Elucidating the mechanism of transcription initiation by RNA polymerases (RNAP) is essential for ... more Elucidating the mechanism of transcription initiation by RNA polymerases (RNAP) is essential for understanding gene transcription and regulation. Although several models such as DNA scrunching, RNAP translation, and RNAP rotation have been proposed, the mechanism of initiation by T7 RNAP has remained unclear. Using ensemble and single molecule Förster resonance energy transfer (FRET) studies, we provide evidence for concerted DNA scrunching and rotation during initiation by T7 RNAP. A constant spatial distance between the upstream and downstream edges of initiation complexes making 4-7 nt RNA supports the DNA scrunching model, but not the RNAP translation or the pure rotation model. DNA scrunching is accompanied by moderate hinging motion (18 ± 4°) of the promoter towards the downstream DNA. The observed step-wise conformational changes provide a basis to understand abortive RNA synthesis during early stages of initiation and promoter escape during the later stages that allows transition to processive elongation.
We consider the Poisson Boolean model of percolation where the percolating shapes are convex regi... more We consider the Poisson Boolean model of percolation where the percolating shapes are convex regions. By an enhancement argument we strengthen a result of Jonasson (2000) to show that the critical intensity of percolation in two dimensions is minimized among the class of convex shapes of unit area when the percolating shapes are triangles, and, for any other shape, the critical intensity is strictly larger than this minimum value. We also obtain a partial generalization to higher dimensions. In particular, for three dimensions, the critical intensity of percolation is minimized among the class of regular polytopes of unit volume when the percolating shapes are tetrahedrons. Moreover, for any other regular polytope, the critical intensity is strictly larger than this minimum value.
We propose an alternative formulation of the Z 2 topological index for quantum spin Hall systems ... more We propose an alternative formulation of the Z 2 topological index for quantum spin Hall systems and band insulators when time reversal invariance is not broken. The index is expressed in terms of the Chern numbers of the bands of the model, and a connection with the number of pairs of robust edge states is thus established. The alternative index is easy to compute in most cases of interest. We also discuss connections with the recently proposed spin Chern number for quantum spin Hall models.
We present a case of acute severe hypereosinophilia associated with the development of right vent... more We present a case of acute severe hypereosinophilia associated with the development of right ventricular thrombosis. Hypereosinophilia is associated with cardiac involvement, pulmonary infiltrates, central nervous system disease and infiltration of abdominal organs. ...
This paper proposes a fast exact algorithm to solve the Pallet Loading Problem (PLP) using depth-... more This paper proposes a fast exact algorithm to solve the Pallet Loading Problem (PLP) using depth-first strategy. A new concept called Maximal Breadth Filling Sequence (MBFS) is introduced to bring down the size of the search tree. The algorithm makes use of two pruning rules ...
We consider a percolation model which consists of oriented lines placed randomly on the plane. Th... more We consider a percolation model which consists of oriented lines placed randomly on the plane. The lines are of random length and at a random angle with respect to the horizontal axis and are placed according to a Poisson point process; the length, angle, and orientation being independent of the underlying Poisson process. We establish a critical behaviour of this model, i.e., percolation occurs for large intensity of the Poisson process and does not occur for smaller intensities. In the special case when the lines are of fixed unit length and are either oriented vertically up or oriented horizontally to the left, with probability p or (1-p), respectively, we obtain a lower bound on the critical intensity of percolation.
While technology is important, organizational and human factors also play a crucial role in achie... more While technology is important, organizational and human factors also play a crucial role in achieving information security. In this paper we develop a system dynamics model of the interplay between technical and behavioral security factors, along with their impact on business value of an organization's IT infrastructure. The model captures delays associated with perception of security risk, the mechanics of user compliance and the mechanics of risk mitigation achieved by investments in security technology and user training. These structural model components interact to mediate the impact of security incidents on the business value generated by information technology enabled transactions. The model reveals the dynamics of erosion in and recovery of business value resulting from security incidents. Experiments with the model suggest that information security drills, analogous to fire drills, may be useful in maintaining user compliance, in addition to usual training and awareness ...
