The zero-mode waveguide is very useful for Ultraviolet Auto-fluorescence spectroscopy on tryptophan-carrying proteins like beta-galactosidase. With further modification of the zero-mode waveguide with a conical reflector, it is possible to study the dynamic process of smaller proteins like streptavidin with 24 tryptophan. , The modified zero-mode waveguide with a conical reflector can be further optimized to enhance the signal-to-noise ratio and reach the ultimate sensitivity of single tryptophan proteins like TNase.