The treatment and disposal of radioactive waste are presently facing great challenges.Spent ion exchange resins have become a focus of attention due to their high production and serious environmental risks.In this pap...The treatment and disposal of radioactive waste are presently facing great challenges.Spent ion exchange resins have become a focus of attention due to their high production and serious environmental risks.In this paper,a simplified model of cationic exchange resin is proposed,and the degradation processes of cationic resin monomer initiated by hydroxyl radicals(·OH)are clarified by combining statistical molecular fragmentation(SMF)model and density functional theory(DFT)calculations.The prediction of active sites indicates that the S-O bonds and the C-S bond of the sulfonic group are more likely to react during the degradation.The meta-position of the sulfonic group on the benzene ring is the most active site,and the benzene ring without the sulfonic group has a certain reactivity.The C11-C14 and C17-C20 bonds,on the carbon skeleton,are the most easily broken.It is also found that dihydroxy addition and elimination reactions play a major role in the process of desulfonation,carbon skeleton cleavage and benzene ring separation.The decomposition mechanisms found through the combination of physical models and chemical calculations,provide theoretical guidance for the treatment of complex polycyclic aromatic hydrocarbons.展开更多
DNA degradation is a biochemical hallmark in apoptosis. It has been demonstrated in many cell types that there are two stages of DNA fragmentation during the apoptotic execution. In the early stage, chromatin DNA is c...DNA degradation is a biochemical hallmark in apoptosis. It has been demonstrated in many cell types that there are two stages of DNA fragmentation during the apoptotic execution. In the early stage, chromatin DNA is cut into large molecular weight DNA fragments, although the responsible nuclease(s) has not been recognized. In the late stage, the chromatin DNA is cleaved further into short oligonucleosomal fragments by a well-characterized nuclease in apoptosis,the caspase-activated DNase (CAD/DFF40). In this study, we demonstrate that large molecular weight DNA fragmentation also occurs in Xenopus egg extracts in apoptosis. We show that the large molecular weight DNA fragmentation factor (LDFF) is not the Xenopus CAD homolog XCAD. LDFF is activated by caspase-3. The large molecular weight DNA fragmentation activity of LDFF is Mg2+-dependent and Ca2+-independent, can occur in both acidic and neutral pH conditions and can tolerate 45℃ treatment. These results indicate that LDFF in Xenopus egg extracts might be a new DNase (or DNases) responsible for the large DNA fragmentation.展开更多
Klenow fragment（KF） uses the activity of a separate exonuclease to excise nucleotide, which is a crucial step in DNA replication and repair. Here is a novel sensitive and convenient method introduced for real-time m...Klenow fragment（KF） uses the activity of a separate exonuclease to excise nucleotide, which is a crucial step in DNA replication and repair. Here is a novel sensitive and convenient method introduced for real-time monitoring nucleotide excision by KF with a molecular beacon as a detecting probe in a homogeneous solution. This method, which overcomes the drawbacks of traditional methods such as discontinuity, time consuming and low sensitivity, was used to assay KF activity and the detection limit reached up to 0.4 U/mL. In addition, the method was applied to investigating the effects of metal ions and chemical drugs on the reaction. The results demonstrate that it is a potential high-throughput assay for screening inhibitors and activity analysis of KF in vitro.展开更多
采用离子动量成像谱仪研究了能量为1.0 ke V的电子束碰撞条件下CF_(4)分子的解离动力学.实验上,对解离离子的三维动量进行了成像测量,通过离子飞行时间关联谱识别了CF_(4)^(2+)异构化生成F_(2)^(+)分子的两个通道:F_(2)^(+)+CF_(2)^(+)...采用离子动量成像谱仪研究了能量为1.0 ke V的电子束碰撞条件下CF_(4)分子的解离动力学.实验上,对解离离子的三维动量进行了成像测量,通过离子飞行时间关联谱识别了CF_(4)^(2+)异构化生成F_(2)^(+)分子的两个通道:F_(2)^(+)+CF_(2)^(+)与CF^(+)+F_(2)^(+)+F,得到了两个通道的离子动能及动能释放分布.对于其中的三体解离通道,我们进一步采用Dalitz图与Newton图等三体动力学分析方法对解离碎片的动量关联进行了分析.该通道以两个带电离子的背对背出射为主,中性的F原子作为旁观者只得到极小的反冲动量.展开更多
凤凰雪茶是一种药食两用植物,具有较大的应用开发价值,本研究拟采用超高效液相色谱-四极杆-飞行时间串联质谱技术(ultra performance liquid chromatography-quadrupole-time of flight tandem mass spectrometry,UPLC-Q-TOF-MS/MS)联...凤凰雪茶是一种药食两用植物,具有较大的应用开发价值,本研究拟采用超高效液相色谱-四极杆-飞行时间串联质谱技术(ultra performance liquid chromatography-quadrupole-time of flight tandem mass spectrometry,UPLC-Q-TOF-MS/MS)联和全球天然产物交互分子网络(global natural products social molecular networking,GNPS)技术对凤凰雪茶的化学成分进行快速分析鉴定。在正、负离子模式下采集质谱数据,通过软件分析、数据库匹配、对照品比对等鉴别出相应化合物,并根据MS/MS碎片的相似性创建分子网络。从凤凰雪茶中共鉴定出58个化学成分,主要包括33个黄酮类、11个酚类、4个生物碱类、3个三萜类和其他类化合物。原儿茶酸-4-葡萄糖苷、杨梅素-3-芸香糖苷、积雪草酸等32个化合物首次在葡萄科蛇葡萄属得到鉴定,并进一步探讨了各类别化合物的质谱裂解规律以及黄酮类网络节点的关联分析。本研究运用液质联用结合GNPS技术可以快速实现对凤凰雪茶的成分的系统性分析,为其探究临床应用、质量控制及药效物质基础提供参考。展开更多
