The Experts below are selected from a list of 2187 Experts worldwide ranked by ideXlab platform
Helge Ewers - One of the best experts on this subject based on the ideXlab platform.
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nanoscopic compartmentalization of membrane Protein Motion at the axon initial segment
Journal of Cell Biology, 2016Co-Authors: David Albrecht, Christian M. Winterflood, Thomas Tschager, Helge Ewers, M SadeghiAbstract:The axon initial segment (AIS) is enriched in specific adaptor, cytoskeletal, and transmembrane molecules. During AIS establishment, a membrane diffusion barrier is formed between the axonal and somatodendritic domains. Recently, an axonal periodic pattern of actin, spectrin, and ankyrin forming 190-nm-spaced, ring-like structures has been discovered. However, whether this structure is related to the diffusion barrier function is unclear. Here, we performed single-particle tracking time-course experiments on hippocampal neurons during AIS development. We analyzed the mobility of lipid-anchored molecules by high-speed single-particle tracking and correlated positions of membrane molecules with the nanoscopic organization of the AIS cytoskeleton. We observe a strong reduction in mobility early in AIS development. Membrane Protein Motion in the AIS plasma membrane is confined to a repetitive pattern of ∼190-nm-spaced segments along the AIS axis as early as day in vitro 4, and this pattern alternates with actin rings. Mathematical modeling shows that diffusion barriers between the segments significantly reduce lateral diffusion along the axon.
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Nanoscopic compartmentalization of membrane Protein Motion at the axon initial segment
bioRxiv, 2016Co-Authors: David Albrecht, Christian M. Winterflood, Thomas Tschager, Helge EwersAbstract:The axon initial segment (AIS) is enriched in specific adaptor, cytoskeletal and transmembrane molecules. During AIS establishment, a membrane diffusion barrier is formed between the axon and the somatodendritic domain. Recently, an axonal periodic pattern of actin, spectrin and ankyrin forming 190 nm distanced, ring-like structures has been discovered. However, whether this structure is related to the diffusion barrier function is unclear. Here, we performed single particle tracking timecourse experiments on hippocampal neurons during AIS development. We analyzed the mobility of lipid-anchored molecules by high-speed single particle tracking and correlated positions of membrane molecules with the nanoscopic organization of the AIS cytoskeleton. We observe a strong reduction in mobility early in AIS development. Membrane Protein Motion in the AIS plasma membrane is confined to a repetitive pattern of ~190 nm spaced segments along the AIS axis as early as DIV4 and this pattern alternates with actin rings. Our data provide a new model for the mechanism of the AIS diffusion barrier.
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segmentation of membrane Protein Motion in the axon initial segment
Biophysical Journal, 2016Co-Authors: Christian M. Winterflood, David Albrecht, Philipp Kukura, Helge EwersAbstract:The axon initial segment (AIS) is a structure rich in specific cytoskeletal molecules that play important roles in the concentration of ion-channels that are required for action-potential generation. The establishment of a postulated diffusion barrier to the lateral exchange of membrane molecules in the AIS correlates with the enrichment of specific cytoskeletal molecules at this structure during development.Recently, a repetitive pattern of actin, spectrin and ankyrin forming ring-like structures perpendicular to the direction of axonal propagation has been discovered, that is interconnected via spectrin tetramers. This structure may finally provide the long sought direct physical correlate to the diffusion barrier at the AIS.Here, we perform repeated high-throughput single-molecule tracking on individual live primary hippocampal neurons during AIS development (DIV 3 - 10). We furthermore analyze the lateral mobility of lipid-anchored and transmembrane molecules with microsecond tracking at a resolution of few nanometers via interferometric scattering (iSCAT). Finally, we correlate the lateral Motion of membrane molecules to the organization of the AIS cytoskeleton.We find that the lateral Motion of membrane molecules becomes reduced in the AIS during development and that this reduction correlates with cytoskeletal organization into ring-like structures. The lateral Motion of membrane molecules in the AIS plasma membrane is locally confined to awithin a repetitive pattern of 190 nm spaced segments along the AIS axis, consistent with the observed spacing of the cytoskeletal rings.Our data provide mechanistic insight into the diffusion barrier function in of the AIS.
