Hydration of Small Peptides Thomas Wyttenbach, Dengfeng Liu, and - - PowerPoint PPT Presentation
Hydration of Small Peptides Thomas Wyttenbach, Dengfeng Liu, and Michael T. Bowers http://bowers.chem.ucsb.edu/ Why study hydration? Is a certain property of a molecule (e.g. conformation) inherent to the molecule or a consequence of
Thomas Wyttenbach, Dengfeng Liu, and Michael T. Bowers http://bowers.chem.ucsb.edu/
Is a certain property of a molecule (e.g. conformation) inherent to the molecule
water (theory)3 apolar solvent (NMR)1 water:2
1 Crescenzi et al
Eur J Biochem 269, 5642 (2002)
2 Zhang et al
J Struct Biology 130, 130 (2000)
3 Baumketner, Shea
UCSB, unpublished
gas phase (theory)3
Why study hydration? Bridge gas phase and solution phase Study effect of individual water molecules
conformations, folding zwitterion formation hydration sites
NMR structure
3 6 9 m/z
2 torr H2O 286 K
(M+2H)2+ (M+3H)3+ (M+H)+
1 H2O (ELYENKPRRPYIL) 1 2
ESI Ion Source ESI Ion Source Ion Funnel Ion Funnel Drift Cell Drift Cell MS MS Detector Detector
M+ M+•(H2O)n H2O ~1 torr H2O Liquid N2 cooling Electrical heaters
3 6 9 m/z
Mass Spectra Neurotensin
2 torr H2O 286 K
(M+2H)2+ (M+3H)3+ (M+H)+
1 H2O (ELYENKPRRPYIL) 1 2
M+ M+•(H2O)n H2O ~1 torr H2O
m/z
1800 µs 900 µs 2700 µs drift time
Neurotensin (M+2H)2+ 290 K, 1.8 torr H2O
3 6 9 m/z
Mass Spectra Neurotensin
2 torr H2O 286 K
(M+2H)2+ (M+3H)3+ (M+H)+
1 H2O (ELYENKPRRPYIL) 1 2
M+ M+•(H2O)n H2O ~1 torr H2O
ratio of peak intensities equilibrium constant van’t Hoff ∆H° and ∆S°
Data Analysis Data Analysis
∆H° ∆S°
lys N-terminus arg his asp glu C-terminus
In peptides and proteins they are:
Ionic Groups The Ammonium Group The Guanidinium Group The Carboxylate Group Several Ionic Groups Multiply Charged Ions Salt Bridges Challenges Ahead Change of Conformation Zwitterion Formation Entropy
+
B3LYP/6-311++G**
second solvation shell
1 2 3 4 5 6 8 10 12 14 16 18
Experiment MM DFT Number of water molecules Water binding energy (kcal/mol)
Experiment
second solvation shell
Molecular Mechanics
AMBER, TIP3P first solvation shell
δ+ δ–
δ+
17kcal/mol
experiment1 & DFT2
15 kcal/mol
experiment2
1 Meot-Ner
JACS 1984, 106, 1265
2 Liu, Wyttenbach,
Barran, Bowers, JACS 2003, 125, 8458
δ+
M+•(H2O)n 10 3 12 2 15 1 ∆H°
kcal/mol
n
0.10 0.90 3 0.08 0.92 2 0.05 0.95 1 — 0.35 0.65 1.00 (H2O)n CH3—NH3+ n NBO charges on CH3NH3+•(H2O)n
B3LYP/6-311++G**
1 2 3 4 5
Experiment MM DFT Number of water molecules
Exp Ele
Electrostatic energy Eel
n-decylamine
=
ij j i el
r q q E
=
CH3NH3
+
(H2O)n–1 nth H2O
n–1
qi qj
etc. etc.
n–1
qi qj
etc. etc.