Multilayer perceptron (MLP) (trained with back propagation learning algorithm) takes large comput... more Multilayer perceptron (MLP) (trained with back propagation learning algorithm) takes large computational time. The complexity of the network increases as the number of layers and number of nodes in layers increases. Further, it is also very difficult to decide the number of nodes in a layer and the number of layers in the network required for solving a problem a priori. In this paper an improved particle swarm optimization (IPSO) is used to train the functional link artificial neural network (FLANN) for classification and we name it ISO-FLANN. In contrast to MLP, FLANN has less architectural complexity, easier to train, and more insight may be gained in the classification problem. Further, we rely on global classification capabilities of IPSO to explore the entire weight space, which is plagued by a host of local optima. Using the functionally expanded features; FLANN overcomes the non-linear nature of problems. We believe that the combined efforts of FLANN and IPSO (IPSO + FLANN = ISO − FLANN) by harnessing their best attributes can give rise to a robust classifier. An extensive simulation study is presented to show the effectiveness of proposed classifier. Results are compared with MLP, support vector machine(SVM) with radial basis function (RBF) kernel, FLANN with gradiend descent learning and fuzzy swarm net (FSN).
SSB proteins bind to and control the accessibility of single-stranded DNA (ssDNA), likely facilit... more SSB proteins bind to and control the accessibility of single-stranded DNA (ssDNA), likely facilitated by their ability to diffuse on ssDNA. Using a hybrid single-molecule method combining fluorescence and force, we probed how proteins with large binding site sizes can migrate rapidly on DNA and how protein-protein interactions and tension may modulate the motion. We observed force-induced progressive unraveling of ssDNA from the SSB surface between 1 and 6 pN, followed by SSB dissociation at $10 pN, and obtained experimental evidence of a reptation mechanism for protein movement along DNA wherein a protein slides via DNA bulge formation and propagation. SSB diffusion persists even when bound with RecO and at forces under which the fully wrapped state is perturbed, suggesting that even in crowded cellular conditions SSB can act as a sliding platform to recruit and carry its interacting proteins for use in DNA replication, recombination and repair.
Ca 2þ release sites in cardiomyocytes. Since individual TT structures are below the resolution li... more Ca 2þ release sites in cardiomyocytes. Since individual TT structures are below the resolution limit of convential light microscopes, the nanoarchitecture in living heart cells is uncertain. Using STED (stimulated emission depletion) nanoscopy and the membrane probe di-8-ANEPPS, we characterized TTs quantitatively deep inside living cardiomyocytes. Using 2D analysis of TT cross-sections we determined diameters and contours indicating regular cylindrical structures. However, after myocardial infarction (post-MI) TT cross-sections appeared dilated. In addition, the continuous TT network changed progressively, resulting in loss of regular tubule orientations and sarcomere misalignement 8 weeks post-MI. In contrast, 4 weeks post-MI a signficant increase of longitudinal network components was evidenced, resembling an immature embryonic phenotype. Analysis of TT associated protein expression confirmed embryonic remodeling 4 weeks post-MI. Furthermore, mathematical modeling of increased spacing between TTs and intracellular Ca 2þ release channels revealed delayed subcellular Ca 2þ release and action potential prolongation in heart failure. In conclusion, STED nanoscopy of intracellular TT structures in living myocytes provides direct insight about a fundamental mechanisms of excitation-contraction coupling and how TT changes contribute to Ca 2þ release dysfunction in heart failure.
We study the asymptotic properties of a minimal spanning tree formed by n points uniformly distri... more We study the asymptotic properties of a minimal spanning tree formed by n points uniformly distributed in the unit square, where the minimality is amongst all rooted spanning trees with a direction of growth. We show that the number of branches from the root of this tree, the total length of these branches, and the length of the longest branch each converges weakly. This model is related to the study of record values in the theory of extreme-value statistics and this relation is used to obtain our results. The results also hold when the tree is formed from a Poisson point process of intensity n in the unit square.
Proceedings of the 38th Annual Hawaii International Conference on System Sciences
Designing a supply chain structure for a volatile market can be tricky. This is more so for produ... more Designing a supply chain structure for a volatile market can be tricky. This is more so for products with a short lifecycle. A capacity constrained supply chain in such a setting impedes the product's market acceptance by limiting product availability and thereby frustrating customers. This paper presents an experimental method, which can be used by channel designers for this purpose. We use a two-echelon supply chain system to elucidate the method. The supply chain structure is represented using system dynamics formalism. Experiment on the model leads to an indication of the cost that the system would incur. Using this cost and through loop dominance analysis we identify feedback loops that primarily determine system behavior. We show that by strengthening the dominant feedback loop, significant improvement in performance can be achieved. The method we claim can easily be deployed in supply chains of other products and can also be used to justify information technology investment decisions.
