Parameterizing amylose chain-length distributions for biosynthesis-structure-property relations
Amylose, one of the components of starch, is a glucose polymer consisting largely of long, linear chains with a few long-chain branch points. The chain-length (molecular weight) distribution (CLD) of the component chains of amylose can provide information on amylose biosynthesis-structure-property relations, as has been done previously by fitting amylopectin CLDs to a model with physically meaningful parameters. Due to the presence of long chains, the CLD of amylose can currently best be obtained by size-exclusion chromatography, a technique that suffers from band-broadening effects which alter the observed distribution. The features of the multiple regions present in amylose chain-length distributions are also difficult to resolve, an issue that combines with band broadening to compound the difficulty of analysis and subsequent parameterization of the structural characteristics of amylose. A new method is presented to fit these distributions with biologically meaningful parameters in a way that accounts for band broadening. This is achieved by assuming that band broadening takes the form of a simple Gaussian over a relatively small region and that chain stoppage is a random process independent of the length of the substrate chain over the same region; these assumptions are relatively weak and expected to be frequently applicable. The method provides inbuilt consistency tests for its applicability to a given data set and, in cases where it is applicable, allows for the first nonempirical parameterization of amylose biosynthesis-structure-property relations from CLDs by using parameters directly linked to the activities of the enzymes responsible for chain growth and chain stoppage.
Publisher URL: https://link.springer.com/article/10.1007/s00216-017-0639-5