A A C C   2 0 0 0   A n n u a l   M e e t i n g

Spatial resolution achievable with synchrotron infrared microspectroscopy was used for highly localized in situ chemical analysis. Mapping along a line with 3 micron steps that corresponds to the beam size permits identification of chemical distinction between adjacent targets in the microscope field of view. Under conventional (thermal) source FT-IR microspectroscopy such distinctions are diluted and obscured by contributions to an average spectrum from the larger targeted area. Data obtained by line mapping from just below the aleurone layer into the central endosperm for a collection of wheat is presented. From the individual spectra obtained the chemical compositional heterogeneity within the wheat section is revealed. Previous large mask mapping within the same botanical part (e.g. central endosperm of corn) showed uneven distribution of lipid even from interpolated representative mapping points. Subsequent 100% mapping with a 6 micron × 6 micron mask showed lipid heterogeneity in endosperm on a smaller scale. With a 3 micron beam the chemisty of a single protein body or a narrow cell wall can be probed even though the predominant content of the specimen in the field of view may be starch. Data obtained from similar 3 micron × 3 micron mapping of a model system involving biological tissue that has a layered structure serves as a goal for future high spatial resolution synchrotron infrared microspectroscopy experiments.