Presentation is loading. Please wait.

Presentation is loading. Please wait.

APS March MeetingDallas, March 22, 2011 FACETING OF MULTICOMPONENT CHARGED ELASTIC SHELLS Rastko Sknepnek, Cheuk-Yui Leung, Liam C. Palmer Graziano Vernizzi,

Similar presentations


Presentation on theme: "APS March MeetingDallas, March 22, 2011 FACETING OF MULTICOMPONENT CHARGED ELASTIC SHELLS Rastko Sknepnek, Cheuk-Yui Leung, Liam C. Palmer Graziano Vernizzi,"— Presentation transcript:

1 APS March MeetingDallas, March 22, 2011 FACETING OF MULTICOMPONENT CHARGED ELASTIC SHELLS Rastko Sknepnek, Cheuk-Yui Leung, Liam C. Palmer Graziano Vernizzi, Samuel I. Stupp, Michael J. Bedzyk, Monica Olvera de la Cruz

2 APS March MeetingDallas, March 22, 2011 MotivationMotivation Can electrostatic interactions lead to faceting? 100 nm Greenfield, M., et al., JACS (2009) Vernizzi & Olvera de la Cruz, PNAS (2007) PCDA-OH PCDA-KKK +3 Experiments find faceted structures in the 100nm size range. Minimization of electrostatic energy on fixed geometry reveals that in certain cases faceted structures are energetically favorable.

3 APS March MeetingDallas, March 22, 2011 Coarse-grainingCoarse-graining Cooke, et al., PRE, 2005 tail-tail interaction potential wcwc Cooke, et al., PRE, 2005 +1,+2,+3 gel liquid unstable  Electrostatic effects treated within linearized Debye-Hueckel theory:

4 APS March MeetingDallas, March 22, 2011 Molecular dynamics of a bilayer patch with 4000 lipids. T=0.6 Focus on a small region of phase diagram T=0.6, 0.7 w c =1.15 1:1 (liquid)1:2 (ordered)1:3 (ordered) T=0.7 1:1 (liquid)1:2 (liquid)1:3 (“almost” ordered)

5 APS March MeetingDallas, March 22, 2011 Use results of linearized Helfrich theory: h(x,y) vertical position at (x,y)  – lateral tension T=0.7, w c =1.15 Electrostatic interactions significantly increase . Estimate of the bending rigidity 

6 APS March MeetingDallas, March 22, 2011 Estimate of the Young’s modulus Y Regular two-dimensional ionic crystals: squaretriangular 1:11:21:3 Total energy: extract Y Estimate: Y 3:1 /Y 2:1  1.8

7 APS March MeetingDallas, March 22, 2011 In addition, different valence charges are expected to segregate. MD simulation of a three component system (1:2 and 1:3) in liquid phase (T=0.9) +3 +2 Segregation leads to an onset of effective line tension between differently charged regions. In continuum representation:

8 APS March MeetingDallas, March 22, 2011 We find shaped using a discretized version of the continuum theory of elasticity. Regions with different charge ratios have different elastic properties. (Seung and Nelson, PRA 1988) bending energy: All effects of charge are encoded in the elastic properties. stretching energy: line tension: We used simulated annealing Metropolis Monte Carlo simulations to find optimal shapes.

9 APS March MeetingDallas, March 22, 2011 Optimal faceted structures  hard /  soft =10 Y hard /Y soft =5  =0.1  =0.3  =0.6 line tension hard component fraction 20% 40%60%80%

10 APS March MeetingDallas, March 22, 2011 Optimal faceted structures  hard /  soft =30 Y hard /Y soft =10  =0.1  =0.3  =0.6 line tension hard component fraction 20% 40%60%80% 100 nm

11 APS March MeetingDallas, March 22, 2011 SummarySummary Funding provided by the U.S. Department of Energy Experimental collaborators: Dr. Megan Greenfield Cheuk Leung Prof. Michael Bedzyk Prof. Samuel Stupp Northwestern High Performance Computing System - Quest We show that electrostatic interaction can lead to lipid crystallization Charge significantly renormalizes elastic properties Different regions segregate – effective line tension Resulting shapes are faceted


Download ppt "APS March MeetingDallas, March 22, 2011 FACETING OF MULTICOMPONENT CHARGED ELASTIC SHELLS Rastko Sknepnek, Cheuk-Yui Leung, Liam C. Palmer Graziano Vernizzi,"

Similar presentations


Ads by Google