▁has ▁found ▁w ides p read ▁use ▁as ▁a ▁hist och em ical ▁st ain ▁for ▁ch ol ester ol . ▁ ▁This ▁method ▁of ▁detect ing ▁ch ol ester ol ▁in ▁cell ▁memb ran es ▁is ▁used ▁clin ically ▁in ▁the ▁study ▁and ▁diagn osis ▁of ▁Type ▁C ▁Niem ann - P ick ▁disease . ▁ ▁It ▁is ▁also ▁used ▁in ▁cell ular ▁bi ology ▁as ▁an ▁in hib itor ▁of ▁the ▁ra ft / ca ve ola e ▁end oc yt osis ▁path way ▁on ▁m amm al ian ▁cells ▁( at ▁concentr ations ▁around ▁ 3   µ g / m L ) ▁ ▁Types ▁Filip in ▁is ▁a ▁mixture ▁of ▁four ▁components ▁- ▁fil ip in ▁I ▁( 4 % ), ▁II ▁( 2 5 % ), ▁III ▁( 5 3 % ), ▁and ▁IV ▁( 1 8 %) ▁- ▁and ▁should ▁be ▁referred ▁to ▁as ▁the ▁fil ip in ▁complex . ▁ ▁The ▁major ▁component , ▁fil ip in ▁III , ▁has ▁the ▁structure ▁which ▁was ▁proposed ▁by ▁C eder ▁and ▁Ry h age ▁for ▁the ▁fil ip in ▁complex . ▁▁▁ ▁Filip in ▁I , ▁which ▁has ▁been ▁difficult ▁to ▁character ize , ▁is ▁probably ▁a ▁mixture ▁of ▁several ▁components ▁each ▁having ▁two ▁hydro x yl ▁groups ▁fewer ▁than ▁fil ip in ▁III . ▁▁▁ ▁Mass ▁spect rom etry ▁and ▁N MR ▁data ▁indicate ▁that ▁Filip in ▁II ▁is ▁ 1 '- de ox y - fil ip in ▁III . ▁▁▁ ▁Filip in ▁IV ▁is ▁is