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Catherine,

Maybe someone knows something that I don't, but what you are asking
is for the most part impossible using microscopy and calcium dyes.
All of the latter use direct electrostatic binding and/or ligand
formation which means you can't escape the electrostatic problem.

You might extract information for measured binding constants for
single component solutions, but in mixtures of protein and pectins,
you don't have enough information. You might be able to measure free
versus bound but that would be about it. Also, you would have to
assume that concentration differences could be measured to the scale
of the protein pectin interaction which I assume is molecular not
microscopic.

To that end, you might consider using EM thin sectioning and using
electron probe microanalysis. There are other little tricks that you
might try that are exotic and if you want to keep discussing it email
me directly.

Good luck,
Mario


>Search the CONFOCAL archive at
>http://listserv.acsu.buffalo.edu/cgi-bin/wa?S1=confocal
>
>        Hello everybody,
>
>        We are studying gels composed of polysaccharides (pectins) and protein
>(BSA). Pectins are gelling upon addition of calcium ions, but calcium can
>also be adsorbed on proteins. All the interactions are of electrostatic
>nature. We are interested by labelling the calcium in order to localize it
>in the blends. However, the dye should not interact with  ions by
>electrostatic interactions.
>        Can someone help us?
>
>        Thank you very much in advance
>
>        Catherine
>**********************************
>Dr Catherine Garnier
>INRA-LPCM
>Rue de la Geraudiere
>BP 71627
>44 316 Nantes Cedex 03
>France
>Phone: Int-33-2-40-67-50-45
>Fax: Int-33-2-40-67-50-43
>http://www.nantes.inra.fr/public/unites_recherche/upcm/upcm.htm
>**********************************


--
_________________________________________________________________
Mario M. Moronne, Ph.D.
NanoMed Technologies
1561 Posen Ave
Berkeley, CA
94706

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