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Neutron scattering for biologyApplications in membrane biophysics
Thad HarrounCanadian Neutron Beam Centre
28 September, 2005
Outline
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■ Some important properties of neutrons.■ How do neutrons interact with matter?■ How are neutrons “made”?■ Survey of neutron scattering experiments in membrane biophysics.
Properties of neutrons
Properties ofneutrons
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■ Mechanical
◆ Mass◆ Angular momentum◆ . . .
■ Electrical
◆ Charge◆ Magnetic dipole moment◆ Electric dipole moment◆ . . .
■ Nuclear
◆ Free lifetime◆ Decay modes◆ Intrinsic Parity, P◆ Isospin, I◆ Baryon number, B◆ Strangeness, S◆ . . .
Mass
Properties ofneutrons
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The mass of the neutron is Mn = 1.008 664 915 60(55) atomicmass units.
Note that Mn > Mp + Me, which makes beta decay possible.[Mn 939.565 MeV - Mp 938.272 MeV - Me 0.510 MeV = 0.782 MeV]
The reaction n → p + e + νe is the prototype for essentially allnaturally occurring radioactivity.
The lifetime of free neutron is about 15 minutes.
Electric and magnetic moments
Properties ofneutrons
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Since the neutron has internal charge and distribution due to thequarks, in principle it can have various electric/magneticmoments, but:
■ The total charge is zero.■ Magnetic dipole moment = -0.966 x 10−26 J T−1
■ Spin = 12
Energy and wavelength
Properties ofneutrons
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A neutron traveling at velocity v has a wavelength ofλ = h/(mv), where h is Planck’s constant, m is the neutronmass, and has a kinetic energy E = 1
2mv2.
The neutron’s momentum is given by ~p = m~v = h̄~k, and|~k| = 2πλ
Elastic scattering
Interactions ofneutrons
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Neutrons that scatter undergo a change in momemtum,~q = ~k0 − ~k1.
k0 k1
d
θθ
Bragg scattering
Interactions ofneutrons
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If |~q| = 2πd =4π sin θ
λ , we get constructive interference in thedirection θ.
k0 k1
d
θθ
q
k0
k1 2πd
θ
θ
X-ray interactions with matter
Interactions ofneutrons
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X-rays scatter from the electrons in the electron cloud. Since thecloud fills most of the atom volume, the source of the scatteredwaves are “fuzzy”.
Neutron interaction with matter - 1
Interactions ofneutrons
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Nuclear dimensions ∼ 10−15m, a pin-point compared to thetypical neutron wavelength, ∼ 10−10m. For neutrons, materialsare mostly empty space.
Neutron interaction with matter - 2
Interactions ofneutrons
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There is also the interaction between unpaired electron spins inmagnetic materials and the neutron magnetic moment. Notmuch use in biology!
Scattering length
Interactions ofneutrons
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Neutron-atom interactions are due to the short range nuclearstrong force. The neutron interacts only within an effectiveimpact radius b ∼ Rn + RA.
A
n
“cross section”Effective
b has the units of length and ∼ 10−12cm.
Scattering cross section
Interactions ofneutrons
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We measure the differential cross section, defined as
dσ
dΩ=
neutrons s−1 scattered into dΩ
flux dΩ= |b2|
Neutrons
Sample
Detector
dΩ
The total cross section is then σ =∫
(dσdΩ)dΩ = 4πb2.
(1 barn = 10−24 cm2)
Scattering length
Interactions ofneutrons
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So, what is this value b? It is a measure of the ability of an atomto scatter neutrons.
It is a characteristic of every isotope of every element, that mustbe determined empirically.
