Sensitive silver staining of proteins after isoelectric focusing in agarose gels

Pectinolytic Enzymes from Actinomycetes for the Degumming of Ramie Bast Fibers

Actinomycetes isolated from 10 different soil and compost samples were screened for production of pectinolytic enzyme activities when grown on pectin-containing solid and liquid media. Pectinolytic enzymes, detected by using plate diffusion tests with a medium containing ramie ( Boehmeria nivea ) plant material as the sole carbon source, were mainly pectate lyases, but low activities of pectinesterases were also observed. Polygalacturonases and polymethylgalacturonases were not produced. Multiple forms of pectate lyases were detected in the culture supernatants of some of the strains by using the zymogram technique of isoelectric focusing gels. Xylanolytic and cellulolytic activities were always found to be associated with pectinolytic activities. None of the pectinolytic enzymes were produced in a medium with glucose as the sole carbon source. Treatment of ramie bast fibers with crude enzyme preparations from a selection of strains showed a good correlation between the pectate lyase activity applied and the degumming effect, resulting in good separation of the bast fibers.

Specific, sensitive and accurate quantification of albumin, retinol binding protein and transferrin in human urine and serum by zone immunoelectrophoresis assay (ZIA)

For zone immunoelectrophoresis assay (ZIA) glass tubes, ID 2 mm and 90 mm high, are filled to 2/3 with buffer containing agarose and antibodies against the protein to be quantified, each sample being pipetted on top of separate agarose gel rods. On electrophoresis at 35-150 V for several hours, the sample proteins enter the gel with resultant immunoprecipitates, visualized by staining. The extension of each immunoprecipitation zone from the upper gel surface (measured with a ruler) is directly proportional to the amount of protein in each sample and can easily be quantitated by comparison with a linear calibration curve. ZIA can be used for quantification of several proteins in blood serum and plasma as well as in urine, as is illustrated for albumin, retinol-binding protein (RBP) and transferrin. The recovery of the pure proteins added to urine is often close to 100%. ZIA has many advantages: (i) simple apparatus and procedure (no gel punching nor cooling), (ii) minimal antiserum consumption (1 mL may allow > 1000 assays), (iii) electrophoresis can be performed within a few hours or overnight, (iv) low coefficient of variation (often < 4%), (v) linear calibration curves, (vi) low detection limit (< 20 ng/mL), (vii) wide concentration ranges, (viii) no kits nor unique antisera preparation are required, and (ix) good agreement with the results from other methods.

A simple modification of Blum's silver stain method allows for 30 minute detection of proteins in polyacrylamide gels

A simple and rapid protocol for silver staining of proteins following electrophoresis in polyacrylamide gels (PAGE) is described. We have reduced the number of steps in the procedure of Blum et al. (Electrophoresis (1987) 8, 93-99), and shortened fixation and washing times so that efficient detection of proteins can be achieved within 30 min. In common with more time-consuming silver-staining methods, the present protocol is capable of detecting nanogram quantities of proteins on a colorless background and is suitable for rapid screening of large numbers of samples.

A short history of electrophoretic methods

High resolution separation of proteins, based on charge differences, is possible with disc electrophoresis, displacement electrophoresis (isotachophoresis) and notably isoelectric focusing (IEF). Size separation is obtained in sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). The combination of gel IEF, followed by SDS-PAGE in a second-dimensional slab gel, i.e. two-dimensional gel electrophoresis, affords the highest resolution with up to several thousand spots per gel. Staining of proteins gives high resolution patterns which can be scanned and stored in comprehensive databases. Over the last 10 years the electrophoretic separation in gels and subsequent visualization of nucleic acids (DNA, RNA) and even genes as well as nucleotides have been much improved, making possible efficient mapping of the genes in humans and all other organisms. This has led to the biggest concerted endeavor in the history of science, i.e. the mapping of the human genome, which will be of importance as long as mankind exists. In the last years electrophoresis in capillaries has attracted much interest because for numerous substances, such as proteins nucleic acids, pharmaceuticals, metabolites, and peptides, it offers high resolution on the analytical scale with over 1 million theoretical plates. Electrophoretic methods have unprecedented impact on life sciences, providing a basis for unique advances in biochemistry, molecular biology, genetics, gene technology and medicine.

