In the structure of secondary proteins,the folding of the polypeptide chain is caused by which bond?

The triple helical structure of collagen was published in Nature in $1954$, and the analysis of the allowed conformations of proteins was performed through the use of the:

$A$: The polypeptide coil of collagen helix is strengthened by the establishment of hydrogen bonds between the $>NH$ group of the glycine residue of each strand and the $-CO$ group of the other two strands.
$R$: In the collagen helix,a locking effect also occurs with the help of proline and hydroxyproline amino acids.

How many water molecules are released during the formation of a dipeptide when two amino acids bind (in $-H_2O$)?

Protein on reaction with which yields Ruhemann's purple?

Which conjugated protein is synthesized by copper?