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Juliet G Crider - One of the best experts on this subject based on the ideXlab platform.
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geometric curvature analysis of intersecting kink bands a new perspective on the 3d geometry of kink folds
Journal of Structural Geology, 2012Co-Authors: Rachel E Dunham, Juliet G CriderAbstract:Abstract We describe a complex set of monoclinal contractional kink bands, exposed in outcrops of the Darrington Phyllite on Samish Island, northwestern Washington, using traditional field measurements and differential geometry. This study is the first to apply laser scanning and geometric curvature analysis to kink bands to obtain a quantitative description of band geometry on the foliation surface. Kink bands in cross section have straight, parallel boundaries that deform a well-defined foliation; in plan view, however, kink band hinges curve and anastomose across the foliation surface, and adjacent bands commonly intersect. Three types of intersections are common: crossing ( X ), bifurcating ( Y ), and obliquely diverging ( λ ); many kink bands also taper out along strike. Geometric curvature analyses were performed on millimeter-resolution DEMs of hand samples containing intersecting kink bands. Maps of curvature parameters (e.g. mean curvature, geologic curvature) clearly outline kink bands in the samples and illuminate the geometry of kink band hinges in each type of intersection. Shortening across hand samples varies where kink bands intersect. Correlations among geometric parameters corroborate rigid rotation as a kinking mechanism for these bands. Quantitative geometric description is the first step toward understanding the three-dimensional mechanics of kink bands.
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geometric curvature analysis of intersecting kink bands a new perspective on the 3d geometry of kink folds
Journal of Structural Geology, 2012Co-Authors: Rachel E Dunham, Juliet G CriderAbstract:Abstract We describe a complex set of monoclinal contractional kink bands, exposed in outcrops of the Darrington Phyllite on Samish Island, northwestern Washington, using traditional field measurements and differential geometry. This study is the first to apply laser scanning and geometric curvature analysis to kink bands to obtain a quantitative description of band geometry on the foliation surface. Kink bands in cross section have straight, parallel boundaries that deform a well-defined foliation; in plan view, however, kink band hinges curve and anastomose across the foliation surface, and adjacent bands commonly intersect. Three types of intersections are common: crossing ( X ), bifurcating ( Y ), and obliquely diverging ( λ ); many kink bands also taper out along strike. Geometric curvature analyses were performed on millimeter-resolution DEMs of hand samples containing intersecting kink bands. Maps of curvature parameters (e.g. mean curvature, geologic curvature) clearly outline kink bands in the samples and illuminate the geometry of kink band hinges in each type of intersection. Shortening across hand samples varies where kink bands intersect. Correlations among geometric parameters corroborate rigid rotation as a kinking mechanism for these bands. Quantitative geometric description is the first step toward understanding the three-dimensional mechanics of kink bands.
Rachel E Dunham - One of the best experts on this subject based on the ideXlab platform.
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geometric curvature analysis of intersecting kink bands a new perspective on the 3d geometry of kink folds
Journal of Structural Geology, 2012Co-Authors: Rachel E Dunham, Juliet G CriderAbstract:Abstract We describe a complex set of monoclinal contractional kink bands, exposed in outcrops of the Darrington Phyllite on Samish Island, northwestern Washington, using traditional field measurements and differential geometry. This study is the first to apply laser scanning and geometric curvature analysis to kink bands to obtain a quantitative description of band geometry on the foliation surface. Kink bands in cross section have straight, parallel boundaries that deform a well-defined foliation; in plan view, however, kink band hinges curve and anastomose across the foliation surface, and adjacent bands commonly intersect. Three types of intersections are common: crossing ( X ), bifurcating ( Y ), and obliquely diverging ( λ ); many kink bands also taper out along strike. Geometric curvature analyses were performed on millimeter-resolution DEMs of hand samples containing intersecting kink bands. Maps of curvature parameters (e.g. mean curvature, geologic curvature) clearly outline kink bands in the samples and illuminate the geometry of kink band hinges in each type of intersection. Shortening across hand samples varies where kink bands intersect. Correlations among geometric parameters corroborate rigid rotation as a kinking mechanism for these bands. Quantitative geometric description is the first step toward understanding the three-dimensional mechanics of kink bands.
