{'fraction_non_alphanumeric': 0.025100401606425703, 'fraction_numerical': 0.002008032128514056, 'mean_word_length': 5.116564417177914, 'pattern_counts': {'":': 0, '<': 0, '<?xml version=': 0, '>': 0, 'https://': 0, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 0, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
All individual domains of staphylococcal protein A show Fab binding.

The interactions between the individual domains (E, D, A, B and C) of staphylococcal protein A (SPA) and Fc and Fab regions of human immunoglobulins were studied using real-time biospecific interaction analysis. An engineered domain Z, similar to fragment B but with a single glycine to alanine amino acid substitution, was also included in the study. The domains were expressed in Escherichia coli, affinity purified and immobilised onto sensor chip surfaces in a directed manner using a unique C-terminal cysteine residue engineered into the recombinant proteins. All domains bound to a recombinant human IgG1 Fc fragment with similar strength. For the first time, binding to human Fab was demonstrated for all native SPA domains, using both polyclonal F(ab')2 and a recombinant scFv fragment as reagents. Interestingly, the engineered Z domain showed a considerably lower affinity for Fab as compared to the native domains.