Infrared spectroscopic imaging is widely used for the
visualization
of biomolecule structures, and techniques such as optical photothermal
infrared (OPTIR) microspectroscopy can achieve <500 nm spatial
resolution. However, these approaches lack specificity for particular
cell types and cell components and thus cannot be used as a stand-alone
technique to assess their properties. Here, we have developed a novel
tool, fluorescently guided optical photothermal infrared microspectroscopy,
that simultaneously exploits epifluorescence imaging and OPTIR to
perform fluorescently guided IR spectroscopic analysis. This novel
approach exceeds the diffraction limit of infrared microscopy and
allows structural analysis of specific proteins directly in tissue
and single cells. Experiments described herein used epifluorescence
to rapidly locate amyloid proteins in tissues or neuronal cultures,
thus guiding OPTIR measurements to assess amyloid structures at the
subcellular level. We believe that this new approach will be a valuable
addition to infrared spectroscopy providing cellular specificity of
measurements in complex systems for studies of structurally altered
protein aggregates