Identification of host-protective antigens of Taenia ovis oncospheres

Sheep were fully protected against challenge infection following immunization with a homogenate of T. ovis oncospheres. Ultracentrifugation of sonicated oncospheres either alone or in the presence of a range of detergents did not reduce the immunogenicity of the extracts. Solubilization of oncosphere extracts in non-ionic detergents or sodium dodecyl sulphate (SDS) enabled analysis of host-protective antigens by isoelectric focusing (IEF) and electrophoresis in polyacrylamide gels (SDS-PAGE), respectively. Immunoblotting analysis of oncosphere antigens with immune sheep sera identified predominantly two groups of antigens with relative mobilities of 31-34 kDa and 47-52 kDa with a common isoelectric point of 5.8. The immunogenicity of these antigens was confirmed in vaccination trials using appropriate fractions cut from SDS-PAGE gels and agarose IEF gels. Affinity-purified antibodies prepared against the candidate antigens were used to select the corresponding recombinant DNA-derived polypeptides, one of which was subsequently found to be host-protective.

Purification and characterization of an intracellular peroxidase from Streptomyces cyaneus

An intracellular peroxidase (EC 1.11.1.7) from Streptomyces cyaneus was purified to homogeneity. The enzyme had a molecular weight of 185,000 and was composed of two subunits of equal size. It had an isoelectric point of 6.1. The enzyme had a peroxidase activity toward o-dianisidine with a Km of 17.8 microM and a pH optimum of 5.0. It also showed catalase activity with a Km of 2.07 mM H2O2 and a pH optimum of 8.0. The purified enzyme did not catalyze C alpha-C beta bond cleavage of 1,3-dihydroxy-2-(2-methoxyphenoxy)-1-(4-ethoxy-3-methoxyphenyl) propane, a nonphenolic dimeric lignin model compound. The spectrum of the peroxidase showed a soret band at 405 nm, which disappeared after reduction with sodium dithionite, indicating that the enzyme is a hemoprotein. Testing the effects of various inhibitors on the enzyme activity showed that it is a bifunctional enzyme having catalase and peroxidase activities.

Purification and properties of an aryl-alcohol dehydrogenase from the white-rot fungus Phanerochaete chrysosporium

An intracellular aryl-alcohol dehydrogenase (previously referred to as aryl-aldehyde reductase) was purified from the white-rot fungus Phanerochaete chrysosporium. The enzyme reduced veratraldehyde to veratryl alcohol using NADPH as a cofactor. Other aromatic benzaldehydes were also reduced, but not aromatic ketones. Methoxy-substituted rings were better substrates than hydroxylated ones. The enzyme was also able to reduce a dimeric aldehyde (4-benzyloxy-3-methoxybenzaldehyde). The highest reduction rate was measured when 3,5-dimethoxybenzaldehyde was used as a substrate. On SDS/PAGE the purified enzyme showed one major band with a molecular mass of 47 kDa, whereas gel filtration suggested a molecular mass of 280 kDa. Polyclonal antibodies raised against the gel purified 47-kDa protein were able to immunoprecipitate the aryl-alcohol dehydrogenase indicating that its activity possibly resides entirely in this protein fragment. The pI of the enzyme was 5.2 and it was most active at pH 6.1. The aryl-alcohol dehydrogenase was partially inhibited by typical oxidoreductase inhibitors.