David Albrecht - One of the best experts on this subject based on the ideXlab platform.
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nanoscopic compartmentalization of membrane Protein Motion at the axon initial segment
Journal of Cell Biology, 2016Co-Authors: David Albrecht, Christian M. Winterflood, Thomas Tschager, Helge Ewers, M SadeghiAbstract:The axon initial segment (AIS) is enriched in specific adaptor, cytoskeletal, and transmembrane molecules. During AIS establishment, a membrane diffusion barrier is formed between the axonal and somatodendritic domains. Recently, an axonal periodic pattern of actin, spectrin, and ankyrin forming 190-nm-spaced, ring-like structures has been discovered. However, whether this structure is related to the diffusion barrier function is unclear. Here, we performed single-particle tracking time-course experiments on hippocampal neurons during AIS development. We analyzed the mobility of lipid-anchored molecules by high-speed single-particle tracking and correlated positions of membrane molecules with the nanoscopic organization of the AIS cytoskeleton. We observe a strong reduction in mobility early in AIS development. Membrane Protein Motion in the AIS plasma membrane is confined to a repetitive pattern of ∼190-nm-spaced segments along the AIS axis as early as day in vitro 4, and this pattern alternates with actin rings. Mathematical modeling shows that diffusion barriers between the segments significantly reduce lateral diffusion along the axon.
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Nanoscopic compartmentalization of membrane Protein Motion at the axon initial segment
bioRxiv, 2016Co-Authors: David Albrecht, Christian M. Winterflood, Thomas Tschager, Helge EwersAbstract:The axon initial segment (AIS) is enriched in specific adaptor, cytoskeletal and transmembrane molecules. During AIS establishment, a membrane diffusion barrier is formed between the axon and the somatodendritic domain. Recently, an axonal periodic pattern of actin, spectrin and ankyrin forming 190 nm distanced, ring-like structures has been discovered. However, whether this structure is related to the diffusion barrier function is unclear. Here, we performed single particle tracking timecourse experiments on hippocampal neurons during AIS development. We analyzed the mobility of lipid-anchored molecules by high-speed single particle tracking and correlated positions of membrane molecules with the nanoscopic organization of the AIS cytoskeleton. We observe a strong reduction in mobility early in AIS development. Membrane Protein Motion in the AIS plasma membrane is confined to a repetitive pattern of ~190 nm spaced segments along the AIS axis as early as DIV4 and this pattern alternates with actin rings. Our data provide a new model for the mechanism of the AIS diffusion barrier.
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segmentation of membrane Protein Motion in the axon initial segment
Biophysical Journal, 2016Co-Authors: Christian M. Winterflood, David Albrecht, Philipp Kukura, Helge EwersAbstract:The axon initial segment (AIS) is a structure rich in specific cytoskeletal molecules that play important roles in the concentration of ion-channels that are required for action-potential generation. The establishment of a postulated diffusion barrier to the lateral exchange of membrane molecules in the AIS correlates with the enrichment of specific cytoskeletal molecules at this structure during development.Recently, a repetitive pattern of actin, spectrin and ankyrin forming ring-like structures perpendicular to the direction of axonal propagation has been discovered, that is interconnected via spectrin tetramers. This structure may finally provide the long sought direct physical correlate to the diffusion barrier at the AIS.Here, we perform repeated high-throughput single-molecule tracking on individual live primary hippocampal neurons during AIS development (DIV 3 - 10). We furthermore analyze the lateral mobility of lipid-anchored and transmembrane molecules with microsecond tracking at a resolution of few nanometers via interferometric scattering (iSCAT). Finally, we correlate the lateral Motion of membrane molecules to the organization of the AIS cytoskeleton.We find that the lateral Motion of membrane molecules becomes reduced in the AIS during development and that this reduction correlates with cytoskeletal organization into ring-like structures. The lateral Motion of membrane molecules in the AIS plasma membrane is locally confined to awithin a repetitive pattern of 190 nm spaced segments along the AIS axis, consistent with the observed spacing of the cytoskeletal rings.Our data provide mechanistic insight into the diffusion barrier function in of the AIS.
