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8/3/2019 Por Fir in As

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Porphyrins

Super-molecules of the Future and

the Sinister Molecules of the Past

Paul GoodlandKim Fields

Peter Zhang

University of South Florida


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What do all these things have incommon? This.


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And.


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AND.


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AND.


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And


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and


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And.


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and


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And even..


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They all involve a class ofchemical compounds known as

porphyrins


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History of Porphyrins

The pathway toporphyrins beginswith dyes extracted

from plants such asthe indigo plant. Theywere so brilliantlycolored and colorfast

that they quicklybecame a luxury.Royal Purple


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Porphyrins were discovered byaccident!

In 1897, a new German company (BASF) beganmanufacturing synthetic indigo dye, which wascheaper and easier than the extraction process.

Another company, ICI, trying to make a modifiedindigo, kept getting a purple by-product thatcontaminated their desired product.

These impurities were also brilliantly colored

dyes, which could withstand temperatures up to500C! Most other dyes would fade or turn colorsat high temperatures.


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Voila! le Porphyrin

N

NH N

HN


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Why Porphyrins are Cool

Theyre really big.

They can contain many different metalatoms in their centers.

The are very stable due to theirconjugation (alternating single and doublebonds).

They can take on an amazing variety ofroles in the real world, which is why theyare widely utilized and researched


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Uses of Porphyrins

Because of the unique chemistry of porphyrins,they are able to serve in several ways: As a metal binder (ligands)

As a solar cell (convert light or chemical energy)

As an oxygen transport medium (hemoglobin)

As an electron transfer medium (conductingpolymers)

Gene regulation

Drug metabolism

Iron metabolism

Hormone synthesis


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As the basic building block of hemoglobin,and as a hemoglobin modeling molecule

Heme a cross-coupled porphyrinused in the largermolecule hemoglobin


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Chlorophyll yes, porphyrins areimportant in plants, too!

Chlorophyll as aPhotoreceptor

Chlorophyll is the molecule thattraps this 'most elusive of all

powers' - and is called aphotoreceptor. It is found in thechloroplasts of green plants, andis what makes green plants,green. The basic structure of achlorophyll molecule is aporphyrin ring, coordinated to a

central atom. This is very similarin structure to the heme groupfound in hemoglobin, except thatin heme the central atom is iron,whereas in chlorophyll it ismagnesium.

http://departments.colgate.edu/chemistry/images/geier-fig1.gif
http://www.chm.bris.ac.uk/motm/chlorophyll/porphine.molhttp://www.chm.bris.ac.uk/motm/chlorophyll/chlorophyll.pdbhttp://www.chm.bris.ac.uk/motm/chlorophyll/chlorophyll.pdbhttp://www.chm.bris.ac.uk/motm/chlorophyll/porphine.mol


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Cytochrome C a molecule responsible for transporting an electron used toprovide energy to the organism.

These molecules are identical, or very similar, for related species of plants or

animals. For example, chickens and pigs have identical cytochrome C, andducks differ onl b a few atoms.


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As water-splitting molecule in fuel cellsthey produce hydrogen gas from water

The continuous system, during the daytime porphyrin-basedphotovoltaics are used directly for power needs. Some of thefuel cells are also run backwards for water splitting, which isthen stored chemically as hydrogen and oxygen. Chemicalstorage is a more viable option compared to batteries in terms ofefficiency and weight. The stored hydrogen and oxygen is fedinto the fuel cells at night for continued use.


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Photodynamic Therapy

Porphyrins arecommonly used aslight-absorbing

compounds which areswitched on by

photons of light andthen react with cells in

a desired way.


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Photodynamic Therapy

Photodynamic therapy (PDT) -fiberoptic surgery

A photosensitive drug absorbed bycancer cells can be activated by alaser beam guided through optical

fibers to selectively destroy atumor.These drugs are also used to treat

other conditions, such as acne.

John CrawfordNational Cancer Institute

"photodynamic therapy." Online Photograph. BritannicaStudent Encyclopedia.9 July 2008 .
http://student.britannica.com/eb/art-92509http://student.britannica.com/eb/art-92509http://student.britannica.com/eb/art-92509http://student.britannica.com/eb/art-92509http://student.britannica.com/eb/art-92509http://student.britannica.com/eb/art-92509


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As an anticancer agent inphotodynamic therapy

Cancer type Gross incidence paSuitable for

PDT

Head and neck (oral cavity, larynx,pharynx and oesophagus 150,000 w/w based upon a US incidence of 17.7 per 100,000

