New x‐ray diffraction results from agarose: Extended single helix structures and implications for gelation mechanism

A new series of x‐ray fiber diffraction patterns is reported from agarose films dried at temperatures close to 100°C from water or dimethylacetamide solutions, cooled to room temperature, stretched above 40°C, and finally x‐rayed at room temperature. This procedure gives x‐ray patterns showing highly crystalline forms of agarose with projected axial advances (h) per repeating disaccharide in the range of 0.888–0.973 nm, and favoring extended and single agarose chains. Stretching the films below 40°C yields an oriented but fairly diffuse x‐ray pattern, similar to that reported previously for agarose, and that has been interpreted in terms of a model with two semicontracted agarose chains, with a value of h = 0.634 nm, draping around each other to form a double helix.

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