Double helix 172 INDEX

Amylopectin is responsible for the crystalline character of the starch granule and its structure can be modelled as a hyperbranched molecule [10,11, 28,29]. The model for the amylopectin molecule proposed by Robin [14] is illustrated in Figure 4.1(c). The A-chains, which are short segments of 15 D-glucopyranosyl residues, are the portion responsible for the crystalline structure of amylopectin. Starch crystallites are thus formed by compact areas made up of A-chains with DP 15. The crystallinity index of regular corn starch with 73% amylose is equivalent to that of waxy maize starch which is 100% amylose this confirms that amylose content has little effect on granule crystallinity. Starch crystallites formed in compact areas are made up of vicinal A-chains in a compact double helix conformation with two extended helices possessing 6 residues per turn that repeat every 21 A [1]. 

Hyperchromic effect increase in the absorbance of a solution at a particular wavelength due to structural changes in the solute molecules. The H.e. is a useful experimental index of DNA denaturation, since the A2J0 of a DNA solution increases when the double helix is transformed by heating into a disordered random coil (see Hybridization). 

The product JN gives the index of the functions K (jc a). For = 2, the expression (77) turns into (74) [only the terms with even n survive in (74) for h = 77/2]. The energy density for a single string follows for = 1. This corresponds to the situation considered by Kunze and Netz [77]. However, the expressions for the energies are different, as mentioned in the last Sect. 6.1.2 (Double Helix). 

---