X-ray scattering length
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1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18
1
H0.282
2
He0.564
3
Li0.846
4
Be1.128
5
B1.41
6
C1.692
7
N1.974
8
O2.256
9
F2.538
10
Ne2.82
11
Na3.102
12
Mg3.384
13
Al3.666
14
Si3.948
15
P4.23
16
S4.512
17
Cl4.794
18
Ar5.076
19
K5.358
20
Ca5.64
21
Sc5.922
22
Ti6.204
23
V6.486
24
Cr6.768
25
Mn7.05
26
Fe7.332
27
Co7.614
28
Ni7.896
29
Cu8.178
30
Zn8.46
31
Ga8.742
32
Ge9.024
33
As9.306
34
Se9.588
35
Br9.87
36
Kr10.152
37
Rb10.434
38
Sr10.716
39
Y10.998
40
Zr11.28
41
Nb11.562
42
Mo11.844
43
Tc12.126
44
Ru12.408
45
Rh12.69
46
Pd12.972
47
Ag13.254
48
Cd13.536
49
In13.818
50
Sn14.1
51
Sb14.382
52
Te14.664
53
I14.946
54
Xe15.228
55
Cs15.51
56
Ba15.792
57
La16.074
72
Hf20.304
73
Ta20.586
74
W20.868
75
Re21.15
76
Os21.432
77
Ir21.714
78
Pt21.996
79
Au22.278
80
Hg22.56
81
Tl22.842
82
Pb23.124
83
Bi23.406
84
Po23.688
85
At23.97
86
Rn24.252
87
Fr24.534
88
Ra24.816
89
Ac25.098
58
Ce16.356
59
Pr16.638
60
Nd16.92
61
Pm17.202
62
Sm17.484
63
Eu17.766
64
Gd18.048
65
Tb18.33
66
Dy18.612
67
Ho18.894
68
Er19.176
69
Tm19.458
70
Yb19.74
71
Lu20.022
90
Th25.38
91
Pa25.662
92
U25.944
93
Np26.226
94
Pu26.508
95
Am26.79
96
Cm27.072
bX−ray = Z × re = Z × 0.2382 × 10−12 cm
Neutron scattering length
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1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18
1
H−3.739
2
He3.26
3
Li−1.9
4
Be7.79
5
B5.3
6
C6.646
7
N9.36
8
O5.803
9
F5.654
10
Ne4.566
11
Na3.63
12
Mg5.375
13
Al3.449
14
Si4.1491
15
P5.13
16
S2.847
17
Cl9.577
18
Ar1.909
19
K3.67
20
Ca4.7
21
Sc12.29
22
Ti−3.438
23
V−0.3824
24
Cr3.635
25
Mn−3.73
26
Fe9.45
27
Co2.49
28
Ni10.3
29
Cu7.718
30
Zn5.68
31
Ga7.288
32
Ge8.185
33
As6.58
34
Se7.97
35
Br6.795
36
Kr7.81
37
Rb7.09
38
Sr7.02
39
Y7.75
40
Zr7.16
41
Nb7.054
42
Mo6.715
43
Tc6.8
44
Ru7.03
45
Rh5.88
46
Pd5.91
47
Ag5.922
48
Cd4.87
49
In4.065
50
Sn6.225
51
Sb5.57
52
Te5.8
53
I5.28
54
Xe4.92
55
Cs5.42
56
Ba5.07
57
La8.24
72
Hf7.7
73
Ta6.91
74
W4.86
75
Re9.2
76
Os10.7
77
Ir10.6
78
Pt9.6
79
Au7.63
80
Hg12.692
81
Tl8.776
82
Pb9.405
83
Bi8.532
84
Po0
85
At0
86
Rn0
87
Fr0
88
Ra10
89
Ac0
58
Ce4.84
59
Pr4.58
60
Nd7.69
61
Pm12.6
62
Sm0.8
63
Eu7.22
64
Gd6.5
65
Tb7.38
66
Dy16.9
67
Ho8.01
68
Er7.79
69
Tm7.07
70
Yb12.43
71
Lu7.21
90
Th10.31
91
Pa9.1
92
U8.417
93
Np10.55
94
Pu0
95
Am8.3
96
Cm0
Incoherent scattering and absorption
Interactions ofneutrons
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1. Neutron-nucleus system has two spin states: I ± 12, with two
scattering lengths: b+, b−.Thermally averaged scattering length
〈b〉 =1
2I + 1
[
(I + 1) b+ + Ib−]
〈
b2〉
=1
2I + 1
[
(I + 1) (b+)2 + I(b−)2]
,
σcoherent = 4π 〈b〉2. σtotal = 4π
〈
b2〉
.σtotal − σcoherent = σincoherent.
