Biochromatograms showing 6-APA

Contact photograph print of paper strip biochromatograms, illustrating the conversion of ‘penicin’ (later known as 6-APA or 6-aminopenicillanic acid) in P.chrysogenum brew of various penicillins, original chromatograms by F R Batchelor, 21 June 1957 at Beecham Research Laboratories

Biochromatograms are an example of chromatographs which show the separation of peptides and proteins. In this example, paper strip chromatograms were laid on sheets of agar on large glass plates seeded with Bacillus sublitis and incubated overnight. The dark zones are areas of inhibited bacterial growth (i.e. clear areas letting light through to a sheet of photographic paper placed underneath and illuminated from above).

Strip 1 is labelled original no precursor brew refereeing to the fact that P. chrysogenum was grown in a peanut meal based culture medium without the addition of a precursor acid. Strip 2 shows an analysis of what was left behind after the culture brew had been extracted with butyl acetate when the brew was adjusted to pH3, leaving behind 6-APA (no showing an antibacterial zone as not sufficiently bio active). Strip 3 shows what happened when the culture brew after extraction with butyl acetate at pH3 was treated with phenylacetyl chloride, showing the formation of the benzylpenicillin from the 6-APA showing as a large zone half way up the chromatogram.

This research In 1957 by the team at Beecham Research Laboratories led to the development of several semi-synthetic penicillins. By tweaking 6 aminopenicillanic acid's chemical structure, scientists created medicines to treat a wider range of bacterial infections, with fewer side effects.

Frank Ralph Batchelor (1931-2021), Frank Doyle (1921-2006), John Nayler and George Rolinson (1928-2016) published their results in the journal Nature. Their careers focused on antibiotics, remaining at Beechams for most of their working lives.