Hydration Number of Biomolecules Evaluated with

21世紀COE外国旅費補助・出張報告会
（2006年6月12日）
Hydration Number of Biomolecules
Evaluated with THz Time-Domain
Attenuated Total Reflection Spectroscopy
物理学第一教室光物性研究室D1
有川敬
会議名称：CLEO/QELS and PhAST 2006
開催期間：2006年5月21～26日
開催場所：アメリカ、カリフォルニア州、ロングビーチ
1. CLEO/QELS and PhASTについて
2. 分野の説明
3. 発表内容、成果
CLEO/QELS and PhASTについて
•３つの会議の合同開催（昨年の参加者5281人）
CLEO : レーザー、電気光学
QELS : 量子エレクトロニクス、レーザーサイエンス
PhAST : 光技術応用
•CLEO Topics
•固体レーザー、半導体レーザー
•ＬＥＤ、有機ＬＥＤ
•ファイバーレーザー、増幅器
•非線形光学応用
•高強度レーザー、物理
•超高速光学、電気光学、応用
•テラヘルツ技術、応用
•薬学、生物学応用
•光通信、ネットワーク
•レーザー加工
•光センシング、計測
など
分野の説明（テラヘルツ電磁波とは）
•テラヘルツ電磁波（1テラ＝1012）は、ミリ波と赤外線の中間の周波数帯に位置する電磁波。
•この周波数領域には様々な物理現象が見られます。
配向緩和
300MHz 3GHz
1m
100mm
電波
プラズマ振動
30GHz
10mm
マイクロ波
分子間振動
300GHz 3THz
1m
100mm
遠赤外
分子内振動
30THz
10mm
300THz
1mm
電子遷移
3PHz
100nm
中赤外近赤外
紫外
X線回折
10nm
1nm
X線
可視光
電波
THz領域
光
0.1nm
g線
テラヘルツ領域の物理現象
●孤立した分子（気体）
－回転準位
●巨大分子
－分子間振動モード（有機分子）
－生体機能に関係する集団運動（生体高分子）
●固体
－フォノン振動
－強誘電ソフトモード（誘電体）
－電子集団励起（半導体）
－超伝導ギャップ（超伝導体）
●液体
－水素結合ネットワーク（水）
－水和（水溶液）
テラヘルツ電磁波を用いた研究例①
Build-up of collective behavior in an electron-hole plasma in GaAs
Nature Vol. 414 (2001)
テラヘルツ電磁波を用いた研究例②
違法薬物、危険物の透視
60
50
40
30
20
10
0
0 10 20 30 40 50 60 mm
Ｘ線と補完的なイメージング光源
本研究の対象
●孤立した分子（気体）
－回転準位
●巨大分子
－分子間振動モード（有機分子）
－生体機能に関係する集団運動（生体高分子）
●固体
－フォノン振動
－強誘電ソフトモード（誘電体）
－電子集団励起（半導体）
－超伝導ギャップ（超伝導体）
●液体
－水素結合ネットワーク（水）
－水和（水溶液）
水和水
生体分子
バルク水
Hydration Number of Biomolecules
Evaluated with THz Time-Domain
Attenuated Total Reflection Spectroscopy
Takashi Arikawa*, Masaya Nagai, Koichiro Tanaka
Department of Physics, Kyoto University, Japan
*JSPS Research Fellow
CLEO/QELS ’06 Long beach, California, USA (May 21-26, 2006)
Background of this study
Bulk water
~ps
Hydrated
H2O
water
•Protein folding
•Expression of biological function
What is the role of water?
10ms ~ ns
Biomolecule
H2O
Interaction between
biomolecule and water
Hydrated water
↑Hydration model of biomolecule1
One indicator of the strength
of interaction between
biomolecule and water
[1] H. S. Frank and Wen –Y. Wen, Disc. Faraday Soc., 24, 133 (1957)
Hydration of Sucrose(C12H22O11)
Method
Hydration Number Time Scale
Calorimetric Measurement1
6.33
~100s
Ultrasound Measurement2
13.8
~10-6s
MD calc3
20.8
Discrepancy
Bulk Water
Whole number of
hydrated water molecules
Solute
=
Polarizability (Im)
Reason: Different time scales of the
experimental perturbation methods
Decrement of bulk water molecules
Hydrated Water
MHz
Ultrasound
GHz
THz
[1] H. Kawai et al., Cryobiology 29, 599 (1992)
[2] C. Branca et al., J. Phys. Chem. B 105, 10140 (2001)
[3] A. Lerbret et al., J. Phys. Chem. B, 109, 11046 (2005)
Purpose of This Study
❑Evaluate the whole hydration number of biomolecules
from THz dielectric properties of water solution.
Solute Molecule
(molecular formula )
Disaccharide
Method : THz Time-domain Attenuated
Total Reflection Spectroscopy1
Sucrose
(C12H22O11)
Trehalose
(C12H22O11)
Amino acid
Alanine
（C3H7O2N）
Arginine
(C6H14O2N4)
THz wave
Dove Prism
(MgO)
[1] H. Hirori et al., Opt. Express 13, 10801 (2005)
K. Tanaka CLEO/IQEC 06, CMCC1
Dielectric Constant of Sucrose Solution
Characteristics of dielectric
response in water solution
6
Dielectric Constant
4
2
Crystal
r
Molecule
Molecule
•A solution with higher
concentration has smaller
absorption (i)
0
Water
0.149 mol/l
0.305 mol/l
0.633 mol/l
0.989 mol/l
6
4
2
0
0.0
i
→ Decrease of bulk water
& Increase of hydrated water
•No dispersion around 1.45 THz
Crystal
0.5
•High frequency tail of debye
relaxation of bulk water
→ Sucrose is surrounded by
hydrated water
1.0
Frequency [THz]
1.5
10
12
Binary Mixture Model
(Onsager’s Local Field theory)
(
Pw  Ps )
P
~
 1 

