fibrous protein

globular protein

Membrane Protein

Simple protein (consisting only of peptide chains)

Binding protein (simple protein prosthetic group)

enzyme

regulatory protein

storage protein

transporter protein

motor protein

Defense proteins and toxin proteins

receptor protein

scaffold protein

structural protein

Abnormally functional proteins

In a broad sense, it refers to compounds with both amino and carboxyl groups; there are 20 amino acids used by organisms to synthesize proteins; except for proline, all others are a-amino acids

Acid hydrolysis: does not cause racemization and obtains L-amino acids

Alkaline hydrolysis: racemization occurs and a mixture of L/D-amino acids is obtained, but tryptophan is not destroyed

Enzyme hydrolysis: does not produce racemization and does not destroy amino acids, but requires multiple enzymes and is time-consuming

Except for glycine, the rest of the a-amino acids are optically active (because their a-C are all asymmetric carbon atoms) and all have L/D-form; except for glycine and proline, all those obtained by protein hydrolysis are L-a-amino acids; D-amino acids found in some antibiotics

Polarity of R group

Structure of R base

It is not directly involved in protein synthesis and is a product of post-translational modification of common amino acids; although selenocysteine ​​(sec) and pyrrolysine (ply) are uncommon amino acids, they can be directly involved in protein synthesis. among

It is not directly involved in protein synthesis, nor is it a product of common post-translational modification of amino acids.

Colorless crystal with extremely high melting point, soluble in water but not in organic solvents

Optical activity

Configuration (characteristics of the general structural formula)

Light absorption: The maximum UV absorption peak of protein is 280nm. Its UV absorption ability mainly comes from proteins containing benzene rings (conjugation effect caused by alternating single and double bonds of benzene rings), phenylalanine and tyrosine (originally tryptophan acidic, but there is very little tryptophan in protein, so it mainly comes from these two)

When the degree of dissociation of the amino and carboxyl groups on the amino acid molecules in the amino acid solution is the same, that is, the net charge carried by the amino acid is 0, the pH of the solution at this time is the size of the isoelectric point, and the isoelectric point is represented by PI, that is PH=PI, at this time the solubility of amino acids is minimum; when PH>PI, the solution is negatively charged; when PH<PI, the solution is positively charged

Reactions in which a-amino group participates:

Reaction in which a-amino and a-carboxyl groups participate together

Side face R base participation reaction

Reaction in which a-carboxyl group participates