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geometric curvature analysis of intersecting kink bands a new perspective on the 3d geometry of kink folds
Journal of Structural Geology, 2012Co-Authors: Rachel E Dunham, Juliet G CriderAbstract:Abstract We describe a complex set of monoclinal contractional kink bands, exposed in outcrops of the Darrington Phyllite on Samish Island, northwestern Washington, using traditional field measurements and differential geometry. This study is the first to apply laser scanning and geometric curvature analysis to kink bands to obtain a quantitative description of band geometry on the foliation surface. Kink bands in cross section have straight, parallel boundaries that deform a well-defined foliation; in plan view, however, kink band hinges curve and anastomose across the foliation surface, and adjacent bands commonly intersect. Three types of intersections are common: crossing ( X ), bifurcating ( Y ), and obliquely diverging ( λ ); many kink bands also taper out along strike. Geometric curvature analyses were performed on millimeter-resolution DEMs of hand samples containing intersecting kink bands. Maps of curvature parameters (e.g. mean curvature, geologic curvature) clearly outline kink bands in the samples and illuminate the geometry of kink band hinges in each type of intersection. Shortening across hand samples varies where kink bands intersect. Correlations among geometric parameters corroborate rigid rotation as a kinking mechanism for these bands. Quantitative geometric description is the first step toward understanding the three-dimensional mechanics of kink bands.
Suzanne Walker - One of the best experts on this subject based on the ideXlab platform.
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peptidoglycan cross linking preferences of staphylococcus aureus penicillin binding proteins have implications for treating mrsa infections
Journal of the American Chemical Society, 2017Co-Authors: Veerasak Srisuknimit, Yuan Qiao, Kaitlin Schaefer, Daniel Kahne, Suzanne WalkerAbstract:Methicillin-resistant Staphylococcus aureus (MRSA) infections are a global public health problem. MRSA strains have acquired a non-native penicillin-binding protein called PBP2a that Cross-Links peptidoglycan when the native S. aureus PBPs are inhibited by β-lactams. It has been proposed that the native S. aureus PBPs can use cell wall precursors having different glycine branch lengths (penta-, tri-, or monoglycine), while PBP2a can only Cross-Link peptidoglycan strands bearing a complete pentaglycine branch. This hypothesis has never been tested because the necessary substrates have not been available. Here, we compared the ability of PBP2a and two native S. aureus transpeptidases to Cross-Link peptidoglycan strands bearing different glycine branches. We show that purified PBP2a can Cross-Link glycan strands bearing penta- and triglycine, but not monoglycine, and experiments in cells provide support for these findings. Because PBP2a cannot Cross-Link peptidoglycan containing monoglycine, this study impli...
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Peptidoglycan Cross-Linking Preferences of Staphylococcus aureus Penicillin-Binding Proteins Have Implications for Treating MRSA Infections
2017Co-Authors: Veerasak Srisuknimit, Yuan Qiao, Kaitlin Schaefer, Daniel Kahne, Suzanne WalkerAbstract:Methicillin-resistant Staphylococcus aureus (MRSA) infections are a global public health problem. MRSA strains have acquired a non-native penicillin-binding protein called PBP2a that Cross-Links peptidoglycan when the native S. aureus PBPs are inhibited by β-lactams. It has been proposed that the native S. aureus PBPs can use cell wall precursors having different glycine branch lengths (penta-, tri-, or monoglycine), while PBP2a can only Cross-Link peptidoglycan strands bearing a complete pentaglycine branch. This hypothesis has never been tested because the necessary substrates have not been available. Here, we compared the ability of PBP2a and two native S. aureus transpeptidases to Cross-Link peptidoglycan strands bearing different glycine branches. We show that purified PBP2a can Cross-Link glycan strands bearing penta- and triglycine, but not monoglycine, and experiments in cells provide support for these findings. Because PBP2a cannot Cross-Link peptidoglycan containing monoglycine, this study implicates the enzyme (FemA) that extends the monoglycine branch to triglycine on Lipid II as an ideal target for small molecules that restore sensitivity of MRSA to β-lactams
Ian S. Haworth - One of the best experts on this subject based on the ideXlab platform.
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electrophoretic mobility of duplex dna cross linked by mechlorethamine at a cytosine cytosine mismatch pair
Electrophoresis, 2013Co-Authors: Rebecca M Romero, Pornchai Rojsittisak, Ian S. HaworthAbstract:: The common nitrogen mustard, mechlorethamine, can form a covalent Cross-Link between the two bases of a cytosine-cytosine mismatch pair within a DNA duplex. The Cross-Linked species can be readily separated from DNA monoadducts and unreacted strands using denaturing polyacrylamide gel electrophoresis. Here, using DNA 19 mer duplexes that are mechlorethamine Cross-Linked at a C(4)-C(35), C(7)-C(32), C(10)-C(29), or C(13)-C(26) mismatch pair, we show that the denaturing polyacrylamide gel electrophoresis mobility of the Cross-Linked species is particularly sensitive to the proximity of the C-C Cross-Link to the duplex end. Species that are Cross-Linked at a C(4)-C(35) mismatch have greater mobilities than those Cross-Linked at C(7)-C(32) or C(13)-C(26), and the species with a central C(10)-C(29) Cross-Link have the lowest mobility. The mobility is also dependent on the proximity of the Cross-Link to a 5'-(32)P-phosphate or a 5'-fluorescein label. We interpret these results in terms of the conformational properties of the Cross-Linked species in the denaturing gel. The results are consistent with the retention of partial duplex character at the end proximal to the Cross-Link, with an influence on the mobility of the GC/AT ratio proximal to the Cross-Link and at the duplex end, and a small but discernible effect of the label.