Estimated 10% =15,000

Lung cancer 500,000 w/w based upon a US incidence of approximately 170,000Estimated 10% =

50,0000

Bladder 150,000 based upon a US incidence of 53,000 5% = 7,500

GastricSecond most common cancer in Far East 120,000 pa in Japan. Less

common in West but w/w incidence must exceed 300,000 paEstimated 10% =

30,000

Cervical 40,000 based upon a US incidence of around 13,000Estimated 10% =

4000

Non melanoma skin 500,000 Estimated 80,000

Barrett's oesophagus(pre-cancerous) 1 million US 5% =50,000

Total potential patients = 164,500 patients

Table: potential PDT cancer market

Sources: PDT Inc, SEER Cancer stats and various others. Estimates by First Instar other percentages PDT


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As chemical markers in oilexploration - Petroporphyrins

The presence of metalloporphyrins in organic-rich sediments such oil shales andpetroleum, generally known as petroporphyrins or geoporphyrins, was firstestablished in the 1930's.

Deoxophylloerythroetioporphyrin (DPEP) and etioporphyrin-III, which usually occur asthe nickel(II) or vanadyl chelates, are commonly found in oil and oil shale.

DPEP is considered to be a molecular fossil of the chlorophylls due to the presenceof a five-membered exocyclic ring

In the 1960's, mass spectrometric investigations demonstrated that sedimentaryporphyrin fractions contain complex mixtures of metalloporphyrins. Indeed, more than eighty porphyrin structures have been identified in organic-rich

sediments by mass spectrometry and NMR spectroscopy. These geoporphyrins fall into several major families, the most prevalent being the

DPEP series which are structurally related to chlorophyll. The structures of the porphyrins in fossil fuels can provide insights into the origins of

these materials and their sedimentary history, as well as being useful chemicalmarkers for petroleum exploration. In addition, the porphyrins associated with a given sediment provide a unique

fingerprint and may allow the origins of environmental contaminants (e.g. oil spills) tobe ascertained.
http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6THS-49DDJSY-8&_user=2139826&_rdoc=1&_fmt=&_orig=search&_sort=d&view=c&_acct=C000054278&_version=1&_urlVersion=0&_userid=2139826&md5=8670eb020cf1bee9ad0d2927a3a6b418http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6THS-49DDJSY-8&_user=2139826&_rdoc=1&_fmt=&_orig=search&_sort=d&view=c&_acct=C000054278&_version=1&_urlVersion=0&_userid=2139826&md5=8670eb020cf1bee9ad0d2927a3a6b418


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In Conducting Polymers

Photovoltaic coatings that gather light andemit electricity could be used to poweryour house or your vehicle. If your vehicle

was painted with a photovoltaic coating itcould gather sun light and emit theelectricity needed to power itself. Thiswould be environmentally friendly and in

most cases cheaper than petroleumproducts. History & Coating Applications of Conductive Polymers Report for Chemistry 446, Spring

2002 by Jason Shaw & Derek Marin
http://chemweb.calpoly.edu/chem/gragson/Teaching/chem446/Chem446.htmhttp://chemweb.calpoly.edu/chem/gragson/Teaching/chem446/Chem446.htm


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Polymeric Photovoltaics

A house that generates it'sown electricity and clothingthat can power a lap topcomputer will soon become areality. One may ask how thisis possible? The answer ispolymeric photovoltaics.

While photovoltaic clothingproducts are almost here thephotovoltaic structural coatingsare still a ways off. Things aredeveloping quickly in the field.All that remains is to make the

coatings more efficient andcheaper to manufacture. One major area of research is

photovoltaic pigmentstoaugment coatings. A popularchoice are the porphyrins,which are chemically similar tochlorophyll.


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Porphyria

Multiple enzymes are needed for the body to produce heme. If any one of the enzymes is abnormal, the process cannot

continue and the intermediate products, porphyrin or itsprecursors, may build up and be excreted in the urine andstool.

As a result of feedback, the decreased production of hemeleads to increased production of precursors, PBG, being one ofthe first substances in the porphyrin synthesis pathway.

The hepatic porphyrias primarily affect the nervous system,resulting in.

What made King Geoge III so very mad? The British ruler who presided overthe loss of the American colonies in 1776 was diagnosed about two centuries

too late with porphyria a genetic disorder that causes psychiatricdisturbances, among other things.

Abdominalpain

vomiting acuteneuropathy

seizures hallucinations depression

anxiety cardiacarrhythmias

fast heart rate(tachycardia)

Chronic andacute pain

paranoia Constipationand/or

diarrhea


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The Truth about Vampires?

