THE CHEMICAL WORLD THIS WEEK of the samples to confirm that they were similar with those reported in the literature. Not only was the identi fication of ions possible using ESC A, but also the oxidation states of the ions were obtained. Semiquantitative analyses by ESCA have been made, they report; however, the technique is so new that any per cent composition must await further research. Dr. Davis did estimate that the sodium ion spectrum is so strong that it could represent up to 807c of the cations present in most samples. Poly water also contains borates in various degrees of polymerization and prob ably numerous types of silicates with differing degrees of polymerization. "Since both of these are prone to polymerization, their presence cer tainly would explain the viscosity and temperature effects reported for poly water samples," Dr. Davis says. The presence of aliphatic- and aro matic-type carbon explains why cer tain polywater samples "bum" on exposure to ruby lasers during Raman studies, he points out. "Likewise, it could explain the fluorescence of poly water. Also, since the total amount of carbon is only a few per cent of the samples' total mass, one would not expect to see infrared bands in the C—H region." Polywater is made by condensing water in silica or borosilicate capil lary tubes with diameters of 1 to 10 microns. The material produced is stable to 300° C , up to 15 times more viscous than water, has a density of 1.4 grams per cm. 3 , and has a high refractive index. Some scientists have suggested that polywater is a polymer of three-center Ο—Η—Ο units, including 12-membered rings of al ternating oxygen and hydrogen atoms. Other scientists have suggested a squarelike structure with Η—Ο—Η units forming two opposite corners, and oxygen with two vacant orbitals forming each of the other two corners. Others have suggested that the struc ture of the substance is analogous with ice-II, which has a rhombohedral structure. One of the primary problems in studying polywater is that only micro gram samples have been made and, therefore, analysis of an individual sample by more than one technique by several scientists is impossible. By the time the Lehigh conference closed last week, most of the attend ees were more confused than ever about whether polywater (as a poly mer of water) does indeed exist. However, few were willing to say it did not exist or to speculate on what polywater was, if it wasn't a polymer of water. 8 C&EN JUNE 29, 1970
HEAVY WATER:
Canada's Quandary Canada may have found a way out of the maze of problems surrounding its venture into heavy water production. Atomic Energy of Canada, Ltd. (AECL), needs 2000 tons of heavy water between now and 1972 to meet commitments for nuclear power gen erating stations using heavy watermodified reactors and natural uranium. If all goes right, where practically everything in the past has gone wrong, AECL will meet its heavy water deadline. Cause of Canada's quandary is the failure of Deuterium of Canada, Ltd., to start up its 400 ton-per-year plant at Glace Bay, N.S. The plant was scheduled for startup in 1966 (C&EN, Dec. 16, 1968, page 18). It still isn't operating, but the $106 million plant won't be scrapped. A spokesman for AECL says startup is now scheduled for 1972. For the rest of 1970, Canadian General Electric's heavy water plant at Port Hawkesbury, N.S., will have to supply the country's needs. The 420 ton-per-year plant is in the proc ess of starting up. Should the Port Hawkesbury plant reach full production without a hitch, Canada will still be 1000 tons short of its heavy water requirement in 1972. AECL says it believes this shortage can be made up from "var ious sources," but if necessary the government is prepared to drain cer tain smaller reactors to obtain the nec essary heavy water. After 1972, the going should be downhill. The Canadian GE plant should be producing by then. Nego tiations are being held with Canadian GE and the government of Nova Scotia with the aim of having Cana dian GE take over management of the Glace Bay plant. Plans call for this plant to contribute an additional 400 tons per year of deuterium oxide after 1972. In addition, Lummus of Can ada is about 80% complete with en gineering and 20% complete with construction of the first 400 ton-peryear D 2 0 unit at the Bruce plant at Port Douglas on Lake Huron. A second 400 ton-per-year unit at Bruce is scheduled for startup in 1973. Canada thus hopes to be in a posi tion to produce 1600 tons of heavy water annually by 1973. Ontario Hydro is building a 3000Mw. nuclear generating station due on stream in 1976 adjacent to the Bruce plant. The station will cost $944 mil lion and will require 3000 tons of heavy water for moderation. The Bruce heavy water plant is based on the design of Canadian GE's Port Hawkesbury unit. Both
were engineered and constructed by Lummus. Although more than 30 processes for D 2 0 production are known, the "GS," or dual temperature atomic exchange process, pioneered by the U.S. Atomic Energy Commission at Savannah River, Ga., has proven most efficient. Specifically, the process in volves an exchange of deuterium with hydrogen at about 20 atm.
MOLECULAR BIOLOGY:
No Route to Drugs "I don't see much chance that de velopments in molecular biology will lead to the design of new drugs in the foreseeable future," says Merck Sharp & Dohme's vice president for developmental research, Dr. Robert G. Denkewalter. This branch of sci ence, in fact, hasn't yet had much im pact on the therapy of diseases, he maintains, nor is it likely to have in the years immediately ahead. This viewpoint may be iconoclastic to many in light of the prominence of those that extol the virtues of mo lecular biology. Nevertheless, there was grudging acceptance of the idea on the part of those who heard Dr. Denkewalter at the 12th national symposium that the ACS Division of Medicinal Chemistry held last week in Seattle, Wash.
