Month: September 2022

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

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

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

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

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

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

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

CHANGING MACHINERY TO FIT NEW ENVIRONMENT. "Some of the key features of the bioenergetic redox enzymes can thus be understood from an evolutionary viewpoint, where enzymes that were already optimised for productive energy conversion in an anaerobic or low O2 environment had to compromise efficiency in order to survive the arrival of O2." https://lnkd.in/dxpcWx8 View in LinkedIn

CHEMISTRY AND POSITION FIXES. "The very high potentials involved in water photolysis can result in the adventitious oxidation of nearby organic species in and around the PSII reaction centre. To work as quenchers of chlorophyll triplets, carotenoids need to be very close, van der Waals contact is typical. Thus carotenoids cannot protect the core chlorophylls in PSII and indeed the crystal structure verified this prediction." (PSII = photosystem II) https://lnkd.in/dxpcWx8 View in LinkedIn

VARIATIONS ON A FIX THEME. "This inefficient Cyt b 559-mediated cycle has been proposed to protect against oxidative damage caused by inline image or by Car +. In marine plankton a much more efficient futile cycle exists under high light. This may represent a souped-up version of the Cyt b 559 cycle described here." https://lnkd.in/dxpcWx8 View in LinkedIn