PORYPHRINS PRESENTATION .pdf

Porphyrins are organic pigments, of both natural and
synthetic origin, all of which contain the porphyrin ring
as part of their structure.
In addition, porphyrin chemistry deals with various
analogues and derivatives of porphyrins and,
particularly, with their metal complexes.

1. PORPHYRINS AND IT'S
CLASSIFICATION
BY
JYOTI REKHA PATRA

2. Porphyrin Definition:-
•A porphyrin is a large ringmoleculeconsisting of 4pyrroles, which are
smaller rings made from 4 carbons and 1 nitrogen. These pyrrole
molecules are connected together through a series of single and
double bonds which forms the molecule into a large ring.
•The technical name for 4 pyrroles connected together is
atetrapyrrole.
•The ring is flat in space, and the distribution of electrons is fairly
equal around the circumference of the ring.
•For this reason, a porphyrin is considered anaromaticcompound.
This means that a porphyrin molecule is very stable.The model of a
general porphyrin is calledporphin.
•This molecule is only rarely found in nature as anintermediate

3. The blue partsof the molecule represent the aromatic ring which forms the base of all
porphyrin molecules.
The black molecules and bonds will eventually be substituted for complex side chains.
These molecules will allow the cellular machinery to attach to and use the porphyrin.
Porphyrins are also capable of absorbing certain wavelengths of light, especially when
associated with different ions.Porphyrins cause both the red color ofbloodand the green
color of plants.
Porphyrin molecules serve a number of purposes in animals, plants, and evenbacteria. For
this reason porphyrin is considered anevolutionarily conservedmolecule.

4. •General characterization :-
•Porphyrins are a class of macrocyclic aromatic compounds composed of
four pyrrole rings connected by methine bridges. Porphyrins are ubiquitous
in nature, as a heme cofactor of hemoglobin, cytochromes, and other redox
active enzymes, and, as more saturated analogs, in the photosynthetic
apparatus in plants and bacteria.
•Tetrapyrrolic macrocycles have been widely examined for their unique
optical and redox properties.

5. •Porphyrins have a unique electronic structure that results in a
complex absorption spectrum.
•Simple porphyrins (such as tetraphenylporphyrin) exhibit a very
strong (with ɛ ∼500,000 M–1 cm–1) absorption band around 400
nm, a series of much weaker bands in the visible region (500–650
nm), and a very weak absorption band in red spectral window (∼650
nm).170 Porphyrins possess also moderate fluorescence quantum
yields (∼0.1).170
•Although simple porphyrins are not suitable for in vivo fluorescence
imaging because of their weak absorption in red/near-IR spectral
window

6. •The precursor pyrrole and
the parent porphin
nucleus of porphyrins.
Sites of isomeric
substitutions are given as
circled numbers and the
pyrrole rings as letters. A
schematic representation
is also given.

7. •Theclassificationoftheporphyrinsisbasedonthesyntheticporphyrin,etioporphyrin
(ETIO),inwhichtwodifferentradicalsaresubstitutedatpositions1through8.The
substitutedradicalsarefourmethyl(M)andfourethyl(E)groups.Thenumberof
structuralisomerspossiblewiththeseeightsubstitutedradicalsisfour,asshownatthe
topofFigure8-2.Thenaturallyoccurringporphyrinsareonlythoseinwhichthe
positioningoftheirsubstitutedradicalscorrespondtoisomerIorIIIofetioporphyrin,
ETIOIandETIOIII.ThisobservationledFischertospeakofa“dualism”ofporphyrinsin
nature,whichisinessentialagreementwithpresentknowledgeofthebiosynthesisof
theporphyrinisomersasproceedingalongparallelandindependentpaths.
•Theuroporphyrinsalsocontaintwodifferentradicals,acetic(A)andpropionic(P)acids,
andfoureachofthesearearrangedtocorrespondtoeitherisomerETIOIorETIOIII(Fig.
8-2).Inthiscase,AcorrespondstoMandPcorrespondstoE.Therefore,theseare
designateduroporphyrinI(UROI)oruroporphyrinIII(UROIII).Similarly,the
coproporphyrinscontainfourMandfourPgroupsandaredesignatedcoproporphyrinI
(COPROI)andcoproporphyrinIII(COPROIII).Theprotoporphyrinofheme(iron-
protoporphyrin,theprostheticgroupofhemoglobin)correspondstotheseriesIIIisomer.
Inthiscase,however,threedifferentradicalsinsteadoftwoaresubstituted.These
consistoffourM,twoP,andtwovinyl(V)radicals.Withthreedifferentradicals,15
isomersarepossible,buttheprotoporphyrinofhemeistheonlynaturallyoccurring
isomerknown.ThisisomerwasdesignatedprotoporphyrinIXbecauseitwastheninthin
theseriesofprotoporphyrinisomerssynthesizedbyFischer.Thearrangementofthe
methylgroupsofthisisomerasshowninFigure8-2correspondstothatofatypeIII
etioporphyrinisomerandmoreproperlyshouldbecalledprotoporphyrinIII.However,by
convention,thenameprotoporphyrinIX(PROTOIX)isthedesignationforthisporphyrin.

