B - Department of Physics

Mesoscale Science:
Selected perspectives of (some) past, present, and future
issues at the crossroads of physics, chemistry,
molecular biology, and You!
(The CCMS Summer Lecture Series - 2012)
Lecture 6: Form follows Function (vice versa?) –
bis 2 [continuation of Lectures 3 and 5]
Mark W. Meisel
Department of Physics and NHMFL, UF
(http://www.phys.ufl.edu/~meisel/CCMS-SLS-2012.docx)
Supported by the National Science Foundation via DMR-1202033 (MWM)
and DMR-0654118 (NHMFL), and UF CCMS.
Where have we been and Where are we going?
Last Week
Lecture 3: Form follows Function (vice versa?) [Amplitude and Phase in Experiments]
Lecture 4: BEC vs. “eyeless” gene, “Smallest transistor, meandering means, and lysozyme”
This Week
Lecture 5: Form follows Function (vice versa?) – bis
Lecture 6: Form follows Function (vice versa?) – bis – bis
Skip a Week
“The End” Week
Lecture 7: Quantum Spins: Chains, Planes, and Wheels (Magnetic Mesoscale)
Lecture 8: TBA
BREAKING FLASH (Sweet!):
“Tiny Talk” script for “homework” has been received!
http://cnem.chem.ufl.edu/outreach.html
http://www.chem.ufl.edu/~bowers/
Tiny Tech (DRAFT by Ryan Wood, UF Chem, Bowers’ Group)
Our daily lives are affected by forces, like friction or weight. Similarly,
microscopic cells are subjected to forces acting on them. Scientists are finding out that
those forces are tremendously important to the form and function of cells. How?
One method uses an instrument known as optical tweezers to shine light on
those forces. Literally! A highly focused laser beam has a large electric field gradient
at its narrowest point, the beam waist. Due to the electric field gradient, molecules
that are within the beam waist are subjected to a force, which can be used to move
molecules. Using two laser beams, molecules at opposite ends of a cell can be pulled
apart, creating a tiny force that deforms the cell. How tiny? These forces can be as
small as several trillionths of a pound.
Like a rubber band, cells experience a restoring force when they are
deformed, they relax to their original shape. Monitoring the relaxation of deformed
cells imparts important information about the elastic properties of the cell. These
experiments truly stretch the limits of cell science.
Potential Script for “Tiny Tech Radio Series”
Outline for Today Lecture 6 (Form follows Function – bis – bis )
A.
B.
C.
D.
E.
Clarification on NMR T1, T2, FID, Question from last time
High Magnetic Fields and You?
Pulling on Proteins
The Challenge to You! (and the “homework”)
What’s to come in the near-future lectures
Nuclear Spin Evolution
z
z
z
Mo
y
x
y
y
x
Mo
ω
x
x
RF receivers pick up
the signals
Time
I
y
www.nmr2.buffalo.edu/.../Introduction-1D-2D-NMR-KDBishop.ppt
Free Induction Decay
The signals decay away due to interactions with the surroundings.
A free induction decay, FID, is the result.
Fourier transformation, FT, of this time domain signal
produces a frequency domain signal.
FT
Frequency
Time
www.nmr2.buffalo.edu/.../Introduction-1D-2D-NMR-KDBishop.ppt
Proteins in liquid,
T1 ∼ 1 – 4 s
T2 ∼ 10 – 100 ms
http://www.biozentrum.unibas.ch/personal/grzesiek/TEACHING/MATERIAL/2011/14370-01/nano_nmr2011.pdf
Outline for Today Lecture 6 (Form follows Function – bis – bis )
A.
B.
C.
D.
E.
Clarification on NMR T1, T2, FID, Question from last time
High Magnetic Fields and You?
Pulling on Proteins
The Challenge to You! (and the “homework”)
What’s to come in the near-future lectures
What are the LIMITS? … at high magnetic fields?
in vivo imaging of gene regulation?
