During protein folding, which of the following interactions help stabilize secondary, tertiary, or quaternary structure?Hydrogen bondsIonic bondsvan der Waals forcesAmide bonds

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11ecba2d_0e87_d44c_a3bf_4bad99ae02bb_MD0008_00 Proteins are polypeptides with varying levels of structure. Various chemical interactions underly the secondary, tertiary, and quaternary structures of a native protein, including hydrogen bonding, ionic bonding (tertiary and quaternary structure only), and van der Waals forces (Numbers I, II, and III). Secondary structure is driven and reinforced by hydrogen bonding between a carbonyl oxygen and an amino hydrogen of nearby amino acids. Hydrogen bonds bend the polypeptide into α-helices and β-pleated sheets, the main components of secondary structure. Tertiary structure is formed by the folding of α-helices and β-pleated sheets into a three-dimensional structure. Although this folding is driven by hydrophilic and hydrophobic interactions, the resulting structure is reinforced by van der Waals forces, hydrogen bonding between side chains, and ionic bonds (electrostatic interactions or "salt bridges") formed between acidic and basic side chains. Tertiary structure may also be reinforced by disulfide bonds (S-S), which are covalent bonds between thiol groups (-SH) of 2 cysteine side chains. Quaternary structure refers to the assembly or 2 or more polypeptide chains (subunits) and is reinforced by the same chemical interactions as tertiary structure. (Number IV) The primary structure of a protein (linear sequence of amino acids) is maintained by amide bonds (ie, peptide bonds) that link the amino acids into a polypeptide chain. After denaturation, the primary structure remains intact; therefore, renaturation would not require reinstatement of amide bonds. Educational objective: Primary protein structure is maintained by peptide bonds. Secondary structure (α-helices and β-pleated sheets) is maintained by hydrogen bonds. Tertiary structure (three-dimensional conformation) and quaternary structure are maintained by van der Waals forces, hydrogen bonds, ionic bonds, and disulfide bonds. Complete denaturation disrupts bonding in all other levels of protein structure except primary structure.

During Protein Folding, Which of the Following Interactions Help Stabilize