title: Structure and hydration of L-proline in aqueous solutions.
abstract: The structure and hydration of L-proline in aqueous solution have been investigated using a combination of neutron diffraction with isotopic substitution, empirical potential structure refinement modeling, and small-angle neutron scattering at three concentrations, 1:10, 1:15, and 1:20 proline/water mole ratios. In each solution the carboxylate oxygen atoms from proline accept less than two hydrogen bonds from the surrounding water solvent and the amine hydrogen atoms donate less than one hydrogen bond to the surrounding water molecules. The solute-solute radial distribution functions indicate relatively weak interactions between proline molecules, and significant clustering or aggregation of proline is absent at all these concentrations. The spatial density distributions for the hydration of the COO- group in proline show a similar shape to that found previously in L-glutamic acid in aqueous solution but with a reduced coordination number.
authors.affiliation: ISIS Facility, Rutherford Appleton Laboratory, Chilton, Didcot, Oxfordshire OX11 0QX, United Kingdom. mclainse@ornl.gov
authors.forename: Sylvia E
authors.initials: SE
authors.lastname: McLain
authors.forename: Alan K
authors.initials: AK
authors.lastname: Soper
authors.forename: Ann E
authors.initials: AE
authors.lastname: Terry
authors.forename: Anthony
authors.initials: A
authors.lastname: Watts
mesh_terms: D000577:Amides / Q000737:chemistry; D002264:Carboxylic Acids / Q000737:chemistry; D004578:Electron Spin Resonance Spectroscopy; D008958:Models, Molecular; D008968:Molecular Conformation; D009502:Neutrons; D011392:Proline / Q000737:chemistry*; D012996:Solutions / Q000737:chemistry; D014867:Water / Q000737:chemistry*
chemical_list: D000577:Amides; D002264:Carboxylic Acids; D012996:Solutions; D014867:Water; D011392:Proline