Chemistry-biology interface: a historical perspective

Federico Cisnetti

ICCF/SEESIB

Formation

Initiation scientifique en Anglais

Outline

• 1. Contemporary view

• 2. Historical perspective of “organic” chemistry

• 3. Four Nobel prizes: evolution of chemistry applied to biology during the 20th century.

• Conclusion and outlook

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1. Contemporary view

• …

• Matter is constitued of atoms.

• Atoms form molecules

• Molecules interact to form complex structures

• These assemble themselves to form cells.

• Cells forms tissues.

• Organs are made from tissues

• …

Chemistry

Biology

Physics

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O,C,H,N: bulk elements K,P,Ca,S,Na,Cl: Macro-elements Oligo-elements All or most compounds toxic

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What we know today

Dose-effect curve Deficiency of essential metals is lethal … but these are toxic at high dose

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Chemical composition of the human body

Inorganic compounds: Ca5(PO4)3(OH) (hydroxyapatite): bones

Water H2O

Organic Matter

CHNOPS

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What we know today

~200.000 C-C bonds

Mass: 1 ng

5 1013 carbon atoms

1014 cells by human being

A cell is simultaneously:

Very large compared to molecules

Very small compared to the body

Typical Cell

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Nucleus

Mitochondria

What we know today

The place of chemistry in contemporary science

Chemistry: science studying matter, its structure and properties above the atomic level and its modifications in chemical reactions.

Contemporary chemistry relies on the principles of quantum physics (first half of the XXth century)

Biology: is a natural science concerned with the study of life and living organisms

Biochemistry: study of chemical processes in living beings.

Organic chemistry: chemistry based on the molecular compounds of carbon.

T. Balaban and Douglas J. Klein, Scientometrics, 2006 7

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Historical perspective of ‘organic’ chemistry

Chemists were interested in living matter: • before the rise of the modern concepts of atoms and molecules (XXth century) • before the understanding of what defines a chemical compound (XVIIIth-XIXth centuries) • before… chemistry if one considers alchemy as precursor of chemical practice. Key historical questions: • which substances are necessary for life? • could man-made substances be used in medicine? • is living matter obeying the same laws as mineral, inert substances?

The beginnings of « chemistry » applied to living beings: Alchemy

Antiquity middle ages renaissance Egypt, Greece Arab world Europe & rest of the world

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Antiquity • Origin: Alexandria, Egypt, intellectual centre of egypto-greco-roman civilisation (Great Library) • Technical recipes focused on manufactory of gold: alloys of golds superficial gilding. • Mercury was recognised as able to dissolve gold, and, simultaneously as a poison

Experimental setup by Zosimus 4th century CE

Most primary sources lost during the dark ages

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Alchemy

Arab alchemists → Arab translation of greek sources Jābir ibn Hayyān (721-815), Al-Razi (865-925)... Several important "pre-chemical" developments • Techniques: crystallisation, distillation. • Sophisticated laboratory apparatus : e.g. ovens • First intuition about the fact that definite quantities of each substance are needed for alchemic processes • Discovery of important substances: alcohol, acetic acid, nitric and sulfuric acids • Elixir to transmute a metal in another one.

athanor

The alchemist, Joseph Wright, 1771

Metals form deep inside Earth under the influence of celestial bodies. Corrosion of metals Illness Analogy between alchemy and medecine Gold is the most perfect metal. Purify a metal and transmute it into gold a cure for the sick patient Elixir, panacea: universal remedy

European Alchemists → latin translation of arab texts

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Paracelsus (1494-1541, Switzerland), focused on the concept of chemical pharmacopeia. He is considered as the founder of iatrochemistry (medical chemistry)

Correspondances Sun Gold Heart Moon Silver Brain Jupiter Tin Liver Venus Copper Kidneys ….

Attemps of therapies with metal-based preparations Dosis facit venenum. The dose makes the poisson Very modern idea!

