-SCIENCE & TECHNOLOGY-
CONCENTRATES Mass spec pins down abnormal disulfide bonds in rhodopsin
I ment about the underlying j ldnericsandmechanism.Using an electrochemical quartscrystal microbalance proceRetinitis pigmentosa, an inherited disease that leads to pro- dure, graduate student Matgressive loss ofvision, has been linked to mutations of the visual I thewL Jeffrey and chemistry pigment rhodopsin. In the 1990s, H. GobindKhorana, emeritus | professor Ian M, Ritchie at professor ofchemistry and biology at MITJ and coworkers showed | Murdoch University in Austhat mutations in a certain portion of rhodopsin (a transmem- | tralia have studied gold leachbrane protein) cause it to misfold so that it doesn't bind 11-dr- j ing as a function of solution retinal. That chromophorenoonattfbinds deepwithtarhodopsirfs purityffiElectrochem.Sac, 148, membrane-spanning helices, isomerizing to the all-trans config- D29 (2001)}. They find that uration when light strikes the molecafc.That event triggers abio- when ultrapure reagents are chemical cascade that the brain interprets as sight. The researchers used, the reaction is immeadetermined indirectly that the misfoldingis due to the formation surably slow By contrast, when of a disulfide bond that differs from what's found in normal I the reaction is carried out in rhodopsin. Now, Khorana, MITpostdocJudith Klein-Seethara- | solutions prepared from anaman, andJohnHwaat DartmouthMedical School have developed I lyticalreagent-gradechemicals a direct mass spectrometric method for identifying such abnor- | tWtypicaKycontainpart-permal disulfide bonds in membrane proteins {Proc. Natl. Acad. Scij biffionlevels ofimpurities such USA, 98, 4872 (2001)}. They find that other mutations in | as lead, gold leaches at apprerhodopsin result in the same abnormal disulfide bond. The results I ciable rates. Lead and other establish that thepackingof rhodopsirfs seven helices within the I metsls are known to catalyze membrane is coupled to foldingin the domain outside the mem- | gold dissolution. Accordingly, | the researchers attribute varibrane where the abnormal disulfide bond occurs. ations in reported reaction rates to variations in impurity ruthenium catalyst supported levels and propose a model in ongraphite.Tlie stability ofthe which the presence of lead boron nitride-supported cata-^ accelerates dissolution of a lyst approaches thatofironcat- chainlike film of AuCN— the alystsusedinindustry whereas rate-limiting step. Unprecedented catalytic the graphite-supported rutheactivity in ammonia synthesis nium catalyst is thermodyhas been achieved using a bar- namically unstable under ium-promoted boron nitride- industrial ammonia synthesis supported ruthenium catalyst. conditions." He adds that GlausJ. HJacobsen, senior sci- boron nitride is a chemically entist at Haldor Topstfe inert material with high temResearch Laboratories, Lyngby perature resistance and that it Chemists have Invented a Denmark, prepared the cata- can be preparedwithhigh sur- new way to link the disparate lyst fromboronnitride crystals face areas. It could prove to be chemical components that and aqueous solutions ofruthe- aninterestingsiipportforother yield high-performance motor nium nitroso nitrate and bar- catalyst materials, he suggests. oil additives [Macromokcutes, ium hydroxide |J. CdtaL, 200, 34,2766 (2001)J.The trick is 1 (2001), also published as to combine an ethylene/1IDEALFirst article, http:// butene copolymer chain, wwwideaKbrarycom/links/toc/ which is compatible with jcat]. He measured its activity motor oil, with a polyethylin a 3:1 mixture of hydrogen One hundred years of using eneimine chain. The amino and nitrogen over a range of a basic chemistry process groups chelate oxidized iron temperatures and pressures, commercially ought to be from corrosion to prevent findingit to be "the most active enough time to work out the engine damage. Jacob L ammonia synthesis catalyst method's fundamental details. Emert, dispersants technolreported so far/'Jacobsen tells But when it comes to leaching ogy manager at ExxonMobil C&EN. "It is stable even at gold from its ores using alka- Chemical; organic chemistry very high pressures and tem- line cyanide solutions (the cen- professor Henry K. HallJr. at peratures, which is not the case tury-old MacArthur-Forrest the University of Arizona; and for the current commercial method), there is little agree- coworkers treat the copoly- I
Boron nitride boosts catalyst activity
New route to motor oil additives
Dirty way to go for the gold
HTTP://PUBS.ACS.ORG/CEN
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merwithboron trifluoride, carbon monoxide, and 2,4dichlorophenol to fictionalize the unsaturated end of the copolymer as a phenyl carbqxylate ester. Reaction ofthat with a polyethyleneimine of average molecular weight
greater than 230 provides the polyamine end group ofthe oil additive.
'Green'paint to be tested The Pentagon announced last week that 20,000 gal of an environmentally friendly paint developed by scientists at the University of Southern Mississippi will be used to paint one Vedge," or wing, of the Pentagon as part of a renovation project. The latex paint, developed by Shelby E Thames, a professor of polymer science, and his coworkers, incorporates a castor oil acrylated monomer (CAM) with the other comoriomers, which are petroleum by-products, in the polymer particles. The CAM acts as apksticizing agent and makes the paint flow without any of the organic cosolvents that are typically used. The paint releases a much smaller amount of volatile organic coriipounds than other latexpaints^as little as 3 g per L compared to 200-400 g per L—and does not have the common "fresh paint odor." When the paint is exposed to air, it undergoes an oxidation reaction that causes cross4inking between carboncarbon double bonds on the fetty acid side chains that are part of the CAM. As a result, the CAM-based paint is more scrub-resistant than other commercial latex paints* C & E N / A P R I L 3 0 , 2001
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