The use of Tween 20 as a blocking agent in the immunological detection of proteins transferred to nitrocellulose membranes

Western immunoblotting: temperature-dependent reduction in background staining

The effect of incubation temperature on the background staining of Western blots with monoclonal antibodies to a human milk protein, alpha-lactalbumin (Mr 14,500), is presented. Human milk proteins were electrophoretically separated and transferred to nitrocellulose membranes which were then blocked with bovine serum albumin, "BLOTTO", casein, or Tween 20. They were subsequently incubated with mouse monoclonal antibody to human alpha-lactalbumin, biotinylated anti-mouse antibody, strepavidin-biotinylated horseradish peroxidase complexes and a substrate containing diaminobenzidine and nickel chloride. Reduction of incubation temperature from 37 degrees C to 22 degrees C and 4 degrees C was found to decrease the extent of non-specific background staining independent of the type of blocking reagent used. Good specific staining with minimal background was found using 0.1% Tween 20 in phosphate-buffered saline, pH 7.2, as blocking agent and incubation temperatures of 4 degrees C.

Sodium dodecyl sulfate enhancement of quantitative immunoenzyme dot-blot assays on nitrocellulose

Treating proteins with low concentrations of sodium dodecyl sulfate (SDS) and boiling for 2-3 min increased the linear range and total amount of protein that could be bound to nitrocellulose. Human serum albumin (HSA) and cathepsin G (Cat G) were both optimally bound at an SDS concentration of 10 micrograms/ml, while bronchial leukocyte proteinase inhibitor (BLPI) required 50 micrograms/ml SDS for optimum binding, corresponding to SDS-to-protein weight ratios of 0.5 and 2.5, respectively. Ionic strength and pH of the blotting buffers had a greater effect on the binding of SDS-treated proteins than on native proteins, with the linear binding range and total capacity for SDS-treated proteins being increased. Boiling SDS-treated human leukocyte extracts inactivated endogenous peroxidases, eliminating their interference with peroxidase-linked secondary antibodies in immunoassays. The nonionic detergents, Tween 20 and Nonidet P-40, were shown to rapidly wash both native and SDS-treated HSA off the filters, but these HSA samples were stable to washing with SDS. Although SDS-treated Cat G was more stable with nonionic detergents than was native Cat G, it was less resistant to washing with SDS. The substitution of SDS for nonionic detergents improved the response of immunoassays with native and SDS-treated proteins. Affinity-purified antibodies to human mast cell tryptase cross-reacted with native Cat G, but not with SDS-treated Cat G, indicating that SDS treatment can improve the specificity of immunoassays employing polyclonal antisera. These effects appear to be the result of partial denaturation and increases in the hydrophobicity of SDS-treated relative to native proteins.

An immunoblot assay for the simultaneous quantification of several antigens

A radioimmunologic assay method that allows for the simultaneous quantification of several antigens in one sample is described. Polypeptide antigens are resolved electrophoretically and electroblotted to nitrocellulose. The nitrocellulose is then reacted with a mixture of several antisera simultaneously, and antibody-binding proteins are visualized by incubation with 125I-protein A and by autoradiography. Antigens are identified according to their molecular weights and quantified by counting the bound radioactivity. The sensitivity of the assay is in the low nanogram range and can be adjusted individually for each antigen by appropriately diluting the first antiserum. The procedure is presently applied to the detection of three neural antigens, neural cell adhesion molecule, neuron-specific enolase, and synaptophysin, in adult brain tissue and to the assessment of expression of the latter two during development of brain cells in primary culture. The method is fast, comparatively cheap, and associated with a low radiation exposure. It should prove especially useful when only scarce amounts of sample are available.

A blocking agent and a blocking step are not needed in ELISA, immunostaining dot-blots and western blots

The effect of blocking and non-blocking was compared in ELISA, immunostaining dot-blots and western blots using phosphate-buffered saline with and without the addition of Tween 20 for washes and dilutions. The results indicated that when Tween 20 was included in phosphate-buffered saline, a blocking agent and a blocking step were not required in immunoassays. Moreover, the use of protein-based blocking agents was found to somewhat lower the reactivity between the antibody and the antigen, possibly due to steric hindrance.

Differences in phorbol-ester-induced down-regulation of protein kinase C between cell lines

Down-regulation of protein kinase C induced by 12-O-tetradecanoylphorbol 13-acetate (TPA) was examined in Swiss 3T3, V79, MDBK and C6 cells by Western blotting. Variations in the rate of down-regulation caused by treatment with 100 nM-TPA were observed; TPA treatment for 5 h caused maximal down-regulation in V79 cells, whereas TPA treatment for 10 h or 30 h was needed for maximal down-regulation of protein kinase C in MDBK or Swiss 3T3 cells respectively. The decrease in amount of immunologically detectable protein kinase C was 30% in MDBK cells and 100% in V79 and Swiss 3T3 cells. MDBK and C6 cells could be completely depleted of protein kinase C by treatment with 250 nM-TPA. In C6 cells, after treatment with 500 nM-TPA, an 80% loss of protein kinase C was seen over 10 h. Measurement of the numbers of phorbol-ester-binding sites remaining in each cell line when protein kinase C was maximally down-regulated indicated that in MDBK and Swiss 3T3 cells loss of phorbol-ester-binding sites paralleled loss of protein kinase C, whereas in V79 and C6 cells no such correlation was observed.

Structural analysis of hemolymph proteins from Schistosoma mansoni (Trematoda)-susceptible and resistant Biomphalaria glabrata (Gastropoda)

1. Five different molecular weight polypeptides from serum (cell-free hemolymph) of Schistosoma mansoni-resistant and susceptible strains of Biomphalaria glabrata, were examined by two-dimensional 125I-peptide mapping and high performance liquid chromatography (HPLC). 2. Peptide mapping indicated that all five radiolabeled polypeptides within and between the two snail strains had similar migration patterns when cleaved with pepsin or alpha-chymotrypsin, thus revealing a shared structural homology. All peptides chosen for analysis appeared to be structurally similar to the 160 kDa hemoglobin molecule. 3. Separations of the radiolabeled enzyme digests by HPLC confirmed results seen in the mapping experiments since all chromatograms had similar elution patterns. 4. Minor differences in the peptide maps and chromatograms within and between snail strains may be due to quantitative differences in the amount of protein present and/or variations in the primary amino acid sequences of the proteins chosen for analysis.

