Carrageenans spectra

The algal polysaccharides resembled the relatively simplified structures of tile neutral mucilages, as in the case of carrageenan A wider spectrum of struclures is found in Ihc bacterial gums, which arc generally of the highly branched type exuded by higher plants,... 

Rg. 2. The 13C NMR spectrum of a K-co-hybrid carrageenan G4S-DA + G6S-DA from Phyllophora nervosa (adapted from ref. 408). 

Rees and coworkers (41) have shown that in the i-carrageenan gel at 15° the segmental motion of all portions of the double helix form is so little that the resulting T2 s are too low for signal observation. On increase of temperature the gel dissociates so that a normal n.m.r. spectrum is obtained (Fig. 20). 

The FTIR spectrum of K-carrageenan (Figure 31.17) is specific in the fingerprint region from 1350 to 800 cm . Apart from alginate, the peak at 1604 cm in less intense, specifically, in... 

Carrageenan, 113, 354 dielectric spectrum, 375 phase transition, 374 Cascade theory, 125 CASING, 20, 108-9 Catalytic polymerization, 102 Cell membrane complex (CMC), 147 Cellulose derivatives, 137 Characterization techniques, 172-412 see also specific techrriques Chemical bonding, 14, 16 Chemical ctosslinking, 106 Chemical gels, 15, 16, 138, 140, 353 Chemical reactions, 104-6 Chemical shift, conformation dependent, 282 C-hordein, 288... 

Figure 13 CD spectrum of (—) methyl / -o-galactopyrarioside, ( ) carrageenan and (—) agarose. Redrawn with permission from data in Arndt ER and Stevens ES (1993) J. Am. Chem. Soc. 116 7849-7853, Copyright (1993) American Chemical Society, Arndt ER and Stevens ES (1994) Biopolymers 34 1527-1534 and Stevens ES and Morris ER (1990) Carbohydr. Polym. 12 219-224.

In 0.03 molL KCI, i-cairageenan (c. 3 gL" ), forms a very tenuous gel network on cooling to 4°C, as can be appreciated from the mechanical spectrum displayed in Figure 13a. There is overall predominance of G over G but a clear dependence of both moduli with . However, in the NPEC with CHI-20 (Z = 0.084) under identical conditions, gelation of i-carrageenan at 4°C was completely suppressed (Fig. 13b). Whether the transition of i-carrageenan is shifted to yet lower temperature or else was inhibited completely, cannot be established conclusively at this stage. 

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