Cell suberized

CELL WALL SUBERIZED WALL PLASMA MEMBRANE CYTOPLASM VACUOLE... 

Fig. 1. Schematic representation of the cuticle (top) and suberized cell wall (bottom)...

Suberin, being an adcrustation on the cell wall, cannot be separated from cell walls. Instead, suberin-enriched wall preparations can be obtained by digesting away as much carbohydrate polymers as possible using pectinases and cellu-lases [3,7]. Depending on the source of the suberized cell wall preparation, the polyester part may constitute a few percent to 30% of the total mass. 

Suberized cell walls stain positively for phenolics with indications that suberin contains monohydroxyphenolic rings and has fewer O-methoxy groups than lignin. 

Removal of the aliphatic materials by hydrogenolysis leaves a residue that contains low amounts of polymethylenic components, suggesting that the suberized material contains some aliphatic components not susceptible to cleavage by such methods [3]. On the other hand, removal of suberin from cork cell wall preparations was examined by CPMAS and the results showed that the aliphatic components were nearly completely removed from this suberin preparation as the spectra showed that the residual material was virtually devoid of methyl... 

Suberized cell walls are some of the last components of tree barks that remain after being buried in soil for years [135]. Fungi can penetrate suberized walls as... 

Figure 11.9 Pyrogram of a paint sample collected from sixteenth century wall paintings in the Messer Filippo cell of the tower in Spilamberto, Italy. Pyrolysis was performed with a micro furnace pyrolyser, at 600°C, in the presence of HMDS. 1, Carbohydrate pyrolysis products 2, lauric acid 3, suberic acid 4, levoglucosane 5, azelaic acid 6, miristic acid 7, hexadecanenitrile 8, palmitic acid 9, octadecanenitrile 10, oleic acid 11, stearic acid. TMS derivative [74]...

Montesano, L., Cawley, D., and Herschman, H.R. (1982) Disuccinimidyl suberate cross-linked ricin does not inhibit cell-free protein synthesis. Biochem. Biophys. Res. Comm. 109, 7-13. 

Cork cells Tabular with all walls suberized occur in thick layers on the outer surfaces of older stems and roots Secrete a fatty substance, suberin, into the walls, suberin renders cork cells waterproof and helps protect the tissues beneath... 

Apicomplexan parasites cause life threatening diseases like malaria, cryptosporid-iosis, toxoplasmosis, coccidiosis. Suberic acid bisdimethylamide which also inhibits HDA selechvely arrests tumor cells as opposed to normal mammalian cells, has an in vivo cytostatic effect against the acute murine malaria Plasmodium berghei (Andrews et al, 2000). 

High-resolution 13C NMR studies have been conducted on intact cuticles from limes, suberized cell walls from potatoes, and insoluble residues that remain after chemical depolymerization treatments of these materials. Identification and quantitation of the major functional moieties in cutin and suberin have been accomplished with cross-polarization magic-angle spinning as well as direct polarization methods. Evidence for polyester crosslinks and details of the interactions among polyester, wax, and cell-wall components have come from a variety of spin-relaxation measurements. Structural models for these protective plant biopolymers have been evaluated in light of the NMR results. 

Isolation of the Biopolyesters. Cutin was obtained from the skin of limes using published methods (8,9). The final solvent extractions were omitted in studies of cutin-wax interactions. Typically, 20 limes provided 800 mg of powdered polymer. Suberized cell walls were isolated from wound-healing potatoes after seven days of growth (10), with a yield of 4.5 g from 22 kg of potatoes. Chemical depolymerization of both polyesters was accomplished via transesterification with BF3/CH3OH (11). 

Suberized Cell Walls. An analogous set of CPMAS experiments is presented for suberin in Figure 6. Because this polymer is an integral part of the plant cell wall, the 13C NMR spectrum had contributions from both polysaccharide and polyester components. Chemical-shift assignments, summarized in Table IV, demonstrated the feasibility of identifying major polyester and sugar moieties despite serious spectral overlap. Semiquantitative estimates for the various carbon types indicated that, as compared with cutin, the suberin polyester had dramatically fewer aliphatic and more aromatic residues. A similar observation was made previously for the soluble depolymerization products of these plant polymers (1,8,11). 

Figure 6. 31.94 MHz 13C NMR spectra for suberized cell walls from potatoes, before (bottom) and after (top) depolymerization treatment. The experimental parameters were as in Figure 4. Chemical-shift assignments and relative numbers of carbons for the untreated material are found in Table IV. Delayed-decoupling experiments left some (CH2) signal intensity in the spectrum of intact suberin, but the analogous signals were drastically attenuated in the NMR spectrum of the depolymerization residue.

Table IV. Carbon Types in Suberized Cell Walls...

For the study of complex cuticular mixtures, measurements of cross-polarization dynamics proved to be especially informative. The equality of Ti/>(H) values in cutin-wax assemblies demonstrated that these cuticular materials were mixed intimately. By contrast, Ti >(H) measurements showed that the polymeric components of suberized cell walls were present in distinct domains, suggesting that suberin was attached at a few structural sites rather than being embedded in the polysaccharide wall. 

Figure 1. Structural responses of the bark of Picea sitchensis to wounding and inoculation with Phaeolus schweinUzii. IW, inoculated wound SP, surface periderm NT, necrotic tissue TC, thickened cells SIT, relic of suberized impervious tissue NP, necrophylactic periderm P, phloem VC, vascular cambium.

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