Slide 1 :Graduate Seminar
Bhabani Shankar Mallik
Y3107065 Dynamics of Hydrogen bonds in
aqueous Solutions
Slide 2 :Complexity and anomalous properties of water
Hydrogen bonds play a critical role in determining macroscopic properties of water and aqueous solution
Anomalous behavior and dynamical structure of water in aqueous solutions are not fully understood
Importance of the dynamics of hydrogen bond in chemical and biological processes.
Outline Of the Seminar: :Outline Of the Seminar: Experimental methods
Theoretical Studies
Conclusions
Experimental Methods: :Experimental Methods: Low frequency Raman ( < 200 cm-1)
Time Resolved Infrared Spectroscopy
Transient Hole burning
Slide 5 :High-frequency Raman Spectral region gives information about the intramolecular motion of water.
Relaxation and intermolecular vibrational modes of water due to H-bond network lies in low frequency Raman region.
Low-frequency Raman Spectral region gives information about the intermolecular motion of hydrogen bonding. Why Low frequency Raman studies ?
Slide 6 :Temp dependence of Raman spectra are measured in the low frequency region.
The spectral intensity is reduced into imaginary part of the dynamical susceptibility. Low frequency Raman studies : Cole-Cole relaxation with relaxation time() Damped oscillators with frequencies
2 and 3 2 Bending like mode frequency
3 Stretching like mode frequency
Low frequency Raman Spectra of Water :Low frequency Raman Spectra of Water Ujike and Tominaga, J. Chem. Phys, 110, 1558 (1999) Three maxima
Fluctuation of tetrahedrally coordinated pentamers
B and S band are from damped modes of vibration
B band is due to bending of hydrogen bonds (O…H-O)
S band is due to stretching of hydrogen bonds
C-Band is due to relaxation C-band – < 10 cm-1
B-band – 50 cm-1
S-band – 180 cm-1
Low frequency Raman Spectra of aqueous alkali halide solution :Low frequency Raman Spectra of aqueous alkali halide solution Ujike and Tominaga, J. Chem. Phys, 110, 1558 (1999) A B C
Slide 9 :Ujike and Tominaga, J. Chem. Phys, 110, 1558 (1999) S(180 cm-1) band broadens and weakens with
increasing temp.
Peak frequency of the relaxation modes in aqueous
solution with high concentration are higher than the
water at low temperature.
Drastic change of Relaxation mode with temperature.
Above room temp it overlaps with the 50cm-1 band.
Variation of n2 and n3 with ion concentration and temperature :Variation of n2 and n3 with ion concentration and temperature Ujike and Tominaga, J. Chem. Phys, 110, 1558 (1999)
Variation of n2 and n3 :Variation of n2 and n3 Bending mode n2 is almost constant with increase in temperature
n2 shifts to lower frequency with increasing concentration
Stretching mode n3 decreases with increasing temperature
n3 shifts to lower frequency with increasing concentration
Variation of relaxation time() with ion concentration and temperature :Variation of relaxation time() with ion concentration and temperature Relaxation time() is around 0.5 - 0.7 ps for pure water Ujike and Tominaga, J. Chem. Phys, 110, 1558 (1999) becomes longer with
decreasing temperature
increases with
increasing concentration
Transient hole burning :Transient hole burning Direct observation of temporarily varying molecular geometry
Observation of temporarily varying H-bond length
Life time of a vibrationally excited state
Spectral diffusion ( Hydrogen bond dynamics)
Rotational dynamics Experiments performed on OH stretch of dilute HOD
in liquid D2O
OH stretch is spectrally distinct
HOD molecules are dilute so as to avoid resonant
vibration-vibration energy transfer.
Transient hole burning studies using IR laser :Transient hole burning studies using IR laser W. Mikenda, J. Mol. Struct. 147, 1 (1986)
G.M. Gale et al, Phys. Rev. Lett, 82, 1068 (1999)
S. Woutersen and H. J. Bakker, Phys. Rev. Lett., 83, 2077 (1999)
Pump-probe signal at different delay times :Pump-probe signal at different delay times Variation of H-bond
distance with time
Frequency correlation function & Hydrogen bond dynamics :Frequency correlation function & Hydrogen bond dynamics Extract frequency time correlation function
C(t) = <(t)(0)>
from experimental data.
