β-pleated sheets form when two or more polypeptide chain segments line up side by side. Each individual segment is referred to as β-strand. Rather than being coiled, each β-strand is fully extended. β-pleated sheets are stabilised by hydrogen bonds that are formed between the polypeptide backbones N—H and carbonyl group of adjacent chain. There are…
α-helix is spiral in shape and has a rigid arrangement of polypeptide chain as proposed by Pauling and Corey (1981). The salient features of α-helix are as follows: Figure 3.5 Structure of α-helix
The protein gets folded, and the hydrogen bonding between the neighbouring amino acids results in the formation of a rigid and tubular structure called helix. This constitutes the secondary structure of proteins. Two types of secondary structure, α-helix and β-sheet, are mainly identified.
The primary structure of protein refers to the number sequence of amino acids and the constituent units of polypeptide chain. The main mode of linkage of amino acids in proteins is the peptide bonds which link the α-carboxyl group of amino acid residue to the α-amino group of the other. Linus Pauling and Robert Corey…
Linderstrom-Lang first defined the four basic structural levels of organisation, which are referred to as primary, secondary, tertiary, and quaternary. Three of these structural levels (primary, secondary, and tertiary) can exist in molecules composed of a single polypeptide chain, whereas the fourth (quaternary) involves interactions of polypeptide within a multi-chained protein molecule. The basic structure of…
The nutritive value of proteins is determined by the composition of essential amino acids. From the nutritional point of view, proteins are classified into three categories.