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Cytoskeletal proteins get their own rooms S
the innovative approach that Dogterom layers of silicon monoxide, chromium, tudying cytoskeletal proteins outside and colleagues have taken in designing and gold to build the microchambers. of a cell comes with an extra set of the microchambers. “No one else in the However, the researchers spatially dechallenges: The size and proportions of field is doing this,” says Joe Howard of fined where the cytoskeletal motor protheir natural environment are critical to the Max Planck Institute of Molecular teins could bind, unlike with traditional how they function. To study these molCell Biology and Genetics (Germany). ecules, Marileen Dogterom of the FOM 2-D gold surfaces, by limiting the width “It’s an in vitro, cell-free assay done in a of the gold layer to 150 nm within the Institute for Atomic and Molecular controlled geometry, where you control depressed space. After building the botPhysics (The Netherlands) and her coltom and sides of the microchambers, the the size and space where the reaction leagues have designed new microchamtakes place and control the periphery— investigators created the confined 3-D bers, or “rooms”, with designated provery, very different from tein attachment points that your standard biochemimimic the space inside a cal assay.” living cell (Nano Lett. This research exempli2005, 5, 2350–2354). fies how some biologists Dogterom and colleagues are moving away from are interested in how cytowhole-cell culture and toskeletal polymers generate ward nanotechnology in force. Researchers can use answering certain remethods such as optical search questions, notes tweezers to measure some Viola Vogel of the Swiss of the force properties of Federal Institute of Techisolated microtubules outnology. She says, “We can side cells. However, DogSchematic of a microtubule as it slides along a layer of kinesin molecules. now provide these engiterom points out that “a Expanded view is a close-up of a microchamber on a glass slide. neering tools to control cell is a confined geometry parameters that were not controlled in rooms by placing a clear glass slide and when microtubules or cytoskeletal the past.” across the top of the microchambers. polymers organize or generate force, The investigators see the work as a Dogterom and colleagues connected they do this in a confined space.” She preliminary step toward their ultimate the cytoskeletal motor protein, kinesin, and her colleagues wanted to create a research goals. “The first step in this to the gold layer in a series of steps. new in vitro environment to study the forces generated by organized cytoskele- Thiol chemistry was used to attach a bi- paper shows that we can not only make a confined chamber but we can also put otinylated self-assembled monolayer to tal polymers and motor proteins in a proteins that are active, specifically mothe gold, and streptavidin was bound to cell. These microchambers mimicked the monolayer. Biotinylated kinesin pro- tor proteins in this case, on the edge of the approximate size and shape of the these chambers,” Dogterom says. She inside of a living cell and allowed the re- teins were then attached to the streptaand her colleagues are now working to searchers to limit the number of protein vidin. To demonstrate that cytoskeletal minimize imperfections in their micromotor proteins could function in this interactions to just the ones between chambers by building the layers first system, the investigators showed that the cytoskeletal polymers and motor fluorescently labeled microtubules could and then etching into those layers to proteins. create the microchambers. Eventually, attach to the kinesin-covered gold layer The researchers used optical lithograthey would like to develop techniques and crawl around the periphery of the phy to construct microchambers with a to selectively place different proteins microchamber. gold layer around the periphery. They throughout such defined microchamAlthough experts note that the techtransformed a glass coverslip into a series bers. a nique is still early in its development of defined microchambers
