Reproducibility of mobility in gel electrophoresis

A New Class of Phantom Materials for Poroelastography Imaging Techniques

Poroelastography is an elastographic technique used to image the temporal mechanical behavior of tissues. One of the major challenges in determining experimental potentials and limitations of this technique has been the lack of complex and realistic controlled phantoms that could be used to corroborate the limited number of theoretical and simulation studies available in the literature as well as to predict its performance in complex experimental situations and in a variety of conditions. In the study described here, we propose and analyze a new class of phantom materials for temporal elastography imaging. The results indicate that, by using polyacrylamide, we can generate inhomogeneous elastographic phantoms with controlled fluid content and fluid flow properties, while maintaining mechanical and ultrasonic properties similar to those of soft tissues.

Electrokinetic transport and separations in fluidic nanochannels

This article presents a summary of theory, experimental studies, and results for the electrokinetic transport in small fluidic nanochannels. The main focus is on the effect of the electric double layer on the EOF, electric current, and electrophoresis of charged analytes. The double layer thickness can be of the same order as the width of the nanochannels, which has an impact on the transport by shaping the fluid velocity profile, local distributions of the electrolytes, and charged analytes. Our theoretical consideration is limited to continuum analysis where the equations of classical hydrodynamics and electrodynamics still apply. We show that small channels may lead to qualitatively new effects like selective ionic transport based on charge number as well as different modes for molecular separation. These new possibilities together with the rapid development of nanofabrication capabilities lead to an extensive experimental effort to utilize nanochannels for a variety of applications, which are also discussed and analyzed in this review.

A new method for the preperative and analytical electrophoresis of cells

In this paper, a new method is described for the horizontal electrophoresis of cells on a density cushion under near-isopycnic conditions. When cell sedimentation is minimized, the electrophoresis of red blood cells (RBC) used as model cells within an anti-convective porous matrix (with pores over 300 μm in diameter) was capable of separating a mixture of human and chicken RBC according to their electrophoretic mobilities. Samples taken from the separated RBC bands show over 90% purity for each species. The simultaneous electrophoresis of several RBC samples carried out under identical conditions permitted the use of comparative data based on the electrophoretic mobility of cells which differ in their surface properties. We believe that this relatively simple system, in which cell sedimentation and convection are minimized, has the potential to be modified and adapted for the separation of other cell types/organelles.

Sequential electroelution and mass spectroscopic identification of intact sodium dodecyl sulfate-proteins labeled with 5(6)-carboxyfluorescein-N-hydroxysuccinimide ester

A gel electrophoresis apparatus capable of scanning the migration path fluorometrically and of computer-directed electroelution of bands was applied to the mass spectrometric identification of sequentially electroeluted 5(6)-carboxyfluorescein-N-hydrosuccinimide ester (FLUOS)-labeled sodium dodedyl sulfate (SDS)-proteins. The masses of four electroeluted SDS-proteins under study determined by matrix assisted laser desorption/ionization-time of flight (MALDI-TOF) spectrometry are changed by 1% due to their reaction with FLUOS in a 1:5 molar ratio of protein:label, allowing for the identification of the labeled intact proteins on the basis of mass. More importantly, the partial (10 or 50%) derivatization of proteins with FLUOS does not preclude their tryptic hydrolysis, and identification of the protein on the basis of the mass spectrometric analysis of its tryptic peptides. Potentially, the procedure allows for the automated mass spectrometric identification of SDS-proteins globally labeled with FLUOS and electrophoretically separated, without need for any gel sectioning.

Transfer of SDS-proteins from gel electrophoretic zones into mass spectrometry, using electroelution of the band into buffer without sectioning of the gel

Five SDS-proteins, ranging in molecular weight from 14 to 66 kDa, were detected without covalent fluorescent labeling by the automated gel electrophoresis apparatus with intermittent fluorescence scanning (HPGE apparatus, LabIntelligence) during electrophoresis in barbiturate buffer in the presence of Cascade Blue. The SDS-proteins were electroeluted from the gel into 220 microl of buffer by a modification of the procedure of Gombocz and Cortez. The electroeluate was freed of SDS, ultrafiltered and subjected to MALDI-TOF mass spectrometry. The masses of the five native proteins were found to be maintained after electrophoresis and electroelution in the presence of the potential contaminants SDS, barbituric acid and Cascade Blue. The procedure of protein transfer from SDS-PAGE into mass spectrometry, without excision of bands, gel maceration and protein recovery by diffusion, therefore is shown to be suitable for the identification by mass of intact proteins derived from gel electrophoretic bands.

