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Picomolar limits of detection are obtained using the noncovalent, fluorogenic dye, Sypro Red. The size separation of four commonly used sodium dodecyl sulfate-capillary gel electrophoresis (SDS-CGE) molecular weight markers with 8% linear polyacrylamide (PAA) as the sieving matrix is used to construct a calibration curve for molecular weight determinations. SDS-CGE purity and molecular weight determination of purified chorismate mutase-prephenate dehydrogenase (CMPD) from Escherichia coli is shown to be comparable in accuracy with slab gel SDS-polyacrylamide gel electrophoresis (SDS-PAGE). A migration time precision study indicates excellent reproducibility. Sypro red labeling of SDS-bovine serum albumin (SDS-BSA) complexes at nanomolar protein concentrations suggests assay detection limits surpassing those of silver staining. This detectability exceeds that achieved in previous SDS-CGE laser-induced fluorescence studies. This approach is expected to be easily adapted for use with commercial polymer formulations and automated instrumentation.

There are currently no accepted blood-based biomarkers of sporadic Alzheimer's disease (AD). Augmented oxidative stress has been implicated in both neural and peripheral AD tissues. In this study, we determined whether short-wavelength near-infrared (NIR) spectrophotometry of blood plasma differentiates mild sporadic AD from normal aging. NIR analysis was conducted on 75 microl plasma samples from 19 AD, 27 amnestic MCI, and 17 normal elderly control (NEC) persons using an optical fiber-coupled, holographic grating-based NIR spectrograph. Five spectral bands associated with heme, R-CH, R-OH, H2O, and R-NH functional groups were sensitive to oxidative modification in pre-clinical studies and were pre-selected to develop a logistic regression model for sample classification. This model differentiated AD from NEC samples with a sensitivity of 80% and specificity of 77%. Fifteen and twelve MCI patients were classified with the NEC and AD groups, respectively. The spectra were not influenced by age, gender, exposure to cholinesterase inhibitors or vitamin E, or sample storage time. The NIR data further implicate oxidative stress in the systemic pathophysiology of sporadic AD and differentiate mild (and possibly pre-clinical) AD from NEC individuals with moderate-high accuracy. The procedure is minimally-invasive, rapid, relatively-inexpensive, and may provide a useful biological marker of sporadic AD.

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