Hawaii International Conference on System Sciences, 2006
Managing service levels is known to be an important element of customer relationship management. ... more Managing service levels is known to be an important element of customer relationship management. In service industries however, there is no inventory of finished goods that can be used to buffer production and yet maintain superior service levels in the face of uncertain demand patterns. Hence capacity planning for different resources takes on special importance in achieving high customer service
2014 International Conference on Advances in Computing, Communications and Informatics (ICACCI), 2014
In this work, an object tracking method using a rule mining/induction technique is presented. Ini... more In this work, an object tracking method using a rule mining/induction technique is presented. Initially, a rule based classification algorithm is employed to classify the target frame into object and background. A sequential covering algorithm is used in order to extract the rules from the candidate frame. Extracted rules are then used for classifying the test samples obtained from the search region of the target frame. Classified test samples form the classification map which are used for calculating the new centroid to locate the object in the target frame. Temporal coherence (between frames) is maintained by updating the rule set during the rule extraction phase. Efficiency of the proposed method is established both qualitatively and quantitatively by comparing it with some of the state-of-the-art algorithms.
An irksome feature in the study of the history of science, mathematics, and society formation is ... more An irksome feature in the study of the history of science, mathematics, and society formation is encountering'Eurocentrism'at practically every level. The notion that everything'civilised'originated in Europe is an enterprise which began around two hundred years ago, at a ...
We provide an argument based on flux insertion to show that certain superconductors with a non-tr... more We provide an argument based on flux insertion to show that certain superconductors with a non-trivial topological invariant have protected zero modes in their vortex cores. This argument has the flavor of a two dimensional index theorem and applies to disordered systems as well. It also provides a new way of understanding the zero modes in the vortex cores of a spinless px + ipy superconductor. Applying this approach to superconductors with and without time reversal and spin rotational symmetry, we predict the necessary and sufficient conditions for protected zero modes to exist in their vortices.
Hfq protein is vital for the function of many non-coding small (s)RNAs in bacteria but the mechan... more Hfq protein is vital for the function of many non-coding small (s)RNAs in bacteria but the mechanism by which Hfq facilitates the function of sRNA is still debated. We developed a fluorescence resonance energy transfer assay to probe how Hfq modulates the interaction between a sRNA, DsrA, and its regulatory target mRNA, rpoS. The relevant RNA fragments were labelled so that changes in intra-and intermolecular RNA structures can be monitored in real time. Our data show that Hfq promotes the strand exchange reaction in which the internal structure of rpoS is replaced by pairing with DsrA such that the Shine-Dalgarno sequence of the mRNA becomes exposed. Hfq appears to carry out strand exchange by inducing rapid association of DsrA and a premelted rpoS and by aiding in the slow disruption of the rpoS secondary structure. Unexpectedly, Hfq also disrupts a preformed complex between rpoS and DsrA. While it may not be a frequent event in vivo, this melting activity may have implications in the reversal of sRNA-based regulation. Overall, our data suggests that Hfq not only promotes strand exchange by binding rapidly to both DsrA and rpoS but also possesses RNA chaperoning properties that facilitates dynamic RNA-RNA interactions.
Imaging single fluorescent proteins in living mammalian cells is challenging due to out-of-focus ... more Imaging single fluorescent proteins in living mammalian cells is challenging due to out-of-focus fluorescence excitation by common microscopy schemes. We report the development of a novel fluorescence microscopy method, reflected light sheet microscopy (RLSM), which allows selective plane illumination throughout the nucleus of living mammalian cells, for reducing outof-focus fluorescence signal. Generation of a thin light sheet parallel to the imaging plane and close to the sample surface is achieved by reflecting an elliptical laser beam incident from the top by 45° with a small mirror. The thin light sheet allows for an increased signal-to-background ratio superior to previous illumination schemes and enables imaging of single fluorescent proteins with up to 100 Hz time resolution. We demonstrate the sensitivity of RLSM by measuring the DNAbound fraction of glucocorticoid receptor (GR) and determine the residence times on DNA of various oligomerization states and mutants of GR and estrogen receptor (ER), enabling us to resolve different modes of DNA binding of GR. Finally, we demonstrate two-color single molecule imaging by observing the spatio-temporal co-localization of two different protein pairs. The combination of our single molecule measurements and statistical analysis reveals dynamic properties of transcription factors in live mammalian cells. Users may view, print, copy, download and text and data-mine the content in such documents, for the purposes of academic research, subject always to the full Conditions of use:
Elucidating the mechanism of transcription initiation by RNA polymerases (RNAP) is essential for ... more Elucidating the mechanism of transcription initiation by RNA polymerases (RNAP) is essential for understanding gene transcription and regulation. Although several models such as DNA scrunching, RNAP translation, and RNAP rotation have been proposed, the mechanism of initiation by T7 RNAP has remained unclear. Using ensemble and single molecule Förster resonance energy transfer (FRET) studies, we provide evidence for concerted DNA scrunching and rotation during initiation by T7 RNAP. A constant spatial distance between the upstream and downstream edges of initiation complexes making 4-7 nt RNA supports the DNA scrunching model, but not the RNAP translation or the pure rotation model. DNA scrunching is accompanied by moderate hinging motion (18 ± 4°) of the promoter towards the downstream DNA. The observed step-wise conformational changes provide a basis to understand abortive RNA synthesis during early stages of initiation and promoter escape during the later stages that allows transition to processive elongation.
