Quantum chemical study of hydrogen-bonded complexes of serine with water and $$\hbox {H}_{2}\hbox {O}_{2}$$ H 2 O 2

Abstract

The hydrogen bonded complexes of serine with water and with H 2 O 2 (HP) have been completely investigated in the present study using second-order Møller-Plesset perturbation theory (MP2) and density functional theory (DFT) in order to determine their geometries, stabilization energies, vibrational frequencies and electronic characteristics. The stabilization energies (E BSSE) span a range of −2.76 to −12.46 kcal/mol for 1:1 serine-water complexes and −4.54 to −12.73 kcal/mol for 1:1 serine-HP complexes. The E BSSE values suggest that serine-HP complexes are more stable than serine-water complexes. For all the structures, complex formation results in elongation of N-H, O-H bonds and shortening of C-H bonds thereby showing the red-shift and blue-shift for the respective bonds. The structural, vibrational and electronic features are in accordance with the fact that HP is a better proton donor and water a better proton acceptor. The excellent relationship is obtained for the variation of E BSSE values with the sum of the ρ values and the sum of laplacian at the BCPs for the HBs. The E (2) values are also in concordance with the calculated E BSSE values.

Monomers of Glycine and Serine Have a Limited Ability to Hydrate in the Atmosphere

“…41 In this structure, the carboxyl group also forms a weak intramolecular hydrogen bond with the amine group, maximizing the number of hydrogen bonds. The lowest-energy structure for Ser(H 2 O) found by Chopra et al 39 does not match our lowest-energy structure (Figure 4, S1-1); in their structure, water bridges the carboxyl OH to the amine nitrogen, while in our structure the water bridges the carboxyl double-bonded O to the hydroxymethyl side chain. Because OH−H hydrogen bonds are stronger than OH−N hydrogen bonds, the structures where a water bridges the hydroxyl side chain of serine with the carboxylic acid are more favorable than those where the water bridges the carboxylic acid and amine moieties of serine.…”

“…In this structure, the carboxyl group also forms a weak intramolecular hydrogen bond with the amine group, maximizing the number of hydrogen bonds. The lowest-energy structure for Ser­(H 2 O) found by Chopra et al . does not match our lowest-energy structure (Figure , S1-1); in their structure, water bridges the carboxyl OH to the amine nitrogen, while in our structure the water bridges the carboxyl double-bonded O to the hydroxymethyl side chain.…”

“…In primary aerosols, amino acids are introduced into the atmosphere already embedded in an aerosol, while for secondary aerosols, amino acids begin in the gas phase and become aerosols through a gas-to-particle conversion . With many sources, amino acids now make up a significant portion of the total organic material in the atmosphere, and their interactions with water have been studied, including glycine − and serine. − However, these studies of the gas-phase conformations and microsolvation of amino acids have focused on spectroscopic properties and the electronic potential energy surface (PES) under vacuum conditions. Given that most atmospheric amino acids exist in solution in the aerosol phase, their potential role in the formation of CCN starting from gas-phase free monomers is incompletely understood and presents a gap in the CCN formation model.…”

Protonation of Serine in Gas and Condensed and Microsolvated States in Aqueous Solution

“…These tautomers are shown in Figure . Hydrogen bonding can stabilize zwitterionic species. − It is thought that the canonical form of serine is the most stable in gas phase while the zwitterionic form is more stable in water. , Thus, this begs the question which form is preferred as a function of number of microsolvating waters. Previous work by Kim and co-workers used computation to show that the zwitterionic form of serine could be stabilized with as few as two water molecules .…”