Tartaric acid, oxalic acid, glucose, and fructose are highly important compounds. A comprehensive study of these substances is fascinating from a scientific perspective. They are key components found in wine, vegetabl...Tartaric acid, oxalic acid, glucose, and fructose are highly important compounds. A comprehensive study of these substances is fascinating from a scientific perspective. They are key components found in wine, vegetables, and fruits. Understanding the isotopic compositions in organic compounds is crucial for comprehending various biochemical processes and the nature of substances present in different natural products. Tartaric acid, oxalic acid, glucose, and fructose are widely distributed compounds, including in vegetables and fruits. Tartaric acid plays a significant role in determining the quality and taste properties of wine, while oxalic acid is also prevalent but holds great interest for further research, especially in terms of carbon isotopic composition. We can unveil the mechanisms of processes that were previously impossible to study. Glucose and fructose are the most common monosaccharides in the hexose group, and both are found in fruits, with sweeter fruits containing higher amounts of these substances. In addition to fruits, wheat, barley, rye, onions, garlic, lentils, peppers, dried fruits, beans, broccoli, cabbage, tomatoes, and other foods are also rich sources of fructose and glucose. To determine the mass fraction of the carbon-13 isotope in these compounds, it is important to study their changes during natural synthesis. These compounds can be modified with a carbon center. According to the existing isotopic analysis method, these compounds are converted into carbon oxide or dioxide [1]. At this point, the average carbon content in the given compound is determined, but information about isotope-modified centers is lost. Dilution may occur through the transfer of other carbon-containing organic compounds in the sample or by dilution with natural carbon or carbon dioxide during the transfer process. This article discusses the possibility of carbon-13 isotope propagation directly in these compounds, both completely modified and modified with individual carbon centers. The literature provides information on determining carbon-13 substance in organic compounds, both with a general approach and for individual compounds [2] [3].展开更多
This paper describes the synthesis of peptide fragments for use in a new type of combinatorial discovery technology, in which the building blocks are brought together by non-covalent interactions, rather than direct c...This paper describes the synthesis of peptide fragments for use in a new type of combinatorial discovery technology, in which the building blocks are brought together by non-covalent interactions, rather than direct chemical bonding. The building blocks of interest—in this case different amino acids—are converted to amphiphiles by attachment to lipid tails. The amphiphiles, when mixed together in aqueous phase, are designed so that they aggregate spontaneously to form micelles. The building blocks form the headgroups of each of the amphiphiles, and these headgroups cover the surface of the micelle in a dynamic close-packed fluid mosaic array. These building blocks come together so closely that two- or three-dimensional structures are created on the surface of the micelles, and these can be screened in biological assays to find out which combination of building blocks is able to elicit a biological response. Lipopeptides consisting of two residues of lipoamino acid and other amino acids moieties have been designed, synthesized, characterized and the ability of these constructs to form supra-molecular assemblies is demonstrated.展开更多
Amino acids are very important compounds for the body and are involved in important functions that keep us healthy. Amino acids are essential components such as valine, proline, glutamine and glutamic acid. They can b...Amino acids are very important compounds for the body and are involved in important functions that keep us healthy. Amino acids are essential components such as valine, proline, glutamine and glutamic acid. They can be synthesized either naturally or artificially. To examine the metabolism and regulate the synthesis process, compounds labeled with nitrogen or carbon isotopes need to be used. These isotopic compounds allow for more extensive research and enable studies that would otherwise be impossible. However, their use is dependent on the availability of simple, efficient methods for isotopic analysis. Currently, the determination of the atomic fraction of carbon and nitrogen isotopes is only possible through their conversion into molecular nitrogen or carbon monoxide or carbon dioxide. This leads to the loss of information about isotopic enrichment in specific centers of the molecule. This article explores a new direct approach to determining the atomic fraction of carbon and nitrogen isotopes in the isotope-modified or identical centers of these compounds. This method eliminates the transfer process and dilution due to nitrogen and carbon impurities. It is now possible to simultaneously determine the atomic fraction of nitrogen and carbon isotopes in the research substance. This method can be applied to amino acids, making it an effective tool for proposing new research methods. Several articles [1] [2] [3] have proposed similar methods for organic compounds and amino acids.展开更多
基金supported by the National Natural Science Foundation of China (No.22176067).
