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Peptides are key regulators of life. They play crucial role in signaling mechanism. Even though a peptide is a short polymer of amino acids still it can regulate factors like blood pressure ex: hormone vasopressin. Peptides used as small molecule drugs, antigens, hormones and ligands in biotech industry. Peptide structural study is important to understand the information carried to cell. This book explains why peptide structure is complex. Peptide structures are stable and relatively rigid. Peptides with similar function typically have similar structure. Inside peptides similarity in structure tends to be more conserved than the sequence of amino acids. Although sequence is known it is hard to determine structure of a peptide.

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