P-chitin

Zikakis, J.P. Chitin, Chitosan and Related Enzymes Academic Orlando, 1984. 

P-chitin can be extracted from the squid pen, which looks like a spine in the trunk. Squid P-chitin has a physical strength comparable to that of the conventional a-chitin. As seen in Table 23.1 (Takahashi, 2004), braking strain and... 

Takai, M., and Shimizu, Y. 1995. Squid P-chitin sheet laminated with salmon skin collagen as an artificial human skin. Report of the cooperative study on Development of functional membrane using marine bioresources collagen. Supported by grant in aid of Ministry of International Trade and Industry of Japan for Industrial-Academe cooperation, 20. 

Comparing the solubility behavior of a- and p-chitins (although the later exists in a crystalline-hydrated structure, which is much looser than that of the ot-chitin), p-chitin shows lower solubility due to the penetration of wafer between the chains of the lattice. Based upon chitin molecule-solvent conformation and solubility mechanisms, p-chitin starts gelling at a lower concentration than a-chitin. Table 2.6 illustrates the solubility of chifin and structurally related compounds in a saturated CaCl2 2H20-methanol solvent system. 

TABLE 2.6 Solubility of a- and p-chitins and structurally related compounds in a saturated CaCl2 2H20-methanol solvent system... 

FIGURE 2.9 The XRPD patterns of (A) a-chitin and chitosan of different molecular weights and (B) of a- and p-chitins. 

FIGURE 2.11 XRPD patterns for (A) p-chitin from different sources (1) cuttlefish pens and (2) squid pens, and (B) the corresponding chitosan. 

Vibration modes Wave number (cm a-Chitin P-Chitin... 

FIGURE 2.21 NMR solid-state spectra of (a) a-chitin from deproteinized lobster tendon, (b) p-chitin from dried deproteinized tube of Tevnia jerichonana. 

The N-acetyl-D-glucosamine moiety in both chitins can be considered as the magnetic independent residue in full agreement with the crystal structure of a- and p-chitin where this residue is also the crystallographic independent unit. Table 2.12 shows the similarity in a- and p-chitin NMR signals which means that solid-state NMR is not the appropriate technique to differentiate them. 

Assigned carbon atom Anhydrous p-chitin from diatom spines (ppm) a-Chitin from lobster tendon (ppm)... 

Due to the loose crystalline structure of p-chitin, it can be highly swollen in water by vigorous mixing using a suitable blender and forms a hydrogel. A suspension will be formed by the addition of excess water to the p-chitin hydrogel which is then filtered to form the p-chitm sheets. 

In Fig. 10, the N2 sorption isotherms of the aerogels of an alkali-gelled chitosan from p-chitin and the same chitosan gelled by TMP (2% molar cross-linker with respect to the number of amine groups) are compared. The aerogel of the... 

Transmission FT-IR spectroscopy has been used to monitor the deuteration by D2O vapor at room temperature of wafers of aerogels of chitosan from p-chitin... 

The dihedral angles about the glycosidic bonds in a-chitin were the same as those in p-chitin, " but in a-chitin there are two chitin chains in the unit cell. To account for an X-ray reflection which should not have been diffracted by crystals of the derived space group, it was proposed that the hydroxymethyl group was disordered. Subsequently, however, it was shown that this reflection was a double diffraction artefact. The detailed structure of a-chitin is therefore uncertain. 

Although described differently, a negative sign being placed before 6 in the a-chitin paper. If the sign in the p-chitin paper is correct, 6 se -143°, very close, as expected, to the figure for cellulose. 

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