Main elements: carbon, hydrogen, oxygen, nitrogen, sulfur.

Features: Most proteins have similar nitrogen content, with an average of 16%. Therefore, nitrogen content is commonly used to determine protein content, also called Kjeldahl nitrogen determination method.

The amino acids that make up human proteins, except glycine, are all L-a amino acids

Classification of amino acids

Sexual dissociation and isoelectric point

Ultraviolet absorption properties: There is a maximum absorption peak at 280nm, so the light absorption value of protein at 280nm can be measured to quantitatively analyze the protein content in the solution.

Ninhydrin reaction: The color of the blue-violet compound is directly proportional to the ammonia produced by the decomposition of amino acids. Based on this, quantitative analysis of amino acids can be carried out.

a-helix

β-sheet

β-turn

random curls

secondary structure polymer

Motif: a region with a specific spatial conformation and specific function

Definition: The relative spatial position of all amino acid residues in the entire peptide chain

domain

There are two or more peptide chains, which refers to the mutual relationship and spatial position between the subunits of multimeric protein molecules.

Chemical bonds: hydrophobic bonds, hydrogen bonds, ionic bonds

Molecular diameter 1~100nm

Provide a hydration film on its surface

Protein surfaces have homogeneous charges

The characteristic absorption peak at 280nm can be used for quantitative determination of protein.

Destroy non-covalent bonds and disulfide bonds without destroying the primary structure

biuret reaction

Ninhydrin reaction

The biological structure of cells, material transport, catalytic function, information exchange, immune function, maintaining the body's acid-base balance, maintaining osmotic pressure...

Protein primary structure is the basis for higher-order structure and function

Hemoglobin transports oxygen