Merck's Denkewalter Inhibit the exercise When Dr. Denkewalter speaks he musters a considerable amount of at tention from his colleagues who admire his chemical accomplishments. For instance, he headed the team at Merck that synthesized bovine pancre atic ribonuclease, the first, and to date the only, enzyme to be made in the laboratory. (A team at Rockefeller University led by Dr. Robert B. Mer-
rifield also synthesized the enzyme at the same time by an alternate route, C&EN, Jan. 20, 1969, page 15.) Nor is Dr. Denkewalter knocking mo lecular biology as such. "Develop ments in this field of science have been truly amazing/' Dr. Denkewalter says. On the other hand, an overempha sis on molecular biology, he believes, could inhibit the exercise of some of the more individualistic approaches to finding new agents for combating dis ease. Screening of chemical com pounds, of course, will continue to be an important means of discovering drugs. But some of the therapeutic breakthroughs that are yet to be made will come about, he maintains, some what as accidental findings in the wake of isolated observations by nu merous individuals. The ability of a scientist to link together a number of diverse facts and to use the knowledge as a base on which to build a rational argument for further research will, in Dr. Denkewalter's opinion, continue to be a key ingredient in drug therapy advances.
CHEMICAL BONDS:
Metals and Enzymes "Multiple juxtapositional fixedness" (MJF) is the tongue-in-cheek term that Dr. Daryle H. Busch has coined to describe the unusually strong bond ing that occurs between metal ions and some ligands, and to account for certain aspects of metal-enzyme ac tivity. Nevertheless, Dr. Busch notes that he was serious in his search for a phrase that would describe the prin ciple of kinetic and thermodynamic stabilization that occurs whenever cer tain groups are so arranged in space that they can't undergo stepwise dis sociation from a metal ion by the usual pathways. The Ohio State Uni versity professor of chemistry de scribed the principle at the 25th an nual Northwest Regional ACS Meet ing in Seattle. The principle may well be of key importance in helping explain the structure of biological systems such as enzymes, many of which depend on a metal complex to function properly. The geometric arrangement of the groups holding a metal ion to a pro tein is such that removing the metal may require disrupting the complex by way of an unusual mechanism. This, in turn, would result in produc ing a slow rate of decomposition, en suring stability of the molecules. Referring to his studies with model compounds, Dr. Busch notes that com plexes of Ni 2 + and ammonia or linear amines decompose very rapidly (within fractions of a second) in an
a stronger catalyst when it is contained within an enzyme structure suggests that the bonds that the metal forms with the donor atoms of the protein are strained, and that these bonds don't contribute the usual amount of electron density to the metal, Dr. Busch says. Consequently, he reasons, a metal ion in such a situation can attract electrons from a substrate molecule more effectively than it would otherwise. "This raises the question as to how the bonding of the metal ion can be normal, or even enhanced, in the very stable complex while at the same time involving bonds that are weakened," Dr. Busch points out. The MJF effect offers a plausible explanation to this apparent paradox, he maintains.
3 m b "o
ι ft
OSU's Dr. Busch Multiple juxtapositional fixedness
acid medium. On the other hand, the complex involving Ni 2 + and 1,4,8,11tetraazacyclotetradecane (a cyclic structure that contains four electrondonating nitrogen atoms) is stable for many weeks in aqueous acid. The stability of the complex doesn't depend on the metal ion being totally imbedded in and surrounded by the ligand molecule, Dr. Busch finds. For instance, in the case of the Ni 2 + com plex with im-anhydroaminobenzaldehyde, the three metal-nitrogen bonds occur on only one face of the mole cule's octahedral structure leaving the metal ion exposed. Yet because of multiple juxtapositional fixedness, the complex withstands stepwise breaking of the bonds in the acid me dium. The requirements for such a high degree of stability or MJF, it seems, are that there be a minimum number of bonding sites in the ligand—prob ably no less than three—that are so fixed in space that they all bind to the metal ion, and that no one bond can dissociate without the entire lig and structure undergoing some sub stantial change, Dr. Busch conjectures. MJF, in fact, results in the overall total strength of bonding being far greater than the sum of the strength of each individual bond, the OSU chemist says. In the case of métallo enzymes, he continues, conformation of the protein structure probably brings the electrondonating groups of the polypeptide chain into such a fixed array as to promote electron donation with the metal ion. The net result of the ensuing MJF is that the metal ion can't be liberated from the complex without changing the conformation of the protein, which amounts to denaturing it, he adds. The ability of a metal ion to act as
MILITARY:
Random Job Matching The Selective Service System has taken considerable pains to ensure that the 1971 draft lottery in Washington this week will be fair and random. The National Bureau of Standards, for instance, has prepared 50 packets of computer-scrambled dates and numbers from which two sets will be randomly chosen for stuffing into capsules used in the drawings. But the randomness Selective Service is working so hard to attain in the draft lottery, according to some service
One third of chemists entering Army in 1969 served in infantry Occupational grouping Infantry, gun crews, allied specialists Electronic equipment repairs Communications and intelligence Medical and dental specialists Other technical and allied specialists Administrative specialists and clerks Electrical/mechanical equipment repairs Craftsmen Service and supply handlers Others Total
Chemical Chem- engiists* neers* 356
146
42
10
42
8
176
30
100
10
126
28
178 10
14 2
54 96 1180
40 40** 330
*AII degree levels combined. **Military occupation assignment in process. Source: Department of Defense
JUNE 29, 1970 C&EN 9