<(t)(0)> ~ ~ e – t/
The time scale at which O-H…Y
H-Bond distance changes.
Time scale of HB dynamics ~ 0.5 ps H-bond is believed to be the key factor in changing frequency of the donating bond
Hydrogen bond dynamics in aqueous alkali halide solutions :Hydrogen bond dynamics in aqueous alkali halide solutions Kropman and Bakker
Science, 291, 2118 (2001) ω0 T1
O-H…O 3420 0.8±0.1 ps 0.5±0.2 ps
O-H..Cl-1 3440 2.6±0.2 ps 12±3 ps
O-H…Br-1 3470 3.0±0.2 ps 25±5 ps
Rotational relaxation of water molecules in solvation shells of anions :Rotational relaxation of water molecules in solvation shells of anions Kropman and co-workers, Phys. Rev. Lett. 88, 077601 (2002) Bulk water: orientational relaxation time ~ 2.6 ps
In solvation shell of Cl- ion: 9 ps, Br- ion: 12 ps
Rotation of the entire solvation shell.
(Idea of rigid solvation shell)
Theoretical Studies :Theoretical Studies Computer Simulations combined with analytical theories
Classical Molecular Dynamics :Classical Molecular Dynamics Approximate:
Models of Water : :Models of Water : ST2 4 sites
F.H. Stillinger and A. Rahman, J. Chem. Phys., 60,1545(1974)
SPC 3 sites
H.J.C. Berendsen and Co-workers, in Intermolecular Forces, ed. B. Pullman, Reidel, Dordrecht,p-331(1981)
SPC/E 3 sites
H.J.C. Berendsen and Co-workers, J. Phys. Chem., 91, 6269(1987)
TIP3P 3 sites
W.L. jorgensen and Co-workers, J. Chem. Phys., 79, 926(1983)
TIP4P 4 sites
W.L. jorgensen and Co-workers, J. Chem. Phys., 79, 926(1983)
COS/G 4 sites
W.F. van Gunsteren and Co-workers, J. Chem. Phys. 118, 221(2003)
Definition of a Water-Water Hydrogen Bond :Definition of a Water-Water Hydrogen Bond Geometric:
ROO R1 , ROH R2 , c
Cut-off values:
Values of R1= 3.5A0 and
R2= 2.45A0 are determined from O-O and O-H radial distribution functions. c is usually taken to be around
300- 450
Anion-Water Hydrogen bonds: :Anion-Water Hydrogen bonds: Geometric:
ROi R1 , RHi R2 , c
Cut-off values:
Values of R1 and R2 are determined from O-ion and
H-ion radial distribution functions.
Slide 24 :Hydrogen bond variables
h(t) = 1, If two molecules are H bonded at time t
= 0, Otherwise
H(t) = 1, If two molecules remain continuously
H-bonded from t=0 to time t
= 0, Otherwise Hydrogen Bond Dynamics:
Hydrogen-bond correlation functions :Hydrogen-bond correlation functions Fluctuation of Hydrogen bond parameters with time
SHB(t) = Continuous Hydrogen-bond correlation function
Describes the probability that an initially hydrogen-bonded pair remains bonded at all times up to t.
CHB(t) = Intermittent Hydrogen-bond correlation function
Describes the probability that a hydrogen bond is intact at time t (Given that it was intact at t=0) D.C. Rapaport, Mol. Phys. 50, 1151 (1983)
Slide 26 :Hydrogen bond time correlation functions: < ….. > =average over all pairs D.C. Rapaport, Mol. Phys. 50, 1151 (1983) Relaxation time of this
function gives average
lifetime of a Hydrogen Bond Shows dynamics of
hydrogen bond structural
relaxation
Rate Const approach of Hydrogen Bond Dynamics :Rate Const approach of Hydrogen Bond Dynamics n(t)= The conditional probability that a HB,
which was intact at t=0, is broken at time t
but the donor/acceptor partners
are still close enough to form HB again.
