Protein Puzzle

One way scientists hope to learn more about the mysteries of the human body is by analyzing the structure of proteins, of which the vital parts of all living creatures are made. The job is complicated by the fact that the typical protein molecule is built up of hundreds or thousands of amino-acid-units which link together in complex ways. They form long chains, they branch, they tangle, they join together in rings. Even to identify the amino acids in a simple protein is a difficult task for the most skillful chemist. To figure how they are arranged in the protein molecule has baffled chemists completely. At last week's Second International Biochemistry Congress in Paris, Dr. Fred Sanger, 33, a Quaker chemist from Britain's Cambridge University, told how he and a group of associates had solved one protein puzzle.

Chemist Sanger worked with crystalline insulin, a comparatively simple protein. First he broke the large molecules by oxidation into two fragments, one containing 21 amino-acid building blocks, the other 30. Then by other methods (e.g., hydrolysis), he broke the two parts down until he had fragments that contained only a few amino acids each. These were compounds familiar to biochemists. Sanger identified them by paper chromatography,/- and the first and easiest part of his job was done.

Finding out how the pieces fitted back together was much harder. Sometimes Sanger and his group would find in their analysis some substance that does not appear in the known chemistry of living things. This, they decided, must be a taillike fragment knocked off some larger fragment. They would shift it around, like a piece in a jigsaw puzzle, until they found a spot where it could be placed to form a familiar compound. Little by little, their picture of the insulin molecule took on detail. At last they were sure they knew where each building block belonged.

Dr. Sanger points out that he has not synthesized insulin; he has only charted its structure. The importance of this work is that other chemists may now chart other proteins, find out whether certain groupings of amino acids in their molecules confer certain vital properties. Eventually, for instance, they may find that a small knot of amino acids makes a protein drug, like insulin, act as it does in the human body. Then perhaps a superior insulin substitute can be synthesized.

*Compounds containing an amino (NH2) group and a carboxyl (COOH) group. /-An analytical method which separates and identifies similar substances by the rate at which they creep through treated filter paper.

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