THE PROTEIN FACTORY. All living organisms have ribosomes within each of their cells that are directed by the genetic code to function as factories, carrying out the synthesis of proteins. Cells having high rates of protein synthesis, such as the pancreas, have millions of ribosomes. DNA carries instructions to messenger RNA (mRNA) for building specific proteins. Transfer RNA (tRNA) then brings the amino acids to the ribosome where they are sequentially added to a growing protein chain.
Ribosomes found in eukaryotic cells (animals, plants, fungi) and prokaryotic (bacterial) cells have a similar structure and function. In the former, they are attached to rough-endoplasmic reticular membranes and, in the latter, suspended in the cytosol, the fluid component of cytoplasm. That ribosomes are found across all kingdoms of life suggests that the ribosome evolved early in the evolutionary process. Palade determined that ribosomes are made up of large and small subunits and that there are subtle differences in density (mass per unit volume) between the ribosomes in prokaryotic and eukaryotic cells. This is of practical significance in the treatment of bacterial infections. Certain antibiotics, such as erythromycin and the tetracyclines, selectively inhibit the protein synthesis in bacteria without having such effects in the patient’s cells.
SEE ALSO Cell Nucleus (1831), Enzymes (1878), Penicillin (1928), DNA Structure (1953), Cracking the Genetic Code for Protein Biosynthesis (1961).
The primary function of ribosomes is the manufacture of proteins. The image depicts a model of a eukaryotic ribosome, which differs in structure from a prokaryotic ribosome.
1956
Parallel Universes • Clifford A. Pickover
Hugh Everett III (1930–1982), Max Tegmark (b. 1967)
A number of prominent physicists now suggest that universes exist that are parallel to ours and that might be visualized as layers in a cake, bubbles in a milkshake, or buds on an infinitely branching tree. In some theories of parallel universes, we might actually detect these universes by gravity leaks from one universe to an adjacent universe. For example, light from distant stars may be distorted by the gravity of invisible objects residing in parallel universes only millimeters away. The entire idea of multiple universes is not as far-fetched as it may sound. According to a poll of 72 leading physicists conducted by the American researcher David Raub and published in 1998, 58% of physicists (including Stephen Hawking) believe in some form of multiple universes theory.
Many flavors of parallel-universe theory exist. For example, Hugh Everett III’s 1956 doctoral thesis “The Theory of the Universal Wavefunction” outlines a theory in which the universe continually “branches” into countless parallel worlds. This theory is called the many-worlds interpretation of quantum mechanics and posits that whenever the universe (“world”) is confronted by a choice of paths at the quantum level, it actually follows the various possibilities. If the theory is true, then all kinds of strange worlds may “exist” in some sense. In a number of worlds, Hitler won World War II. Sometimes, the term “multiverse” is used to suggest the idea that the universe that we can readily observe is only part of the reality that comprises the multiverse, the set of possible universes.
If our universe is infinite, then identical copies of our visible universe may exist, with an exact copy of our Earth and of you. According to physicist Max Tegmark, on average, the nearest of these identical copies of our visible universe is about 10 to the 10100 meters away. Not only are there infinite copies of you, there are infinite copies of variants of you. Chaotic cosmic inflation theory also suggests the creation of different universes—with perhaps countless copies of you existing but altered in fantastically beautiful and ugly ways.
SEE ALSO Wave Nature of Light (1801), Schrödinger’s Cat (1935), Cosmic Inflation (1980), Quantum Computers (1981).
Some interpretations of quantum mechanics posit that whenever the universe is confronted by a choice of paths at the quantum level, it actually follows the various possibilities. Multiverse implies that our observable universe is part of a reality that includes other universes.
1957
Antidepressant Medications • Wade E. Pickren
Roland Kuhn (1912–2005)
In 1952, a drug under development for use with tuberculosis patients, iproniazid, was found to be effective in treating depression. Approved for use in 1958, it was withdrawn three years later when it was found to cause serious liver damage. In 1955, imipramine was being considered as a treatment for people suffering from schizophrenia at a mental hospital in Switzerland, but the results were not positive. Psychiatrist Roland Kuhn decided to try the drug on forty depressed patients, and the results were all positive. Patients became livelier, their voices were stronger, they were able to effectively communicate, and hypochondriacal complaints all but disappeared. He published his results in 1957.
Imipramine moved to the market under the brand name Tofranil. It was the first of what soon became a family of drugs labeled tricyclics (so named because of their three-ring chemical structure). Tricyclics work by inhibiting the reuptake of the neurotransmitters norepinephrine and, to a lesser degree, serotonin, thus initially making more of them available for use in the brain. There can be unpleasant side effects, however, such as dry mouth, constipation, weight gain, and sexual dysfunction.
Another antidepressant that also works by inhibition was discovered shortly after imipramine. The class of drugs known as monoamine oxidase inhibitors (MAOI) prevents the action of an enzyme, monoamine oxidase, which breaks down such neurotransmitters as serotonin and norepinephrine. MAOI side effects are even more dangerous than those of the tricyclics, so they are seldom prescribed today.
