This hydroxyl group has the potential to form multiple hydrogen bonds with neighboring amino acid residues, therefore mutations must be made to these neighboring amino acids in order for interactions of Stronger H bonds can form between the receptor and testosterone. The same principle also applies to amino acids close to the carbonyl group. Serine or tyrosine can be used to replace neighboring amino acids to create more H-bonds between the receptor and testosterone. With these additional H-bonds, the affinity of testosterone is believed to increase