duction) of the quark track to the tracks of singly charged particles is 0.48 ± 0.05. After ruling out a number of possible causes, the phys icists state, "The only other explanation we can see is that the track is due to a fractionally charged particle." Thi;, the quark would be. In theory, the quark has an electric charge either one third or two thirds of an electron's. It can be either lighter or heavier than a proton, which would be formed by three of them. The physicists found the name for their unusual particle in the line "Three quarks for Muster Mark" in James Joyce's Finnegan's Wake. The quark was proposed about five years ago independently by Dr. Murray Gellmann and Dr. George Zweig of California Institute of Technology. The proton could actually be lighter than its constituent quarks because the quarks, in combining, could lose most of their mass as binding energy. This is analogous to the slight loss of mass by a neutron and proton in forming the heavy-water nucleus. Reacting to the report from Down Under, physicists at Brookhaven Na tional Laboratory, scene of an earlier quark hunt, stay reserved. One sci entist states, "One has to be extremely careful, as there is a reasonable chance for error." In the Australian scientists' current article, they state, "The appearance of the tracks could not be due to a statistical fluctuation in the number of ions produced because the numbers involved were much too large." PROTEINS:
Synthesis in Two Steps Protein synthesis may be a two-step process, says Dr. W. Ward Pigman, New York Medical College biochemist. Polypeptides are made from amino acids in one part of a cell and then linked together to form finished pro teins in another. Speaking at the International Symposium on Blood and Tissue Antigens in Ann Arbor, Mich., Dr. Pigman notes that the poly peptide building blocks destined for the same part of the same protein are not necessarily identical. This has important consequences for modern theories of evolutionary change. Studying submaxillary gland cells of cattle, pigs, and sheep, Dr. Pigman concentrates on mucins—glycoproteins of molecular weight about 1.3 millionproduced by these glands. He has isolated polypeptides from cell ma terial (of cattle) containing 20 to 28 amino acid units and separated the peptides. Dr. Pigman interprets images of particles 25 A. in diameter, seen in
Ribosome assembled peptides migrate to Golgi membrane for protein synthesis Golgi apparatus Protein Endoplasmic reticulum (Peptide synthesizing site; energy consumption site ;ite; activated building u n i t
\n f S | L ^ < ^ n //JS β f/± r^iirMm Ribosomes CTTTTTv * ,, C tmg} ^UuSh ^ ^ Sltes o n GoJ (m_RNA) s ) ^W^ \ . · · ^ ^ & a p p Ä (enzynjij
electron micrographs from Dr. J. M. Shackelford's University of Alabama group, as molecules of building block polypeptides. The particles lie near ribosomes in cells and are of the estimated size for 20 to 28 amino acid segments. At the membranes of Golgi bodies—cell organelles previously described to have roles in protein "packaging,"—there are particles which Dr. Pigman suggests are completed glycoprotein molecules. The New York biochemist thus concludes that peptide synthesis may occur at ribosomes, but assembly to finished proteins occurs on Golgi body membranes—a function not previously assigned to the Golgi apparatus. In addition, Dr. Pigman notes that mucin contains no aromatic amino acids such as histidine or trytophan, yet the polypeptides have ultraviolet absorptions around 260 to 270 πΐμ.
Glycoprotein molecules
This leads him to postulate an activat ing group, perhaps a purine base, on the polypeptide molecules. Using trypsin to catalyze hydrolysis of glycoproteins, Dr. Pigman detects substitution of amino acids at various positions in the protein chain. "This suggests," he says, "that each cell has the capacity to synthesize slightly dif ferent homologous peptides and pro teins. Therefore a theory about an evolutionary process or 'natural selection' which can occur rapidly in all cells must be considered." With each cell synthesizing similar, not identical, peptide units, Golgi membrane polymerases would reject segments that cannot be used, and a repressor mechanism might operate to cause mRNA's that produce the unused homologs to disappear.
NUCLEAR POWER:
11-State Compact
Biochemist Pigman Two-step process
When Washington's Governor Daniel Evans gaveled the session to order last week, he marked the creation of the Western Interstate Nuclear Com pact. The delegates who attended the two-day meeting he hosted at Seattle's Edgewater Inn came from the western states to put their seal to an institution that has been gestating for years. WINC is patterned after the highly successful Southern Interstate Nuclear Board, which dates from 1961. One of the western compact's objectives, for instance, is to gain recognition and support at the federal level through a unified governmental voice of the participating states. Too, it will be a vehicle through which uniform state regulations pertaining to interstate commerce of nuclear materials may be drawn up. And the compact seeks to foster commercial and industrial SEPT. 29, 1969 C&EN
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