Proteins, molecules, and macromolecular assemblies in water are surrounded by a nanometer-sized hydration layer with properties very different from bulk water. Here, we use classical molecular dynamics simulations to study the dielectric response of hydration water next to hydrophobic and hydrophilic planar surfaces. We find the interfacial dielectric absorption of water to be strongly anisotropic: compared to bulk water, which shows a broad dielectric absorption maximum around 15 GHz in the imaginary part of the dielectric function, the absorption for electric fields parallel to the surface is of similar strength and shows a slight redshift, while for perpendicular electric fields it is strongly attenuated and blueshifted. This anisotropy is generic for hydrophobic and hydrophilic surfaces. From our spatially resolved dielectric functions and a modified Maxwell-Garnett theory that accounts for anisotropic hydration layers around spherical particles, the dielectric absorption of solutions of organic molecules and micelles is derived to exhibit the experimentally known attenuation in combination with a redshift. These two features are traced back to the subtle interplay of interfacial depolarization effects and the dielectric anisotropy in the hydration layer. By a detailed analysis of the individual water molecule dynamics the perpendicular blueshift is shown not to be linked to accelerated water reorientation, but rather to dielectric boundary effects. Carefully conducted angularly resolved experiments at planar aqueous interfaces will be able to resolve this dielectric anisotropy and thus to confirm the subtle connection between spectral absorption features and the molecular water dynamics in hydration layers.
REFERENCES
1.
B.
Bagchi
, “Water dynamics in the hydration layer around proteins and micelles
,” Chem. Rev.
105
, 3197
(2005
).2.
R.
Buchner
and G.
Hefter
, “Interactions and dynamics in electrolyte solutions by dielectric spectroscopy
,” Phys. Chem. Chem. Phys.
11
, 8984
–8999
(2009
).3.
B.
Born
, H.
Weingärtner
, E.
Bründermann
, and M.
Havenith
, “Solvation dynamics of model peptides probed by terahertz spectroscopy: Observation of the onset of collective network motions
,” J. Am. Chem. Soc
131
, 3752
(2009
).4.
K. J.
Tielrooij
, D.
Paparo
, L.
Piatkowski
, H. J.
Bakker
, and M.
Bonn
, “Dielectric relaxation dynamics of water in model membranes probed by terahertz spectroscopy
,” Biophys. J.
97
, 2484
–2492
(2009
).5.
U.
Kaatze
, “Bound water: Evidence from and implications for the dielectric properties of aqueous solutions
,” J. Mol. Liq.
162
, 105
(2011
).6.
T.
Fukasawa
, T.
Sato
, J.
Watanabe
, Y.
Hama
, W.
Kunz
, and R.
Buchner
, “Relation between dielectric and low-frequency Raman spectra for hydrogen-bond liquids
,” Phys. Rev. Lett.
95
, 197802
(2005
).7.
I. R.
Piletic
, D. E.
Moilanen
, D. B.
Spry
, N. E.
Levinger
, and M. D.
Fayer
, “Testing the core/shell model of nanoconfined water in reverse micelles using linear and nonlinear IR spectroscopy
,” J. Phys. Chem. A
110
, 4985
–4999
(2006
).8.
J.
Qvist
and B.
Halle
, “Thermal signature of hydrophobic hydration dynamics
,” J. Am. Chem. Soc.
130
, 10345
–10353
(2008
).9.
A. A.
Bakulin
, M. S.
Pshenichnikov
, H. J.
Bakker
, and C.
Petersen
, “Hydrophobic molecules slow down the hydrogen-bond dynamics of water
,” J. Phys. Chem. A
115
, 1821
(2011
).10.
R.
Abseher
, H.
Schreiber
, and O.
Steinhauser
, “The influence of a protein on water dynamics in its vicinity investigated by molecular dynamics simulation
,” Proteins
25
, 366
–378
(1996
).11.
R.
Iftimie
and M. E.
Tuckerman
, “Decomposing total IR spectra of aqueous systems into solute and solvent contributions: A computational approach using maximally localized Wannier orbitals
,” J. Chem. Phys.
122
, 214508
(2005
).12.
M.
Heyden
, J.
Sun
, S.
Funkner
, G.
Mathias
, H.
Forbert
, M.
Havenith
, and D.
Marx
, “Dissecting the THz spectrum of liquid water from first principles via correlations in time and space
,” Proc. Natl. Acad. Sci. U.S.A.
107
, 12068
(2010
).13.
M.
Heyden
and M.
Havenith
, “Combining THz spectroscopy and MD simulations to study protein-hydration coupling
,” Methods
52
, 74
(2010
).14.
