core structure of proteins and proteids polypeptide chain of the protein molecule and may consist of one, two or more circuits.Nevertheless, physical, biological and chemical properties of biopolymers are caused not only a general chemical structure which may be a "meaningless", but also by other levels of the organization of the protein molecules.
primary structure of a protein is determined by qualitative and quantitative amino acid composition.The peptide bonds are the basis of primary structure.For the first time this hypothesis suggested in 1888 Danilevskiy and later his suspicions were confirmed by peptide synthesis, which is carried out by E. Fischer.The structure of the protein molecule was studied in detail Danilevskiy and E. Fischer.According to this theory, protein molecules consist of a large number of amino acid residues joined by peptide bonds.A protein molecule may have one or more polypeptide chains.
In the study of the primary structure of proteins using chemical agents and proteolytic enzymes.For example, using Edman degradation is very convenient to identify the terminal amino acids.
protein secondary structure shows the spatial configuration of the protein molecule.The following types of secondary structure of alpha-helix, beta-helical, collagen helix.Scientists have found that the structure of peptides is most common alpha-helix.
protein secondary structure is stabilized by hydrogen bonds.The latter arise between hydrogen atoms bonded to an electronegative nitrogen atom one peptide bond, and a carbonyl oxygen atom of the fourth one of its amino acids, and they are directed along the spiral.Energy calculations show that the polymerization of these amino acids is more efficient right alpha-helix, which is present in the native protein.
protein secondary structure: Beta-sheet structure
polypeptide chains in beta-pleated fully extended.Beta-sheet formed by the reaction of two peptide bonds.This structure is typical for fibrous proteins (keratin, fibroin, etc.).In particular, beta-keratin characterized by a parallel arrangement of polypeptide chains which are further stabilized by the interchain disulfide bonds.The silk fibroin adjacent antiparallel polypeptide chains.
secondary structure of proteins: collagen helix
Education consists of three circuits spiralized tropocollagen, which has the shape of the rod.Helical twist chain and form superhelix.Helix stabilized by hydrogen bonds between hydrogen occurring peptide amino groups of amino acid residues of one chain and the oxygen of the carbonyl group of the amino acid residue of another chain.Presented collagen structure gives high strength and elasticity.
tertiary structure of the protein
Most proteins in the native state have a very compact structure, which is determined by the shape, size and polarity of amino acid residues, and the amino acid sequence.
significant influence on the formation of the native conformation of the protein or its tertiary structure having hydrophobic and ionic interactions, hydrogen bonds, and others. Under the influence of these forces is achieved thermodynamically expedient conformation of the protein molecule and its stabilization.
quaternary structure
This kind of structure of the molecule is the result of association of several subunits into a single complex molecule.The structure of each subunit includes primary, secondary and tertiary structures.
