The total mass attenuation coefficients () (cm2/g) and atomic, molecular, and electronic effective cross sections have been calculated for nonessential amino acids that contain H, C, N, and O such as tyrosine, aspartate, glutamine, alanine, asparagine, aspartic acid, cysteine, and glycine in the wide energy region 0.015–15？MeV. The variations with energy of total mass attenuation coefficients and atomic, molecular, and electronic cross sections are shown for all photon interactions. 1. Introduction The total mass attenuation coefficients and atomic, molecular, and electronic effective cross sections are basic quantities required in determining the penetration of X-ray and gamma photons in matter [1]. The knowledge of mass attenuation coefficients of X-rays and gamma photons in biological and other important materials is of significant interest for industrial, biological, agricultural, and medical applications [2]. Reliable data on the transmission and absorption of X-rays and gamma rays in biological, shielding, and dosimetric materials are needed in medical physics and radiation biology as well as in many other fields of medicine, biological studies, and industry. Since amino acids are the building blocks of proteins, which are essential to all living matter, data on the total attenuation cross sections of amino acids are quite useful. Being the most abundant macromolecules that exist in living cells; amino acids constitute the largest living matter in all types of cells. The human body consists of 20 different amino acids. Out of the 20 amino acids, humans can produce 11, which are called essential amino acids. Nonessential amino acids (alanine, arginine, aspartic acid, cysteine, glutamic acid, glutamine, glycine, proline, serine, tyrosine, and asparagine) are those which can be produced from other amino acids and substances in the metabolism. The metabolism can shift into producing the amino acids that it requires for synthesizing proteins essential to our survival. Various diseases in human organism are related to amino acids. Phenylketonuria (PKU), caused by a deficiency of phenylalanine hydroxylase, is the most common clinically encountered inborn error of amino acid metabolism. Biochemically, it is characterized by accumulation of phenylalanine (and a deficiency of tyrosine). Albinism refers to a group of conditions in which a defect in tyrosine metabolism results in a deficiency in the production of melanin. These defects result in the partial or full absence of pigment from the skin, hair, and eyes. Albinism appears in different forms, and it
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