Use Of Secondary Antibodies Research Articles

Introduction of expanded tools for spatial biology applications

Abstract Fluorescence labelling is a highly versatile approach to immunohistochemistry (IHC), offering the ability to detect numerous targets simultaneously with excellent sensitivity and specificity. Currently, the fluorescent labelling method utilized for IHC is the use of secondary antibodies. This multi-step process is restricted by targets that share the same species isotype, limiting the number of targets possible in one sample. Another method used for multiplex staining is cyclic labeling, the process of staining and stripping a tissue sample with different antibodies to detect multiple targets. This process is time-consuming and increases the risk of tissue damage or loss of antigenicity. Our new reagents will enable researchers to stain in fewer steps with preserved antigenicity, ensuring accurate and reliable detection of target antigens in tissue samples. One of the key benefits of these products is the ability to achieve higher-plex labeling, allowing researchers to multiplex with 8-10 biological targets on a single sample in one staining cocktail. This reduces the need for cyclic labeling, streamlines the workflow, and reduces overall time required for analysis. We provide a process that enables successful detection of multiple protein markers across diverse tissue organs while simultaneously detecting transcriptomic targets, providing comprehensive insights into complex biological processes and disease mechanisms. Intended for research use only.

Facile construction of sandwich ELISA based on double-nanobody for specific detection of α-hemolysin in food samples

α-hemolysin (Hla), a toxin secreted by Staphylococcus aureus (S. aureus), has been proved to be involved in the occurrence and aggravation of food poisoning. Hence, it is quite essential to establish its rapid detection methods to guarantee food safety. Sandwich ELISA based on nanobody is well known to be viable for toxins, but there is absence of nanobody against Hla, let alone a pair for it. Therefore, in this paper, we screened specific nanobodies by bio-panning and obtained the optimal nanobody pair for sandwich ELISA firstly. Then, RANbody, a novel nanobody owning both recognition and catalytic capability, is generated in a single step and at low cost through molecular recombination technology. Subsequently, sandwich ELISA was developed to detect Hla based on the nanobody and RANbody, that not only eliminated the use of secondary antibodies and animal-derived antibody, but also reduced detection time and cost, compared with traditional sandwich ELISA. Lastly, the performance has been evaluated, especially for specificity which showed no response to other hemolysins and a low limit of detection of 10 ng/mL. Besides, the proposed sandwich ELISA exhibits favorable feasibility and was successfully employed for the detection of Hla in milk and pork samples.

TRIM21 chimeric protein as a new molecular tool for multispecies IgG detection

BackgroundThe production of monoclonal antibodies for immunoglobulin detection is not cost-effective, while polyclonal antibody production depends on laboratory animals, raising concerns on animal welfare. The widespread use of immunoglobulins in the pharmaceutical industry and the increasing number and variety of new antibodies entering the market require new detection and purification strategies. The Tripartite motif-containing protein 21 is a soluble intracellular immunoglobulin G receptor that binds to the constant region of immunoglobulin G from various species with high affinity. We hypothesized that using this protein as an antibody-binding module to create immunoglobulin detection probes will improve the portfolio of antibody affinity ligands for diagnostic or therapeutic purposes. ResultsWe created a chimeric protein containing a mutated form of the C-terminal domain of mouse Tripartite motif-containing protein 21 linked to streptavidin to detect immunoglobulin G from various species of mammals. The protein is produced by heterologous expression and consists of an improved molecular tool, expanding the portfolio of antibody-affinity ligands for immunoassays. We also demonstrate that this affinity ligand may be used for purification purposes since imidazole elution of antibodies can be achieved instead of acidic elution conditions of current antibody purification methods. ConclusionData reported here provides an additional and superior alternative to the use of secondary antibodies, expanding the portfolio of antibodies affinity ligands for detection and purification purposes.

