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[IP] phenol

Insulin has been shown to be a protein consisting of two polypeptide
chains (see peptide), one of 21 amino acid residues and the other of 30,
joined by two disulfide bridges (see cysteine). The two chains are
synthesized in the beta cells as part of one continuous polypeptide chain
called proinsulin; a 32-amino acid sequence (the connecting peptide) is
subsequently split out of the proinsulin molecule by an enzyme resembling
trypsin to yield active insulin.

The thiol group of one cysteine residue is capable of combining with the
thiol group of another to form a disulfide bridge, either linking two
peptide chains together, as in the case of insulin, or causing a single
peptide chain to fold back on itself, making a loop.

phenol , C6H5OH, a colorless, crystalline solid that melts at about 410C,
boils at 1820C, and is soluble in ethanol and ether and somewhat soluble
in water. An aromatic alcohol, it exhibits weak acidic properties and is
corrosive and poisonous. Phenol is sometimes called carbolic acid,
especially when in water solution. It reacts with strong bases to form
salts called phenolates. Phenol is important in industry in the
production of certain artificial resins, e.g., Bakelite, and in the
synthesis of many drugs, dyes, weed killers, insecticides, and explosives
(e.g., picric acid). It is the simplest member of a class of hydroxy
benzene derivatives, all of which contain a hydroxyl group attached to a
benzene ring; these compounds may be thought of as derivatives of phenol
and generically are called phenols.


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