The direct transfer of membrane proteins from human platelets to the liposomal fraction was examined, particularly in relation to platelet activation during the process. The incorporation of an artificial boundary lipid, 1,2-dimyristoylamido-1,2-deoxyphosphatidylcholine (DDPC), in the interacting liposome considerably enhanced the efficiency of the protein transfer. The transfer proceeded with neither significant activation nor lysis of the platelet, and the activation of the platelet with thrombin did not affect the amount of the transferred proteins. A wide range of platelet membrane proteins was transferred, and they were almost comparable to those in a sample prepared by glycerol lysis/centrifugation. In addition, they included the major surface glycoproteins GPIIb and GPIIIa without noticeable contamination of soluble cytosol proteins. The protein transfer method is a one-pot process and clearly more convenient than the conventional 'extract and reconstitute' approach. These results strongly support the use of the transfer process, especially with DDPC, as an alternative to the conventional detergent-solubilization or the solvent-extraction methods for preparation of samples of platelet membrane proteins.