| THE TOUCHSTONE OF LIFE Molecular Information, Cellular Communication, and the Foundations of Life Werner R. Loewenstein New York: Oxford University Press, 1999 |
Rating: 5.0 High |
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| ISBN 0-19-511828-6 | 366p. | HC/BWI | $30.00 | |
The scope of this book is vast, and the ambitions of its author immense — nothing less than describing the cosmic origins of information in the Big Bang, and how that information is incorporated into living systems by self-assembling molecules.
Unfortunately, Dr. Loewenstein stumbles at times when he attempts to explain information theory and the intricacies of particle physics. For example, on page 15 he states that an average protein "demon" can extract about half the information present in its environs, or about 5x10^24 bits per mole. This seems wrong, but I will have to run the calculation myself to be sure. Later, on page 24, I find the statement that "nuclei with 5 or 8 particles are not stable." Really? I guess we just lost our world supply of beryllium.
| M E A C U L P A |
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| 1 June 2004 |
Loewenstein is right about this last statement, and I am wrong. What he is talking about is atomic mass. It is true that an atomic nucleus with mass=5 or mass=8 is unstable. (See e.g. Chown, The Magic Furnace, page 169.) |
When describing matters within his own field, he does much better. It is clear that molecular biology is a subject he has studied for long and understands thoroughly. However, I found the style and structure of the book impediments to clear understanding. The first five chapters cover the same ground repeatedly, and the author's Britishisms often caused me to do a mental double-take. It was only when I got to Chapter 6 that I felt I had reached the heart of the book.
Here, I found meaty passages like the following:
These building blocks [amino acids and nucleoside bases] were shown to assemble "spontaneously" in experiments simulating the early environment on Earth (such molecular syntheses are ruled by the principle of directly energized short chain elongation, as discussed in Chapter 4), and nucleosides might have formed from prebiotic precursors through mineral catalyzed reactions. It has also been shown that from these building blocks protein-like molecules and short RNA chains can be polymerized in the absence of macromolecules; polypeptides of up to about 50 amino acids form on clays, proteinoids of 200 amino acids form in the presence of polyphosphates, and oligonucleotides of 40 nucleotides with RNA-like linkages (3'-5') form in the presence of phosphoric acid and zinc. – Page 105 |
This is wonderful stuff. However, I am disturbed that the book gives no credit to Stanley Miller and Harold Urey, who were among the first to demonstrate how such building blocks might have formed. Perhaps because they were Americans?
In any case, this chapter expresses more clearly the central message of the book, which is that DNA's linear chains preserve life's organizing information across generations, while RNA and the multitude of three-dimensional protein forms realize that information in living creatures. And all the molecular players constantly extract information from their environment and exchange it in a circus of shuttling covalent bonds.
The narrative proceeds from DNA and the mechanisms of its expression (including reverse transcription) through the four methods of inter-cell communication: a) hormones pass through the cell membrane into the interior (cytoplasm); b) a hormone attaches to a "relay" molecule in the membrane, and its message is passed to the interior; c) a protein molecule pair joins two cell membranes, passing information back and forth by conformational changes triggered by smaller molecules "docking" at their receptor sites, as in b; and d) interlocking sets of four-, five-, or six-lobed proteins form tunnels that allow ions (sodium, potassium, calcium) and smaller molecules (up to 16-18 Angstroms diameter, or about 1,000 daltons) to circulate between the cell interiors.
Each of these membrane-bridging mechanisms could fill a book by itself — as could intracell communication mechanisms. But the tunnels fascinated me above the other three. They are not simple ducts; they select what passes through them. In a crisis (defined as a sharp spike in calcium ion concentration) they can close down in milliseconds. The lobes, oval in cross-section, rotate much like the leaves of a camera shutter, isolating the affected cells. This fully reversible action is being investigated as a potential therapy for cancer.
Neurons (a relatively recent development in the cellular bestiary, according to Dr. Loewenstein) are discussed briefly in a penultimate chapter (13) which touches on the nature of mind and speculates that it may — as Roger Penrose theorizes — be due to quantum-mechanical coupling among nerve cells in the brain. This corresponds to what physicists call a Bose-Einstein condensate. Such entities have only recently been demonstrated on macroscopic scales, and they typically require cryogenic temperatures. But the laws of physics do not forbid such coupling at room temperature, and if it actually exists in the brain, the implications are astounding.
