Inner great rings

Figure 7. Inner great rings of natural macrocyclic ligand systems...

The polymer is about 0.8 nm in its maximum width and 0.33 nm2 in cross-sectional area, and can contain about 10,000 glucose residues with their rings in the same plane. In the cell wall these polymers are organized into micro-fibrils that can be 5 nm by 9 nm in cross section. These microfibrils apparently consist of an inner core of about 50 parallel chains of cellulose arranged in a crystalline array surrounded by a similar number of cellulose and other polymers in a paracrystalline array. Microfibrils are the basic unit of the cell wall and are readily observed in electron micrographs. Although great variation exists, they tend to be interwoven in the primary cell wall and parallel to each other in the secondary cell wall (Fig. 1-13). 

Though at first glance PN and PC show great similarity in their chemistry, their reactivity differs dramatically, which has been snbject of extensive investigations over the past decades and reflects itself in the inner phase chemistry of both species. For example, in solution PN ring-expands rapidly at room temperatme to 95 in the sub-nanosecond time scale, whereas ring-expansion of PC can only be observed at elevated temperatures in... 

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