Depending on the type of charge they carry and other parameters, amphipathic molecules could be of various types. Liposome and micelle are amphipathic molecules. Liposomes are composed of a bilayer of amphipathic molecules where the two layers of molecules are arranged in two concentric circles. Micelles are closed lipid monolayers where the fatty acids are either present in the core or at the surface. This is the key difference between liposomes and micelles. Overview and Key Difference 2.
What is Liposome 3. What is Micelle 4. Similarities Between Liposome and Micelle 5. Liposomes are structures that consist of a bilayer of amphipathic molecules where the two layers of molecules are arranged in two concentric circles. In this arrangement of molecules, the outer layer hydrophilic heads are arranged where they are pointed outwards exposing to the outer environment.
The inner hydrophilic core is formed by the hydrophilic heads of the inner layer. The hydrophobic tails of both layers are arranged between the two concentric rings. The formation of a liposome occurs by a process where the dry lipid molecules are hydrated through a nonpolar solvent that is followed an agitation process mechanical induction.
The major sources for liposome formation are phospholipid molecules along with cholesterol. The types of liposomes vary according to how they are formed. This criterion of liposome classification depends on the extent of mechanical agitation and the use of a polar solvent in some instances.
In the human body, the liposomes are taken up by organs that are rich in the reticuloendothelial system. Therefore the main objective of liposomes is drug delivery, which is targeted to these organs. In order to target specific tumor cells, the liposomes are coated with special polymers. The relative liposomes production process is costly.
Therefore, these liposomes are used only during viral infection treatment and tumor cell killing. Drug administration is achieved via the parenteral route. Micelle is defined as a lipid molecule that is arranged in a spherical form in aqueous solution.
Micelles are formed in response to the amphipathic nature of fatty acids. Micelles are composed of both hydrophilic regions and hydrophobic regions.
The hydrophilic regions are polar head groups whilst the hydrophobic regions are the long hydrophobic chains tails. The polar head groups usually involve in the formation of the outside layer of the micelles since they have the ability to interact with water due to their polar nature. The hydrophobic tails are present inside of the structure to prevent the interaction with water due to their nonpolar nature.
Fatty acids that are produced from micelles contain a single hydrocarbon chain in opposite direction to two hydrocarbon chains. This structure enables the fatty acids to develop a spherical shape and thereby it lessens the steric hindrance that occurs within the fatty acid molecules themselves.
Common single chain amphiphiles that form micelles are detergents like sodium dodecyl sulfate - SDS as well as fatty acids, which themselves are detergents. NaOH feels slippery on your skin since the base hydrolyses the fatty acids esterified to skin lipids. The free fatty acids then aggregate spontaneously to form micelles which act like detergents.
Lipids in Water - Question. Liposomes produced in the lab can be unilamellar, consisting of a single bilayer surrounding the internal aqueous compartment, or multilamellar, consisting of multiple bilayers surrounding the enclosed aqueous solution. You can image the multilamellar vesicles resembles an onion with its multiple layers. Cartoons of unilamellar and multilamellar liposomes are shown below, where each concentric circle represents a bilayer. Liposomes vary in diameter. Their various sizes are shown below, in comparison to other large biological structures.
In this lab, we will make and characterize LUV. The chemical composition of liposomes can be widely varied. Most contain neutral phospholipids like phosphatidyl choline PC , phosphatidyl ethanolamine PE , or sphingomyelin SM , supplemented, if desired, with negatively charged phospholipids, like phosphatidyl serine PS and phosphatidyl glycerol PG. In addition, single chain amphiphiles like cholesterol C and detergents can be incorporated into the bilayer membrane, which modulates the fluidity and transition temperature Tm of the bilayer.
If present in too great a concentration, single chain amphiphiles like detergents, which form micelles, can disrupt the membrane so completely that the double chain amphiphiles become incorporated into detergent micelles, now called mixed micelles, in a process which effectively destroys the membrane bilayer. In lab for those that take it you will make liposomes containing only natural PC from fresh egg yolk.
Remember, the two fatty acids in naturally occurring phospholipids can be of a multiple of lengths and degrees of unsaturation. Given the large degree of unsaturation at C2, what do you expect the transition temperature of a liposome composed only of egg yolk PC to be? This high degree of unsaturation makes egg yolk PC very susceptible to oxidation, which could alter the properties of the liposome dramatically. Synthetic PC made with saturated fatty acids could alleviate that problem.
The properties of liposomes charge density, membrane fluidity, and permeability are determined by the lipid composition and size of the vesicle. The desired properties will be, in turn, determined by the use of the particular liposome. The vesicles offer wonderful, simple models to study the biochemistry and biophysics of natural membranes. In fact, membrane proteins can actually be incorporated into the liposome bilayer using the exact method you will be using. But apart from these purposes, liposomes can be used to encapsulate water soluble molecules such as nucleic acids, proteins, and toxic drugs.
These liposomes can be targeted to specific cells if antibodies or other molecules which will bind specifically to the target cell can be incorporated into the bilayer of the vesicle.
Intraliposomal material may then be transferred into the cell either by fusion of the vesicle with the cell, or by endocytosis of the vesicle.
Contributors and Attributions Prof.
0コメント