Chitosan （CS） is expected to be an ideal gene carrier for its high biosafety. In this work, CS with low molecular weight were prepared through the γ-ray radiation on the acetic acid solution of CS. The CS chains we...Chitosan （CS） is expected to be an ideal gene carrier for its high biosafety. In this work, CS with low molecular weight were prepared through the γ-ray radiation on the acetic acid solution of CS. The CS chains were scissioned under the γ-ray radiation, and the molecu- lar weight （MW） of CS decreased with the absorbed dose. When the absorbed dose was above 30 kGy, the molecular weight of CS decreased about an order of magnitude. The γ-ray-radiation-scissioned CS can effectively bind with plasmid （pEGFP） through complex coacervation method, forming pEGFP/γ-ray-radiation-scissioned CS complex particles with a size of 200-300 nm. The complex particles have good stability and little cytotoxicity. The in vitro gene transfection efficiencies of the pEGFP/γ-ray-radiation-scissioned CS complex particles were investigated by fluorescence microscope and flow cytometry. The results showed that the gene vectors using γ-ray-radiation-scissioned CS as the carrier will possess better gene transfection efficiency than those using natural high-MW CS as the carrier. The higher the absorbed dose, the smaller the MW of CS and the better transfection efficiency of the corresponding gene vector. This work provides a green and simple method on the preparation of CS-based gene vectors with high efficiency and biosafety.展开更多
The present study was designed to investigate the bioactive constituents ofXanthoceras sorbifolia in terms of amounts and their antioxidant, DNA scissiou protection, and ct-glucosidase inhibitory activities. Simultane...The present study was designed to investigate the bioactive constituents ofXanthoceras sorbifolia in terms of amounts and their antioxidant, DNA scissiou protection, and ct-glucosidase inhibitory activities. Simultaneous quantification of 10 X. sorbifolia constituents was carried out by a newly established ultra-high performance liquid chromatography-quadrupole mass spectrometry method （UHPLC-MS）, The antioxidant activities were evaluated by measuring DPPH radical scavenging and DNA scission protective activities. The a-glucosidase inhibitory activities were investigated by using an assay with a-glucosidase from Bacillus Stearothermophilus and disaccharidases from mouse intestine. We found that the wood ofX. sorbifolia was rich in phenolic compounds with the contents of catechin, epicatechin, myricetin, and dihydromyricetin being 0.12-0.19, 1.94-2.16, 0.77-0.91, and 6.76-7.89 mg.g-1, respectively. The four constituents strongly scavenged DPPH radicals （with ECs0 being 4.2, 3.8 and 5.7 μg-mL-1, respectively） and remarkably protected peroxyl radical-induced DNA strand scission （92.10%, 94.66%, 75.44% and 89.95% of protection, respectively, at a concentration of 10 μmol.L-1）. A dimeric flavan 3-ol, epigallocatechin-（4β→8, 2β→O-7）-epicatechin potently inhibited a-glucosidase with an IC50 value being as low as 1.2 μg.mL1. The established UHPLC-MS method could serve as a quality control tool for X. sorbifolia. In conclusion, the high contents of antioxidant and α-glucosidase inhibitory constituents in X. sorbifolia support its use as complementation of other therapeutic agents for metabolic disorders, such as diabetes and hypertension.展开更多
3-Methoxy-, 3, 5-dimethoxy-, and 3-phenyl-4-hydroxyacetophenones suffered alkyl carbonyl C-C bond scission to yield 4-hydroxybenzoate esters and 4-isopropenylphenols under standard conditions of ethylene ketal formati...3-Methoxy-, 3, 5-dimethoxy-, and 3-phenyl-4-hydroxyacetophenones suffered alkyl carbonyl C-C bond scission to yield 4-hydroxybenzoate esters and 4-isopropenylphenols under standard conditions of ethylene ketal formation; the latter underwent in situ dimerization, cyclization, and rearrangement to give substituted indanols. The isopropenylphenol derived from 3,5-ditertbutyl-4-hydroxyacetophenone did not dimerize but condensed with its precursor to yield a substituted diphenylpropanone. 3-nitro-, 3,5-dinitro-, and 3,5-dibromo-4-hydroxyacetophenones on the other hand reacted normally to give ethylene ketals in good yields.展开更多