The response of individual polypeptides of the mammalian respiratory chain to thyroid hormone

The effects of thyroid hormone on the accumulation of inner membrane polypeptides in rat liver mitochondria have been investigated using Western blot analysis. Respiration and mitochondrial protein synthesis were also measured. Levels of the subunits of cytochrome oxidase, the cytochrome bc1 complex, and the beta-subunit of F1-ATPase increase relatively late, requiring 3-6 days of treatment and high doses of hormone. In contrast, respiration increases under conditions in which no significant accumulation of individual subunits is observed. Our results indicate that increased oxidative capacity of mitochondria can be divided into an early response which probably involves metabolic regulation of mitochondrial respiration by hormone and a later response which is due to elevated mitochondrial protein synthesis and the accumulation of polypeptides of the respiratory chain.

Comparison of dot enzyme-linked immunosorbent assay (Dot-ELISA), passive haemagglutination test (PHT) and thin layer immunoassay (TIA) in the diagnosis of natural or experimental Fasciola hepatica infections in sheep

The dot enzyme-linked immunosorbent assay (Dot-ELISA) was compared with the passive haemagglutination test (PHT) and thin layer immunoassay (TIA) for the detection of antibodies against Fasciola hepatica in naturally and experimentally infected sheep. The infected animals gave titres from 1:25,000 to 1:204,000, while control animals gave titres of from 1:100 to 1:800. The titres of the infected sheep obtained by Dot-ELISA were 1000-2000 times higher than the ones obtained using TIA or PHT. Due to its high sensitivity, this technique could be very useful for the diagnosis of ovine fascioliasis.

Indirect immunofluorescence localization of ponticulin in motile cells

Ponticulin is the major actin-binding integral glycoprotein in plasma membranes isolated from log-phase Dictyostelium discoideum amebae. As such, this protein appears to be an important link between the plasma membrane and actin filaments (Wuestehube and Luna: Journal of Cell Biology 105:1741-1751, 1987). In this study, indirect immunofluorescence microscopy was used to examine the distribution of ponticulin in randomly moving D. discoideum amebae and in amebae engaged in cell migration and phagocytosis. Ponticulin is distributed throughout the plasma membrane and also is present in intracellular vesicles associated with the microtubule-organizing center-Golgi complex adjacent to the nucleus. In aggregating amebae, ponticulin is concentrated in regions of lateral cell-cell contact and in arched regions of the plasma membrane. Ponticulin also is present, but not obviously enriched, in filopodia, in the actin-rich anterior end of polarized cells, and in detergent-insoluble cytoskeletons. In amebae engaged in phagocytosis of yeast, ponticulin is present but not enriched in phagocytic cups and is associated with intracellular vesicles around engulfed yeast. These results suggest that ponticulin is stably associated with actin filaments in certain regions of the plasma membrane and that the actin-binding activity of ponticulin may be tightly controlled. Indirect immunofluorescence microscopy and immunoblot analysis demonstrate that human polymorphonuclear leukocytes also contain a 17 kD protein that specifically cross-reacts with antibodies affinity-purified against D. discoideum ponticulin. As in D. discoideum, the mammalian 17 kD ponticulin-analog appears to be localized in plasma membrane and is evident in actin-rich cell extensions. These results indicate that ponticulin-mediated linkages between the plasma membrane and actin may be present in higher eukaryotic cells.

Immunoblotting techniques with picogram sensitivity in cerebrospinal fluid protein detection

Agarose isoelectric focusing followed by blotting with nitrocellulose, nylon or polyvinylidene difluoride membranes, and immunochemical detection of cerebrospinal fluid IgG with various combinations of antisera, was evaluated. Polyvinylidene difluoride proved to be an easy-to-handle and reliable membrane for protein blotting. Among immunochemical visualization reactions, the most sensitive employed biotinylated goat anti-human IgG followed by streptavidin colloidal gold conjugate and silver enhancement in 20% w/v urea, allowing a sensitivity of less then 1 picogram IgG/band.

Monoclonal antibodies against spore antigens of Bacillus anthracis

A murine monoclonal antibody produced against heat inactivated spores of Bacillus anthracis Ames, reacted with live or inactivated spores of several anthrax strains in indirect immunofluorescence (IF) tests. The reactive anthrax strain gave only a moderate degree of reaction. No staining of anthrax vegetative cells was observed. The monoclonal did not react with spores of non-anthrax Bacillus strains that gave cross reactions with mouse hyperimmune antiserum raised against Ames spores. The staining of individual spores in B. anthracis preparations was more heterogeneous with the monoclonal antibody than with the hyperimmune serum. Evidence is produced that the epitope for this monoclonal is not stable during long-term storage of inactivated spore preparations, and is not fully available for reaction with antibody until late in spore maturation. The monoclonal did not react by immunoblotting (Western blotting) of spore extracts. A monoclonal antibody produced against Ames spore extracts reacted with about 1% of Ames spores in IF tests, but not reproducible reactions with other anthrax strains were recorded. This monoclonal interacted with three bands in Western blots of anthrax spore extracts.

