6th Summary- Experiments with Membranes, Osmosis& Selective Transport

Dr. Matt Holden March 29, 2014

The purpose of the lab is making droplets to create a membrane by investigating the relationship

between lipid membrane composition and osmosis or selectively transport rates of droplet interface

bilayer (DIBs). These droplets are created by plunging two aqueous droplets of lipid solution in

hexadecane, which creates balance. Eventually, lipid monolayers will form around the droplets when the

vesicles inside the droplets supply the lipids. Since there is affinity between the lipid monolayers, an

entropic gain occurs, where a pair of droplets surrounded by lipid monolayers will come in contact to

form a lipid bilayer. Given that the B vesicles were more concentrated than the A vesicles, water passed

from the A vesicles to the B vesicles by osmosis. From the eight lipid bilayers formed, seven coalesced.

The second part of the experiment consisted of creating more lipid bilayers between A vesicles and

resorufin dyed vesicles, which must be amphipathic so that the dye can pass from one molecule to

another. After the DIBs are formed, a diffuser is placed on top of the chip containing the DIBs to diffract

the light for better quality of the image. Then, the DIBs are illuminated using a laser pointer, which

excites the electrons in the dye when absorbing a photon. The excess energy is given off as heat or

fluorescence light, and since the fluorescence concentration was high, residence energy transfer

between molecules occurred. As a result, the membranes were selectively permeable because polimers

in the membrane did not let the dye molecules pass. In this lab, transport rates of water and other

molecules depending on the composition of membranes were observed as osmolytes and dyes were

inserted into droplets of DIBs. This experiment can be applied to cure diseases related to lipids by

changing its composition so it can either absorb more water or inhibit its water absorption. It can also be

implied by creating bio batteries by engineering toxins, and light receptors from

Halobacteriumsalinarum.