Membrane protein proposed as proton pump - C&EN Global

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The Chemical World This Week

GOAL ISSUES TOP WEEK'S ACTIVITIES Coal moved to the forefront last week. In one way or another, it was the focus of attention for labor, industry, environmentalists, and utilities. Items: • Negotiators for the coal industry and the United Mine Workers were hammering out the specific wording of a contract that might bring to an end the nation's longest-running coal strike—a strike that has begun to pinch utilities, although those companies in the chemical industry that rely on coal have been relatively unaffected as yet. • A series of comprehensive recommendations on coal production and use was made public, the result of two years of reasoning together by industrialists and environmentalists making up the National Coal Policy Project. • After receiving good notices last month from the Office of Technology Assessment (C&EN, Jan. 30, page 13), coal slurry pipeline proposals have begun to surface. Although most chemical operations in the U.S. do not use much coal either for feedstock or for fuel, some sites are heavily dependent on it. Among companies in this position, there seems to be no concern yet on running out of supplies because of the strike. But another month of delay on receiving new shipments could start to hurt. Possibly the largest coal-dependent chemical operation is that of Eastman Chemicals' huge complex at Kingsport, Tenn. A spokesman at Kingsport tells C&EN that the site still has coal reserves adequate for the short term and is still receiving some coal. No effect on operations is expected if the strike is settled within the next 20 to 30 days. Akzona, another company that has converted most of its plants to coal for fuel, says that coal stockpiles are still adequate for 40 to 80 days. The company says it started the winter with "immense inventories." Coal-dependent utilities in the east central U.S., on the other hand, have appealed to customers to reduce their use of electricity 25%. Edison Electric Institute, an industry association, says this cutback is likely to lead to closings of industrial plants and to layoffs. In contrast to such short-term 6

C&EN Feb. 13, 1978

mental chairman, oversaw the task forces and approved reports and recommendations in the name of the project, under the direction of the plenary chairman Francis X. Quinn, special assistant to the dean of Temple University's business school. In all, about 100 economists, attorneys, engineers, and scientists were involved, devoting more than 10,000 man-days to the project. The project did not reach agreement on all of the major environmental policy issues related to coal. Nevertheless, the project's report notes, the body of agreement is "impressively large and covers a wide range of issues." Indeed, the task force reports are quite detailed and, Decker: covers a wide range of issues in some cases, "painstakingly constructed." Not the least of its accomconcerns, the National Coal Policy plishments, project participants beProject addressed the long run. The lieve, is that for the first time, inproject is an attempt by industrialists dustrialists and environmentalists and environmentalists to search for have made a joint effort to reach a alternatives to the costly adversarial consensus on the environmentally battles that have raged in Congress sound utilization of a vital energy reand the courts. It began when Dow source. Chemical's corporate energy manager Meanwhile, Florida Gas Co., along Gerald L. Decker proposed the idea to with nine other utilities from Florida former Sierra Club president Lau- and Georgia, met last week in Winter rence I. Moss. Eventually, the initia- Park, Fla., to consider a 1500-mile tive came under the aegis of the coal slurry pipeline. The pipeline, Center for Strategic & International which would originate in the coal Studies at Georgetown university in fields of eastern Kentucky, would Washington, D.C., as the National deliver fuel to power plants in the two Coal Policy Project. southern states. Estimated costs of the project vary In operation, five task forces were responsible for working out positions from a low of $864 million for a 15 and making recommendations on five million ton-per-year system to a high issues: mining, coal transportation, air of $1.6 billion for a 45 million tonpollution, fuel utilization and con- per-year system. Mainline pipe sizes servation, and energy pricing. A ple- would vary from 28-inch-diameter for nary group, of which Decker is in- the smallest system to 48 inches for D dustry chairman and Moss environ- the largest studied.

Membrane protein propc ed as proton pump For membranes studies, Halobacterium halobium is so well characterized that it seems more a gift horse than a bacterium. Under certain growth conditions, it makes a special light-sensitive membrane for generating energy. Made in patches accounting for about half the cells' limiting membrane, t h a t special "purple membrane" contains a single protein, bacteriorhodopsin. The purple membrane acts as a proton pump and uses light to gen-

erate an electrochemical gradient. Last week Dr. Walther Stoeckenius of the University of California, San Francisco, presented a model on how this pump works chemically to the Second International Conference on the Molecular Basis of Cell-Cell Interaction, held in San Diego. Stoeckenius proposes that protons are pumped from inside the cell to the surrounding medium along chains of hydrogen bonds. The chains, he says, are part of the protein bacteriorho-