0E
0E
~

Ps
H2O
H2O
H2O
Sucrose
Pw
H2O
H2O
H2O
H2O
H2O


Pi  N i i F
Ni : Number density
i : Polarizability
F : Local field
Approximate calculation of local field
●Lorentz field
 ~ ~  2 
F ( ) 
E
3
E
●Onsager’s theory1 Considering the effect
of permanent dipole
 ~
F ( ) 


r a3
g~ (~ )
m ~ ~  3 E

3
1  r a
1  r ( ) a
[1] N. E. Hill “Dielectric Properties and
Molecular Behaviour”
Polarizability [10
4
Real Part
Different value of polarizability
depending on the concentration
Sucrose
2
Physically inconsistent
0
Reason : Hydration effect
is not considered
-2
0
Imaginary Part
-2
0.149 mol/l
0.305 mol/l
0.633 mol/l
0.989 mol/l
-4
-6
-8
0.0
0.5
1.0
12
Frequency
[10[THz]
Hz]
Frequency
1.5
Polarizability (Im)
2 -1
Cm-12V ] 2
-1 2
10
-12
-1 2
10
Orientational Polarizability [10 Cm V-1]
Orientational Polarizability of Sucrose
Bulk water
Solute
Hydrated water
MHz
GHz
THz
Modified Binary Mixture Model
Bulk water
H2O
H2O
H2O
H2O
H2O
Assumption
H2O
Sucrose
H2O
H2O
H2O
H2O
H2O
H2O
Volume of hydrated sucrose
‫װ‬
Volume of sucrose
Hydrated water : set orientational polarizability to zero
Solution =
Hydrated sucrose
(Sucrose & nH hydrated water molecules)
+
Bulk water
(a)Real Part
2
0
-1 2
10
-2
2
Orientational Polarizability [10-12Cm2V-1]
4
-12
10
-1 2
2 -1
Polarizability
V -12
] Cm2V-1]
[10 Cm[10
Polarizability
Orientational
Determination of
Hydration Number & Polarizability
Sucrose
•Hydration number is 19.3
(MD calculation : 20.8)
•Orientational polarizability is zero
(b)Imaginary Part
= 19
nnHH=19.3
0
-2
-4
0.0
0.5
1.0
1.5
Frequency [THz]
10
12
Hydration Number
Molecule
Sucrose
(C12H22O11)
Disaccharide
Trehalose
(C12H22O11)
Alanine
（C3H7O2N）
Amino acid
Arginine
(C6H14O2N4)
H2 O
D2O
Alanine
Sucrose
19.3±0.2 24.7±0.1
(20.81)
20.6±0.1 26.35±0.1
Arginine
1
Trehalose
(22.9 )
5.47±0.01 6.99±0.01
(3.482)
14.0±0.1 17.9±0.1
[1] (MD calculation)
A. Lerbret et al., J. Phys. Chem. B 109, 11046 (2005)
[2] (Monte Carlo method) T. K. Kim et al., J. Mol. Liquids 59, 179 (1994)
D2O/H2O
1.28
1.28
1.28OH
OH
HOH2C
o
1.28
OH
10
-1 3
-12
10
-1 3
2 -1
Polarizability
V -12] Cm2V-1]
[10 Cm
[10
Polarizability
Orientational
Determining Condition of hydration number
0.44
0.33
0.22
Zero-Polarizability condition
(a) Real Part
(Onsager’s Model)
H2O
Sucrose +
water
numberHydrated
is determined
Hydration
0.11
so that the vector sum of
0
permanent
dipoles of solute and
(b) Imaginary Part
0.33
hydrated
water becomes zero
nH

m s   m w,i

0
i

ms
0.22
0.11
0
0.0

Solute
0.5
1.0

mw
1.5
Frequency [THz]
10
12
*J. Higo et al., Proc. Natl. Acad. Sci. U.S.A. 98 (11) 5961 (2001 )
Formula for Hydration Number
and Isotope Effect
Volume of a solute molecule
High frequency polarizability
of solute and water
a
  nH 

2( s  1) (2 s  1)
4 0
3
s

s
Static dielectric constant of Solution
 w,D2O   w,H 2O 1.28
nH , D 2O  1.28  nH , H 2O

w
Summary
Hydration of biologically-relevant molecules studied
by THz TD-ATR spectroscopy
1. Hydration number is determined so that the vector sum of permanent
dipoles of solute and hydrated water becomes zero.
2. Hydration number is determined by static dielectric constant of
solution s, volume of a solute a3, and high frequency polarizability of
solute and solvent s(w).
3. Evaluated hydration numbers are in good agreement with MD
calculation results (in the case of disaccharides).
発表成果
•テラヘルツ電磁波を水溶液中の生体分子の水和の研究に用いた研究例は他にはない
•大きな会議で、多くの聴衆の前で、内容的にインパクトのある講演ができたと思う

Download Report