-----------------------------------------------------------------------
                                           BIOINFORMATICS COLLOQUIUM
					       College of Science
                                            George Mason University
                       -----------------------------------------------------------------------

			        Analysis of 2D Gels: Global and Region-based Approaches					
	
 				
				 	    Francoise Seillier-Moiseiwitsch
						
					  Georgetown University Medical Center

Abstract:

Two-dimensional polyacrylamide gel electrophoresis is currently one of
the techniques of choice to separate and display all the proteins expressed in
a tissue. In the resulting protein maps for groups of patients, we seek to 
identify proteins that are differentially expressed.  I will describe a 
comprehensive analytical approach that deals with preprocessing, alignment 
and differential analysis. Preprocessing removes the bulk of the background 
noise. It involves smoothing, selecting regions containing spots and gradient thresholding.
Images are aligned using cubic-spline transformations. The alignment is formulated as a 
quadratic programming problem that is optimized using an interior-point method. In the 
global approach, wavelets are utilized to summarize the aligned images, and statistical 
tests performed on the wavelet coefficients. In the region-based approach, the images 
are segmented using the watershed algorithm and summary statistics are computed on each 
region. Statistical tests are applied to these summary statistics.