Dystrophin and nebulin in the muscular dystrophies

Skeletal muscle from patients with 5 different forms of muscular dystrophy and from 6 fetuses at high risk (95%) for Duchenne muscular dystrophy (DMD) were probed with specific antibodies for the presence of dystrophin and nebulin. Dystrophin was absent in all 5 patients with DMD and 4 of 6 fetuses at high risk for DMD and present in trace amounts in the remaining two. Dystrophin was also undetectable in one borderline DMD/Becker muscular dystrophy (BMD) case and reduced in 2 of 4 cases of BMD. In contrast, dystrophin was present in all 16 biopsies from 4 other types of muscular dystrophy (congenital, limb girdle, Emery-Dreifuss and facioscapulohumeral). Nebulin profiles varied with the type, severity and duration of the dystrophic process. Nebulin was present in 5 of 6 DMD fetal samples but vastly reduced or absent in all samples of clinically manifest DMD.

An unusual strain of human keratinocytes which do not stratify or undergo terminal differentiation in culture

We have characterized an unusual cell phenotype in third passage cultures of a human keratinocyte strain derived from newborn foreskin epidermis. The cells had the same DNA fingerprint pattern as the second passage, morphologically normal, keratinocytes; they formed desmosomes and expressed the keratin profile characteristic of normal keratinocytes in culture. However, unlike normal keratinocytes, the cells did not grow as compact colonies and did not stratify or undergo terminal differentiation, even after TPA treatment or suspension culture. For these reasons we named them ndk for "nondifferentiating keratinocytes." The ndk cells also differed from normal keratinocytes in that they did not require a feeder layer and were not stimulated by cholera toxin to proliferate. The ndk cells had an absolute requirement for hydrocortisone and their growth rate was increased when epidermal growth factor was added to the medium. Although ndk failed to undergo terminal differentiation in culture, they were not transformed, since they were still sensitive to contact inhibition of growth, did not proliferate in soft agar, and had a limited lifespan in culture. The appearance of the ndk phenotype was correlated with a doubling of chromosome number and the presence of a lp marker chromosome. We suggest that these cells are a useful experimental adjunct to cultures of normal keratinocytes, in which proliferation and terminal differentiation are tightly coordinated, because in ndk cells there appears to be a block in terminal differentiation.

Allergens of the imported fire ant

A whole body extact (WBE) was prepared by saline extraction of ground imported fire ants (IFA). A serum pool from rabbits immunized with the WBE elicited 31 precipitates on crossed immunoelectrophoresis. Crossed radioimmunoelectrophoresis was performed with sera from 26 RAST IFA-positive subjects, 24 of whom were known for clinical hypersensitivity to IFA and two subjects, known to be hypersensitive to yellow jacket. Radiostaining was obtained to 14 precipitates, some of which were judged to be partially identical. Thus, six apparently different allergen groups could be identified. Two of these fulfilled arbitrary criteria of major allergens. Three of the IFA WBE allergens were easily identified in crossed immunoelectrophoresis of a commercially obtained IFA-venom preparation. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis of the IFA WBE demonstrated protein bands with molecular weight ranging from 10,000 to 200,000 daltons. An immunoblotting technique with nitrocellulose paper strips revealed binding of human IgE from hypersensitive subjects to four different bands (either single bands or clusters of proteins of similar molecular weight) with molecular weights ranging from 13,000 to 42,000 daltons. It is a notable finding that these insect allergens thus were of a similar size as important aeroallergens.

In vivo analysis of puf operon expression in Rhodobacter sphaeroides after deletion of a putative intercistronic transcription terminator

The intercistronic region of the mRNA derived from the puf operon of Rhodobacter sphaeroides is capable of forming two stable stem-loop structures, the first of which resembles a factor-independent transcription terminator. A puf operon construction lacking the putative transcription terminator was made in vitro and crossed into the chromosome of R. sphaeroides PUFB1 to yield a single chromosomal copy in the terminator-deleted strain. The mutant strain, designated PUF delta 348-420 which was otherwise isogenic with the wild-type strain 2.4.1, showed a normal growth rate at high light intensity compared with the wild type, with the levels of the B875 and reaction center spectral complexes being approximately 7% and 25%, respectively, of those found in the wild type. The deletion mutation correlated with a reduction in the size of the fixed photosynthetic unit from 15:1 in the wild type to 4:1 in the mutant. The level of the B800-850 complex was increased approximately twofold in the mutant strain. However, substantial amounts of the B875 and reaction center polypeptides were not incorporated into spectrally active complexes, suggesting the importance of other factors in the assembly of these complexes. Removal of the intercistronic stem-loops resulted in increased readthrough of the puf operon terminator to regions downstream, as well as altering the stability of the resulting puf operon-specific transcripts. A model is proposed which links ribosome stalling within the open reading frame K leader region of the puf operon transcript with chain termination.

Specific Epstein-Barr virus serological response in patients with nasopharyngeal carcinoma detected by immunoblotting

The specific humoral immune response against Epstein-Barr virus (EBV) antigens in patients with nasopharyngeal carcinoma (NPC) was compared to that of patients with infectious mononucleosis (IM) and other EBV-seropositive subjects using immunoblotting technique. Almost all sera from EBV serologically associated NPC reacted reproducibly with a major group of polypeptides (four to six) of early antigen (EA) complex with molecular weights ranging from 50 kD to 58 kD, and with some additional polypeptides. Sera from IM-patients reproducibly recognized only one polypeptide of 50 kD belonging to the major group of polypeptides of EA-complex. Sera from patients with other types of head and neck cancer and relatively high levels of IgG antibody against viral capsid antigen (VCA) and EA did not react reproducibly with any of the EBV-associated proteins.

A protein-free blocking system for the covalently binding matrix cyanuric chloride-activated paper in immunological procedures

A new protein-free blocking system containing 10% (w/v) sulfanilic acid/10% (v/v) triethanolamine/0.05% (v/v) Tween 20 has been used to block free binding sites of the covalently binding matrix cyanuric chloride-activated paper (CCA-paper). This method allows a reversible staining of protein blots with Coomassie brilliant blue after each step of the immunological procedure and reuse of the blots for a repeated antibody probing. Non-radioactive and radioactive detection procedures have been compared with blots on CCA-paper and nitrocellulose. The best combination is a Coomassie brilliant blue staining and immunological detection with 125I-protein A.

