What are the effects of acidic and alkaline solvent systems on the dissociation of polar groups of a

In acidic solution, it is conducive to the basic ionization of amino acids, the amino group binds protons, and the whole molecule is positively charged; On the contrary, the acidic ionization of the carboxyl group in the alkaline solution is favorable, and the amino acid molecule as a whole is negatively charged.

Mainly look at the R group linked to the alpha carbon, if it contains polar groups (such as hydroxyl group, amino group, carboxyl group, etc.), it is a polar amino acid; If they are all hydrocarbons, they are non-polar amino acids.

Polar amino acids include: serine (SER), tyrosine (TYR), cysteine (cys), methionine (MET), asparagine (ASN), glutamine (GLN), threonine (THR), lysine (LYS), arginine (ARG), histidine (his).

Non-polar amino acids include: alanine (ala), valine (val), leucine (leu), isoleucine (ile), proline (pro), phenylalanine (phe), tryptophan (TRP), methionine (met).

Polar amino acids are hydrophilic, and non-polar amino acids are hydrophobic, so when the peptide chain is folded, the polar amino acids are often on the outside and the non-polar amino acids are wrapped on the inside.

Pure hand play, welcome to ask,

The concepts polar and nonpolar are often associated with hydrophobicity and hydrophilicity.

According to the principle of similarity compatibility, polar solutes are dissolved in polar solvents, and non-polar solutes are dissolved in non-polar solvents. Water is often used as a solvent, which is polar. Therefore, polar amino acids can be regarded as amino acids that are soluble in water, and vice versa, they are not easily soluble in water.

On the other hand, you can also look at the structure of amino acids, the properties of amino acids mainly depend on the side chain group R, if R is only composed of H or C and H elements, they are all hydrophobic, if it contains polar side chain groups, such as -OH, -SH, -COOH, -N Ding2, etc., then this amino acid is polar.

Generally speaking, it is associated with hydrophilic and hydrophobic, for example, most proteins are polar amino acids on the surface, and non-polar amino acids are inside, under normal circumstances, these proteins are soluble in water, but when they are denatured, the internal non-polar amino acids are exposed, and then the protein is precipitated.

Because water is polar, it can be considered that polarity is hydrophilic and non-polar is hydrophobic.

Amino acids can be divided into:

1. 7 non-polar hydrophobic amino acids: glycine (GLY), alanine (ala), valine (val), leucine (LEU), isoleucine (LLE), phenylalanine (PHE), proline (PRO).

2. 8 polar hydrophilic neutral amino acids: tryptophan (TRP), serine (SER), cysteine (cys), methionine (MET), asparagine (ASN), glutamine (GLN), threonine (THR), tyrosine (TYR).

3. 2 acidic amino acids: glutamic acid (GLU), aspartic acid (ASP) 4. 3 basic amino acids: lysine (LYS), arginine (ARG), histidine (his).

Is LZ satisfied?

Negative electrolysis of R group amino acids can occur: The R side chain groups of amino acids in this group are dissociated in a neutral solution to produce negatively charged amino acids. Including aspartic acid ASP, glutamic acid glu; These two amino acids are also commonly referred to as acidic amino acids.

Positive electrolysis of R group amino acids: The R side chain group of this group of amino acids can be dissociated in a neutral solution to produce positively charged amino acids. Includes:

Histidine his, lysine lys, arginine arg; These three amino acids are also commonly referred to as basic amino acids.

Due to the different relative strengths and numbers of carboxyl and amino groups in various amino acids, the isoelectric points of amino acids are different, resulting in a charge.

Non-polar amino acids: propylvalerian, bright, isobright, proline, phenylacrylic, methyl sulfide, non-polarity: glycan, silk, cysteine, asparagine, glutamine, positively charged: lysine group.

Negative Electricity: Tiandong Valley.

Polarity can be simply understood as soluble in water (similarly soluble, water is polar) Glycine (GLY) is sometimes classified as a non-polar reference because the R-based side chain is between polar and non-polar