Effects of High Magnetic Fields on Transcription Reactions:
The Magnetic Anisotropy of T7 RNA Polymerase
Marianna Worczak*c, James Ch. Davisb, Mark W. Meiselb
*Summer 2005 NHMFL REU Participants,
Department of Physics, Sweet Briar College, Sweet Briar, VA 24595,
Department of Physics, University of Florida Gainesville, FL 32611-3440,
Department of Chemistry, Clarkson University, Potsdam, NY 13699-2389
Abstract: The diamagnetic properties of the T7 RNA polymerase have been investigated to test the hypothesis that strong magnetic fields generate subtle
perturbations of the polymerase due to the structural diamagnetic anisotropy of the molecule. These possible effects may be the cause of a biochemical stress
response previously detected in plants. The maximum energy arising from the protein’s orientation in a strong magnetic field was estimated. At 9 Tesla, this
magnetic energy is approximately 10-100 ppm of the ambient thermal energy. A one-dimensional model was proposed of the deformation of the thumb alpha
helix of the polymerase. Distortion forces estimated were ~4 orders of magnitude smaller than those forces required to stop transcription completely.
Motivation Alignment Hypothesis: Strong magnetic fields generate subtle
or perturbations of biomolecules due to the structural diamagnetic
Distortion of the anisotropy of the molecules, causing a disruption of normal
molecules? biochemical function (Worczak 2005).
Control 18.9 T
Arabidopsis thalia displayed a stress response (in blue) when
placed in a magnetic field of 18.9 Tesla (Paul et al. 2005)
The thumb, palm, and fingers form the DNA entry
pore. In a homogenous field, a force (FM) is
applied. The thumb reacts with a restoring force
http://oregonstate.edu/instruction/bb451/winter2005/stryer/ch28/Slide9.jpg FR, where k is a spring constant for the thumb and s
is the displacement from equilibrium. With enough
Transcription is the creation of RNA transcripts from a DNA template. It is applied force, the thumb moves, deforming the
the first step in gene expression. The DNA enters the polymerase through entry pore and interfering with transcription.
the DNA entry pore, proceeds through a groove within the polymerase,
where it creates an RNA transcript. The RNA is formed at the active site
inside the groove, where the DNA and RNA temporarily form an RNA- Results
DNA hybrid (Tahirov et al. 2002).
At 9 Tesla, the maximum energy, DU, arising
from the magnetic anisotropy, DX (Pauling
T7 RNA Polymerase 1979), and strong field, B (Worchester 1978), is
10 to 100 ppm of the ambient thermal energy.
The T7 RNA Polymerase is composed of groups and subgroups, each with Calculating FM from the magnetic anisotropy energy
their own roles in transcription. We use a hand model, where the thumb, and the displacement from equilibrium, FM~10-17 N.
palm, and fingers represent the major sections. Considering the forces required to unzip a beta hairpin,
to stop the polymerase from proceeding along the DNA,
The thumb has one main alpha helix or to overstretch DNA are all on the order of ~10-11 N,
of ~40 base pairs. Its role is to our FM is small. But our effect, movement of 1 nm,
guide the DNA into the groove should come from a small force.
where transcription takes place, and
to wrap around the DNA during We also propose a possible range of spring
transcription to hold the DNA constants for the thumb, based upon possible
secure (Tahirov et al. 2002). values for restoring force, FR, and energy, U.
The thumb is located at the DNA Paul , A.-L, R.J. Ferl, B. Klingenberg, J.S. Brooks, A.N. Morgan, Worchester, D. L. (1978) Structural Origins of Diamagnetic Anisotropy.
J. Yowtak, and M.W. Meisel (2005) Strong Magnetic Field
entry pore and any alteration to the Induced Changes of Gene Expression in Arabidopsis. Materials
Proc. Natl. Acad. Sci. (75) 5475-5477.
Worczak, Marianna et al. (2005) Effects of high magnetic fields on in vitro
thumb’s position is likely to inhibit Processing in Magnetic Fields: Proceedings of the International transcription Report of research performed Summer 2005 as part of
Workshop on Materials Analysis and Processes in Magnetic Fields NHMFL REU Program.
transcription. (NHMFL, Tallahassee, 17-19 March 2004). To appear fall 2005.
Pauling, Linus (1979) Diamagnetic anisotropy of the peptide group. Acknowledgements:
Biophysics (76) 2293-2294. This work was made possible, in part, by the National High Magnetic
Field Laboratory (NHMFL) Summer 2005 Program, and the
Tahirov, Tahir H et al. (2002) Structure of a T7 RNA polymerase
University of Florida. We acknowledge R. J. Ferl, W. B. Gurley, and
elongation complex at 2.9 A resolution. Nature (420) 43-50.
Structure found in protein data base PDB# 1QLN (Tahirov et al. 2002). Norman Anderson for their enlightening conversations. Additional
Worchester, D.L. (1978) Structural Origins of diamagnetic
support was provided by grants from the National Science Foundation
anisotropy. Pro.Natl. Acad. Sci. (75) 5475-5477.
(NSFDMR-0305371) and NASA (NNA045561).