Irreversible egg protein denaturation and loss of solubility, caused by the high temperature (while cooking it)

Denaturation is the alteration of a protein or nucleic acid's shape through some form of external stress (for example, by applying heat, acid or alkali), in such a way that it will no longer be able to carry out its cellular function. In biology, the shape and form of biological compounds such as proteins critically determine the function of the protein. Under stress, the shape and form (protein structure and protein folding) of the protein warp, and the protein changes (denatures) due to its inability to retain its old shape. Wikipedia does not have an article with this exact name. ... Wikipedia does not have an article with this exact name. ... Cooking is the act of preparing food. ... A representation of the 3D structure of myoglobin, showing coloured alpha helices. ... Look up nucleic acid in Wiktionary, the free dictionary. ... For other uses, see Heat (disambiguation) In physics, heat, symbolized by Q, is energy transferred from one body or system to another due to a difference in temperature. ... For other uses, see Acid (disambiguation). ... Alkaline redirects here. ... Proteins are an important class of biological macromolecules present in all biological organisms, made up of such elements as carbon, hydrogen, nitrogen, oxygen, and sulfur. ... Protein folding is the process by which a protein assumes its characteristic functional shape or tertiary structure, also known as the native state. ...

Common examples

When food is cooked, some of its proteins become denatured. This is why boiled eggs become hard and cooked meat becomes firm.

A classic example of denaturing in proteins comes from egg whites, which are largely egg albumins in water. Fresh from the eggs, egg whites are transparent and liquid. But by cooking they are turned opaque and white, and form an interconnected solid mass. The same transformation can be effected with a denaturing chemical. Pouring egg whites into a beaker of acetone will also turn egg whites opaque and solid. The skin which forms on curdled milk is another common example of denatured protein. And the traditional Peruvian cold appetizer known as ceviche is prepared by chemically "cooking" raw fish and shellfish in an acidic citrus marinade, without heat. Albumen redirects here. ... The egg white is a clear liquid (also called albumen or ovalbumin) contained within a birds egg. ... For other uses, see Liquid (disambiguation). ... For other uses, see Solid (disambiguation). ... The chemical compound acetone (also known as propanone, dimethyl ketone, 2-propanone, propan-2-one and β-ketopropane) is the simplest representative of the ketones. ... Curdled is also the name of a Quentin Tarantino film. ... Peruvian ceviche with lobster and shrimp Ceviche (also spelled as cebiche or seviche) is a form of citrus marinated seafood salad that originated in the Viceroyalty of Peru. ...

Although denaturation can be irreversible, an example of reversible denaturing in proteins is the modern permanent wave technique for curling or straightening hair. Turn of the century advertisement for Nesslers permanent wave machine. ...

Protein denaturation

Denatured proteins can exhibit a wide range of characteristics, from loss of solubility to communal aggregation. Solubility is a chemical property referring to the ability for a given substance, the solute, to dissolve in a solvent. ... Communal aggregation is the phenomenon of aggregation of the hydrophobic proteins to come closer and form the bonding between them, so as to reduce the total area exposed to water. ...

Background

Proteins are very long strands of amino acids linked together in specific sequences. A protein is created by ribosomes that "read" mRNA that is encoded by codons in the gene and assemble the requisite amino acid combination from the genetic instruction, in a process known as translation. The newly created protein strand then undergoes posttranslational modification, in which additional atoms or molecules are added, for example copper, zinc or iron. Once this post-translational modification process has been completed, the protein begins to fold (spontaneously, and sometimes with enzymatic assistance), curling up on itself so that hydrophobic elements of the protein are buried deep inside the structure and hydrophilic elements end up on the outside. The final shape of a protein determines how it interacts with its environment. A representation of the 3D structure of myoglobin, showing coloured alpha helices. ... Phenylalanine is one of the standard amino acids. ... Figure 1: Ribosome structure indicating small subunit (A) and large subunit (B). ... RNA codons. ... The structure of part of a DNA double helix Deoxyribonucleic acid, or DNA, is a nucleic acid molecule that contains the genetic instructions used in the development and functioning of all known living organisms. ... Translation is the second process of protein biosynthesis (part of the overall process of gene expression). ... Posttranslational modification is the chemical modification of a protein after its translation. ... For other uses, see Atom (disambiguation). ... 3D (left and center) and 2D (right) representations of the terpenoid molecule atisane. ... For other uses, see Copper (disambiguation). ... General Name, symbol, number zinc, Zn, 30 Chemical series transition metals Group, period, block 12, 4, d Appearance bluish pale gray Standard atomic weight 65. ... For other uses, see Iron (disambiguation). ... Neuraminidase ribbon diagram An enzyme (in Greek en = in and zyme = blend) is a protein, or protein complex, that catalyzes a chemical reaction and also controls the 3D orientation of the catalyzed substrates. ... In chemistry, hydrophobic or lipophilic species, or hydrophobes, tend to be electrically neutral and nonpolar, and thus prefer other neutral and nonpolar solvents or molecular environments. ... The adjective hydrophilic describes something that likes water (from Greek hydros = water; philos = friend). ...

When a protein is denatured, the secondary and tertiary structures are altered but the peptide bonds between the amino acids are left intact. Since the structure of the protein determines its function, the protein can no longer perform its function once it has been denatured. This is in contrast to intrinsically unstructured proteins, which are unfolded in their native state, but still functionally active. A representation of the 3D structure of the Myoglobin protein. ... In biochemistry, the tertiary structure of a protein is its overall shape. ... A peptide bond is a chemical bond that is formed between two molecules when the carboxyl group of one molecule reacts with the amino group of the other molecule, releasing a molecule of water (H2O). ... Intrinsically unstructured proteins, often referred to as naturally unfolded proteins or disordered proteins, are proteins characterized by their lack of stable secondary structure as isolated subunits. ... In biochemistry, the native state of a protein is its operative or functional form. ...