Henry Van Den Bedem - One of the best experts on this subject based on the ideXlab platform.
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kinematic flexibility analysis hydrogen bonding patterns impart a spatial hierarchy of Protein Motion
Journal of Chemical Information and Modeling, 2018Co-Authors: Dominik Budday, Sigrid Leyendecker, Henry Van Den BedemAbstract:Elastic network models (ENMs) and constraint-based, topological rigidity analysis are two distinct, coarse-grained approaches to study conformational flexibility of macromolecules. In the two decades since their introduction, both have contributed significantly to insights into Protein molecular mechanisms and function. However, despite a shared purpose of these approaches, the topological nature of rigidity analysis, and thereby the absence of Motion modes, has impeded a direct comparison. Here, we present an alternative, kinematic approach to rigidity analysis, which circumvents these drawbacks. We introduce a novel Protein hydrogen bond network spectral decomposition, which provides an orthonormal basis for collective Motions modulated by noncovalent interactions, analogous to the eigenspectrum of normal modes. The zero modes decompose Proteins into rigid clusters identical to those from topological rigidity, while nonzero modes rank Protein Motions by their hydrogen bond collective energy penalty. Our...
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kinematic flexibility analysis hydrogen bonding patterns impart a spatial hierarchy of Protein Motion
arXiv: Biomolecules, 2018Co-Authors: Dominik Budday, Sigrid Leyendecker, Henry Van Den BedemAbstract:Elastic network models (ENM) and constraint-based, topological rigidity analysis are two distinct, coarse-grained approaches to study conformational flexibility of macromolecules. In the two decades since their introduction, both have contributed significantly to insights into Protein molecular mechanisms and function. However, despite a shared purpose of these approaches, the topological nature of rigidity analysis, and thereby the absence of Motion modes, has impeded a direct comparison. Here, we present an alternative, kinematic approach to rigidity analysis, which circumvents these drawbacks. We introduce a novel Protein hydrogen bond network spectral decomposition, which provides an orthonormal basis for collective Motions modulated by non-covalent interactions, analogous to the eigenspectrum of normal modes, and decomposes Proteins into rigid clusters identical to those from topological rigidity. Our kinematic flexibility analysis bridges topological rigidity theory and ENM, and enables a detailed analysis of Motion modes obtained from both approaches. Our analysis reveals that collectivity of Protein Motions, reported by the Shannon entropy, is significantly lower for rigidity theory versus normal mode approaches. Strikingly, kinematic flexibility analysis suggests that the hydrogen bonding network encodes a Protein-fold specific, spatial hierarchy of Motions, which goes nearly undetected in ENM. This hierarchy reveals distinct Motion regimes that rationalize Protein stiffness changes observed from experiment and molecular dynamics simulations. A formal expression for changes in free energy derived from the spectral decomposition indicates that Motions across nearly 40% of modes obey enthalpy-entropy compensation. Taken together, our analysis suggests that hydrogen bond networks have evolved to modulate Protein structure and dynamics.
R J D Miller - One of the best experts on this subject based on the ideXlab platform.