Photosensitivity? Crazy behavior? Paleskin? Anemic? Involuntary tranfusions?

Stories of vampires date back thousandsof years. Our modern concept stemsfrom Bram Stoker's quirky classicDracula and Hollywood's Bela Lugosi--the romantic, sexually charged, blood-sucking outcast with a fatal susceptibilityto sunlight and an abhorrence of garlicand crosses.

In contrast, vampires of folklore cut apathetic figure and were also known asthe undead.

In searching for some underlying truth invampire stories, researchers have

speculated that the tales may have beeninspired by real people who suffered fromporphyria.

Did they seek the blood of othersbecause they were unable tomanufacture their own? Hmmmm..


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Werewolf?

http://www.geocities.com/RainForest/Canopy/5322/molybdenum.html


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As a selective catalyst

Porphyrins, especiallythose with special groupsknown as chiral centersas part of the structure,

have a special ability tohelp chemical reactionsto proceed to veryspecific products.

Chiral centers are

carbons atoms with fourdifferent groups attachedto it.


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A Quick Organic Chemistry Lesson

Organic chemistry the chemistry ofcarbon-containing compounds

Shortcut formula draw lines instead ofcarbon-carbon bonds.

R a letter used to represent a variety ofcarbon-chains from one carbon to many.


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Synthesis of Porphyrins Simplified

N

NH N

NHNH

pyrrole4 parts

+

R

O

1 great big porphyrinaldehyde

4 parts

R

R

R

R

each corner represents a carbon atom

(R is hydrogen or a carbon chain of any length)


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The Porphyrin Synthesis Process

Reaction: Pyrrole and aldehyde

Separate product (porphyrin) from leftoverreactants and by-products

Purify (by chromatography) and removewater and/or other impurities

Wash and filter as needed to isolateproduct


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Porphyrin Research

What is there to research?Arent they all pretty muchthe same?

Well, no. There are lots of

variations. There is thebase model

And then there are lots ofsubstitutedporphyrins.

So you can change thegroups attached to it, andwhen you do, it gets newcharacteristics.

N

NHN

HN


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Porphyrin Variation 1 the Center

The center of the porphyrin can be empty (left) or hold a metal ion(right). This is called coordination. The porphyrin on the left isempty, while the one on the right contains a cobalt atom.

N

NH N

HN

N

N N

N

Co


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Porphyrin Variation 2The Meso Positions

Different functional groups (R) can be attached to oneor more sides. Imagine all the different combinations ofmany possible functional groups mixed and matched atthese four locations

N

NH N

HN

*

*

*

*

meso positions*

N

NH N

HN

meso-substituted porphyrin

Cl

Cl


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Porphyrin Variation 2The Beta Positions

N

NH N

HN

beta positions (asterisks*)

*

* *

*

***

*

N

NH N

HN

beta-substituted porphyrin

Br Br

Br

BrBr

Br

Br

Br

The beta positions are the corner positions.


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Porphyrin Variation 3

Combinations of thesecombinations!Coordinated Metalsand/orMeso-substituents

and/oralpha-substituentsand/orbeta-substituents

Heme B


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Chemical Research Is.

Discover new compounds and their properties

Discover how the new compounds function

Publish findings worldwide so others doing similar

work can learn from it, question it, collaborate, etc. Research sometimes leads to recognition,

advancement, and other perks. But even when itdoesnt, it always adds to the collective body of

knowledge, some of which may be valuable later.

For example, (late discovery example)


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USF Leadership in Porphyrin Research

Synthesis of new porphyrin catalystsintroducing new groups to the porphyrinperiphery

Use of synthesized novel porphyrincatalysts in various highly-specificsynthesis reactions


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What Does it Take to Be aResearch Chemist

Graduate high school take as much science asyou can, especially AP courses

Get a bachelors (4-year) degree in a major suchas chemistry, chemical engineering, biology, or

anything else with a good chemistry foundation Apply to Grad school they usually will pay you

to go! (dont get excited though, its not a lot) Pick a program and do teaching, research, and

probably a few other duties Defend your doctoral thesis and they make youa doctor!


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Benefits - PhD Degree in Chemistry

You will in your lifetime earn about significantlymore than the masters and bachelors degreed

people alongside you.

You will most likely be a specialist or manager orother similar lofty position

You likely will get to travel but not too much

You will live to an old age.. (really)

Your job will be interesting and ever-changing


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Thank You!

Any questions?


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Acknowledgements

REST Program, Florida Department of Education

USF Department of Chemistry

School District of Hillsborough County

NSF CAREER Award (CHE-0711024)

Documents

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