文摘The treatment and disposal of radioactive waste are presently facing great challenges.Spent ion exchange resins have become a focus of attention due to their high production and serious environmental risks.In this paper,a simplified model of cationic exchange resin is proposed,and the degradation processes of cationic resin monomer initiated by hydroxyl radicals(·OH)are clarified by combining statistical molecular fragmentation(SMF)model and density functional theory(DFT)calculations.The prediction of active sites indicates that the S-O bonds and the C-S bond of the sulfonic group are more likely to react during the degradation.The meta-position of the sulfonic group on the benzene ring is the most active site,and the benzene ring without the sulfonic group has a certain reactivity.The C11-C14 and C17-C20 bonds,on the carbon skeleton,are the most easily broken.It is also found that dihydroxy addition and elimination reactions play a major role in the process of desulfonation,carbon skeleton cleavage and benzene ring separation.The decomposition mechanisms found through the combination of physical models and chemical calculations,provide theoretical guidance for the treatment of complex polycyclic aromatic hydrocarbons.
基金This work was supported by Major State Basic Research Program of China(No.G1999053905)National Science Fund for Distinguished Young Scholars(No.30225016).
文摘DNA degradation is a biochemical hallmark in apoptosis. It has been demonstrated in many cell types that there are two stages of DNA fragmentation during the apoptotic execution. In the early stage, chromatin DNA is cut into large molecular weight DNA fragments, although the responsible nuclease(s) has not been recognized. In the late stage, the chromatin DNA is cleaved further into short oligonucleosomal fragments by a well-characterized nuclease in apoptosis,the caspase-activated DNase (CAD/DFF40). In this study, we demonstrate that large molecular weight DNA fragmentation also occurs in Xenopus egg extracts in apoptosis. We show that the large molecular weight DNA fragmentation factor (LDFF) is not the Xenopus CAD homolog XCAD. LDFF is activated by caspase-3. The large molecular weight DNA fragmentation activity of LDFF is Mg2+-dependent and Ca2+-independent, can occur in both acidic and neutral pH conditions and can tolerate 45℃ treatment. These results indicate that LDFF in Xenopus egg extracts might be a new DNase (or DNases) responsible for the large DNA fragmentation.
基金Supported by the Key Project of Natural Science Foundation of China(No.90606003)the Hunan Provincial Natural Science Foundation, China(No.08JJ1002)+1 种基金the National High-Tech Research and Development Program(No.2007AA022007)the Changjiang Scholars and Innovative Research Team in University, China
文摘Klenow fragment（KF） uses the activity of a separate exonuclease to excise nucleotide, which is a crucial step in DNA replication and repair. Here is a novel sensitive and convenient method introduced for real-time monitoring nucleotide excision by KF with a molecular beacon as a detecting probe in a homogeneous solution. This method, which overcomes the drawbacks of traditional methods such as discontinuity, time consuming and low sensitivity, was used to assay KF activity and the detection limit reached up to 0.4 U/mL. In addition, the method was applied to investigating the effects of metal ions and chemical drugs on the reaction. The results demonstrate that it is a potential high-throughput assay for screening inhibitors and activity analysis of KF in vitro.
文摘采用离子动量成像谱仪研究了能量为1.0 ke V的电子束碰撞条件下CF_(4)分子的解离动力学.实验上,对解离离子的三维动量进行了成像测量,通过离子飞行时间关联谱识别了CF_(4)^(2+)异构化生成F_(2)^(+)分子的两个通道:F_(2)^(+)+CF_(2)^(+)与CF^(+)+F_(2)^(+)+F,得到了两个通道的离子动能及动能释放分布.对于其中的三体解离通道,我们进一步采用Dalitz图与Newton图等三体动力学分析方法对解离碎片的动量关联进行了分析.该通道以两个带电离子的背对背出射为主,中性的F原子作为旁观者只得到极小的反冲动量.