How denaturation occurs at levels of protein structure

See also: Protein structure

• In quaternary structure denaturation, protein sub-units are dissociated and/or the spatial arrangement of protein subunits is disrupted.
• Tertiary structure denaturation involves the disruption of:

• Covalent interactions between amino acid side chains (such as disulfide bridges between cysteine groups)
• Noncovalent dipole-dipole interactions between polar amino acid side chains (and the surrounding solvent)
• Van der Waals (induced dipole) interactions between nonpolar amino acid side chains.

• In secondary structure denaturation, proteins lose all regular repeating patterns such as alpha-helices and beta-pleated sheets, and adopt a random coil configuration.
• Primary structure, such as the sequence of amino acids held together by covalent peptide bonds, is not disrupted by denaturation.

Proteins are an important class of biological macromolecules present in all biological organisms, made up of such elements as carbon, hydrogen, nitrogen, oxygen, and sulfur. ... In biochemistry, many proteins are actually assemblies of more than one protein (polypeptide) molecule, which in the context of the larger assemblage are known as protein subunits. ... In biochemistry, the tertiary structure of a protein is its overall shape. ... Covalent bonding is a form of chemical bonding characterized by the sharing of one or more pairs of electrons between atoms, in order to produce a mutual attraction, which holds the resultant molecule together. ... The term Side chain can have different meanings depending on the context: In chemistry and biochemistry a side chain is a part of a molecule attached to a core structure. ... A disulfide bond (SS-bond), also called a disulfide bridge, is a strong covalent bond between two sulfhydryl groups. ... Cysteine is a naturally occurring, sulfur-containing amino acid that is found in most proteins, although only in small quantities. ... The Earths magnetic field, which is approximately a dipole. ... For other uses, see Solvent (disambiguation). ... In chemistry, the term van der Waals force originally referred to all forms of intermolecular forces; however, in modern usage it tends to refer to intermolecular forces that deal with forces due to the polarization of molecules. ... A representation of the 3D structure of the Myoglobin protein. ... Side view of an α-helix of alanine residues in atomic detail. ... Diagram of β-pleated sheet with H-bonding between protein strands The β sheet (also β-pleated sheet) is the second form of regular secondary structure in proteins — the first is the alpha helix — consisting of beta strands connected laterally by three or more hydrogen bonds, forming a generally twisted, pleated sheet. ... Illustration of a 3-dimensional polypeptide A random coil is a polymer conformation where the monomer subunits are oriented randomly while still being bonded to adjacent units. ... A protein primary structure is a chain of amino acids. ... A peptide bond is a chemical bond that is formed between two molecules when the carboxyl group of one molecule reacts with the amino group of the other molecule, releasing a molecule of water (H2O). ...

Loss of function

Most biological proteins lose their biological function when denatured. For example, enzymes lose their catalytic activity, because the substrates can no longer bind to the active site, and because amino acid residues involved in stabilizing substrates' transition states are no longer positioned to be able to do so. Ribbon diagram of the enzyme TIM, surrounded by the space-filling model of the protein. ... In chemistry and biology, catalysis is the acceleration (increase in rate) of a chemical reaction by means of a substance, called a catalyst, that is itself not consumed by the overall reaction. ... The active site of an enzyme is the binding site where catalysis occurs. ... The transition state of a chemical reaction is a particular configuration along the reaction coordinate. ...

Reversibility and irreversibility

In many proteins (unlike egg whites), denaturation is reversible (the proteins can regain their native state when the denaturing influence is removed). This was important historically, as it led to the notion that all the information needed for proteins to assume their native state was encoded in the primary structure of the protein, and hence in the DNA that codes for the protein. The structure of part of a DNA double helix Deoxyribonucleic acid, or DNA, is a nucleic acid molecule that contains the genetic instructions used in the development and functioning of all known living organisms. ...

Nucleic acid denaturation

The denaturation of nucleic acids such as DNA due to high temperatures, is the separation of a double strand into two single strands, which occurs when the hydrogen bonds between the strands are broken. This may occur during polymerase chain reaction. Nucleic acid strands realign when "normal" conditions are restored during annealing. If the conditions are restored too quickly, the nucleic acid strands may realign imperfectly. Look up nucleic acid in Wiktionary, the free dictionary. ... The structure of part of a DNA double helix Deoxyribonucleic acid, or DNA, is a nucleic acid molecule that contains the genetic instructions used in the development and functioning of all known living organisms. ... An example of a quadruple hydrogen bond between a self-assembled dimer complex reported by Meijer and coworkers. ... “PCR” redirects here. ... Annealing, in genetics, means for DNA or RNA to pair by hydrogen bonds to a complementary sequence, forming a double-stranded polynucleotide. ...

See also

• Protein folding
• Random coil

Protein folding is the process by which a protein assumes its characteristic functional shape or tertiary structure, also known as the native state. ... Illustration of a 3-dimensional polypeptide A random coil is a polymer conformation where the monomer subunits are oriented randomly while still being bonded to adjacent units. ...

External Links

• Using Denaturing SDS Gel Electrophoresis to Analyze Protein Structure and Function