An enzyme-linked immunosorbent assay for phytochrome

A double-antibody sandwich, enzyme-linked immunosorbent assay has been developed for phytochrome in Avena sativa L. cv. Saladin. An immunoglobulin fraction of rabbit antiserum raised to 118 kdalton phytochrome was used with alkaline phosphatase as the enzyme label. The assay detected as little as 0.2 ng phytochrome in extracts of dark-grown plant material. No evidence for specific or non-specific measurement of proteins other than phytochrome was found. The assay detected phytochrome in extracts of Avena grown in the light. Dilution curves for light-grown phytochrome extracts had a reduced slope and saturated at a lower level of enzyme activity than those for dark extracts. These differences were not caused by an inhibitor in extracts from light-grown plants. Phytochromes from dark- and light-grown plants may be immunologically different.     

An enzyme-linked immunosorbent assay for N-acetylglucosaminyltransferase-V

The development of an enzyme-linked immunosorbent assay (ELISA) for uridine 5'-diphospho-N-acetyl-glucosamine: alpha mannoside beta 1----6 N-acetylglucosaminyltransferase (GnT-V) is reported. The assay quantitates the enzymatic conversion of the specific synthetic GnT-V acceptor GlcNAc beta 1----2Man alpha 1----6Man beta-R (5) to the product GlcNAc beta 1----2[GlcNAc-beta 1----6]Man alpha 1----6Man beta-R (6) when these oligosaccharide structures were covalently attached to bovine serum albumin which was then coated on microtiter wells. Conversion of 5 to 6 was detected using a polyclonal antiserum raised against the product 6 and from which antibodies cross-reacting with acceptor 5 had been removed by affinity adsorption. GnT-V activity detected by ELISA was linearly proportional to both enzyme concentration and time under appropriate experimental conditions where 50-300 fmol of product was formed per microtiter well. GnT-V activity could be measured by ELISA in Triton X-100 extracts of hamster kidney acetone powder and in human serum. The twofold increase in GnT-V activity which is known to accompany Rous sarcoma virus transformation of baby hamster kidney cells could also be quantitated using the ELISA.     

An assay of collagenase activity using enzyme-linked immunosorbent assay for mammalian collagenase

A new method was developed for the measurement of collagenase activity using the enzyme-linked immunosorbent assay (ELISA). Rabbit colon wall collagenase, pepsin-soluble rat skin type I collagen, and its antisera were used in the present experiment. After the collagenase-degraded portion of the collagen coated on the microwell was released, the immunoreaction of the residual collagen on the microwell to anticollagen sera was determined by ELISA. This method was approximately 10 times more sensitive than the conventional assay procedure using [14C]-glycine-labeled reconstituted collagen fibrils as substrate. It was suitable for screening a large number of samples without radioisotopes.     

An enzyme-linked immunosorbent assay for rat prolactin

A sensitive and specific competitive enzyme-linked immunosorbent assay (ELISA) for rat prolactin was developed using reagents from the National Institute of Arthritis, Diabetes, Digestive Diseases and Kidney. In this assay soluble prolactin and prolactin adsorbed to a solid-phase support compete for rabbit anti-prolactin antibody binding sites. Therefore, a high concentration of soluble prolactin in the sample will result in a low concentration of antibody immobilized to the adsorbed prolactin. The immobilized antibody-prolactin complex is detected and quantified using goat anti-rabbit immunoglobulin G covalently conjugated to the enzyme horseradish peroxidase. Assay parameters were optimized by investigating the concentration of reagents and the reaction kinetics in each of the assay steps. The assay can be performed in 24 h. A sensitivity range of 0.06 to 6 ng in the region of 90 to 10% binding was obtained. Near 50% binding (0.6 ng), the intraassay coefficient of variation (CV) was 4.2% and the interassay CV was 7.6%. The correlation between radioimmunoassay and the ELISA was 0.868. Selected applications of the assay are described. The assay should prove a useful alternative to the radioimmunoassay in those instances where steps involving the use of 125I become limiting, for example, iodination facility and gamma counter availability or prolonged reagent storage.     

An enzyme-linked immunosorbent assay for plant cadmium-binding peptide

Polyclonal antibodies raised against Cd-binding peptide from roots of Agrostis gigantea Roth were used with an enzyme-linked immunosorbent assay (ELISA). The antigen was best adsorbed to Immulon 2 “U” microtitre plates in 50 mM acetic acid. The antibodies to the antigen from Agrostis cross-reacted with Cd-binding peptides from the roots of maize and tomato, but not with glutathione nor metallothioneins I and II from rabbit liver. The antibodies reacted specifically with peptides rich in cysteine and glutamate, and having glycine or serine in the least amount. Reaction of antibodies was limited to ELISA; the antiserum did not form antigen-antibody precipitates when tested by standard diffusion and immunoelectrophoretic methods.     

