Sir

Your News Feature 'The photon trap' (Nature 452, 400–402; 2008) makes good points about the challenges for converting solar to fuel energy by artificial photosynthesis. But we wish to clarify the assessment that “simply mimicking photosynthesis is too short-sighted”.

The (highly optimistic) 3% efficiency for solar energy conversion in plants covers everything that a plant gets up to, day and night, during an annual cycle. The whole complex process of photosynthesis, not to mention the plant's way of life, is certainly not a target for chemical mimicry. Biologically inspired chemistry based on photosynthesis focuses only on the specific reactions that are potentially useful.

Early aviation pioneers, who looked to birds for biomimetic aeroplane design features, incorporated wings, a tail, a fuselage and aspects of aerodynamics into their final product. In the main, they chose not to go for flapping — and nest-building and flying south for the winter were right out. Biomimetic chemistry is the same: we pick only the relevant bits.

The water-oxidizing enzyme you feature is currently the focus of attention — a chemical marvel in which a low-energy pathway removes electrons from water so that the enzyme can operate at minimum electrical over-potential. Its high energy-conversion efficiency is unmatched by artificial catalysts derived from cheap and abundant elements.

Your News Feature implies that research on this enzyme has advanced to the point where it can provide a legitimate target for catalyst-hunting chemists to mimic. This is true, but there is still a good deal to be learned about the structure and mechanism of the enzyme itself and this will doubtless be of great benefit to future research on artificial photosynthesis.