structure of a protein can be represented by one of the four options.Each option has its own peculiarities.So, there is a quaternary, ternary, secondary and primary structure of the protein.
Last on the list level is a linear polypeptide chain of amino acids.Amino acids joined together by peptide bonds.The primary structure of a protein is the simplest level of organization of the molecule.By covalent peptide bonds between the alpha-amino group of one amino acid and the alpha-carboxyl group of another molecule provides high stability.
In the formation of peptide bonds in cells activated first carboxyl group.Once there is a connection with an amino group.Approximately the same is carried out laboratory polypeptide synthesis.
peptide bond, is a repeat unit of the polypeptide chain has a number of features.Under the influence of these features not only form the primary structure of the protein.They affect both the higher organizational levels of the polypeptide chain.Among the main features isolated coplanarity (ability of all the atoms that are included in the peptide group are in the same plane) with respect to substituents trans-N-C linkages, the property exist in 2 resonance forms.Peptide bond to features include the ability to form hydrogen bonds.Wherein each peptide of the group may be formed by two hydrogen bonds with other groups (including peptide).However, there are exceptions.These include peptide groups with the amino groups of hydroxyproline or proline.They can form only one hydrogen bond.This affects the formation of protein secondary structure.Thus, the portion where is hydroxyproline or proline, the peptide chain is easily bent due to the fact that there is a second hydrogen bonding, which would keep it (as usually).
name peptides formed from the names of amino acids that make them.Dipeptide give two amino tripeptide - three tetrapeptide - four, and so on.Each polypeptide chain (or peptide) of any length is present N-terminal amino acid, which contains a free amino group and the C-terminal amino acid, in which there is a free carboxyl group.
properties of proteins.
In studying these compounds, scientists interested in several issues.Investigators especially have sought to find out the dimensions, shape and determine molecular weight proteins.It should be noted that it was quite a challenge.The difficulty is that the determination of the relative molecular weight to increase the boiling point of solutions of proteins (as occurs in other substance) is not possible, because the protein solutions can not boil.A definition of the indicator in accordance with the lowering of the freezing point of giving inaccurate results.In addition, proteins in pure form never occur.However, using methods developed it was found that the molecular weight ranges from 14 to 45 thousand or more.
One of the important characteristics of the compounds is a fractional salting.This process is a selection of proteins from solution after the addition of salt solutions of different concentrations.
Another important characteristic is the denaturation.This process occurs in the deposition of proteins with heavy metals.Denaturation is the loss of the natural properties.This process involves the conversion of different molecules apart breaking the polypeptide chain.In other words, the primary structure of protein denaturation remains unchanged.
