title: On-chip isoelectric focusing using photopolymerized immobilized pH gradients.
abstract: We present the first successful adaptation of immobilized pH gradients (IPGs) to the microscale (muIPGs) using a new method for generating precisely defined polymer gradients on-chip. Gradients of monomer were established via diffusion along 6 mm flow-restricted channel segments. Precise control over boundary conditions and the resulting gradient is achieved by continuous flow of stock solutions through side channels flanking the gradient segment. Once the desired gradient is established, it is immobilized via photopolymerization. Precise gradient formation was verified with spatial and temporal detection of a fluorescent dye added to one of the flanking streams. Rapid (<20 min) isoelectric focusing of several fluorescent pI markers and proteins is demonstrated across pH 3.8-7.0 muIPGs using both denaturing and nondenaturing conditions, without the addition of carrier ampholytes. The muIPG format yields improved stability and comparable resolution to prominent on-chip IEF techniques. In addition to rapid, high-resolution separations, the reported muIPG format is amenable to multiplexed and multidimensional analysis via custom gradients as well as integration with other on-chip separation methods.
authors.affiliation: Biosystems Research Department, Sandia National Laboratories, Livermore, California 94551, USA.
authors.forename: Greg J
authors.initials: GJ
authors.lastname: Sommer
authors.forename: Anup K
authors.initials: AK
authors.lastname: Singh
authors.forename: Anson V
authors.initials: AV
authors.lastname: Hatch
mesh_terms: D000180:Acrylic Resins / Q000737:chemistry; D006863:Hydrogen-Ion Concentration; D007525:Isoelectric Focusing / Q000379:methods*; D008567:Membranes, Artificial; D046228:Microarray Analysis / Q000379:methods*; D010777:Photochemistry; D011506:Proteins / Q000302:isolation & purification*; D013050:Spectrometry, Fluorescence; D000099166:Polyacrylamides
chemical_list: D000180:Acrylic Resins; D008567:Membranes, Artificial; D011506:Proteins; D000099166:Polyacrylamides