A reexamination of the double‐helix model for agarose gels using optical rotation

The diffuse x‐ray diffraction patterns of agarose gels are compatible with both the “chicken‐wire” gel model consisting of associated double‐helix chain conformations and a network of more extended, but unentwined helices. Preference f or the double‐helix model has largely rested on an early interpretation of optical rotation data. Applying a recent, less empirical, chiroptical model of saccharide rotation, we confirm the earlier analysis by concluding that the rotation observed in the gel can be satisfactorily accounted for in terms of wide‐diameter agarose helices, capable of intertwining. In addition, we have found that the extended helices found in dried sols do not yield the observed gel rotations.