Subject: Summary of Answer to Ln3+ and water

From: [email-masked] (Andre Monteil)
Date: Wed, 4 Jan 1995 15:37:41 +0000

Dear Netters,

  Thank you for your answers to my question :

> I am looking for references about Lanthanide ions and water interaction.
> Specially I need Lennard-Jones parameters for MD simulation.

These are the answers :

******************************************************
        Tom Cundari
******************************
 
        The following paper by Ben Hay describes the extension of the MM2 force
field to Ln(III) aqua complexes.  This paper may have the data you require or
point you to the appropriate literature references.  Good luck.

Hay, B. P. Inorg. Chem. 1991, 30, 1991.

******************************************************
        Iosif Vaisman
******************************

AUTHOR(s):       Helm, L.
                 Foglia, F.
                 Kowall, T.
TITLE(s):        Structure and dynamics of lanthanide ions and lanthanide
                   complexes in solution.

           In:   Journal of physics.  Condensed matter :  an Inst
                 JUN 06 1994 v 6 n 23A supp
         Page:   A137
     SICI Code:  0953-8984(19940606)6:23A:suppL.A137:SDLI;1-

AUTHOR(s):       Frey, Steven T.
TITLE(s):        Characterization of Lanthanide Complexes with a Series of
                   Amide-Based Macrocycles, Potential MRI Contrast Agents,
                   Using Eu3+ Luminescence Spectroscopy and Molecular
                   Mechanics.
Summary:         Eu3+ luminescence spectroscopy was used to thoroughly
                   characterize complexes with a series of amide-based
                   macrocycles in aqueous solution, providing stoichiometries,
                   formation constants, and the number of Eu3+ coordinated
                   water molecules. Deductions regarding the composition of
                   the first coordination sphere of the Eu3+ ion are reported
                   on the basis of molecular mechanics calculations. Shown
                   here is a stereoscopic drawing of the energy-minimized
                   structure of Eu2(bis(dtpa-eam))
                 (H2O)2.

           In:   Inorganic chemistry.
                 JUN 22 1994 v 33 n 13
         Page:   2882

AUTHOR(s):       Fossheim, R.
                 Dahl, S.G.
TITLE(s):        Molecular Structure and Dynamics of Aminopolycarboxylates
                   and their Lanthanide Ion Complexes.

           In:   Acta chemica Scandinavica.
                 AUG 01 1990 v 44 n 7
         Page:   698

******************************************************
        Bill Ross
******************************

Here is some discussion on ions that may help, abstracted from
a document in the tree under

        http://www.amber.ucsf.edu/amber/amber.html

Bill Ross

         van der Waals parameters:  ...
    Monoatomic ions, however, do not
    present  such  analogies in the Amber force field.  Therefore a
    more basic discussion follows.  The simplest approach to deriv-
    ing  van  der Waals parameters is to somehow match some experi-
    mental determination of the size of the atom in question.   One
    source  of such measurements is diffraction data.  For example,
    the sum of metal and oxygen Pauling radii [2] tends  to  be  3%
    smaller  than indicated by water-ion neutron and X-ray diffrac-
    tion data for Li+ and Na+ ions, 2% smaller than for K+, and  1%
    smaller than for Rb+ and Cs+ [3].  Another source of ion `size'
    information is crystallographic studies of ion  complexes  [4].
    Since van der Waals parameters consist of two terms, the param-
    eters that yield a given size are not unique.  Another  experi-
    mental  datum  that  can  contribute to parameterization is the
    free energy of solvation in water or another relevant  solvent.
    However,  it is not clear whether the combination of experimen-
    tal size and solvation free energy determines unique  modelling
    parameters.   A further complication arises because R*, epsilon
    parameters are seperately ``combined'' with those for  each  of
    the  other  atom  types  to  give the interatomic van der Waals
    potentials.  Therefore, it is important  to  choose  parameters
    consistent  with  the atom types that the new type will come in
    contact with.  In particular, the TIP water models (as well  as
    other waters) have a spherical van der Waals potential centered
    on the water oxygen, which is somewhat inflated to enclose  the
    hydrogen  atoms  in  the molecule.  Thus a cation that has been
    parameterized to give a correct  radial  distance  distribution
    function  in such a water model will be ``smaller'' and come in
    closer contact with neighboring atoms  if  it  is  bound  in  a
    molecule  consisting  of Amber atoms.  Moreover, different com-
    bining rules are in use in the  modelling  community,  so  that
    ____________________
       [2] Pauling, L. The Nature of  the  Chemical  Bond  and  the
    Structure  of Molecules and Crystals; Cornell University Press:
    Ithaca, New York, 1960.
       [3]  Ross,  W. S. and Hardin, C. C., J. Am. Chem. Soc. 1994,
    116, 6070-6080.  (This discussion of van der  Waals  parameters
    is based on that work.)
       [4]  Vedani,  A., Huhta, D. W., J. Am. Chem. Soc. 1990, 112,
    4759-4767 and references therein.
    ____________________

    parameters from one convention must even be  adapted  to  yield
    the  same  results in another scheme.  Thus it was necessary to
    adapt the monovalent cation parameters of A"" vist [5] found in
    parm94.dat  and parm91.dat for Amber so that the ion-water com-
    bined potential gave the same optimal distance as with the com-
    bining  rules  used  by A"" vist.  Matching the ion size in the
    environment seems to be sufficient in the case with  monoatomic
    cations; the default has traditionally [6] been to use a  some-
    what  arbitrary  well  depth (epsilon) of 0.1 kcal/mol, charac-
    teristic of a rather nonpolarizable atom, and fit an R* parame-
    ter  (see  the  Ross and Hardin reference).  For simulating the
    effect of ions in solution on a macromolecular solute,  insofar
    as  the  ions do not come in contact with the solute, the finer
    points of van der Waals parametrization should  not  have  much
    bearing  on the outcome.  In a vacuum simulation with distance-
    dependent dielectric to simulate water, an ionic radius  should
    be  used  which includes the solvation shell, and in this case,
    given the other approximations, exact van der Waals parameteri-
    zation  is even less important.  For the multivalent ions, dif-
    ferent further approaches may  be  considered  to  capture  the
    quasi-bonding  electron mobility, including the use of explicit
    bonds or hydrogen bonding  terms  (see  the  Vedani  and  Huhta
    reference).

******************************************************
        Jan Hrusak
******************************

In the last NATO meeting this summer, there has been a poster to this
topic by a group from Lausanne. Contact Thomas Kowall for more information.

Institute de Chimie minerale et analytique,
Universite de Lausanne
BCH 
1015  Lausanne

******************************************************
        Fernando Luis Barroso da Silva
******************************

Did you read Hitoshi Ohtaki and Tomas Radnai's paper ( "Structure and
Dynamics of Hydrated Ions" Chemical Reviews, 1993, vol. 93, n. 3 ) ?  Look
at page 1183! 

******************************************************
        Michael Probst
******************************

A paper dealing with aqueous LnCl3 solution (MD - Simulations)
is in J.Phys.Chem. 94, p.4672 (1990)
A paper with ab inito calculations on the interaction of water with
all Lanthanides appeared in Z.Naturforsch. 46a, p.117 (1991)
Hope that helps !

******************************************************

 By another way we found an interesting reference which was helpful :
  P. Auffinger and G. Wipff
  J. Am. Chem. Soc. (1991) 113, p 5976

    Merci et Bonne Annee a tous
             Andre'

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