Selective silver staining of urease activity in polyacrylamide gels

A selective method for staining urease activity bands in nondenaturing polyacrylamide gels is described. It is based on the deposition of silver at the urease bands after incubation of gels in the presence of urea and photographic developers. Its highly sensitivity (up to 0.015 enzyme units, corresponding to 5 ng of purified urease) is based on both the silver deposition enhancement methodology and the developers used. The selectivity of the procedure is based on the local pH increase catalytically produced by the enzyme in the presence of urea. The densitometric scan of the enzyme bands gives a linear response at least in the range 0.015-0.300 urease units. This selective staining method is about 2.5 times more sensitive than the standard silver staining of proteins, in terms of detectable urease amount.     

Eosin Y staining of proteins in polyacrylamide gels.

A staining method is described in which various proteins in polyacrylamide gels can be stained by using eosin Y. After a brief incubation of a polyacrylamide gel in an acidic solution of 1% eosin Y, various proteins, including human erythrocyte membrane sialoglycoproteins which are not detectable by Coomassie blue R-250 (CB), can be detected with a sensitivity of 10 ng protein. This is far more sensitive than CB staining and is comparable to the sensitivity of silver staining. In a Western blot, the antigenicity of an eosin Y stained protein is retained. In addition, proteins on an immunoblot sheet can be detected by eosin Y staining. The method described is rapid, sensitive, and reproducible with various proteins in polyacrylamide gels and has the added advantage of also staining sialoglycoproteins.     

A method for the direct measurement of glycogen synthase activity on gels after polyacrylamide gel electrophoresis

A method for the detection of glycogen synthase activity after nondenaturing polyacrylamide gel electrophoresis is described. After the electrophoretical run, the gels were incubated in situ with UDP-glucose and glycogen. Labeled or unlabeled UDP-glucose could be used, since similar activity patterns were obtained by autoradiography or iodine staining of the gels. The method here described offers several advantages in terms of speed, sensitivity, and economy when compared with other procedures.     

Simultaneous staining of proteins during polyacrylamide gel electrophoresis in acidic gels by countermigration of Coomassie brilliant blue R-250

A method for the simultaneous staining of proteins during polyacrylamide gel electrophoresis with Coomassie brilliant blue R-250 at pH 2.5 is described. Calf thymus whole histone and cytochrome c were stained by this method and the results obtained were similar to that obtained by staining after electrophoresis.     

Native gel activity stain and preparative electrophoretic method for the detection and purification of pyridine nucleotide-linked dehydrogenases

An activity stain for the detection of pyridine nucleotide-linked dehydrogenases in polyacrylamide gels is described. Following incubation of the gel with substrate and cofactor, bands are visualized under ultraviolet light, where reduced cofactors fluoresce and oxidized cofactors appear black. The methods described are useful for any NAD- or NADP-linked dehydrogenase; the enzymes can be assayed in either the oxidative or the reductive direction. Also described is a preparative polyacrylamide gel system using the activity stain, which can be used as a general purification method for dehydrogenases. The preparative gels are crosslinked with bisacrylylcystamine. These crosslinks can be broken by the addition of thiols after the bands of interest have been located and excised. The protein of interest is then separated from the solubilized acrylamide by adsorption to a suitable resin.     

Crossed immunoelectrophoresis from sodium dodecyl sulfate-polyacrylamide gels after fixation and staining and without nonionic detergent intermediate layers

A modified method is described for crossed immunoelectrophoresis in which the first-dimension separation has been carried out by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The described method does not require nonionic detergents and is carried out after fixation and staining of the polyacrylamide gel. This permits more precise alignment of immunoprecipitates with polypeptide bands as well as allowing direct testing of an individual polypeptide band for reaction with antibody.     

Improved zymographic detection of bovine acrosin.