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observation of the cascaded atomic to global length scales driving Protein Motion
Proceedings of the National Academy of Sciences of the United States of America, 2003Co-Authors: M Armstrong, Jennifer P Ogilvie, M L Cowan, A M Nagy, R J D MillerAbstract:Model studies of the ligand photodissociation process of carboxymyoglobin have been conducted by using amplified few-cycle laser pulses short enough in duration (
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Diffractive optics-based nonlinear spectroscopy: application to the study of deterministic Protein Motion
Technical Digest. Summaries of Papers Presented at the Quantum Electronics and Laser Science Conference, 1999Co-Authors: Gami Dadusc, Jennifer P Ogilvie, G.d. Goodno, V. Astinov, R J D MillerAbstract:Summary form only given. Biological systems constantly transduce various forms of chemical energy into functions in which the inherent response of the system operates at the edge of stability. Excursions from the stability region lead to denaturation; whereas small fluctuations about the stability point lead to highly correlated responses that behave in a deterministic fashion with respect to the function of the system. Exactly how is the bond energy directed in such a complex system and how has the system evolved to minimize entropic losses in conversion efficiency? We have used the oxygen binding heme Proteins as model systems for studying the coupling of reaction forces to functionally relevant Motions; i.e., structural transitions important to the self regulation of oxygen binding and transport. Since the forces involved become spatially distributed over an enormous number of degrees of freedom, the net relative Motions can be exceedingly small (
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PICOSECOND PHASE GRATING SPECTROSCOPY : APPLICATIONS TO BIOENERGETICS AND Protein DYNAMICS
Methods in Enzymology, 1994Co-Authors: John Christopher Deak, L Richard, M. Pereira, Hui-ling Chui, R J D MillerAbstract:Publisher Summary Picosecond phase grating spectroscopy (PGS) is a form of transient grating spectroscopy. This form of spectroscopy is related to holography, in which the constructed image is a diffraction grating. In general, a diffraction grating is capable of light diffraction through spatially periodic modulations in optical absorption, index of refraction, or both. The different contributions to the light diffraction process can be manipulated through changes in optical wavelengths, choice of materials, or probing conditions. The high sensitivity of this spectroscopy is also ultimately responsible for its application in following Protein Motion. Even minute changes in Protein structure that require net Motion (material displacement) can be holographically recorded as a density grating to provide a real-time view of global Protein Motion. The two different contributions to the signal, energetics, and Protein-driven density changes can be readily separated by the different temporal responses of the grating formation and by studies near the zero thermal expansion point of water.
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Picosecond phase grating spectroscopy of hemoglobin and myoglobin : energetics and dynamics of global Protein Motion
Biochemistry, 1992Co-Authors: L Richard, L Genberg, John Christopher Deak, H.-l. Chiu, R J D MillerAbstract:Phase grating spectroscopy has been used to follow the optically triggered tertiary structural changes of carboxymyoglobin (MbCO) and carboxyhemoglobin (HbCO). Probe wavelength and temperature dependencies have shown that the grating signal arises from nonthermal density changes induced by the Protein structural changes. The material displaced through the Protein structural changes leads to the excitation of coherent acoustic modes of the surrounding water. The coupling of the structural changes to the fluid hydrodynamics demonstrates that a global change in the Protein structure is occurring in less than 30 ps. The global relaxation is on the same time scale as the local changes in structure in the vicinity of the heme pocket. The observed dynamics for global relaxation and correspondence between the local and global structural changes provides evidence for the involvement of collective modes in the propagation of the initial tertiary conformational changes. The energetics can also be derived from the acoustic signal. For MbCO, the photodissociation process is endothermic by 21 +/- 2 kcal/mol, which corresponds closely to the expected Fe-CO bond enthalpy. In contrast, HbCO dissipates approximately 10 kcal/mol more energy relative to myoglobin during its initial tertiary structural relaxation. The difference in energetics indicates that significantly more energy is stored in the hemoglobin structure and is believed to be related to the quaternary structure of hemoglobin not present in the monomeric form of myoglobin. These findings provide new insight into the biomechanics of conformational changes in Proteins and lend support to theoretical models invoking stored strain energy as the driving force for large amplitude correlated Motions.
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direct observation of global Protein Motion in hemoglobin and myoglobin on picosecond time scales
Science, 1991Co-Authors: L Genberg, L Richard, George Mclendon, R J D MillerAbstract:Picosecond phase-grating spectroscopy is highly sensitive to density changes and provides a new holographic approach to the study of Protein dynamics. Photodissociation of carbon monoxide from heme Proteins induces a well-defined transition from a ligated to a deoxy structure that is important to hemoglobin and myoglobin functionality. Grating spectroscopy was used to observe Protein-driven density waves on a picosecond time scale after carbon monoxide dissociation. This result demonstrates that global tertiary structure changes of Proteins occur on an extremely fast time scale and provides new insight into the biomechanics of deterministic Protein Motion.
