Proline is an a-imino acid; the others are a-amino acids

The basic amino acids in natural proteins are all L-a-type (except glycine)

nonpolar amino acids

polar neutral amino acids

acidic amino acids

basic amino acids

Common amino acids: 20 types

Standard/basic amino acids: 22 types

Essential amino acids for human body: 8 types

colorless crystal

Higher melting point

Solubility in pure water varies greatly

have different taste

Insoluble in organic solvents such as ether (except proline)

is its characteristic constant

pI=1/2(pK1 pK2)

The solubility of amino acids is minimum at the isoelectric point

Maximum absorption value at 280nm

Heating reaction with amino acids produces a blue-purple substance

Yellow substance (Sanger reaction) with a-amino acid under weak base conditions

C-N

Definition: A compound in which amino acids are linked by peptide bonds

Oligopeptide: A peptide generally composed of less than 10 amino acids

Polypeptide: composed of more than 10 amino acids

Direction: N end to C end

amino acid residue

composition

Features

effect

A type of peptide that inhibits or kills bacteria by damaging cell membranes

D L type alternating

Amino acid group protection

peptide condensation reaction

Remove protecting groups

(hat elevator)

Purification of protein samples

Determination of the number of polypeptide chains

Analysis of amino acid composition

Analysis of N-terminal amino acids

Several peptide units in the main chain skeleton of the polypeptide chain each coil or fold along a certain axis, and form a regular conformation with hydrogen bonds as the main secondary bonds.

The basic unit composed of a peptide bond and two adjacent a-carbon atoms is called a peptide unit or peptide plane

The main chain of a polypeptide chain can be regarded as composed of a series of rigid peptide planes

The C-N bond in the main chain has the nature of a partial double bond and cannot rotate freely.

a-helix

b-fold

b-corner

random skein

The overall arrangement of all atoms or groups in a peptide chain of a protein in three-dimensional space is called the tertiary structure

Describe the entire three-dimensional folding of a polypeptide chain

hydrogen bond

hydrophobic bond

Salt bond (ionic bond)

Allocation key

van der Waals force

Also called motif or primitive

Motif is also called motif or motif

Refers to the fact that sequentially adjacent secondary structures within a polypeptide are often close to each other in spatial folding and interact with each other to form regular, spatially identifiable secondary structure aggregates.

Refers to an independent folding unit within the tertiary structure of a protein, usually a combination of several motif structural units, and refers to a protein structure between the secondary structure and the tertiary structure.

Certain kinds of domains have different biological activities

Different functions of proteins come from the diversity of domain combinations

Myoglobin is a protein with a typical tertiary structure

The ferrous ion in the center of the heme group in myoglobin can form 6 coordination bonds, one of which binds O2

A protein composed of two or more polypeptide chains has a quaternary structure

Some proteins have only one polypeptide chain, so they have no quaternary structure.

Subunit: the peptide chain that makes up a protein

Quaternary structure: a more complex protein spatial structure formed by two or more subunits interacting through non-covalent bonds

It consists of one polypeptide chain or two or more peptide bonds linked by disulfide bonds.

Has its own primary, secondary and tertiary structure

No sulfhydryl group between subunits

Proteins with quaternary structure composed of 2-10 subunits are called oligomers, and proteins composed of more subunits are called multimers.

Generally, subunits are inactive and become active when they form a protein with a complete quaternary structure.

If the protein subunits are the same, they are called homologous proteins

The chemical bonds that maintain the quaternary structure include hydrophobic bonds, salt bonds, hydrogen bonds, van der Waals forces and disulfide bonds

Hydrophobic bonds play a major role

is a molecule with a typical quaternary structure

Compare with myoglobin

Composed of four subunits, each subunit is connected to a molecule of heme

hemoglobin

S-shaped oxygenation curve

The primary structure of a protein determines its spatial conformation and biological function

Different proteins and peptides have different functions. The fundamental reason is that their primary structures are different.

Definition: The phenomenon that the binding of a protein to an allosteric agent causes a change in the spatial conformation of the protein, thereby leading to a change in the biological activity of the protein.

The synergistic effect is for the active center and is different from the allosteric effect.

Can increase protein activity or decrease protein activity

Although the primary structure of some proteins remains unchanged, the protein folds incorrectly and its conformation changes, which also affects its function.