news of the week

One solution to the problem now has been devised by Chad A. Mirkin, an associ­ate professor of chemistry, and graduate students Jin Zhu and Feng Xu at North­western University, Evanston, Π1., and Su­san J. Schofer, an undergraduate student at Brown University [f. Am. Chem. Soc., 119, 235(1997)].

Their solution lies in metal nanoparti-cles. Earlier work such as that by the group of Michael J. Natan, an assistant professor of chemistry at Pennsylvania State University, University Park, showed that assemblies of nanoparticles of metals like gold and silver can enhance the Ra­man signals of bulk organic films depos­ited on various substrates.

Building on those results, Mirkin and coworkers have developed a technique compatible with the high reactivity of high-temperature superconductors. Using gold as a Raman-signal enhancer and a commercially available instrument, they obtained the Raman spectrum of a mono­layer of 4-aminopyridine on the surface of the cuprate superconductor YBa2Cu307_§.

"Usually, getting information regarding the surface structure of high-temperature superconductors requires heroic efforts," says Natan, an expert in colloid chemistry and Raman spectroscopy. The experiment by Mirkin and coworkers is simple and straightforward, rapidly giving insight into the structure of the organic film, he adds.

Mirkin's research provides, for the first time, information about the "handshaking mechanism" between a monolayer and a complex cuprate superconductor surface, notes John T. McDevitt, associate profes­sor of chemistry at the University of Texas, Austin. One of McDevitts areas of exper­tise is chemical modification of high-temperature superconductors.

The Raman spectrum indicates a strong chemical interaction between the amino group of 4-aminopyridine and the YBa2Cu307_5 substrate, Mirkin says. This re-

(From left) Zhu, Mirkin, and Xu are three-fourths of team that devised spectroscopic technique.

suit directly confirms what re­searchers have assumed from previous studies: Molecules with amino groups reach out to the superconductor surface through those groups. This finding is corroborated by elec­trochemical data indicating that pyridine groups do not chemically interact with the surface of YBa2Cu307_5.

Although the superconductor coun­terpart in this "handshake" and other structural details—such as the degree of order of the adsorbed molecules—have not yet been determined, McDevitt says the Raman method should allow a "more complete structural analysis of supercon­ductor-localized monolayer assemblies."

The simplicity of the approach is very appealing, comments Natan. The monolay­er is formed on the substrate by immersing the substrate in a solution of 4-aminopyri­dine in acetonitrile. Then the monolayer is exposed to gold nanoparticles dispersed in toluene and rinsed several times with pen-tane. The Raman spectrum obtained after such treatment of the monolayer compares very well with that of pure solid 4-amino­pyridine.

Maureen Rouhi

Monsanto to buy seed corn producer, makes agchem discovery deal Monsanto announced three deals last week—two in seed production and mar­keting and one in agrochemicals—that will expand its technology base and pro­vide commercialization routes for its bio­technology developments.

In the two largest deals, Monsanto will spend a total of up to $1.02 billion to acquire Holden's Foundation Seeds and two Corn States businesses. Based in Williamsburg, Iowa, Holden's is a leading producer of seed corn used by retail companies to create hybrid seeds for farmers. Des Moines-based Corn States Hybrid Service and Corn States Interna­tional are the exclusive worldwide mar­keting and sales representatives for Hold­en's products. Late last month, Monsanto received final U.S. regulatory approval to

market its genetically engineered insect-resistant corn.

The deals are still under negotiation, says a Monsanto spokeswoman, but about $945 million of the acquisition price will be for Holden's. This is a tremendously high premium for a privately held compa­ny that has annual sales of about $45 mil­lion. However, what Monsanto will gain immediately, suggest chemical industry an­alysts, is a worldwide marketing and distri­bution infrastructure for its biotechnology products.

In addition, says Paul Raman, an analyst with investment banker PaineWebber in New York City, "Monsanto should be able to increase its [seed corn] market share to about 40% from the about 7 to 10%" share it would have had without the acquisition.

In a separate deal aimed at agrochemi­cals, Monsanto signed an agreement with combinatorial chemistry company ArQule. Under the five-year agreement, the Med-ford, Mass.-based company will provide ar­rays of compounds for use in discovering and developing crop protection products. ArQule is to receive $12 million from Monsanto for delivering the initial arrays. Additional milestone and royalty payments are possible if compounds progress through field trials and become commer­cial products.

Combinatorial chemistry is most often directed toward drug discovery, so part­nerships involving small combinatorial chemistry firms such as ArQule and major agrochemical producers are rare. But the same principles can be applied in creating agrochemicals. like drug candidates, com­pounds can be rapidly screened and iden­tified for pesticidal activity. With Monsan-

Shapiro: deals will speed seeds to market

6 JANUARY 13, 1997 C&EN

to, the target chemicals will include herbi­cides, fungicides, and insecticides.

In the past 18 months, Monsanto has spent more than $400 million to expand its reach in agricultural biotechnology-acquiring stakes in Calgene, Ecogen, DeKalb Genetics, and all of Agracetus— fueling rumors, since proven true, that the company would split into a chemical company and a life sciences company (C&EN, Dec. 16, 1996, page 9).

Holden's basic seed technology will be an important building block in Monsanto's agricultural biotechnology business, pro­viding a delivery mechanism for getting genetically engineered plant traits into commercial seed products. "These acqui­sitions mean the latest technological ad­vances will be made available to the great­est possible number of seed companies of all sizes with unparalleled speed," says Robert B. Shapiro, Monsanto chairman and chief executive officer.