A novel two-site immunoradiometric assay for beta-endorphin using nitrocellulose as solid phase

A two-site immunoradiometric assay for the highly specific direct quantitation of nonacetylated beta h-EP in crude brain tissue samples has been developed with a detection limit of 10 fmol per well. The assay used two different antibodies with distinct specificities: a polyclonal rabbit anti-beta h-EP antibody binding between the middle portion and the C-terminal end of beta h-EP was bound to nitrocellulose membrane discs, a solid phase with a high protein binding capacity. In the following two incubation steps, the beta h-EP containing crude tissue extract--or the beta h-EP-standard--and, subsequently, the 125I-labeled monoclonal 3-E7 mouse antibody directed against the N-terminus of beta h-EP were added. Binding of beta h-EP to the solid phase antibody in the first incubation step was not affected by the addition of cross reacting opioid peptides derived from beta h-LPH up to 10 pmol per disc. Nonspecific binding of the labeled antibody to the solid phase could be lowered to 3% of total counts by the use of PBS containing nonfat dry milk as blocking solution and incubation buffer, a procedure that did not reduce maximum specific binding. Dilution studies performed with extracts sampled from the anterior hypothalamus excluded the interference of tissue factors in the assay.

Fluorescent labeling of nitrocellulose-bound proteins at the nanogram level without changes in immunoreactivity

Proteins blotted on nitrocellulose were stained with either 5-dimethylamino-1-naphthalene-sulfonylchloride (dansyl chloride) or fluorescein isothiocyanate. In both cases the staining procedure can be completed in less than 30 min. The sensitivity for detecting fluorescent-labeled proteins on nitrocellulose was 0.5 ng using a dot test. This was accomplished by transparentizing the nitrocellulose with either immersion oil or toluene. Dansylated proteins were successfully utilized for optimizing the electroblotting procedure. In the presence of 0.2% sodium dodecyl sulfate and 20% methanol the distribution of proteins on the nitrocellulose was an exact replica of the protein pattern seen in the polyacrylamide gel. The fluorescent labeling did not affect the antigenic properties of proteins allowing the subsequent probing with antisera. For this procedure, only one set of samples is needed to obtain accurate photographic records of the gel, the nitrocellulose blot, and the probed blot.

Identification of an Escherichia coli S1-like protein in the spinach chloroplast ribosome

Antibodies directed against E. coli ribosomal protein S1 were used in immunoblotting assays to search for an S1-like protein in the ribosome of spinach chloroplast. An immunological cross-reaction was reproducibly detected on the blots and inhibition experiments have demonstrated its specificity. The chloroplastic ribosomal protein which has epitopes common to antigenic determinants of the E. coli protein S1 was identified as being protein S2/S3.

Characterization of a major virion envelope glycoprotein complex of murine cytomegalovirus and its immunological cross-reactivity with human cytomegalovirus

Three glycoproteins on the murine cytomegalovirus (MCMV) virion with apparent molecular weights of 150K (gp 150), 105K (gp 105), and 52K (gp52) were immunoprecipitated by two monoclonal antibodies (MAbs) 8G5.12A and 2E.12A. However, only 8G5.12A was able to neutralize MCMV infectivity in the presence of complement. The accessibility of these three glycoproteins to radiolabeling by surface-iodination reactions suggested that they were exposed on the surface of the virion. Western blot analysis of the three glycoproteins showed that gp150 shared antigenic determinants with gp105 and gp52. Briefly, the MAb 8G5.12A reacted with gp150 and gp105, whereas the MAb 2E8.12A reacted with gp150 and gp52. A third MAb 3H2.12A was also found to be reactive with gp150 and gp105 in Western blots, but was unable to immunoprecipitate these glycoproteins. Data from pluse-chase experiments suggested that all three virion glycoproteins were synthesized from a common 128K precursor, providing a partial explanation of their antigenic relatedness. Furthermore, we have demonstrated the presence of high-molecular-weight complexes formed by disulfide bonding between gp150, gp105, and gp52. Lastly, the MAb 8G5.12A was able to immunoprecipitate 84K and 99-110K glycoproteins from human CMV-infected WI-38 cells, demonstrating that conserved determinants exist between murine and human CMV envelope glycoproteins.

Purification of outer membrane proteins of the gram-negative bacterium Neisseria gonorrhoeae

A system of protein purification, using sodium dodecyl sulfate-polyacrylamide gel electrophoresis and electroblotting, that results in purified outer membrane proteins of the gram-negative bacterium Neisseria gonorrhoeae is described. The proteins, which ranged in apparent molecular mass from approximately 31,000 to approximately 92,000 Da, were located by naphthol blue black staining, eluted from nitrocellulose membranes using 88% formic acid, and precipitated by the addition of concentrated ammonium hydroxide. Up to 65% of the original protein present was recovered by this procedure. The resultant purified protein could then be resuspended in aqueous buffer by brief sonication, making it available for further structural and in vivo immunological analyses. Proteins purified in this manner retain their original antigenicity when probed with polyclonal and monoclonal antibodies, and are structurally unaltered by the purification process. This procedure makes it possible to acquire easily usable quantities of highly insoluble outer membrane proteins of gram-negative bacteria.

Antibodies to synthetic peptides from the tubulin regulatory domain interact with tubulin and microtubules

The carboxyl-terminal region of tubulin alpha and beta subunits plays a major role in regulating its assembly into microtubules and constitutes an essential domain for the selective interaction of microtubule-associated proteins (MAPs). With the goal of understanding the structural basis of the regulatory function of the carboxyl-terminal domains of tubulin subunits, we have produced rabbit antisera against two MAP-interacting peptides Lys-Asp-Tyr-Glu-Glu-Val-Gly-Val-Asp-Ser-Val-Glu of alpha-tubulin and Tyr-Gln-Gln-Tyr-Gln-Asp-Ala-Thr-Ala-Asp-Glu-Gln-Gly of beta subunit. The affinity-purified alpha and beta anti-peptide antibodies interacted specifically with tubulin and with the respective peptide antigens but did not interact with MAPs. Substoichiometric amounts of both antibodies showed the capacity to inhibit in vitro MAP-induced tubulin assembly and to promote a fast depolymerization of preassembled microtubules. Taxol-promoted assembly of pure tubulin was not inhibited by the antibodies. In the presence of MAP-2 and taxol, the antibodies decreased the MAP-2 content of taxol-promoted microtubules. The interaction with microtubules was corroborated by immunofluorescence experiments in HeLa and NE-18 lung carcinoma cells. The epitopes recognized by the alpha and beta anti-peptide antibodies appear to be located in the outer surface of the microtubular structure.

