Designed Polymer Architectures
Introduction to Pectin
While pectin is essentially a linear co-polymer of galacturonic acid and its methylesterified counterpart, it is arguably one of the most complex of the plant cell polysaccharides. This complexity, manifest in a host of possible fine structure variants, gives pectin its utility of function and, combined with its horde of accompanying enzymes in-vivo , its ability to respond to a myriad of environmentally triggered stimuli. More generally, any process capable of modifying pectin's molecular level polymeric characteristics, such as the molar mass, the degree and distribution of methylesterification, amidation, acetylation, or ferulic acid substitution, and the content, length and distribution of neutral sugar side-chains, may yield a tangible change in it's manifest properties.
The large degree of possible structural variation endows pectin molecules with a rich and varied interaction space where hydrogen bonding, hydrophobic type interactions, polyelectrolytic behaviour, specific ionic interactions, and even covalent coupling can all play a possible role in determining behaviour. To date, we have been primarily interested in how the inter- and intra-molecular distributions of methylesterification affects the pectin functionality, as stressed in the basic structure shown (See Box). Ultimately, the control of the methylesterification of these homogalacturonan regions can be used to control the interaction between chains. We want, therefore, to understand how to use different chain architectures, to allow us to build designed soft materials, as Nature does. In general structure-function relationships are difficult to elucidate in-vivo, owing to the difficulty of selectively measuring polymeric fine structure in-situ or removing biopolymeric material, without modifying its fine structure, while still retaining information on its location and interactions within the host biomaterial. We have therefore concentrated on developing an in-vitro approach.
Towards Controlled Polymer Achitectures
We are currently engineering polymer samples with distinct degrees and patterns of methylesterification, using chemical and enzymatic methodologies. These involve the use of fungal and plant pectinmethylesterases. We are also investigating novel methods for the molecular engineering of controlled fine structures. Such work relies heavily on our ability to measure generated inter and intra-molecular distributions of methylesterification.