Monsanto's investments in seed mar­keters are designed to allow it to capital­ize on the billions of dollars it has invest­ed in plant biotechnology R&D over the past 20 years.

Ann Thayer

Investors push for Rexene sale Two Wall Street investors are waging a battle to toss out the current board of di­rectors of Dallas-based plastics and film maker Rexene. They want to install four new directors whose mission will be to sell Rexene for at least $16 per share or $300 million.

The investors are miffed because they say Rexene's board failed to adequately ex­plore at least three offers to purchase the company made last year by Salt Lake City-based plastics maker Huntsman Corp. In July, Huntsman offered $14 per share (C&EN, Jury 29, 1996, page 6); it made an­other offer of $15 in August (C&EN, Aug. 12,1996, page 9); and it made a third offer of $16 late in October. The last offer rep­resented a more than 70% premium over the $925-per-share price at which Rexene traded before Huntsman's first offer.

The investors' proposed directors "have no experience in managing a spe­cialized polymer company like Rexene," warns Rexene's chairman and chief ex­ecutive officer, Andrew J. Smith, in a let­ter to shareholders. If they secure con­trol of Rexene and cannot sell the com­pany at $16 per share, the proposed

directors would be "forced to manage the company, or sell the company at an unacceptably low price," he says.

However, in reaction to the two in­vestors' call for the sale of the company, Rexene management now says it would consider selling the company for $16 per share, if it could close a deal within 60 days. At press time, Rexene, which has annual sales of more than $600 million, traded at $ 14 per share on the New York Stock Exchange.

The investors, Wyser-Pratte Manage­ment and Spear, Leads & Kellogg, both of New York City, together own about 10% of Rexene's shares. They have just mailed a solicitation statement asking sharehold­ers to approve a special meeting of share­holders. If a majority approves the request, the investors—who plan to ask Smith to remain as a fifth director and CEO—hope that the shareholders will replace the cur­rent board with their nominees.

Those nominees are Jonathan R Macey, a professor at Cornell Law School; Robert C. Mauch, former president and CEO of pro­pane distributor AmeriGas; Lawrence C. McQuade, former executive vice president of W.R. Grace; and James S. Pasman Jr., former chairman and CEO of KaiserTech, an aluminum and chemical concern.

Of the current imbroglio, a spokesman for Huntsman says, "We are aware of the proxy battle, but we have nothing to do with it." The spokesman added that under advice of counsel, he could make no com­ment about Huntsman's interest in acquir­ing Rexene. If Huntsman is still interested in acquiring Rexene, it may not want to re-create the hostile atmosphere that exist­ed between the two companies last year.

Marc Reisch

Methylene chloride exposure sharply limited The Occupational Safety & Health Admin­istration has issued a final standard limiting worker exposure to methylene chloride. The new eight-hour time-weighted per­missible exposure limit (PEL) is 25 ppm. The previous PEL was 500 ppm.

According to OSHA, about 238,000 workers in more than 92,000 establish­ments are exposed to methylene chlo­ride every year. The compound is used for paint stripping and in aerosols, plas­tics manufacture, metal-degreasing oper­ations, urethane foam production, and pharmaceuticals. It is not flammable and does not contribute significantly either to

air pollution or depletion of stratospher­ic ozone.

OSHA has set the new standard low be­cause of indications that methylene chlo­ride is carcinogenic. Laboratory animal studies show that it can cause cancers in rats and mice, and some epidemiologic data indicate it may cause cancer in ex­posed workers. Based on OSHA's risk as­sessment from these data, the agency esti­mates that exposure at 25 ppm will result in 3.6 excess cancer deaths per 1,000 workers exposed to the chemical.

These risks are vigorously denied by the Halogenated Solvents Industry Alliance (HSIA), a Washington, D.C.-based trade group that represents manufacturers and users of methylene chloride. OSHA's re­view of the toxicity of methylene chloride "likely will be inconsistent with the out­come of an ongoing recharacterization of the solvent by the Environmental Protec­tion Agency and other federal agencies," predicts HSIA Executive Director Peter E. Voytek. He believes this ongoing federal review will show that it is safe to use the chemical at the industry-recommended ex­posure level of 50 ppm.

OSHA disagrees. Adam M. Finkel, direc­tor of OSHA's health standards programs, says industry is incorrect in believing OSHA has not considered the animal and epidemiologic data properly. "OSHA has considered the metabolic differences be­tween mice and humans and did consider the data submitted to us by HSIA," Finkel says. Those data did not convince the agency to set the PEL at 50 ppm.

HSIA is also concerned that it will be impossible for small businesses to meet the new, tougher standard. "For many smaller users, if OSHA sticks with the 25 ppm, they will go out of business," ac­cording to Voytek.

OSHA believes its standard is both technologically and economically feasi­ble. Compliance costs are estimated to be $101 million annually, or about $424 per exposed worker. Firms that substi­tute other chemicals for methylene chlo­ride could avoid compliance costs entire­ly, OSHA points out.

At press time, the methylene chloride standard had not yet been published in the Federal Register, but it will go into effect 90 days after publication. It includes re­quirements for exposure monitoring, med­ical surveillance, and respiratory protec­tion. Small businesses get a few breaks on some compliance deadlines and medical tests, but will have to meet the same expo­sure limit as all other affected operations.

Dave Hanson

JANUARY 13, 1997 C&EN 7

according to OSHA, about 238,000