An enzyme-linked immunosorbent assay for 6-keto PGF

An enzyme-linked immunosorbent assay for 6-keto prostaglandin F_1α, a stable metabolite of prostacyclin, has been developed. The assay allows quantitation of 6-keto PGF_1α in the range 1–200 pg/0.1 ml and shows very low cross reactivity to nine other prostaglandins. Dose dependent stimulation by thrombin of 6-keto PGF_1α formation in human endothelial cells in culture has been used to verify the assay. Quantitation by the enzyme linked immunosorbent assay agrees closely with determination by radioimmunoassay.     

Measurement of cell proliferation by enzyme-linked immunosorbent assay (ELISA) using a monoclonal antibody to bromodeoxyuridine

An ELISA was developed and optimized to measure cell proliferation using a monoclonal antibody to bromodeoxyuridine (BrdUrd). Incorporation of BrdUrd into myoblast monolayers, measured as the optical density at 492 nm, increased in response to fetal calf serum, IGF-I and EGF, the ELISA data correlated closely with data obtained by BrdUrd immunocytochemistry (r = 0.984), cell counting (r = 0.972) and tritiated thymidine uptake by liquid scintillation counting (r = 0.990). The BrdUrd ELISA is a useful alternative to measurement of tritiated thymidine uptake by scintillation counting, and has the added advantages of dispensing with the use of radioactivity and of being less labour intensive.     

An enzyme-linked immunosorbent assay (ELISA) for plasma testosterone

A rapid, single extraction ELISA for testosterone in plasma is described, using a standard 96 well microtitre plate. Testosterone is covalently bonded to bovine thyroglobulin and passively adsorbed in guanidine hydrochloride to the ELISA plate, giving an immobilised antigen approach which simplifies subsequent assay standardisation for steroid hormone assays. The addition of standard, sample and first antibody (rabbit anti-testosterone), which is unique for each different assay, is followed by a general procedure which includes washing, addition of peroxidase labelled goat antirabbit IgG, further washing and finally, addition of o-phenylenediamine substrate with colour development and reading of the plate at 492 nm on an automatic ELISA processor. The ELISA assay is compared to a testosterone RIA with 125I-label and has similar specificity and precision to the latter with a quicker processing time, and is more cost effective. The added advantages that ELISA assays confer over RIAs in terms of isotope purchase and disposal make this an ideal procedure for use in a routine steroid laboratory.     

An enzyme-linked immunosorbent assay (ELISA) for plasma cortisol

A direct ELISA for plasma cortisol is described which is carried out in a standard 96 well microtitre plate. In this ELISA cortisol-thyroglobulin conjugate is immobilised to the microtitre plate and competes with cortisol in the standard or plasma sample for antibody binding sites. Following washing the rabbit cortisol antibody bound to immobilised cortisol is incubated with peroxidase labelled goat antirabbit IgG. Following further washing o-phenylenediamine is added, colour developed, and the plate read at 492 nm on a standard ELISA plate reader. This ELISA shows good agreement with RIA and its sensitivity, specificity and precision allow its use in the routine steroid laboratory.     

Clickable enzyme-linked immunosorbent assay

Click chemistry is explored as a potential cost-effective and selective immobilization method for the production of an enzyme-linked immunosorbent assay (ELISA). Coatings were formulated containing either a terminal alkyne or a bicyclo[6.1.0]non-4-yne (BCN) chemical handle, and a diagnostic peptide was subsequently immobilized onto these coatings by the copper-catalyzed azide-alkyne 1,3-dipolar cycloaddition (CuAAC) or copper-free strain-promoted azide-alkyne 1,3-dipolar cycloaddition (SPAAC), respectively. The terminal alkyne-containing coating showed high background levels in subsequent ELISA's due to the copper catalyst used in the immobilization step. The BCN-containing coating, however, was successfully employed and presents a cost-effective alternative to existing (strept)avidin-biotin immobilization methods. This technology was illustrated with an ELISA used for the diagnosis of rheumatoid arthritis (RA) but could be easily applied to a wide range of diagnostic tests.     

An enzyme-linked immunosorbent assay for quassin and closely related metabolites

A microtitration plate enzyme-linked immunosorbent assay has been developed for quassin and closely related seco-triterpenes. The method is much more sensitive than conventional chromatographic techniques and enables the routine analysis of large numbers of samples with a detection limit of 5 ng quassin. Antibody production was elicited by injecting a conjugate of iso-quassinic acid linked to bovine serum albumin into rabbits. Important features of the technique are (a) the use of a double-antibody, noncompetitive enzyme-linked immunosorbent assay for a low-molecular-weight, nonantigenic compound using microtitration plates; and (b) that the initial incubation of samples with primary antiserum can be carried out in buffer containing up to 20% ($\text{v}\text{v}$) methanol with minimal loss of sensitivity. The structural requirements for recognition of the hapten by the antiserum are considered based on the levels of cross-reaction found with a wide range of other quassinoids.     