The fission fragment mass-yields are evaluated for pre-actinide and actinide isotopes using a systematic statistical scission point model.The total potential energy of the fissioning systems at the scission point is p...The fission fragment mass-yields are evaluated for pre-actinide and actinide isotopes using a systematic statistical scission point model.The total potential energy of the fissioning systems at the scission point is presented in approximate relations as functions of mass numbers,deformation parameters and the temperature of complementary fission fragments.The collective temperature,Tcoll,and the temperature of fission fragments,Ti,are separated and the effect of collective temperature on mass yields results is investigated.The fragment temperature has been calculated with the generalized superfluid model.The sum of deformation parameters of complementary fission fragments has been obtained by fitting the calculated results with the experimental data.To investigate the transitions between symmetric and asymmetric modes mass yields for pre-actinide and heavy actinides are calculated with this model.The transition from asymmetric to symmetric fission is well reproduced using this systematic statistical scission point model.The calculated results are in good agreement with the experimental data with Tcoll=2 Me V at intermediate excitation energy and with T_(coll)=1MeV for spontaneous fission.Despite the Langevin model,in the scission point model,a constraint on the deformation parameters of fission fragments has little effect on the results of the mass yield.展开更多
A new statistical method for systematizing the nuclei fission fragments, investigation of their mass and charge spectra and neutron fission parameters has been suggested. In proposed method, the mass and charge yields...A new statistical method for systematizing the nuclei fission fragments, investigation of their mass and charge spectra and neutron fission parameters has been suggested. In proposed method, the mass and charge yields of nucleons are determined from the equilibrium conditions of the nuclear fragments post-fission ensemble. Here we consider protons and neutrons of different fragments as statistically non-equivalent. The abilities of the proposed statistical method for explanation of the U, Pa, Th, Ac and Ra post-fission fragments ordering and neutron emission function calculation have been demonstrated.展开更多
Methyl, ethyl, n-propyl, and benzyl p-hydroxyphenyl ketones and 6-hydroxy-1-tetralone are shown under the condition of ethylene ketal formation to undergo alkyl-carbonyl C-C bondscission, but not with p-hydroxybenzoph...Methyl, ethyl, n-propyl, and benzyl p-hydroxyphenyl ketones and 6-hydroxy-1-tetralone are shown under the condition of ethylene ketal formation to undergo alkyl-carbonyl C-C bondscission, but not with p-hydroxybenzophenone, p-hydroxyisobutyrophenone, and 5-hydroxy-1-indanone. It is suggested that the scissiou is preceded by an aldol condensation.展开更多
The fragment angular distributions of fusion-fission reactions for the systemsof <sup>16</sup>O+<sup>232</sup>Th,<sup>19</sup>F+<sup>232</sup>Th and <sup>16</su...The fragment angular distributions of fusion-fission reactions for the systemsof <sup>16</sup>O+<sup>232</sup>Th,<sup>19</sup>F+<sup>232</sup>Th and <sup>16</sup>O+<sup>238</sup>U at near-and sub-barrier energies were measured.The measured fragment anisotropies obviously deviate from the predictions ofscission-point transition-state model.We also compared the excitation energy of tiltingmode with the statistical assumption.It was found that thermal equilibrium is not estab-lished at scission for the reactions studied.展开更多
We study in the framework of the Langevin model the influence of initial excitation energy(E*) of Hg compound nuclei(CNs) on the sensitivity of the excitation energy at scission(Esc*) to the nuclear friction strength(...We study in the framework of the Langevin model the influence of initial excitation energy(E*) of Hg compound nuclei(CNs) on the sensitivity of the excitation energy at scission(Esc*) to the nuclear friction strength(β).It is shown that the sensitivity is enhanced substantially with increasing E*.Moreover,we find that the significant sensitivity of Esc* to β at high E*is little affected by a marked difference in the neutron-to-proton ratio of a CN and in its size and fissility.Our findings suggest that,on the experimental side,a measurement of Esc* in energetic proton-induced spallation reactions can provide not only a sensitive but also a robust probe of nuclear dissipation in fission of highly excited nuclei.Further development of a suitable approach to spallation reaction is discussed.展开更多
Using the stochastic Langevin model coupled with a statistical decay model,we study nuclear dissipation properties at large deformations with excitation energy at scission(E*_(sc)) measured in experiments.It is found ...Using the stochastic Langevin model coupled with a statistical decay model,we study nuclear dissipation properties at large deformations with excitation energy at scission(E*_(sc)) measured in experiments.It is found that the postsaddle dissipation strength required to fit E*_(sc) data is 12*10^(21) s^(-1)for^(254;256)Fm and 6*10^(21) s^(-1)for^(189)Au,which has a smaller postsaddle deformation than the former heavy nucleus,showing a rise of nuclear dissipation strength with increasing deformation.展开更多
