What maintains the secondary structure of a protein?

hydrogen bonds

Explanation:

Proteins are folded into their secondary structure via hydrogen bonds-between the amino hydrogen and carboxyl oxygen atoms. Secondary structure is an intermediate, before proteins gets its 3D shape (conformation), tertiary and quaternary structure. Mos commonly found secondary structures of the protein are:

alpha helices-backbone N−H group forms a hydrogen bond with the backbone C=O group of the amino acidwhich is three or four residues apartbeta sheets- laterally connected polypetpide chains with two or three hydrogen bonds

Could you elaborate?

When you are making a guess you are forming a hypothesis