From groundbreaking research into insulin to modern laboratory techniques, we explore how Cambridge helped transform the understanding and production of peptides.
Today, a researcher can order a peptide with a specified sequence and have it made, purified and tested to order.
Laboratories working with lab peptides take this for granted. Yet, in the early 1950s, the complete amino acid sequence of a protein had never been determined.
The story begins in a Cambridge laboratory, where pioneering work on insulin would change our understanding of protein chemistry.
Insulin before Sanger
Insulin was discovered in Toronto in 1921, but its precise chemical structure remained unknown.
Scientists knew that proteins contained amino acids. However, whether these followed a fixed sequence had not yet been demonstrated for an entire protein.
Insulin was a good candidate for investigation because it is relatively small.
It contains just 51 amino acids, arranged in two chains of 21 and 30, placing it on the border between a peptide and a protein.
Sanger’s method
Frederick Sanger joined Charles Chibnall’s group in the Department of Biochemistry at Cambridge in 1943, where he began investigating bovine insulin.
His approach was painstaking. He labelled the free amino end of each chain with a chemical now known as Sanger’s reagent. He then broke the insulin into fragments using acid or enzymes such as trypsin.
The fragments were separated on filter paper, first by electrophoresis and then by chromatography. Some were made visible using a dye called ninhydrin, producing a pattern of spots that Sanger called a fingerprint.
By identifying each fragment and matching the overlaps, Sanger gradually pieced the entire sequence together.
The B chain was completed in 1951, followed by the A chain in 1953. By 1955, the positions of the three disulphide bonds holding the structure together were also known.
Insulin became the first protein to be fully sequenced. In 1958, Sanger received the Nobel Prize in Chemistry for his work on the structure of proteins, particularly insulin.
His research demonstrated that proteins possess defined amino acid sequences. This discovery later aligned with Francis Crick’s sequence hypothesis about how genetic information is expressed in proteins.
Sanger went on to receive a second Nobel Prize in 1980 for his contributions to methods for determining nucleotide sequences in DNA.
From reading peptides to making them
While Sanger was working to understand insulin’s structure, other scientists were developing methods to synthesise peptides.
In 1953, Vincent du Vigneaud synthesised oxytocin, a hormone containing just nine amino acids. It became the first polypeptide hormone to be produced in a laboratory.
He received the Nobel Prize in Chemistry in 1955 for his work, particularly this achievement.
Insulin synthesis advanced during the 1960s, with Panayotis Katsoyannis in Pittsburgh and Helmut Zahn in Aachen reporting early synthetic insulin preparations.
In 1965, a Chinese research team produced fully synthetic, crystalline bovine insulin with biological activity.
Another major turning point came in 1963, when Bruce Merrifield published solid-phase peptide synthesis.
Rather than building a peptide in solution and purifying it after every step, this method anchors the chain to tiny resin beads. Amino acids are then added one at a time, using temporary protecting groups to control which chemical groups can react.
Excess reagents are simply washed away between steps.
The method earned Merrifield the Nobel Prize in Chemistry in 1984 and remains one of the principal techniques used to produce synthetic peptides.
Peptides in the modern laboratory
Peptide research has since expanded far beyond the structure of a single hormone.
Modern laboratories study peptides in areas including ageing and longevity, tissue repair and recovery, and metabolism.
Using cell cultures and animal models, researchers investigate how peptides interact with biological systems, influence cellular signalling and participate in processes involved in stress responses and tissue repair.
However, some of this research remains at an early stage. Findings from laboratory studies do not, by themselves, establish how a compound will behave in humans.
The same principles continue to underpin modern laboratory processes, although today’s tools are considerably more advanced.
Following synthesis, the crude product is commonly purified using reversed-phase high-performance liquid chromatography. Mass spectrometry then helps determine whether its measured molecular mass matches the expected value.
Additional analysis may also be required to establish its precise identity.
Science of peptidesAutomation has transformed the pace of production, too.
Continuous-flow approaches to peptide synthesis were being reported by the 1980s. Further developments from the early 2010s enabled faster and more automated production.
Peptides supplied for laboratory research are designated for research use only. Analytical checks following synthesis help researchers assess the identity and purity of the materials they are working with.
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