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PARTIAL FIX. "However in the reaction centres, chlorophyll triplet could be formed by short circuits such as charge recombination. Here again carotenoid quenching has been employed where possible but this is clearly insufficient and many mechanisms exist where by these short-circuits are minimised." https://lnkd.in/dxpcWx8 View in LinkedIn

BIG PROBLEM FIX. "When chlorophyll-containing species found themselves in the presence of O2 then there was a big problem. The main fix was to wheel out the carotenoids as quenchers of chlorophyll triplet states and of singlet O2." https://lnkd.in/dxpcWx8 View in LinkedIn

PROBLEMS OF OXYGENATION. "The energy-converting enzymes evolved from ancestral enzymes that functioned in conditions of low O2 concentration or anaerobicity. These ancestral proteins did not have to deal with the inevitable side-reactions (leaks) that occur when O2 is present." https://lnkd.in/dxpcWx8 View in LinkedIn

HURDLES TO LIFE. "The history of life on Earth suggests that there were at least two major hurdles to overcome before complex life developed. The first was biological. The second obstacle for complex life was having sufficient free, diatomic oxygen (O2)." The third was actually coping with an oxygenated atmosphere, and adapting old machinery designed for anoxic conditions. https://lnkd.in/eM8rQZu View in LinkedIn

MODERN SYSTEM INEFFICIENCY. "These protective mechanisms involve fine-tuning of reduction potentials, switching of pathways and the use of short circuits, back-reactions and side-paths, all of which compromise efficiency." https://lnkd.in/dxpcWx8 View in LinkedIn

THE GREAT OXYGENATION EVENT. "It is widely assumed that atmospheric oxygen concentrations remained persistently low (less than 10−5 times present levels) for about the first 2 billion years of Earth’s history. The first long-term oxygenation of the atmosphere is thought to have taken place around 2.3 billion years ago, during the Great Oxidation Event." https://lnkd.in/euqjmtw View in LinkedIn

FINGER IN THE DYKE. "The tuning of electron transfer needed to deal with leaks and damaging back-reactions seems to be a requirement associated with life in the presence of oxygen." https://lnkd.in/dxpcWx8 View in LinkedIn

FRAGMENT FROM NATURE deals with some examples of how changes in the environment could have made many molecular mechanisms redundant without considerable molecular exaptation and serious work-around and bolt-ons, just as had happened with physical structures like feet. Here we see photosynthetic futile cycles and carefully positioned carotenoids operating as adaptations to the challenges of an oxygenated atmosphere. View in LinkedIn

BOLT-ON SOLUTIONS. "These features evolved in ancestral enzymes in a low O2 environment. When O2 appeared, energy-converting enzymes had to deal with its troublesome chemistry. Various protective mechanisms duly evolved that are not directly related to the enzymes’ principal redox roles." https://lnkd.in/dxpcWx8 View in LinkedIn

Johnson & Johnson to pay $4.7bn damages in talc cancer case. The family company. http://www.bbc.co.uk/news/business-44816805 View in LinkedIn