are distinctive because they possess 

 multiple negative charges. In the 

 oyster shell, it is hypothesized that the 

 negatively charged polyaspartic 

 proteins attract the positively charged 

 calcium crystals, controlling their 

 growth and shape. 



"When we started 

 studying the oysters, 

 we thought those 

 proteins containing 

 polyaspartic acid 

 initiated mineraliza- 

 tion," Wheeler says. 

 "But what we found in 

 our lab tests was that 

 it stopped it. We were 

 more than a bit 

 surprised." 



Wheeler thinks 

 that the protein 

 polymer selectively 

 adsorbs certain 

 surfaces of the 

 calcium crystals as 

 they grow, thereby 

 controlling the shape 

 of the oyster shell. 



After understand- 

 ing that the proteins 

 controlled mineraliza- 

 tion, Wheeler and his 

 colleague Steve Sikes 

 of the University of 

 South Alabama saw 

 commercial applica- 

 tions for their find- 

 ings. The protein 

 could be used to 

 reduce mineral growth 

 in boilers, cooling 

 towers, desalinators, 

 and mining and 

 offshore drilling 

 operations. Currently, 

 industries lose hours 

 of valuable work time and spend 

 millions of dollars preventing crusty 

 mineral accumulation with 

 nonbiodegradable products that are 

 potentially harmful to the environ- 

 ment. 



Polyaspartic acid offers a biode- 

 gradable alternative that controls 



mineral buildup without environmental 

 repercussions. Already, the oil compa- 

 nies are experimenting with the tech- 

 nology to reduce mineralization at 

 offshore well sites. 



However, proteins extracted from 



Herman Lankford 



Polyaspartic acid could make detergents like these more biodegradable 



oyster shells couldn't be the source of 

 the protein. The bivalves were neither 

 cheap nor abundant enough to offer a 

 consistent supply of the protein 

 polymer for industrial use. Instead, 

 Wheeler and his colleagues designed 

 and synthesized a polyaspartic ana- 

 logue that mimicked the oyster protein. 



To manufacture this analogue, 

 they used thermal synthesis, an 

 inexpensive heat process that pro- 

 duced a dry protein powder. 

 Polyaspartic acid can now be manu- 

 factured in quantities sufficient for 

 commercial use. 



Having tackled 

 that problem, 

 Wheeler began 

 looking at other 

 industrial uses for the 

 protein analogue. 

 Again, the protein's 

 chemistry provided 

 an answer. 



Detergent 

 manufacturers add 

 polyanions — 

 compounds that carry 

 multiple negative 

 charges — to their 

 products to attract 

 and hold dirt and 

 mineral particles. The 

 dirt then stays 

 suspended in the 

 wash water "instead 

 of landing back on 

 your clothes or 

 dishes," Wheeler 

 says. 



The negatively 

 charged polyaspartic 

 acid can perform 

 the same function 

 as the commercial 

 polyanions, and it 

 is biodegradable 

 to boot. 



Polyaspartic acid 

 has a carbon-nitrogen 

 backbone that 

 naturally occurring 

 microbes — fungi, 

 bacteria and microor- 

 ganisms — can attack and break down 

 harmlessly. However, the dispersants 

 currently added to detergents don't 

 break down because they have a 

 carbon-carbon backbone that isn't 

 digestible by microbes. Instead, these 

 compounds are released into the 

 environment with every use of the 



16 MAY/JUNE 1997 