Improved detection of lymphocyte membrane proteins in purified form and as a crude mixture using native and denaturing polyacrylamide gel electrophoresis by optimisation of coomassie brilliant blue and silver staining

Optimised silver staining protocols were devised for the detection of membrane proteins in purified form and as a crude mixture. These were adduced in both sodium dodecyl sulphate (SDS) and native polyacrylamide gel electrophoresis and consisted of ethanol-acetic acid-formaldehyde fixation, Coomassie Brilliant Blue prestaining, Rapidfix pretreatment, formaldehyde enhancement and finally ammoniacal silver staining. With these modifications, numerous staining problems of membrane proteins were overcome. These included reduction in background staining, enhanced detection sensitivity in native gels, elimination of negative staining and the avoidance of metallic silver deposition on the gel surface. In overcoming these problems, some factors determining the colour and stainability of membrane proteins in their native state were determined. Both the anionic Coomassie Brilliant Blue dye and SDS detergent improved the sensitivity of silver staining in native gels, and ammoniacal silver was more sensitive than neutral silver, suggesting silver staining to be a charge dependent process.

Porphobilinogen deaminase in human erythrocytes: purification of two forms with apparent molecular weights of 40 kDa and 42 kDa

Porphobilinogen deaminase was purified from human erythrocytes by ion-exchange chromatography, gel filtration and hydrophobic interaction chromatography. Two forms of the enzyme were isolated, with apparent molecular weights of 40 kDa and 42 kDa, and in relative amounts of 85% and 15%, respectively. Both forms were found to have an N-terminal amino acid sequence identical to that published for the erythropoietic form of porphobilinogen deaminase, as deduced from a cDNA clone. The two forms present could each be separated into three differently charged subforms by Mono Q chromatography.

History of electrophoretic methods

Electrophoresis is the migration of electrically charged particles or ions in solutions due to an applied electric field. The ability to separate very similar substances including different proteins for analytical and preparative purposes has increased, especially since 1950, owing to the introduction of zone electrophoresis in paper and later in gels of polyacrylamide or agarose. After 1960, disc and displacement electrophoresis (isotachophoresis) and isoelectric focusing offered much increased resolution. Electrophoretic methods nowadays promote advances in biochemistry and molecular biology and will continue to be very important in science and for numerous applications in genetics, gene technology, sequencing of nucleic acids and proteins, studies of diseases and malfunctions including cancer, and in the identification of species and individuals, e.g., in forensic medicine.

Isolation of dimeric forms of human pituitary growth hormone

A procedure is described which for the first time allows the isolation of noncovalently-linked dimeric human pituitary growth hormone. Isomers of this dimeric species were prepared as were also, for the first time, isomers of covalently-linked dimers. Chromatography on DEAE-Sepharose CL-6B revealed the existence of noncovalently-linked dimers composed of monomers of 22K hGH, 20K hGH and 20K1 hGH (the latter is a new form of 20K hGH with a scission in the peptide chain) and covalent dimers containing 22K hGH and 24K hGH (the latter a 22K hGH with a scission). The different dimers all occurred as charge isomers and subsequent HPLC on an anion exchanger followed by zone electrophoresis in agarose suspension made possible the isolation of four noncovalently-linked isomers: one form of (20K-20K)hGH, two forms of (20K-22K)hGH and one form of (22K-22K)hGH; and of three covalently-linked isomers: one form of (22K-22K)hGH and two forms of (22K-24K)hGH.

Isolation of four isomers of the 20,000 dalton variant of human pituitary growth hormone

A simple procedure has been developed which for the first time describes the isolation of isomers of the 20,000 dalton variant of human growth hormone (20K hGH). From a human pituitary hormone concentrate different hGH dimers (covalently and noncovalently linked) were enriched by chromatography on SP-Sephadex C-50, DEAE-Sepharose CL-6B and Sephadex G-100. Noncovalently-linked dimers were split by 6 M urea into 20K hGH and 22K hGH monomers. A complete group-separation of 20K hGH and 22K hGH monomers was achieved by chromatography on DEAE-Sepharose CL-6B at neutral pH. The 20K hGH monomer was resolved into four isomers either by preparative isoelectric focusing or by zone electrophoresis in agarose suspension at alkaline pH. The three latter techniques were all used in the presence of 6 M urea. Radioimmunoassay and radioreceptorassay indicated that the isomers obtained were true components of human growth hormone.