In 1987, a second-generation antidepressant with the trade name Prozac was approved for use by the US Food and Drug Administration. Prozac and other drugs like it are selective serotonin reuptake inhibitors (SSRIs). Just as their name implies, they inhibit the reuptake of serotonin in the synapse. The response has been phenomenal: within three years of its release, Prozac was the number-one drug prescribed by psychiatrists, and by 1994 it was the number-two best-selling drug of any kind in the world. It does not have many of the side effects of other antidepressants. Indeed, it is used by millions of people who suffer from no mental disorder at all but who use the drug to enhance their personality, lose weight, or increase their attention spans.
SEE ALSO Morgagni’s “Cries of Suffering Organs,” Neuron Doctrine (1891), Cerebral Localization (1861), Psychoanalysis (1899), Cognitive Behavior Therapy (1963).
Many species of passionflower have been found to contain beta-carboline harmala alkaloids, which are MAO inhibitors with antidepressant properties.
1957
Space Satellite • Marshall Brain
Think about your typical satellite, for example a photographic satellite that takes pictures of the Earth. On the one hand it is not that complicated. It has a high-resolution digital camera attached to a telescope that acts as a lens. It has solar panels and batteries to provide electricity. It has a radio to communicate with Earth and an antenna. There’s nothing really surprising. These are the same parts you would expect to find on any remote camera system—the camera itself, a power source, and a radio link.
So why does a satellite like this cost millions of dollars? It is largely because of the special considerations that go along with flying in space. Engineers have to keep the satellite functioning in an inaccessible, harsh environment. These challenges were first faced when Russian scientists launched the first space satellite, Sputnik 1, in 1957. Since then, satellites have gotten far more sophisticated.
Take for example the computer in a modern satellite. Engineers cannot use a normal computer in space. Everything must be radiation hardened at the time of manufacture to prevent cosmic rays, solar particles, and other forms of radiation from disrupting the circuits. The computer will then be triple redundant, with a voting system to detect if one of the three fails.
The satellite has to keep itself properly oriented at all times. It usually
does this with a combination of sun trackers, star trackers, and reaction wheels. The reaction wheels can speed up or slow down in order to change the orientation of the satellite. There will also be thrusters and plenty of fuel (e.g., 300 pounds or 150 kg) to last a decade or more.
The solar cells are not typical. They are radiation-hardened, high-efficiency cells. And the batteries are not standard either. Engineers have created special nickel-hydrogen batteries that handle tens of thousands of charge/discharge cycles and can last more than a decade.
And then there is one final thing: a massive amount of reliability testing, certification, redundancy, etc., including assembly in a clean-room environment, testing in a hard vacuum, vibration tests, and so on. There is no way to repair the satellite if something goes wrong, and it has to work for many years in space. All of this work and all of these special components make any satellite an expensive proposition.
SEE ALSO First Humans in Space (1961), Hubble Telescope (1990), Global Positioning System (GPS) (1994).
Three crew members of mission STS-49 hold on to the 4.5-ton International Telecommunications Organization Satellite (INTELSAT) VI, 1992.
1958
Central Dogma of Molecular Biology • Michael C. Gerald with Gloria E. Gerald
Francis Crick (1916–2004), James D. Watson (b. 1928), Howard Temin (1934–1994), David Baltimore (b. 1938)
In 1958, five years after Watson and Crick discovered the molecular structure of deoxyribonucleic acid (DNA)—the double helix—Crick proposed the central dogma of molecular biology, and this he popularized in a paper in Nature in 1970. In its basic terms, the central dogma states that genetic information flows in only one direction from DNA (“transcription”) to RNA (“translation”) to proteins.
Information is “transcribed” from a section of DNA to a newly assembled piece of messenger RNA (mRNA); mRNA makes a copy of one of the two strands of DNA, which serves as a template. The mRNA then travels from the nucleus to the cytoplasm where it binds to a ribosome. The ribosome translates the instructions as a codon, a three nucleotide sequence that spells out the order in which amino acids are to be added to the growing peptide chain. The final step involves the faithful replication of DNA to a daughter cell, carried out by the process of mitosis.
As originally formulated, the sequence was never translated backwards from DNA to RNA. When the enzyme reverse transcriptase was independently discovered in 1970 by Howard Temin at the University of Wisconsin-Madison and David Baltimore at MIT, this upset the premise of the central dogma. For this work, Temin and Baltimore were co-recipients of the 1975 Nobel Prize. Subsequently, it was found that reverse transcriptase is present in retroviruses, such as the human immunodeficiency virus (HIV), and converts DNA from RNA. In addition, and as another exception to the central dogma, not all DNA is involved in programming the synthesis of proteins. Some 98 percent of human DNA is noncoding DNA (dubbed “junk DNA”); its biological function has not yet been determined.
Semantic issues were also raised. In his 1988 autobiography, What Mad Pursuit: A Personal View of Scientific Discovery, Crick commented that the term “dogma” was ill-advised. He chose not to use the word “hypothesis,” which, in retrospect, would have been far more appropriate. Dogma is a belief that cannot be doubted—certainly not the case when used here.
