Thermodynamic and kinetic stability of zwitterionic histidine: Effects of gas phase hydration

• Published in: Chemical physics letters 2015-09, Vol.637, p.42-50
• Main Authors: Lee, Sung-Sik, Kim, Ju-Young, Han, Yuna, Shim, Hyun-Jin, Lee, Sungyul
• Format: Article
• Language: English
• ISSN: 0009-2614; 1873-4448
• DOI: 10.1016/j.cplett.2015.08.003

•We calculate the structures and relative stabilities of histidine–(H2O)n (n=0–6) clusters.•We compare the Gibbs free energies of canonical and zwitterionic conformers.•Six H2O are required for thermodynamically stable histidine zwitterion.•Some canonical clusters may be kinetically stable in low temperature gas phase. We present calculations for histidine–(H2O)n (n=0–6) to examine the effects of micro-hydrating water molecules on the relative stability of the zwitterionic vs. canonical forms of histidine. We calculate the structures and Gibbs free energies of the conformers at wB97XD/6-311++G(d,p) level of theory. We find that six water molecules are required to produce the thermodynamically stable histidine zwitterion. By calculating the barriers of canonical↔zwitterionic transformation, we predict that both the most stable canonical and zwitterionic forms of histidine–(H2O)6 may be observed in low temperature gas phase environment.