Principles of Protein Structure - H. Schultz 1982

Amino acids
20 canonical amino acids

At present, the fundamental scheme of the Organization of living matter can be considered well-established. Nucleic Acids carry all the Genetic information encoded in The sequence of four different nucleotide bases. There are two Types of Nucleic acids. The more stable deoxyribonucleic acid (DNA) serves as the repository of information. The less stable ribonucleic acid (RNA), transcribed from DNA, acts as a template that translates the nucleotide text into Amino acid sequences of Proteins via the ribosomal machinery. Proteins are involved in virtually all types of biological activity within the Organism.

This chapter examines the 20 canonical amino acid residues found in proteins. They are listed in Table 1.1 according to their relative Abundance; commonly used three-letter and one-letter Abbreviations are provided alongside mnemonic AIDS to facilitate their memorization. The molecular weights of the residues range from 57 to 186 (with an average value of ~ 110). Thus, a protein with a Molecular Weight of 33,000 contains approximately 300 residues. Amino Acids can be classified into polar and non-polar based on The properties of their side chains. Polar side chains can be further subdivided into neutral, basic, or acidic. Figure 1.1 illustrates the side chains of the 20 most common amino acids, with residues of similar properties grouped together.