Inverse of k(t) corresponds to the
average lifetime of a hydrogen bond Alenka Luzar and David Chandler, Nature, 379, 53 (1996)
Phys. Rev. Lett, 76, 928 (1996)
Dynamics of Hydrogen-bonds in pure water :Dynamics of Hydrogen-bonds in pure water A. Chandra, Phys. Rev. Lett, 85, 768 (2000) Continuous H-Bond Correlation function Life time=0.54 ps Structural Relaxation time=6.58 ps Intermittent H-Bond Correlation function
Dynamics of Hydrogen-bonds in Aqueous solution :Dynamics of Hydrogen-bonds in Aqueous solution A. Chandra, Phys. Rev. Lett, 85, 768 (2000)
J. Phys. Chem. B, 107, 3899 (2003) NaCl Solution
Conc Lifetime Diff. Coff.(D)
in ps (Dx10-5 cm2 s-1)
0.0M 0.54 2.75
0.88M 0.53 2.48
2.20M 0.52 2.06
3.35M 0.50 1.70 Decay of continuous H-Bond
Correlation function
Structural relaxation of water-water H-bonds in aqueous solution :Structural relaxation of water-water H-bonds in aqueous solution Water-Water H-bonds in solution are slower than
water-water H-bonds in pure water NaCl Solution
Conc Relaxation times (ps)
0.0M 6.58
0.88M 6.62
2.20M 6.74
3.35M 6.92 Decay of Intermittent H-Bond
Correlation function
Slide 31 :Dynamics of anion-water and water-water hydrogen bonds A. Chandra, J. Phys. Chem. B, 107, 3899 (2003) Decay of continuous H-Bond
Correlation function
Structural relaxation of anion-water & water-water H-bonds :Structural relaxation of anion-water & water-water H-bonds Anion-water H-bonds are slower than water-water
H-bonds by about a factor of 2. Decay of Intermittent H-Bond
Correlation function
Rate constant approach of hydrogen-bond dynamics :Rate constant approach of hydrogen-bond dynamics Rate const of breaking= 0.7 ps-1
Rate const of reforming=1.0 ps-1 Alenka Luzar and David Chandler, Nature, 379, 53 (1996)
Phys. Rev. Lett, 76, 928 (1996)
Hydrogen-bond Dynamics near Polypeptide :Hydrogen-bond Dynamics near Polypeptide Different Environments for Water molecules
Various Hydrogen-Bond classes of water pairs:
0. In bulk
I. In solvation shell of carbon of hydrophobic
surface
II. In the solvation shell of oxygen or nitrogen
atom Huafeng Xu and B.J. Berne, J. Phys. Chem B, 105, 11929 (2001) Last 16 residues to the C-terminus of the immunoglobulin binding protein G
Hydrophobic surface is created by Trp43, Tyr45, Phe52, Val54
Structural relaxation of water-water H-bonds near Polypeptide :Structural relaxation of water-water H-bonds near Polypeptide Huafeng Xu and B.J. Berne, J. Phys. Chem B, 105, 11929 (2001) Slower decay around other solutes as compared to water Env Relax() Lifetime(HB)
0…0 3.2 0.26
0…I 5.0 0.27
0…II 5.4 0.27
I…I 6.8 0.31
Hydrogen-Bond dynamics near Oligopeptide :Hydrogen-Bond dynamics near Oligopeptide Different Environments for Water molecules near peptide chain [GVG(VPGVG)n]
Various Hydrogen-Bond classes :
BB – Between water molecules in the bulk.
SC – Two water molecules both located in the
first solvation of peptide side chains.
PS – peptide and water in the first solvation
shell. Dominik Marx and Co-workers,Phys. Rev. Lett., 92, 148101 (2004)
Rate constants for Hydrogen-Bond breaking and reforming :Rate constants for Hydrogen-Bond breaking and reforming Activation Energies(KJ/mol)
Breaking(k) Reforming(k’)
BB 8.0 5.0
SC 9.0
PS 13.0 11.0 (<320K)
4.0 (>330K) Dominik Marx and Co-workers,Phys. Rev. Lett., 92, 148101 (2004)
Conclusions :Conclusions The dynamics of breaking and the structural relaxation of anion-water hydrogen bonds in aqueous solution are slower than the water-water hydrogen bonds in water.
The dynamics of Hydrogen bonds are found to be slower near bio-molecules surfaces.
This is due to slow orientational and translational motion of water near charged solutes.
Slide 39 :Thank You....