The outer membrane proteins (OMPs) are beta-barrel membrane proteins that 
performed lots of biology functions. The discriminating OMPs from other non-OMPs 
is a very important task for understanding some biochemical process. In this 
study, a method that combines increment of diversity with modified Mahalanobis 
Discriminant, called IDQD, is presented to predict 208 OMPs, 206 transmembrane 
helical proteins (TMHPs) and 673 globular proteins (GPs) by using Chou's pseudo 
amino acid compositions as parameters. The overall accuracy of jackknife 
cross-validation is 93.2% and 96.1%, respectively, for three datasets (OMPs, 
TMHPs and GPs) and two datasets (OMPs and non-OMPs). These predicted results 
suggest that the method can be effectively applied to discriminate OMPs, TMHPs 
and GPs. And it also indicates that the pseudo amino acid composition can better 
reflect the core feature of membrane proteins than the classical amino acid 
composition.