Visualization of protein zones in preparative electrophoresis and carrier ampholyte zones on isoelectric focusing in gel slabs by two light refraction methods

Real-time monitoring of polyacrylamide gel electrophoresis by the shadowgraph technique

Polyacrylamide gel electrophoresis (PAGE) with sodium dodecyl sulphate (SDS) and Coomassie brilliant blue (CBB) staining is widely used in protein research and requires time for electrophoresis, staining and destaining. Because the protein bands electrophoresed in the gel are invisible in most cases, the results cannot be observed until the whole process is complete. In this study, shadowgraph was applied to detect biomolecules such as proteins during electrophoresis. A simple optical system and camera-enabled real-time monitoring of migration and separation of individual protein bands in polyacrylamide gels without staining. The visibility was high enough that it was possible to visualize substances other than proteins, such as DNA. This method provides protein profiles instantly in the early stage of electrophoresis. The elimination of the staining and destaining steps will help save researchers' time. The method is also environmentally friendly and will help reduce the generation of waste solutions containing synthetic dyes.

Mass distribution, polydispersity and focusing properties of carrier ampholytes for IEF II: pH 4–6 intervals

For studying the M(r) distribution and number of species in narrow-range (2 pH-unit wide, in the nominal pI 4-6 interval) carrier ampholytes from four commercial sources (Bio-Lyte, Servalyt, Ampholine and Pharmalyte), a 2-D technique was adopted consisting of a focusing step in a liquid phase (Rotofor, yielding 20 fractions) followed by orthogonal CE in both, acidic and basic buffers. As a final step, every other fraction was analyzed by CE-MS. The findings: Ampholine contains 80 different M(r) compounds, in the M(r) interval 203 to 893 Da, for a total of 325 isoforms. Bio-Lyte consists of 66 different M(r) species, in the M(r) range 388 to 835 Da, for a total of 436 isoforms. Servalyt is made of 199 different M(r) compounds, in the M(r) interval 204 to 907 Da, for a total of 1302 isoforms. Pharmalyte pH 4-6.5, comprises 217 amphoteres, in the M(r) range 150 to 1179 Da, for a total of 812 isoforms. Pharmalyte appears to be the best brand, with the vast majority of species focusing sharply at their pI position and <5% "poor" species, distributed along the entire pH gradient, denoting an extremely shallow pH/mobility curve across the pI value.

Real-time detection of DNA during gel electrophoresis using a Zeeman refractive index detector

We have developed a new method for detecting unstained, untagged, unlabeled DNA bands in real-time during gel electrophoresis. This technique is based on the use of a Zeeman refractive index detector with lambda/12,000 resolution and outstanding stability. Current sensitivity in a polyacrylamide gel is 0.2 ng of DNA in the probe beam. We believe this can be significantly improved. We don't understand why the DNA initially decreases, then dramatically increases, the local refractive index as it passes through the gel, although we propose three possible mechanisms.

Application of schlieren optics to real-time monitoring of protein electrophoresis in crosslinker-free linear polyacrylamide solution

Molecular sieving effect of crosslinker-free linear polyacrylamide solutions could be visualized in a real-time mode using schlieren optics for electrophoresis of proteins. Since linear polymer solutions are going to find application in capillary electrophoresis (Zhu, M., et al., J. Chromatogr. 1989, 480, 311-319), the above approach may be useful for obtaining basic data of electrophoresis of proteins and nucleic acids in such media under conditions free from the predominant wall effect pertinent to the use of a capillary.

The application of schlieren optics for detection of protein bands and other phenomena in polyacrylamide gel electrophoresis

A modernized schlieren optics system was applied to follow protein bands visually during polyacrylamide gel electrophoresis. This approach is suitable for quantitative measurement of electrophoresis as well as for detection of protein bands because of the absence of distortion of the electrophoretic pattern during the staining process. The optics are also suitable for the detection of various background phenomena which usually escape observation.

Protein hormones: detection and extraction of functional forms from alkaline polyacrylamide gels

A method is presented for rapidly staining zones (30 min) in alkaline polyacrylamide gels in the absence of fixatives. Native functional proteins are recovered in homogeneous form after excision of the visible zones from the polyacrylamide matrix. Removal of dye from excised zones is facilitated because only the surface of the gel is stained. Biological activity is then recovered from the gel slices by simple diffusion. The technique makes use of the sensitivity of Coomassie Brilliant Blue G-250 for the detection of proteins (less than 1 microgram). Structural variants of prolactin are isolated and recovered by this method. The method is applicable to studies requiring analytical and semi-preparative electrophoresis of proteins, especially pituitary hormones.

Visualization of carrier ampholyte patterns in granular gel slabs. 1. Applications to analytical electrofocusing

1. The isoelectric banding patterns of three commercial carrier ampholytes (pH range 2-11) were visualized in both Sephadex gel slabs and on paper prints, by means of ultraviolet light. 2. The fluorescence pattern of Servalyt is described in detail. This pattern, which has sharply delineated bands, is characteristic, and is reproducible from run to run with different batches of Servalyt. A total of 56 fluorescent bands were identified on gel slabs, and 62 on prints. 3. Methods are described for identifying individual fluorescent bands on prints. A classification scheme for organizing the banding pattern of Servalyt and naming individual bands is presented. 4. On gel slabs and on prints, the fluorescent pattern of a carrier ampholyte may be used analytically as a map for the location and identification of focused protein bands. The utility of the fluorescent pattern for characterising commercial ampholyte mixtures is discussed. 5. Individual fluorescent bands on the gel slab have characteristic pH values, which are constant from run to run and remain constant in the presence of focused sample proteins. On prints, these bands serve as permanent internal markers for assigning isoelectric points to protein bands.

Preparative gel electrophoresis: detection, excision, and elution of protein bands from unstained gels

Methods are described for localizing proteins in unstained gels and accurately excising the regions containing them. A gel elutor, which is all glass with Lucite fittings, is also described. The elutor removes proteins from gels with a high yield and concentrates the protein in a small volume. The elutor is simple and very easy to use. A way is presented for avoiding the oxidation of methionine and cysteine during preparative electrophoresis.

The instantaneous monitoring of polyacrylamide gels during electrophoresis

The advantages of being able to see protein zones in a gel during electrophoresis (and hence before staining) are pointed out, and a method is described which depends on local increments of refractive index in these zones. The use of local increments of refractive index in polyacrylamide gels for measuring protein concentrations in zones during electrophoresis is briefly considered; it is found that such increments are greater than would be expected from the amount of protein when sodium dodecyl sulphate is present. The enhancement depends on conditions and time of running. This makes quantitative estimates difficult, but the sensitivity of detection of protein zones by observations based on refractive-index changes is greatly increased by this property of sodium dodecyl sulphate. Methods are described for making optically uniform gels (both with uniform and with graded concentrations of polyacrylamide), necessary for observation of small changes in refractive index. A simple dark-field system of observation is described. Examples are given showing protein samples observed with the system during electrophoresis and compared with the same gel stained with Coomassie Blue after completion of the run. Under optimal conditions the optical method is comparable in sensitivity with staining. With the proteins of lower mol.wt. (approx. 15000), the optical method is not so sensitive, becoming less sensitive with longer running time. This loss of sensitivity is greatly decreased by using more concentrated polyacrylamide gels, and graded gels are therefore more suitable for optical observation than are uniform gels. The observation of protein zones during electrophoresis adds nothing to the time needed for making a stained gel and gives much information long before it can be obtained from the stained gel.