tmv diffusion in complex solutions: when science goes wrong randy cush* & paul russo louisiana...
TRANSCRIPT
TMV Diffusion in Complex Solutions: When Science Goes WrongRandy Cush* & Paul RussoLouisiana State University
Indiana University Purdue University Indianapolis October 30, 2002
Generic Talk Outline
• Thank hosts for wonderful day
• Tell joke or story
• Explain what we’re trying to do
• Explain what we did• Explain why that is so cool • Destroy evil-doers • Thank friends
• Explain why that is totally wrong • Fix it • Move on
Entanglement in solution?Entanglement in solution?
To isolate spaghetti in "solution" with a fork is To isolate spaghetti in "solution" with a fork is difficult: hydrodynamic interactions interfere difficult: hydrodynamic interactions interfere with entanglement. After solvent is drained to with entanglement. After solvent is drained to obtain a "melt" the entire blob is easily handled. obtain a "melt" the entire blob is easily handled.
Collander
See, e.g., Lodge & Muthukumar, J. Phys. Chem. 1996, 100, 13275-13292
DLS for Molecular Rheology of Complex Fluids:Prospects & Problems
+ + + Wide-ranging autocorrelators> 10 decades of time in one measurement!
– – – Contrast stinks: everything scatters, esp.in aqueous systems or most supercritical fluids, where refractive index matching cannot hide the matrix.
Studied a lot
Barely studied
Our Hypothesis
Solutions containing rodlike diffusers may provide evidence for entanglement-like phenomena in solution…or at least prove interesting, fun and challenging while helping us develop micro-rheology tools.
Evidence would be: * sudden drop-offs in mobility with concentration * failure to follow continuum mechanics
Yeah, challenging…. Early de Gennes paper on
rod/coil diffusion: 19 citations
Same era de Gennes paper on coil/coil reptation: 479 citations
We may expect some problems!
Why it’s worth it: composite precursorfluids, dissolution rate, phase separation rate, relation to GPC, CGE of rods, intracellulartransport.
Desirable rod properties
Stiff—no bendingMonodisperse (all the same size)Non-aggregatingWater-solubleWe don’t have to make ‘em!
Let mother nature do the work: plants make viruses (unwillingly) with most of these qualities.
Seedlings
Sick Plants And close-up of mosaic pattern.
DIY farming--keeping the “A” in LSU A&M
TMV CharacterizationTMV Characterization
Sedimentation, Electron Microscopy and DLS
•Most TMV is intact.•Some TMV is fragmented
–(weaker, faster mode in CONTIN)
•Intact TMV is easy to identify –(stronger, slower mode in CONTIN)
Better Views
http://www.uct.ac.za/depts/mmi/stannard/linda.html
An ear of corn has about as many kernels as TMVhas protein subunits (ca. 2130). The protein
subunits enfold a spiral-wound strand of RNA whichwill encode the next generation. TMV is more
extended than an ear of corn.
A Minnesota Farmboy’s Corny View of TMV
Tobacco from the Carolinas to Connecticut
If tobacco goes away…“Traditionally in Kentucky great mounds of brush are piled and burned in February to prepare a bed for tobacco seedlings. I remember spending most of the day hauling and piling brush. My dad would start the fire in late afternoon and we would sit up most of a cold February or March night stoking the fire, watching the stars, and roasting hot dogs or marshmallows over the bonfire. Many times neighbors would stop by and sit with us for a spell around the fire, talking into the night.”
From: http://www.webcom.com/duane/farm2.html
Rotation & Diffusion of TMV in Polymer Solutions
++ + + Fabulous new autocorrelators for scattering10 decades of time in one measurement!
– – – Contrast for scattering stinks: everything scatters, esp. in aqueous systems where refractive index matching cannot hide matrix.