India ink staining of proteins on nylon and hydrophobic membranes

India ink was found to be an acceptable stain for proteins blotted or dotted onto positively charged nylon or hydrophobic membranes. The hydrophobic membrane, Immobilon, was an outstanding matrix for binding proteins and displayed low levels of background staining. The least amount of protein detected by india ink staining was between 1.0 and 10 ng. India ink staining of proteins on nylon membranes is an easy, inexpensive, and quick method for the unequivocal detection of both standards and unknowns in the same blot. However, inks, ink concentrations, fixing conditions, staining times, pH, washing conditions, and membrane lots all need to be controlled to achieve maximum sensitivity for protein detection following india ink staining.

The use of polyvinylidenedifluoride membranes as a general blotting matrix

A fast chemical staining of protein by Coomassie blue on a stable nonshrinking membrane of polyvinylidenedifluoride is described. The procedure is especially useful for detection of nonlabeled marker proteins in comparison to specifically detected proteins. The membrane is highly suitable for other chemical stains like silver, gold, or india ink for immunostaining, lectin binding, and binding of radioactive ligands like 45Ca. Blocking of the background against nonspecific binding to proteins was studied using different reagents. A multiple slit plate is described for volume-saving simultaneous application of multiple reactants on one protein-loaded membrane.

Anti-idiotypic antibodies that react with microtubule-associated proteins are present in the sera of rabbits immunized with synthetic peptides from tubulin's regulatory domain

A fundamental question in microtubule research is how the interactions of tubulin subunits with microtubule-associated proteins (MAPs) are controlled. The answer should provide insight into the regulation of the cellular processes in which microtubules are implicated. Previous work demonstrated the interaction of MAPs with a 4-kDa C-terminal domain of tubulin alpha and beta subunits. Synthetic peptides from the variable region of the 4-kDa C-terminal moiety of tubulin subunits, alpha-(430-441) and beta-(422-434), bind to MAP-2 and to the MAP tau, and a preferential interaction of the beta peptide is observed. To define the regulatory significance of the substructure of the C-terminal tubulin domain, we produced rabbit antisera against these MAP-interacting peptides. We found that these antisera contained not only antibodies to the original synthetic peptides but also antibodies to MAPs. Here, we report that these antibodies, which react with MAP-1, MAP-2, and tau, appear to be a population of anti-idiotypic antibodies directed to the anti-peptide antibodies. They can inhibit MAP-induced tubulin assembly into microtubules in vitro, and the addition of MAPs overcomes the inhibition. The recognition by these anti-idiotypic antibodies of the tubulin-binding domain on MAPs provides unequivocal evidence that the tubulin region defined by the synthetic peptides is directly involved in the interaction with MAPs.

Analyses of frequency of infection, specific infectivity, and prion protein biosynthesis in scrapie-infected neuroblastoma cell clones

Scrapie, a spongiform encephalopathy of sheep and goats, is caused by a poorly understood transmissible agent in which no nucleic acid has been conclusively identified. Biochemical characterization of agent derived from animal tissues has not been precise because of the tenacious association of the agent with tissue components. As an approach toward obtaining homogeneous preparations of agent generated in vitro, we cloned scrapie-infected neuroblastoma cells. By frequency analysis, nearly every cell in expanded cultures contained scrapie agent. We also analyzed cell-dose infectivity relationships and developed a standard curve which allowed various cultures to be compared. Since a proteinase K (PK)-resistant form of a protein designated prion protein (PrP) has been found in partially purified preparations of scrapie agent from infected animal spleens and brains, we sought to identify this protein in cell cultures. No PK-resistant PrP was found in infected or uninfected cultures, although the PK-sensitive PrP was readily detected. These results suggested that PK-resistant PrP may not be an essential component of the infectious scrapie agent.

Calmodulin-binding profiles for nebulin and dystrophin in human skeletal muscle

Nebulin and dystrophin are two high-molecular-mass skeletal muscle proteins that have both been associated with the defective gene in Duchenne muscular dystrophy, although the function of neither protein is known. Other high-molecular-mass, calmodulin-binding proteins have recently been implicated in regulating calcium release from skeletal muscle. Western blots of human skeletal muscle biopsy samples were probed with biotinylated calmodulin; nebulin was identified as a prominent high-molecular-mass calmodulin-binding protein but dystrophin did not bind detectable amounts of biotinylated calmodulin. Dystrophin was absent in a Duchenne muscle biopsy.

Monoclonal antibodies to the major structural proteins of bacteriophage phi 6

A panel of 38 monoclonal antibodies to the five major structural proteins of phi 6 was generated and characterized. The panel includes antibodies recognizing the receptor recognition protein P3, the major hydrophobic envelope protein P9, the nucleocapsid surface protein P8, and the nucleocapsid proteins P1 and P4, which are involved in the viral RNA polymerase activity and form the internal protein skeleton of the nucleocapsid. Six out of the fourteen antibodies to the receptor recognition protein, P3, showed neutralizing activity, interfering with the adsorption of phi 6 to host cells.