C(CO)–alkyl bonds are ubiquitous in a variety of organic molecules,and their selective activation and functionalization are important for the reconstruction of simple ketones into valuable building blocks.However,due...C(CO)–alkyl bonds are ubiquitous in a variety of organic molecules,and their selective activation and functionalization are important for the reconstruction of simple ketones into valuable building blocks.However,due to the thermodynamic and kinetic stability,the cleavage and transformation of the unstrained C(CO)–alkyl bonds remain a significant challenge.Herein,we report a novel silver-catalyzed scission of the unstrained C(CO)–alkyl bond of ketones by reacting with N-isocyanoiminotriphenylphosphorane(NIITP)under mild conditions.This method could transform a variety of unstrained ketones into iminophosphoranes and nitriles in high yields.Experimental and computational studies disclosed the reaction proceeded through an unprecedented[3+2]/retro-[3+2]cycloaddition mechanism.展开更多
A dynamical model based on one-dimensional Langevin equations was used to calculate the average pre-fission multiplicities of neutrons, light charged particles, and the fission probability for compound nucleus 17Sw pr...A dynamical model based on one-dimensional Langevin equations was used to calculate the average pre-fission multiplicities of neutrons, light charged particles, and the fission probability for compound nucleus 17Sw produced in fusion reactions. The pre-seission multiplicities of particles and fission probability are calculated and compared with the experimental data over a wide range of excitation energy. A modified wall and window dissipation with a reduction coefficient, ks, has been used in the Langevin equations for reproducing experimental data. It was shown that the results of the calculations are in good agreement with the experimental data by using values of ks in the range 0.24〈 ks 〈0.47.展开更多
The emission of scission neutrons from fissioning nuclei is of high practical interest.To study this process we have used the sudden approximation and also a more realistic approach that takes into account the scissio...The emission of scission neutrons from fissioning nuclei is of high practical interest.To study this process we have used the sudden approximation and also a more realistic approach that takes into account the scission dynamics.Numerically,this implies the solution of the bi-dimensional Schr¨odinger equation,both stationary and time-dependent.To describe axially symmetric extremely deformed nuclear shapes,we have used the Cassini parametrization.The Hamiltonian is discretized by using finite difference approximations of the derivatives.The main computational challenges are the solution of algebraic eigenvalue problems and of linear systems with large sparse matrices.We have employed appropriate procedures(Arnoldi and bi-conjugate gradients).The numerical solutions have been used to evaluate physical quantities,like the number of emitted neutrons per scission event,the primary fragments’excitation energy and the distribution of the emission points.展开更多
基金This work was supported by the National Natural Science Foundation of China （No.81171829, No.51473152, and No.51573175） and the Fundamental Research hinds for the Central Universities （WK2060200012, WK3450000001）. We also thank Prof. Li-hua Yang and Prof. Ye-zi You at the University of Science and Technology of China （USTC） for their kind help ill providing experimental reagents and instrunlents.
文摘Chitosan （CS） is expected to be an ideal gene carrier for its high biosafety. In this work, CS with low molecular weight were prepared through the γ-ray radiation on the acetic acid solution of CS. The CS chains were scissioned under the γ-ray radiation, and the molecu- lar weight （MW） of CS decreased with the absorbed dose. When the absorbed dose was above 30 kGy, the molecular weight of CS decreased about an order of magnitude. The γ-ray-radiation-scissioned CS can effectively bind with plasmid （pEGFP） through complex coacervation method, forming pEGFP/γ-ray-radiation-scissioned CS complex particles with a size of 200-300 nm. The complex particles have good stability and little cytotoxicity. The in vitro gene transfection efficiencies of the pEGFP/γ-ray-radiation-scissioned CS complex particles were investigated by fluorescence microscope and flow cytometry. The results showed that the gene vectors using γ-ray-radiation-scissioned CS as the carrier will possess better gene transfection efficiency than those using natural high-MW CS as the carrier. The higher the absorbed dose, the smaller the MW of CS and the better transfection efficiency of the corresponding gene vector. This work provides a green and simple method on the preparation of CS-based gene vectors with high efficiency and biosafety.
