times less
than in gas!
WHY?
H2O
Henry’s constant
(kH,cc)-1 =
for : = 50/1
for ethanol: = 1/47000
[in gas]
[in liquid]
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Презентация на тему Elementary interactions: hydrophobic & electrostatic; SS and coordinate bonds
Содержание
- 2. Hydrophobic effectConcentration of C6H14 in
- 3. ENTROPY:SE = kB • ln[ME];
- 5. Experiment: ΔG intA→B= kBT•ln([C1 in A]/[C1 in
- 6. -2/3 +1/3Loss: S
- 7. High heat capacity d(ΔH)/dT:Melting of“iceberg”
- 8. 20-25 cal/mol per Å2 of molecularaccessible non-polar surfaceOctanol → Water
- 9. Семён Ефимович Бреслер (1911 – 1983) Давид Львович Талмуд
- 10. ______largeeffect_______ small______ large
- 11. Electrostatics in uniform media: potential ϕ1
- 12. (1736-1806)
- 13. Water => PROTEIN
- 14. Non-uniform media: εeff = ?
- 15. Non-uniform media: εeff = ?
- 16. Non-uniform media: εeff = ?intermediate dipole
- 17. ϕ = q/ε1r
- 18. - - - -ϕ = (q/ε1)/r
- 19. Good estimate fornon-uniform media+ -+ - +
- 20. εeffective in non-uniform media15040
- 21. Large distance:
- 22. At atomic distances in water:
- 23. Protein engineering experiments:ϕ(r) = ΔpH × 2.3RT ⇒⇒ εeff(r)
- 24. Sir Alan Roy Fersht, 1943Protein engineering
- 25. Dipole interactions (e.g., H-bonds):(HO)-1/3-H+1/3::::::(OH)-1/3-H+1/3Quadruple interactionsAlso: charge-dipole, dipole-quadruple,
- 26. Electrostatic interactions also occur between charge (q)
- 27. Debye-Hückel screening of electrostatic by ions:U =
- 28. Electrostatics is T- dependent;U = (1/ε)•(q1q2/r)is free
- 29. S-S bonds (Cys-Cys) exchange: entropic forceS-S bond is not stable within a cell
- 30. Скачать презентацию
- 31. Похожие презентации
Hydrophobic effectConcentration of C6H14 in H2O:50 times lessthan in gas!WHY?H2OHenry’s constant(kH,cc)-1 = for : =
![ENTROPY:SE = kB • ln[ME]; ME=number_of_states(E)Why kB? What is kB?Because](/img/tmb/15/1439696/467bdf22b303ef2ca7331d618dfff680-720x.jpg "Elementary interactions: hydrophobic & electrostatic; SS and coordinate bonds")
![Experiment: ΔG intA→B= kBT•ln([C1 in A]/[C1 in B])ΔSintA→B = -d(ΔGintA→B)/dTΔHintA→B = ΔGintA→B](/img/tmb/15/1439696/c6caa6bf654fb75e4ea31d6c3759f9ab-720x.jpg "Elementary interactions: hydrophobic & electrostatic; SS and coordinate bonds")
![Debye-Hückel screening of electrostatic by ions:U = [q1q2/εr]•exp(-r/D) ;](/img/tmb/15/1439696/8c2f89ac5188ee57c8d350370b34ca76-720x.jpg "Elementary interactions: hydrophobic & electrostatic; SS and coordinate bonds")
Слайд 2
Hydrophobic effect
Concentration of C6H14
in H2O:
50
times less
for : = 50/1
for ethanol: = 1/47000
Слайд 3
ENTROPY:
SE = kB • ln[ME]; ME=number_of_states(E)
Why
kB? What is kB?
