value is much lower compared with the bulk sea water ratio of about 27.0,implying that potassium is favorable to reside in the bone rather than sodium.Both sodium and potassium were found to significant correlation with the content of organic materials in bone based upon the intensity of native signal determined by electron paramagnetic resonance（EPR）.It was estimated that almost all of potassium is kept within the organic phases,while about 30% of sodium is stored in organic phases and the other 70% within mineral phase.The microscopic distributions of potassium in the cross-section and/or surface were revealed by synchrotron radiation Xray fluorescence（SR-XRF） technique.The ratio of potassium to calcium based upon the SR-XRF intensity counter varied considerably from the surface to the interior,and on the surface the highest concentration of potassium was observed in the middle section with decreasing amounts toward the edge.This indirectly documented that exchange of potassium between fluid and bone organic phase maybe occur.展开更多
文摘Electron paramagnetic resonance （EPR） and optical absorption studies were carried out at room temperature on copper doped mixed alkali cadmium phosphate （LiNaCdP） glasses to understand the nature and symmetry of dopant. Three samples with varying concentrations of alkali ions have been prepared. The spin Harniltonian parameters obtained from room temperature EPR spectra are： gli=2.437, 9⊥=2.096, A‖=117×10-4 cm-1, A⊥=26×10-4 cm-1 for LiNaCdP1, g‖=2.441, g⊥=2.088, A‖=121×10-4 cm-1, A⊥=25×10-4 cm-1 for LiNaCdP2and g‖=2.433,g⊥=2.096, A‖=125×10 4cm-1, A⊥=32×10-4cm-1 for LiNaCdP3. TheseEPR results indicate that the dopant Cu2＋ ion enters the glass matrix into a tetragonally elongated octahedral site. The bonding parameters evaluated by correlating optical and EPR data suggest that bonding between the central metal ion and ligands is partially covalent. The mixed alkali effect in cadmium phosphate glasses was reported.
基金Project supported by the National Natural Science Foundation of China (Grant No 10774103)the Doctoral Education Fund of Education Ministry of China (Grant No 20050610011)
文摘A simple theoretical method is introduced for studying the interrelation between electronic and molecular structures.By diagonalizing the 120 × 120 complete energy matrices,the relationships between zero-field splitting （ZFS） parameter D and local distortion parameter △θ for Cr^3＋ ions doped,separately,in α- and β- alums are investigated.Our results indicate that there exists an approximately linear relationship between D and △θ in a temperature range 4.2-297 K and the signs of D and △θ are opposite to each other.Moreover,in order to understand the contribution of spin-orbit coupling coefficient ζ to ZFS parameter D,the relation between D and ζ is also discussed.
文摘Site-directed spin-labeling with continuous wave electron paramagnetic resonance spectroscopy was used to monitor autoproteolysis of HIV-1 protease, an enzyme essential for viral maturation. Two protein constructs were examined, namely subtype F and the circulating recombinant form CRF01_A/E. As the protease undergoes self-cleavage, protein unfolds and small peptide fragments containing the spin label are generated, which collectively give rise to a sharp spectral component that is easily discernable in the high-field resonance line in the EPR spectrum. By monitoring the intensity of this spectral component over time, the autoproteolytic stability of each construct was characterized under various conditions. Data were collected for samples stored at 4 °C, 25 °C, and 37 °C, and on a subtype F HIV-1 protease sample stored at 25 °C and containing the FDA-approved protease inhibitor Tipranavir. As expected, the rate of autoproteolysis decreased as the storage temperature was lowered. Minimal autoproteolysis was seen for the sample that contained Tipranavir, providing direction for future spectroscopic studies of active protease samples. When compared to standard methods of monitoring protein degradation such as gel electrophoresis or chromatographic analyses, spin-labeling with CW EPR offers a facile, real-time, non-consuming way to monitor autoproteolysis or protein degradation. Additionally, mass spectrometry studies revealed that the N-termini of both constructs are sensitive to degradation and that the sites of specific autoproteolysis vary.
基金supported by grants fromthe National Natural Science Foundation of China(project nos.40776001 and 40306001)the Foundation for the Author of National Excellent Doctoral Dissertation of China(grant200354)+2 种基金the Ministry of Education of China,and the Chinese Academy of Sciencessupported by the Chinese Arctic and Antarctic AdministrationSRXRF experiment is supported by BSRF
文摘Penguin and skua in the maritime Antarctic have high salt loadings in the body due to almost exclusive diet consumption of marine invertebrates.However,the storage and turnover of sodium and potassium in these animals are poorly investigated.Here we determined the concentration and microscopic distribution of the two elements in the bones of penguin and skua.The average concentrations of sodium and potassium in penguin bone were comparable with that in skua bone（0.18% and 0.82% for penguin bone;0.19% and 0.76% for skua bone in dry weight）.The ratios of sodium to calcium and potassium to calcium（0.0330 and 0.0075 for penguin,0.0335 and 0.0082 for skua in average by weight） were somewhat higher than the reported ratios for terrestrial animals,indicating these marine animals＇ bone enrichment of salt.The ratios of sodium to potassium in average by weight were 6.75 and 4.65 for penguin and skua,respectively.This value is much lower compared with the bulk sea water ratio of about 27.0,implying that potassium is favorable to reside in the bone rather than sodium.Both sodium and potassium were found to significant correlation with the content of organic materials in bone based upon the intensity of native signal determined by electron paramagnetic resonance（EPR）.It was estimated that almost all of potassium is kept within the organic phases,while about 30% of sodium is stored in organic phases and the other 70% within mineral phase.The microscopic distributions of potassium in the cross-section and/or surface were revealed by synchrotron radiation Xray fluorescence（SR-XRF） technique.The ratio of potassium to calcium based upon the SR-XRF intensity counter varied considerably from the surface to the interior,and on the surface the highest concentration of potassium was observed in the middle section with decreasing amounts toward the edge.This indirectly documented that exchange of potassium between fluid and bone organic phase maybe occur.
