Q6. Remember there are two cysteine molecules incorporated into one luciferin molecule. The yield is 4.32%. This maximum is reached after one day of incubation.

Ql. The oleandrin, which contains an acetate group, was labelled with the trideuterated acetate and this has passed unchanged from plant to aphid to ladybird.

Q2. The alkaloids are extracted from the plant, reduced to free bases, re-oxidized using lsO and fed to the insect. Later the alkaloids are extracted from the insect and examined by mass spectrometry. If the 180 is still intact, there will be a distinct M+2 ion in the spectrum. Q3. There should be enhancement of the peaks for the two labelled carbon atoms in the 13C NMR spectrum and there should be 13C-13C coupling. Q4. There was 0.002% conversion.

Q5. Since romallenone is probably a carotene degradation product from the carotenes in the leaves on which the grasshopper feeds, the isophorone and the trimethylcyclohexendione are from the same source. It is difficult to see how verbenone can be formed in the same way, so it has either been made by the grasshopper or from a monoterpene in its food.

The Bonus Question

The average volume of an amino-acid in silk is 2.4 x 10~22 m, and the volume of 1 cm of a silk fibre is 8.66 x 1014 m. Therefore there are approximately 360,000,000 molecules per cm length and this number added per second per fibre. The fibres are actually hollow, so a minimum dimension for the fibre has been used. Fibre dimensions vary from 0.023 to 0.009 mm during the spinning process

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