Development of nanobody-horseradish peroxidase-based sandwich ELISA to detect Salmonella Enteritidis in milk and in vivo colonization in chicken

BackgroundSalmonella Enteritidis (S. Enteritidis) being one of the most prevalent foodborne pathogens worldwide poses a serious threat to public safety. Prevention of zoonotic infectious disease and controlling the risk of transmission of S. Enteriditidis critically requires the evolution of rapid and sensitive detection methods. The detection methods based on nucleic acid and conventional antibodies are fraught with limitations. Many of these limitations of the conventional antibodies can be circumvented using natural nanobodies which are endowed with characteristics, such as high affinity, thermal stability, easy production, especially higher diversity. This study aimed to select the special nanobodies against S. Enteriditidis for developing an improved nanobody-horseradish peroxidase-based sandwich ELISA to detect S. Enteritidis in the practical sample. The nanobody-horseradish peroxidase fusions can help in eliminating the use of secondary antibodies labeled with horseradish peroxidase, which can reduce the time of the experiment. Moreover, the novel sandwich ELISA developed in this study can be used to detect S. Enteriditidis specifically and rapidly with improved sensitivity.ResultsThis study screened four nanobodies from an immunized nanobody library, after four rounds of screening, using the phage display technology. Subsequently, the screened nanobodies were successfully expressed with the prokaryotic and eukaryotic expression systems, respectively. A sandwich ELISA employing the SE-Nb9 and horseradish peroxidase-Nb1 pair to capture and to detect S. Enteritidis, respectively, was developed and found to possess a detection limit of 5 × 104 colony forming units (CFU)/mL. In the established immunoassay, the 8 h-enrichment enabled the detection of up to approximately 10 CFU/mL of S. Enteriditidis in milk samples. Furthermore, we investigated the colonization distribution of S. Enteriditidis in infected chicken using the established assay, showing that the S. Enteriditidis could subsist in almost all parts of the intestinal tract. These results were in agreement with the results obtained from the real-time PCR and plate culture. The liver was specifically identified to be colonized with quite a several S. Enteriditidis, indicating the risk of S. Enteriditidis infection outside of intestinal tract.ConclusionsThis newly developed a sandwich ELISA that used the SE-Nb9 as capture antibody and horseradish peroxidase-Nb1 to detect S. Enteriditidis in the spike milk sample and to analyze the colonization distribution of S. Enteriditidis in the infected chicken. These results demonstrated that the developed assay is to be applicable for detecting S. Enteriditidis in the spiked milk in the rapid, specific, and sensitive way. Meanwhile, the developed assay can analyze the colonization distribution of S. Enteriditidis in the challenged chicken to indicate it as a promising tool for monitoring S. Enteriditidis in poultry products. Importantly, the SE-Nb1-vHRP as detection antibody can directly bind S. Enteritidis captured by SE-Nb9, reducing the use of commercial secondary antibodies and shortening the detection time. In short, the developed sandwich ELISA ushers great prospects for monitoring S. Enteritidis in food safety control and further commercial production.Graphic

Technical steps towards enhanced localization of proteins in cultural heritage samples by immunofluorescence microscopy and micro-reflectance imaging spectroscopy

This study presents the results obtained during the optimization phase of a protocol based on immunofluorescence microscopy (IFM) with the aim to characterize and localize proteins in fluid-rich samples of cultural heritage interest.Chicken serum albumin from chicken blood was considered the primary target. Ovalbumin from chicken egg albumen (egg white) was also used as a common target protein to test the versatility of the protocol. Mock-ups were created, obtaining a complex distribution of the proteins in a porous matrix, thus providing a good approximation to a real case scenario. Thin sections of 1 µm thickness were then obtained using a cyanoacrylate-based tissue adhesive for the first time in samples of cultural heritage interest. Thin sections were preferred over standard cross sections, as they enabled multiple experiments to be performed by easily generating multiple sections from the same sample. This was particularly important during the optimization phase of the indirect immunochemical procedure, as the concentration of the blocking solutions, primary and secondary antibodies had to be optimized as well as the washing steps, time and temperature of incubation. The use of secondary antibodies conjugated with quantum dots fluorophores and the use of single wavelength structured illumination in the fluorescence microscope set-up reduced the contribution from unspecific fluorescence.All these technical advances led to the enhanced mapping of the distribution of both ovalbumin and chicken serum albumin in the mock-up samples. The material distribution was also mapped using micro-reflectance imaging spectroscopy, which confirmed the localization of the target materials, thus laying the foundation for a multi-modal imaging protocol, which will be applied to samples taken from fluid-rich patinas on West African sculptures.