We consider the Poisson Boolean model of percolation where the percolating shapes are convex regi... more We consider the Poisson Boolean model of percolation where the percolating shapes are convex regions. By an enhancement argument we strengthen a result of Jonasson (2000) to show that the critical intensity of percolation in two dimensions is minimized among the class of convex shapes of unit area when the percolating shapes are triangles, and, for any other shape, the critical intensity is strictly larger than this minimum value. We also obtain a partial generalization to higher dimensions. In particular, for three dimensions, the critical intensity of percolation is minimized among the class of regular polytopes of unit volume when the percolating shapes are tetrahedrons. Moreover, for any other regular polytope, the critical intensity is strictly larger than this minimum value.
We propose an alternative formulation of the Z 2 topological index for quantum spin Hall systems ... more We propose an alternative formulation of the Z 2 topological index for quantum spin Hall systems and band insulators when time reversal invariance is not broken. The index is expressed in terms of the Chern numbers of the bands of the model, and a connection with the number of pairs of robust edge states is thus established. The alternative index is easy to compute in most cases of interest. We also discuss connections with the recently proposed spin Chern number for quantum spin Hall models.
We present a case of acute severe hypereosinophilia associated with the development of right vent... more We present a case of acute severe hypereosinophilia associated with the development of right ventricular thrombosis. Hypereosinophilia is associated with cardiac involvement, pulmonary infiltrates, central nervous system disease and infiltration of abdominal organs. ...
This paper proposes a fast exact algorithm to solve the Pallet Loading Problem (PLP) using depth-... more This paper proposes a fast exact algorithm to solve the Pallet Loading Problem (PLP) using depth-first strategy. A new concept called Maximal Breadth Filling Sequence (MBFS) is introduced to bring down the size of the search tree. The algorithm makes use of two pruning rules ...
We consider a percolation model which consists of oriented lines placed randomly on the plane. Th... more We consider a percolation model which consists of oriented lines placed randomly on the plane. The lines are of random length and at a random angle with respect to the horizontal axis and are placed according to a Poisson point process; the length, angle, and orientation being independent of the underlying Poisson process. We establish a critical behaviour of this model, i.e., percolation occurs for large intensity of the Poisson process and does not occur for smaller intensities. In the special case when the lines are of fixed unit length and are either oriented vertically up or oriented horizontally to the left, with probability p or (1-p), respectively, we obtain a lower bound on the critical intensity of percolation.
While technology is important, organizational and human factors also play a crucial role in achie... more While technology is important, organizational and human factors also play a crucial role in achieving information security. In this paper we develop a system dynamics model of the interplay between technical and behavioral security factors, along with their impact on business value of an organization's IT infrastructure. The model captures delays associated with perception of security risk, the mechanics of user compliance and the mechanics of risk mitigation achieved by investments in security technology and user training. These structural model components interact to mediate the impact of security incidents on the business value generated by information technology enabled transactions. The model reveals the dynamics of erosion in and recovery of business value resulting from security incidents. Experiments with the model suggest that information security drills, analogous to fire drills, may be useful in maintaining user compliance, in addition to usual training and awareness ...