Acrosomal materials extracted from bovine spermatozoa contain a trypsin-like proteinase termed acrosin (1–3) (EC 3.4.21.10). The presence of multiple molecular forms of this spermatozoal enzyme has been demonstrated both by gel filtration (2) and by polyacrylamide gel electrophoresis (1,3).The enzymic reactions of proteinases can be detected in electrophoretic patterns by incorporating proteinaceous substrates in the electrophoretic media (4) or by using specific amino acid derivatives of β-naphthylamine (1,5,6). Andary and Dabich (6) recently reported that the former method was improved by diffusing the proteinaceous substrate into the gel during a 1-hr incubation period following electrophoresis. The zymogram then required an additional incubation of the gel in buffer solution for 2–12 hr before the transparent zones of proteinase activity were detectable. Incubation periods of less than 1 hr are normally required for the zymographic staining methods that use synthetic arginine derivatives of β-napthylamine to detect acrosin activity. These systems do, however, suffer from a lack of sensitivity and fading of the diazonium-coupled product (1). An improved method for rapid detection of acrosin activity in gels would, therefore, be useful. The present communication describes an improved version of the staining system for detecting acrosin activity using a synthetic arginine derivative of β-naphthylamine. The application of this staining system for the detection of the multiple forms of bovine acrosin is presented. In addition, the stability of the zymograms resulting from three different coupling dyes was investigated using a miniature polyacrylamide gel electrophoretic system.     

Detection of cellulase activity in polyacrylamide gels using Congo red-stained agar replicas

Bands that have cellulolytic activity are visualized after polyacrylamide gel electrophoresis by laying the slab gel on top of a thin sheet of 2% agar containing 0.1% carboxymethylcellulose. After a suitable incubation time, zones of carboxymethylcellulose hydrolysis are revealed by staining the agar replica with Congo red.     

Detection of elastase activity with a zymogram method after isoelectric focusing in polyacrylamide gel

A zymogram method for detecting elastase activity following isoelectric focusing in polyacrylamide gel is described. After enzyme activity has been visualized, the gel itself is available for protein staining and for analysis in sodium dodecyl sulfate-polyacrylamide gel electrophoresis in second dimension. The zymogram method is suitable for detecting microgram amounts of elastase and has one step only. It can be used with the purified enzyme as well as with crude extracts of tissue containing elastases showing activity toward succinyl-(Ala)₃-p-nitroanilide. By this method a major component of elastase in both porcine and rat pancreas was detected. In addition, two forms of elastase with isoelectric points of 8.2 and 8.8, respectively, were identified in rat leukocyte extracts.     

Alcian blue staining of proteoglycans in polyacrylamide gels using the "critical electrolyte concentration" approach

A method is described here for Alcian blue staining of proteoglycans in polyacrylamide gels; this is illustrated using extracts obtained from bovine corneal stroma. Other available methods for visualization of proteoglycans can produce nonspecific staining and frequently a high background in the gel; with a "critical electrolyte concentration" approach, specific staining against a clear background can be obtained.     

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.     

Improved method for ribonuclease zymogram

An improved method for ribonuclease zymogram in agarose overlays is described which enables significantly enhanced sensitivity and the avoidance of false-positive activity. Two critical aspects of the zymogram method—the fixation/staining technique and the RNA substrate concentration—were evaluated for the RNase activity in RNase A and in human serum and urine. The zymogram method is sensitive to at least 10 pg of RNase A and does not show a false-positive reaction from 1500 μg of non-RNase protein following electrophoresis in thin-layer polyacrylamide gel.     

Highly purified agarose as stacking gel in sodium dodecyl sulphate/polyacrylamide-gel electrophoresis.

A modified sodium dodecyl sulphage/polyacrylamide-gel-electrophoretic method is described that utilizes highly purified agarose as stacking gel. The same electrophoretic resolution of different marker proteins is found as when polyacrylamide is used as stacking gel, but the background staining seen when polyacrylamide is used as stacking gel is decreased.     