Matrix Polymer
Solvent
TMV Probe
Solution: Use Polarizers to Hide Matrix
Dynamic Light ScatteringDynamic Light Scattering
Hv = q2Dtrans + 6Drot
LASERVV
HH
PMT
Hv Geometry Hv Geometry (Depolarized)(Depolarized)
Uv Geometry Uv Geometry (Polarized)(Polarized)
VV
Uv = q2Dtrans
o
nq
2/sin4
PMT
LASER
q2
6Drot
q2
Dtrans
StrategyStrategy
•Find polymer that should not “entangle”
•Find a rodlike probe that is visible in DDLS
•Measure its diffusion in solutions of each polymer separately
•Random coil
•Polysaccharide
•Invisible in HvDLS
•Highly-branched
•Polysaccharide
•Invisible in HvDLS
•Rigid rod
•Virus
•Visible in HvDLS
Dextran
Ficoll
TMV
•Find polymer that should (???) “entangle”
BARELYBARELY
0 5 10 15 20 25 30 35 400
1
2
3
4
5
6
7
8
9
10
11
BothViscosity
sp/c
/dL
-g-1
c/g-dL-1
Dextran 670,000 Ficoll 420,000
As expected…
0.0 0.5 1.0 1.5 2.0 2.5 3.0
200
300
400
500D
t /10-8cm
2s-1
Dr /
s-110 L3
c/mg-mL-1
0
1
2
3
4
5
6
Rotation
Translation
Experiments are in dilute regime. TMV overlap (1/L3)
All measurements made at low TMV concentrations—no self-entanglement
Hv correlation Hv correlation functions for 14.5% functions for 14.5% dextran and 28% dextran and 28% ficoll with and ficoll with and without added without added 0.5 mg/mL TMV0.5 mg/mL TMV
The dilute TMV The dilute TMV easily “outscatters” easily “outscatters” either matrixeither matrix
1E-6 1E-5 1E-4 1E-3 0.01 0.1 1 10 100
1.0
1.2
1.4
Ficoll >6000 s acquisition
TMV + Ficoll 600s aquisition
g(2
)
t/s
1E-6 1E-5 1E-4 1E-3 0.01 0.1 1 10 1000.9
1.0
1.1
1.2
1.3
Dextran >6000 s acquisition
TMV + Dextran 215 s acquisition
g(2
)
t/s
Matrix is invisible
0 1 2 3 4 5
0
500
1000
1500
2000
2500
3000
3500
4000
Hv TMV / Dextran / Buffer
Uv TMV / Buffer
Hv TMV / Buffer
/s-1
q2/1010 cm-2
Hey, it works!
I didn’t think—I experimented.
---Wilhelm Conrad Roentgen
0 2 4 6 8 10 12 14 160
1
2
3
4
5
6
Dtr
ans/1
0-8 c
m2
s-1
wt% dextran0 2 4 6 8 10 12 14 16
0
50
100
150
200
250
300
350
Dro
t/ s-
1
wt% dextran
Early results—very slight errors
rotation translationMacromolecules 1997,30, 4920-6.
Stokes-Einstein Plots: if SE works, thesewould be flat. Instead, apparent deviations in
different directions for Drot and Dtrans
0 2 4 6 8 10 12 14 16
0.0
0.5
1.0
1.5
Dt /10
-9g-cm
-s-2
Dr /
g-cm
-1-s
-1
wt% Dextran
0
2
4
0 2 4 6 8 10 12 14 16
0 5 10 15 20
0
2
4
6
8 /cP
Dr/D
t /1
09 cm-2
wt % dextran
0 5 10 15 20
0
20
40
60
80
Dextran overlap
Macromolecules 1997,30, 4920-6.
At the sudden transition: L/c.m. ~ 13 and L/ ~ 120
L
cm
0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 300
1
2
3
4
5
6
Dtr
an
s/10-
8 cm
2 s-
1
wt% ficoll
0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30
0
50
100
150
200
250
300
350
Dro
t/ s-
1
wt% ficoll
rotation
translation
END OF PUBLISHED DATA
We believed that the transition represented topological constraints.
It was suggested that more systems be studied.
BEGIN FICOLL
When we did Ficoll, many more points were added!
0 5 10 15 20 25 300.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
Dtra
ns /10
-9g-cm-1-s
-1
Dro
t /g-
cm-1-s
-1
wt% ficoll
0.0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
Huh? Drot still diving in Ficoll?
rotationtranslation
Maybe we should think now.
The chiral dextran and ficoll alter polarization slightly before and after the scattering center.
With a strongly depolarizing probe, this would not matter, but…
TMV = IHv/IUv ~ 0.003
While matrix scattering is minimal, polarized scattering from TMV itself leaks through a “twisted” Hv setup.
Most damaging at low angles
Mixing in Polarized TMV Light
Uv light from misalign True Hv light
q2 q2
Drot too low
6Drot
q2
6Drot
Even at the highest concentrations, only a few degrees out of alignment.
0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 360
50
100
150
200
250
300
Op
tica
l Ro
tatio
n /
arc
-min
ute
s
wt %
Dextran Ficoll
Polarimeters are long for a reason
0 5 10 15 20 25 30 35
0
50
100
150
200
250
300
350
NewFicollRatio_PR
Right way Wrong way
Dro
t / s
-1
wt% ficoll
Slight, but important, improvement.
