HiLyte Fluor™ 555-IgY conjugate has been optimized in fluorophore/protein labeling ratio to ensure high fluorescent signal and uncompromised IgY function. HiLyte Fluor™ 555 is an orange flurophore with brighter fluorescence and better photostability than Cy3. The fluorescence of HiLyte Fluor™ 555 is only slightly red-shifted as compared to that of Cy3 dyes, resulting in an optimal match to filters designed for Cy3 dyes. The fluorescence of HiLyte Fluor™ 555 can be observed at excitation/emission wavelength of 553 nm/568 nm.