From alchemy to chemistry

Jean-Baptiste Van Helmont (Flanders, 1627-1691) Precursor of pneumatic chemistry. Van Helmont applied the experimental method to verify alchemical assumptions Experiment that allowed Van Helmont to conclude that water is the primordial element

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Discovery of gases: biological properties

• Jean-Baptiste van Helmont discovered that "gas sylvestre" originated from the combustion of charcoal. Later on, he recognised that this gas was unbreathable and was the same that originated from fermentation. • Joseph Priestley isolated pure oxygen in 1774 but did not recognise it as an element. Instead he believed that his sample contained "dephlogisticated air". He noticed that "five or six times better than common air for the purpose of respiration, inflammation, and, I believe, every other use of common atmospherical air “. •Lavoisier discovered that air was consituted of two gases "vital air " (later renamed to oxygen) and azote (greek etymology: lifeless). It was recognised that « vital air » allowed both combustion and respiration. The parallel between combustion (or corrosion) and respiration was understood since the very first modern chemical experiments.

Beginnings of ‘organic’ chemistry

Nicolas Lémery (France, XVIIth century) suggested the extension to chemistry of the division of the world into vegetal, animal and mineral. Organic chemistry was founded as the chemistry of organised substances (vegetal and animal) 1780-1820: foundation of modern chemistry (Lavoisier) Chemical analysis of living matter. Decomposition in species that chemists could analyse and quantify.

Justus Liebig (Germany, 1803-1873) used CuO to analyse organic matter. Elemental analysis chemical formula

Liebig’s laboratory in Giessen

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Composition of (living) matter

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“If two elements form more than one compound between them, then the ratios of the masses of the second element which combine with a fixed mass of the first element will be ratios of small whole numbers”

John Dalton, the first modern atomist

Today, chemistry is based on the descption of matter as molecules as assemblies of atoms. John Dalton introduced the first modern atomic theory. He established the law of multiple proportions ("New System of Chemical Philosophy“, 1808)

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Hot debate between atomists and anti-atomists (equivalentists) throughout the XIXth century

Vital force theory (vis vitalis)

Jöns Jacob Berzelius (Sweden, first half of the XIXth century ): Study of mineral compounds, discovery of several elements. Chemists cannot prepare by synthesis compounds found in living beings Need of a « vital spark » (transcendent/religious explanation) Chemists could decompose or modify an organic sample but not reconstitute it.

First counter-evidence: Friedrich Wöhler (1828)

Pb(CNO)2 + 2NH3 + 2 H2O → Pb(OH)2 + 2NH4(CNO)

The vitalist theory, was not completely overturned…

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The action of living beings on chemical compounds revived the vitalist theory

i.e. in modern terms: enantiopure compounds are accessible only from living sources The vitalist theory was definitively overturned by the proof

enzymes (ferments) as isolated chemical compounds could allow chemical transformations. Although the vitalist theory is obsolete, « organic chemistry » remains.

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Four Nobel Prizes: 1907-1964

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The history of the Nobel Prize in chemistry throughout the XXth century allows to understand the greatest achievements of this science and the topics that attracted and continue to attract the attention of scientists. More than 30 of the Nobel Prizes in chemistry awarded (each year between1901-2013 with very few exceptions) correspond to topics belonging chemistry-biology interface

Eduard Buchner (Germany) 1907

Norman Haworth (USA) 1937

Vincent du Vigneaud (USA) 1955

Dorothy Hodgkin(UK) 1964

Eduard Buchner

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1907 for his biochemical researches and his discovery of cell-free fermentation “The work on which I have to report lies on the boundary between animate and inanimate nature. I therefore have reason to hope that I can interest not only the chemists but also the wide circles of all those who follow the advance of biological science with close attention.”

Microscopic Image of yeast

• 1680: microscopic observation of yeast. (van Leeuwenhoek). Not recognised as a living organism •Last part of XIXth century: biologists established « yeast as live cells of a plants » Fermentation as a result of life Mixed receptions among chemists: Some of them were vitalists, others opposed the theory

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Before Eduard Buchner Jöns Jacob Berzelius (1779-1848) assumed that yeast caused the decomposition of sugar catalytically, simply by its presence as a contact substance or catalyst. Justus Liebig (1803-1873) opinion was that yeast caused fermentation "in consequence of a progressive disintegration which it suffers in the presence of air in contact with water” Louis Pasteur (1822-1895), finally recognised that in Nature without living organisms, no fermentation exists. Moritz Traube (1826-1894), assumed that there was in micro-organisms a certain chemical body which caused fermentation. How to study fermentation chemically?

