Thermostability
Encyclopedia
Thermostability is the quality of a substance to resist irreversible change in its chemical
or physical structure at a high relative temperature.
Thermostable materials may be used industrially as fire retardant
s. A thermostable plastic
, an uncommon and unconventional term, is likely to refer to a thermosetting plastic
that cannot be reshaped when heated, than to a thermoplastic
that can be remelted and recast. Thermostability also commonly refers to a protein
resistant to irreversible change in its protein structure
due to applied heat.
of the protein structure to be irreversible, a condition understandably deleterious to continuing life-functions. The denaturing
of proteins in albumen
from a clear, nearly colourless liquid to an opaque white, insoluble gel is a common example of this.
Certain thermophilic life-forms
exist which can withstand temperatures above this. Examining homologous
proteins present in these thermophiles and other organisms reveal only slight differences in the protein structure. One notable difference is the presence of extra hydrogen bond
s in the thermophile's proteins—meaning that the protein structure is more resistant to unfolding. The presence of certain types of salt
has been observed to decrease thermostability in the proteins of mesophile
s but not of hyperthermophile
s which may indicate that salt bridges
have more impact on thermostability at high temperature than is currently widely acknowledged. Another factors of protein thermostability are compactness of protein structure, oligomerization, and strength interaction between subunits.
Thermostable enzyme
s such as Taq polymerase
and Pfu DNA polymerase
are used in polymerase chain reaction
s where temperatures of 94 °C or over are used to melt apart DNA
strands.
ous fungi contain thermostable toxin
s, such as amatoxin
found in the death cap
and autumn skullcap
mushroom
s. Therefore, applying heat to these deadly mushrooms will not remove its toxicity.
Chemical structure
A chemical structure includes molecular geometry, electronic structure and crystal structure of molecules. Molecular geometry refers to the spatial arrangement of atoms in a molecule and the chemical bonds that hold the atoms together. Molecular geometry can range from the very simple, such as...
or physical structure at a high relative temperature.
Thermostable materials may be used industrially as fire retardant
Fire retardant
A fire retardant is a substance other than water that reduces flammability of fuels or delays their combustion. This typically refers to chemical retardants but may also include substances that work by physical action, such as cooling the fuels; examples of these include fire-fighting foams and...
s. A thermostable plastic
Plastic
A plastic material is any of a wide range of synthetic or semi-synthetic organic solids used in the manufacture of industrial products. Plastics are typically polymers of high molecular mass, and may contain other substances to improve performance and/or reduce production costs...
, an uncommon and unconventional term, is likely to refer to a thermosetting plastic
Thermosetting plastic
A thermosetting plastic, also known as a thermoset, is polymer material that irreversibly cures. The cure may be done through heat , through a chemical reaction , or irradiation such as electron beam processing.Thermoset materials are usually liquid or malleable prior to curing and designed to be...
that cannot be reshaped when heated, than to a thermoplastic
Thermoplastic
Thermoplastic, also known as a thermosoftening plastic, is a polymer that turns to a liquid when heated and freezes to a very glassy state when cooled sufficiently...
that can be remelted and recast. Thermostability also commonly refers to a protein
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...
resistant to irreversible change in its protein structure
Protein structure
Proteins are an important class of biological macromolecules present in all organisms. Proteins are polymers of amino acids. Classified by their physical size, proteins are nanoparticles . Each protein polymer – also known as a polypeptide – consists of a sequence formed from 20 possible L-α-amino...
due to applied heat.
Thermostable proteins
Most life-forms on Earth live at temperatures of less than 50 °C, commonly from 15 to 50 °C. Above this, thermal energy may cause the unfoldingProtein folding
Protein folding is the process by which a protein structure assumes its functional shape or conformation. It is the physical process by which a polypeptide folds into its characteristic and functional three-dimensional structure from random coil....
of the protein structure to be irreversible, a condition understandably deleterious to continuing life-functions. The denaturing
Denaturation (biochemistry)
Denaturation is a process in which proteins or nucleic acids lose their tertiary structure and secondary structure by application of some external stress or compound, such as a strong acid or base, a concentrated inorganic salt, an organic solvent , or heat...
of proteins in albumen
Egg white
Egg white is the common name for the clear liquid contained within an egg. In chickens it is formed from the layers of secretions of the anterior section of the hen's oviduct during the passage of the egg. It forms around either fertilized or unfertilized egg yolks...
from a clear, nearly colourless liquid to an opaque white, insoluble gel is a common example of this.
