All the transportation of substances, information, and energy inside and outside the cell that is necessary for vital activities is carried out through the cell membrane. These transportations are deeply involved in neurotransmission, metabolism, and viral infections, making them important research targets in the biology, medicine, and drug-discovery fields. The basic structure of the cell membrane is a lipid bilayer, in which specific lipids and membrane proteins are assembled through diffusion and aggregation of molecules within the membrane to control and improve the efficiency of reactions occurring in the cell membrane. Such regions are called lipid domains, a typical example of which is "lipid raft", which is rich in sphingolipids and cholesterol. New technologies for controlling and arranging the positions of lipid domains on a solid substrate are demanded for the biosensing and screening of lipids and membrane proteins.

This research team fabricated an artificial lipid bilayer on a graphene oxide monolayer deposited on a silicon substrate. They discovered for the first time that the lipid domains are concentrated on graphene oxide. Graphene oxide has a structure in which hydrophilic oxygen functional groups are added to graphene (a monoatomic sheet material of carbon).

In a two-component lipid bilayer consisting of two types of phosphatidylcholines with different fluidities, the majority of the low-fluidity gel phase domains in the lipid bilayer membrane gathered on the graphene oxide. In a three-component mixed lipid bilayer membrane of sphingolipids, cholesterols, and phosphatidylcholine, many lipid raft components were present on the graphene oxide．

Professor Ryugo Tero, the leader of the research team, explained as follows: "Regardless of the lipid composition, the less fluid lipid domains clustered on the graphene oxide. This is due to the presence of a mixture of hydrophilic and hydrophobic regions on the graphene oxide surface on a nanometer scale. The initial process of the domain formation in the lipid bilayer occurred preferentially in the hydrophobic regions of the graphene oxide."

By controlling the position of lipid domains on a solid substrate, membrane proteins with high affinity to the lipids can be placed in the same location, which is expected to be useful as an elemental technology for biosensors and screening technologies targeting membrane proteins. Furthermore, the research team believes that the same method can be used to collect biochemically important lipid components such as glycolipids as well as the lipid raft. They expect that this will be useful in the development of techniques for concentrating and purifying the rare lipids and membrane proteins in cell membranes.