文摘凤凰雪茶是一种药食两用植物,具有较大的应用开发价值,本研究拟采用超高效液相色谱-四极杆-飞行时间串联质谱技术(ultra performance liquid chromatography-quadrupole-time of flight tandem mass spectrometry,UPLC-Q-TOF-MS/MS)联和全球天然产物交互分子网络(global natural products social molecular networking,GNPS)技术对凤凰雪茶的化学成分进行快速分析鉴定。在正、负离子模式下采集质谱数据,通过软件分析、数据库匹配、对照品比对等鉴别出相应化合物,并根据MS/MS碎片的相似性创建分子网络。从凤凰雪茶中共鉴定出58个化学成分,主要包括33个黄酮类、11个酚类、4个生物碱类、3个三萜类和其他类化合物。原儿茶酸-4-葡萄糖苷、杨梅素-3-芸香糖苷、积雪草酸等32个化合物首次在葡萄科蛇葡萄属得到鉴定,并进一步探讨了各类别化合物的质谱裂解规律以及黄酮类网络节点的关联分析。本研究运用液质联用结合GNPS技术可以快速实现对凤凰雪茶的成分的系统性分析,为其探究临床应用、质量控制及药效物质基础提供参考。
文摘Tartaric acid, oxalic acid, glucose, and fructose are highly important compounds. A comprehensive study of these substances is fascinating from a scientific perspective. They are key components found in wine, vegetables, and fruits. Understanding the isotopic compositions in organic compounds is crucial for comprehending various biochemical processes and the nature of substances present in different natural products. Tartaric acid, oxalic acid, glucose, and fructose are widely distributed compounds, including in vegetables and fruits. Tartaric acid plays a significant role in determining the quality and taste properties of wine, while oxalic acid is also prevalent but holds great interest for further research, especially in terms of carbon isotopic composition. We can unveil the mechanisms of processes that were previously impossible to study. Glucose and fructose are the most common monosaccharides in the hexose group, and both are found in fruits, with sweeter fruits containing higher amounts of these substances. In addition to fruits, wheat, barley, rye, onions, garlic, lentils, peppers, dried fruits, beans, broccoli, cabbage, tomatoes, and other foods are also rich sources of fructose and glucose. To determine the mass fraction of the carbon-13 isotope in these compounds, it is important to study their changes during natural synthesis. These compounds can be modified with a carbon center. According to the existing isotopic analysis method, these compounds are converted into carbon oxide or dioxide [1]. At this point, the average carbon content in the given compound is determined, but information about isotope-modified centers is lost. Dilution may occur through the transfer of other carbon-containing organic compounds in the sample or by dilution with natural carbon or carbon dioxide during the transfer process. This article discusses the possibility of carbon-13 isotope propagation directly in these compounds, both completely modified and modified with individual carbon centers. The literature provides information on determining carbon-13 substance in organic compounds, both with a general approach and for individual compounds [2] [3].
文摘This paper describes the synthesis of peptide fragments for use in a new type of combinatorial discovery technology, in which the building blocks are brought together by non-covalent interactions, rather than direct chemical bonding. The building blocks of interest—in this case different amino acids—are converted to amphiphiles by attachment to lipid tails. The amphiphiles, when mixed together in aqueous phase, are designed so that they aggregate spontaneously to form micelles. The building blocks form the headgroups of each of the amphiphiles, and these headgroups cover the surface of the micelle in a dynamic close-packed fluid mosaic array. These building blocks come together so closely that two- or three-dimensional structures are created on the surface of the micelles, and these can be screened in biological assays to find out which combination of building blocks is able to elicit a biological response. Lipopeptides consisting of two residues of lipoamino acid and other amino acids moieties have been designed, synthesized, characterized and the ability of these constructs to form supra-molecular assemblies is demonstrated.
文摘Amino acids are very important compounds for the body and are involved in important functions that keep us healthy. Amino acids are essential components such as valine, proline, glutamine and glutamic acid. They can be synthesized either naturally or artificially. To examine the metabolism and regulate the synthesis process, compounds labeled with nitrogen or carbon isotopes need to be used. These isotopic compounds allow for more extensive research and enable studies that would otherwise be impossible. However, their use is dependent on the availability of simple, efficient methods for isotopic analysis. Currently, the determination of the atomic fraction of carbon and nitrogen isotopes is only possible through their conversion into molecular nitrogen or carbon monoxide or carbon dioxide. This leads to the loss of information about isotopic enrichment in specific centers of the molecule. This article explores a new direct approach to determining the atomic fraction of carbon and nitrogen isotopes in the isotope-modified or identical centers of these compounds. This method eliminates the transfer process and dilution due to nitrogen and carbon impurities. It is now possible to simultaneously determine the atomic fraction of nitrogen and carbon isotopes in the research substance. This method can be applied to amino acids, making it an effective tool for proposing new research methods. Several articles [1] [2] [3] have proposed similar methods for organic compounds and amino acids.
