1. 5th 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 Halobacterium
salinarum.