Chirped-pulsed FTMW Spectrum of Valeric
Acid and 5-Aminovaleric Acid. A Study of
Amino Acid Mimics in the Gas Phase.
Ryan G. Bird, Vanesa Vaquero, and David W. Pratt
University of Pittsburgh
Daniel Zaleski and Brooks H. Pate
University of Virginia
Importance of n-π* Interactions
• H-bond formation in proteins
• Recently findings suggest n-π* bonds are just
as important1
• A survey of 1731 proteins in the PDB found
possible n-π* interaction in every one
• Majority of n-π* interaction occurred in αhelices
1Bartlett,
G.; Choudhary, A.; Raines, R.; Woolfson, D.; Nat. Chem. Biol. 2010, 6, 615-620
Organic Acids
• Valeric Acid
• Propanoic Acid1
• 5-Aminovaleric Acid
• 4-Aminobutanoic Acid (GABA)3
• 3-Aminopropanoic Acid (β-Alanine)2
1Ouyang,
B.; Howard, B. J. J. Phys. Chem. A 2008, 112, 8208-8214..
M. E.; et. al.. J. Am. Chem. Soc. 2006, 128, 3812-3817.
3Blanco, S.; López, J. C.; Mata, S.; Alonso, J. L. Angew. Chem. Int. Ed. 2010, 49, 9187-9192.
2Sanz,
CP-FTMW Spectrometer
Pratt Group CP-FTMW
spectrometer1
Horn to Mirror Cavity
~500 MHz chirped Pulse
1 Nozzle, 10 Hz
1Bird,
Pate Group CP-FTMW
spectrometer2
Horn to Horn Cavity
~11 GHz chirped Pulse
3 Nozzle, 7 Hz
R.G., Neill, J.L., Alstadt, V.J., Pate, B.H., and Pratt, D.W. J. Phys. Chem. A, in press .
2 Brown, G. G.; Dian, B. C.; Douglass, K. O.; Geyer, S. M.; Shipman, S. T.; Pate, B. H. Rev. Sci. Instrum. 2008, 79, 053103.
Valeric Acid
Valeric Acid
Parameters
Experiment
m052x/
6-31g(d,p)
A (MHz)
7951.42(1)
8001.27
B (MHz)
1051.011(5)
1058.629
C (MHz)
950.947(3)
956.863
ΔI (uÅ2)
-13.0
-12.4
Nlines
11
5-Aminovaleric Acid??
5-Valerolactam
δ-Valerolactam
Parameter
A (MHz)
B (MHz)
C (MHz)
χaa (MHz)
χbb (MHz)
χcc (MHz)
ΔI
1Kuze,
This Work
4590.9107(6)
2495.0392(6)
1731.0550(3)
2.323(8)
1.86(1)
-4.18(1)
-20.7
N.; et. al. J. Mol. Spectrosc. 1999, 198, 381-386
Kuze1
4590.96(11)
2495.03(2)
1731.06(2)
-21.0
m052x/6-31g(d,p)
4618.95
2505.722
1739.754
2.32
1.84
-4.16
-20.6
δ-Valerolactam Reaction
Reaction Coordinate
0.06
Relative Energy (Hartree)
0.05
0.04
0.03
0.02
0.01
103 kJ/mol
0
-0.01
-0.02
-0.03
-0.04
-0.05
120 kJ/mol
Comparison of Lowest Energy
Conformer
Experimental
Theory
n··· π*
interaction
n- π*
bond
n··· π*
interaction
no
interaction
N-H ···O
hydrogen bond
N-H ···O
hydrogen bond
δ-Valerolactam Spectrum
Parent
14N(1)
13C(2)
13C(3)
13C(4)
13C(5)
13C(6)
Isotopomers
15N (1)
13C (2)
13C (3)
13C (4)
13C (5)
13C (6)
Parent
A (MHz)
4537.26(4)
4591.09(4)
4520.36(3)
4528.26(1)
4586.77(2)
B (MHz)
2493.635(2) 2481.339(1) 2493.924(1) 2476.8510(4) 2454.0144(9) 2479.800(1) 2495.0462(9)
C (MHz)
1722.705(2) 1724.486(4) 1720.576(3) 1714.485(1) 1711.834(2) 1714.522(3) 1731.0549(3)
4524.46(3) 4590.9052(8)
χaa (MHz)
2.34(2)
2.34(2)
2.31(1)
2.32(1)
2.30(2)
2.33(1)
χbb (MHz)
1.40(6)
1.85(3)
1.81(2)
1.86(8)
1.93(6)
1.85(2)
χcc (MHz)
-3.74(6)
-4.19(3)
-4.12(2)
-4.18(8)
-4.23(6)
-4.18(2)
31
25
25
20
26
132
Nlines
9
Kraitchman Analysis
A
B
C
N (1)
0.338(5)
-1.149(1)
-0.02(1)
C (2)
1.061(1)
-0.076(2)
-0.03(4)
C (3)
0.273(5)
1.310(1)
-0.13(1)
C (4)
-1.175(1)
1.207(1)
0.312(4)
C (5)
-1.817(1)
-0.07(2)
-0.326(5)
C (6)
-1.099(1)
-1.275(1)
0.16(1)
Water Complex
Lactam H2O
m052x/
6-31+g(d,p)
Lactam (H2O)2
m052x/
6-31+g(d,p)
A (MHz)
3485.929(2)
3493.856
2314.66(1)
2328.24
B (MHz)
1244.7297(8)
1258.315
823.0632(5)
827.218
C (MHz)
954.725(2)
962.679
625.404(1)
629.999
χzz (MHz)
1.70(1)
1.33
1.3(1)
1.1
χxx (MHz)
2.02(3)
2.35
2.1(1)
2.3
χyy (MHz)
-3.73(3)
-3.69
-3.4(1)
-3.4
ΔJ (kHz)
0.23(1)
0.116(3)
ΔJK (kHz)
-0.46(6)
0.14(3)
δj (kHz)
0.042(5)
0.025(2)
δk (kHz)
1.1(2)
0.38(7)
Nlines
91
49
δ-Valerolactam Water Complexes
Conclusions
• Collected and analyzed spectra of valeric acid
and δ-valerolactam
• Using Gaussian and δ -valerolactam, we
determined structure of 5-aminovaleric acid
• Rejection of delta-amino acid as evolutionary
precursor
• Future Work: KIE analysis on 5-valerolactam
spectrum with ~500,000 averages
Acknowledgements
Pratt Group:
Pate Group:
Dr. David Pratt
Justin Young
A.J. Fleisher
Dr. Vanessa Vaquero
Valerie J. Alstadt
Dr. Brooks Pate
Justin Neill
Matt Muckle
Daniel Zaleski
Amanda Steber