Microscale fractionation facilitates detection of differentially expressed proteins in Alzheimer's disease brain samples.

Fractionation enhances the resolution of proteins with similar characteristics by reducing the number of proteins that comigrate in gels, thus facilitating the detection of lower-abundance proteins and the accurate determination of quantitative and qualitative differences in disease and normal samples. An efficient, reproducible microscale fractionation protocol for complex protein mixtures using novel ion-exchange membrane chromatographic substrates (PerkinElmer, Boston, MA, USA; Vivascience, Carlsbad, CA, USA) is described. The fractionation techniques were used in combination with two-dimensional (2-D) gels and orthogonal matrix-assisted laser desorption/ ionization-time of flight (MALDI-TOF) mass spectrometry to identify differentially expressed proteins in brain samples from persons with and without Alzheimer's disease.