Table Of ContentSolutio Propertie
Polysaccharides
In Solution Properties of Polysaccharides; Brant, D.;
ACS Symposium Series; American Chemical Society: Washington, DC, 1981.
In Solution Properties of Polysaccharides; Brant, D.;
ACS Symposium Series; American Chemical Society: Washington, DC, 1981.
Solution Properties of
Polysaccharides
David A. Brant, EDITOR
University of California
Based on a symposium
sponsored by the Division
of Carbohydrate Chemistry
at the 179th Meeting of the
American Chemical Society,
Houston, Texas,
March 24-27, 1980.
150
ACS SYMPOSIUM SERIES
AMERICAN CHEMICAL SOCIETY
WASHINGTON, D. C. 1981
In Solution Properties of Polysaccharides; Brant, D.;
ACS Symposium Series; American Chemical Society: Washington, DC, 1981.
Library of Congress CIP Data
Solution properties of polysaccharides.
(ACS symposium series, ISSN 0097-6156; 150)
Includes bibliographies and index.
1. Polysaccharides—Congresses. 2. Solution (Chem
istry)—Congresses.
I. Brant, David A. II. American Chemical Society.
Division of Carbohydrate Chemistry. III. Series.
QD320.S5 547.7'8204541 81-236
ISBN 0-8412-0609-0 ACSMC8 150 1-580 AACR2
Copyright © 1981
American Chemical Society
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In Solution Properties of Polysaccharides; Brant, D.;
ACS Symposium Series; American Chemical Society: Washington, DC, 1981.
ACS Symposium Series
M. Joan Comstock, Series Editor
Advisory Board
David L. Allara James P. Lodge
Kenneth B. Bischoff Marvin Margoshes
Donald D. Dollberg Leon Petrakis
Robert E. Feeney Theodore Provder
Jack Halpern F. Sherwood Rowland
Brian M. Harney Dennis Schuetzle
W. Jeffrey Howe Davis L. Temple, Jr.
James D. Idol, Jr. Gunter Zweig
In Solution Properties of Polysaccharides; Brant, D.;
ACS Symposium Series; American Chemical Society: Washington, DC, 1981.
FOREWORD
The ACS SYMPOSIUM SERIES was founded in 1974 to provide
a medium for publishin symposi quickl i book form Th
format of the Serie
IN CHEMISTRY SERIES except that in order to save time the
papers are not typeset but are reproduced as they are sub
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viewed under the supervision of the Editors with the assistance
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In Solution Properties of Polysaccharides; Brant, D.;
ACS Symposium Series; American Chemical Society: Washington, DC, 1981.
PREFACE
T
his volume is the outgrowth of a symposium on the solution properties
of polysaccharides and reflects the success of the symposium in bringing
together an international group of experts engaged in studies of virtually
every aspect of the solution behavior of polysaccharides. Thirty-seven
chapters span the range from conformational analysis of dissolved poly
saccharides using spectroscopic, scattering, hydrodynamic, and theoretical
methods to experimental and theoretical investigations of the interactions
between dissolved polysaccharide chains and between polysaccharides and
a variety of high- and low-molecular-weight ligand species. Without excep
tion these chapters are
fields, and the book represent person
wish to remain or become conversant with current research on polysac
charide solution properties.
Chemical and biological interest in polysaccharides has begun to shift
over the past decade from the structural and storage polysaccharides of
plant origin, e.g. cellulose, carrageenan, and starch, toward polysaccharides
of animal and, especially, microbial origin. The existing and potential
commercial importance of extracellular microbial polysaccharides produced
by fermentation using relatively inexpensive feedstocks has provided a
major impetus for the increasing attention being given to these materials;
the range of chemical and structural characteristics represented among the
known microbial polymers and those potentially available by genetic engi
neering techniques can only further encourage this activity. Among poly
saccharides of animal origin attention now is focused strongly on the
mucopolysaccharides or proteoglycans that occur, usually in close associa
tion with protein, in the intercellular matrix of the connective tissues. This
interest is motivated by evidence that abnormalities in the distribution of
these substances accompany a number of serious metabolic diseases.
Finally, the emerging recognition of poly- and oligosaccharides as immuno
chemical determinants has served as a strong stimulus for studies of poly
mers of both animal and microbial origin.
The polysaccharides derived from these two sources are almost always
highly solvated, if not actually dissolved, in their native environment.
Consequently it is appropriate that investigations of the relationships
between the chemical structures and the physical and biological properties
of these species should give special attention to their solution behavior.
xi
In Solution Properties of Polysaccharides; Brant, D.;
ACS Symposium Series; American Chemical Society: Washington, DC, 1981.
Even for those polysaccharides that are crystalline or semicrystalline in
nature, solution studies must play an important role. Investigations of the
solution properties of all polymers are necessary not only to obtain funda
mental data concerning the mean molecular weights and molecular-weight
distributions of the macromolecular species, but also to provide information
about relationships between chemical structure and the inherent conforma
tional characteristics of individual macromolecules free of interactions with
other like or unlike species. Such interactions are, of course, important for
the biological function and physical behavior of polysaccharides, and
solution studies also provide a unique avenue to information about inter
actions between small numbers of polysaccharide chains or between poly
saccharides and other kinds of molecules and ions. This book illustrates
the diverse modern techniques currently being exploited to investigate these
properties of polysaccharides in solution.