Nanobody\u2011horseradish peroxidase and -EGFP fusions as reagents to detect porcine parvovirus in the immunoassays

BackgroundAntibodies are an important reagent to determine the specificity and accuracy of diagnostic immunoassays for various diseases. However, traditional antibodies have several shortcomings due to their limited abundance, difficulty in permanent storage, and required use of a secondary antibody. Nanobodies, which are derived from single-chain camelid antibodies, can circumvent many of these limitations and, thus, appear to be a promising substitute. In the presented study, a sandwich ELISA-like immunoassay and direct fluorescent assay with high sensitivity, good specificity, and easy operation were the first time to develop for detecting porcine parvovirus (PPV). After screening PPV viral particles 2 (VP2) specific nanobodies, horseradish peroxidase (HRP) and enhanced green fluorescent protein (EGFP) fusions were derived from the nanobodies by recombinant technology. Finally, using the nanobody-HRP and -EGFP fusions as probes, the developed immunoassays demonstrate specific, sensitive, and rapid detection of PPV.ResultsIn the study, five PPV-VP2 specific nanobodies screened from an immunised Bactrian camel were successfully expressed with the bacterial system and purified with a Ni–NTA column. Based on the reporter-nanobody platform, HRP and EGFP fusions were separately produced by transfection of HEK293T cells. A sandwich ELISA-like assay for detecting PPV in the samples was firstly developed using PPV-VP2-Nb19 as the capture antibody and PPV-VP2-Nb56-HRP fusions as the detection antibody. The assay showed 92.1% agreement with real-time PCR and can be universally used to surveil PPV infection in the pig flock. In addition, a direct fluorescent assay using PPV-VP2-Nb12-EGFP fusion as a probe was developed to detect PPV in ST cells. The assay showed 81.5% agreement with real-time PCR and can be used in laboratory tests.ConclusionsFor the first time, five PPV-VP2 specific nanobody-HRP and -EGFP fusions were produced as reagents for developing immunoassays. A sandwich ELISA-like immunoassay using PPV-VP2-Nb19 as the capture antibody and PPV-VP2-Nb56-HRP fusion as the detection antibody was the first time to develop for detecting PPV in different samples. Results showed that the immunoassay can be universally used to surveil PPV infection in pig flock. A direct fluorescent assay using PPV-VP2-Nb12-EGFP as a probe was also developed to detect PPV in ST cells. The two developed immunoassays eliminate the use of commercial secondary antibodies and shorten detection time. Meanwhile, both assays display great developmental prospect for further commercial production and application.

Δ-Tetrahydrocannabinol Increases Dopamine D1-D2 Receptor Heteromer and Elicits Phenotypic Reprogramming in Adult Primate Striatal Neurons.

SummaryLong-term cannabis users manifest deficits in dopaminergic functions, reflecting Δ9-tetrahydrocannabinol (THC)-induced neuroadaptive dysfunctional dopamine signaling, similar to those observed upon dopamine D1-D2 heteromer activation. The molecular mechanisms remain largely unknown. We show evolutionary and regional differences in D1-D2 heteromer abundance in mammalian striatum. Importantly, chronic THC increased the number of D1-D2 heteromer-expressing neurons, and the number of heteromers within individual neurons in adult monkey striatum. The majority of these neurons displayed a phenotype co-expressing the characteristic markers of both striatonigral and striatopallidal neurons. Furthermore, THC increased D1-D2-linked calcium signaling markers (pCaMKIIα, pThr75-DARPP-32, BDNF/pTrkB) and inhibited cyclic AMP signaling (pThr34-DARPP-32, pERK1/2, pS845-GluA1, pGSK3). Cannabidiol attenuated most but not all of these THC-induced neuroadaptations. Targeted pathway analyses linked these changes to neurological and psychological disorders. These data underline the importance of the D1-D2 receptor heteromer in cannabis use-related disorders, with THC-induced changes likely responsible for the reported adverse effects observed in heavy long-term users.

Protein Binders Specific for Immunoglobulin G from Different Species for Immunoassays and Multiplex Imaging.