dopsin that is embedded in the membrane. Thus protons pass along the proteins in a kind of "hydrogen bucket brigade," as one scientist put it. Bacteriorhodopsin spans the halobacter membrane, zigzagging across in seven alpha-helical segments. The protein contains one molecule of retinal, a light-absorbing vitamin A derivative that helps give the purple membrane its color. Buried within the membrane (probably close to its outside face) and attached to the protein by a Schiff s base linkage, retinal plays a key part in proton pumping, according to the model. The proton-passing chain—presumably the protein—needs a switch to prevent the cell from continuously spewing them out. Without such a gap, "proton conductivity would short-circuit the proton gradient across the membrane," Stoeckenius explains. Retinal is a likely candidate for an on-off switch for the pump. It gains and loses a proton during the light reaction and it also undergoes a conformational change, Stoeckenius notes. Its affinity for protons also changes during the light reaction cycle. Thus, it might pick up a proton coming along the chain from the cell, swing across the gap in that chain within the membrane, and deliver the proton to the tail end of the chain and from there out of the cell. Stoeckenius calls this model "highly speculative," but notes that "it fits the main experimental observation." For example, protons need a path across the charge-abhorring membrane. But diffraction studies rule out a water pore, and other studies make it unlikely that the whole protein could flip around in the membrane to deliver protons from inside to the outside, he says D

chairman of the Senate Committee on Energy & Natural Resources. The committee is considering the nomination of Robert Thome for the Department of Energy's assistant administrator for energy technologies. Thorne was the manager of ERDA's San Francisco operations office at the time of the nuclear referendum. His nomination has been opposed by a number of groups because his advocacy of nuclear power might make it difficult to be objective about other energy technologies. The GAO report, although finding that ERDA itself perhaps acted improperly, says it found "no evidence that the San Francisco office made a concerted attempt to influence the outcome of the referendum." GAO notes only two instances—a memorandum from the director of the San Francisco public affairs office calling for a "short-term intensive effort in California to counter an all-out attack being waged by antienergy groups" and requests to Lions Clubs and Elks Lodges that ERDA officials be allowed to make speeches on the energy situation—that could be interpreted as attempts to conduct a pronuclear campaign. Otherwise, GAO says, San

Francisco officials simply were carrying out ERDA headquarters programs, which were designed to influence the outcome of the referendum. GAO bases its conclusions on several findings: the memo from the San Francisco public affairs director; that in the month before the vote ERDA significantly increased its exhibit and speech programs in California; and correspondence from ERDA deputy administrator Robert Fri that, according to GAO, clearly indicated an attempt to present pronuclear information in California prior to the referendum. The Department of Energy, which has absorbed ERDA, strongly disagrees with GAO's conclusion. It points out that GAO found no evidence of an increased use of press, radio, and citizen workshops which together represent two thirds of ERDA's information activities. DOE oints out that news releases are the est way to reach a wide number of people and says that the activities noted by GAO reached only 5% of the people in California, clearly indicating no attempt to use the mass media to sway the vote. D

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Dow proceeds with plan for coal power plant

Dow Chemical is moving ahead with plans to assure future electric power supplies for its big chemical complex near Freeport, Tex. (C&EN, Nov. 28, 1977, page 10). Dow is planning a joint venture with Houston Lighting & Power Co. to build and operate two 750,000-kw, power-generating units fueled by lignite (brown coal). The units are expected to be on stream in 1983 and 1984. Dow and Houston Lighting will share equally in the cost of the two power plants, which will be built some 175 miles north of Freeport near Fairfield, Tex., in Freestone County. Nuclear vote allegedly The companies say the project will cost several hundred million dolinfluenced by ERDA lars. Final plans will be developed after Congress' investigative agency, the General Accounting Office, has ac- the boards of directors of both comcused the now-defunct Energy Re- panies approve the project. The search & Development Administra- companies have agreed that Houston tion of attempting to influence Cali- Lighting will be the project manager. fornia voters against a referendum, Each company will own one half of placed on the ballot in June 1976, that the electric power produced by the would have curtailed the use of nu- units. Houston Lighting's share will clear power in the state. ERDA did so, be fed into its power distribution GAO says, by a stepped-up informa- system that provides electricity for a tion program that advocated the ab- 5000 square-mile area on Texas' solute need for nuclear power and upper Gulf Coast. failed to mention its disadvantages. Officials of both companies cite the The referendum was defeated by a project as an aid to reduce their detwo-to-one margin. pendence on natural gas as a fuel The investigation was requested by source. The project, by ensuring an Sen. Henry M. Jackson (D.-Wash.), adequate and economical electric

supply for the future, means jobs and stability for Dow and Houston Lighting, says Paul Oreffice, president of Dow Chemical U.S.A. The agreement will provide the utility's first entry into using lignite, a local energy source, adds George W. Oprea, executive vice president of Houston Lighting. The lignite will come from the Freestone County area where Dow has been acquiring deposits for four years. Dow's analysis of its lignite

Power plant is 175 miles from Freeport complex

Freeport

Feb. 13, 1978 C&EN

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