Purification and molecular properties of rabbit liver esterase ES-1A

1. The isolation of esterase ES-1A from rabbit liver microsomes/lysosomes is reported. The purification as measured by methylbutyrate-hydrolysing activity, was about 27-fold with a recovery of 2.4%. 2. The resulting product is apparently homogeneous by polyacrylamide (gradient) gel electrophoresis and sodium dodecyl sulphate/polyacrylamide gradient gel electrophoresis after protein staining. The enzyme exhibits heterogeneity after staining for esterase activity and in isoelectric focusing. 3. The molecular mass of the native protein was found to be about 183 kDa (determined by gel filtration and polyacrylamide gel electrophoresis) with a subunit mass of about 63 kDa, indicating a trimeric structure of the enzyme, with subunits of equal size. 4. ES-1A is a glycoprotein and is classified as a carboxylesterase (EC 3.1.1.1). 5. The high degree of similarity of the properties of rabbit ES-1A with those of mouse ES-6A and rat ES-10 suggests that these three esterases may have a common evolutionary origin.     

Identification of proteins according to biological activity following separation by two-dimensional isoelectric focusing/sodium dodecyl sulfate gel electrophoresis: analysis of human exocrine pancreatic proteins

A novel procedure is described whereby proteins can be identified according to their biological activity after their separation in two dimensions using isoelectric focusing and polyacrylamide gel electrophoresis in sodium dodecyl sulfate (G. Scheele, 1975, J. Biol. Chem., 250, 5375–5385). This procedure includes an optimal staining method for the visualization of two-dimensional gel spots, which avoids the use of chemical fixatives, and a one-step method for elution and renaturation of proteins. Fifteen out of the twenty discrete proteins separated from human pancreatic juice by the two-dimensional gel method were successfully identified by this procedure.     

Enzyme crystal embedded in latex film as immobilized enzyme

Summary A simple and effective method for enzyme crystals immobilization is developed. The water- based acrylic latex mixed with enzyme crystals is coated on a porous membrane. When dried, the latex produces a continuous and strong film in which enzyme crystals are embedded. Latex of three different compositions are synthesized to immobilize urease. The urease crystals embedded in latex film shows a good thermal stability that the activity remains at 60% of its initial activity after 5 days' incubation at 50°C. The film containing amorphous urease powder, on the other hand, has a very poor thermal stability that urease activity decreases to 50% and 3% of its initial activity after 8 hrs' and 3 days' incubation, respectively. The diffusion limitation in the lattices of urease crystal is the main reason for the low activity retention of urease crystals embedded in the latex film.     

Effects of molecular oxygen on detection of superoxide radical with nitroblue tetrazolium and on activity stains for catalase

The usual method of staining polyacrylamide gel electropherograms for superoxide dismutase activity utilizes a photochemical flux of O2- to reduce nitroblue tetrazolium. Superoxide dismutases intercept O2-, preventing formazan production and thus causing achromatic bands. In the presence of H2O2, catalases also yield achromatic bands during this staining procedure. This is due to local elevation of pO2 by the catalatic decomposition of H2O2. O2, in turn, inhibits the reduction of the tetrazolium by O2-. This phenomenon provides a new activity stain for catalase. A previously described activity stain for catalase has also been reexamined and significantly improved.     

In-gel detection of urease with nitroblue tetrazolium and quantification of the enzyme from different crop plants using the indophenol reaction

Two methods for measurement of urease activity are described and demonstrated on extracts from several crop plants. With an in-gel staining method based on the principle of Fishbein's noninhibitory stain for urease as little as 25 microU of jackbean urease can be detected within 2 h following electrophoresis. A comparison with published in-gel staining methods shows that the sensitivity is improved by at least two orders of magnitude. The second method allows quantification of urease activity from small amounts of plant material without the need for special laboratory equipment. It employs the detection of ammonium by the indophenol reaction. To eliminate reducing agents which are often necessary to maintain urease activity during extraction, but which interfere with ammonium detection, a simple spin-column procedure is used. The quantification of less than 5 mU/ml extract is possible.     

