Month: September 2022

NEW REALITY DROVE NEW SOLUTIONS. "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

THE OXYGEN PROBLEM. "When chlorophyll-containing species found themselves in the presence of O2 then there was a big problem: the excited singlet and more importantly the longer-lived triplet state had more than enough energy (1.3 eV) to drive the conversion of triplet O2 to its highly reactive singlet form (1 eV). Redox tuning does not help here, this is an energy question and red light is as low in energy as possible for efficient oxygenic photosynthesis." https://lnkd.in/dxpcWx8 View in LinkedIn

MINIMIZING INEFFICIENCY. "The main fix was to wheel out the carotenoids as quenchers of chlorophyll triplet states and of singlet O2. 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

OXIDATION PROTECTION. "In PSII, given the extreme oxidising chemistry associated with water oxidation and generation of O2, there are other protective mechanisms that appear to be there to prevent over-oxidation of the cofactors and groups in their environment (These too may have secondary reactions associated with O2 and its derivatives." https://lnkd.in/dxpcWx8 View in LinkedIn

"SHORT CIRCUITS in the broken Q-cycle. Despite its sluggishness, the very existence of this short-circuit is important because it represents an “emergency exit” pathway which bypasses the Q-cycle. This reaction thus allows the quinol-plastocyanin oxidoreductase activity to occur and thus the entire photosynthetic chain to function, even with a non-functional Q cycle." https://lnkd.in/dxpcWx8 View in LinkedIn

RETOOLING COMPROMISES. "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

SO ENDS this case study of how the photosynthetic apparatus of plants had to adapt imperfectly to the emergence of an oxygenated atmosphere. Molecular vestiges suited for different purposes are littered through cellular systems. It is not just wisdom teeth, feet and the human tailbone: every aspect of life shows evidence of the wrench of sometimes clumsy adaptation to meet new challenges. View in LinkedIn

NO REGENERATION. "While urodele amphibians (newts and salamanders) can regenerate limbs as adults, other tetrapods (reptiles, birds and mammals) cannot and just undergo wound healing." http://onlinelibrary.wiley.com/doi/10.1111/j.1440-169X.2007.00973.x/full View in LinkedIn

BIRDS AND MAMMALS. "Birds cannot regenerate limbs at any stage of development and, surprisingly, mammals have slightly better limb regenerative capacity than that of birds." http://onlinelibrary.wiley.com/doi/10.1111/j.1440-169X.2007.00973.x/full View in LinkedIn

HIGH REGENERATION. "Sea urchins are highly regenerative animals with indeterminate growth and life-long reproduction, and thus offer the opportunity to investigate mechanisms for long-term maintenance of tissue homeostasis and regenerative capacity. In addition, different species of sea urchins have very different reported life expectancies" of up to 100 years.” https://lnkd.in/dQZUv9k View in LinkedIn