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Current Researches:

Phospholipid Membranes

Phospholipid membranes are essential functional and structural components of cells that are involved in numerous cellular physico-chemical processes occurring within the cells or between them. Despite the apparent importance of membrane electrostatic behavior for the functioning of membranes, insights into the electronic structure of the phospholipid membrane are scarce. These problems are difficult to address because of the complexity of the membrane system.Using density functional theory, our group investigated the structure of DPPC under different degrees of hydration with the focus on:

  1. Calculation of ground state configuration of DPPC, hydrated DPPC and 2xDPPC
  2. The influence of the interfacial water molecules on the electric potential at the interface
  3. The influence of neighboring DPPC molecules on the structure of the hydrated lipid
  4. Investigation of detailed distribution of charge density of membrane phospholipids and
  5. Determination of the magnitude, orientation and the origin of the dipole and quadrupole moments and dipole potential of the biological membrane.

(Up) Tilted gel-phase type structure of relaxed hydrated 2xDPPC with 32 water molecules per lipid. The tilt angle is about 28 degrees. (Below) Surface potential of the monolayer. The surface potential is defined as the sum of the Hartree potential plus the local pseudopotential.

Also our group were able to give 'complete assignments'  of the vibrational spectrum of DPPC. We found that water hydrating the lipid headgroups enables efficient energy transfer across membrane leaflets on sub-picosecond time scales. The emergence of spatially extended vibrational modes upon hydration, underlies this phenomenon. Our findings illustrate the importance of collective molecular behavior of biomembranes and reveal that hydrated lipid membranes can act as efficient media for the transfer of vibrational energy.

Vibrational dynamics of DPPC bilayer type structure. (a) is an extended mode of the bilayer at 36.22 1/cm (b) is a breathing mode at 74.24 1/cm in which the two lipids are in anti-phase. (c) is the phase velocity for vibrations Tx of the system as a function of frequency.