Detection of chitinase activity after polyacrylamide gel electrophoresis

Commercial Streptomyces griseus and Serratia marcescens chitinases and purified wheat germ W1A and hen egg white lysozymes were subjected to polyacrylamide gel electrophoresis under native conditions at pH 4.3. After electrophoresis, an overlay gel containing 0.01% (W/V) glycol chitin as substrate was incubated in contact with the separation gel. Lytic zones were revealed by uv illumination with a transilluminator after staining for 5 min with 0.01% (W/V) Calcofluor white M2R. As low as 500 ng of purified hen egg lysozyme could be detected after 1 h incubation at 37 degrees C. One band was observed with W1A lysozyme and several bands with the commercial microbial chitinases. The same system was also used with native polyacrylamide gel electrophoresis at pH 8.9. Several bands were detected with the microbial chitinases. The same enzymes were also subjected to denaturing polyacrylamide gel electrophoresis in gradient gels containing 0.01% (W/V) glycol chitin. After electrophoresis, enzymes were renatured in buffered 1% (V/V) purified Triton X-100. Lytic zones were revealed by uv after staining with Calcofluor white M2R as for native gels. The molecular weights of chitinolytic enzymes could thus be directly estimated. In denaturing gels, as low as 10 ng of purified hen egg white lysozyme could be detected after 2 h incubation at 37 degrees C. Estimated molecular weights of St. griseus and Se. marcescens were between 24,000 and 72,000 and between 40,500 and 73,000, respectively. Some microbial chitinases were only resistant to denaturation with sodium dodecyl sulfate while others were resistant to sodium dodecyl sulfate and beta-mercaptoethanol.     

Structure and possible ureide degrading function of the ubiquitous urease of soybean

Ubiquitous soybean urease, as opposed to the seed-specific urease, designates the seemingly identical ureolytic activities of suspension cultures and leaves. It also appears to be the basal urease in developing seeds of a variety, Itachi, which lacks the seed-specific urease (Polacco, Winkler 1984 Plant Physiol 74: 800-804). On native polyacrylamide gels the ureolytic activities in crude extracts of these three tissues comigrate as determined by assays of gel slices. At this level of resolution the ubiquitous urease also migrates with or close to the fast (trimeric) form of the seed-specific urease.

The ubiquitous urease was purified approximately 100-fold from suspension cultures of two cultivars (Itachi and Prize) as well as from developing seeds of Itachi. These partially purified preparations allowed visualization of native urease on polyacrylamide gels by activity staining and of urease subunits on denaturing lithium dodecyl sulfate gels by electrophoretic transfer to nitrocellulose and immunological detection (“Western Blot”). The ubiquitous urease holoenzyme migrates slightly less rapidly than the fast seed urease in native gels; its subunit migrates slightly less rapidly than the 93.5 kilodaltons subunit of either the fast or slow (hexameric) seed enzyme. The ubiquitous urease elutes from an agarose A-0.5 meter column with the fast form of the seed urease species suggesting that the ubiquitous urease, like the fast seed urease, exists as a trimeric holoenzyme. The soybean cultivar, Prize, produces the hexameric seed urease; yet its ubiquitous urease (from leaf and suspension culture) is trimeric.

The pH dependence of the ureolytic activity of seed coats of both seed urease-negative (Itachi) and seed urease-positive (Williams) cultivars suggests that this activity is exclusively the ubiquitous urease. Its relatively higher levels in seed coats than in embryos of Itachi suggests that the ubiquitous urease is involved in degradation of urea derived from ureides. Consistent with a ureide origin for urea is the observation that addition of a urease inhibitor, phenylphosphordiamidate, to extracts of developing Itachi seeds (seed coat plus embryo) results in accumulation of urea from allantoic acid.