Diagnostic Mr31/32,000 Schistosoma mansoni proteins (Sm31/32): reaction with sera from Sudanese patients infected with S. mansoni or S. haematobium

Sera of Sudanese patients with active infections of Schistosoma mansoni or S. haematobium were tested in immunoblots for their reactivity with Mr31/32,000 proteins of adult S. mansoni (Sm31/32). All sera from patients with intestinal (n = 123) and all but one from those with urinary schistosomiasis (n = 35) had antibodies against Sm31/32. These and additional data suggest that both specificity and sensitivity of Sm31/32 to detect schistosome infections are close to 100%. Antibodies against these proteins developed also in monkeys after experimental infection with S. haematobium. Sm31/32 antigens reacted in immunoblots as a doublet with most S. haematobium-patient sera and as a broad band with many S. mansoni-sera suggesting that at least two components are present in the molecular weight region of Mr31/32,000. The data demonstrate the potential use of Sm31/32 from adult worms to diagnose patients with intestinal or urinary schistosomiasis in endemic areas.

Characterization of the binding epitope of a monoclonal antibody to sulphatide

An IgG1 monoclonal antibody, Sulph I, reacting with sulphatide (3'-sulphogalactosylceramide), was produced by immunizing Balb/c mice with that glycolipid coated on Salmonella minnesota bacterial membrane. Radioimmunodetection of the binding of the monoclonal antibody to structurally related glycolipids adsorbed to microtitre plates or chromatographed on thin-layer plates was used to determine its binding epitope. The antibody showed similar binding avidity to three sulphated glycolipids: sulphatide, sulpholactosylceramide and seminolipid. Lysosulphatide did bind the antibody, but, compared with sulphatide, 30 times more antigen was needed for half-maximal binding. Bis(sulphogangliotriosyl)ceramide and bis-sulphogangliotetraosylceramide did not bind the antibody. These results suggest that terminal galactose-3-O-sulphate and part of the hydrophobic region of the glycolipid are recognized by the Sulph I antibody.

Protein blotting: techniques and application in virus hepatitis research

The protein-blotting technique is a very practical way to detect and characterize certain proteins in a complex sample by various reagents like polyclonal and monoclonal antibodies, lectins, nucleic acids, or other ligands. This article discusses several options to perform this technique with special reference to viral hepatitis. We give a detailed description of denaturing gel electrophoresis, blotting and specific detection methods. At the beginning of each section a general outline of a certain technique is given, thereafter the reagents, equipment, suppliers, and techniques are described in a way that a beginner may be able to perform the assay.

Investigation of human immune response to Micropolyspora faeni antigens by enzyme-linked immunoelectrodiffusion assay and immunoblotting

Immune response to Micropolyspora faeni was analyzed in 10 patients suffering from farmer's lung by two techniques: enzyme-linked immunoelectrodiffusion assay (ELIEDA) and immunoblotting. ELIEDA revealed the presence in all patients of various specific immunoglobulin G (IgG), IgM, IgA, and IgE antibodies, with the number of arcs ranging from 4 to 19. M. faeni proteins were isolated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, transferred to nitrocellulose, and immunoblotted with human sera and specific immunoglobulin-peroxidase conjugates. In immunoblotting, the predominant immunoglobulin class was IgG for all patients. At least 20 bands ranging from 15,000 to 60,000 in molecular weight were observed in a highly positive serum, whereas IgM- and IgA-specific reactivity was directed mainly to the 28,000- and 49,000-molecular-weight bands; M. faeni-specific IgE antibodies appeared less often. The rheumatoid factor (IgM-RF), which also had high titers in these patients (greater than 1/512), interfered with ELIEDA, while only slightly interfering with the immunoblotting detection of specific IgM. This latter technique provided a better characterization of immune response in patients with farmer's lung than ELIEDA did and should also permit discrimination of recently exposed individuals from chronic patients. Moreover, this technique should make it possible to determine whether the response of one particular immunoglobulin class to an antigen fraction can be associated with a specific state of the disease.

Cholinergic regulation of protein phosphorylation in bovine adrenal chromaffin cells

Chromaffin cells were isolated from bovine adrenal medullae and maintained in primary culture. After prelabeling with 32PO4, exposure of the chromaffin cells to acetylcholine increased the phosphorylation of a Mr approximately equal to 100,000 protein and a Mr approximately equal to 60,000 protein (tyrosine hydroxylase), visualized after separation of total cellular proteins in naDodSO4/polyacrylamide gels. Immunoprecipitation with antibodies to three known phosphoproteins ("100-kDa," "87-kDa," and protein III) revealed an acetylcholine-dependent phosphorylation of these proteins. These three proteins were also shown to be present in bovine adrenal chromaffin cells by immunolabeling techniques. "100-kDa" is a Mr approximately equal to 100,000 protein selectively phosphorylated by calcium/calmodulin-dependent protein kinase III, "87-kDa" is a Mr approximately equal to 87,000 protein selectively phosphorylated by protein kinase C, and protein III is a phosphoprotein doublet of Mr approximately equal to 74,000 (IIIa) and Mr approximately equal to 55,000 (IIIb) phosphorylated by cAMP-dependent protein kinase and calcium/calmodulin-dependent protein kinase I. Furthermore, 100-kDa was shown to be identical to the Mr approximately equal to 100,000 protein whose phosphorylation was increased by acetylcholine treatment. The acetylcholine-dependent increase in phosphorylation of tyrosine hydroxylase, 100-kDa, 87-kDa, and protein III required extracellular calcium and was mimicked by nicotine, veratridine, elevated K+, and calcium ionophore A23187, but not by muscarine. In addition, forskolin increased the phosphorylation of tyrosine hydroxylase, 100-kDa, and protein III, but not that of 87-kDa. Phorbol 12,13-dibutyrate increased the phosphorylation of tyrosine hydroxylase, 87-kDa, and protein III, but not that of 100-kDa. The data demonstrate that cholinergic activation of chromaffin cells increases the phosphorylation of several proteins and that several protein kinase systems may be involved in these effects.