Because entropy SE comes to the
free energyFE = E – TSE (measured in energy units) as TSE,
and T is measured in degrees, while
ln[number of states] is dimensionless;
Thus, kB is energy_unit/degree
FREE ENERGY:
Probability(E) ~ ME•exp(-E/kBT) = exp(-FE/kBT)
Boltzmann
F=E-TS at V=const;
G=H-TS=(E+PV)-TS at P=const (better for experiment)
-------------------
Слайд 4
Gint : “Free energy of interactions”
(“mean force potential”)Chemical potential:
μ ≡ G(1) = Gint - T•kBln(V(1)) ≡ Gint + T•kBln[C]
EQUILIBRIUM for transition
of molecule 1 from A to B: GA(1) = GB(1)
chemical potentials in A and B are equal
ΔGintA→B ≡ GintB – GintA
ΔGintA→B= kBT•ln([CinA]/[CinB])
===================================================
Слайд 5
Experiment: ΔG intA→B= kBT•ln([C1 in A]/[C1 in B])
ΔSintA→B
= -d(ΔGintA→B)/dT
ΔHintA→B = ΔGintA→B +TΔSintA→B
C6H12
[C] of C6H12
in H2O:
50
times lessthan in gas;
100000 times
less than in
liquid C6H12
T=2980K=250C
Слайд 9
Семён Ефимович Бреслер
(1911 – 1983)
Давид Львович Талмуд
(1900
- 1973)
Cyrus Homi Chothia, 1942
Hydrophobic
effect
&
amino acid
water-accessible
surface
Hypothesis on a
role of hydrophobic effect in protein folding Hydrophobic
effect
&
denaturationof proteins
Charles Tanford
(1921 - 2009)
General physical
features of
Hydrophobic
effect
Слайд 11
Electrostatics in uniform media:
potential ϕ1 =
q1/εr
Interaction of two charges:
U = ϕ1q2 =
ϕ2q1 = q1q2/εrε = 1 vacuum
ε ≈ 3 protein
ε ≈ 80 water
Protein/water interface
In non-uniform media: εeff = ?
At atomic distances: εeff = ?
Слайд 13
Water => PROTEIN
(ε≈3)
R ≈ 1.5 - 2 Å
ΔU
≈ +30 - 40 kcal/molCHARGE inside PROTEIN:
VERY BAD
CHARGE
inside
PROTEIN
Water => vacuum:
ΔU ≈ +100 kcal/mol
Слайд 19
Good estimate for
non-uniform media
+ -+ - +
–
+ – + –
εeff ≈ 150 !!
εeff≈40
ϕ = q/rεeff
in positions: -
- -
-
Слайд 21 Large distance:
Atomic distance:
εeff = ε =
80 εeff = ?intermediate
“vacuum”, ε ~ 1?
but the absence
of intermediate
dipoles can
only increase
interaction…
Слайд 22
At atomic distances in water:
1)
ε=80 is not a bad approximation (much better than
ε = 1 or 3 !!)(salt does not dissolve, if ε<50 at 3Å!)
[H]1/2=10-1.75 [H]1/2=10-4.25=10-1.75 × e-ΔGel/RT
ε ≈ 30-40 at ≈ 2.5Å!
ΔGel = 2.5 × ln(10) × RT ≈ 6RT ≈ 3.5 kcal/mol at ≈2.5Å
Слайд 25
Dipole interactions
(e.g., H-bonds):
(HO)-1/3-H+1/3::::::(OH)-1/3-H+1/3
Quadruple interactions
Also: charge-dipole, dipole-quadruple, etc.
Potentials:
ϕdipole ~ 1/εr2
ϕquadruple ~ 1/εr3Слайд 26 Electrostatic interactions also occur between charge (q) and
non-charged body, if its ε2 differs from the media’s
ε1:U ~ q • [1/ε2 – 1/ε1] • [ε2 /(ε1+ε2 /2)] • V • (1/r 4) at large r
In water: repulsion of charges from non-polar molecules (since here ε1>>ε2);
in vacuum (where ε1<ε2) : just the opposite!
+
+
+
-
-
-
ε2
V
ε1
Слайд 27
Debye-Hückel screening
of electrostatic by ions:
U = [q1q2/εr]•exp(-r/D)
;
in water: D = 3Å•I-1/2; Ionic strength I = ½ΣiCi(Ziion)2 .
Usually: I ≈ 0.1 [mol/liter]; D ≈ 8Å.
Electrostatics is an example of a multi-body
(charge1, charge2, media, ions) interaction
Слайд 28
Electrostatics is T- dependent;
U = (1/ε)•(q1q2/r)
is free energy
(U = H-TS);
TS = T•(-dU/dT) = -T• [d(1/ε)/dT]•(q1q2/r) =
= [dln(ε)/dlnT]•U
in water: when T grows from 273o to 293oK (by 7%),
ε decreases from 88 to 80 (by 10%):
-TS ≈ 1.3 U; H ≈ -0.3 U
In water the entropic term (-TS) is the main
for electrostatics!