University of California a
Irvine, CA 92717
November 4, 1980
xii
In Solution Properties of Polysaccharides; Brant, D.;
ACS Symposium Series; American Chemical Society: Washington, DC, 1981.
1
Quasielastic Light-Scattering Studies of Xanthan
in Solution
J. G. SOUTHWICK, A. M. JAMIESON, and J. BLACKWELL
Department of Macromolecular Science, Case Western Reserve University,
Cleveland, OH 44106
We are using quasielasti
the conformation and interaction
Xanthan i s the extracellular polysaccharide produced by the
bacterium Xanthomonas campestris and has a wide variety of uses,
e.g. as a viscosity enhancer and food additive. The chemical
structure is a repeating pentasaccharide:(1,2) a β-1,4-D-glucan
backbone with a trisaccharide substituent on alternating backbone
residues. The side chain i s β-1,3 linked β-D-mannopyranosyl-α-
1,4-D-glucuropyranosyl-β-1,2-D-mannopyranoside 6-0-acetate. In
addition, the terminal D-mannose residue of the side chain may
have a pyruvic acid residue linked at the 4- and 6- positions.
The degree of pyruvation typically varies from 0.31 - 0.56,(3)
depending on the bacterial strain, history, and fermentation
conditions.(4,5)
Early physical chemical studies of xanthan in aqueous solu
tion at low ionic strength showed an unusual property in that
there was a sigmoidal increase in the viscosity of a 1% solution
at T ~55°C.(6) Spectroscopic measurements using ORD, CD, and
m
NMR methods have also detected this transition.(7) At room tem
perature a broad, featureless NMR spectrum i s obtained, but the
spectra become sharp and detailed above the transition tempera
ture. As a result, the transition i s explained as an order-
disorder phenomenon, probably due to conversion of a helix to a
flexible coil. It has also been shown that the transition tem
perature i s variable, depending on the presence of trace ions.(8)
From x-ray diffraction studies of oriented crystalline films,
Moorhouse et al(9) showed that the most likely solid state con
formation i s a 5 right-handed single helix, repeating in 47A. A
1
significant feature of this structure i s that the trisaccharide
side chains are arranged close to (and hydrogen bonded to) the
glucan backbone, which could be expected to stabilize a stiff hel
ical conformation i n solution. However, the x-ray patterns were
not of sufficient quality to determine the structure unambigu
ously, and other conformations including multiple strand helices
also need to be considered. Electron microscopy by Holzwarth(10)
0097-6156/81/0150-0001$05.00/0
© 1981 American Chemical Society
In Solution Properties of Polysaccharides; Brant, D.;
ACS Symposium Series; American Chemical Society: Washington, DC, 1981.
2 SOLUTION PROPERTIES OF POLYSACCHARIDES
has shown that rod-like aggregates are precipitated from unheated
xanthan solutions. Shorter, thinner chains are observed in prepa
rations of heated (denatured) xanthan, and from the observed
dimensions i t is argued that the ordered form consists of a double
helical aggregate of an average of 40 chains.
Our light scattering studies focused initially on the thermal
transition, in order to compare the diffusion properties of
xanthan above and below T . This led to an interest in the con
m
centration dependence of diffusion and the development of chain
overlap and entanglement points. Some of the work reviewed below
has been published separately.(11,12,13,14)
Experimental
Xanthan Solutions. Specimens of xanthan were obtained from
Kelco Co. (Kelzan) and fro Dr P Sandford the t U.S.D.A
Northern Regional Laboratory
described by Holzwarth.
^ 0.5% xanthan was prepared by addition of distilled deionized
water that had previously been filtered through O.lum Millipore
filters (to remove bacteria, dust, etc.). This solution was
dialyzed for four days against filtered distilled deionized water.
Other than for the first solutions used for the thermal studies,
sodium azide (0.02%) was added to the stock solutions to retard
bacterial growth. Solutions at different concentrations were
prepared by dilution with 0.02% aqueous sodium azide. Preparations
before and at different intervals after filtration were checked
for possible bacterial growth by examination of shadowed speci
mens in a Jeol 100B electron microscope. Bacterial cells were not
seen in xanthan solutions that had been filtered through 0.22ym
Millipore filters; these solutions remained sterile for over a
month.
Aqueous xanthan solutions (in 0.02% sodium azide) were
routinely filtered and centrifuged at ^ 4350g for 30 minutes
before collecting the light scattering data. These solutions
showed a slow transition to lower values of D, at a rate that
t
increased with the concentration, and this time dependence is
one of the subjects of this paper. Solutions in f iltered 4M urea
were maintained at 90°C for three hours and then cooled slowly
to room temperature.
Light Scattering. The thermal transition was studied using
a laser light scattering instrument consisting of an argon ion
laser (X = 4880A), an EMI 9656KR phototube, a Keithley 104 wide
band amplifier, and a Saicor SAI-52 real time 400 point spectrum
analyzer and digital integrator; the homodyne data were recorded
as the voltage spectra and converted to the power spectra by
squaring 40 data points and subtracting the background. The
latter data formed the input for a Lorentzian curve fitting pro
gram, from which the half width at half height, T, was deter-
In Solution Properties of Polysaccharides; Brant, D.;
ACS Symposium Series; American Chemical Society: Washington, DC, 1981.