T.
Yamaguchi
, H.
Furuhashi
, T.
Matsuoka
, and S.
Koda
, “Dynamic solvophobic effects and its cooperativity in the hydrogen-bonding liquids studied by dielectric and nuclear magnetic resonance relaxation
,” J. Phys. Chem. B
112
, 16633
–16641
(2008
).15.
K. J.
Tielrooij
, J.
Hunger
, R.
Buchner
, M.
Bonn
, and H. J.
Bakker
, “Influence of concentration and temperature on the dynamics of water in the hydrophobic hydration shell of tetramethylurea
,” J. Am. Chem. Soc.
132
, 15671
–15678
(2010
).16.
R. K.
Murarka
and T.
Head-Gordon
, “Dielectric relaxation of aqueous solutions of hydrophilic versus amphiphilic peptides
,” J. Phys. Chem. B
112
, 179
(2008
).17.
J. C.
Rasaiah
, S.
Garde
, and G.
Hummer
, “Water in nonpolar confinement: From nanotubes to proteins and beyond
,” Annu. Rev. Phys. Chem.
59
, 713
(2008
).18.
J.
Li
, J. M.
Fernandez
, and B. J.
Berne
, “Waters role in the force-induced unfolding of ubiquitin
,” Proc. Natl. Acad. Sci. U.S.A.
107
, 19284
(2010
).19.
R.
Baron
, P.
Setny
, and J. A.
McCammon
, “Water in cavity-ligand recognition
,” J. Am. Chem. Soc.
132
, 12091
(2010
).20.
D.
Thirumalai
, G.
Reddy
, and J. E.
Straub
, “Role of water in protein aggregation and amyloid polymorphism
,” Acc. Chem. Res.
45
, 83
(2012
).21.
D.
Laage
, G.
Stirnemann
, and J. T.
Hynes
, “Why water reorientation slows without iceberg formation around hydrophoic solutes
,” J. Phys. Chem. B
113
, 2428
(2009
).22.
A.
Chandra
and B.
Bagchi
, “Microscopic expression for frequency and wave vector dependent dielectric constant of a dipolar fluid
,” J. Chem. Phys.
90
, 1832
(1988
).23.
F. O.
Raineri
, B.-C.
Perng
, and H. L.
Friedman
, “A fluctuating charge density formulation of the dielectric behavior of liquids – with applications to equilibrium and nonequilibrium solvation
,” Electrochim. Acta
42
, 2749
(1997
).24.
P. A.
Bopp
, A. A.
Kornyshev
, and G.
Suttman
, “Freqency and wave-vector dependent dielectric function of water: Collective modes and relaxation spectra
,” J. Chem. Phys.
109
, 1939
(1998
).25.
S.
Schrödle
, G.
Hefter
, W.
Kunz
, and R.
Buchner
, “Effects of nonionic surfactant C12E5 on the cooperative dynamics of water
,” Langmuir
22
, 924
(2006
).26.
B.
Klösgen
, C.
Reichle
, S.
Kohlsmann
, and K. D.
Kramer
, “Dielectric spectroscopy as a sensor of membrane headgroup mobility
,” Biophys. J.
71
, 3251
(1996
).27.
P. B.
Petersen
and R. J.
Saykally
, “Probing the interfacial structure of aqueous electrolytes with femtosecond second harmonic generation spectroscopy
,” J. Phys. Chem. B
110
, 14060
(2006
).28.
Y.
Rao
, D.
Song
, N. J.
Turro
, and K. B.
Eisenthal
, “Orientational motions of vibrational chromophores in molecules at the air/water interface with time-resolved sum frequency generation
,” J. Phys. Chem. B
112
, 13572
(2008
).29.
M.
Sajadi
, Y.
Ajaj
, I.
Ioffe
, H.
Weingärtner
, and N. P.
Ernsting
, “Terahertz absorption spectroscopy of a liquid using a polarity probe: A case study of trehalose/water mixtures
,” Angew. Chem., Int. Ed.
49
, 454
(2010
).30.
C.
Sendner
, D.
Horinek
, L.
Bocquet
, and R. R.
Netz
, “Interfacial water at hydrophobic and hydrophilic surfaces: Slip, viscosity and diffusion
,” Langmuir
25
, 10768
(2009
).31.
F.
Sedlmeier
, Y.
von Hansen
, L.
Mengyu
, D.
Horinek
, and R. R.
Netz
, “Water dynamics at interfaces and solutes: Disentangling free energy and diffusivity contributions
,” J. Stat. Phys.
145
, 240
–252
(2011
).32.
H. J. C.
Berendsen
, J. R.