At what magnetic field strength would YOU become
900 MHz
concerned about having MRI performed? Duration? 105 mm bore
http://thewritersguidetoepublishing.com/
forward-to-the-future-tomorrow-always-comes/no-limits-283x300
http://nmr.magnet.fsu.edu/facilities/900_105mm_TLH.htm
Effects of High Magnetic Fields on in vitro
Transcription of T7 and SP6 RNA Polymerases*
Marianna Worczak†, Kimberly Wadelton†,
James Ch. Davis, and Mark W. Meisel
Department of Physics and NHMFL, University of Florida
Anna-Lisa Paul and Robert J. Ferl
Department of Horticultural Sciences, University of Florida
Motivation via work on whole plants
The “Working” Hypothesis
Transcription and T7 Structure
Results with T7 and SP6
Future Directions
* Supported, in part, by the NSF via the NHMFL, DMR-0305371 (MWM),
and NASA grant NNA04CC61 (ALP and RJF).
† NHMFL Research for Undergraduates (REU) Summer 2005.
Magnetic Levitation: The Basics
(Not of the Superconducting or Similar Variety)
Diamagnetism: M. Faraday (1846)
Magnetic Levitation of:
Graphite: W. Braunbeck (1939)
Organic Materials: E. Beaugnon and R. Tournier (1991)
F=(M•∇)B
F ≡ force acting on the body
B ≡ external magnetic field
ρ ≡ density of the material
M ≡ magnetic moment
M = (χ/µo) (Volume) B
χ ≡ magnetic susceptibility
µo ≡ permeability constant
Force due to gravity: (mass) g = ρ (Volume) g
* Balances the magnetic force when material is
diamagnetic ( i.e. χ < 0 ); and
Bz ∇z Bz = µoχρ g
(assuming ideal conditions along the z-direction of solenoid magnet)
H2O levitates at [B dB/dz] ≈ 1400 T2/m
Graphite levitates at [B dB/dz] ≈ 375 T2/m
> Mesoscale Science
< Megascale Science
“a range of infrastructure
needed to explore
strange new Worlds”
Sketch of Cell 5 Magnet at the National High Magnetic Field Laboratory (NHMFL) in
Tallahassee. Dimensions are in mm and vertical bore access is 50 mm.
0.5
0.0
-0.5
-1.0
-1.5
-2.0
200
D is t
100
anc e
f ro m
C en
0
-100
-200
ter o
f Ma
g net
(m m
)
0
5
10
15
20
)
d ( Te s l a
l
ie
F
ic
t
M ag ne
Force
(units
g)
(units of
of g)
Initial Data: Magnetic Levitation and Controls
|
← ∼ 50 mm →
|
Results after staining of intact plants experiencing
2.3 hours of the parameters given:
Bench Control
B ≤ 0.1 mT
B∇ B = 0
Center Field Control
B = 18.9 T
B∇ B = 0
Magnetic Levitation
B = 14.4 T
B∇ B = 1708 T2/m
Adh-GUS Reporter Gene System
Anoxia
Hypoxia
ABA
Cold
Drought
Salt
Adh gene promoter
β-Glucuronidase - GUS
GUS coding region
Quantification and Localization
(at the level of gene expression!)
Additional Measurements: The Plants and the Qualitative Results
GUS Activity [(nmol 4-MUG)/(µg protein)/minute]
The Quantitative Results
a
20
10
Leaves (2.5 hr exposure)
Run 1 - NHMFL Cell 5
Run 2 - NHMFL Cell 6
Run 3 - UF Supercon.
Run 4 - NHMFL Cell 5
Log-normal Function
95% Limits
P = 0.001
and not
∝B
∝ B2
0
b
40
Roots (2.5 hr exposure)
Run 1 - NHMFL Cell 5
Run 2 - NHMFL Cell 6
Run 3 - UF Supercon.
Run 4 - NHMFL Cell 5
P = 0.03
20
0
0
5
10
15
20
Magnetic Field (Tesla)
25
Microchip Array Data: More Information!
Affymetrix ATH1 Arabidopsis Array
for 21 day old plants 21 T or 0 T
bore control for 2.5 hours.
Topographical imaging technique
for qualitative analysis of
microarray data
J.Ch. Davis, A.-L. Paul, R.J. Ferl,
M.W. Meisel
BioTechniques 41 (2006) 554
70
Athb12
Xero2
Xtr7
Cor
60
50
40
30
20
10
0
-10
2.5 hrs Shoot
2.5 hrs Shoot
2.5 hrs Shoot
Mag Control
Mag 14T
Mag 21T
-20
Quantitative Real-Time PCR analyses of selected genes.
The levels of gene expression for these genes are
displayed as fold-induction or fold-repression relative to
the control.