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anomalous cross linking by mechlorethamine of dna duplexes containing c c mismatch pairs
Biochemistry, 1999Co-Authors: Rebecca M Romero, Michael Mitas, Ian S. HaworthAbstract:: Nitrogen mustards such as mechlorethamine have previously been shown to covalently Cross-Link DNA through the N7 position of the two guanine bases of a d[GXC].d[GYC] duplex sequence, a so-called 1,3 G-G-Cross-Link, when X-Y = C-G or T-A. Here, we report the formation of a new mechlorethamine Cross-Link with the d[GXC].d[GYC] fragment when X-Y is a C-C mismatch pair. Mechlorethamine Cross-Links this fragment preferentially between the two mismatched cytosine bases, rather than between the guanine bases. The Cross-Link also forms when one or both of the guanine bases of the d[GCC].d[GCC] fragment are replaced by N7-deazaguanine, and, more generally, forms with any C-C mismatch, regardless of the flanking base pairs. Piperidine cleavage of the Cross-Link species containing the d[GCC].d[GCC] sequence gives DNA fragments consistent with alkylation at the mismatched cytosine bases. We also provide evidence that the Cross-Link reaction occurs between the N3 atoms of the two cytosine bases by showing that the formation of the C-C Cross-Link is pH dependent for both mechlorethamine and chlorambucil. Dimethyl sulfate (DMS) probing of the Cross-Linked d[GCC].d[GCC] fragment showed that the major groove of the guanine adjacent to the C-C mismatch is still accessible to DMS. In contrast, the known minor groove binder Hoechst 33258 inhibits the Cross-Link formation with a C-C mismatch pair flanked by A-T base pairs. These results suggest that the C-C mismatch is Cross-Linked by mechlorethamine in the minor groove. Since C-C pairs may be involved in unusual secondary structures formed by the trinucleotide repeat sequence d[CCG]n, and associated with triplet repeat expansion diseases, mechlorethamine may serve as a useful probe for these structures.
Veerasak Srisuknimit - One of the best experts on this subject based on the ideXlab platform.
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peptidoglycan cross linking preferences of staphylococcus aureus penicillin binding proteins have implications for treating mrsa infections
Journal of the American Chemical Society, 2017Co-Authors: Veerasak Srisuknimit, Yuan Qiao, Kaitlin Schaefer, Daniel Kahne, Suzanne WalkerAbstract:Methicillin-resistant Staphylococcus aureus (MRSA) infections are a global public health problem. MRSA strains have acquired a non-native penicillin-binding protein called PBP2a that Cross-Links peptidoglycan when the native S. aureus PBPs are inhibited by β-lactams. It has been proposed that the native S. aureus PBPs can use cell wall precursors having different glycine branch lengths (penta-, tri-, or monoglycine), while PBP2a can only Cross-Link peptidoglycan strands bearing a complete pentaglycine branch. This hypothesis has never been tested because the necessary substrates have not been available. Here, we compared the ability of PBP2a and two native S. aureus transpeptidases to Cross-Link peptidoglycan strands bearing different glycine branches. We show that purified PBP2a can Cross-Link glycan strands bearing penta- and triglycine, but not monoglycine, and experiments in cells provide support for these findings. Because PBP2a cannot Cross-Link peptidoglycan containing monoglycine, this study impli...
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Peptidoglycan Cross-Linking Preferences of Staphylococcus aureus Penicillin-Binding Proteins Have Implications for Treating MRSA Infections
2017Co-Authors: Veerasak Srisuknimit, Yuan Qiao, Kaitlin Schaefer, Daniel Kahne, Suzanne WalkerAbstract:Methicillin-resistant Staphylococcus aureus (MRSA) infections are a global public health problem. MRSA strains have acquired a non-native penicillin-binding protein called PBP2a that Cross-Links peptidoglycan when the native S. aureus PBPs are inhibited by β-lactams. It has been proposed that the native S. aureus PBPs can use cell wall precursors having different glycine branch lengths (penta-, tri-, or monoglycine), while PBP2a can only Cross-Link peptidoglycan strands bearing a complete pentaglycine branch. This hypothesis has never been tested because the necessary substrates have not been available. Here, we compared the ability of PBP2a and two native S. aureus transpeptidases to Cross-Link peptidoglycan strands bearing different glycine branches. We show that purified PBP2a can Cross-Link glycan strands bearing penta- and triglycine, but not monoglycine, and experiments in cells provide support for these findings. Because PBP2a cannot Cross-Link peptidoglycan containing monoglycine, this study implicates the enzyme (FemA) that extends the monoglycine branch to triglycine on Lipid II as an ideal target for small molecules that restore sensitivity of MRSA to β-lactams