An immunoassay is the most widely used method for analyzing a variety of analytes based on antigen-antibody interactions in the biological and medical sciences. However, the use of secondary antibodies has certain shortcomings, such as a high cost, cross-reactivity, and loss of binding affinity during labeling. Herein, we present the development of repebodies specifically binding to immunoglobulin G with a different origin, which is a small-sized nonantibody scaffold composed of leucine-rich repeat (LRR) modules, for use in immunoassays and imaging. Repebodies specific for IgG from different species (i.e., mouse, human, and rabbit) were selected through a phage display, and their affinities were matured using a modular engineering approach. The respective repebodies were labeled with various signal generators such as horseradish peroxidase (HRP), a fluorescent dye, and quantum dots, and the resulting repebodies were used as alternatives to conventional secondary antibodies in typical immunoassays and imaging. The labeled repebodies enabled the detection of diverse target analytes with high sensitivity and specificity, showing a negligible cross-reactivity. Moreover, the repebodies labeled with different color-emitting quantum dots allowed the imaging of cell-surface receptors and proteins in a multiplex manner. The developed repebodies can be effectively used for sensitive immunoassays and multiplex imaging.

Surface Plasmon Resonance (SPR) Sensing Based on DNA Elongation by Site-Selective Surface Plasmon (SP) Field Heating toward Ultra-High Sensitive Detection of Single Pathogenic Particles

The purpose of this work is to realize a novel enhancement method for surface plasmon resonance (SPR) sensing based on DNA elongation by surface plasmon (SP) field heating which shows promise for the detection of single pathogenic particles such as viruses and bacteria. The biosensor based on SPR is a powerful analytical tools for biological studies because it can monitor molecular interactions with high sensitivity and in a quantitative manner in real-time. The principle of a SPR sensor is based on the detection of the change in the dielectric constant on the surface due to the ligand-analyte binding. However, the change upon the 1:1 binding may be too small for detection of analytes at high dilutions. To address this limitation, some additional procedures have been proposed and applied: for example, the use of secondary antibody with gold colloid and DNA elongation from the analyte by using rolling circle amplification (RCA) induced by homogeneous heating (1). However, most of these methods have their associated limitations with respect to sensitivity enhancement mainly due to the non-specific binding of the additives, thereby increasing the background signal level. In the present study, we propose a novel sensitivity enhancement method for SPR analysis based on the DNA elongation by site-specific SP heating. Our concept is summarized in Fig. 1(a). At the SPR condition, the almost incident light energy is transferred to the SPs and finally converted to heat. Practical SPR biosensor systems employ a dim excitation light because the resulting heat disturbs the detection. In contrast, we intentionally employ a high-power laser as a light source to generate enough heat to drive the DNA polymerase. The SPR angle increases with increasing the amount of the bound analyte. Accordingly, when we illuminate the high power p-polarized laser at an incident angle (q’) greater than the SPR angle for the ligand (q), the SP fields should be effectively generated at the analyte binding site and the resulting heat can induce site-selective DNA elongation from the primers immobilized on/around the analytes. The amplified DNA (amplicons) elongating on/around the analytes could more effectively contribute to the shift of the SPR angle than the analytes themselves initially bound by the ligands. The amplicons can be detected not only by the shift of the SPR angle but also by SP enhanced fluorescence measurement, in which the number of the incorporated fluorophore is several thousands times larger than that of the analytes. We have employed RCA as a method for DNA elongation, in which the replication isothermally occurs from a small primer using a circular template and a polymerase with a strand displacement activity. A 50 nm gold film on a cover slip was immersed in a 1 mM dimethylformamide (DMF) solution of dithiobis-(succinimidyl undecanoate) and the resulting succinimidyl self-assembly monolayer (SI-SAM) was used for immobilization of the molecules. Site-selective SP heating was carried out by the multispot analysis. Anti-bovine serum albumin antibody (anti-BSA) and anti-mouse IgG were used as the ligand and the control, respectively. The four spots, consisting of two sets of two spots (one ligand and one control) with a 1-mm diameter, one ligand and one control, were prepared on the SI-SAM. The spots were covered with a 6-mm silicone rubber well and immersed in the solution of the analyte, which is primer-immobilized BSA. Then, the mixture solution of a circular template (M13mp18), 96-7 polymerase, and the nucleotide mixture was injected into the well. SP field heating was performed by illumination for 60 min with p-polarized laser (808 nm, 300 mW) at the upper-half area of the well at an offset angle of approximately +2° from the SPR angle. After the SP heating, the amplicons were stained with SYBR-Green I and observed by the confocal microscope and the SP enhanced fluorescence imager. The fluorescence from the analyte-bound and SP heated ligand spot was more intense than that of the control spot (Fig. 1(b) and (c)). This result indicates that, upon binding BSA, the ligand spots absorbed the excitation light and got heat from SP field more effectively than the control spot, which rapidly induces enzymatic DNA elongation giving the enhanced SPR and fluorescence signals. We have applied this method to the pathogenic particle detection. The intense fluorescence spots of the amplicons were observed around the 3-micrometer polystyrene latex beads as the dummy pathogen suggesting the site-selective heating around the particles. Further experimental data and detailed discussion will be presented. Reference 1. Y. Huang, H. Hsu, and C. C. Huang, Biosens. Bioelect., 22, 2007, 980-985. Figure 1

Identification of Connexin43 Phosphorylation and S-Nitrosylation in Cultured Primary Vascular Cells.

