Red Giants

Since no chemist can truly say that he has seen a molecule under the microscope, laymen may be mystified to hear scientific talk of "giant molecules." But molecules, infinitesimally tiny as they are by ordinary standards, vary greatly in size. Molecular weight of ethyl alcohol, for example, is 46 units; * of sodium chloride (salt), 58.5; of the hormone secretin, 5,000; of hemoglobin, about 68,000; of the thyroid substance thyroglobulin, about 700,000. Dr. Wendell Meredith Stanley and his associates at the Rockefeller Institute have crystallized the virus which causes mosaic disease in tobacco, found that it weighs 17,000,000 units (TIME, Nov.15). A rabbit wart virus was found to weigh 20,000,000 units, a horse encephalitis virus 25,000,000. Even these monster molecules are so small that they pass through the pores of a fine filter.

At a chemical symposium in Manhattan last week Dr. Kurt G. Stern of Yale announced that he had isolated a red pigment molecule from liver tissue which weighs 3,000,000 to 4,000,000 units. This is the biggest molecule ever found to be a normal part of vertebrate animals. It was extracted while Dr. Stern and his co-workers were purifying enzymes in a powerful centrifuge, which separates molecules of mixed weight by whirling them at high speed.

Dr. Stern declared that the red giants appeared to be chemically different from any other known substance. Their biological function remains obscure. But the red color seems to be an intrinsic property of the molecules, not an impurity. "We plan," said Dr. Stern, "to study this interesting substance more extensively."

* The unit is the weight of the hydrogen atom.

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