8. •The isomeric porphyrins.
The nomenclature of the
porphyrins URO, COPRO,
and PROTO is based on
the isomeric structure of
the etioporphyrins

9. •Synthesis of Porphyrins and Heme:-
•Theinitialstepsinthepathwayforporphyrinandhemebiosynthesisbegins
withtheincorporationofthemethylcarbon(C-2)andnitrogenatomof
glycineintotheporphyrinringandultimatelyintothehemeofhemoglobin.
•The methyl carbons (C-2) of glycine supply 8 of the 34 carbons of
protoporphyrin: one for each of the four methene bridges and one for each of
the pyrrole rings (Fig. 8-3). The carboxyl carbon atom of glycine is given off as
CO2and is not incorporated into the protoporphyrin molecule (Fig. 8-3). The
direct incorporation of the nitrogen or the methyl carbon glycine into the
heme of hemoglobin has been the basis for a useful technique to label the
erythrocyte and to measure its survival time. After administering15N-glycine,
the concentration of15N in heme rises rapidly, remains constant for a time,
and then falls.
•The remaining carbons of protoporphyrin are supplied by the tricarboxylic acid
(TCA) cycle intermediate

11. •Types of Porphyrins
•Porphyrins in Animals
•A major use of porphyrin molecules in animals is in the construction
ofhemegroups. These molecules are simply a porphyrin molecule with various
side-chains substituted around the main ring. In a heme, the porphyrin ring
serves an important function. The nitrogen molecules at the center of the ring
are capable of “hosting” an iron molecule. It is this porphyrin structure, holding
iron, which gives blood its red color.
•The red blood cells have the proteinhemoglobin, which holds the heme in
place.
•Another heme-holding molecule,myoglobin, functions as the oxygen
transporting molecule within themusclecells. This heme is also made from
porphyrin, and hosts iron. Myoglobin has different side-chains than
hemoglobin. As such, it can interact with the machinery of muscle cells, and
deliver oxygen from the surface of thecellto themitochondriawhich need the
oxygen ofoxidative phosphorylation.

12. •Porphyrins in Plants
•plants have also mastered a different configuration of porphyrin molecule,
which allows them to capture the energy in sunlight.Chlorophyllis a special
molecule designed around a porphyrin base. Seen below, the chlorophyll
molecule has several unique side-chains off of the porphyrin molecule. It also
has a really long side chain, seen coming off the bottom. These side-chains
slightly change the shape and configuration of the base porphyrin.

13. •Applications
•Photodynamic therapy
•Porphyrins have been evaluated in the context ofphotodynamic therapy(PDT)
since they strongly absorb light, which is then converted to energy and heat in
the illuminated areas.
[18]
This technique has been applied inmacular
degenerationusingverteporfin.
[19]
•Organic geochemistry
•The field oforganic geochemistryhad its origins in the isolation of porphyrins
from petroleum.This finding helped establish the biological origins of
petroleum. Petroleum is sometimes "fingerprinted" by analysis of trace
amounts of nickel andvanadylporphyrins.
•Toxicology
•Heme biosynthesis is used asbiomarkerin environmental toxicology studies.
While excess production of porphyrins
indicateorganochlorineexposure,leadinhibitsALA dehydrataseenzyme.
[22]

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