The “Working” Hypothesis: Magnetic Alignment vs. Magnetophoresis
The magnetic energy (Bothner-By, 1996; Tjandra et al., 1997):
1
E=−
B(r ) ⋅ χ ⋅ B (r )
2 µ0
Variations from anisotropies of χ and B:
1
{ B(r ) ⋅ δχ ⋅ B(r ) + 2 B(r ) ⋅ ∆χ ⋅ δB(r )}
δE = −
2 µ0
An order of magnitude comparison of the two effects:
2 ∆χ δB
R ≈
δχ B
Top of leaves and Bottom of roots:
Anisotropy of χ for biomacromolecules:
(Maret, Dransfeld, 1985; Tjandra et al., 1997)
(Valles et al., 1997)
(δB/B) ≈ 5 × 10−3
δχ ≈ 10−33 m3/molecule
∆χ ≈ 10−29 m3/molecule
R < 10 −2 ⇒ Magnetic Alignment > Magnetophoresis !
Adh-GFP
The Next Generation of reporter gene
Anoxia
Hypoxia
ABA
Cold
Drought
Salt
Adh gene promoter
•Quantification
•Localization
Green Fluorescent Protein
GFP coding region
•Non-destructive
•Remote Sensing
Mike Manak -UF
Adh-GFP
488 nm / 512 nm
Positive CaMV/GUS
Control for comparison
Facts:
(a) Adh unchanged.
(b) Response not
shifted to lower B.
Adh/GFP expression
Control
Adh/GFP expression
21T 2.5 hours
Null Result for Adh-GFP at 20 T for 6.5 hrs?
Explanation:
GFP sensitivity too
weak !
Summary
Static, “homogeneous” magnetic fields above 15 T* induce a
stress response mechanism in the gene regulation in transgenic
arabidopsis.
GUS Activity [(nmol 4-MUG)/(µg protein)/minute]
* Noteworthy that this value is about the “crossover” field for
taking magnetic alignment into account for NMR structural
determinations.
a
20
10
Future
Leaves (2.5 hr exposure)
Run 1 - NHMFL Cell 5
Run 2 - NHMFL Cell 6
Run 3 - UF Supercon.
Run 4 - NHMFL Cell 5
Log-normal Function
95% Limits
Single transcription in vitro studies?
(e.g. T7 RNA polymerase)
0
b
40
Roots (2.5 hr exposure)
Run 1 - NHMFL Cell 5
Run 2 - NHMFL Cell 6
Run 3 - UF Supercon.
Run 4 - NHMFL Cell 5
20
0
0
5
10
15
20
Magnetic Field (Tesla)
25
High magnetic field induced changes of gene
expression in arabidopsis;
A.-L. Paul, R.J. Ferl, M.W. Meisel;
BioMagnetic Research & Technology 4 (2006) 7
Implications?
The effect of homogeneous magnetic fields up to 25 T should be
investigated and understood; especially if:
New generation “2 GHz” NMR machines are needed to study gene
regulation in vivo (National Resonance Collaboratorium, 1998).
Road to this goal:
Y.-Y. Lin et al., “High-resolution, >1 GHz NMR in unstable magnetic
fields”, Phys. Rev. Lett. 85 (2000) 3732-3735. (25 T)
A.Y. Louie et al., “In vivo visualization of gene expression using magnetic
resonance imaging”, Nat. Biotechnol. 18 (2000) 321-325. (11.7 T)
R. Weissleder et al., “In vivo magnetic resonance imaging of transgene
expression”, Nat. Med. 6 (2000) 351-354. (1.5 & 7.1 T)
A. Kangarlu et al., “Cognitive, cardiac, and physiological safety studies in
ultra high field magnetic resonance”, Magn. Reson. Imag. 17 (1999) 14071416. (humans, 1 hour, 8 T)
“Simplicity does not precede complexity,
but follows it.” Alan J. Perlis
(EPIGRAMS IN PROGRAMMING)
Move from “complex” in vivo plants
to a simple in vitro system!
http://www.facebook.com/pages
/Alan-J-Perlis/70755357048
Try in vitro transcription of a single process:
Use T7 Ribomax® Express in vitro Transcription Kit (
).
Key elements:
1. T7 RNA polymerase (RNAP) widely studied (structure too).
2. Elements of kit are simple and pure (T7 RNAP,
DNA template, rNTPs, and buffer).