2 kcal/mol
1 2 3 4 5
Experiment MM DFT Number of water molecules
Exp Ele
n-decylamine
=
ij j i el
r q q E
=
CH3NH3
+
(H2O)n–1 nth H2O
Experimental water binding energy (C10H21NH3
+)
2 kcal/mol
1 2 3 4 5 6 8 10 12 14 16 18
Experiment MM DFT Number of water molecules Water binding energy (kcal/mol) DFT
methylamine
Experiment
n-decylamine
AMBER
n-decylamine
NH CH C CH2 NH O CH2 CH2 CH2 NH3 C O CH C NH O R
self-solvation
H3C C NH2 O
H3C C OH O 1.7 D
lysine
Nα-acetyl-L-lysine AMBER
AMBER
OH
Experimental binding energies (–∆H° in kcal/mol)
Nα-acetyl-
L-lysine
n-decyl- amine
NH CH C CH3 NH O CH C CH3 NH O CH C CH2 NH O CH2 CH2 CH2 NH2 CH C CH3 NH O CH C CH3 OH O C H3C O
AMBER
NH CH C CH3 NH O CH C CH3 NH O C H3C O CH C CH3 NH O CH C CH3 NH O CH C CH2 OH O CH2 CH2 CH2 NH2
charge remote AMBER
AMBER
kcal/mol experimental water binding enthalpy
kcal/mol
NH3 + NH3 +
δ– δ+
AMBER AMBER x = 8 x = 20 Jarrold JACS (1998) 120, 12974 x = 4
Experimental water binding energies (kcal/mol)
n/a n/a n/a
7 8
Ac-A20K Ac-A8K Ac-AAAAK Ac-AAKAA n-decylamine
10 12 15 ≤4
n/a n/a n/a
5
n/a n/a n/a
7
n/a n/a n/a
7 9
n/a n/a n/a
3 2 1 First solvation shell Second
solvation
shell Charge remote
10 8 8
acetyllysine
a a Estimated based on: Jarrold JACS (2002) 124, 11148
Ammonium Group
Ionic Groups The Ammonium Group The Guanidinium Group The Carboxylate Group Several Ionic Groups Multiply Charged Ions Salt Bridges Challenges Ahead Change of Conformation Zwitterion Formation Entropy
HO H N NH3 O O CH3 CH3 NH2 NH2 NH HO O NH2
(Arg–OMe + H)+
C10H21NH3
+
(Arg + H)+
(Ala-Ala + H)+
–∆H° (kcal/mol) –∆H° (kcal/mol) Guanidine Amine
Experimental water binding energies
N C N N H H H H H
AMBER
9.4 9.5 10.2 9.3 9.0
–∆H°
kcal/mol
(Ac-AAAAK + H)+ (Ac-AAKAA + H)+ (AAAAA + H)+ C10H21NH3
+
(AARAA-OMe + H)+ (Ac-AARAA + H)+
6.9
(AARAA + H)+
8.5
(RAAAA + H)+
10.5
(Arg + H)+ Exposed
14.8
–∆H°
kcal/mol
Self- solvated
Amines Guanidines
pentapeptides Experimental water binding energies
Guanidines –∆H°
kcal/mol
9.4 9.5 10.2 9.3
1st H2O
8.4 8.1 8.4 7.8
2nd H2O
7.6 7.1
3rd H2O
(AARAA-OMe + H)+ (Ac-AARAA + H)+ (AARAA + H)+ (RAAAA + H)+ Experimental water binding energies
The Ammonium Group The Guanidinium Group The Carboxylate Group Several Ionic Groups Multiply Charged Ions Salt Bridges Challenges Ahead Change of Conformation Zwitterion Formation Entropy
Carboxylate
(Ala-Ala – H)–
Ammonium
(Ala-Ala + H)+
H2N CH C CH3 N H O CH COO CH3 H3N CH C CH3 N H O CH COOH CH3
–∆H°
kcal/mol
1st H2O
1st H2O
–∆H°
kcal/mol
3rd H2O
3rd H2O
2nd H2O
2nd H2O
N CH C CH3 O O H
+ 4 H2O
AMBER
(Ala-Ala – H)–
AMBER
11.9 13.1 15.6
B3LYP/6-31G*
Calculated (B3LYP/6-31G*) water binding energy (kcal/mol)
CH C CH3 N O CH C (CH2)x N O C O O CH C CH3 O H H
x=1 aspartic acid x=2 glutamic acid
(Ala-Ala) • (Ala-Ala – H)–
AMBER
4 3 [(AA)2-H]
4 6 8 (AA–H)–•(AA)•(H2O)m
Dimer
(AA–H)–•(H2O)n
Monomer
n
319 8 3
160 180 200 220 240 260 280 300 320 340 360 380 400 420 440 460 480
m/z
1.3 Torr H2O, 260 K 〈n〉 – 〈m〉 ≅ 4 (AA–H)–•(H2O)5.2 Average: 〈n〉 = 5.2 (AA–H)–•(AA)•(H2O)1.3 Average: 〈m〉 = 1.3
AMBER
(AA–H)–
AMBER
(AA–H)–•(AA)
AMBER
(AA–H)–•(H2O)4
AMBER
Overlap of (AA–H)– conformation in (AA–H)– (AA–H)–•(H2O)4 (AA–H)–•(AA)
The Ammonium Group The Guanidinium Group The Carboxylate Group Several Ionic Groups Multiply Charged Ions Salt Bridges Challenges Ahead Change of Conformation Zwitterion Formation Entropy
4
3
2
2
1
1
kcal/mol
kcal/mol
H3N H3N NH3
CH3(CH2)9NH3+ H3N(CH2)12NH32+
