NEWS OF THE WEEK NANOSCIENCE
DENDRIMER TRAP ΤΓ-CONJUGATED Third-generation polylpropylene imine) dendrimer is functionalized with oligofp-phenylenevinylene).
Two light beams are used to manipulate fluorescent aggregates
u
SING AN OPTICAL TWEEZER
consisting of two light beams, chemists in Europe have constructed novel supramol-
ecular assemblies of dendrimers functionalized with an outer shell of fluorescent semiconducting groups.
The researchers first prepare spherical aggregates of the den drimers in an acidic solution, and then use a highly focused infrared beam to trap the vesi cles near the focal point of the beam. The vesi cles, which have an av erage diameter of 300 nm, jump to a second optical trap a few mi crometers away when the first trap is switched off and the second is switched on {Chem. Commun.,2002,1264]. The team includes chemistry professor Frans C. De Schryver and postdoctoral re searcher Johan Hofkens at Catholic Uni versity of Leuven, in Belgium, and research fellowAlbertusPHJ. Schenning and organic chemistry professor E. W. (Bert) Meijer at Eindhoven University ofTechnology in the Netherlands. They used transmission electron microscopy and confocal scanning fluorescence microscopy meas
TRANSITIONS
Special Election Set For ACS Board t its June meeting last week in Elkridge, Md., the ACS Board of Directors appointed Joan E. Shields, professor of chemistry, Long Island University, C. W. Post campus (Brookville, N.Y.), to the Governing Board for Publishing (GBP), the body that oversees the operations of the Publications Division and Chemical Abstracts Service. Shields will serve a three-year term beginning July 1. To accept the appointment, Shields will resign from the ACS Board as a director-at-large effective June 30. Shields served on the board from 1989 to 1991 and from 1995 to the present; she was chair from 1996 to 1998. "I've enjoyed my tenure on the board and am still actively involved in numerous ACS governance com
A
8
C&EN
/JUNE
17,
200?
urements to confirm the globular nature of the vesicles and visual ize the switching process. The paper presents an inter esting advance in micromanipula tion, says François Ν. Diederich, professor of organic chemistry at the Swiss Federal Institute of Technology (ΕΤΗ), Zurich. "Ma nipulation by optical tweezing is a promising new tool for gaining control over large supramolecular assemblies," he remarks. Hofkens says that, under acidic conditions, "the dendrimer be comes a giant amphiphilic mole cule by changing its conformation and then forms vesicles like other amphiphilic molecules. The size ofthe aggregates strongly depends on the p H ofthe aqueous solution. "The optical trap immobilizes micrometer- and submicrometersize particles against gravitation and Brownian motion," he adds. "We used a dual trap to demon strate the attractive interaction be tween the vesicles and to form as semblies with novel architectures." The work shows the synergy that can be found when two re search groups with different back grounds join forces, Meijer notes. "On the one hand, it makes use of a well-defined molecule that selfassembles into a supramolecular architecture, while on the other hand, advanced optical tech niques are used that manipulate these architectures," he says.— MICHAEL FREEMANTLE
mittees, but I couldn't give up this wonderful opportunity to serve the society in a different capacity," she says. "I am looking forward to the challenges that come with the GBP in this electronic era. Serving as chair of the Joint Board-Council Committee on Publica tions has given me further insights into the task ahead." The Committee on Nominations & Elections will conduct a special election among ACS councilors in accordance with ACS bylaws to fill Shields's remaining one-and-a-half-year term. C&EN will publish the slate of candidates and a timeline in a subsequent issue. The board also reappointed Kathleen Case, publisher, Ameri can Association for Cancer Research, and Mary L Good, dean, Donaghey College of Information Science & Systems Engineer ing, University of Arkansas, Little Rock, to the GBP for four-year terms beginning July 1.-MADELEINE JACOBS
HTTP://PUBS.ACS.ORG/CEN
