Hooshang Nikjoo's Group

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The objectives of the Radiation Biophysics Group's work is to characterize the biophysical features of radiation track that determines their effects on mammalian system, relate these to subcellular and cellular effects of radiations of different quality, and evaluate their practical implications for radiation protection and radiation therapy.

The Radiation Biophysics Group(RBG)was formed in 2008 at Karolinska Institutet based on the initiative of the SSM (The Swedish Radiation Safety Authority). Dr Nikjoo was appointed to head of the group, and as Professor of radiation biophysics in June 2009, at the Department of Oncology-Pathology.

The general strategy of the work is to exploit the power of theory and computation in biophysical modelling in conjunction with specific experiments to understand the mechanism(s) of radiation insult in mammalian cells and tissue. The mission of the group is:

  • To undertake Fundamental Research on the relationship in which human genome is damaged and repaired or modified from insult by ionizing radiation;
  • To develop a method and models to estimate the genetic risk of low dose radiation exposure of male and female humans - a problem that has persisted for the past 60 years;
  • To provide course text books, training courses for PhD students and career development in research within the field of radiation biophysics;
  • To promote an improved public understanding of scientific development in the field of radiation research and radiation protection.

The group has published original contributions in the following topics:

A. BIOPHYSICAL STUDIES OF RADIATION ACTION AND RADIATION QUALITY

  • Physical and biological aspects of low energy electrons
  • Physical and Biophysical aspects of Auger electrons
  • Radioprobing novel structures of DNA
  • Microdosimetry
  • Frequencies and magnitude of energy deposition by electrons and ions in DNA and larger macromolecular structures
  • RBE of low Energy Electrons and Photons

B. PHYSICS AND PARTICLE TRACK SIMULATION

Development of track structure models for electron in biological media and full-slowing-down of protons and heavier ions used in particle radiation therapies.

Database of Monte Carlo Track Structure Codes KURBUC at RBG

Kurbuc_e Uehara & Nikjoo e- 10eV - 10 MeV  
Pits99 Wilson & Nikjoo all ions e 0.3 MeV/u track segment
Kurbuc_p Uehara & Nikjoo protons 1keV  1MeV full slowing down
Kurbuc_alpha Uehara & Nikjoo a-particles 1keV/u  8MeV/u full slowing down
ChemKurb Uehara & Nikjoo chemistry e10-12 s  
kurbuc_n Nikjoo & Uehara neutrons thermal -100MeV  
Kurbuc_liq Uehara, Nikjoo, Emfietzoglou electron 10eV  10 keV  
Kurbuc_proton Liamsuwan, Uehara, Nikjoo protons 1keV/u  300MeV/u full slowing down
Kurbuc_carbon Liamsuwan & Nikjoo carbon ions 1keV/u  10MeV/u full slowing down

An example: Number of events in a 200 MeV full slowing down proton track

p elastic scattering 200,908
p ionization 1,943,795
p excitation 1,117,797
p e-capture 1,294
H elastic scattering 2,259
H ionization 1,084
H excitation 676
H electron loss 1,293
Secondary electrones    
ionization ( 12.62 eV) 12.62 eV 1,977,465
ionization ( 14.75 eV) 14.75 eV 1,494,653
ionization ( 18.51 eV) 18.51 eV 877,941
ionization ( 32.40 eV) 32.40 eV 20,812
ionization (539.7 eV) 539.7 eV 7,135
excitation A1B1 198,989
excitation B1A1 648,345
excitation Rydberg A+B 246,620
excitation Rydberg C+D 347,007
excitation diffuse band 1,204,030
excitation H* Lyman a 343,570
excitation H* Balmer a 67,931
excitation OH* 836,387
sub-excitation electrons ------- 634,450

C. DNA DAMAGE AND REPAIR

Development of mechanistic model of DNA damage and repair in mammalian cells.

D. DEVELOPMENT OF COMPUTATIONAL GENOMIC TECHNOLOGIES FOR DETECTION OF LCR AND CNV IN HUMAN GENOME
E. GENETIC RISK ESTIMATION FROM EXPOSURE TO RADIATION IN HUMAN

Group members

Hooshang Nikjoo, Professor, Group leader
Tommy Sundström, MSc, Research Assistant, 2008-2012
Peter Girard, PhD, Research Associate
Shirin Rahmanian, M.Sc, Visiting Research Student
Lennart Lindborg, PhD, Emiritus Professor, Research Associate
Dimitris Emfietzoglou, PhD, Medical Physics, Ioannina Medical School, Research Associate
K Sankaranarayanan, Emeritus professor, Leiden, Research Associate
Shuzo Uehara, Emeritus Professor, Kyushu University, Japan, Research Associate
Keith Baverstock, PhD, University of East Finland, Research Associate

Selected publications

Ionizing radiation and genetic risks. XVII. Formation mechanisms underlying naturally occurring DNA deletions in the human genome and their potential relevance for bridging the gap between induced DNA double-strand breaks and deletions in irradiated germ cells.
Sankaranarayanan K, Taleei R, Rahmanian S, Nikjoo H
Mutat. Res. ;753(2):114-30

Biochemical DSB-repair model for mammalian cells in G1 and early S phases of the cell cycle.
Taleei R, Nikjoo H
Mutat. Res. 2013 Aug;756(1-2):206-12

The non-homologous end-joining (NHEJ) mathematical model for the repair of double-strand breaks: II. Application to damage induced by ultrasoft X rays and low-energy electrons.
Taleei R, Girard P, Sankaranarayanan K, Nikjoo H
Radiat. Res. 2013 May;179(5):540-8

Nikjoo H, Uehara S, Emfietzoglou D, 2012, Interaction of radiation with matter. CRC Press, ISBN 9781439853573.

A Monte Carlo track structure simulation code for the full-slowing-down carbon projectiles of energies 1 keV u(-1)-10 MeV u(-1) in water.
Liamsuwan T, Nikjoo H
Phys Med Biol 2013 Feb;58(3):673-701

A model of the cell nucleus for DNA damage calculations.
Nikjoo H, Girard P
Int. J. Radiat. Biol. 2012 Jan;88(1-2):87-97

Simulation of (125)I-based radioprobing experiments to study DNA quadruplex structure and topology.
Girard P, Nikjoo H, Laughton C
Int. J. Radiat. Biol. 2008 Dec;84(12):1045-9

Ionising radiation and genetic risks. XVI. A genome-based framework for risk estimation in the light of recent advances in genome research.
Sankaranarayanan K, Nikjoo H
Int. J. Radiat. Biol. 2011 Feb;87(2):161-78

A complete dielectric response model for liquid water: a solution of the Bethe ridge problem.
Emfietzoglou D, Cucinotta F, Nikjoo H
Radiat. Res. 2005 Aug;164(2):202-11

Computational approach for determining the spectrum of DNA damage induced by ionizing radiation.
Nikjoo H, O'Neill P, Wilson W, Goodhead D
Radiat. Res. 2001 Nov;156(5 Pt 2):577-83

Radiation Biophysics