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Surfaces and Immobilisation Strategies for Use in Immunoassay Development
Published in Richard O’Kennedy, Caroline Murphy, Immunoassays, 2017
In SPR-based analyses a number of proteins were immobilised and were also shown to be effective in a fluorescence-based microarray. The authors demonstrated an operational strategy for preparing the associated chips with controllable antibody density. Scholler and co-workers utilised yeast mating to generate in vitro biotinylated antibody fragments. These ‘biobodies’ were generated by first screening a library for anti-HE4 scFv (ovarian cancer marker) followed by mating with haploid yeast carrying a biotin ligase sequence. The generated constructs were readily used on biotinylated alkaloid-based surfaces which took advantage of the multiple biotin-binding sites available on streptavidin to capture the biobodies for characterisation [67]. In a similar approach, Even-Desrumeaux and co-workers developed a bead-based sandwich assay using novel single-domain antibody fragments (sdAbs), which are the VHH domain antibodies from camelids. In this study, in vivo biotinylation was achieved in E. coli facilitating direct spotting of bacterial lysates for sandwich assay development for the purposes of developing high-throughput antibody-based diagnostic arrays. This bead-based approach has potential for multiplexing and is an attractive approach for low-density clinical-diagnostic arrays [68].
Beta and Alpha Particle Autoradiography
Published in Michael Ljungberg, Handbook of Nuclear Medicine and Molecular Imaging for Physicists, 2022
Anders Örbom, Brian W. Miller, Tom Bäck
Recent example studies using alpha autoradiography in pre-clinical research include Al Darwish and colleagues demonstrating autoradiography of tumour sections using a Timepix sensor (see Figure 30.18B) in a 227Th TAT study comparing mice treated with TAT and TAT combined with chemotherapy. Dekempeneer and colleagues evaluating the efficacy of single-domain antibody fragments (sdAb) labelled with the α-emitter 213Bi (45-minute half-life). The iQID was used in biodistribution studies to image and quantify the radioactivity distribution within tumour sections [79].
Glossary of scientific and technical terms in bioengineering and biological engineering
Published in Megh R. Goyal, Scientific and Technical Terms in Bioengineering and Biological Engineering, 2018
Single domain antibody (sdAb, called Nanobody by Ablynx, the developer) is an antibody fragment consisting of a single monomeric variable antibody domain. Like a whole antibody, it is able to bind selectively to a specific antigen. With a molecular weight of only 12–15 kDa, single-domain antibodies are much smaller than common antibodies (150–160 kDa) which are composed of two heavy protein chains and two light chains, and even smaller than Fab fragments (~50 kDa, one light chain and half a heavy chain) and single-chain variable fragments (~25 kDa, two variable domains, one from a light and one from a heavy chain).
COVID-19;-The origin, genetics,and management of the infection of mothers and babies
Published in Egyptian Journal of Basic and Applied Sciences, 2020
Hassan Ih El-Sayyad, Yousef Ka Abdalhafid
Camelids, such as alpacas and llamas are of medical importance due to producing a novel type of heavy chain-antibody specific for production single domain antibodies which are highly selective for different protein antigen. The extracted single domain antibodies can then be used either directly or as part of an engineered reagent. Single domain antibodies can be generated, purified, and directly used in prokaryotic expression system in large quantities as recombinant proteins or can be engineered to contain unique markers as reporters in cellular studies or in diagnostics [148]. During invasion of the human cells, the SARS-CoV-2 receptor-binding domain (RBD) of the spike protein binds to ACE2 receptor. Two nanobodies, H11-D4 and H11-H4, are created with high selective binding to BRD and block their crosslink their ACE2 after application of a naïve IIama single-domain antibody library and PCR-based maturation. The studies illustrate that nanobodies identify the same epitope, which overlaps with the ACE2-binding surface, illustrating the blocking of the RBD-ACE2 interaction [149].
Cytoplasmic and periplasmic expression of recombinant shark VNAR antibody in Escherichia coli
Published in Preparative Biochemistry and Biotechnology, 2019
Herng C. Leow, Katja Fischer, Yee C. Leow, Katleen Braet, Qin Cheng, James McCarthy
In contrast to camelids, immunoglobulin new antigen receptor (IgNAR) is an intra-domain disulfide bond immunoglobulin superfamily protein that provided additional stability without adversely affecting antigen binding efficiency. This protein was naturally discovered from nurse shark (Ginglymostoma cirratum)[5] and wobbegong shark (Orectolobus maculates).[6] Unlike immunoglobulin (Ig) isotypes found in higher mammals, the variable domains of shark IgNAR (VNAR) is an unusual single domain antibody that contains only a single H-chain homodimer and lacks a light chain.[7] According to molecular analysis, the deletion of a large portion of framework region 2-complementarity determining region 2 (FR2-CDR2) has made VNAR the smallest variable domain with a size of ∼12 kDa in the animal kingdom.[7] It may be due to VNARs have evolved from separate lineage from immunoglobulins and thus have never had a CDR2.[8,9]Moreover, VNAR domains possess an extraordinary CDR3 domain which is much longer than that of conventional antibodies. The inter- or intra-loop of CDR3 is typically influenced by the numbers of cysteine residues and the penetration capability into the cleft region of the target antigen.[10,11] Owing to peculiar structure, the excellent solubility and thermostability of these natural single domain fragments may be due to the substitutions of amino acid at heavy and light variable domains (VH-VL) interface, resulting to be more hydrophilicity rather than a hydrophobic interface as exhibited in conventional antibodies.[7,12]
Production of bioactive recombinant monoclonal antibody fragment in periplasm of Escherichia coli expression system
Published in Preparative Biochemistry & Biotechnology, 2023
Preeti Saroha, Anurag S. Rathore
Recombinant biotherapeutic molecules, such as single-domain antibody fragments (dAbs), antigen-binding fragments (Fabs), and single-chain variable fragments (scFvs) are produced in Escherichia coli due to its well-known physiology and genetics. Factors, such as lack of glycosylation, easier production, high expression levels, high cell densities, and low production costs compared to other available expression platforms contribute to popularity of the E. coli platform.