Grigera
, and T. P.
Straatsma
, “The missing term in effective pair potentials
,” J. Phys. Chem.
91
, 6269
(1987
).33.
M.
Neumann
, “Dielectric relaxation in water: Computer simulations with the TIP4P potential
,” J. Chem. Phys.
85
, 1567
(1986
).34.
D.
van der Spoel
, E.
Lindahl
, B.
Hess
, G.
Groenhof
, A. E.
Mark
, and H. J. C.
Berendsen
, “GROMACS: Fast, flexible, and free
,” J. Comput. Chem.
26
, 1701
(2005
).35.
S.
Plimpton
, “Fast parallel algorithms for short-range molecular dynamics
,” J. Comput. Phys.
117
, 1
–17
(1995
).36.
H. J. C.
Berendsen
, J. P. M.
Postma
, W. F.
van Gunsteren
, A.
DiNola
, and J. R.
Haak
, “Molecular dynamics with coupling to an external bath
,” J. Chem. Phys.
81
, 3684
(1984
).37.
I.
Yeh
and M. L.
Berkowitz
, “Ewald summation for systems with slab geometry
,” J. Chem. Phys.
111
, 3155
–3162
(1999
).38.
C. J. F.
Böttcher
and P.
Bordewijk
, Theory of Electric Polarization II
(Elsevier Scientific
, 1978
).39.
H. A.
Stern
and S. E.
Feller
, “Calculation of the dielectric permittivity profile for a nonuniform system: Application to a lipid bilayer system
,” J. Chem. Phys.
118
, 3401
(2003
).40.
D. J.
Bonthuis
, S.
Gekle
, and R. R.
Netz
, “Dielectric profile of interfacial water and its effect on double layer capacitance
,” Phys. Rev. Lett.
107
, 166102
(2011
).41.
D. J.
Bonthuis
, S.
Gekle
, and R. R.
Netz
, “Profile of the static permittivity tensor of water at interfaces: Consequences for capacitance, hydration interaction and ion adsorption
,” Langmuir
28
, 7679
–7694
(2012
).42.
V. A.
Froltsov
and S. H. L.
Klapp
, “Dielectric response of polar fluids in narrow slit pores
,” J. Chem. Phys.
126
, 114703
(2007
).43.
See supplementary material at http://dx.doi.org/10.1063/1.4749380 for additional data.
44.
M. R.
Reddy
and M.
Berkowitz
, “The dielectric constant of SPC/E water
,” Chem. Phys. Lett.
155
, 173
(1989
).45.
46.
T.
Hanai
and K.
Sekine
, “Theory of dielectric relaxations due to the interfacial polarization for two-component suspensions of spheres
,” Colloid Polym. Sci.
264
, 888
(1986
).47.
J. E. W.
Castner
, G. R.
Fleming
, B.
Bagchi
, and M.
Maroncelli
, “The dynamics of polar solvation: Inhomogenepous dielectric continuum models
,” J. Chem. Phys.
89
, 3519
(1988
).48.
The core radius is obtained from
$4/3\pi R_c^3=V_p$
with the particle volume given by Vp = Mp/ρ where the density ρ = 0.968 g/cm3 for pure TMU and the particle mass in turn is calculated from Mp = M/NA with the molar mass of TMU M = 116.16 g/mol and NA Avogadro's constant.49.
O.
Glatter
, G.
Fritz
, H.
Lindner
, J.
Brunner-Popela
, R.
Mittelbach
, R.
Strey
, and S. U.
Egelhaaf
, “Nonionic micelles near the critical point: micellar growth and attractive interaction
,” Langmuir
16
, 8692
(2000
).50.
M.
Maroncelli
and G. R.
Fleming
, “Computer simulation of the dynamics of aqueous solvation
,” J. Chem. Phys.
89
, 5044
(1988
).51.
G.
Stirnemann
, S. R.-V.
Castrillón
, J. T.
Hynes
, P. J.
Rossky
, P. G.
Debenedetti
, and D.
Laage
, “Non-monotonic dependence of water reorientation dynamics on surface hydrophilicity: Competing effects of the hydration structure and hydrogen-bond strength
,” Phys. Chem. Chem. Phys.
13
, 19911
(2011
).52.
J. J.
Loparo
, C. J.
Fecko
, J. D.
Eaves
, S. T.
Roberts
, and A.
Tokmakoff
, “Reorientational and configurational fluctuations in water observed on molecular length scales
,” Phys. Rev. B
70
, 180201
(2004
).© 2012 American Institute of Physics.
2012
American Institute of Physics
You do not currently have access to this content.
