Proteinoid
Encyclopedia
Proteinoids, or thermal proteins, are protein
-like molecules formed inorganically from amino acid
s. Some theories of abiogenesis
propose that proteinoids were a precursor to the first living
cells
.
The inorganic polymerization
of amino acids into proteins through the formation of peptide bond
s was thought to occur only at temperatures over 140°C. However, the biochemist Sidney Walter Fox and his co-workers discovered that phosphoric acid
acted as a catalyst for this reaction. They were able to form protein-like chains from a mixture of 18 common amino acids at only 70°C in the presence of phosphoric acid, and dubbed these protein-like chains proteinoids. Fox later found proteinoids similar to those he had created in his laboratory in lava and cinders from Hawaii
an volcanic
vents and determined that the amino acids present polymerized due to the heat of escaping gases and lava. Other catalysts have since been found; one of them, amidinium carbodiimide, is formed in primitive Earth experiments and is effective in dilute aqueous
solutions.
When present in certain concentrations in aqueous solutions, proteinoids form small structures called microsphere
s or protocells. This is because some of the amino acids incorporated into proteinoid chains are more hydrophobic than others, and so proteinoids cluster together like droplets of oil in water. Many argue that these are not themselves alive
in the traditional sense, but these structures exhibit many of the characteristics of cells accepted as living cells:
It is thought that the microspheres may have provided a cell compartment within which biochemistry could have become concentrated and protected from the outside environment during the process of chemical evolution
.
Proteinoid microspheres are today being considered for use in pharmaceuticals, providing microscopic biodegradable capsules in which to package drugs for delivery to a specific region in the patient's body.
Protein
Proteins are biochemical compounds consisting of one or more polypeptides typically folded into a globular or fibrous form, facilitating a biological function. A polypeptide is a single linear polymer chain of amino acids bonded together by peptide bonds between the carboxyl and amino groups of...
-like molecules formed inorganically from amino acid
Amino acid
Amino acids are molecules containing an amine group, a carboxylic acid group and a side-chain that varies between different amino acids. The key elements of an amino acid are carbon, hydrogen, oxygen, and nitrogen...
s. Some theories of abiogenesis
Abiogenesis
Abiogenesis or biopoesis is the study of how biological life arises from inorganic matter through natural processes, and the method by which life on Earth arose...
propose that proteinoids were a precursor to the first living
Life
Life is a characteristic that distinguishes objects that have signaling and self-sustaining processes from those that do not, either because such functions have ceased , or else because they lack such functions and are classified as inanimate...
cells
Cell (biology)
The cell is the basic structural and functional unit of all known living organisms. It is the smallest unit of life that is classified as a living thing, and is often called the building block of life. The Alberts text discusses how the "cellular building blocks" move to shape developing embryos....
.
The inorganic polymerization
Polymerization
In polymer chemistry, polymerization is a process of reacting monomer molecules together in a chemical reaction to form three-dimensional networks or polymer chains...
of amino acids into proteins through the formation of peptide bond
Peptide bond
This article is about the peptide link found within biological molecules, such as proteins. A similar article for synthetic molecules is being created...
s was thought to occur only at temperatures over 140°C. However, the biochemist Sidney Walter Fox and his co-workers discovered that phosphoric acid
Phosphoric acid
Phosphoric acid, also known as orthophosphoric acid or phosphoric acid, is a mineral acid having the chemical formula H3PO4. Orthophosphoric acid molecules can combine with themselves to form a variety of compounds which are also referred to as phosphoric acids, but in a more general way...
acted as a catalyst for this reaction. They were able to form protein-like chains from a mixture of 18 common amino acids at only 70°C in the presence of phosphoric acid, and dubbed these protein-like chains proteinoids. Fox later found proteinoids similar to those he had created in his laboratory in lava and cinders from Hawaii
Hawaii
Hawaii is the newest of the 50 U.S. states , and is the only U.S. state made up entirely of islands. It is the northernmost island group in Polynesia, occupying most of an archipelago in the central Pacific Ocean, southwest of the continental United States, southeast of Japan, and northeast of...
an volcanic
Volcano
2. Bedrock3. Conduit 4. Base5. Sill6. Dike7. Layers of ash emitted by the volcano8. Flank| 9. Layers of lava emitted by the volcano10. Throat11. Parasitic cone12. Lava flow13. Vent14. Crater15...
vents and determined that the amino acids present polymerized due to the heat of escaping gases and lava. Other catalysts have since been found; one of them, amidinium carbodiimide, is formed in primitive Earth experiments and is effective in dilute aqueous
Water
Water is a chemical substance with the chemical formula H2O. A water molecule contains one oxygen and two hydrogen atoms connected by covalent bonds. Water is a liquid at ambient conditions, but it often co-exists on Earth with its solid state, ice, and gaseous state . Water also exists in a...
solutions.
When present in certain concentrations in aqueous solutions, proteinoids form small structures called microsphere
Microsphere
Microsphere are small spherical particles, with diameters in the micrometer range . Microspheres are sometimes referred to as microparticles....
s or protocells. This is because some of the amino acids incorporated into proteinoid chains are more hydrophobic than others, and so proteinoids cluster together like droplets of oil in water. Many argue that these are not themselves alive
Life
Life is a characteristic that distinguishes objects that have signaling and self-sustaining processes from those that do not, either because such functions have ceased , or else because they lack such functions and are classified as inanimate...
in the traditional sense, but these structures exhibit many of the characteristics of cells accepted as living cells:
- a film-like outer wall.
- osmotic swelling and shrinking.
- budding.
- binary fission (dividing into two daughter microspheres).
- streaming movement of internal particles.
It is thought that the microspheres may have provided a cell compartment within which biochemistry could have become concentrated and protected from the outside environment during the process of chemical evolution
Chemical evolution
Chemical evolution may refer to:*Nucleosynthesis, the creation of chemical elements in the universe either through the Big Bang, or supernovae*Abiogenesis, the transition from nonliving elements to living systems...
.
Proteinoid microspheres are today being considered for use in pharmaceuticals, providing microscopic biodegradable capsules in which to package drugs for delivery to a specific region in the patient's body.
Further readings
- Fox, S. W. and K. Dose (1977). Molecular Evolution and the Origin of Life, Marcel Dekker, Inc.