Analytical Gel Isotachophoresis of Proteins With Carrier Ampholyte Spacers

An overview of about 100 years of bioanalysis is here disastrously attempted. The beginning of rigorous analytical systems can perhaps be traced back to the building and testing of the analytical ultracentrifuge by Svedberg and the apparatus for moving-boundary electrophoresis of Tiselius, both systems relying on expensive and hard to operate machines. In the sixties, Porath discovered porous beads for the determination of relative molecular mass (Mr) of proteins, based on the principle of molecular sieving. Concomitantly, Svensson and his pupil Vesterberg described a revolutionary principle for fractionating proteins in a nonisocratic environment, based on generation of stable pH gradients in an electric field, a technique that went down to history as isoelectric focusing (IEF). Polyacrylamide gel electrophoresis (PAGE), with the brilliant idea of discontinuous buffers, was brought to the limelight and in 1967, sodium dodecyl sulfate (SDS)-PAGE was described, permitting easy assessment of protein purity and reasonable measurements of Mr values of denatured polypeptide chains. By the mid seventies, another explosive concept was realized: orthogonal combination of two unrelated techniques, based on surface charge and mass fractionation, namely, two-dimensional (2-D) PAGE already in the very first papers by O'Farrell elaborated to its utmost sophistication. The eighties saw the systematic growth of 2-D PAGE, accompanied by systematic efforts to develop instrumentation for large-scale production of 2-D maps and computer evaluation for 2-D map analysis, based on the sophisticated algorithms adopted by astronomers for mapping stars in the sky. Another fundamental innovation in the field of IEF was the discovery of immobilized pH gradients (IPGs) that brought the much needed reproducibility in 2-D maps while allowing exquisite resolution in very narrow pH ranges. The nineties were definitely the decade of capillary zone electrophoresis, with the concomitant concept of automation and miniaturization in electrokinetic methodologies. Also 2-D map analysis witnessed a big revival, thanks to the adoption of IPGs for the first dimension. The enormous progress of mass spectrometry resulted in first reports on the analysis of macromolecules and the building of data bases on gene and protein banks. The third millennium is, perhaps, exasperating the concept of miniaturization at all costs, while not disdaining increasingly larger maps for 2-D analysis of complex protein mixtures.

Section: The Fabulous Seventiesmentioning

confidence: 99%

Bioanalysis: Its past, present, and some future

Righetti¹

2004

“…There have been other methods, described as early as 1970, in which counterflow was used in conjunction with ITP to allow time for isotachophoretic steps to become fully developed in a relatively short (10s of cm) capillaries 39–41, for automated isotachophoretic procedures on cellulose acetate membranes 42–44 or for improved concentration enhancement in coupled ITP‐CE methods 45–48. The use of ampholyte mixtures to form continuous conductivity gradients for ITP focusing and separation has also been described previously 49–54.…”

Section: Introductionmentioning

confidence: 99%

Chiral separation with gradient elution isotachophoresis for future in situ extraterrestrial analysis

Danger

Ross

2008

The first results of chiral separations with the gradient elution isotachophoresis method are presented. As previously described, citrate is used in the run buffer as the leading ion and borate in the sample buffer as the terminating ion. Modulation of parameters such as electrolyte pH, pressure scan rate, chiral selector concentration, combinations of CD or the percentage of ampholytes provides an easy optimization of the separations. To perform fluorescent detection 5-carboxyfluorescein succinimidyl ester and two fluorogenic-labeling agents, fluorescamine (Fluram) and 3-(4-carboxybenzoyl)quinoline-2-carboxaldehyde, are used to label amino acids. With the 5-carboxyfluorescein amino acids, chiral separations are easily obtained using a neutral CD ((2-hydroxypropyl)-beta-CD) at a low concentration (2 mmol/L). With Fluram amino acids, the situation is more complicated due to the formation of diastereoisomers and due to weak interactions with the different CDs used. The use of the 3-(4-carboxybenzoyl)quinoline-2-carboxaldehyde-labeling agent solves the problems observed with the Fluram agent while retaining the fluorogenic properties. These first results demonstrate the simplicity and the feasibility of gradient elution isotachophoresis for chiral separations.

Multiphasic electrophoresis with diversified spacers

Bringard¹,

Charlionet²

1990

The principle and some applications of multiphasic electrophoresis with diversified spacers are described. The method combines previously published concepts of introducing highly diversified spacers into the stack of an isotachophoretic system with the theory of snow- and telescope-electrophoresis. The link between this electrophoretic method and isotachophoresis on the one hand and monophasic zone electrophoresis on the other hand is exemplified. The importance of the nature of the spacers as well as of the pH and ions in the leading and terminating zone is illustrated. Details are given concerning the experimental set-up. This electrophoretic technique could serve as an alternative to isoelectric focusing.