If you like us, please share us on social media.
The latest UCD Hyperlibrary newsletter is now complete, check it out.
Copyright (c) 2006-2014 MindTouch Inc.
This file and accompanying files are licensed under the MindTouch Master Subscription Agreement (MSA).
At any time, you shall not, directly or indirectly: (i) sublicense, resell, rent, lease, distribute, market, commercialize or otherwise transfer rights or usage to: (a) the Software, (b) any modified version or derivative work of the Software created by you or for you, or (c) MindTouch Open Source (which includes all non-supported versions of MindTouch-developed software), for any purpose including timesharing or service bureau purposes; (ii) remove or alter any copyright, trademark or proprietary notice in the Software; (iii) transfer, use or export the Software in violation of any applicable laws or regulations of any government or governmental agency; (iv) use or run on any of your hardware, or have deployed for use, any production version of MindTouch Open Source; (v) use any of the Support Services, Error corrections, Updates or Upgrades, for the MindTouch Open Source software or for any Server for which Support Services are not then purchased as provided hereunder; or (vi) reverse engineer, decompile or modify any encrypted or encoded portion of the Software.
A complete copy of the MSA is available at http://www.mindtouch.com/msa
Another indicator of membrane dynamics is the measured permeability coefficient of ions and molecules across the bilayer. (see Passive and Facilitated Diffusion). Permeabilities are correlated to the partition coefficient of the molecule or ion in organic solvents. If the molecule readily dissolves in a nonpolar solvent, it is more likely to pass through the hydrophobic barrier of the membrane. Obviously the size of the molecule would play a part as well. Hence charged ions like Na+ and K+ have low permeabilities. Cl- has a higher permeability, since the charge density on the larger Cl anion is smaller. Water has a surprisingly high permeability although it is polar. It is small and can enter down deep into the head group region through sequential H-bonding which must assist its transfer across the membrane.
Figure: Permeability of liposome bilayers
Many different probes have been developed to study membrane structure and dynamics. Many of them are fluorescent. The diagram below, taken from the Molecular Probe's catalog, gives examples.