Primary structure: *The order of amino acids in proteins *To a certain extent, it also includes other covalently bound components

right hand spiral

The hydrogen bond formed by the amino group and the carbonyl group is the main force stabilizing the helix.

3.6 amino acids per turn of helix

Side chain groups are located outside the helix

Several polypeptide chains are arranged in forward or antiparallel directions

Amino and carbonyl groups form interchain hydrogen bonds

The side chains extend above and below the sheet

is the most extended conformation of a peptide chain

Smaller side chain groups bring the peptide chains closer to each other, which is beneficial to the formation of β-sheets

1. Proposed by Pauling et al. in 1951, it exists in both fibrous and globular proteins. 2. The polypeptide chain is quite extended, folded into a zigzag structure between adjacent peptide units (peptide planes), and the side chains are staggered above and below the zigzag structure - see structure. 3. More than two sections of this structure are arranged in parallel, and the two chains can be parallel or anti-parallel. 4. Hydrogen bonds are formed between the peptide chains between the two chains to stabilize the folded structure. The hydrogen bonds are perpendicular to the long axis of the helix (anti-parallel). 5. The distance between adjacent amino acids is 0.35nm.

Determination of N-terminal amino acids of polypeptides

Determination of the C-terminal amino acid of polypeptides

Most active peptides in the body are processed from inactive protein precursors through special enzyme systems (such as polypeptide chain cleavage, acylation, acetylation, etc.)

Separation and purification of natural active peptides (salting out, chromatography, selective precipitation, etc.)

Preparation of active peptides through chemical synthesis (can be used for clinical diagnosis, treatment, and prevention of certain major diseases)

Primary structure: *The order of amino acids in proteins *To a certain extent, it also includes other covalently bound components

The secondary structure of a protein refers to the local spatial conformation of the backbone atoms of a polypeptide chain. It is a skeleton formed by the repeated arrangement of three atoms: N (amino nitrogen), Ca (a-carbon atom) and Co (carboxyl carbon). chain; the R group of each amino acid residue constitutes the side chain of the polypeptide chain. The secondary structure refers to the conformation of the main chain skeleton atoms and does not involve the R group.

Main types of protein secondary structures

Super secondary structure: motif

The tertiary structure of a protein is the overall spatial arrangement of all atoms in the entire polypeptide chain. That is, on the basis of the secondary structure, the interaction of the side chain R groups is added, and the entire polypeptide chain is organized. formed spatial structure. In a water environment, polar groups are often located on the surface of protein molecules, and non-polar groups are often located inside protein molecules.

Factors that maintain the stability of the three-level structure

Tertiary structure of myoglobin

domain

A multimeric protein composed of multiple polypeptide chains. Each polypeptide chain folds to form its own independent tertiary structure and is associated together. These polypeptide chains that constitute the multimeric protein are the subunits of the protein. Subunits The association between bases is the quaternary structure of the protein, including the spatial arrangement and interactions of subunits.