Glutathione peroxidase, the first example of selenoproteins identified in mammals, was subjected to force field calculations and molecular dynamics in order to enable a clearer comprehension of enzymatic selenium cata...Glutathione peroxidase, the first example of selenoproteins identified in mammals, was subjected to force field calculations and molecular dynamics in order to enable a clearer comprehension of enzymatic selenium catalysis. Starting from the established X-ray structure of bovine GPX, all kinetically defined intermediates and enzyme substrate complexes were modelled. The models thus obtained support the hypothesis that the essential steps of the catalysis are three distinct redox changes of the active site selenium which, in the ground state, presents itself at the surface of selenoperoxidases as the center of a characteristic triad built by selenocysteine, glutarnine and tryptophan. In GPX, four arginine residues and a lysine residue provide an electrostatic architecture which, in each reductive step, directs the donor substrate GSH towards the catalytic center in such a way that 1ts sulfhydryl group must react with the selenium moiety. To this end, different equally efficient modes of substrate binding appear possible. The models are consistent with substrate specificity data, kinetic pattern and other functional characteristics of the enzyme. Comparison of molecular models of GPX with those of other members of the GPX superfamily reveals that the cosubstrate binding mechanisrns are unique for the classical type of cytosolic glutathione peroxidases but cannot operate e. g. in plasma GPX and phospholipid hydroperoxide GPX. The structural differences between the selenoperoxidases, shown to be relevant to their specificities, are discussed in terms of functional diversification within the GPX superfamily展开更多
Recently, an edge adaptive image stegano- graphic method based on least significant bit （LSB） matching revisited （EA-LSBMR） has been proposed, which holds good visual quality and proper security under appropriate ...Recently, an edge adaptive image stegano- graphic method based on least significant bit （LSB） matching revisited （EA-LSBMR） has been proposed, which holds good visual quality and proper security under appropriate embedding rates. However, from the extensive experiments to EA-LSBMR, we find that the discrete Fourier transform （DFT） spectrum of pixelpairs differences histogram still reveals the presence of a secret message even in a low embedding rate. To enhance the security, a modified scheme is proposed in this paper, which can defeat the above-mentioned analysis and keep the visual quality better than EA-LSBMR in higher embedding rates. Experimental results using a latest universal steganalysis method have demonstrated the proposed method＇s good performance.展开更多
The concept of dual image reversible data hiding（DIRDH） is the technique that can produce two camouflage images after embedding secret data into one original image.Moreover,not only can the secret data be extracted ...The concept of dual image reversible data hiding（DIRDH） is the technique that can produce two camouflage images after embedding secret data into one original image.Moreover,not only can the secret data be extracted from two camouflage images but also the original image can be recovered.To achieve high image quality,Lu et al.＇s method applied least-significant-bit（LSB） matching revisited to DIRDH.In order to further improve the image quality,the proposed method modifies LSB matching revisited rules and applies them to DIRDH.According to the experimental results,the image quality of the proposed method is better than that of Lu et al.＇s method.展开更多
Babylon Revisited is one of Fitzgerald's greatest stories. In this story, the protagonist Charlie comes to Paris to get custody of her daughter Honoria from his wife's sister Marion, to whom the child is entru...Babylon Revisited is one of Fitzgerald's greatest stories. In this story, the protagonist Charlie comes to Paris to get custody of her daughter Honoria from his wife's sister Marion, to whom the child is entrusted after Charlie fell apart several years ago. However, he is prevented by his late wife's sister Marion for her selfishness and jealousy. Perhaps, Fitzgerald wants us to question whether Charlie is really prepared for parenting. The story hints that he isn't, because it provides many hints that he has not separated himself enough from his past bad habits.展开更多
Several generations of mafic dyke swarms(2.7 to 0.8Ga),highlighted by aeromagnetic data,petrography,geochemistry,isotope geology and mostly U-Pb baddeleyite ages,crosscut the Archean and
In1951,When Tibet wonpeaceful liberation, PLAsoldiers reached a townwith only a few house-holds. As a token of thanks forthe PLA who strove to expandit, the town was named Bayi,or August 1,the day on whichthe People’...In1951,When Tibet wonpeaceful liberation, PLAsoldiers reached a townwith only a few house-holds. As a token of thanks forthe PLA who strove to expandit, the town was named Bayi,or August 1,the day on whichthe People’s Liberation Armywas founded.展开更多
ZHANG Fuqing, born in June, 1919, was from Fenyang, Shanxi Province. During her childhood, she went to school in Beijing, where her knowledge was broadened and her field of vision was widened. She gradually grew into ...ZHANG Fuqing, born in June, 1919, was from Fenyang, Shanxi Province. During her childhood, she went to school in Beijing, where her knowledge was broadened and her field of vision was widened. She gradually grew into a talented and sedate girl. It was while she was still a little girl that she developed an interest in cooking. At home she often helped her parents to prepare meals. On New Year’s Day or during other festivals, what interested展开更多