All connexins (Cx) proteins contain both highly ordered domains (i.e., 4 transmembrane domains) and primarily unstructured regions (i.e., n- and c-terminal domains). The c-terminal domains vary in length and amino acid composition from the shortest on Cx26 to the longest on Cx43. With the exception of Cx26, the c-terminal domains contain multiple sites for posttranslational modification (PTM) including serines (S), threonines (T), and tyrosines (Y) for phosphorylation or cysteines (C) for S-nitrosylation. These PTMs are critical for regulating cellular localization, protein-protein interactions, and channel functionality. There are several biochemical techniques that allow for the identification of these PTM including Western blotting and the "Biotin Switch" assay for nitrosylation. Quantitative analysis of Western blots can be achieved through use of secondary antibodies in the near infrared scale and high-resolution scanning on a fluorescent scanner.

Photoluminescent lateral-flow immunoassay revealed by graphene oxide: highly sensitive paper-based pathogen detection.

A paper-based lateral flow immunoassay for pathogen detection that avoids the use of secondary antibodies and is revealed by the photoluminescence quenching ability of graphene oxide is reported. Escherichia coli has been selected as a model pathogen. The proposed device is able to display a highly specific and sensitive performance with a limit of detection of 10 CFU mL(-1) in standard buffer and 100 CFU mL(-1) in bottled water and milk. This low-cost disposable and easy-to-use device will prove valuable for portable and automated diagnostics applications.

Recognition of a monoclonal antibody against a small molecular weight antigen by monitoring the antigen–antibody reaction using fluorescence labeled structured peptides

Interaction between proteins (as analytes) and de novo designed structured peptides as capture molecules cause structural changes, which are reflected in fluorescent-intensity changes of labeled peptides in a dose dependent manner. In contrast to conventional detection methods our detection system does not involve the detection of specific molecules themselves in a 1:1 manner, but uses the principle of the differences in fluorescent intensity changes of capture peptides upon addition of analytes. Instead of the use of secondary antibodies we have attempted monitoring these structural changes by an array of de novo designed synthetic and structured peptides. In the present study we have focused on a recognition system, 5-fluorouracil, as a low molecular antigen and a monoclonal antibody against 5-FU. The fluorescent intensity changes of fluorescent labeled peptides have been measured after incubation with a monoclonal antibody and again after further incubation with the antigen, 5-FU. Unique intensity changes were found for several peptides in the fluorescent peptide library that allowed the visualization as a color-coded protein fingerprint. The peptide screen used in the present study offers a useful detection system as capture molecules for peptide-based microarrays.

Abstract 47: Development and Use of a Novel Single-Cell Epigenetic Lineage Tracing Method to Identify Smooth Muscle--Derived Macrophage-Like Cells Within Human Atherosclerotic Lesions

