and coworkers A. R. Tavarozzi, of Union Carbide, and G. J. Wagerson, of PPG Industries, currently recom­mend Azdel for auto interiors and for under the hood, mainly because of a necessity for hand finishing sur­faces before painting. But in the fu­ture, Mr. Hofer says, the company anticipates use of Azdel for painted exterior body panels.

Unfilled thermoplastics such as ac-rylonitrile-butadiene-styrene are also in contention for auto body exterior panels. Several plastics makers, in­cluding Marbon division of Borg-Warner and Uniroyal, currently are promoting such materials.

Another development bringing plas­tic auto bodies closer to reality is Vibrin-Mat sheet molding compound (originally developed by Uniroyal but the rights for which have been ac­quired by Marco Chemical Division of W. R. Grace & Co.). James P. Walton, Marco's manager of Vibrin products, describes the material as a low-shrinkage glass-fiber-polyester composite in sheet form. A smooth, fiber pattern-free surface is obtained "out of mold," thus eliminating much of the costly sanding and surface prep­aration previously required when working with glass-reinforced poly­ester resin compounds.

ALUMINUM: More Used in Autos The average 1969 model passenger car will contain more aluminum than in any previous year-73.3 pounds per car, according to Aluminum Co. of America's 14th annual survey of the U.S. auto industry. This will amount to a total of 765 million pounds of the lustrous, lightweight metal in U.S. autos, Alcoa says, another all-time record. The Alcoa survey is projected on an output of 8.4 million cars during the current

model year, the same as in the 1968 model run.

Highest per-car net use for alumi­num before the 1969 model estimate was 72.4 pounds in 1964 models. In 1968, net use per car was a little less than in 1964-72.2 pounds, but total aluminum consumption in autos last year was 730 million pounds, higher than in any previous year.

These increases in automotive use come despite a reduction of bright exterior and interior trim resulting from federal safety regulations and styling changes, notes Robert E. Con-lee, Alcoa's manager of transportation industry sales. Although 1969 mod­els generally have less trim than re­cent-year models, Mr. Conlee says, aluminum comprises a greater por­tion of the total trim on many makes of cars. Grilles, moldings, rear deck plates, bezels, scuff plates, and similar items constitute a huge market, he adds. Extrusions offer styling features which designers are using to good advantage. He also indicates that Alcoa anticipates extensive use of alu­minum for windshields and rear win­dow reveal moldings, items conven­tionally made of stainless steel.

The Alcoa survey attributes the higher average per-car use of alu­minum to increasing growth in instal­lation of certain optional equipment, combined with increased aluminum content in many of these items. Cer­tainly three of the most influential factors in the metal's growth in auto use, Mr. Conlee says, are the high rate of factory installation of air con­ditioners, the nearly universal use of automatic transmissions, and the big­ger and higher displacement engines being installed.

The survey indicates that an antic­ipated upswing in the number of fac­tory-installed air conditioners alone (estimated at 50% for 1969 models) will account for an increase of 10 mil­lion pounds of aluminum.

ENZYMES: First Total Synthesis The first total laboratory synthesis of an enzyme has been accomplished in­dependently by two teams of chem­ists—one at Rockefeller University and the other at Merck Sharp & Dohme Research Laboratories of Merck & Co. Using two entirely different techniques, the teams have synthesized the enzyme ribonuclease (RNase). Both groups have published results of their work in the Jan. 15 issue of the Journal of the American Chemi­cal Society.

The synthesis opens a path to more complete knowledge of RNase's struc­ture and mechanism of action. It also shows that it's possible to attack the synthesis of even larger enzymes with the two methods.

Dr. Robert B. Merrifield and Dr. Bernd Gutte comprised the Rockefel­ler team. The Merck scientists were led by Dr. Robert G. Denkewalter and Dr. Ralph F. Hirschmann. The prod­ucts prepared by both groups show the same kind of enzymic activity as that present in naturally occurring RNase. They split ribonucleic acid (RNA) but have no effect on deoxy­ribonucleic acid (DNA).

The Rockefeller team's approach to the synthesis of RNase was the solid-phase peptide synthesis technique de­veloped several years ago by Dr. Mer­rifield. In the technique, an insoluble solid support, polystyrene, acts as an anchor for the peptide chain during the synthesis. The first amino acid is firmly bound to a small polystyrene bead and each of the other 123 amino acids is then added one at a time in a stepwise manner. The process is au­tomated by a machine so that the 369 chemical reactions and 11,931 steps of the machine which were required for the synthesis could be accom­plished in a few weeks of continuous operation.

The Merck team's synthetic ap­proach exploited the well-known prop­erty of RNase that if the first 20 of the enzyme's 124 amino acids are re­moved, the enzymic activity will cease, but when both of these parts are re-combined full enzymic activity is re­generated. One portion of the en­zyme, a 104 amino acid fragment, is called S-protein; the other, a 20 amino acid fragment, is called S-peptide.

The Merck scientists prepared a large number of small peptides, or fragments, of RNase. They then as­sembled the pieces into the large S-protein, which had no enzymic activ­ity. In the crucial final experiment, the research workers showed that the S-protein could combine with the small S-peptide fragment, producing the active enzyme.

JAN. 20, 1969 C&EN 15

Use of aluminum in passenger cars will reach record this year

Pounds per car average-finished part weight

Source: Aluminum Company of America * Estimated

50.7 54.39

62.7 66.5 ι

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70 72.4 69.1 70 71 72.2 73.3*

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