Professor Benjamin Ehrenberg

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• Professor Benjamin Ehrenberg
• Biophysics of membranes Photosensitization and
  light-triggered processes Optical
  spectroscopy
• tel [phone] fax [phone] e-mail
  ehren_at_mail.biu.ac.il
• http//www.ph.biu.ac.il/fac?id16
• Biography
• B.Sc. and M.Sc., Bar-Ilan University Soreq
  Nuclear Center, Physical Chemistry
• Ph.D., Chemical Physics, Weizmann Institute of
  Science
• Postdoctoral research, Cornell University,
  Ithaca, NY (with Prof. A Lewis 1977-9)
• Sabbaticals at University of Connecticut Health
  Center (1985,6,8) UCLA (1993)
• Full Professor, Bar-Ilan University, since 1993
• Chairman, Department of Physics, 1994-7
• Chairman, BIU M.Sc. (1994-1999) Ph.D. (since
  2003) graduate schools
• Research Overview
• Photosensitization reactions in nano-scale
  liposomes as models of biological cells
  light-triggered damage caused in membranes, with
  sub-nanometer resolution electric potential
  differences over nanometer scales, across and
  near membranes employing optical sensors to
  probe the concentration profile of oxygen in
  membranes.

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LIPOSOMES
Natural and artificial lipid bilayer membranes
are 2-dimensional semi-fluid phases, with a
thickness of 4 nm, which spans 2 lipid molecules
4 nm
There are several components of the electric
field across near membranes, on the 4-30 nm
scale. The fields are the driving forces of
cellular processes in all cells. They are the
transmitted signal in nerve cells. They can be
measured by the smallest available electrodes
molecules that sense the field optically.
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Light-activated molecules that enter the membrane
can be sensitized by light to generate active
oxygen species. These cause localized damage to
membrane components and are used for Photodynamic
Therapy of tumors
We have several custom-modified sensitizers that
can be anchored, with sub-nm resolution in the
membrane. The relative efficiency of a
membrane-localized reaction is increased (see
numbers). This could be used to enhance
photodynamic therapy.
0.54
1.0
1.22
1.33
4 nm
Lipid membrane
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Diffusion of oxygen inside a membrane, and out of
it
Extra-liposomal (or extra-cellular) aqueous phase
4 nm
sensitizer
The nanometric resolution in the location of
sensitizers is employed to study the location of
the photochemical effect that is inflicted.
Diffusion path of oxygen inside the lipid membrane
A reactive singlet oxygen molecule that is
generated in the membrane diffuses rapidly (100
nm in 1 millisecond). The deeper the sensitizer
is located, the longer the diffusion path and the
higher its efficiency in photodynamic therapy.
We are studying depth-localized sensors of oxygen
to probe its concentration profile inside the
membrane phase.