The overall goal of this project is to design, synthesize and apply cholesterol-based molecular probes that would aid in the understanding of cholesterol trafficking disorders. One such probe is a novel fluorescent cholesterol mimic that would serve as a general tool to track cholesterol movement in live cells or identify cholesterol localization in fixed cells. The other probes are cholesterol-based cross-linker molecular probes that consist of two cholesterol units are linked from head-to-tail. Our hypothesis behind this probe design is that these cross-linker probes can be used to identify and isolate protein pairs that participate in the transfer of cholesterol. Initially, these probes will be studied in the context of Niemann-Pick type C (NPC) disease since the proteins that are involved in the transport of cholesterol have been well studied. Once we have proven that this probe design works, we can utilize these types of probes in studies of other lipid storage diseases such as Tay-Sachs disease and progressive familial intrahepatic cholestasis.