Describing such an arcane (and still only partially understood) subject in a book for lay audiences is fraught with perils. But Dr. Loewenstein succeeds admirably overall. Laced with phrases in foreign languages (Dr. Loewenstein apparently speaks Latin, Greek, French and German)1 leavened with historical excursions, and laden with far-reaching implications, this book is well worth reading despite its occasional (harrowing) passages. His excellent vocabulary in English (with words like urtext, monistic, and indagations) is an extra treat. A very detailed table of contents, a list of recommended reading, chapter by chapter reference section, and a fairly complete index add to its value.
My only cavil is that I wish he had enlisted a physicist and an electrical engineer to review the manuscript. This would have eliminated errors like those mentioned above, or like the following:
| Page 168: | "It took some two and a half billion years to get from the first cell to the first multicellular organisms, about twice as long to get from the first multicellular organisms to us." |
| The way I read this, it adds up to 7.5 billion years — a neat trick on a planet that formed about 4.5 billion years ago. |
| Page 184: | "Thus, in the International Morse Code 52, symbols consisting of sequences of dots and dashes map on 52 symbols of the alphabet, numbers, and punctuation marks;..." |
| Let's see: 26 letters (uppercase English) plus 10 digits (0-9) leaves 16 symbols for punctuation. I doubt that Morse includes so many. |
| Page 186: | "The teletype codes are comparable in quality to the codes in intercellular communication. There is enough information in each teletype signal to make the messages unambiguous. In fact, we can readily estimate the upper limit of the amount of information required for that; all we need is the number of coding symbols. These are the letters from a to z and the space — altogether 27 symbols in 'telegraph English' (which has no punctuation, capital letters, or paragraphs). For an upper-limit estimate, we assume all symbols to occur with equal probability. So, by virtue of equation 1, we get log 27 = 4.76 bits — the amount of information per letter needed for unambiguous communication." |
| This is not the teletype code. That has punctuation symbols. It definitely includes numbers. It also features a number of special symbols for carriage or terminal control — like the LINE FEED and CARRIAGE RETURN characters, as well as the BEL for an alert sound and a SHIFT to change letter case. The good doctor seems to confuse teletype with telegraph; they are not equivalent, and both include numbers. It sounds more like the outmoded Baudot code, which uses up to 5 parallel holes per symbol in paper tape, thus being capable of 32 discrete symbols maximum. |
| Page 188: | "It [the language translation machine] did quite well until it got to [Matthew] 26:41: 'the spirit is willing but the flesh is weak.' The translation read: 'el aguardiente es agradable pero la carne es insipida' (the liquor is agreeable but the meat is stale)." |
| Well, this is not Dr. Loewenstein's error, but inept programming. An adjective that implies volition ("willing") should in Spanish go with the noun "alma" (soul), not "aguardiente" — and this should condition the translation of the subordinate clause. (Actually, I've heard this as an English-Russian-English translation story, where it may be more plausible.) |
On page 189, in footnote 4, Loewenstein states that "all attempts to deduce the 64-word lexicon of the second tier ... have been unsuccessful so far." Yet, the very next page shows this 64-word code in full detail. How then was it deciphered?
Of grammatical errors, the principal one is omission of articles like "a", "an", and "the". These may be instances of some British convention unknown to me. (I only recently learned that Brits, when they talk of corn, mean any food grain.) This may also be true of his use of "elfs" — versus elves — in the third paragraph of page 51, or with the couplet reproduced on page 104:
When Adam delved and Eve span
Who was then a gentleman?
I always thought it read "Eve spun", going with the pronunciation rather than the spelling.
On page 16: "Consider now what happens when a photon of sunlight gets absorbed by matter. It ends up in many modes of smaller quantum — a state with less information." (Emphasis added.) This looks to me like it should be "quanta".
Finally, there are a number of terms left undefined, including: "daltons", "nucleosides" & "nucleotides", "desolvation" (page 81); "pseudogenes" (page 151); "endoplasmic reticulum" (page 172); and (referring to calcium) "coordination numbers" and "ionization energies" (page 237). A glossary would have been most welcome.
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