Chinese New Year painting exhibition reveals the beauty of folk art A CHINESE New Year painting exhibition has offered thousands of art lovers a traditional folk art feast in Beijing this past January and February.Wi...Chinese New Year painting exhibition reveals the beauty of folk art A CHINESE New Year painting exhibition has offered thousands of art lovers a traditional folk art feast in Beijing this past January and February.With the theme of "Door Gods," over 300 works of art were on display,representing various styles in China’s different regions. Woodcut prints,each a piece of special handmade folk art featuring auspicious subjects,are characterized by their concise lines, bright colors,and joyful scenes embodying people’s best wishes for the New Year.展开更多
文摘Glutathione peroxidase, the first example of selenoproteins identified in mammals, was subjected to force field calculations and molecular dynamics in order to enable a clearer comprehension of enzymatic selenium catalysis. Starting from the established X-ray structure of bovine GPX, all kinetically defined intermediates and enzyme substrate complexes were modelled. The models thus obtained support the hypothesis that the essential steps of the catalysis are three distinct redox changes of the active site selenium which, in the ground state, presents itself at the surface of selenoperoxidases as the center of a characteristic triad built by selenocysteine, glutarnine and tryptophan. In GPX, four arginine residues and a lysine residue provide an electrostatic architecture which, in each reductive step, directs the donor substrate GSH towards the catalytic center in such a way that 1ts sulfhydryl group must react with the selenium moiety. To this end, different equally efficient modes of substrate binding appear possible. The models are consistent with substrate specificity data, kinetic pattern and other functional characteristics of the enzyme. Comparison of molecular models of GPX with those of other members of the GPX superfamily reveals that the cosubstrate binding mechanisrns are unique for the classical type of cytosolic glutathione peroxidases but cannot operate e. g. in plasma GPX and phospholipid hydroperoxide GPX. The structural differences between the selenoperoxidases, shown to be relevant to their specificities, are discussed in terms of functional diversification within the GPX superfamily
基金supported in part by the National Science Foundation of China for Distinguished Young Scholars under Grant No. 61025013Sino-Singapore JRP under Grant No. 2010DFA11010+1 种基金National NSF of China under Grant No. 61073159Fundamental Research Funds for the Central Universities under Grant No. 2009JBZ006
文摘Recently, an edge adaptive image stegano- graphic method based on least significant bit （LSB） matching revisited （EA-LSBMR） has been proposed, which holds good visual quality and proper security under appropriate embedding rates. However, from the extensive experiments to EA-LSBMR, we find that the discrete Fourier transform （DFT） spectrum of pixelpairs differences histogram still reveals the presence of a secret message even in a low embedding rate. To enhance the security, a modified scheme is proposed in this paper, which can defeat the above-mentioned analysis and keep the visual quality better than EA-LSBMR in higher embedding rates. Experimental results using a latest universal steganalysis method have demonstrated the proposed method＇s good performance.
基金supported by MOST under Grants No.105-2410-H-468-010 and No.105-2221-E-468-019
文摘The concept of dual image reversible data hiding（DIRDH） is the technique that can produce two camouflage images after embedding secret data into one original image.Moreover,not only can the secret data be extracted from two camouflage images but also the original image can be recovered.To achieve high image quality,Lu et al.＇s method applied least-significant-bit（LSB） matching revisited to DIRDH.In order to further improve the image quality,the proposed method modifies LSB matching revisited rules and applies them to DIRDH.According to the experimental results,the image quality of the proposed method is better than that of Lu et al.＇s method.
文摘Babylon Revisited is one of Fitzgerald's greatest stories. In this story, the protagonist Charlie comes to Paris to get custody of her daughter Honoria from his wife's sister Marion, to whom the child is entrusted after Charlie fell apart several years ago. However, he is prevented by his late wife's sister Marion for her selfishness and jealousy. Perhaps, Fitzgerald wants us to question whether Charlie is really prepared for parenting. The story hints that he isn't, because it provides many hints that he has not separated himself enough from his past bad habits.
文摘Several generations of mafic dyke swarms(2.7 to 0.8Ga),highlighted by aeromagnetic data,petrography,geochemistry,isotope geology and mostly U-Pb baddeleyite ages,crosscut the Archean and
文摘In1951,When Tibet wonpeaceful liberation, PLAsoldiers reached a townwith only a few house-holds. As a token of thanks forthe PLA who strove to expandit, the town was named Bayi,or August 1,the day on whichthe People’s Liberation Armywas founded.
文摘ZHANG Fuqing, born in June, 1919, was from Fenyang, Shanxi Province. During her childhood, she went to school in Beijing, where her knowledge was broadened and her field of vision was widened. She gradually grew into a talented and sedate girl. It was while she was still a little girl that she developed an interest in cooking. At home she often helped her parents to prepare meals. On New Year’s Day or during other festivals, what interested
文摘Chinese New Year painting exhibition reveals the beauty of folk art A CHINESE New Year painting exhibition has offered thousands of art lovers a traditional folk art feast in Beijing this past January and February.With the theme of "Door Gods," over 300 works of art were on display,representing various styles in China’s different regions. Woodcut prints,each a piece of special handmade folk art featuring auspicious subjects,are characterized by their concise lines, bright colors,and joyful scenes embodying people’s best wishes for the New Year.