Multilayer perceptron (MLP) (trained with back propagation learning algorithm) takes large comput... more Multilayer perceptron (MLP) (trained with back propagation learning algorithm) takes large computational time. The complexity of the network increases as the number of layers and number of nodes in layers increases. Further, it is also very difficult to decide the number of nodes in a layer and the number of layers in the network required for solving a problem a priori. In this paper an improved particle swarm optimization (IPSO) is used to train the functional link artificial neural network (FLANN) for classification and we name it ISO-FLANN. In contrast to MLP, FLANN has less architectural complexity, easier to train, and more insight may be gained in the classification problem. Further, we rely on global classification capabilities of IPSO to explore the entire weight space, which is plagued by a host of local optima. Using the functionally expanded features; FLANN overcomes the non-linear nature of problems. We believe that the combined efforts of FLANN and IPSO (IPSO + FLANN = ISO − FLANN) by harnessing their best attributes can give rise to a robust classifier. An extensive simulation study is presented to show the effectiveness of proposed classifier. Results are compared with MLP, support vector machine(SVM) with radial basis function (RBF) kernel, FLANN with gradiend descent learning and fuzzy swarm net (FSN).
SSB proteins bind to and control the accessibility of single-stranded DNA (ssDNA), likely facilit... more SSB proteins bind to and control the accessibility of single-stranded DNA (ssDNA), likely facilitated by their ability to diffuse on ssDNA. Using a hybrid single-molecule method combining fluorescence and force, we probed how proteins with large binding site sizes can migrate rapidly on DNA and how protein-protein interactions and tension may modulate the motion. We observed force-induced progressive unraveling of ssDNA from the SSB surface between 1 and 6 pN, followed by SSB dissociation at $10 pN, and obtained experimental evidence of a reptation mechanism for protein movement along DNA wherein a protein slides via DNA bulge formation and propagation. SSB diffusion persists even when bound with RecO and at forces under which the fully wrapped state is perturbed, suggesting that even in crowded cellular conditions SSB can act as a sliding platform to recruit and carry its interacting proteins for use in DNA replication, recombination and repair.
Ca 2þ release sites in cardiomyocytes. Since individual TT structures are below the resolution li... more Ca 2þ release sites in cardiomyocytes. Since individual TT structures are below the resolution limit of convential light microscopes, the nanoarchitecture in living heart cells is uncertain. Using STED (stimulated emission depletion) nanoscopy and the membrane probe di-8-ANEPPS, we characterized TTs quantitatively deep inside living cardiomyocytes. Using 2D analysis of TT cross-sections we determined diameters and contours indicating regular cylindrical structures. However, after myocardial infarction (post-MI) TT cross-sections appeared dilated. In addition, the continuous TT network changed progressively, resulting in loss of regular tubule orientations and sarcomere misalignement 8 weeks post-MI. In contrast, 4 weeks post-MI a signficant increase of longitudinal network components was evidenced, resembling an immature embryonic phenotype. Analysis of TT associated protein expression confirmed embryonic remodeling 4 weeks post-MI. Furthermore, mathematical modeling of increased spacing between TTs and intracellular Ca 2þ release channels revealed delayed subcellular Ca 2þ release and action potential prolongation in heart failure. In conclusion, STED nanoscopy of intracellular TT structures in living myocytes provides direct insight about a fundamental mechanisms of excitation-contraction coupling and how TT changes contribute to Ca 2þ release dysfunction in heart failure.
We study the asymptotic properties of a minimal spanning tree formed by n points uniformly distri... more We study the asymptotic properties of a minimal spanning tree formed by n points uniformly distributed in the unit square, where the minimality is amongst all rooted spanning trees with a direction of growth. We show that the number of branches from the root of this tree, the total length of these branches, and the length of the longest branch each converges weakly. This model is related to the study of record values in the theory of extreme-value statistics and this relation is used to obtain our results. The results also hold when the tree is formed from a Poisson point process of intensity n in the unit square.
Proceedings of the 38th Annual Hawaii International Conference on System Sciences
Designing a supply chain structure for a volatile market can be tricky. This is more so for produ... more Designing a supply chain structure for a volatile market can be tricky. This is more so for products with a short lifecycle. A capacity constrained supply chain in such a setting impedes the product's market acceptance by limiting product availability and thereby frustrating customers. This paper presents an experimental method, which can be used by channel designers for this purpose. We use a two-echelon supply chain system to elucidate the method. The supply chain structure is represented using system dynamics formalism. Experiment on the model leads to an indication of the cost that the system would incur. Using this cost and through loop dominance analysis we identify feedback loops that primarily determine system behavior. We show that by strengthening the dominant feedback loop, significant improvement in performance can be achieved. The method we claim can easily be deployed in supply chains of other products and can also be used to justify information technology investment decisions.
