It should therefore be as flexible as a simple hydrocarbon chain. Note that flexing in a covalent structure does not occur by bending bonds, and the normal tetrahedral or trigonal planar bond angles are maintained. This is called the denatured state of the protein. Proteins become denatured at elevated temperature or in the presence of disruptive solvents. Because there is no orderly arrangement, denatured protein is non-functional.
Most proteins also have an ordered arrangement called the native state.
Biochemists often work with proteins in ice baths to keep the temperature down and preserve the native state. If the X-ray wavelength is known, the size of the repeat pattern in the protein can be calculated. For alpha-keratin , periodic repeat distances were 1.5 and 5.4 angstroms. The diffraction patterns also showed characteristic missing reflections that suggested a helical structure. For fibroin or beta keratin , periodic repeats were 3.5 and 7.0 angstroms .