Improved Drot/Dtrans Ratio Plots
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 160
1
2
3
4
5
6
7
8
NewDexConcStudy_PR
Dro
t/Dtr
ans/
109 cm
-2
wt% dextran0 5 10 15 20 25 30 35 40
0
1
2
3
4
5
6
7
8
NewFicollRatio_PR
Dro
t/Dtr
ans/
109 c
m-2
wt% ficoll
Improved Stokes-Einstein PlotsBlack = TMV Translation
Blue = TMV Rotation
0 2 4 6 8 10 12 14 160.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
4.5
5.0
0.0
0.2
0.4
0.6
0.8
NewDexConcStudy_PR
Dro
t/g-c
m-1s-1
wt% dextranD
trans /10-9g-cm
-s-2
0 5 10 15 20 25 30 350.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
4.5
5.0
0.0
0.2
0.4
0.6
0.8
NewFicollRatio_PR
Dro
t/g-c
m-1 s
-1
wt% ficoll
Dtrans / 10
-9g-cm-s
-2
Check Dtrans by FPR a.k.a. FRAP
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 160
1
2
3
4
5
6
FPRtmvDex_PR
Hv DLS FPR
Dtr
ans/
10-8
cm2 s-1
wt% dextran
Hydrodynamic Ratio—Effect of Matrix M at High Matrix Concentration
0 2 4 6 8 10 12 14 16 18 200
1
2
3
4
5
6
7
8
9DextranMWStudy_PR
Dro
t/Dtr
ans/
109 cm
-2
dextran MW/ 105 daltons
Effect of Dextran Molecular Weight—High Dextran Concentration (~ 15%)
10000 100000 1000000 1E71
10
100
DextranMWStudy_PR
-0.62 ± 0.04
Dro
t / s
-1
Dextran MW10000 100000 1000000 1E7
0.1
1
10
DextranMWStudy_PR
-0.72 ± 0.01
Dtr
ans/
10-9
cm
2 s-1
Dextran MW
TMV Translation TMV Rotation
1 10 100
0.01
0.1
1
10
100
1000
10000
G' /
Pa
/ Hz
5% w/w 30% w/w 35% w/w 40% w/w
Behavior of Dextran Matrix
Pathological Science?*
The magnitude of the effect is substantially independent of the intensity of the causative agent.
The effect is of a magnitude that remains close to the limits of detectability; or, many measurements are necessary because of the very low statistical significance of the results.
It makes claims of great accuracy.
It puts forth fantastic theories contrary to experience.
Criticisms are met by ad hoc excuses.
The ratio of supporters to critics rises up to somewhere near 50 percent and then falls gradually to oblivion.
LangmuirNobel 1932
*The science of things that aren’t so Lecture December 18, 1953 GE Labs
Studying “entangled” TMV by FPR
Fluorescentlylabeled probe rod
Unlabeled rods
Solvent
Ld
1
1
3
3
3
L
L
L
1
1
2
2
2
dL
dL
dL
1
14
2
2
2
2
A
A
dLA
LC formation = 4/A2 5/dL2
Reduced # Density dL2/5
Doi-Edwards-Onsager Reference Volumes for Rods = number density = # of rods per unit volume
D expected to decrease by half, but at what concentration?
D
D
X
Modulation FPR Device a’la Lanni & Ware
*
*
*
*
AOM
M
M
D
RR
DM
OBJ
S
PMT
PA OS
TA/PVD
L
SCOPE
Measuring Translational Diffusion
0 200 400 600 800 10000
1
2
3
4
DC
Sig
nal
Con
tras
t
t/s
0 2 4 6 8 10 12 140.000
0.005
0.010
0.015
0.020
0.025
0.030
0.035
0.040
/H
z
K2 / 105cm-2
FPR Data for TMV Solution: very low dye content.
0.1 1 10 1001
2
3
4
5
6
7
Source: Cush Monthly Report (5/1/01)
1/dL21/L3
Dse
lf /
10 -8
cm
2 s
-1
cTMV
/ mg mL-1
Dtracer self of TMV vs. cTMV
TMV vs Helical, Semiflexible Polymer
0.0 0.2 0.4 0.6 0.8 1.00.0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1.0
1.1
(Dse
lf/Do)
PB
LG /
(D
self/D
o)D
MF
PBLG
TMV
D
self /
Do
/*
Thanks!
