The Williams Group|
Study abroad, Monash University,
Australia, July - November 2004 (biomaterials, macromolecules, smart
materials and Synthesis of
Current research has focused in different areas of non-traditional approaches with polystyrene (Mw=826 Daltons) and polyethylene glycol (Mw=700 Daltons). In these approaches, the use of MALDI sample stages (stainless steel and gold) and metal substrates (i.e. copper, aluminum, and brass) have been utilized with a cationizing agent to promote desorption/cationization of low molecular weight polymers. The use of these metal substrates has significantly improved the quality of the mass spectrum below 1000 Daltons yielding better polymer analysis. Currently, work is being done looking at the platinum series of metal as substrates with and without organic matrix.
In addition to using different metal substrates, the use of gold
nanoparticles has also been investigated. Using different sized gold
nanoparticles may yield more accurate molecular weight information for
polymer analysis for different polymer weights. The use of gold
nanoparticles, like the metal substrates, significantly improves the
mass spectrum below 1000 Daltons compared with the traditional organic
matrix, with a limited number of random mass being detected.
Starches are important macromolecules with many industrial applications, particularly in the food and pharmaceutical industries. Their uses range from gelling agents to drug transport and even energy storage. Properties of starches vary based on the plant or bacterial source and are connected to the amylose and amylopectin content. Amylose is a linear polysaccharide with α-1,4 glycoside bonds and has a molecular weight around 106 Daltons. Amylopectin is a highly branched polysaccharide with α-1,6 glycoside bonds along a α-1,4 glycoside bond chain backbone and has a molecular weight around 107 Daltons .
Characterization of starch has previously been performed using size-exclusion chromatography (SEC). The use of SEC for polysaccharides is limited due to low exclusion limits of the packed column and shear degradation of the ultrahigh molecular weight components. An alternative to SEC is field-flow fractionation (FFF). In 1994, Lou et al. reported the use of thermal FFF (ThFFF) to perform the separation of pullulan with varying molecular weight and of corn starch with varying amylose and amylopectin content . ThFFF uses a temperature field applied perpendicular to the carrier liquid flow to promote the retention and fractionation of analytes based on the ratio of thermal diffusion coefficient DT to normal diffusion coefficient D. The retention time tr of the analyte is therefore controlled by the temperature difference across the channel DT, the size and molecular weight of the analyte, and parameters that affect DT.
In the past decade, flow FFF has been in the spotlight with respect to polysaccharides analyses [3-5] using an aqueous carrier liquid. Separation of polysaccharides of starches by flow FFF is based solely on the hydrodynamic size of the macromolecule whereas ThFFF has additional composition sensitivity.
Richardson, S.; Gorton, L. Anal. Chim. Acta. 497, 27-65
Justin R. Engle
and S. Kim R. Williams. “Gold Nanoparticles as an Inorganic Matrix for
Justin R. Engle
and S. Kim R. Williams. “Non-Traditional Approaches to MALDI-TOF Mass
Justin R. Engle
and S. Kim R. Williams. “Fractionation of Industrial Starch
Justin R. Engle,
J. Ray Runyon, and S. Kim R. Williams. “Nontraditional Matrices for