Specific Adhesion of Membranes Simultaneously Supports Dual Heterogeneities in Lipids and Proteins

Membrane adhesion is a vital component of many biological processes. Heterogeneities in lipid and protein composition are often associated with the adhesion site. These heterogeneities are thought to play functional roles in facilitating signalling. Here we experimentally examine this phenomenon using model membranes made of a mixture of lipids that is near a phase boundary at room temperature. Non-adherent model membranes are in a well-mixed, disordered-fluid lipid phase indicated by homogeneous distribution of a fluorescent dye that is a marker for the fluid-disordered (Ld) phase. We specifically adhere membranes to a flat substrate bilayer using biotin–avidin binding. Adhesion produces two types of coexisting heterogeneities: an ordered lipid phase that excludes binding proteins and the fluorescent membrane dye, and a disordered lipid phase that is enriched in both binding proteins and membrane dye compared with the non-adhered portion of the same membrane. Thus, a single type of adhesion interaction (biotin–avidin binding), in an initially-homogeneous system, simultaneously stabilizes both ordered-phase and disordered-phase heterogeneities that are compositionally distinct from the non-adhered portion of the vesicle. These heterogeneities are long-lived and unchanged upon increased temperature.This work was funded by start-up funds from The University of Texas at Austin (UT Austin) to VDG. MR was supported in part by undergraduate research fellowships from UT Austin. We are grateful to Professor Jeanne Stachowiak (Biomedical Engineering, UT Austin) for helpful conversations about membrane formation and to her and her group for technical assistance. We thank Professor Ernst-Ludwig Florin (Physics, UT Austin) for the extruder and for cover glasses. We thank Professor Lauren Ehrlich (Molecular Biosciences, UT Austin) for helpful conversations about the immune synapse.Center for Nonlinear Dynamic

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Slavery in Niger: Historical, legal and contemporary perspectives

This document is part of a digital collection provided by the Martin P. Catherwood Library, ILR School, Cornell University, pertaining to the effects of globalization on the workplace worldwide. Special emphasis is placed on labor rights, working conditions, labor market changes, and union organizing.ASI_2004_DBS_Niger_Slavery_in_Niger.pdf: 110 downloads, before Oct. 1, 2020

Compromise and Synchronization in Opinion Dynamics

We discuss two models of opinion dynamics. First wepresent a brief review of the Hegselmann and Krause (HK) compromise model in two dimensions, showing that it is possible to simulate the dynamics in the limit of an infinite number of agents by solving numerically a rate equation for a continuum distribution of opinions. Then, we discuss the Opinion Changing Rate (OCR) model, which allows to study under which conditions a group of agents with a different natural tendency (rate) to change opinion can find the agreement. In the context of the this model, consensus is viewed as a synchronization process.Comment: Talk presented at the international conference Next05 Sigma Phi, 13-18 august 2005, Kolymbari, Crete. EPJ B (2006) in press. Typos corrected, refs adde

Voting for Committees in Agreeable Societies

We examine the following voting situation. A committee of $k$ people is to be formed from a pool of n candidates. The voters selecting the committee will submit a list of $j$ candidates that they would prefer to be on the committee. We assume that $j \leq k < n$. For a chosen committee, a given voter is said to be satisfied by that committee if her submitted list of $j$ candidates is a subset of that committee. We examine how popular is the most popular committee. In particular, we show there is always a committee that satisfies a certain fraction of the voters and examine what characteristics of the voter data will increase that fraction.Comment: 11 pages; to appear in Contemporary Mathematic