2. Neutron capture by the nucleus σabsorption.
X-ray scattering cross section
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1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18
1
H0.655
2
He1.94
3
Li5.76
4
Be16.6
5
B41.5
6
C89.9
7
N173
8
O304
9
F498
10
Ne768
11
Na1140
12
Mg1610
13
Al2220
14
Si2970
15
P3880
16
S4970
17
Cl6240
18
Ar7720
19
K9400
20
Ca11300
21
Sc13500
22
Ti15900
23
V18500
24
Cr21300
25
Mn24600
26
Fe28000
27
Co31400
28
Ni4760
29
Cu5470
30
Zn6290
31
Ga7190
32
Ge8190
33
As9290
34
Se10500
35
Br11800
36
Kr13200
37
Rb14800
38
Sr16500
39
Y18300
40
Zr20300
41
Nb22300
42
Mo24600
43
Tc27000
44
Ru29500
45
Rh32300
46
Pd35200
47
Ag38200
48
Cd41500
49
In45000
50
Sn48600
51
Sb52500
52
Te56500
53
I60700
54
Xe65200
55
Cs70000
56
Ba75000
57
La80300
72
Hf46000
73
Ta48500
74
W51300
75
Re57200
76
Os58000
77
Ir62400
78
Pt63400
79
Au66900
80
Hg66800
81
Tl111000
82
Pb117000
83
Bi123000
84
Po129000
85
At126000
86
Rn143000
87
Fr149000
88
Ra149000
89
Ac174000
58
Ce85700
59
Pr91200
60
Nd96800
61
Pm102000
62
Sm108000
63
Eu110000
64
Gd105000
65
Tb84700
66
Dy97700
67
Ho34700
68
Er36700
69
Tm39300
70
Yb41000
71
Lu45000
90
Th172000
91
Pa153000
92
U161000
93
Np169000
94
Pu165000
95
Am181000
96
Cm179000
Neutron total cross section
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1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18
1
H82.3526
2
He1.34747
3
Li71.87
4
Be7.6376
5
B772.24
6
C5.5545
7
N13.41
8
O4.23219
9
F4.0276
10
Ne2.667
11
Na3.81
12
Mg3.773
13
Al1.734
14
Si2.338
15
P3.484
16
S1.556
17
Cl50.3
18
Ar1.358
19
K4.06
20
Ca3.26
21
Sc51
22
Ti10.44
23
V10.18
24
Cr6.54
25
Mn15.45
26
Fe14.18
27
Co42.78
28
Ni22.99
29
Cu11.81
30
Zn5.241
31
Ga9.58
32
Ge10.8
33
As10
34
Se20
35
Br12.8
36
Kr7.68
37
Rb7.18
38
Sr7.53
39
Y8.98
40
Zr6.645
41
Nb7.405
42
Mo8.19
43
Tc26.3
44
Ru9.16
45
Rh149.4
46
Pd11.38
47
Ag68.29
48
Cd2526.5
49
In196.42
50
Sn5.518
51
Sb8.81
52
Te9.02
53
I9.96
54
Xe23.9
55
Cs32.9
56
Ba4.48
57
La18.63
72
Hf114.3
73
Ta26.61
74
W22.9
75
Re101.2
76
Os30.7
77
Ir439
78
Pt22.01
79
Au106.4
80
Hg399.1
81
Tl13.32
82
Pb11.289
83
Bi9.1898
84
Po0
85
At0
86
Rn12.6
87
Fr0
88
Ra25.8
89
Ac0
58
Ce3.57
59
Pr14.16
60
Nd67.1
61
Pm189.7
62
Sm5961
63
Eu4539.2
64
Gd49880
65
Tb30.24
66
Dy1084.3
67
Ho73.12
68
Er167.7
69
Tm106.38
70
Yb58.2
71
Lu81.2
90
Th20.73
91
Pa211.1
92
U16.478
93
Np190.4
94
Pu0
95
Am84.3
96
Cm0
The penetrating power of neutrons
Interactions ofneutrons
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The penetrating power of neutrons
Interactions ofneutrons
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Neutron sources
Neutron sources
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Where can you get neutrons?
Recall that free neutrons have a half-life of about 15 mins.
There are lots of “stored” neutrons in the very heavy elements.
