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From: Arthur Rowe <arthur.rowe@nottingham.ac.uk>
To : Helmut Coelfen <Helmut.Coelfen@MPIKG-GOLM.MPG.DE>
Date: Thu, 08 Mar 2001 12:23:05 +0000
Re: Estimate of the density of hydration water
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Hi Helmut !
I suspect that I was the one who made the statement which you refer to at
the Duisburg conference. So I had better respond.
The whole concept of bound water having a density higher than that of bulk
water, the so-called "electrostriction effect" goes back a long, long way.
It probably predates even Cohn & Edsall, and is the long-accepted reason as
to why Traube's Rule (more or less, and unexpectedly) works for calculating
the vbar of proteins by sigma-ing the weighted contribution of the vbars of
the amino-acid residues. It appears that around +0.02 ml/g of internal void=
s
is balanced out by -0.02 ml/g of effective contribution from higher density
of bound water.
The fact that water is indeed bound at higher density has been confirmed by
various physical techniques including neutron scattering (as Heini Eisenber
has just posted), and MD studies confirm that a balancing contribution from
internal voids of this magnitude is for real: e.g.
Kelly J Frye & Catherine A Royer (1998) "Probing the contribution of
internal cavities to the volume change of protein unfolding under pressure"=
Protein Science 7 2217-2221
A similar sort of magnitude for the bound water effect comes out of other
studies, e.g.
B. Kernel, G. Zaccai & C. Ebel (1999) "Determination of partial molal
volumes, and salt & water binding, of highly charged biological
macromolecules {tRNA, halophilic protein) in multimer salt solutions"
Progr. Colloid Polym. Sci. 113 168-175
The latter work brings up the point of charge and salt concentration, which
is relevant to your system. There is a lot to do here - I am fascinated by
the quite massive (+ve) changes in vbar which (at least some) salts seem to
induce (Dieter Schubert at Duisburg, related to the earlier work of Helmut
Durschlag). This really takes some explaining. Perhaps you can post the
answer when you have it ?!
Regards
Arthur
*****************************************************
Arthur J Rowe
Professor of Biomolecular Technology
University of Nottingham
School of Biological Sciences
Sutton Bonington
Leicestershire LE12 5RD UK
Phone/voicemail +44 (0)115 951 6156
Phone/fax +44 (0)115 951 6156/7
email arthur.rowe@nottingham.ac.uk
arthur.rowe@connectfree.co.uk
Web http://www.nottingham.ac.uk/ncmh/business
*****************************************************
----------
>From: Helmut Coelfen <Helmut.Coelfen@MPIKG-GOLM.MPG.DE>
>To: rasmb@alpha.bbri.org
>Subject: Estimate of the density of hydration water
>Date: Wed, Mar 7, 2001, 7:10 pm
>
>Hello out there,
>
>for a principal investigation, I'm interested in the structuration of wate=
r
by
>polymers expressed in a density increase. We find huge differences in the
>overall solution density when certain synthetic polyelectrolytes are added=
;
>far
>higher than expected from the buoyancy increment of the polymer. From some
>of the
>last AUC conference talks I think to remember that it was observed that
>hydration
>water of proteins has a higher density than bulk water - probably an effec=
t
>of its
>structuration in the contact area to the protein. Does anyone of you have =
a
>citeable
>Reference about this effect ?
>
>Thanks a lot in advance for any help you can give.
