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I had the impression that PSII (photosystem II) always has four Manganese atoms (4 Mn). Is there any reason that these atoms are needed?

Is Mn or Fe also present in bacteria LH1 or LH2?

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  • $\begingroup$ I'm having some difficulty understanding your question... can you write everything out and not use abbreviations? This will help. Thanks! $\endgroup$ Commented Jan 16, 2017 at 3:06
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    $\begingroup$ Mn Fe are standard chemical symbols while PS2 is also standard abbreviation. Please stop these politics. Thanks. $\endgroup$
    – latra
    Commented Jan 16, 2017 at 4:06
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    $\begingroup$ I made some edits to your title because the previous isn't in the correct english syntax $\endgroup$ Commented Jan 16, 2017 at 4:09
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    $\begingroup$ I guess you are referring to Magnesium and not Manganese. Are you sure you are talking about manganese? $\endgroup$
    – WYSIWYG
    Commented Jan 16, 2017 at 12:06
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    $\begingroup$ Thanks. I am not a native speaker. Therefore, my English surely have some problem. But manganese....I guess was copied from a paper....But what is really there? $\endgroup$
    – latra
    Commented Jan 17, 2017 at 11:12

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Manganese is part of the oxygen-evolving complex and is essentiell for the oxidation of the water to generate electrons, protons and oxygen. This is done by changing the oxidation state of the mangane from +2 to +4, as shown in the figure (from here):

enter image description here

These manganese atoms are the center of the reaction - important here are the different oxidation states they can take, other examples are copper (in tyrosinase for example) or iron (hemoglobin) which are also present in the active center of enzymes. For more information see references 1 and 2.

Anoxygenic bacterial photosynthesis also needs metal ions in the bacteriochlorophyll, this is magnesium (as in the chlorophyll of green plants), the light harvesting complexes contain iron-sulphur complexes. For a general overview see reference 3, for more detail on the reaction centers and their evolution, see reference 4.

References:

  1. Where water is oxidized to dioxygen: structure of the photosynthetic Mn4Ca cluster.
  2. Reduction-induced inhibition and Mn(II) release from the photosystem II oxygen-evolving complex by hydroquinone or NH2OH are consistent with a Mn(III)/Mn(III)/Mn(IV)/Mn(IV) oxidation state for the dark-adapted enzyme.
  3. Bacterial Photosynthesis
  4. Reaction centres: the structure and evolution of biological solar power.
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  • $\begingroup$ There seems to have some LH1 or LH2 do not need such atoms. I am not sure whether PS I or PS II... $\endgroup$
    – latra
    Commented Jan 17, 2017 at 11:28
  • $\begingroup$ any physical reason why these atoms must be there? (for instance they need a spin or entropy...) $\endgroup$
    – latra
    Commented Jan 19, 2017 at 0:49
  • $\begingroup$ @latra Besides having the function as electron acceptors/donors? Not that I know of. $\endgroup$
    – Chris
    Commented Jan 19, 2017 at 7:20
  • $\begingroup$ So, it is biochemistry instead of biophysics. The picture above came from a biophysics course note. $\endgroup$
    – latra
    Commented Jan 19, 2017 at 9:50
  • $\begingroup$ @latra If you want to see the real flow of the electrons on the molecular level, this is mixed biochemistry-biophysics. $\endgroup$
    – Chris
    Commented Jan 19, 2017 at 10:10

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