e-ISSN 2231-8542
ISSN 1511-3701

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A Competitive ELISA for Quantification of Protein A in Culture Medium

Abdul Manaf Ali1 Sharifah Tahir, Baharuddin Abdul Ghani, Ungku Chulan and Ismail B. Ahmad

Pertanika Journal of Tropical Agricultural Science, Volume 19, Issue 2&3, December 1996

Keywords: protein A, competitive ELISA, IgG, Staphylococcus aureus

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A competitive enzyme-linked immunosorbent assay (ELISA) for quantification of protein A produced by Staphylococcus aureus A676 (a methicillin-resistant strain) was based on competitive binding to rabbit IgG molecules between alkaline phosphatase-labelled protein A and unlabelled protein A. The optimum IgG concentration required for coating was 2-4 fig I ml. The optimum incubation time for colour development using (p-nitrophenol phosphate substrate was 20-30 min. The lowest protein A concentration that could be measured using the optimized competitive ELISA was 20 ng/ml, and the maximum 2 fig I ml. The amount of protein A produced in brain-heart infusion medium increased exponentially during log phase of cell growth, reaching a maximum concentration of 22.5 fig I ml after 15 h cultivation.

ISSN 1511-3701

e-ISSN 2231-8542

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