Miller Dorothy J, Lisy James M
Department of Chemistry, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA.
J Chem Phys. 2006 May 14;124(18):184301. doi: 10.1063/1.2191047.
In recent years neutral indole(H2O)n clusters have been used to model the hydration of biomolecules containing an indole moiety. Both experimental and theoretical studies of the binary indole...OH2 system show NH...OH sigma hydrogen-bonding. By introducing a cation to the indole...OH2 model, cation...pi and ion...dipole electrostatic interactions are placed in direct competition with conventional indole...OH2 hydrogen-bonding. The effects, arising from a monovalent potassium cation on (indole)m(H2O)n clusters, were investigated using infrared photodissociation spectroscopy in the OH and NH stretching regions. In K+ (indole)1(H2O)(n < or = 4) and K+ (indole)2(H2O)(m < or = 3) clusters, the electrostatic ion...ligand interaction inhibits the formation of an indole NH...OH2 sigma hydrogen-bond. However, indole...H2O pi hydrogen-bonding via the five-membered indole ring is observed with three or more ligands around the ion.
近年来，中性吲哚(H2O)n簇已被用于模拟含吲哚部分的生物分子的水合作用。对二元吲哚…OH2体系的实验和理论研究均表明存在NH…OH σ氢键。通过向吲哚…OH2模型中引入阳离子，阳离子…π和离子…偶极静电相互作用与传统的吲哚…OH2氢键直接竞争。利用红外光解离光谱在OH和NH伸缩区域研究了一价钾阳离子对(吲哚)m(H2O)n簇的影响。在K+(吲哚)1(H2O)(n≤4)和K+(吲哚)2(H2O)(m≤3)簇中，静电离子…配体相互作用抑制了吲哚NH…OH2 σ氢键的形成。然而，在离子周围有三个或更多配体时，观察到通过五元吲哚环的吲哚…H2O π氢键。
