So this is pronounced cystine. This is pronounced cysteine. So we have the hydrophobic interactions that basically drive the formation of that tertiary structure. And then that hydrophobic core is held together by Van der Valle's interaction. And we can also have a special type of covalent bond known as the disulfide bridge that also holds our structure together. So here we have one disulfide bond, a second disulfide bond, and a third disulfide bond between these 15 amino acids.