Science Concentrates NUCLEIC ACIDS
Genetic engineering through click chemistry Method gets nucleic acids into cells by first modifying cell surfaces Gene therapy and many types of biological research use a process called transfection to efficiently deliver nucleic acids into cells. Many transfection approaches for mammalian cells rely on electrostatics: Cationic reagents bind to negatively charged nucleic acids and form ionic complexes that cells can pull inside via a mechanism known as endocytosis. The concentration of positive charge in the reagents can kill cells, however, and the process works poorly for some types of cells. Now researchers report a click-chemistry-based transfection technique, dubbed SnapFect, which relies on bio-orthogonal molecules—a class of chemically reactive compounds that don’t interfere with biological systems (ACS Cent. Sci. 2017, DOI: 10.1021/acscentsci.7b00132). The team, led by Muhammad N. Yousaf of York University, designed nanoparticle liposomes carrying a ketone ligand.
When added to cultured cells, they fuse into the cell membrane within seconds, leaving the ligand exposed on the cells’ surfaces. Meanwhile, the researchers created lipid complexes decorated with oxyamines that hold nucleic acids. When these complexes were added to the cells, their oxyamines reacted with the cell surface ketones. The cells then pulled the resulting membrane-bound nucleic acid complex inside via endocytosis, and the nucleic acid could be expressed by the cells’ machinery. Yousaf’s team compared the performance of two widely used transfection kits—Lipofectamine (Life Technologies) and ViaFect (Promega)—with SnapFect, which is now for sale via Yousaf ’s company, OrganoLinX. SnapFect transfected cells with a 68% overall efficiency, while the other two did so with 19% and 29% efficiency, respectively.
SnapFect uses click chemistry to bind oxyamine-labeled nucleic acid parcels to ketone-decorated cell surfaces. The cells then pull the nucleic acids inside (not shown). “It’s an interesting step forward,” says James H. Eberwine, a molecular neurobiologist at the University of Pennsylvania. Eberwine adds that researchers often optimize transfection techniques for their particular applications and achieve much higher efficiencies than those noted in this study. “I would certainly try it,” he says, to see how the efficiency stacks up in a real-world context.—ALLA KATSNELSON,
special to C&EN
MOLECULAR MACHINES
Tiny machine synchronizes the motions of its two moving parts Gearing up to make even more complex molecular machines, chemists at the University of Groningen have created a molecular motor coupled to a rotor. The motor turns the attached rotor such that the two components’ motions are synchronized, just like that of machines we encounter in everyday life (Science 2017, DOI: 10.1126/science. aam8808). “This is fundamental research about how to control motion at the molecular level and how then to use it to synchronize motion and amplify motion,”
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C&EN | CEN.ACS.ORG | JUNE 5, 2017
says Ben L. Feringa, who led the Groningen team. In a commentary that accompanies the paper, University of Bologna chemists and molecular machine makers Massimo Baroncini and Alberto Credi note that the motor-rotor combo “takes an important step forward toward more complex mechanical functions with artificial nanoscale devices.” The unidirectional motor consists of a fluorenyl unit attached to an indanyl group via a double bond. The system’s naphthyl rotor is covalently attached to the indanyl half of the motor. When illuminated,
the motor’s double bond isomerizes, setting the system into motion. As the motor turns, the naphthyl rotor paddle slides alongside the fluorenyl unit so that the rotor is always facing the motor with the same side—a feat the group accomplished with a complex stereochemical design. Both nuclear magnetic resonance and circular dichroism spectroscopy confirmed this synchronized motion. It was a delicate balance to achieve the desired movement, Feringa notes. “We had to induce motion, we had to couple motion, and we had to prevent free rotation of the rotor; otherwise we could not have synchronized rotation,” he says. Next, Feringa’s group would like to create machines that can amplify the molecular machines’ motion to larger movements or transmit motion over longer distances.—BETHANY HALFORD
CREDIT: ADAPTED FROM SCIENCE (STRUCTURE); ACS CENT. SCI. (REACTION)
Molecular motor turns rotor
