In this study we have determined whether Raman and infrared spectroscopy of blood plasma differentiates Alzheimer's disease (AD) from normal aging of healthy controls. Spectroscopic analysis was conducted on blood plasma samples from 8 mild AD, 16 moderate AD, 11 severe AD, and 12 normal elderly control persons using Fourier transform spectrometers and a near-infrared laser beam as excitation source for Raman spectroscopy. Spectra were processed employing discriminant analysis to determine whether band areas and frequency-intensity relationships might reveal biochemical differences associated with AD. Seven spectral biomarkers were identified in the Raman regions of 1700-1600 cm-1 (protein secondary structure), 980-910 cm-1 (protein α-helices), 790-730 cm-1 (protein tertiary structure), and 440-390 cm-1 (protein backbone) and in the infrared regions of 1700-1600 cm-1 (protein secondary structure) and 1150-1000 cm-1 (oxidative stress). This discriminant analysis model differentiated AD from normal aging of elderly control persons with a sensitivity of 89% and specificity of 92%. Moreover, specificity increases to 100% for the detection of mild AD. In summary, our results open the possibility of using this spectroscopic approach as a non-invasive, rapid, and relatively inexpensive procedure for early accurate diagnosis of AD.
Surface-enhanced Raman spectra of cytidine. and cytidine 5'-monophosphate adsorbed on copper and silver colloids were investigated. As an aid to the interpretation with regard to the metal-adsorbate binding sites, the normal Raman spectra of the complexes of these substances witb the metal ions were also obtained. The adsorption of the cytosine moiety in these substances occurs preferentially through the carbonyl bond, the pyrimidine ring adopting a non-planar orientation on tbe surface. However, in the complexes involving the metal ions the N-3 position is found to be the site through which the base interacts with these metals. The ribofuranose ring does not seem to participate significantly in the interaction of these substances with copper and silver in either the colloidal or ionic states.
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