Certain thermophilic life-forms
Thermophile
A thermophile is an organism — a type of extremophile — that thrives at relatively high temperatures, between 45 and 122 °C . Many thermophiles are archaea...
exist which can withstand temperatures above this. Examining homologous
Homology (biology)
Homology forms the basis of organization for comparative biology. In 1843, Richard Owen defined homology as "the same organ in different animals under every variety of form and function". Organs as different as a bat's wing, a seal's flipper, a cat's paw and a human hand have a common underlying...
proteins present in these thermophiles and other organisms reveal only slight differences in the protein structure. One notable difference is the presence of extra hydrogen bond
Hydrogen bond
A hydrogen bond is the attractive interaction of a hydrogen atom with an electronegative atom, such as nitrogen, oxygen or fluorine, that comes from another molecule or chemical group. The hydrogen must be covalently bonded to another electronegative atom to create the bond...
s in the thermophile's proteins—meaning that the protein structure is more resistant to unfolding. The presence of certain types of salt
Salt
In chemistry, salts are ionic compounds that result from the neutralization reaction of an acid and a base. They are composed of cations and anions so that the product is electrically neutral...
has been observed to decrease thermostability in the proteins of mesophile
Mesophile
A mesophile is an organism that grows best in moderate temperature, neither too hot nor too cold, typically between 25 and 40 °C...
s but not of hyperthermophile
Hyperthermophile
A hyperthermophile is an organism that thrives in extremely hot environments— from 60 degrees C upwards. An optimal temperature for the existence of hyperthermophiles is above 80°C . Hyperthermophiles are a subset of extremophiles, micro-organisms within the domain Archaea, although some bacteria...
s which may indicate that salt bridges
Salt bridge (protein)
Salt bridges fall into the broader category of noncovalent interactions. A salt bridge is actually a combination of two noncovalent interactions: hydrogen bonding and electrostatic interactions . This is most commonly observed to contribute stability to the entropically unfavorable folded...
have more impact on thermostability at high temperature than is currently widely acknowledged. Another factors of protein thermostability are compactness of protein structure, oligomerization, and strength interaction between subunits.
Thermostable enzyme
Enzyme
Enzymes are proteins that catalyze chemical reactions. In enzymatic reactions, the molecules at the beginning of the process, called substrates, are converted into different molecules, called products. Almost all chemical reactions in a biological cell need enzymes in order to occur at rates...
s such as Taq polymerase
Taq polymerase
thumb|228px|right|Structure of Taq DNA polymerase bound to a DNA octamerTaq polymerase is a thermostable DNA polymerase named after the thermophilic bacterium Thermus aquaticus from which it was originally isolated by Thomas D. Brock in 1965...
and Pfu DNA polymerase
Pfu DNA polymerase
Pfu DNA polymerase is an enzyme found in the hyperthermophilic archaeon Pyrococcus furiosus, where it functions in vivo to replicate the organism's DNA...
are used in polymerase chain reaction
Polymerase chain reaction
The polymerase chain reaction is a scientific technique in molecular biology to amplify a single or a few copies of a piece of DNA across several orders of magnitude, generating thousands to millions of copies of a particular DNA sequence....
s where temperatures of 94 °C or over are used to melt apart DNA
DNA
Deoxyribonucleic acid is a nucleic acid that contains the genetic instructions used in the development and functioning of all known living organisms . The DNA segments that carry this genetic information are called genes, but other DNA sequences have structural purposes, or are involved in...
strands.
Thermostable toxins
Certain poisonPoison
In the context of biology, poisons are substances that can cause disturbances to organisms, usually by chemical reaction or other activity on the molecular scale, when a sufficient quantity is absorbed by an organism....
ous fungi contain thermostable toxin
Toxin
A toxin is a poisonous substance produced within living cells or organisms; man-made substances created by artificial processes are thus excluded...
s, such as amatoxin
Amatoxin
Amatoxins are a subgroup of at least eight toxic compounds found in several genera of poisonous mushrooms, most notably Amanita phalloides and several other members of the genus Amanita, as well as some Conocybe, Galerina and Lepiota mushroom species.-Structure:The compounds have a similar...
found in the death cap
Death cap
Amanita phalloides , commonly known as the death cap, is a deadly poisonous basidiomycete fungus, one of many in the genus Amanita. Widely distributed across Europe, A. phalloides forms ectomycorrhizas with various broadleaved trees. In some cases, death cap has been introduced to new regions with...
and autumn skullcap
Galerina
Galerina is a genus of small brown-spored saprobic mushrooms, with over 300 species found throughout the world, from the far north to remote Macquarie Island in the Southern Ocean. Species are typically small and hygrophanous, with a slender and brittle stem. They are often found growing on wood,...
mushroom
Mushroom
A mushroom is the fleshy, spore-bearing fruiting body of a fungus, typically produced above ground on soil or on its food source. The standard for the name "mushroom" is the cultivated white button mushroom, Agaricus bisporus; hence the word "mushroom" is most often applied to those fungi that...
s. Therefore, applying heat to these deadly mushrooms will not remove its toxicity.