Search results
Results from the WOW.Com Content Network
The parent of porphyrins is porphine, a rare chemical compound of exclusively theoretical interest. Substituted porphines are called porphyrins. [1] With a total of 26 π-electrons, of which 18 π-electrons form a planar, continuous cycle, the porphyrin ring structure is often described as aromatic.
In biochemistry, a porphyrinogen is a member of a class of naturally occurring compounds with a tetrapyrrole core, a macrocycle of four pyrrole rings connected by four methylene bridges. [1] They can be viewed as derived from the parent compound hexahydroporphine by the substitution of various functional groups for hydrogen atoms in the ...
The porphyrin ring is a planar dianionic, tetradentate ligand. The iron is typically Fe 2+ or Fe 3+. One or two ligands are attached at the axial sites. The porphyrin ring has 4 nitrogen atoms that bind to the iron, leaving two other coordination positions of the iron available for bonding to the histidine of the protein and a divalent atom. [2]
The porphyrin with a core phosphorus (V) ion can be tuned with additional substituents added to either the outside of the polycyclic ring system or axially to the core phosphorus. Meso-substituted porphyrins like meso-tetra-p-tolylporphyrin (TTP) and octaethylporphyrin (OEP) are often used in synthesis of the core phosphorus porphyrin.
[4] Like heme B, heme A is often attached to the apoprotein through a coordinate bond between the heme iron and a conserved amino acid side-chain. In the important respiratory protein cytochrome c oxidase (CCO) this ligand 5 for the heme A at the oxygen reaction center is a histidyl group. [5]
In coordination chemistry, a macrocyclic ligand is a macrocyclic ring having at least nine atoms (including all hetero atoms) and three or more donor sites that serve as ligands. [1] Crown ethers and porphyrins are prominent examples. Macrocyclic ligands often exhibit high affinity for metal ions, the macrocyclic effect.
The general term protoporphyrin refers to porphine derivatives that have the outer hydrogen atoms in the four pyrrole rings replaced by other functional groups. The prefix proto often means 'first' in science nomenclature (such as carbon protoxide), hence Hans Fischer is thought to have coined the name protoporphyrin as the first class of porphyrins. [3]
Porphyrins, including heme, the core of hemoglobin; Chlorins, including those at the core of chlorophyll. Cyclic tetrapyrroles having three one-carbon bridges and one direct bond between the pyrroles include: Corrins, including the cores of cobalamins, when complexed with a cobalt ion.