Christian M. Winterflood - One of the best experts on this subject based on the ideXlab platform.
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nanoscopic compartmentalization of membrane Protein Motion at the axon initial segment
Journal of Cell Biology, 2016Co-Authors: David Albrecht, Christian M. Winterflood, Thomas Tschager, Helge Ewers, M SadeghiAbstract:The axon initial segment (AIS) is enriched in specific adaptor, cytoskeletal, and transmembrane molecules. During AIS establishment, a membrane diffusion barrier is formed between the axonal and somatodendritic domains. Recently, an axonal periodic pattern of actin, spectrin, and ankyrin forming 190-nm-spaced, ring-like structures has been discovered. However, whether this structure is related to the diffusion barrier function is unclear. Here, we performed single-particle tracking time-course experiments on hippocampal neurons during AIS development. We analyzed the mobility of lipid-anchored molecules by high-speed single-particle tracking and correlated positions of membrane molecules with the nanoscopic organization of the AIS cytoskeleton. We observe a strong reduction in mobility early in AIS development. Membrane Protein Motion in the AIS plasma membrane is confined to a repetitive pattern of ∼190-nm-spaced segments along the AIS axis as early as day in vitro 4, and this pattern alternates with actin rings. Mathematical modeling shows that diffusion barriers between the segments significantly reduce lateral diffusion along the axon.
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Nanoscopic compartmentalization of membrane Protein Motion at the axon initial segment
bioRxiv, 2016Co-Authors: David Albrecht, Christian M. Winterflood, Thomas Tschager, Helge EwersAbstract:The axon initial segment (AIS) is enriched in specific adaptor, cytoskeletal and transmembrane molecules. During AIS establishment, a membrane diffusion barrier is formed between the axon and the somatodendritic domain. Recently, an axonal periodic pattern of actin, spectrin and ankyrin forming 190 nm distanced, ring-like structures has been discovered. However, whether this structure is related to the diffusion barrier function is unclear. Here, we performed single particle tracking timecourse experiments on hippocampal neurons during AIS development. We analyzed the mobility of lipid-anchored molecules by high-speed single particle tracking and correlated positions of membrane molecules with the nanoscopic organization of the AIS cytoskeleton. We observe a strong reduction in mobility early in AIS development. Membrane Protein Motion in the AIS plasma membrane is confined to a repetitive pattern of ~190 nm spaced segments along the AIS axis as early as DIV4 and this pattern alternates with actin rings. Our data provide a new model for the mechanism of the AIS diffusion barrier.
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segmentation of membrane Protein Motion in the axon initial segment
Biophysical Journal, 2016Co-Authors: Christian M. Winterflood, David Albrecht, Philipp Kukura, Helge EwersAbstract:The axon initial segment (AIS) is a structure rich in specific cytoskeletal molecules that play important roles in the concentration of ion-channels that are required for action-potential generation. The establishment of a postulated diffusion barrier to the lateral exchange of membrane molecules in the AIS correlates with the enrichment of specific cytoskeletal molecules at this structure during development.Recently, a repetitive pattern of actin, spectrin and ankyrin forming ring-like structures perpendicular to the direction of axonal propagation has been discovered, that is interconnected via spectrin tetramers. This structure may finally provide the long sought direct physical correlate to the diffusion barrier at the AIS.Here, we perform repeated high-throughput single-molecule tracking on individual live primary hippocampal neurons during AIS development (DIV 3 - 10). We furthermore analyze the lateral mobility of lipid-anchored and transmembrane molecules with microsecond tracking at a resolution of few nanometers via interferometric scattering (iSCAT). Finally, we correlate the lateral Motion of membrane molecules to the organization of the AIS cytoskeleton.We find that the lateral Motion of membrane molecules becomes reduced in the AIS during development and that this reduction correlates with cytoskeletal organization into ring-like structures. The lateral Motion of membrane molecules in the AIS plasma membrane is locally confined to awithin a repetitive pattern of 190 nm spaced segments along the AIS axis, consistent with the observed spacing of the cytoskeletal rings.Our data provide mechanistic insight into the diffusion barrier function in of the AIS.
