Effects of High Magnetic Fields on Transcription Reactions: The Magnetic Anisotropy of T7 RNA Polyme

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Effects of High Magnetic Fields on Transcription
ReactionsThe Magnetic Anisotropy of T7 RNA
PolymeraseKim WadeltonaMarianna Worczakc,
James Ch. Davisb, Mark W. MeiselbSummer 2005
NHMFL REU Participants, a Department of Physics,
Sweet Briar College, Sweet Briar, VA 24595, b
Department of Physics, University of Florida
Gainesville, FL 32611-3440, c 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 proteins 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
Hypothesis Strong magnetic fields generate
subtle perturbations of biomolecules due to the
structural diamagnetic anisotropy of the
molecules, causing a disruption of normal
biochemical function (Worczak 2005).
Alignment or Distortion of the molecules?
Model
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)
Transcription malfunction?
Transcription
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
FR, where k is a spring constant for the thumb
and s is the displacement from equilibrium. With
enough applied force, the thumb moves, deforming
the entry pore and interfering with transcription.
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5/stryer/ch28/Slide9.jpg
Transcription is the creation of RNA transcripts
from a DNA template. It is the first step in
gene expression. The DNA enters the polymerase
through 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-DNA hybrid (Tahirov et
al. 2002).
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Results
At 9 Tesla, the maximum energy, DU, arising from
the magnetic anisotropy, DX (Pauling 1979), and
strong field, B (Worchester 1978), is 10 to 100
ppm of the ambient thermal energy.
T7 RNA Polymerase
The T7 RNA Polymerase is composed of groups and
subgroups, each with their own roles in
transcription. We use a hand model, where the
thumb, palm, and fingers represent the major
sections.
Calculating FM from the magnetic anisotropy
energy and the displacement from equilibrium,
FM10-17 N. Considering the forces required to
unzip a beta hairpin, to stop the polymerase from
proceeding along the DNA, or to overstretch DNA
are all on the order of 10-11 N, our FM is
small. But our effect, movement of 1 nm, should
come from a small force.
The thumb has one main alpha helix of 40 base
pairs. Its role is to guide the DNA into the
groove where transcription takes place, and to
wrap around the DNA during transcription to hold
the DNA secure (Tahirov et al. 2002).
We also propose a possible range of spring
constants for the thumb, based upon possible
values for restoring force, FR, and energy, U.
References
The thumb is located at the DNA entry pore and
any alteration to the thumbs position is likely
to inhibit transcription.
Paul , A.-L, R.J. Ferl, B. Klingenberg, J.S.
Brooks, A.N. Morgan,J. Yowtak, and M.W. Meisel
(2005) Strong Magnetic Field Induced Changes of
Gene Expression in Arabidopsis. Materials
Processing in Magnetic Fields Proceedings of
the International Workshop on Materials Analysis
and Processes in Magnetic Fields (NHMFL,
Tallahassee, 17-19 March 2004). To appear fall
2005. Pauling, Linus (1979) Diamagnetic
anisotropy of the peptide group. Biophysics (76)
2293-2294.
Worchester, D. L. (1978) Structural Origins of
Diamagnetic Anisotropy. Proc. Natl. Acad. Sci.
(75) 5475-5477. Worczak, Marianna et al. (2005)
Effects of high magnetic fields on in vitro
transcription Report of research performed Summer
2005 as part of NHMFL REU Program.
Acknowledgements This work was made possible, in
part, by the National High Magnetic Field
Laboratory (NHMFL) Summer 2005 Program, and the
University of Florida. We acknowledge R. J.
Ferl, W. B. Gurley, and Norman Anderson for their
enlightening conversations. Additional support
was provided by grants from the National Science
Foundation (NSFDMR-0305371) and NASA (NNA045561).
Tahirov, Tahir H et al. (2002) Structure of a T7
RNA polymerase elongation complex at 2.9 A
resolution. Nature (420) 43-50. Worchester, D.L.
(1978) Structural Origins of diamagnetic
anisotropy. Pro.Natl. Acad. Sci. (75) 5475-5477.
Structure found in protein data base PDB 1QLN
(Tahirov et al. 2002).