基金supported by National Natural Science Foundation of China(No.81360474)
文摘The present study was designed to investigate the bioactive constituents ofXanthoceras sorbifolia in terms of amounts and their antioxidant, DNA scissiou protection, and ct-glucosidase inhibitory activities. Simultaneous quantification of 10 X. sorbifolia constituents was carried out by a newly established ultra-high performance liquid chromatography-quadrupole mass spectrometry method （UHPLC-MS）, The antioxidant activities were evaluated by measuring DPPH radical scavenging and DNA scission protective activities. The a-glucosidase inhibitory activities were investigated by using an assay with a-glucosidase from Bacillus Stearothermophilus and disaccharidases from mouse intestine. We found that the wood ofX. sorbifolia was rich in phenolic compounds with the contents of catechin, epicatechin, myricetin, and dihydromyricetin being 0.12-0.19, 1.94-2.16, 0.77-0.91, and 6.76-7.89 mg.g-1, respectively. The four constituents strongly scavenged DPPH radicals （with ECs0 being 4.2, 3.8 and 5.7 μg-mL-1, respectively） and remarkably protected peroxyl radical-induced DNA strand scission （92.10%, 94.66%, 75.44% and 89.95% of protection, respectively, at a concentration of 10 μmol.L-1）. A dimeric flavan 3-ol, epigallocatechin-（4β→8, 2β→O-7）-epicatechin potently inhibited a-glucosidase with an IC50 value being as low as 1.2 μg.mL1. The established UHPLC-MS method could serve as a quality control tool for X. sorbifolia. In conclusion, the high contents of antioxidant and α-glucosidase inhibitory constituents in X. sorbifolia support its use as complementation of other therapeutic agents for metabolic disorders, such as diabetes and hypertension.
文摘3-Methoxy-, 3, 5-dimethoxy-, and 3-phenyl-4-hydroxyacetophenones suffered alkyl carbonyl C-C bond scission to yield 4-hydroxybenzoate esters and 4-isopropenylphenols under standard conditions of ethylene ketal formation; the latter underwent in situ dimerization, cyclization, and rearrangement to give substituted indanols. The isopropenylphenol derived from 3,5-ditertbutyl-4-hydroxyacetophenone did not dimerize but condensed with its precursor to yield a substituted diphenylpropanone. 3-nitro-, 3,5-dinitro-, and 3,5-dibromo-4-hydroxyacetophenones on the other hand reacted normally to give ethylene ketals in good yields.
文摘The fission fragment mass-yields are evaluated for pre-actinide and actinide isotopes using a systematic statistical scission point model.The total potential energy of the fissioning systems at the scission point is presented in approximate relations as functions of mass numbers,deformation parameters and the temperature of complementary fission fragments.The collective temperature,Tcoll,and the temperature of fission fragments,Ti,are separated and the effect of collective temperature on mass yields results is investigated.The fragment temperature has been calculated with the generalized superfluid model.The sum of deformation parameters of complementary fission fragments has been obtained by fitting the calculated results with the experimental data.To investigate the transitions between symmetric and asymmetric modes mass yields for pre-actinide and heavy actinides are calculated with this model.The transition from asymmetric to symmetric fission is well reproduced using this systematic statistical scission point model.The calculated results are in good agreement with the experimental data with Tcoll=2 Me V at intermediate excitation energy and with T_(coll)=1MeV for spontaneous fission.Despite the Langevin model,in the scission point model,a constraint on the deformation parameters of fission fragments has little effect on the results of the mass yield.
文摘A new statistical method for systematizing the nuclei fission fragments, investigation of their mass and charge spectra and neutron fission parameters has been suggested. In proposed method, the mass and charge yields of nucleons are determined from the equilibrium conditions of the nuclear fragments post-fission ensemble. Here we consider protons and neutrons of different fragments as statistically non-equivalent. The abilities of the proposed statistical method for explanation of the U, Pa, Th, Ac and Ra post-fission fragments ordering and neutron emission function calculation have been demonstrated.
文摘Methyl, ethyl, n-propyl, and benzyl p-hydroxyphenyl ketones and 6-hydroxy-1-tetralone are shown under the condition of ethylene ketal formation to undergo alkyl-carbonyl C-C bondscission, but not with p-hydroxybenzophenone, p-hydroxyisobutyrophenone, and 5-hydroxy-1-indanone. It is suggested that the scissiou is preceded by an aldol condensation.
