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VERSION:2.0
CALSCALE:GREGORIAN
PRODID:UW-Madison-Physics-Events
BEGIN:VEVENT
SEQUENCE:2
UID:UW-Physics-Event-8184
DTSTART:20230223T220000Z
DTEND:20230223T230000Z
DTSTAMP:20260408T000427Z
LAST-MODIFIED:20230224T162404Z
LOCATION:2241 Chamberlin Hall
SUMMARY:Entropy\, molecular motors\, and non-thermal equilibrium stati
 stical physics\, Steven Chu\, Stanford University
DESCRIPTION:The transport of molecular cargos in neuronal cells is ana
 lyzed in the context of new developments in statistical physics. We de
 veloped bright optical probes which enabled the long-term single track
 ing of molecular cargos in live neurons for tens of minutes. The numbe
 r of dynein motors transporting a cargo in a neuron was found to switc
 h stochastically from one to five motors. We were able to resolve indi
 vidual molecular steps\, and new a quantitative chemo-mechanical model
  where a single step requires the hydrolysis of two ATP molecules. <br
 >
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\nWe also find that the movement approaches a steady-state no
 n-thermal equilibrium with effective temperature\, T_eff=〖6×T〗_ce
 ll=6×310 K. Also\, the minimum “uncertainty principle” limit\, Δ
 Q⋅ϵ^2≥2k_B T_eff\, where ΔQ=T_eff ΔS is the heat entropy needed
  to achieve movement with a normalized precision 〖ϵ(x)〗^2≡((〈
 x^2 〉-〈x〉^2))⁄〈x〉^2 . This uncertainty limit sets the mini
 mum heat energy needed to achieve a given precision in any physical op
 eration. In the context of intercellular molecular transport\, a more 
 uniform motion of the cargo requires a greater expenditure of energy. 
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URL:https://www.physics.wisc.edu/events/?id=8184
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