Randy CushDavid Neau
Ding Shih
Holly Ricks
Jonathan Strange
Amanda Brown
Zimei Bu
Zuhal & Savas Kucukyavuz—METU
Seth Fraden—Brandeis
Dan DeKee—Tulane
Nancy Thompson—Chapel Hill N$F
THE END
Misalignment from thick polarizer in “active” part of detector train, exacerbated by tiny cells
used to squelch optical rotation & conserve TMV
shifted by thick polarizer element
correctly aligned scattered beam
Ld
1
1
3
3
3
L
L
L
1
1
2
2
2
dL
dL
dL
1
14
2
2
2
2
A
A
dLA
LC formation = 4/A2 5/dL2
Reduced # Density dL2/5
Doi-Edwards-Onsager Reference Volumes for Rods = number density = # of rods per unit volume
Conditions for use as a ProbeConditions for use as a Probe
•Is the TMV Probe Dilute?A TMV concentration of 0.5 mg/mL, well below the
theoretical overlap concentration, was chosen. See Figure 2.•Does dilute TMV overwhelm the matrix scattering?
At 0.5 mg/mL the TMV easily “outscatters” both matrices. See Figure 3.
•Is the probe compatible with the matrix?-Solutions stable months after preparation
-Angle dependent Hv SLS
-Dtrans goes up, not down (Figures 6 & 8)
Effect of Dextran ConcentrationEffect of Dextran Concentration
• The dependence of Drot and Dtrans upon added dextran is shown in Figure 4.
• The quotient Drot/Dtrans is plotted against viscosity in Figure 5. By combining both transport coefficients, each inversely proportional to viscosity in dilute solution, we can remove the effect of solution viscosity. • Figure 6 reveals like positive deviations from the Stokes-Einstein continuum expectation that diffusion be inversely proportional to viscosity (below 6.5%).
•Above 6.5% the deviations become greater for both Drot and Dtrans but in opposite directions
There once was a theorist from Francewho wondered how molecules dance.“They’re like snakes,” he observed, “As they follow a curve, the large onesCan hardly advance.”
D ~ M -2
P.G. de GennesScaling Concepts in Polymer Physics
Cornell University Press, 1979
de Gennes
OutlineOutline• Characterize the TMV
– Is it intact and behaving properly?
• Establish conditions for use of TMV as probe– Can the probe be dilute and still overwhelm the
matrix scattering?– Will the probe stay mixed with the matrix solutions
without aggregating?
• Show the effect of the dextran and ficoll matrices on TMV diffusion
Effect of Ficoll ConcentrationEffect of Ficoll Concentration
• The dependence of Drot and Dtrans upon added dextran is shown in Figure 4.
• The quotient Drot/Dtrans is plotted against viscosity in Figure 7.
• Figure 8 shows slight like positive deviations from the Stokes-Einstein continuum expectation (below 11%).
• Above about 11% ficoll the deviation slowly becomes greater for Drot and slightly greater for Dtrans but in opposite directions
• Figure 9 compares TMV behavior in ficoll to that in dextran.
0 5 10 15 20 25 300
2
4
6D
rot /
Dtr
ans
/109 cm
-2
wt% ficoll
0
20
40
60
80/ cP
0 10 20 30 40 50 60
-1
0
1
2
3
4
5
6
7
8 Ficoll Dextran
Dro
t / D
tran
s/ 1
09 cm-2
/ cP
Too-Good-to-be-True Conclusion?Too-Good-to-be-True Conclusion?
• Below 6.5% dextran the diffusion of the rodlike TMV probe is controlled mostly by viscosity.
• Above 6.5% dextran a sharp transition suggests topological constraint for TMV rotation while translation is not much affected.
• The transition is more gradual in ficoll.• The TMV probe senses something different for
linear vs. highly branched polymers in solution.• Looks good for topological models!
Alternate Conclusion?• The systems studied so far place (impossibly?) strict
demands on geometric & polarization alignment. – Revised polarization placement– Difficult zero angle measurements requiring even more
TMV
• New systems must be studied:– TMV is OK – Dextran/Ficoll must go!
• Depolarized probe diffusion has the potential, as yet unrealized, to assess strength of hydrodynamic vs. topological effects.
To Do
Get Cush to estimate the total number of TMV’s he produced.
Slopes of intrinsic viscosity plot don’t meet the 0.5 rule.
What has Deutch & Pecora to do with Dtrans vs. M?
What does regular viscosity have to say about M-dependence?
At what concentration was that M-dependent stuff done?