3. Protocol simple, and commercial kits available.
http://oregonstate.edu/instruction/bb451/winter2005/stryer/ch28/Slide9.jpg
Transcription
“Fingers”
“Palm”
“Thumb”
“N-Terminal
Domain”
D. Jeruzalmi and T.A. Steitz, EMBO J. 17 (1998) 4101 [PDB 1ARO].
T 7 RNAP
1QLN: Cheetham and Steitz, Science 286 (1999) 2305.
Model: Theis, Gong, and Martin, Biochemistry 43 (2004) 12709.
Recent: “The Structure of a Transcribing T7 RNA Polymerase in Transition
from Initiation to Elongation”, K.J. Durniak, S. Bailey, T.A. Steitz,
Science 322 (2008) 553 (including more dynamics of the conformational changes)
Results: T7 Reactions
T7 Electrophoresis Results
Controls | 4.5 Tesla |
9.0 Tesla
2.3 kb
1.1 kb
Time (min): 1
5 10 20 | 1
5 10 20 | 1
5
10 20
Control
I(t) / I(t = 1 min)
20
15
10
4.5 Tesla
9.0 Tesla
5
0
0
5
10
15
20
Time (minutes)
25
30
20 – 25 Tesla:
“null result”?
Results: SP6 Reactions
SP6 Electrophoresis Results
Controls
| 4.5 Tesla | 9.0 Tesla
1.8 kb
Time (min): 1
5 10 20 | 1 5 10 20 | 1 5 10 20
Surprise again: 9 T strong enough to perturb transcription!?
SP6 RNA polymerase structure: not yet determined
(but believed to be similar to T7 RNA polymerase).
SP6: 874 residues
T7: 883 residues
Effects of High Magnetic Fields on in vitro
Transcription of T7 and SP6 RNA Polymerases
Marianna Worczak†, Kimberly Wadelton†,
James Ch. Davis, and Mark W. Meisel
Department of Physics and NHMFL, University of Florida
Anna-Lisa Paul and Robert J. Ferl
Department of Horticultural Sciences, University of Florida
Future Extensions/Work:
T7/SP6: additional data at more/higher magnetic fields & longer time!
(magnetic field power law?)
Magnetic Anisotropy from Structure (Worcester, 1978; Pauling, 1979):
calculate/measure/predict differences (via RNCs) ???
(RDC = residual dipolar couplings)
Simple to Complex: E. coli (living system amplifier!) and “noise” ?
“RADICAL PAIR”, photoexcitation of cryptochromes up to 500 µT ?
I.A. Solov'yov, D.E. Chandler, K. Schulten, “Magnetic Field Effects in
Arabidopsis thaliana Cryptochrome-1”, Biophys. J. 2007 92:2711
M. Ahmad, P. Galland, T. Ritz, R. Wiltschko, W. Wiltschko, “Magnetic intensity
affects cryptochrome-dependent responses in Arabidopsis thaliana”
Planta 2006 225:615
Change the setting on your clock, Meisel!?
4774–4779 | PNAS | March 27, 2012 | vol. 109 | no. 13
www.pnas.org/cgi/doi/10.1073/pnas.1118959109
Outline for Today Lecture 6 (Form follows Function – bis – bis )
A.
B.
C.
D.
E.
Clarification on NMR T1, T2, FID, Question from last time
High Magnetic Fields and You?
Pulling on Proteins
The Challenge to You! (and the “homework”)
What’s to come in the near-future lectures
The Bacterial Condensin MukBEF Compacts DNA
into a Repetitive, Stable Structure
Ryan B. Case,
1,2*
3*
Yun-Pei Chang,
1,3
Nicholas R. Cozzarelli,
2,4
Steven B. Smith,
Jeff Gore,
1,2,3,4
Carlos Bustamante
Science 9 July 2004: Vol. 305. no. 5681, pp. 222 - 227
1
Dept. of Molecular and Cell Biology, University of California, Berkeley
2
Dept. Physics, University of California, Berkeley
3
Biophysics Graduate Group, University of California, Berkeley
4
Howard Hughes Medical Institute, University of California, Berkeley
*
2
These authors contributed equally to this work.