Reactor sources
Neutron sources
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CNBC, Chalk River, Ontario
Neutron sources
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Fission production
Neutron sources
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235U(92p + 143n) + n → X + Y + 2.5n + Q
■ X,Y are nuclei with atomic mass ∼ 95 - 140 u■ ∼ 2.5n per fission■ Q ∼ 210 MeV per fission released
Reactor sources
Neutron sources
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CORE
WARM WATER
TO HEAT
EXCHANGERS
COOL WATER
FROM PUMPS
BEAM
TUBES
STEEL
SHIELDING
CONCRETE
SHIELDING
DECK PLATE
MAIN
FLOOR
10 m
9 m
NEUTRONS
n(v) = 4√π
(
m2kBT
)3/2v2 exp
(
− mv2
2kBT
)
Neutron energies
Neutron sources
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0
10
20
30
40
50
100 1000
Neutron velocity (m/s)
5 K50 K
300 K
0.0001 0.001 0.01 0.1
Neutron energy (eV)
1 10
Neutron wavelength (Å)
NRU spectrometers
Neutron sources
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NRU spectrometers
Neutron sources
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NRU spectrometers
Neutron sources
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NRU spectrometers
Neutron sources
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NIST, Gaithersberg, Maryland
Neutron sources
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NIST, Gaithersberg, Maryland
Neutron sources
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Spallation sources
Neutron sources
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ISIS, Oxford, U.K.
Neutron sources
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ISIS, Oxford, U.K.
Neutron sources
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SNS, Oak Ridge, Tennesse
Neutron sources
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Neutron flux
Neutron sources
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X-ray synchrotron flux ∼ 1013 − 1015 photons/mm2-sec-1% spectrum
Neutrons and biology
Neutrons andbiology
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Bound Atom Scattering Lengths and Cross Sections for Typical Elements in
Biomaterials
Atom Nucleus bc σc σi σabs* f
(10−12 cm) (10−24 cm2) (10−24 cm2) (10−24 cm2) (
Hydrogen 1H -0.374 1.76 79.7 0.33 0.28Deuterium 2H 0.667 5.59 2.01 0 0.28Carbon 12C 0.665 5.56 0 0 1.69Nitrogen 14N 0.930 11.1 0 1.88 1.97Oxygen 16O 0.580 4.23 0 0 2.25Fluorine 19F 0.556 4.03 0 0 2.53
Phosphorous P† 0.513 3.31 0 0.17 4.22
Chlorine Cl† 0.958 11.53 5.9 33.6 4.74
The structure of membrane lipids
Neutrons andbiology
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Hydrogen/Deuterium contrast
Neutrons andbiology
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0
0.02
0.04
0.06
0 20 40 60 80 100
ρ (1
0−12
cm
Å−
3 )
% D2O
Water
RNA
Protein
Lipid head group
CH2
The structure of membrane lipids
Neutrons andmembranebiophysics
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The cell membrane
Neutrons andmembranebiophysics
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Composition of cell membranes.
Neutrons andmembranebiophysics
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Membrane Protein (%) Lipid (%) Carbohydrate (%)Myelin 18 79 3Human erythrocyte plasma membrane 49 43 8Amoeba plasma membrane 54 42 4Mycoplasma cell membrane 58 37 1.5Halobacterium purple membrane 75 25 0
Lipid bilayers
Neutrons andmembranebiophysics
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Sample preparation - 1
Neutrons andmembranebiophysics
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Incident Diffracted
d
2q
q
Si Substrate
Sample preparation - 2
Neutrons andmembranebiophysics
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Experimental data
Neutrons andmembranebiophysics
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hq = hd =2h sin θ
λ
I ∝ |F (q)|2 = |∑
bi exp(−iqzi)|2
100
1000
0 2 4 6 8 10 12 14 16 18
Neu
tron
cou
nts
2θ (°)
Data analysis
Neutrons andmembranebiophysics
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ρ(z) = ρ0 +hmax∑
h=1
Fh cos(2πhz/d)
−0.01
−0.005
0
0.005
0.01
0.015
0.02
−30 −20 −10 0 10 20 30
Sca
tterin
g Le
ngth
Den
sity
(ar
b. u
nits
)
z (Å)
DMPC−d3DMPC
−0.005
0
0.005
0.01
0.015
0.02
0.025
−30 −20 −10 0 10 20 30
Sca
tterin
g Le
ngth
Den
sity
(ar
b. u
