Abstract: The gating pathways of mechanosensitive channels of large conductance (MscL) in two bacteria (Mycobacterium tuberculosis and Escherichia coli) are studied using the finite element method. The phenomenological model treats transmembrane helices as elastic rods and the lipid membrane as an elastic sheet of finite thickness; the model is inspired by the crystal structure of MscL. The interactions between various continuum components are derived from molecular-mechanics energy calculations using the CHARMM all-atom force field. Both bacterial MscLs open fully upon in-plane tension in the membrane and the variation of pore diameter with membrane tension is found to be essentially linear. The estimated gating tension is close to the experimental value. The structural variations along the gating pathway are consistent with previous analyses based on structural models with experimental constraints and biased atomistic molecular-dynamics simulations. Upon membrane bending, neither MscL opens substantially, although there is notable and nonmonotonic variation in the pore radius. This emphasizes that the gating behavior of MscL depends critically on the form of the mechanical perturbation and reinforces the idea that the crucial gating parameter is lateral tension in the membrane rather than the curvature of the

The ASME International Mechanical Engineering Congress and Exposition (IMECE) will be held in 11-16 November 2007, in Seattle, Washington. As the 2007 Program Chair of the Applied Mechanics Division (AMD), I hope to get you involved in planning activities at the Congress.

IMECE is a place where you can meet people and attend talks in Applied Mechanics, as well as in other fields, such as Materials, Electronic Packaging, Tribology, and Heat Transfer. For many mechanicians, a highlight of the Congress is the Applied Mechanics Annual Dinner, where old acquaintances are resumed, new friends made, awards announced, and the Timoshenko lectures delivered.

[img_assist|nid=46|title=|desc=|link=url,http://www.materialstoday.com/2006_issues/april.htm|align=right|width=75|height=100]The cover story of the April 2006 issue of Materials Today features Flexible Electronics. This issue also includes two review articles in this emerging field of research. Access to full text articles is free of charge at http://www.materialstoday.com.

Review Article:

Material challenge for flexible organic devices, by Jay Lewis

Review Article:

Organic and polymer transistors for electronics, by Ananth Dodabalapur

Cover Story:

Jet printing flexible displays, by R.A. Street et al.