(presentation by Mark Meisel, Physics, 18 Jan 06)
Fig. 1. (A) A single force-extension curve of naked DNA (left panel) and
DNA after incubation with 12.5 nM MukBEF and 2 mM Mg-ATP (right panel)
R. B. Case et al., Science 305, 222 -227 (2004)
Published by AAAS
Figure 1D
R. B. Case et al., Science 305, 222 -227 (2004)
Flow of superfluid 4He through a micro-orfice at 10 mK
O. Avenel and E. Varoquaux, Phys. Rev. Lett. 55 (1985) 2704
E. Varoquaux, M.W. Meisel, and O. Avenel, Phys. Rev. Lett. 57 (1986) 2291
Superfluid helium quantum interference devices: physics and applications
Y. Sato and R.E. Packard, Rep. Prog. Phys. 75 (2012) 016401
http://iopscience.iop.org/0034-4885/75/1/016401/pdf/0034-4885_75_1_016401.pdf
Fig. 2. (A) Recondensation against a constant force
R. B. Case et al., Science 305, 222 -227 (2004)
Published by AAAS
Fig. 3. Enhancement of recondensation by a type I topoisomerase
R. B. Case et al., Science 305, 222 -227 (2004)
Published by AAAS
Fig. 4. Model for the DNA condensation mechanism
R. B. Case et al., Science 305, 222 -227 (2004)
Published by AAAS
Optical tweezers slide
http://www.stanford.edu/group/blocklab/Optical%20Tweezers%20Introduction.htm
Perspectives MOLECULAR BIOLOGY: Science 9 July 2004: Vol. 305. no. 5681, pp. 188 - 190
“Unraveling DNA Condensation with Optical Tweezers”, Xiaowei Zhuang
The Bacterial Condensin MukBEF Compacts DNA
into a Repetitive, Stable Structure
Jargon Slide:
Bacterial: E. coli
Condensin: proteins that play a role in compacting DNA
MukBEF:
MukB is a SMC dimer.
MukE and MukF are two non-SMC subunits that are believed
to bind to the head domains of
MukB (“rectangles in the cartoons”).
SMC: Structural Maintenance of Chromosomes
Figure S1
R. B. Case et al., Science 305, 222 -227 (2004)
Published by AAAS
Figure S3
Worm-like Chain Model
1/ 2
 4P 

= 
F  kB T 

x 
1 −

 L(F) 
(y= b +
mx)
1
L(F) = Lo ( 1 + F / S )
P = persistence length (~ 50
nm)
X = distance tip to tail
L = length of strand (~ 5 µm)
S = stretch modulus (1200 pN)
R. B. Case et al., Science 305, 222 -227 (2004)
Published by AAAS
Figure S4
R. B. Case et al., Science 305, 222 -227 (2004)
Published by AAAS
Figure S5
R. B. Case et al., Science 305, 222 -227 (2004)
Published by AAAS
Never before in the history of science
has “anything” like this been seen…
Figure 1 of Biophys J, March 2002, p. 1537-1553, Vol. 82, No. 3
“Unzipping DNA with Optical Tweezers: High Sequence Sensitivity and Force Flips”
U. Bockelmann, Ph. Thomen, B. Essevaz-Roulet, V. Viasnoff, and F. Heslot
Figure 10 of Biophys J, March 2002, p. 1537-1553, Vol. 82, No. 3
“Unzipping DNA with Optical Tweezers: High Sequence Sensitivity and Force Flips”
U. Bockelmann, Ph. Thomen, B. Essevaz-Roulet, V. Viasnoff, and F. Heslot
Figure 11 of Biophys J, March 2002, p. 1537-1553, Vol. 82, No. 3
“Unzipping DNA with Optical Tweezers: High Sequence Sensitivity and Force Flips”
U. Bockelmann, Ph. Thomen, B. Essevaz-Roulet, V. Viasnoff, and F. Heslot
S.B. Smith, Y. Cui, C. Bustamante
Science (1996) vol. 271, pp. 795-799
“Theory”
0 nm/s limit
Molecule 1
100 nm/s
Molecule 2
50 nm/s
Molecule 2
200 nm/s
Figure 15 of Biophys J, March 2002, p. 1537-1553, Vol. 82, No. 3
“Unzipping DNA with Optical Tweezers: High Sequence Sensitivity and Force Flips”
U. Bockelmann, Ph. Thomen, B. Essevaz-Roulet, V. Viasnoff, and F. Heslot
Yun-Pei Chang,
1,3
Steven B. Smith,
2
Jeff Gore,
1,2,3,4
Carlos Bustamante
20
0
Nicholas R. Cozzarelli,
2,4
14
3*
5)
Ryan B. Case,
1,2*
09
RE
TR
AC
TE
D
The Bacterial Condensin MukBEF Compacts DNA
into a Repetitive, Stable Structure
1
M
ar
ch
Science 9 July 2004: Vol. 305. no. 5681, pp. 222 - 227
*
Sc
ie
nc
e
30
7
(0
4
Dept. of Molecular and Cell Biology, University of California, Berkeley
2
Dept. Physics, University of California, Berkeley
3
Biophysics Graduate Group, University of California, Berkeley
4
Howard Hughes Medical Institute, University of California, Berkeley
These authors contributed equally to this work.
