Amino Acids and Protein Solubility

Proteins are essential biological macromolecules composed of amino acids. Each amino acid contains a central carbon atom, an amino group, a carboxyl group, a hydrogen atom, and a distinctive R group (side chain) that determines the properties of the amino acid. Proteins can fold into complex three-dimensional structures that determine their function in biological processes.

Consider the following amino acids: Glycine (Gly), Alanine (Ala), and Serine (Ser). Glycine has a hydrogen atom as its R group, making it the simplest amino acid. Alanine has a methyl group as its R group, while Serine contains a hydroxymethyl group. The polarity of the side chains plays a vital role in protein solubility and function.

Which of the following amino acids would most likely enhance the solubility of a protein in an aqueous environment due to its polar side chain?