Blades, Klassen, Kebarle JACS 118, 12437 (1996)
Na+ Ca2+ n 1 ~55 24
(radius 0.97 Å) (radius 0.99 Å)
Na+ Ca2+ n 1 ~55 24
(radius 0.97 Å) (radius 0.99 Å)
m/z
Hydration Mass Spectra Neurotensin
1.3 Torr H2O 260 K (ELYENKPRRPYIL) 9 6 3
820 840 860 880 900 920 940 960
12 12 H2O
560 580 600 620 640 660 680 700
15 18 9
1660 1700 1740 1780 1820
3
(M+2H)2+ (M+3H)3+ (M+H)+
6
n −∆H°n (kcal/mol) +1 +2 +3 1 9.2 10.3 (15) 2 9.8 8.9 (12) 3 (9) 9.6 9.5 4 (9) 9.4 9.3 5 8.5 9.4 6 (8) 9.8 7 (9) 8.8 8 (10) 9 (9) 10 (9)
Experimental ∆H°-values for binding nth water molecule to neurotensin (ELYENKPRRPYIL) in charge states +1, +2, and +3 ± 0.3 kcal/mol ± 1 kcal/mol for values in parenthesis 9 10 12 10 10 10 9 8 9
n −∆H°n (kcal/mol) +1 +2 +3 1 9.2 10.3 (15) 2 9.8 8.9 (12) 3 (9) 9.6 9.5 4 (9) 9.4 9.3 5 8.5 9.4 6 (8) 9.8 7 (9) 8.8 8 (10) 9 (9) 10 (9)
Experimental ∆H°-values for binding nth water molecule to neurotensin (ELYENKPRRPYIL) in charge states +1, +2, and +3 ± 0.3 kcal/mol ± 1 kcal/mol for values in parenthesis
13.6
4
13.4
3
12.1
2
15.7
2
15.7
1
14.8
1
–∆H°
kcal/mol
n –∆H°
kcal/mol
n 13.6
4
13.4
3
12.1
2
15.7
2
15.7
1
14.8
1
–∆H°
kcal/mol
n –∆H°
kcal/mol
n
CH3(CH2)9NH3+ H3N(CH2)12NH32+
Blades, Klassen, Kebarle JACS 118, 12437 (1996)
H3N NH3
H3N NH3
Degree of charge exposure Nature of charged groups
n −∆H°n (kcal/mol) +1 +2 +3 1 9.2 10.3 (15) 2 9.8 8.9 (12) 3 (9) 9.6 9.5 4 (9) 9.4 9.3 5 8.5 9.4 6 (8) 9.8 7 (9) 8.8 8 (10) 9 (9) 10 (9)
Experimental ∆H°-values for binding nth water molecule to neurotensin (ELYENKPRRPYIL) in charge states +1, +2, and +3 ± 0.3 kcal/mol ± 1 kcal/mol for values in parenthesis
Degree of charge exposure Nature of charged groups
n −∆H°n (kcal/mol) +1 +2 +3 1 9.2 10.3 (15) 2 9.8 8.9 (12) 3 (9) 9.6 9.5 4 (9) 9.4 9.3 5 8.5 9.4 6 (8) 9.8 7 (9) 8.8 8 (10) 9 (9) 10 (9)
± 0.3 kcal/mol ± 1 kcal/mol for values in parenthesis Experimental ∆H°-values for binding nth water molecule to neurotensin (ELYENKPRRPYIL) in charge states +1, +2, and +3 Experimental ∆H°-values for binding nth water molecule to neurotensin (ELYENKPRRPYIL) in charge states +1, +2, and +3 +1 +2 Experimental ∆H°-values for binding nth water molecule to neurotensin (ELYENK +3 Degree of charge exposure Nature of charged groups
Expect 15 kcal/mol for exposed ammonium independent of the presence
number of preferred hydration sites ∝ z
water binding energy ≠ f(z) Multiply Charged Ions
H3N NH3
The Ammonium Group The Guanidinium Group The Carboxylate Group Several Ionic Groups Multiply Charged Ions Salt Bridges Challenges Ahead Change of Conformation Zwitterion Formation Entropy
Same sign vs opposite sign charges
Coulomb repulsion Coulomb attraction
Salt Bridge
Salt Bridge
N C N N H H H H H O O C N C N N H H H H H O O C N C N N H H H H H O O C N C N N H H H H H O O C N H H O O C H N H H O O C H
δ+ δ– δ+ δ–
AMBER
Barran, Liu, Wyttenbach, Bowers; unpublished
δ+ δ– δ+ δ–
δ+ δ– δ+ δ–
AMBER
Experimental ∆H° and ∆S° values for binding nth water molecule to bradykinin (M+H)+
4
3
2
1
kcal/mol
kcal/mol
±0.3 ±1
Hydration Sites & Energies
The Ammonium Group The Guanidinium Group The Carboxylate Group Several Ionic Groups Multiply Charged Ions Salt Bridges Challenges Ahead Change of Conformation Zwitterion Formation Entropy
ESI Ion Source ESI Ion Source MS MS Drift Cell (helium) Drift Cell (helium) MS MS Detector Detector
form M±z•(H2O)n in the source
Williams, J. Am. Soc. Mass Spectrom. 1997, 8, 565 Beauchamp, J. Am. Chem. Soc. 1998, 120, 11758.
