SCIENCE - Chemical & Engineering News Archive (ACS Publications)

Nov 5, 2010 - Mesquite yields arahinose while corn cobs and other grain refuse are fertile sources of xylose. It has been taken for granted that each ...
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THE CHEMICAL WORLD THIS WEEK Mass., plant for producing high styrene copolymer latices i n volume and a paint latex of superior water and scrub resistance is i n the final development stage. In addition t o the styrene copolymers, the company now distributes polyvinyl acetate emulsions to the paint industry through R . T . Vanderbilt & Co., New York.

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Dow Chemical C o . is now producing morpholine, a ring compound containing both an amine and an ether group. It can b e used i n the formulation of waterresistant waxes and polishes. Morpholine may b e added to boilers and steam lines to maintain constant alkalinity, thereby minimizing corrosion. It is also used in the formulation of wax emulsions that cover vegetables during shipment and storage for moisture retention, and in the preparation of water-resistant adhesives. I t is "being made at Dow's Midland plant.

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Schwara Laboratories recently added eight more products to their line of fine chemicals. T h e newly added chemicals are: acetyl phosphate, lithium (high purity); allantoic alloxan; alloxantin; 2,6-dichloropyrinaidine; ribose-5-phosphate, barium; 2,4,6-triaminopyrimidine; and uric acid.

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CHEMICAL

7 - C a r b o n Sugar Blasts Concept O f Phof-osynthetic Specificity Certain plants have long been prized among sugar chemists for t h e special saccharides they yield. Thus, Jerusalem artichoke has b e e n looked upon as a prime source of fructose, the nut of the ivory palm is famous for mannose. Mesquite yields arahinose while corn cobs and other grain refuse are fertile sources of xylose. It has been taken for granted that each of these plants has a peculiar set of enzymes that enables it to synthesize its special sugars to the exclusion of others. This concept was exploded last week w h e n Melvin Calvin of the University of California announced that every plant cell is alike i n so far as photosynthesis is concerned. Spealcing at Howard University in Washington, Dr. Calvin reported that his studies with all types of plants have revealed that all can make the same sugars —from the same intermediates. But what the plant does with the primary products of photosynthesis may b e peculiar to each. M a n y of these differences may lie in the plant's dark reactions, or those that proceed in the absence of light, such as, for instance, t b e formation of citric acid. Dr. Calvin has demonstrated that dark reactions are completely different from those induced by chlorophyll in the light. Ultimately, tlie differences between plants is exhibited more in what they store than in w h a t they make.

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About a year ago, Dr. Calvin postulated a vital role in photosynthesis for sedoheptulose (/. Am. Chem. Soc. 7 3 , 2 9 7 0 ) . Sedoheptulose, a 7-carbon sugar with the altrose configuration, has been known for 3 5 years since its discovery by LaForge in the succulent plants of the sedum family, a type of cactus. But in his report of a year ago, Dr. Calvin indicated that this sugar had been found as a monophosphate in a number of plants, including Chlorella, Scenedesmus, the leaves of barley seed­ lings, soy beans, geranium, and others. "It now appears," said Dr. Calvin last week, "that sedoheptulose can be made to form extremely rapidly under very spe­ cial circumstances in any plant from the blue-green algae o n up."

REMOVE A LL ACIDS

Tracing with Radioactivity Working with C"-labeled carbon di­ oxide, Dr. Calvin and coworkers are follow­ ing the path of carbon in photosynthesis. One of their methods is to work in what they call the "steady state" of constant illumination (to avoid complicating the system with transient changes ) and to con­ trol photosynthesis by time of contact with labeled carbon dioxide. Shortest useful time is about four seconds, following which the reactions are terminated by dumping the substrate into boiling alcohol. The reaction products are separated and identi­ fied by paper chromatography. By means of these studies, the California group has been getting closer and closer to the mechanisms by which carbohydrates are formed, and their evidence indicates that hexoses are t h e result of direct combi­ nation of two 3-carbon units from phospboglyceric aldehyde, which, to date, is the smallest identified moiety which seems directly involved in the photosynthetic cycle. This, it is postulated, is fonned by carboxylation of a 2-carbon unit with CO«. These PGA units then join head-to-head to form hexoses as indicated by the fact that labeled atoms show up first in hexoses in the two center carbons. The sedoheptulose evidence, however, substantiates previous indications that there is another type of carboxylation pe­ culiar to photosynthesis which leads to a four-carbon compound, according t o Dr. Calvin, who points out that sedoheptulose appears to be formed from 3 - and 4-carbon units. Furthermore, this new type of car­ boxylation is even more rapid than the one that results in phosphoglyceric aldehyde (and the hexoses) because sedoheptulose can be made to appear before much PGA is formed. Conditions favorable to the formation of sedoheptulose are those in which carbon dioxide starvation is rigor­ ously avoided; otherwise PGA is obtained predominantly. The ultimate function of sedoheptulose in those plants which do not store this sugar seems to be connected with the step­ wise regeneration of the 2-carbon acceptor in a cycle involving the 5-cafbon sugar ribulose (C&EN, 29, 3 9 6 7 ) and a triose. V O L U M E

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