SEE ALSO DNA Structure (1953), Ribosomes (1955), Cracking the Genetic Code for Protein Biosynthesis (1961), Epigenetics (1983).
This image depicts the flow of genetic instructions from DNA, to RNA, to the production of amino acids, which link together to form proteins.
1958
Integrated Circuit • Clifford A. Pickover
Jack St. Clair Kilby (1923–2005), Robert Norton Noyce (1927–1990)
“It seems that the integrated circuit was destined to be invented,” writes technology-historian Mary Bellis. “Two separate inventors, unaware of each other’s activities, invented almost identical integrated circuits, or ICs, at nearly the same time.”
In electronics, an IC, or microchip, is a miniaturized electronic circuit that relies upon semiconductor devices and is used today in countless examples of electronic equipment, ranging from coffeemakers to fighter jets. The conductivity of a semiconductor material can be controlled by introduction of an electric field. With the invention of the monolithic IC (formed from a single crystal), the traditionally separate transistors, resistors, capacitors, and all wires could now be placed on a single crystal (or chip) made of semiconductor material. Compared with the manual assembly of discrete circuits of individual components, such as resistors and transistors, an IC can be made more efficiently using the process of photolithography, which involves selectively transferring geometric shapes on a mask to the surface of a material such as a silicon wafer. The speed of operations is also higher in ICs because the components are small and tightly packed.
Physicist Jack Kilby invented the IC in 1958. Working independently, physicist Robert Noyce invented the IC six months later. Noyce used silicon for the semiconductor material, and Kilby used germanium. Today, a postage-stamp-sized chip can contain over a billion transistors. The advances in capability and density—and decrease in price—led technologist Gordon Moore to say, “If the auto industry advanced as rapidly as the semiconductor industry, a Rolls Royce would get a half a million miles per gallon, and it would be cheaper to throw it away than to park it.”
Kilby invented the IC as a new employee at Texas Instruments during the company’s late-July vacation time when the halls of his employer were deserted. By September, Kilby had built a working model, and on February 6, Texas Instruments filed a patent.
SEE ALSO Transistor (1845), ENIAC (1946), Quantum Computers (1981).
The exterior packaging of microchips (e.g., large rectangular shape at left) house the integrated circuits inside that contain the tiny components such as transistor devices. The housing protects the much smaller integrated circuit and provides a means of connecting the chip to a circuit board.
1959
Structure of Antibodies • Clifford A. Pickover
Paul Ehrlich (1854–1915), Rodney Robert Porter (1917–1985), Gerald Maurice Edelman (1929–2014)
The germ theory of disease, proposed in the mid-1800s, suggested that microorganisms cause many diseases, and people wondered how the body attempted to defend itself against such foreign invaders. Today, we know that antibodies (also called immunoglobulins) are the protective proteins that circulate in our bodies and identify and neutralize foreign substances, called antigens, which include bacteria, viruses, parasites, transplanted foreign tissues, and venoms. Antibodies are produced by plasma B cells (a kind of white blood cell). Each antibody consists of two heavy chains and two light chains made of amino acids. These four chains are bound together to form a molecule shaped like the letter Y. Variable regions at the two upper tips of the Y bind to antigens, thereby marking them for other parts of the immune system to destroy. Many millions of different antibodies can exist with slightly different tip structures. Antibodies can also neutralize antigens directly by binding to them and, for example, preventing the pathogens from entering or damaging cells.
Antibodies circulating in the blood play a role in the humoral immune system. Additional immune players—phagocytes—function like single-celled creatures that engulf and destroy smaller particles. The binding of antibodies to an invader can mark the invader for ingestion by phagocytes.
Tests used to detect particular antibodies may lead a physician to suspect, or rule out, certain diseases such as Lyme disease. Autoimmune disorders may be triggered by antibodies binding to the body’s own healthy cells. Antiserums can sometimes be made by injecting animals with an antigen and then isolating the antibodies in the serum for use in humans.
Paul Ehrlich coined the word antibody (Antikörper in German) around 1891, and he proposed a mechanism in which the receptors on cells attached to toxins in a tight lock-and-key fit to trigger antibody production. English biochemist Rodney
Porter and American biologist Gerald Edelman won the 1972 Nobel Prize for their independent research, which started around 1959 and elucidated the antibody’s Y-like structure, as well as identifying heavy and light chains.
SEE ALSO Smallpox Vaccine (1798), Germ Theory of Disease (1862), Discovery of Viruses (1892).
Artist’s concept of Y-shaped antibodies circulating through the bloodstream.
1960
Laser • Clifford A. Pickover
Albert Einstein (1879–1955), Leon Goldman (1905–1997), Charles Hard Townes (1915–2015), Theodore Harold “Ted” Maiman (1927–2007)
“Laser technology has become important in a wide range of practical applications,” writes laser expert Jeff Hecht, “ranging from medicine and consumer electronics to telecommunications and military technology. . . . 18 recipients of the Nobel Prize received the award for laser-related research.”
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