Infrared spectra of human central nervous system tissue and human breast carcinoma are presented. The spectra are discussed in terms of the composition of the tissues. It is shown that differences between spectra of white and grey matter can be rationalised on the basis of differences in lipid content. Spectra of the choroid plexus and arachnoid villus of the meninges show a series of absorptions not observed in other CNS tissue. These absorptions are discussed in terms of the connective tissue content of the samples. We demonstrate that the presence of collagen results in the appearance of a series of characteristic absorptions which may be mis-assigned as DNA phosphate absorptions. The implications of the presence of collagen in tissues for the diagnosis of disease states by IR spectroscopic methods, with particular reference to cancer, is discussed.

We report the first evidence of the structure of beta-amyloid protein as it exists in situ within a slice of human Alzheimer's diseased brain tissue. Using a Fourier transform infrared microspectroscopic technique, areas of interest can be selected for spectral measurements with regions of potential contamination masked. In so doing, it is possible to obtain infrared spectra only of beta-amyloid and not the surrounding grey matter within which it lies. However, to obtain spectra of high-quality signal-to-noise ratio using a conventional infrared source, we were limited to aperture sizes between 24 microns x 24 microns to 50 microns x 50 microns. Markedly improved high-quality spectra were acquired with infrared radiation provided by a synchrotron light source (National Synchrotron Light Source, Brookhaven National Laboratories), using aperture sizes as small as 12 microns x 12 microns. This allowed spectroscopic mapping of brain tissue regions containing amyloid. We observe that in situ protein of grey matter exist predominantly in an alpha-helical and/or unordered conformation, whereas within amyloid deposits a beta-sheet structure predominates. The hydrogen bonding strength of the beta-structure found in situ is different from that reported in the literature for isolated/chemically synthesized beta-amyloid peptides.