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Stability and IR spectroscopy of zwitterionic form of β-alanine in water clusters

: Ghassemizadeh, R.; Moore, B.; Momose, T.; Walter, M.


Journal of physical chemistry. B 123 (2019), Nr.20, S.4392-4399
ISSN: 1089-5647
ISSN: 1520-6106
ISSN: 1520-5207
Deutsche Forschungsgemeinschaft DFG
IRTG 2079 CoCo
Fraunhofer IWM ()
amino acid; ammonia; computation theory; density functional theory

Amino acids are the building blocks of proteins, and their detection in outer space thus has implications on the origin of life. They form a zwitterionic structure in aqueous environments while adopting a neutral configuration in the gas phase. We perform an experimental and computational study on the number of water molecules needed for zwitterion formation of β-alanine. Our density functional theory investigation reveals that a minimum of five water molecules are required to form and stabilize the zwitterion. A characteristic connecting water molecule located between the COO- and NH3+ groups is found to enhance the stability. This water molecule is also involved in a characteristic infrared active vibration at ≈1560 cm-1, which is slightly shifted with the number of surrounding water molecules and is located in a spectral region outside of water vibrations. A corresponding infrared signal is found in high-resolution experimental spectra of β-alanine and water in a solid para-hydrogen matrix.