Hawaii International Conference on System Sciences, 2006
Managing service levels is known to be an important element of customer relationship management. ... more Managing service levels is known to be an important element of customer relationship management. In service industries however, there is no inventory of finished goods that can be used to buffer production and yet maintain superior service levels in the face of uncertain demand patterns. Hence capacity planning for different resources takes on special importance in achieving high customer service
2014 International Conference on Advances in Computing, Communications and Informatics (ICACCI), 2014
In this work, an object tracking method using a rule mining/induction technique is presented. Ini... more In this work, an object tracking method using a rule mining/induction technique is presented. Initially, a rule based classification algorithm is employed to classify the target frame into object and background. A sequential covering algorithm is used in order to extract the rules from the candidate frame. Extracted rules are then used for classifying the test samples obtained from the search region of the target frame. Classified test samples form the classification map which are used for calculating the new centroid to locate the object in the target frame. Temporal coherence (between frames) is maintained by updating the rule set during the rule extraction phase. Efficiency of the proposed method is established both qualitatively and quantitatively by comparing it with some of the state-of-the-art algorithms.
An irksome feature in the study of the history of science, mathematics, and society formation is ... more An irksome feature in the study of the history of science, mathematics, and society formation is encountering'Eurocentrism'at practically every level. The notion that everything'civilised'originated in Europe is an enterprise which began around two hundred years ago, at a ...
We provide an argument based on flux insertion to show that certain superconductors with a non-tr... more We provide an argument based on flux insertion to show that certain superconductors with a non-trivial topological invariant have protected zero modes in their vortex cores. This argument has the flavor of a two dimensional index theorem and applies to disordered systems as well. It also provides a new way of understanding the zero modes in the vortex cores of a spinless px + ipy superconductor. Applying this approach to superconductors with and without time reversal and spin rotational symmetry, we predict the necessary and sufficient conditions for protected zero modes to exist in their vortices.
Hfq protein is vital for the function of many non-coding small (s)RNAs in bacteria but the mechan... more Hfq protein is vital for the function of many non-coding small (s)RNAs in bacteria but the mechanism by which Hfq facilitates the function of sRNA is still debated. We developed a fluorescence resonance energy transfer assay to probe how Hfq modulates the interaction between a sRNA, DsrA, and its regulatory target mRNA, rpoS. The relevant RNA fragments were labelled so that changes in intra-and intermolecular RNA structures can be monitored in real time. Our data show that Hfq promotes the strand exchange reaction in which the internal structure of rpoS is replaced by pairing with DsrA such that the Shine-Dalgarno sequence of the mRNA becomes exposed. Hfq appears to carry out strand exchange by inducing rapid association of DsrA and a premelted rpoS and by aiding in the slow disruption of the rpoS secondary structure. Unexpectedly, Hfq also disrupts a preformed complex between rpoS and DsrA. While it may not be a frequent event in vivo, this melting activity may have implications in the reversal of sRNA-based regulation. Overall, our data suggests that Hfq not only promotes strand exchange by binding rapidly to both DsrA and rpoS but also possesses RNA chaperoning properties that facilitates dynamic RNA-RNA interactions.
Imaging single fluorescent proteins in living mammalian cells is challenging due to out-of-focus ... more Imaging single fluorescent proteins in living mammalian cells is challenging due to out-of-focus fluorescence excitation by common microscopy schemes. We report the development of a novel fluorescence microscopy method, reflected light sheet microscopy (RLSM), which allows selective plane illumination throughout the nucleus of living mammalian cells, for reducing outof-focus fluorescence signal. Generation of a thin light sheet parallel to the imaging plane and close to the sample surface is achieved by reflecting an elliptical laser beam incident from the top by 45° with a small mirror. The thin light sheet allows for an increased signal-to-background ratio superior to previous illumination schemes and enables imaging of single fluorescent proteins with up to 100 Hz time resolution. We demonstrate the sensitivity of RLSM by measuring the DNAbound fraction of glucocorticoid receptor (GR) and determine the residence times on DNA of various oligomerization states and mutants of GR and estrogen receptor (ER), enabling us to resolve different modes of DNA binding of GR. Finally, we demonstrate two-color single molecule imaging by observing the spatio-temporal co-localization of two different protein pairs. The combination of our single molecule measurements and statistical analysis reveals dynamic properties of transcription factors in live mammalian cells. Users may view, print, copy, download and text and data-mine the content in such documents, for the purposes of academic research, subject always to the full Conditions of use:
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Papers by Rahul Roy