Introduction

Protein Science is the study of protein molecules by researchers from varied fields of science, including chemistry, physics, mathematics, and biology. The primary interest of such research is on the structure, function, design, and possible applications of protein molecules. Proteins are considered a part of family called biological macromolecules and before broaching their molecular structure, clarity about the definition of molecule is essential. Defining a molecule in biochemistry is a little different than in general chemistry. In general chemistry, a molecule normally comprises of two or more atoms bonded covalently in specific stoichiometry and defined geometry. For example, ethane, C2H6 has well defined stoichiometry and defined geometry. But this is not the case with the chiral molecule or cis-trans isomers of biochemistry.

In biochemistry, molecules are considered as components which may or may not be bonded together covalently in all parts. Local and non-local interactions play important roles in their structures. For example in a protein molecule there are several weak interactions taking place in the functional structure of that protein, apart from covalent bonds. Also in a complex protein, non-covalent interactions play roles in the very assembling of the constituent molecules. Take the case of apoptosomes and proteosomes. The geometry of biological molecules are unique 3-D arrangements of its components. There are various levels of structural organization of such biological macromolecules. These levels of complexity, in them, are described below:

Four degrees of structure

• (a) Monomers are simple building blocks of macromolecules; and include sugars, amino acids and nucleotides.

• (b) Primary structure (1°) is the linear rearrangement of residues in the covalently linked polymers.

• (c) Secondary structure (2°) is a local regular structure, such as a-helix, b-sheets.

• (d) Tertiary structure (3°) is a global 3-D fold or topology, such as native structure of protein.

• (e) Quaternary structure (4°) is spatial arrangement of multiple distinct polymers, such as hemoglobin and proteosomes.

Biochemists devoted considerable effort over a very long time, employing a variety of biochemical techniques in order to understand the relationship between structure and function of biomolecules.

The current focus in life sciences is on learning more about proteomes with emphasis on the study of individual structures of biomolecules in order to understand their role in cellular functions. The tens of thousands of biomolecules encountered in living cells are mainly in two general groups.