Aim: Smooth muscle cells (SMC) possess remarkable phenotypic plasticity that allows adaptation to changing environmental cues. Lack of definitive SMC lineage tracing studies and inability to identify phenotypically modulated SMCs within lesions due to loss of SMC marker gene expression raise major questions regarding the role of SMC in vivo in atherosclerosis progression. We hypothesize that a subset of cells within lesions that express macrophage markers are derived from SMC not monocytes and play a key role in determining plaque stability. Methods: We developed a novel lineage tracing based on detection of H3K4dime of the SM MHC gene, a SMC-specific epigenetic lineage marker we have previously shown is stable during phenotypic switching in vitro. Detection of H3K4dime of the SM MHC locus was done using a Proximity ligation assay (PLA) developed in our lab with an antibody targeting the biotinylated DNA probe for the SM MHC locus in conjunction with an anti-H3K4dime antibody. Use of secondary antibodies conjugated with oligonucleotides induces formation of circular DNA that serve as template for amplification, allowing visualization of co-localization of H3K4dime and the SM MHC gene (Duolink). Our new lineage tracing is suitable with human paraffin-embedded tissue sections (n=4) allowing investigation of SMC fate within human atherosclerotic lesion. Results: H3K4dime on the SM MHC gene (PLA+ cells) was found to be specific for SMCs and not found in any other cell types including adventitial fibroblasts, or endothelial cells. The method was validated using a SMC-specific lineage tracing mouse model wherein SM MHC Cre mice are crossed to ROSA flox STOP eYFP+/+ ApoE -/- mice. The H3K4dime/SM MHC PLA signal (i.e. PLA+) was exclusively found in eYFP+ cells. Moreover, some of the lesion SMCs were eYFP+/PLA+/SM α-actin-. Similarly, we identified PLA+ cells in human lesions that were positive for the macrophage marker CD68. Conclusion: Our new method permits definitive identification of SMC-derived cells within lesions even if they are not identifiable as SMC due to loss of SMC markers. Moreover, we provide exciting evidence that a significant fraction of macrophage-like cells in human lesions are derived from SMC. We postulate that transition of SMC to a macrophage state may be a key event leading to plaque destabilization and rupture with possible myocardial infarction or stroke.

Abstract 4394: Development of parallel conjugation and assay methodologies to screen for antibodies with optimal properties for use as antibody-drug conjugates

Abstract The activity of antibody-drug conjugates (ADCs) on cancer cells can be affected by a multitude of factors, such as binding affinity, rate of internalization, subcellular trafficking, and efficient drug release within the target cell population. Consequently, the properties of an ideal antibody for drug delivery are not necessarily the same as those for a therapeutic naked antibody. Furthermore, the use of indirect assays involving the use of secondary antibodies to screen for optimal ADCs can be misleading, since crosslinking on the cell surface can lead to altered downstream events, and the affinity of the secondary antibody constrains the dynamic range of the assay. When seeking candidate antibodies directed against a novel antigen for ADC therapy, it is therefore most desirable to screen a large panel in the form of ADCs and evaluate their cytotoxic activities, since these results provide a direct measurement of parameters that can affect cytotoxic activity. However, when dealing with microgram quantities of a large number of antibodies as is typical of an antibody discovery campaign, the yields from conventional conjugation methodologies are limiting. We developed a novel approach that addresses this issue and have successfully applied it to the discovery of optimal ADCs out of a large panel of candidate antibodies. The technology is currently being applied to the discovery of ADCs against antigens of interest for targeted drug delivery. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 4394.

Life and Death of Cardiac Stem Cells

The recognition that myocyte mitosis occurs in the fetal, neonatal, adult, and hypertrophied heart and that a pool of primitive, undifferentiated cells is present in the myocardium has put forward a different view of the biology of the heart. The new paradigm suggests that myocyte formation is preserved during postnatal life, in adulthood or senescence, pointing to a remarkable growth reserve of the heart throughout the course of life of the organism. This article reviews a large body of novel information, which has been obtained in the last 2 decades, in favor of the notion that the mammalian heart has the inherent ability to continuously replace its parenchymal cells and that this unexpected characteristic has important implications in understanding myocardial homeostasis, cardiac aging, and tissue repair. The paradigm that the heart is a postmitotic organ incapable of regenerating parenchymal cells was established in the 1970s, and this dogma has profoundly conditioned basic and clinical research in cardiology for the last 3 decades. On the basis of this paradigm, cardiomyocytes undergo cellular hypertrophy1,2 but cannot be replaced either by entry into the cell cycle of a subpopulation of nonterminally differentiated myocytes or by activation of a pool of primitive cells that become committed to the myocyte lineage. The only response of cardiomyocytes to stress is hypertrophy and/or death. Therefore, a tremendous effort was made to identify the molecular mechanisms of myocyte hypertrophy and their genetic control. A sophisticated knowledge of various signaling pathways has been achieved, and our understanding of the biology of hypertrophic myocyte growth has advanced markedly.3 An array of new technologies has been introduced that has led to a scientific revolution in terms of questions, approaches, and interpretation of experimental results. Despite this enormous progress in our understanding of basic mechanisms of hypertrophy, however, very little …

Sensitivity enhancement of surface plasmon resonance biosensing of small molecules