Not mentioned on the Bustamante Group site.
Case had a webpage and photo posted before the holiday, but not now.
Science 4 March 2005: Vol. 307. no. 5714, p. 1409
… However, subsequent experiments done after the paper
appeared suggested that the sawtooth pattern corresponds to
the unzipping of the two strands of DNA (2). We now believe
that nicks that arose indiscriminately along the DNA molecules
from normal pipetting allowed interior biotin and Digoxigenin
derivitization of the DNA tether. The combination of interior
and terminal labels most likely generated a pulling geometry
between the beads that led to the denaturation of the DNA.
To test these ideas, we have now performed an extensive set
of experiments.
(2) Bockelmann et al., Biophysical Journal (2002)
Why was the work of Bockelmann et al. missed?
It should have been discussed in the paper!?
Authors, Referees, and “Expert” blurb writer
missed this issue, but some reader(s) did not!
On Being A Scientist: Responsible Conduct in Research
(from the National Academy of Sciences)
(http://www.nap.edu/readingroom/books/obas/contents/allocation.html)
The Allocation of Credit
…
Citations serve many purposes
in a scientific paper. …
Failure to cite the work of others
can give rise to more than just hard
feelings. …
…
Some people succeed in science despite
their reputations. Many more succeed
at least in part because of their
reputations.
“Tutorial Wednesdays” and “Brain Speculation Fridays”
http://www.phys.ufl.edu/~meisel/CCMS-SLS-2012.docx
Skip a Week (in Greece)
Wednesday, 20 June = Lecture 7:
Quantum Spins: Chains, Ladders, Planes, and Wheels
(Magnetic Mesoscale) Ferromagnetism, Antiferromagnetism, and
Spin Glass-like behavior at Mesoscales of length/time and spatial/spin
dimensions, PLUS what a “bad” magnetometer signal might look like?
Friday, 22 June, Lecture 8 (last one) and end of Summer A:
Quantum Spins - bis, J.D. van der Waals, Summary of Lectures
“things I wished I knew before I knew them (Mesoscale)”
Exponetial fits, et al., negative temperature
The Plan: Wednesdays and Fridays, 4:05 pm to 5:00 pm
(but not for one week of 13 and 15 June)
“Tutorial Wednesdays” and “Brain Speculation Fridays”
(cold beverages available on Fridays for the after session)
The Detailed Plan and Notes:
(http://www.phys.ufl.edu/~meisel/CCMS-SLS-2012.docx)
Comparison of DNA and RNA
GUS Activity
[(nmol 4-MUG)/(µg protein)/minute]
GUS: P = 0.001 (not B or B2)
a
20
10
Microarray (8k genes)
Leaves (2.5 hr exposure)
Run 1 - NHMFL Cell 5
Run 2 - NHMFL Cell 6
Run 3 - UF Supercon.
Run 4 - NHMFL Cell 5
Log-normal Function
95% Limits
0
0
5
10
15
20
25
Magnetic Field (Tesla)
Real-Time Quantitative PCR
70
Athb12
Xero2
Xtr7
Cor
60
50
40
30
20
10
0
-10
-20
2.5 hrs Shoot
2.5 hrs Shoot
Mag Control
Mag 14T
Control 14 T
2.5 hrs Shoot
Mag 21T
21 T
(Paul et al., BioMag. Res. Tech. 2006, 4:7) (Davis et al., BioTech. 41 (2006) 554)
[Ikehata et al., J. Appl. Phys. 93 (2003) 6724: yeast in 14 T, 24 hrs: 22 genes ≤ 2 fold changes.]