>
>Best wishes
>
>Helmut C=F6lfen
>
>
>
>
>_______________________________________________________________
>Dr. Helmut C=F6lfen
>Max-Planck-Institute of Colloids and Interfaces
>Colloid Chemistry
>Am M=FChlenberg 2
>14424 Potsdam
>Germany
>
>Tel: --49 331 567-9513
>Fax: --49 331 567-9502
>http://www.mpikg-golm.mpg.de/kc/coelfen/
>_______________________________________________________________
>
--MS_Mac_OE_3066898986_575611_MIME_Part
Content-type: text/html; charset="ISO-8859-1"
Content-transfer-encoding: quoted-printable
<HTML>
<HEAD>
<TITLE>Re: Estimate of the density of hydration water </TITLE>
</HEAD>
<BODY BGCOLOR=3D"#FFFFFF">
<FONT SIZE=3D"2">Hi Helmut !<BR>
I suspect that I was the one who made the statement which you refer to at t=
he Duisburg conference. So I had better respond.<BR>
The whole concept of bound water having a density higher than that of bulk =
water, the so-called "electrostriction effect" goes back a long, l=
ong way. It probably predates even Cohn & Edsall, and is the long-accept=
ed reason as to why Traube's Rule (more or less, and unexpectedly) works for=
calculating the vbar of proteins by sigma-ing the weighted contribution of =
the vbars of the amino-acid residues. It appears that around +0.02 ml/g of i=
nternal voids is balanced out by -0.02 ml/g of effective contribution from h=
igher density of bound water.<BR>
The fact that water is indeed bound at higher density has been confirmed by=
various physical techniques including neutron scattering (as Heini Eisenber=
has just posted), and MD studies confirm that a balancing contribution from=
internal voids of this magnitude is for real: e.g.<BR>
Kelly J Frye & Catherine A Royer (1998) "Probing the contribution =
of internal cavities to the volume change of protein unfolding under pressur=
e" Protein Science <B>7</B> 2217-2221<BR>
A similar sort of magnitude for the bound water effect comes out of other s=
tudies, e.g.<BR>
B. Kernel, G. Zaccai & C. Ebel (1999) "Determination of partial mo=
lal volumes, and salt & water binding, of highly charged biological macr=
omolecules {tRNA, halophilic protein) in multimer salt solutions" Prog=
r. Colloid Polym. Sci. </FONT><B>113 </B><FONT SIZE=3D"2">168-175<BR>
The latter work brings up the point of charge and salt concentration, which=
is relevant to your system. There is a lot to do here - I am fascinated by=
the quite massive (+ve) changes in vbar which (at least some) salts seem to=
induce (Dieter Schubert at Duisburg, related to the earlier work of Helmut =
Durschlag). This really takes some explaining. Perhaps you can post the ans=
wer when you have it ?!<BR>
Regards<BR>
Arthur<BR>
*****************************************************<BR>
Arthur J Rowe<BR>
Professor of Biomolecular Technology<BR>
University of Nottingham<BR>
School of Biological Sciences<BR>
Sutton Bonington<BR>
Leicestershire LE12 5RD UK<BR>
<BR>
Phone/voicemail +44 (0)115 951 6156<BR>
Phone/fax +44 (0)115 951 6156/7<BR>
email arthur.rowe@nottingham.ac.uk<BR>
arthur.rowe@connectfree.co.uk<BR>
Web http://www.nottingham.ac.uk/ncmh/business<BR>
*****************************************************<BR>
<BR>
----------<BR>
>From: Helmut Coelfen <Helmut.Coelfen@MPIKG-GOLM.MPG.DE><BR>
>To: rasmb@alpha.bbri.org<BR>
>Subject: Estimate of the density of hydration water <BR>
>Date: Wed, Mar 7, 2001, 7:10 pm<BR>
><BR>
<BR>
>Hello out there,<BR>
><BR>
>for a principal investigation, I'm interested in the structuration of w=
ater by<BR>
>polymers expressed in a density increase. We find huge differences in t=
he<BR>
>overall solution density when certain synthetic polyelectrolytes are ad=
ded;<BR>
>far <BR>
>higher than expected from the buoyancy increment of the polymer. From s=
ome<BR>
>of the <BR>
>last AUC conference talks I think to remember that it was observed that=
<BR>
>hydration<BR>
>water of proteins has a higher density than bulk water - probably an ef=
fect<BR>
>of its<BR>
>structuration in the contact area to the protein. Does anyone of you ha=
ve a<BR>
>citeable<BR>
>Reference about this effect ?<BR>
><BR>
>Thanks a lot in advance for any help you can give. <BR>
><BR>
>Best wishes<BR>
><BR>
>Helmut C=F6lfen<BR>
><BR>
><BR>
><BR>
><BR>
>_______________________________________________________________<BR>
>Dr. Helmut C=F6lfen<BR>
>Max-Planck-Institute of Colloids and Interfaces<BR>
>Colloid Chemistry<BR>
>Am M=FChlenberg 2<BR>
>14424 Potsdam <BR>
>Germany<BR>
><BR>
>Tel: --49 331 567-9513<BR>
>Fax: --49 331 567-9502<BR>
>http://www.mpikg-golm.mpg.de/kc/coelfen/<BR>
>_______________________________________________________________<BR>
><BR>
<BR>
<BR>
</FONT>
</BODY>
</HTML>
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