PRESENTED BY:SABARNI SARKER
HISTORY OF PROTEIN DISCOVERY
• The similarity between the cooking of egg whites and the curdling of milk was recognized even in ancient times; for example, the name albumen for the egg-white protein was coined by Pliny the Elder (a scholar from ancient Rome) from the Latin albus ovi (egg white).
Pre-history of Protein
Ancient people new much about the similarity of egg white and curdled milk
• There had been the concept of an "animal substance," slight variants of which were thought to make up muscles, skin, and blood.
• But it turned into hard, hornlike material when heated and became foul-smelling when kept under moist, warm conditions, giving off an alkaline vapor.
• This contrasted with the properties of starch and sugar.
• In 1728, the Italian scholar Jacopo Beccari announced that he had discovered the presence of a material with all the characteristics of "animal substance" in white wheat flour.
Pre-history of Protein
• Proteins were recognized as a distinct class of biological molecules by Antoine Fourcroy at 1789
• Members of this class were called albuminoids• Well-known examples at the start of the
nineteenth century included albumen from egg whites, blood serum albumin, fibrin, and wheat gluten
Protein: A Distinct Class
• Dutch chemist Gerhardus Johannes Mulder carried out elemental analyses of common animal and plant proteins in 1837
• To everyone's surprise, all proteins had nearly the same empirical formula, roughly C400H620N100O120 with individual sulfur and phosphorus atoms.
• He hypothesized that there was one basic substance (Grundstoff) of proteins, and that it was synthesized by plants and absorbed from them by animals in digestion.
PROTEIN: THE GRUNDSTOFF
Nomenclature of the protein
• Berzelius supported the theory of Mudler.• He proposed the name "protein" for this
substance in a letter dated 10 July 1838.• He said: The name protein that I propose for
the organic oxide of fibrin and albumin, I wanted to derive from the Greek word πρωτειος (first; foremost), because it appears to be the primitive or principal substance of animal nutrition.
Gerardus Johannes Mulder(1802-1880)
Jöns Jacob Berzelius(1779-1848)
Protein Timeline• 1819: Leucine is the first amino acid isolated. The 20th,
threonine, was not discovered until 1936. • 1902: Emil Fisher and Franz Hofmeister (independently)
discover the peptide bond.• 1907-8: Committees in England and the USA standardise
the term protein.• 1920: Hermann Staudinger was the first effective
proponent of the idea that true molecules of huge size are capable of stable existence.
• 1925: N. Bjerrum, E. Q. Adams, K. Linderstrøm-Lang and others reach consensus about the zwitterionic character of proteins at the isoelectric pH.
Protein Timeline (Continued)• 1929, Hsien Wu hypothesized that denaturation was
protein unfolding, a purely conformational change that resulted in the exposure of amino acid side chains to the solvent.
• 1930-1950, The hypothesis of protein folding was followed by research into the physical interactions that stabilize folded protein structures.
• The secondary and low-resolution tertiary structure of globular proteins was investigated initially by hydrodynamic methods. After 1950, Spectroscopic methods to probe protein structure were developed.
And Finally!• The first atomic-resolution structures of proteins
were solved by X-ray crystallography in the 1960s and by NMR in the 1980s.
• As of 2006, the Protein Data Bank has nearly 40,000 atomic-resolution structures of proteins.
• In more recent times, cryo-electron microscopy of large macromolecular assemblies and computational protein structure prediction of small protein domains are two methods approaching atomic resolution.
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