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1000 g yeast + hard, fine-divided (quartz, etc) 500 g liquid extract

Carbon dioxide bubbles and formation of ethanol if added to a solution of sugar. fermentation

Eduard Buchner

First experimental setup, then sophisticated hydraulic presses.

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Norman Haworth

1937 for his investigations on carbohydrates and vitamin C

Haworth introduced the representation that bears his name nowadays. Simple sugars had already been explored decades before by Emil Fischer (Nobel Prize 1902)

“Twenty years ago it could have been said that the wealth of natural products which comprise the carbohydrate group was bewildering in its complexity. Such materials as cellulose, glycogen, and starch seemed almost beyond the range of structural investigation” (N. Haworth Nobel lecture) Haworth and others established the structures of natural carbohydrate polymers by chemical means. These works contributed greatly to the understanding of the general properties of life’s macromolecules.

Haworth’s legacy: carbohydrate polymers

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Example : D-glucose polymers (glu)n

• Starch (plants, energy storage) • Glycogen (animals, energy storage) • Cellulose (plants, structure)

Potato amyloplasts with starch colored by iodine

Monosaccharides = carbohydrates

(CH2O)n where n ≤ 7(most often)

Disaccharides: 2 monosaccharides.

Oligosaccharides > 3 monosaccharides.

Giant polysaccharides: up to several thousand units

Structure of starch

1) Amylose

2) Amylopectin

Linear, water-soluble polymer (14) bond

Ramified polymer, 1 ramification each 24-30 glu units Sparingly soluble in water

Ramification : (16) bond

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= linear glu chains with (14) bonds (instead of (14) in starch)

Forms fiber in plants wood, cotton, paper.

Animals cannot break (14) bonds

Structure of cellulose

Overall: glucids as pioneered by Haworth illustrate that function is aquired by polymerization, 3D structure and interactions with other molecules

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Haworth’s legacy: synthesis of vitamin C

Haworth correctly determined, by chemical means, the structure of vitamin C (ascorbic acid) Acidic compound without carboxylic group, strong reductant, derived from sugars. Tadeusz Reichstein (1933) developed this process for synthesis of vitamin C

ascorbic acid

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Vincent du Vigneaud

1955 "for his work on biochemically important sulphur compounds, especially for the first synthesis of a polypeptide hormone“

1902

Theodor Curtius

Emil Fischer H2N COOEt

HN

NHO

O

H2N

HN

O

COOH

Diketopiperazin

O NH-peptide

O

H2N-peptideCH3

CO2H2, [Pd]

Max Bergmann, Leonidas Zerwas, 1932

Introduction of protective groups

Peptides have been investigated since the beginning of the XXth century

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Vincent du Vigneaud

J. Am. Chem. Soc. 1954

Synthetic oxytocin did possess the same physical and chemical characteristics than natural peptides and displayed its activity Very important hormone in human behaviour

Disulphide bridge

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After du Vigneaud’s works…

The synthesis of peptides is now mostly performed using solid phase chemistry. This technique relies on sophisticated protection/deprotection schemes.

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Dorothy Hodgkin

“…. [The] great advantage of X-ray analysis as a method of chemical structure analysis is its power to show some totally unexpected and surprising structure with, at the same time, complete certainty...“ (D. Hodgkin Nobel lecture)

1964 "for her determinations by X-ray techniques of the structures of important biochemical substances “

Contemporary apparatus

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Penicillin: demonstration of the structure contrary to scientific opinion at the time

Cholesterol: steroid Pepsin

Dorothy Hodgkin

Vitamin B12

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Conclusion and outlook

• The chemistry/biology interface has always been actively considered by chemists • Contemporary research:

- Macromolecular structure is accessible by physico-chemical techniques necessary for understanding the mechanism of action of drugs - Biological polymers may be synthesized chemically but macromolecular synthesis remains a challenge - Macromolecules such as enzymes may be used in new chemical processes ‘greener’ chemistry? - The molecular complexity of life is now understood it is still a challenge to apply analytical methods to detect a species of interest in a living system.

Thank you for your attention!