基金The project supported by the National Natural Science Foundation of China under the contract No.19275067.
文摘The fragment angular distributions of fusion-fission reactions for the systemsof <sup>16</sup>O+<sup>232</sup>Th,<sup>19</sup>F+<sup>232</sup>Th and <sup>16</sup>O+<sup>238</sup>U at near-and sub-barrier energies were measured.The measured fragment anisotropies obviously deviate from the predictions ofscission-point transition-state model.We also compared the excitation energy of tiltingmode with the statistical assumption.It was found that thermal equilibrium is not estab-lished at scission for the reactions studied.
基金Supported by National Natural Science Foundation of China(NSFC) Projects (No.11075034)
文摘We study in the framework of the Langevin model the influence of initial excitation energy(E*) of Hg compound nuclei(CNs) on the sensitivity of the excitation energy at scission(Esc*) to the nuclear friction strength(β).It is shown that the sensitivity is enhanced substantially with increasing E*.Moreover,we find that the significant sensitivity of Esc* to β at high E*is little affected by a marked difference in the neutron-to-proton ratio of a CN and in its size and fissility.Our findings suggest that,on the experimental side,a measurement of Esc* in energetic proton-induced spallation reactions can provide not only a sensitive but also a robust probe of nuclear dissipation in fission of highly excited nuclei.Further development of a suitable approach to spallation reaction is discussed.
基金supported by the National Nature Science Foundation of China(No.11575044)
文摘Using the stochastic Langevin model coupled with a statistical decay model,we study nuclear dissipation properties at large deformations with excitation energy at scission(E*_(sc)) measured in experiments.It is found that the postsaddle dissipation strength required to fit E*_(sc) data is 12*10^(21) s^(-1)for^(254;256)Fm and 6*10^(21) s^(-1)for^(189)Au,which has a smaller postsaddle deformation than the former heavy nucleus,showing a rise of nuclear dissipation strength with increasing deformation.
基金provided by the National Natural Science Foundation of China(21871043,21961130376)Department of Science and Technology of Jilin Province(20180101185JC,20190701012GH,20200801065GH)the Fundamental Research Funds for the Central Universities(2412019ZD001,2412019FZ006)。
文摘C(CO)–alkyl bonds are ubiquitous in a variety of organic molecules,and their selective activation and functionalization are important for the reconstruction of simple ketones into valuable building blocks.However,due to the thermodynamic and kinetic stability,the cleavage and transformation of the unstrained C(CO)–alkyl bonds remain a significant challenge.Herein,we report a novel silver-catalyzed scission of the unstrained C(CO)–alkyl bond of ketones by reacting with N-isocyanoiminotriphenylphosphorane(NIITP)under mild conditions.This method could transform a variety of unstrained ketones into iminophosphoranes and nitriles in high yields.Experimental and computational studies disclosed the reaction proceeded through an unprecedented[3+2]/retro-[3+2]cycloaddition mechanism.
文摘A dynamical model based on one-dimensional Langevin equations was used to calculate the average pre-fission multiplicities of neutrons, light charged particles, and the fission probability for compound nucleus 17Sw produced in fusion reactions. The pre-seission multiplicities of particles and fission probability are calculated and compared with the experimental data over a wide range of excitation energy. A modified wall and window dissipation with a reduction coefficient, ks, has been used in the Langevin equations for reproducing experimental data. It was shown that the results of the calculations are in good agreement with the experimental data by using values of ks in the range 0.24〈 ks 〈0.47.
基金supported by the contracts PNCDI2-Parteneriate 71-112 and PN09370102 of the Romanian Ministry of Education and Research.
文摘The emission of scission neutrons from fissioning nuclei is of high practical interest.To study this process we have used the sudden approximation and also a more realistic approach that takes into account the scission dynamics.Numerically,this implies the solution of the bi-dimensional Schr¨odinger equation,both stationary and time-dependent.To describe axially symmetric extremely deformed nuclear shapes,we have used the Cassini parametrization.The Hamiltonian is discretized by using finite difference approximations of the derivatives.The main computational challenges are the solution of algebraic eigenvalue problems and of linear systems with large sparse matrices.We have employed appropriate procedures(Arnoldi and bi-conjugate gradients).The numerical solutions have been used to evaluate physical quantities,like the number of emitted neutrons per scission event,the primary fragments’excitation energy and the distribution of the emission points.
