Characterization and supramolecular architecture of the cellulose‐protein fibrils in the tunic of the sea peach (Halocynthia papillosa, Ascidiacea, Urochordata)

Abstract

The cellulose-protein fibrils, which constitute by far the bulk of the fibrous fraction of the sea peach tunic (Halocynthia papillosa), were structurally and chemically characterized, either in situ or after extraction procedures, with the use of classical electron microscopy combined with diffraction contrast imaging and electron diffraction, histochemistry, affinity cytochemistry and chemical analysis. These fibrils exhibit a cross-sectional shape close to a parallelogram. The crystallites forming their core, with lateral dimensions ranging from roughly 5 to 20 nm, are composed of native cellulose of higher crystallinity than that of plant cellulose. They are associated with acid mucopolysaccharid~s (amps) and proteins which form a coating material appearing as a continuous sheath enveloping the axial crystallite in the cuticular layer or as patches more-or-less periodically distributed around and along the fibre axis in the fundamental layer. Tunicin, the alkali-insoluble fibrous fraction, is not pure cellulose, yielding only 22-60% of its dry weight as glucose equivalents, depending on the tunical layer. It is suggested that in addition to the high degree of crystallinity of the tunical cellulose, the presence of a significant amount of coating material composed of amino acids and proteoglycans firmly linked to cellulose molecules contributes to tunicin's high resistance to hydrolysis.

TEMPO-mediated surface oxidation of cellulose whiskers

“…Thus, we can conclude that the TEMPO-mediated oxidation conditions that were used here do not have further hydrolytic treatment on the whiskers, whose lengths are determined by the initial hydrolytic treatment. Regarding the whisker width and their distribution, they are essentially close to those observed in the initial tunicate mantle (Van Daele et al 1992). Therefore, neither the hydrolytic treatment, nor the surface oxidation seems to have any thinning effect on the tunicin whiskers, in contrast with other solid-state treatments such as acetylation (Sassi and Chanzy 1995) or enzymatic digestion (Chanzy and Henrissat 1983).…”

“…The tunicin whiskers have the section of truncated lozenges (Helbert et al 1998) that for simplification can be modeled as rectangles with average dimensions of long and short sides, respectively, L = 18.2 nm and l = 8.8 nm (Van Daele et al 1992;Terech et al 1999). In Figure 2, we show the representation of a model whisker and its orientation with respect to the section of the unit cell of cellulose Ib and its two lattice parameters a = 0.801 nm and b = 0.817 nm (Sugiyama et al 1991).…”

High-resolution electron microscopy on ultrathin sections of cellulose microfibrils generated by glomerulocytes in Polyzoa vesiculiphora

“…These bundles are randomly deposited on the tunic so as to give the analogue of "randomly oriented plywood" appearance. This makes it technically difficult to align the microfibrils and visualize their precise cross-sectional shapes: the only successful images obtained to date came from Halocynthia papillosa (Revol et al 1990, Daele et al 1992. Interestingly, these authors found a unique parallelogram which prompted us to speculate on the difference in the mode of crystallization between Ia-and Io-rich cellulose microfibrils.…”

Soluble and film-forming cellulose derivatives with redox- chromogenic and enzyme immobilizing 1,4-phenylenediamine groups

“…Among the macromolecular supports used so far in biosensors, cellulose structures provide the best prerequisites because of polyfunctionality, supramolecular structure forming potential and due to their hydrophilic and biocompatible properties 1) . Examples may be found in nature too where linkages between cellulose or other polysaccharides with proteins, e. g., supramolecular structures of collagen or elastin and cellulose or polysaccharide-protein structures in the case of glycoproteins, lead to a stabilization of the protein conformation 2,3) . The aim of our structural design studies consists in a novel type of cellulose derivatives corresponding to the above requirements of a transducer building block.…”