Dextran crystalline forms

There are at least four crystalline forms of cellulose, based on different packing of the primary chain (Blackwell, 1982), and three forms of granular starch, based on the packing of double helices (Noel et al., 1993). The differences are largely in the unit-cell dimensions and the crystallization and precipitation temperatures. One form of starch, precipitated with alcohol, is in a symmetrical molecular arrangement and is readily dispersible in cold water (Kerr, 1950). Mannan and dextran yield different crystals at low and high temperatures, and there was not only a polymorphic difference, but a conformational difference in cellulose (Quenin and Chanzy, 1987). Curdlan appears to have three polymorphs—anhydrous, hydrated, and annealed. 

Fakes et al. [1.152] evaluated the moisture sorption behavior of mannitol, anhydrous lactose, sucrose, D-(+)-trehalose, dextran 40 and povidine (PVP K24) as bulking agents. Mannitol was found to be crystalline and non-hygroscopic before and after freeze-drying with RM 0.1-0.3% w/w at 25 °C and 10-60% RH. Anhydrous lactose, sucrose and trehalose were crystalline and relatively non-hygroscopic with RM 0.86, 0.15 and 9.2% respectively. After freeze-drying they where amorphous with RM 1.6, 2.5 and 1.2%, respectively, and adsorbed moisture in an increasing RH atmosphere. Lactose adsorbed 10% water and formed its crystalline hydrate at 55% RH. 

Dextran forms crystalline, spherulitic complexes with Ca " ", Ba, and La, but not with Mg " and Na. The optical rotation of dextran in aqueous solution is considerably increased by the addition of La and Ba, but only slightly by Ca, Mg, and Na" " acetates. Complex-formation appears to ter the conformation of the polymer chain. A 20% solution of dextran will dissolve — 5% of Fe this solution is used for the treatment of anemia. ... 

Partial to complete 3-0-octadecylated polysaccharides exhibited characteristic solution and solid properties based on hydrophilic-hydrophobic structures. These polymers are suggested to form micellar conformations in water and in chloroform polysaccharide-coated liposomes, polymeric membranes, and thermotropic liquid-crystalline mesophase, depending on the octadecyl content. Hydrolysis of 3-deoxygenat-ed, 3-0-methylated, and 3-0-octadecylated dextrans by an endo-acting dextrans is compared. The possibility of a combshaped branched polysaccharide toward cell-specific biomedical materials is discussed. 

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