measure cross sections in helium
Wyttenbach, Bowers, Top. Curr. Chem. 2003, 225, 207.
The Ammonium Group The Guanidinium Group The Carboxylate Group Several Ionic Groups Multiply Charged Ions Salt Bridges Challenges Ahead Change of Conformation Zwitterion Formation Entropy
H3N CH2 C O O H2N CH2 C OH O
neutral
Gly
zwitter- ion Theory Jensen and Gordon JACS, 117, 8159 (1995)
Gly•(H2O)2
12 kcal/mol zwitter- ion Photoelectron spectroscopy Xu, Nilles, Bowen J.Chem.Phys., 119, 10696 (2003) zwitter- ion
Gly•(H2O)5
2N
NH NH NH O O O O O OH D vs L residue
NH NH NH NH O O O O
NH H2N NH2
+
H3N+ O O
–
H3N CH2 C O O
H O
NH H2N NH2
+
H O
NH H2N NH2
+
different
2N
O
RNH OR’
2N
NH NH NH O O O O residue
NH NH NH NH O O O O
NH H2N NH2
+
O
500 502 504
MH
458 460 462 464 466 468 470 25 50 75 100
AARAA
MH
m/z
72 474 476 4
AARA R = Ac R’= H gas-phase H/D exchange with D2O R = H R’= H R = H R’= CH3
all
1H
all
1H
Wyttenbach, Paizs, Barran, Breci, Liu, Suhai, Wysocki, Bowers JACS 125, 13768 (2003)
different
+1.8 0.0
(AARAA)H+·H2O
+4.8 0.0
(AARAA)H+
Energy (kcal/mol)
AMBER & B3LYP/6-31+G(d,p)
zwitterion neutral termini
different
2N
O
H2N OH
2N
NH NH NH O O O O residue
NH NH NH NH O O O O
NH H2N NH2
+
O
Wyttenbach, Paizs, Barran, Breci, Liu, Suhai, Wysocki, Bowers JACS 125, 13768 (2003)
with interpretation of gas-phase H/D exchange data
binding energy (kcal/mol)
B3LYP/6-31+G(d,p)
BSSE & ZPE correction
(AARAA)H+···H2O
Wyttenbach, Paizs, Barran, Breci, Liu, Suhai, Wysocki, Bowers JACS 125, 13768 (2003)
Wyttenbach, Paizs, Barran, Breci, Liu, Suhai, Wysocki, Bowers JACS 125, 13768 (2003)
B3LYP/6-31+G(d,p)
set up for H/D exchange relay mechanism
(AARAA)H+•H2O
Neutral termini
(AARAA)H+•H2O
Zwitterion
Wyttenbach, Paizs, Barran, Breci, Liu, Suhai, Wysocki, Bowers JACS 125, 13768 (2003)
B3LYP/6-31+G(d,p)
(AARAA)H+•H2O
Transition state
Wyttenbach, Paizs, Barran, Breci, Liu, Suhai, Wysocki, Bowers JACS 125, 13768 (2003)
B3LYP/6-31+G(d,p)
The Ammonium Group The Guanidinium Group The Carboxylate Group Several Ionic Groups Multiply Charged Ions Salt Bridges Challenges Ahead Change of Conformation Zwitterion Formation Entropy
–∆S°
cal/mol/K
–∆H°
kcal/mol
all other data:
1st H2O
molecules 2nd H2O
molecules 1st H2O
molecules
∆S° < 0 loss of 3 translational and 3 rotational degrees of freedom (gain of 6 vibrational degrees of freedom)
all data positive and negative ions
floppy
tightly bound H2O
strong entropy–enthalpy correlation (red data)
exceptions are:
yields smaller than average loss of entropy → floppy hydrates
yields data between blue and red
?