Greg Grason (polymer science & engineering) : soft matter theory/polymer physics
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QuickTime™ and a decompressor are needed to see this picture. QuickTime™ and a decompressor are needed to see this picture. QuickTime™ and a decompressor are needed to see this picture. reg Grason (polymer science & engineering): oft matter theory/polymer physics lamentous Assemblies: How do small, flexibl lamentous Assemblies: How do small, flexibl molecules pack themselve molecules pack themselve -Filaments are both nanoscopic (~1-10 nm diameter) and microscopic (~1m) length -Filaments have well defined structure, chemistry and mechanical properties -Thermal forces and packing constraints gives rise to a host of complex assembly properties growth cone of axon mitotic spindle bundles of protein filaments polymer-based nano-rods ordered assembly Moon & McCarthy, Moon & McCarthy, Macromolecules Macromolecules (2003). (2003). How does Nature generate such robust & functional assemblies?? How can one design/functionalize synthetic filaments to achieve desired assembly??
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Greg Grason (polymer science & engineering) : soft matter theory/polymer physics. Filamentous Assemblies: How do small, flexible molecules pack themselves?. mitotic spindle. growth cone of axon. -Filaments are both nanoscopic (~1-10 nm diameter) and microscopic (~1 m) length - PowerPoint PPT Presentation
Transcript of Greg Grason (polymer science & engineering) : soft matter theory/polymer physics
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Greg Grason (polymer science & engineering): soft matter theory/polymer physics
Filamentous Assemblies: How do small, flexible Filamentous Assemblies: How do small, flexible molecules pack themselves?molecules pack themselves?
-Filaments are both nanoscopic (~1-10 nm diameter) and microscopic (~1m) length
-Filaments have well defined structure, chemistry and mechanical properties
-Thermal forces and packing constraints gives rise to a host of complex assembly properties
growth coneof axon
mitotic spindle
bundles of protein filaments
polymer-based nano-rods
ordered assembly
Moon & McCarthy, Moon & McCarthy, MacromoleculesMacromolecules (2003). (2003).
How does Naturegenerate such
robust & functional
assemblies??
How can one design/functionalize synthetic filaments to achieve desired
assembly??
Statistical mechanics:melting to states of intermediate order
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Grelet, Grelet, Phys. Rev. Lett. Phys. Rev. Lett. (2008).(2008).
phase behavior orrod-like fd virus
low-temperature,high-density crystal
high-temperature,low-density columnar
liquid crystal
inhomogenous structure alongfilament backbone
longitudinal thermalfluctuations
-density variationlocks into registry
-breaks symmetry alongbackbone direction
-non-zero shear modulus
-thermal fluctuations along filaments to slide freely
-fluid symmetry
-shear modulus vanishes
Questions:
-what are critical properties?
-how does melting influence mechanical properties of assemblies?
Geometry & frustration:2D packings of flexible screws
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Claessens, Semmrich, Ramos & Bausch, Claessens, Semmrich, Ramos & Bausch, PNASPNAS (2007). (2007).
bundles of filamentousactin
Bundles of helical filaments want
twist & 2D orderCan they have
both?
Biological filaments(like DNA) have helical, screw-like structure…
…and molecular screws exert a mutual twist, inducingrelative tilt
Questions:
-how does local twist packing dictate assembly properties (size) of bundles?
-other twisted assembly motifs? writhing bundles? planar assemblies of short filaments?
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Better filament packing with defects:
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5-fold disclinations drive twistingwrithing conformations
Questions: What is state of densely packed DNA? Crystalline or liquid crystalline? What type of defect structures accommodate packaging?
DNA in bacteriophage capsid (EM)
DNA in bacteriophage capsid (simulation)
Petrov, Locker & Harvey, PRE (2009).
Leforestier & Livolant, PNAS (2009).
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Homin: postdoc
Stephanie: PSE
Wei: PSE
Raw materials:espresso
Apparatus:“belafonte”
currently seekingcurrently seekinggraduate studentgraduate student
www.pse.umass.edu/ggrason/[email protected]
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Badel: postdoc
