How many different proteins composed of 100 amino acids could possibly exist?

The number of possible proteins in humans is twenty.

The number of amino acids you can use it's called n, and the number of possible proteins then will be P=20^n.

In this case, you have 100 amino acids if you replace the n in the equation P=20^100 possible proteins.

the electromagnetic spectrum includes, from longest wavelength to shortest: radio waves, microwaves, infrared, optical, ultraviolet, x-rays, and gamma-rays.