Biological characterization of purified native 20-kDa human growth hormone

Because of the propensity of the 20-kDa variant of human growth hormone (GH) to aggregate with itself and with 22-kDa human GH, it has been difficult to prepare monomeric 20-kDa GH in highly purified form. This has been a major complicating factor in determining whether 20-kDa GH has a biological activity profile distinct from that of 22-kDa GH. In the present study, native 20-kDa GH was isolated from a human GH dimer concentrate and purified by a procedure that included column electrophoresis in agarose suspension as a final separation step. This procedure yielded highly purified monomeric 20-kDa GH, which was contaminated to an extent of less than 1% with 22-kDa GH, and which exhibited only a small degree of dimerization upon storage. The native 20-kDa GH was quite active in stimulating growth in hypophysectomized rats, when growth was assessed by body weight gain, longitudinal bone growth, the stimulation of sulfation of cartilage, and the elevation of serum IGF-1 level. However, in all of these growth assays, the 20-kDa GH was somewhat less active than the native 22-kDa GH to which it was compared; e.g., in the body weight gain and longitudinal bone growth assays, it had an estimated potency of 0.6 relative to the 22-kDa GH. The 20-kDa GH exhibited substantial diabetogenic activity when tested for the ability to raise fasting blood glucose concentration and to impair glucose tolerance in ob/ob mice. Also, the native 20-kDa GH had significant in vitro insulin-like activity, although its potency was approximately 20% that of the native 22-kDa GH to which it was compared. Thus, the biological activity profile of native 20-kDa GH differs from that of 22-kDa GH primarily in that insulin-like activity is markedly attenuated.

Discomfort from rubber gloves indicating contact urticaria

Rubber glove intolerance is a common dermatological problem and hypersensitivity of both delayed and immediate types occur. In order to study immediate skin reactions induced by rubber gloves, 15 patients with discomfort and itch produced by rubber gloves were examined. The patients were provoked by wearing rubber gloves, scratch tested with gloves, rubber chemicals and powders. RAST-tests were performed using an extract from the rubber tree (Hevea brasiliensis). In 6/15 patients, contact urticaria was confirmed, in 3 of whom IgE antibodies to latex were demonstrated.

Detection of oligoclonal IgG bands in unconcentrated CSF by isoelectric focusing in agarose gel and silver staining

We analyzed 102 unconcentrated cerebrospinal fluids from a variety of neurologic diseases for oligoclonal IgG bands by isoelectric focusing in agarose gel followed by staining with silver. Ten to 12 microliter of cerebrospinal fluid containing 0.4-0.8 microgram of IgG was found to be optimum. Cerebrospinal fluid from 38 of 40 patients with clinically definite multiple sclerosis, 6 of 9 with suspected multiple sclerosis and 8 of 53 patients with other neurologic diseases had oligoclonal IgG bands by IEF in agarose followed by immunofixation. The commercial system employed here is a simple sensitive and rapid method for detection of oligoclonal bands in unconcentrated cerebrospinal fluid of patients with multiple sclerosis.

Agarose isoelectric focusing, antiserum immunofixation and silver staining for detection of oligoclonal bands in unconcentrated cerebrospinal fluid

Unconcentrated cerebrospinal fluid (CSF) and corresponding serum from 30 patients with multiple sclerosis (MS), 30 with other neurological disease and 30 controls suffering from tension headache or psychoneurosis, were examined for oligoclonal IgG bands by initial separation employing agarose isoelectric focusing (AIF) followed by a modified procedure of immunofixation with monospecific antiserum and silver staining. This method is specific for demonstration of IgG and has a limit for detection of 0.4 microgram of IgG. Comparing the results with those obtained by AIF followed by capillary blotting to nitrocellulose membrane, double antibody peroxidase labeling and avidin-biotin amplification, both methods revealed similar frequencies of positive findings for oligoclonal IgG bands in the three patient groups. AIF followed by antiserum immunofixation and silver staining is a simple, sensitive and specific method for detection of oligoclonal IgG in unconcentrated CSF.