In the figure 1A of http://photobiology.info/Jones.html the Mg is not belong to other structure. Is that because something is omitted or is it indeed like a pearl in a mussel's mouth? In the later case could we replace the Mg by some other atoms (and the bacteriochlorophyll still live well)?

  • 2
    $\begingroup$ The Mg atom is not bound in the porphyrin ring, it is coordinated there. $\endgroup$
    – Chris
    Commented Jan 27, 2017 at 7:51
  • $\begingroup$ photobiology.info/Jones.html The author of the above page told me The magnesium (purple sphere) is bonded to the four pyrrole nitrogens (the four blue atoms pointing towards it. $\endgroup$
    – latra
    Commented Jan 28, 2017 at 22:01
  • $\begingroup$ I checked chemistry books "coordinate" means the shared electron all came from one party ? So,what is the difference between bounded and coordinated? $\endgroup$
    – latra
    Commented Jan 29, 2017 at 4:45
  • $\begingroup$ When the atom is bound, chemical bounds are formed. If it is coordinated, it is kept in place by interaction between the atoms (for example by van der Waals force). $\endgroup$
    – Chris
    Commented Jan 29, 2017 at 21:16
  • $\begingroup$ So, both Mg in chlorophyll and Fe in RC are coordinated? Will a coordinated atom have a fixed orientation with other atoms? $\endgroup$
    – latra
    Commented Jan 29, 2017 at 22:34


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