Ig class and IgG subclass responses to Treponema pallidum in patients with syphilis

The Ig class and IgG subclasses of anti-Treponema pallidum antibodies in human serum were quantified using solid-phase enzyme-linked immunosorbent assays. Development of these assays with monoclonal antibodies, each specific for a human immunoglobulin class or IgG subclass, provided quantitative data concerning the major antibody specificities. In patients with primary syphilis, anti-T. pallidum activity was limited almost exclusively to IgG1 and IgM. Coordinate, restricted expression of IgG1 and IgG3 responses in T. pallidum-specific assays was observed with sera from patients with active secondary syphilis. IgG1 and IgG3 accounted for roughly 53 and 43% of the total anti-treponemal IgG antibody activity, respectively. While IgM antibody levels were elevated in the patients with secondary syphilis, IgG2 and IgG4 levels, if present at all, represented less than 10 and 2% of the total IgG activity, respectively. Ig in sera from patients who had been treated adequately for secondary syphilis were restricted almost entirely to IgG3 and IgG1. Considering the low level of IgG3 in serum, disproportionately high percentages of antitreponemal antibodies were found in this subclass during and after treatment for secondary syphilis. The restricted, coexpression of the IgG1 and IgG3 isotypes may reflect the close genetic linkage of the gamma 1 and gamma 3 genes and possibly the impact of immunoregulatory mechanisms in response to the induction and expression of autoantibodies which arise during the course of secondary syphilis.

The use of Tween 20 alone as a blocking agent for immunoblotting can cause artefactual results

The use of Tween 20 as a suitable blocking agent in immunoblotting studies was evaluated by screening a panel of monoclonal antibodies (MoAbs) against a selection of blotted proteins which were unrelated to the antigens used to raise the MoAbs. Using Tween 20 alone to block the nitrocellulose membranes clear reactions were observed between the panel of MoAbs and several components of the blotted protein mixture. In contrast, when haemoglobin was used to block the membranes such reactions were not observed. In the absence of added protein the use of Tween 20 alone as a blocking agent for immunoblotting appears to lead to false positive reactions by non-specific antigen-antibody complexes.

Molecular comparisons of in vivo- and in vitro-derived strains of Aleutian disease of mink parvovirus

DNA from one cell culture-adapted and two pathogenic strains of Aleutian disease of mink parvovirus (ADV) was molecularly cloned into the vectors pUC18 and pUC19. The DNA from the two pathogenic strains (ADV-Utah I and ADV-Pullman) was obtained from virus purified directly from the organs of infected mink, whereas the DNA from the nonpathogenic ADV-G was derived from cell culture material. The cloned segment from all three viruses represented a 3.55-kilobase-pair BamHI (15 map units) to HindIII (88 map units) fragment. Detailed physical mapping studies indicated that all three viruses shared 29 of 46 restriction endonuclease recognition sites but that 6 sites unique to the pathogenic strains and 5 sites unique to ADV-G were clustered in the portion of the genome expected to code for structural proteins. Clones from all three viruses directed the synthesis of two ADV-specific polypeptides with molecular weights of approximately 57 and 34 kilodaltons. Both species reacted with sera from infected mink as well as with a monoclonal antibody specific for ADV structural proteins. Because production of these ADV antigens was detected in both pUC18 and pUC19 and was not influenced by isopropyl-beta-D-thiogalactopyranoside (IPTG) induction, their expression was not regulated by the lac promoter of the pUC vector, but presumably by promoterlike sequences found within the ADV DNA. The proteins specified by the clones of ADV-G were 2 to 3 kilodaltons smaller than those of the two pathogenic strains, although the DNA segments were identical in size. This difference in protein molecular weights may correlate with pathogenicity, because capsid proteins of pathogenic and nonpathogenic strains of ADV exhibit a similar difference.

Cortical cytoskeleton of giant moth eggs

Unfertilized eggs of several species of giant moths contain a substantial cortical cytoskeleton. This structure is assembled during oogenesis, and contains actin as a major fibrillar component. The presence of actin was confirmed by gel electrophoresis and binding to phalloidin, DNase I, and a monoclonal antibody against cytoskeletal actin. Several lines of evidence suggest that the fat body is a source of the actin in the oocyte and that the transport and acquisition of actin by the ovary are similar to the mechanism of vitellogenin acquisition. A possible role for the cortical cytoskeleton in directing early embryogenesis is discussed.

Characterization of monoclonal antibodies to fimbria-associated adhesins of Bacteroides loescheii PK1295

Bacteroides loescheii PK1295 fimbriae, which mediate the lactose-sensitive coaggregation with Streptococcus sanguis 34 and the lactose-insensitive coaggregation with Actinomyces israelii PK14, were injected into mice to raise adhesin-specific monoclonal antibodies (MAbs). Supernatants of hybridomas were screened for the capacity to inhibit coaggregation and agglutinate intact bacteria. Of the 10 MAbs that were isolated, 4 were specific and potent inhibitors of the coaggregation between B. loescheii and S. sanguis and two other MAbs specifically inhibited the B. loescheii-A. israelii interaction. None of the six MAbs which inhibited adherence were capable of agglutinating whole cells of B. loescheii, whereas the four remaining MAbs agglutinated whole cells but had no effect on coaggregation. Fab fragments of two MAbs, one that inhibited the coaggregation with S. sanguis and another that inhibited the interaction with A. israelii, also were shown to inhibit the respective coaggregation interactions, suggesting that each of the immunoglobulins recognized its adhesin molecule at or near the active sites. By immunoblotting or immunoprecipitation, the S. sanguis adhesin-specific MAbs reacted with a 75-kilodalton polypeptide present in fimbria-enriched preparations, whereas the A. israelii adhesin-specific MAbs recognized a 45-kilodalton polypeptide in the same preparations. By screening hybridoma supernatants directly for their capacity to block coaggregation, we isolated MAbs which were used to establish that the B. loescheii-S. sanguis and the B. loescheii-A. israelii interactions were mediated by different adhesins.

