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A new technique for preparing samples for matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) is reported. The technique relies on electrowetting-on-dielectric (EWOD) to move droplets containing proteins or peptides and matrix to specific locations on an array of electrodes for analysis. Standard MALDI-MS reagents, analytes,(More)
To realize multiplexed sample preparation on a digital microfluidic chip for high-throughput Matrix Assisted Laser Desorption/Ionization Mass Spectrometry (MALDI-MS), several fluidic functions need to be integrated. These include the generation of multiple droplets from a reservoir and parallel in-line sample purification. In this paper, we develop two(More)
An in-line sample purification method for MALDI-MS, which relies on the electrowetting-on-dielectric (EWOD)-based technique for digital microfluidics, is reported. In this method, a droplet containing peptides and impurities is moved by EWOD and deposited onto a Teflon-AF surface. A droplet of water is subsequently moved over the spot, where it dissolves(More)
In droplet-based ("digital") microfluidics, liquid droplets in contact with dielectric surfaces are created, moved, merged and mixed by applying AC or DC potentials across electrodes patterned beneath the dielectric. We show for the first time that it is possible to manipulate droplets of organic solvents, ionic liquids, and aqueous surfactant solutions in(More)
Natural tissues are composed of functionally diverse cell types that are organized in spatially complex arrangements. Organogenesis of complex tissues requires a coordinated sequential transformation process, with individual stages involving time-dependent expression of cell-cell, cell-matrix, and cell-signal interactions in three dimensions. The common(More)
The common blue marine mussel adheres to underwater surfaces using an adhesive protein (Mefp-1) extruded from its foot. This highly hydroxylated protein contains a number of unusual amino acids, including 3,4-dihydroxyphenylalanine (DOPA), which is thought to contribute to the crosslinking of the extruded threads and adhesion to the substratum. Mefp-1(More)
This article describes the equilibrium shape of a liquid drop under applied fields such as gravity and electrical fields, taking into account material properties such as dielectric constants, resistivities, and surface tension coefficients. The analysis is based on an energy minimization framework. A rigorous and exact link is provided between the energy(More)
The biological activity of proteins is structure dependent. In this discussion, we describe development of g-factor analysis for characterizing the secondary structure of proteins in solutions and films. In g-factor analysis, experimental circular dichroism (CD) and UV absorbance spectra are converted to dimensionless g-factor spectra by dividing the(More)
Surface enhanced Raman spectroscopy (SERS) was used to characterize a homologous series of alpha,omega-amino acids on colloidal gold and silver. Raman and SER spectra of the alpha,omega-amino acids, NH2(CH2)nCOOH (n = 3-7), are presented and analyzed, revealing the probable conformations of the molecules on the metal surfaces. The alpha,omega-amino acids(More)