The diffuse x-ray diffraction patterns of agarose gels are compatible
with both the ''chicken-wire'' gel model consisting of associated doub
le-helix chain conformations and a network of more extended, but unent
wined helices. Preference for the double-helix model has largely reste
d on an early interpretation of optical rotation data. Applying a rece
nt, less empirical, chiroptical model of saccharide rotation, we confi
rm the earlier analysis by concluding that the rotation observed in th
e gel can be satisfactorily accounted for in terms of wide-diameter ag
arose helices, capable of intertwining. In addition, we have found tha
t the extended helices found in dried sols do not yield the observed g
el rotations. (C) 1995 John Wiley & Sons, Inc.