The amylase gene-enzyme system of fishes. I. Developmental expression of amylase in the mosquitofish

The objective of this study is to examine the effects of developmental stage on amylase expression in the mosquitofish (Gambusia affinis holbrooki, Poeciliidae). Expression was characterized in terms of amylase activity and amount of amylase protein in five developmental stages: early, mid, and late embryos, 5-day-old juveniles, and adults. Two measures of activity were used: a starch-iodine assay, which measures the change in substrate, and the dinitrosalicyclic acid (DNSA) assay, which measures the change in product. To measure changes in the amount of amylase, the enzyme-linked immunosorbent assay (ELISA) was used. Highest activity and amount was observed in the adult stage. In general, both increased with development. While the two activity measures were positively correlated, these were only weakly correlated with the amount of amylase. Possible reasons for these weak correlations between amylase activity and amount are discussed.

Identification and intracellular localization of the unc-22 gene product of Caenorhabditis elegans

The unc-22 gene is one of a set of genes identified using classical genetics that affect muscle structure and function in the free-living nematode Caenorhabditis elegans. Since cloning the unc-22 gene by transposon tagging, we have used conventional techniques combined with a set of Tc1 transposon insertion alleles to characterize the gene and its products. The gene extends over more than 20 kb of genomic sequence and produces a transcript of approximately 14 kb. A polyclonal antibody raised against an Escherichia coli beta-galactosidase-unc-22 fusion protein recognizes a polypeptide in nematode extracts that is between 500,000 and 600,000 daltons and labels the muscle A-band in indirect immunofluorescent microscopy. The Tc1-induced alleles have been used at every stage to verify these conclusions. The Tc1 insertions are spread over much of the region that contributes to the mature transcript; in most alleles, Tc1 sequences are incorporated into a composite unc-22-Tc1 transcript. The large protein is either absent or severely reduced in amounts in the mutants. In one case, a truncated polypeptide was also identified. The location of the protein in the A-band, along with earlier genetic data, suggests that the unc-22 product may interact with myosin to regulate its function.

The 3' portion of the gene for a Plasmodium yoelii merozoite surface antigen encodes the epitope recognized by a protective monoclonal antibody

The 230-kDa merozoite antigen of the murine malarial parasite Plasmodium yoelii provides a potential model system for the development of a protective erythrocytic stage vaccine. To characterize this antigen at the molecular level, isolated P. yoelii 17XL DNA was used to construct a genomic library in the expression vector lambda gt11. A monoclonal antibody, mAb 302, which passively protected mice against P. yoelii challenge infection, was used to identify a lambda gt11 recombinant clone encoding a portion of the 230-kDa antigen of this parasite. Using this clone as a probe, we identified an mRNA of 7.6 kilobases by RNA blot analysis. Nucleic acid sequence analysis of the clone showed that the epitope recognized by the protective mAb 302 is encoded by the 3' portion of the gene for the 230-kDa antigen. The deduced amino acid sequence revealed that this antigen also contains the tandemly repeated tetrapeptide Gly-Ala-Val-Pro, a series of 10 cysteine residues located within the terminal 110 amino acids, and a potential membrane anchor of 18 hydrophobic residues. Comparison of this C-terminal sequence with the carboxyl segment of the 195-kDa merozoite antigen of Plasmodium falciparum revealed nucleic acid and amino acid sequence similarities ranging from 40% to 70%. The localization of a B-cell epitope recognized by the protective mAb 302 to this carboxyl region of the P. yoelii antigen, combined with the limited strain variability in this region of the homologous 195-kDa antigen of P. falciparum, has implications for the development of an effective erythrocytic stage malarial vaccine.

Specific deposition of serum amyloid A protein 2 in the mouse

The homogenates of amyloid-laden spleens prepared from CBA mice were analysed by SDS-PAGE and immunoblotting employing rat anti-murine monoclonal antibody, MSA 4-26. The results showed that the precursor of amyloid A protein (AA), serum amyloid A protein 2 (SAA2), and SAA intermediates with molecular weights of 10,000, 9000, and 8000 were contained in amyloid-laden tissues. The experiment using sonicated spleen cells and acute phase murine sera showed a delay in the degradation rate of SAA2 on cell fragments and the remains of SAA1 in supernatants. This result can explain disappearance of SAA2 from the murine serum during amyloidogenesis in vivo.

Immunological characterization of an early cytomegalovirus single-strand DNA-binding protein with similarities to the HSV major DNA-binding protein

Monospecific polyclonal antisera were prepared against the 129-kDa, early, single-strand DNA-binding protein (DB129) of strain Colburn cytomegalovirus (CMV), and used to study its distribution in infected cells and its relatedness to a proposed human CMV (HCMV) counterpart (DB140). Indirect immunofluorescence of fixed, infected human fibroblasts showed DB129 to be localized within the intranuclear inclusions characteristic of replicating CMV. Treatment of infected cells with 50 to 100 micrograms phosphonoformic acid per milliliter resulted in the overproduction of DB129 and its accumulation within nuclei, both inside the inclusions and in surrounding areas of the nucleoplasm, whereas treatment with 500 micrograms/ml prevented inclusion formation, and DB129 was localized at discrete points throughout the infected-cell nuclei. The sera cross-reacted an estimated 10% with HCMV DB140 in an indirect immunoassay, and their use in immunofluorescence localized DB140 to the nuclear inclusions of HCMV-infected cells. Their immunological cross-reactivity, as well as their similar biochemical properties and intracellular distribution, support the likelihood that DB129 and DB140 are the protein products of homologous genes. The relationship of these proteins to the herpes simplex major DNA-binding protein is discussed.

Immunological detection of high molecular weight proteins by gel and blot overlay

The sensitivity and specificity of the gel overlay and western blot methods of immunodetection are compared for spectrins, typical high molecular weight proteins. The gel overlay method is more sensitive and specific for the immunodetection of brain spectrin (240/235) and rbc spectrin. As the western blot technique will remain the method of choice for many applications because of its relative speed, we discuss methods for optimizing its sensitivity and selectivity.