Life's Origin: The Beginnings of Biological Evolution

3. Formation of the Building Blocks of Life

chapter 3 Formation of the Building Blocks of Life stanley l. miller and antonio lazcano 78 INTRODUCTION Along with his books, notes, letters, and papers, Charles Robert Darwin bequeathed two recipes to succeeding generations. The first, written in his wife’s recipe book, describes the way to boil rice: Add salt to the water and when boiling hot, stir in the rice. Keep it boiling for twelve minutes by the watch, then pour off the water and set the pot on live coals during ten minutes—the rice is then fit for the table. His second recipe appears in a letter to his friend Joseph Dalton Hooker (figure 3.1). Sent on February 1, 1871, this letter summarizes Darwin’s rarely expressed ideas on the emergence of life and his views on the molecular nature of the basic biological processes: It is often said that all the conditions for the first production of a living organism are now present, which could ever have been present. But if (& oh what a big if) we could conceive in some warm little pond with all sorts of ammonia & phosphoric salts,—light, heat, electricity &c present, that a protein compound was chemically formed, ready to undergo still more complex changes, at the present day such matter would be instantly devoured, or absorbed, which would not have been the case before living creatures were formed. By the time Darwin wrote this letter, DNA had already been discovered , although its central role in genetic processes would not be Figure 3.1. Charles Darwin’s letter to Joseph Hooker, dated February 1, 1871. In spite of the handwriting, Darwin’s ideas on a “warm little pond” are readable. Adapted from Calvin 1969. deciphered for eighty years. Moreover, the role of proteins in many biological processes had been established, and many of the building blocks of life had been chemically characterized (table 3.1). Of equal significance, by Darwin’s day, the chemical gap separating living from nonliving systems had been bridged, at least in principle, by laboratory syntheses of organic molecules. These syntheses challenged the longentrenched tradition that organic compounds were fundamentally different from inorganic materials. In 1827, for example, Jöns Jacob Berzelius—probably the most influential chemist of his day—wrote that “art cannot combine the elements of inorganic matter in the manner of living nature.” In 1828, however, Berzelius’s friend and former student Friedrich Wöhler demonstrated that urea, an organic compound fundamental to higher organisms, could be formed in high yield “without the need of an animal kidney” simply by heating ammonium cyanate (Leicester 1974). Wöhler’s work represented the first recorded synthesis of an organic compound from purely inorganic starting materials. This benchmark experiment ushered in a new era of chemical research. By 1850, Adolph Strecker had achieved the laboratory synthesis of the amino acid alanine from a mixture of acetaldehyde, ammonia, and hydrogen cyanide; this work was followed by the experiments of Alexandr M. Butlerov, who showed that treatment of formaldehyde with a strong alkaline catalyst, such as sodium hydroxide, leads to the formation of sugars (table 3.2). 80 Stanley L. Miller and Antonio Lazcano TABLE 3.1 DISCOVERY AND CHARACTERIZATION OF IMPORTANT BIOCHEMICAL MONOMERS Year Discoverers Monomers 1810 W. H. Wollaston Cystine (urinary calculi) 1819 J. L. Proust Leucine (fermenting cheese) 1823 M. E. Chevreul Fatty acids (butyric to stearic) 1869 F. Miescher DNA (pus cells) 1882 A. Kossel Guanine (yeast nuclei) 1883 A. Kossel and A. Neumann Thymine 1886 A. Kossel and A. Neumann Adenine 1894 A. Kossel and A. Neumann Cytosine 1900 A. Ascoli Uracil 1909 P. T. Levene and W. A. Javok Deoxyribose 1913 W. Küsler Porphyrin 1906–1936 P. T. Levene et al. Ribose, ribonucleotides Based on Leicester (1974) and Letham and Stewart (1977). The laboratory synthesis of organic, biochemically relevant compounds was soon extended, offering an increasing array of products and more complicated experimental settings. By the end of the 19th century, electric discharges and diverse gas mixtures had been used to achieve the nonbiological synthesis of sugars and fatty acids (Glocker and Lind 1939). Work of this type was carried into the 20th century by several workers, notably Walther Löb and Oskar Baudish, who showed that amino acids could be synthesized by exposing wet formamide (CHONH2) either to a silent electric discharge (Löb 1913) or to ultraviolet (UV) light (Baudish 1913). At this time, however, no...