In this study, we propose a novel method to predict the solvent accessible 
surface areas of transmembrane residues. For both transmembrane alpha-helix and 
beta-barrel residues, the correlation coefficients between the predicted and 
observed accessible surface areas are around 0.65. On the basis of predicted 
accessible surface areas, residues exposed to the lipid environment or buried 
inside a protein can be identified by using certain cutoff thresholds. We have 
extensively examined our approach based on different definitions of accessible 
surface areas and a variety of sets of control parameters. Given that 
experimentally determining the structures of membrane proteins is very difficult 
and membrane proteins are actually abundant in nature, our approach is useful 
for theoretically modeling membrane protein tertiary structures, particularly 
for modeling the assembly of transmembrane domains. This approach can be used to 
annotate the membrane proteins in proteomes to provide extra structural and 
functional information.