The band areas of proteins determined by fluorescent scanning in the commercial automated gel electrophoresis apparatus

An automated gel electrophoresis apparatus, recently available commercially, allows one to follow the band during electrophoresis in real time, and lends itself therefore to an evaluation of bandwidth as a function of migration time (the dispersion coefficient), resolution and band shape. These determinations assume the constancy of band area with migration time and at various gel concentrations. The purpose of the present study was to verify these assumptions. Representative proteins and sodium dodecyl sulfate (SDS)-proteins, either natively fluorescent or fluorescein carboxylate labeled, were found to exhibit band areas which approach constancy as a function of migration time in both agarose and polyacrylamide gel electrophoresis, provided that (i) the protein concentration under the band was low enough to obviate self-quenching of fluorescence; (ii) the separation of the protein of interest from contaminants had progressed sufficiently during the time at which band areas were measured; (iii) the baseline under the peak was sufficiently well defined. However, band areas decrease with increasing gel concentration. Protein peaks exhibited leading and trailing tails. The ratio of the combined tail area to total area appeared to be near-constant at varying migration times. However, that ratio increases with increasing gel concentration. The tail area does not appear to be an artifact of fluorometric detection since it is reproduced upon fluorimetric analysis of the protein eluted from gel slices after electrophoresis. However, it may be due to photochemical destruction under the conditions of repetitive fluorometric peak detection.

Sodium dodecyl sulfate-agarose gel electrophoresis of urinary proteins: application to multiple myeloma

We evaluated a new sodium dodecyl sulfate-agarose gel electrophoresis (SDS-AGE) for urinary protein analysis in patients with multiple myeloma (MM; n = 47; ages, 62 ± 2 years, mean ± SE). Abnormal proteinuria (mean = 1872 ± 360 mg/24 h) was present in 95% of the samples; 75% of the patients had some sign of renal dysfunction (glomerular and/or tubular) according to their SDS-AGE pattern. A band suggesting Bence Jones proteinuria (BJP) was detected in 40 vs 33 specimens by routine AGE. Immunofixation identified BJP in 38 patients; the calculated sensitivity of SDS-AGE for BJP was 97%. Excellent correlation (P <0.0001) was obtained with routine AGE (r = 0.994) and immunonephelometry (r = 0.963) for light chain quantification. SDS-AGE allows easy evaluation of renal dysfunction and shows high sensitivity for BJP detection. In a specialized laboratory, it is useful for following the progress of MM patients through the semiquantification of BJP.

Improved sensitivity of detection with the commercial automated gel electrophoresis (HPGE-1000) apparatus through modification of its optical system

In a representative application to a fluorescently detectable protein of commercial automated gel electrophoresis apparatus (HPGE-1000, LabIntelligence, Belmont, CA) the sensitivity of detection by fluorescence was significantly increased by elimination of the mirror below the gel tray. That increase in detection sensitivity is due to a decrease of fluorescent background noise by nearly one order of magnitude, overcompensating a decrease in signal by a factor of two. The resulting increase in signal/noise ratio, i.e., detection sensitivity, should allow for lowered sample loads by which the band width is reduced with benefits to resolution.

Interpretation of electrophoretic band shapes by a partition chromatographic model

Measurements of the shape of electrophoretic bands of phycoerythrin and conalbumin have been made at regular intervals during migration in agarose gels. Analysis of the peak shapes suggests the existence of a significant degree of asymmetry. This is to be contrasted with the symmetry around the peak associated with the generally assumed Gaussian band. The degree of asymmetry of the bands decreased as a function of time and increased with agarose concentration. A similar experiment on DNA indicated constancy of the degree of asymmetry as a function of time. These results can be interpreted as, but do not prove the validity of, a nonlocal diffusion equation which generalizes a theory originally put forth by Giddings and Eyring (J. Am. Chem. Soc. 1955, 59, 416-420). The results may be significant in framing a measure of the resolvability of electrophoretic peaks.

Separation and isolation of subcellular-sized particles by electrophoresis in polymer solution using the commercial scanning apparatus

Electrophoresis of fluorescently labeled rat liver microsomes and polystyrene carboxylates of 10 and 30 nm radius was conducted in buffered 10-15% polyvinylpyrrolidone (M(r) = 10(6) solutions, using a horizontal gel electrophoresis apparatus with intermittent scanning of fluorescence (HPGE-1000, LabIntelligence). Banding, constant migration rates and Ferguson plots were obtained in these polymer solutions. The major microsome band detected by the automated scan was located visually on the gel by means of its fluorescein label and was isolated by volumetric withdrawal, recovery was monitored by scanning and ascertained to be near quantitative after three consecutive steps, in each of which 30 microL were withdrawn. This preparative method promises to be generally applicable to particles that are too large to enter into gels.