An enzyme-linked immunosorbent assay for zein and other proteins using unconventional solvents for antigen adsorption

An enzyme-linked immunosorbent assay (ELISA) performed in polystyrene microtiter plates that can detect and quantitate the maize prolamin zein is described. The assay yields positive reactions with as little as 1 ng of antigen and uses solvents not ordinarily employed in ELISA methods. A systematic investigation of zein adsorption to polystyrene in various solvents supports the hypothesis that antigen binding occurs through nonpolar interactions. The method was also used to determine structural relationships among three zein polypeptides differing in size and charge. Additional experiments indicate that a number of soluble proteins are absorbed to polystyrene in the denaturing agent urea and retain immunological reactivity. The retention of antigen reactivity after solubilization in 6-8 M urea suggests that ELISA methods may be applicable to other proteins which are insoluble, or rendered insoluble, in aqueous buffers.     

An enzyme-linked immunosorbent assay for 6-keto PGF1 alpha

An enzyme-linked immunosorbent assay for 6-keto prostaglandin F1 alpha, a stable metabolite of prostacyclin, has been developed. The assay allows quantitation of 6-keto PGF1 alpha in the range 1-200 pg/0.1 ml and shows very low cross reactivity to nine other prostaglandins. Dose dependent stimulation by thrombin of 6-keto PGF1 alpha formation in human endothelial cells in culture has been used to verify the assay. Quantitation by the enzyme linked immunosorbent assay agrees closely with determination by radioimmunoassay.     

A simple competitive enzyme-linked immunosorbent assay using antigen-beta-galactosidase fusions

The fusion of the N-terminal 461 bp of the human interferon-alpha 2 (INF) in frame to the beta-galactosidase gene from Escherichia coli is described. The presence of the expected DNA sequence was shown by restriction mapping and DNA sequencing. A fusion protein was demonstrated in crude extracts of E. coli by Western blots using polyclonal anti-beta-galactosidase and monoclonal anti-IFN antibodies. Using monoclonal antibodies specific for the N-terminal region of IFN-alpha and cell-free extracts from an E. coli strain containing the fusion protein, we set up a simple competitive enzyme-linked immunosorbent assay for human interferon. The test described here was linear down to a lower detection limit of at least 1000 Units, or 5 ng human IFN.     

An enzyme-linked immunosorbent assay for the detection of cytoplasmic polyhedrosis virus

An enzyme-linked immunosorbent assay (ELISA) for the detection of Euxoa scandens cytoplasmic polyhedrosis virus (EsCPV) is described. Antisera to EsCPV, produced in rabbits and guinea pigs, are specific to EsCPVs when used in an indirect assay. This indirect assay approach permits the detection of homologous antigens at a concentration of about 1 μg/ml; however, this procedure is not suitable to test large numbers of unpurified specimens. For this type of analysis we used a double antibody sandwich assay which can detect 10 ng/ml of homologous antigen in unpurified material without nonspecific reactions. This assay is used to diagnose EsCPV infections in field and laboratory studies.     

An optimized enzyme-linked immunosorbent assay for quantitative diagnosis of bovine fascioliasis

An optimized immunoassay for detection of antibody to Fasciola hepatica antigen in cattle was developed through the adaptation of a kinetics-dependent, enzyme-linked immunosorbent assay (k-ELISA) to a microplate format. Enhanced sensitivity and a strict quantitative nature were achieved with the utilization of enzyme kinetics. With this k-ELISA, significant (P less than 0.01) elevations in anti-F. hepatica antibody could be detected as early as 2 wk post-infection in experimentally infected calves. Furthermore, fluke-burden related differences in anti-F. hepatica antibody levels between 3 different levels of fluke infection were evident.     

An enzyme-linked immunosorbent assay (ELISA) for human corticosteroid-binding globulin

A specific and sensitive enzyme-linked immunosorbent assay (ELISA) of the "sandwich-type" for human corticosteroid-binding globulin was developed. A polyclonal rabbit anti-CBG antibody is immobilised to a microtitre plate. Following incubation of standards and samples a second monospecific rabbit anti-CBG antibody, labelled with alkaline phosphatase, is added. After colour development the microtitre plate is read at 405 nm wavelength. The assay shows good agreement to CBG binding capacity assay and commercially available RIA.     

Microwave-mediated enzyme-linked immunosorbent assay procedure

Here we demonstrate a novel microwave-mediated enzyme-linked immunosorbent assay (MELISA) method that has dramatically reduced the enzyme-linked immunosorbent assay (ELISA) timing to less than 5 min with a result comparable to that obtained by 18-h conventional ELISA. Efficacy of the MELISA procedure is demonstrated by detecting human immunoglobulin G (IgG), rabbit IgG, human immunoglobulin E (IgE), human interleuken 1β (IL-1β), Entamoeba histolytica antibody, and Aspergillus fumigatus antibody. MELISA could be an excellent substitute for time-consuming conventional ELISA for rapid diagnosis of diseases in cases of medical urgency, outbreak of infectious diseases, and screening of samples in blood banks or emigration counters.