This arrangement allows two chains to join together and adopt a LH double helix. The two chains wrap together so tightly that gaps are closed, and water is trapped inside the helix. The two chains have 4 ends and these remain as random chains that are able to link up with other random coil ends of other helices so giving extensive cross linking, and a 3-D complex of helix tubes containing water. Thus short coil lengths allow more helix structure, holds more water, but less strong because less cross links. Seaweed agarose Seaweed algae can alter their agar to suit the prevaling conditions.
Sulphate is bulky and disrupts helix formation so acts as a helix breaker.
When seaweed in deep water, sulphate removed by enzymes so softer gel prevails to allow nutrients to permeate better. When tide is going out and seaweed is bashed by waves, sulphate is added and more cross linking strengthens the agar. Commercially it is very important to understand process as it affects harvesting of seaweed for processing and agar extraction and post harvest modification to suit customer needs. Food industry prefers soft gel, but microbiological and pharmaceutical industry prefers a harder gel. Enzymologists are learning how to do the sulphate modifications so that agar can be harvested all year round then modified in the laboratory to specified gel strengths.