Agarose molecular structure

Agarose and its O-methyl, sulfate, 0-(2-hydroxyethyl), and 0-(car-boxyethylidene) derivatives give diffraction diagrams corresponding to a common molecular structure. A double helix having an axial periodicity of 9.5 A (950 pm) was proposed. Each chain in the double helix is a left-handed, threefold helix of pitch 19.0 A (1.90 nm), and it is translated axially, relative to its partner, by 9.5 A (950 pm). 

The adsorption capacity of stationary phases containing different divalent metal ions chelated to IDA-agarose has been found to decrease for human serum proteins in the order Cu > Zn " " > Ni > Mn " [13]. Certain interferons, depending on their molecular structure, were bound to a Cu -IDA column but not to Zn +-IDA [77], whereas other interferons had higher affinity for Zn " " than... 

Fig. 5-2. Molecular structures of some of the most commonly used polymer systems. (A) Polystyrene, a copolymer of styrene and divinylbenzene, (B) polyacrylamide, a copolymer of acrylamide and methylenebisacrylamide, (C) HEMA, a copolymer of ethylene glycol methacrylate and bisethylene glycol methacrylate, (D) cross-linked dextran, (E) agarose, (F) cellulose.

The structures of agarose, iota- and kappa-carrageenan have been determined by x-ray fiber diffraction (24-27). The quality of the diffraction data obtained from each of these three specimens varies considerably and the way in which these data are used in structure determination is outlined here. Diffraction patterns from oriented specimens of agarose, and kappa- and iota-carrageenan are shown in Figure 6 (28). The molecular repeat distances derived from these patterns are listed in Table I. 

Table I. Molecular Repeat Distances and Pitches of Agarose and Carrageenan Structures...

---