Cholesteryl hemisuccinate is a detergent that is often used to replace cholesterol 
in crystallization of membrane proteins. Here we employ atomistic molecular dynamics 
simulations to characterize how well the properties of cholesteryl hemisuccinate 
actually match those of cholesterol in saturated protein-free lipid membranes. 
We show that the protonated form of cholesteryl hemisuccinate mimics many of the 
membrane properties of cholesterol quite well, while the deprotonated form of 
cholesteryl hemisuccinate is less convincing in this respect. Based on the results, 
we suggest that cholesteryl hemisuccinate in its protonated form is a quite faithful 
mimic of cholesterol for membrane protein crystallization, if specific cholesterol-protein 
interactions (not investigated here) are not playing a crucial role.