Multiple choice Which of the photoreceptors use FAD as chromophore? Phototropins Phytochrome Cryptochrome BLUF-proteins Only 1 and 2 Only 1 and 3 Only 2 and 3 Only 2 and 4 Only 3 and 4 Reveal answer Fill a bubble to check yourself E Correct answer Explanation Correct answer. The cryptochrome and the BLUF-proteins use flavin adenine dinucleotide (FAD) as chromophore.