nits
)
DMPC−d3 Label
Area 0.077Width 4.2 Center 0.0
Label distributionFit
Deuterium labelling
Neutrons andmembranebiophysics
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ρ(z) = ρ0 +hmax∑
h=1
(
FDh − FHh
)
cos(2πhz/d)
−0.01
−0.005
0
0.005
0.01
0.015
0.02
−30 −20 −10 0 10 20 30
Sca
tterin
g Le
ngth
Den
sity
(ar
b. u
nits
)
z (Å)
DMPC−d3DMPC
−0.005
0
0.005
0.01
0.015
0.02
0.025
−30 −20 −10 0 10 20 30
Sca
tterin
g Le
ngth
Den
sity
(ar
b. u
nits
)
DMPC−d3 Label
Area 0.077Width 4.2 Center 0.0
Label distributionFit
cholesterol in polyunsaturated lipids
Neutrons andmembranebiophysics
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0
0.02
0.04
0.06
0.08
−30 −20 −10 0 10 20 30
Distance from bilayer center (Å)
20:4−20:4 PC
0
0.02
0.04
0.06
Net
uron
sca
tteri
ng le
ngth
den
sity
(x1
0−7
Å−2
)
18:0−20:4 PC
0
0.02
0.04
0.06 18:1−18:1 PC
0
0.02
0.04
0.0616:0−18:1 PC
Center of bilayer
Headgroup
Water
Acyl chain
A B C
Labelling membrane bound proteins
Neutrons andmembranebiophysics
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Finding amino acids in the bilayer
Neutrons andmembranebiophysics
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−0.02
0.02
0.06
0.1
0.14
0 5 10 15 20 25
Labe
l Pro
file
Phe4DifferenceGauss fit
0 5 10 15 20 25
z (°)
Phe8
0 5 10 15 20 25
Phe12
We see the time-averaged fluctuation amplitude for each residuethat was deuterium labeled.
Protein structure modeling
Neutrons andmembranebiophysics
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X
Y
Z
Combined with a model of protein structure, determining theorientation is a simple problem of geometry.
Protein structure modeling
Neutrons andmembranebiophysics
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Insights into the protein’s behavior while part of the membranecan be gained through modeling the data.
Neutrons andmembranebiophysics
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The mesh represents the interface between the membrane and the
water.
Slightly different structures have very different orientations,which are clues to the protein’s function.
Small angle scattering
Neutrons andmembranebiophysics
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Recall Bragg’s law: q = 4πλ sin θ =2πd
The angles at which neutrons are diffracted scales inversely withthe size of the scattering object:2θ ∼ λd
To probe the shape and size of objects on the length scales of60∼1000 Å, then 2θ = 0.3◦ ∼ 5◦ (λ =10 Å).
We are no longer on the atomic scale. Consider the sample as a
continuum of scattering density.
Instead of bi for each atom i, consider b(~r).
Small angle scattering
Neutrons andmembranebiophysics
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The neutron scattering from variations in b(~r) depends on twoterms:
■ F (q) depends on the shape of the scattering objects■ S(q) depends on the distribution of the objects
Solvent
Object
b(r)
Membrane pore formation
Neutrons andmembranebiophysics
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Antimicrobial proteins work by forming pores in the membrane,which causes cell death.How big are these pores? What is their lateral density?
In-plane diffraction
Neutrons andmembranebiophysics
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The theory is drawn from liquid scattering, only this liquid is 2D.It accounts for pore size and correlations intra- and inter-bilayer.
q = qr r̂ + qz ẑ
I(qz,qr) = N | F (qz,qr) |2 S(qz,qr)
S(qz,qr) = S00(qr) + 2 cos(qzD)S01(qr) + ...
S0m(qr) = δ0m +
∫
(n0m(r) − n̄)J0(qr)2πrdr
In-plane diffraction
Neutrons andmembranebiophysics
Brock University Neutrons for Biology – 61 / 74
Mellitin pores detected by off-plane diffraction.
In-plane diffraction
Neutrons andmembranebiophysics
Brock University Neutrons for Biology – 62 / 74
In-plane diffraction
Neutrons andmembranebiophysics
Brock University Neutrons for Biology – 63 / 74
Melittin pores can semi-crystallize into a 3D lattice.
AFMnet: potential drug delivery
Neutrons andmembranebiophysics
Brock University Neutrons for Biology – 64 / 74
Bicellar mixtures
Neutrons andmembranebiophysics
Brock University Neutrons for Biology – 65 / 74
It is currently thought that mixtures of long and short chain lipidsform a liquid crystalline phase of bicelles - bilayered micelles.