Surface plasmon resonance (SPR) biosensor formats using gold nanoparticle or protein signal amplification for the sensitive assay of small molecules were developed using progesterone as a model compound. Progesterone was immobilized to a dextran surface in the Biacore biosensor through in situ covalent immobilization using an oligoethylene glycol linker attached to the 4 position of the steroid. This surface produced stable antibody binding for in excess of 1100 assay cycles. Using this surface, assays were developed for progesterone using 10- and 20-nm gold–streptavidin labels attached to biotinylated monoclonal antibody in both label prebinding and sequential binding formats. Prelabeling formats gave no signal enhancement but produced assays with limits of detection of 143 pg/ml, compared with approximately 1 ng/ml in previous studies. Sequential binding formats gave signal enhancements of 2.2-fold over the monoclonal antibody and a limit of detection of 23.1 pg/ml. It was found that secondary antibody labeling gave 8.1-fold signal enhancements and a limit of detection of 20.1 pg/ml, whereas use of secondary antibody–25 nm gold complexes provided more signal enhancement (13-fold) and a further improvement in limit of detection of 8.6 pg/ml.

A new protein conjugate that replaces the use of secondary antibodies engineered from the two staphylococcal enzymes protein A and 6-phospho-beta-galactosidase.

The lacG gene encoding the 6-phospho-beta-galactosidase (E.C.3.2.1.85) of Staphylococcus aureus was fused to the protein A gene in the plasmid pRIT2T. Escherichia coli cells containing this plasmid produce a fusion protein with both IgG binding and 6-phospho-beta-galactosidase activities after heat induction. The recombinant gene was overexpressed and the hybrid protein was purified to homogeneity in high yield. The chimeric protein was shown to have almost identical enzymatic characteristics to pure 6-phospho-beta-galactosidase. This result leads to the conclusion that a free N-terminus of the 6-phospho-beta-galactosidase is not required for biological activity. The hybrid protein of protein A and 6-phospho-beta-galactosidase was used as an enzyme conjugate in enzyme-linked immunosorbent assays (ELISA). The experiments presented demonstrate that the 6-phospho-beta-galactosidase is a suitable fusion partner in various diagnostic applications where an unique biological activity is required.

Negative staining in the detection of viruses in clinical specimens

Viruses have unique morphology and are therefore good candidates for negative staining. Negative staining with phosphotungstic acid (PTA) or uranyl acetate has facilitated the detection of many viruses in clinical specimens. Enhancement procedures have included the use of centrifugation and agar diffusion for concentrating virus particles, the use of solid phase capture reagents to trap virus particles and the use of secondary antibodies and electron dense markers to help visualize them. Techniques currently in use and employing negative staining include direct EM, immune electron microscopy (IEM), solid phase immune electron microscopy (SPIEM), colloidal gold-labeled protein A (PAG), solid phase IEM employing a second decorator antibody (SPIEMDAT), and solid phase IEM using colloided gold-labeled secondary antibodies (SPEIMDAGT). IEM methods assist with the detection of small viruses or viruses present in low numbers while PAG offers increased sensitivity over direct EM and IEM. In our experience the serum-in-agar (SIA) method is the most sensitive of the PAG IEM techniques for detection of rotavirus particles in clinical specimens. SPIEMDAT enhances the detection of small viruses which are often missed by other techniques due to background staining in specimens. SPEIMDAGT employing colloidal gold-labeled secondary antibody has increased sensitivity and offers the advantage of detecting viral antigen when whole virus particles are not visible. IEM techniques have recently been used for typing viruses using either monospecific antisera or monoclonal antibodies and colloidal gold-labeled secondary antibody.

Use of secondary antibodies for visualization of bound primary reagents in blotting procedures

AbstractSecondary antibodies are used for visualization of bound primary ligands in blotting procedures in several formats. The term “secondary antibody” usually denotes an anti‐immunoglobulin from a species different from the one producing the primary antibody. This secondary antibody is modified so as to produce a visible signal by conjugation with enzyme, fluorophore, radioisotope or suitable particulatematerial. The characteristics of these antibodies will influence both sensitivity and specificity of the assays in which they are used. Thorough knowledge of these characteristics is thus needed for critical evaluation of results. This paper discusses the production and reactivity of secondary antibodies, their immunochemistry and their possible side reactions. Alternative secondary reagents are also discussed with respect to specificity and sensitivity.