Isotropic bicelles
Brock University Neutrons for Biology – 66 / 74
10-1
100
101
102
103
104
I (a
rbitr
ary
unit)
5 60.01
2 3 4 5 60.1
2 3
q (Å-1
)
35 oC
10 oC
55 oC
45 oC
q-1
Chiral nematic ribbons
Brock University Neutrons for Biology – 67 / 74
10-1
100
101
102
103
104
I (a
rbitr
ary
unit)
5 60.01
2 3 4 5 60.1
2 3
q (Å-1
)
35 oC
10 oC
55 oC
45 oC
q-1
Chiral nematic ribbons
Neutrons andmembranebiophysics
Brock University Neutrons for Biology – 68 / 74
Multilamellar vesicles
Brock University Neutrons for Biology – 69 / 74
10-1
100
101
102
103
104
I (a
rbitr
ary
unit)
5 60.01
2 3 4 5 60.1
2 3
q (Å-1
)
35 oC
10 oC
55 oC
45 oC
q-1
Multilamellar vesicles
Neutrons andmembranebiophysics
Brock University Neutrons for Biology – 70 / 74
Smectic lamellae
Brock University Neutrons for Biology – 71 / 74
10-1
100
101
102
103
104
I (a
rbitr
ary
unit)
5 60.01
2 3 4 5 60.1
2 3
q (Å-1
)
35 oC
10 oC
55 oC
45 oC
q-1
Smectic lamellae
Neutrons andmembranebiophysics
Brock University Neutrons for Biology – 72 / 74
Liposomes
Brock University Neutrons for Biology – 73 / 74
10-2
10-1
100
101
102
103
104
I (ar
bitr
ary
unit)
4 6 80.01
2 4 6 80.1
2
q (Å-1
)
0.1 wt%10
oC
45 oC
10 oC
Acknowledgments
Neutrons andmembranebiophysics
Brock University Neutrons for Biology – 74 / 74
■ NPMR NRC Chalk River, Canada■ AFMnet, University of Gueplh
◆ John Katsaras◆ Mu-Ping Nieh◆ Jeremy Pencer◆ Staecie Institute of Molecular Sciences
■ University of Edinburgh, Scotland, U.K.
◆ Jeremy Bradshaw◆ Richard Ashley◆ Malcolm Darkes◆ Sarah Davies◆ Biotechnology and Biological Sciences Research Council◆ Welcome Trust
■ Rice University, Houston, Texas
◆ Huey W. Huang◆ William Heller◆ Lin Yang◆ NIH - Houston Molecular Biophysics Program
OutlineProperties of neutronsProperties of neutronsMassElectric and magnetic momentsEnergy and wavelength
Interactions of neutronsElastic scatteringBragg scatteringX-ray interactions with matterNeutron interaction with matter - 1Neutron interaction with matter - 2Scattering lengthScattering cross sectionScattering lengthX-ray scattering lengthNeutron scattering lengthIncoherent scattering and absorptionX-ray scattering cross sectionNeutron total cross sectionThe penetrating power of neutronsThe penetrating power of neutrons
Neutron sourcesNeutron sourcesReactor sourcesCNBC, Chalk River, OntarioFission productionReactor sourcesNeutron energiesNRU spectrometersNRU spectrometersNRU spectrometersNRU spectrometersNIST, Gaithersberg, MarylandNIST, Gaithersberg, MarylandSpallation sourcesISIS, Oxford, U.K.ISIS, Oxford, U.K.SNS, Oak Ridge, TennesseNeutron flux
Neutrons and biologyNeutrons and biologyThe structure of membrane lipidsHydrogen/Deuterium contrast
Neutrons and membrane biophysicsThe structure of membrane lipidsThe cell membraneComposition of cell membranes.Lipid bilayersSample preparation - 1Sample preparation - 2Experimental dataData analysisDeuterium labellingcholesterol in polyunsaturated lipidsLabelling membrane bound proteinsFinding amino acids in the bilayerProtein structure modelingProtein structure modelingSmall angle scatteringSmall angle scatteringMembrane pore formationIn-plane diffractionIn-plane diffractionIn-plane diffractionIn-plane diffractionAFMnet: potential drug deliveryBicellar mixturesIsotropic bicellesChiral nematic ribbonsChiral nematic ribbonsMultilamellar vesiclesMultilamellar vesiclesSmectic lamellaeSmectic lamellaeLiposomesAcknowledgments