The functions of regulatory enzymes are essential to modulating cellular pathways. Here, we report a tweezer-like DNA nanodevice to actuate the activity of an enzyme/cofactor pair. A dehydrogenase and NAD þ cofactor are attached to different arms of the DNA tweezer structure and actuation of enzymatic function is achieved by switching the tweezers between open and closed states. The enzyme/cofactor pair is spatially separated in the open state with inhibited enzyme function, whereas in the closed state, enzyme is activated by the close proximity of the two molecules. The conformational state of the DNA tweezer is controlled by the addition of specific oligonucleotides that serve as the thermodynamic driver (fuel) to trigger the change. Using this approach, several cycles of externally controlled enzyme inhibition and activation are successfully demonstrated. This principle of responsive enzyme nanodevices may be used to regulate other types of enzymes and to introduce feedback or feed-forward control loops.

Optical detection of molecular targets typically requires immobilization, separation, or chemical or enzymatic processing. An important exception is aptamers that allow optical detection in solution based on conformational changes. This method, however, requires the laborious selection of aptamers with high target specificity and affinity, and the ability to undergo the required conformational changes. Here we report on an alternative generic scheme for detecting small molecules and proteins in solution based on a shift in the equilibrium of DNA-based strand displacement competition reaction. The shift occurs upon binding of a protein, for example, an antibody to its target. We demonstrate nanomolar detection of small molecules such as biotin, digoxigenin, vitamin D, and folate, in buffer and in plasma. The method is flexible, and we also show nanomolar detection of the respective antibodies or protein targets of these molecules. The detection scheme provides a generic alternative to aptamers for detection of analytes.

DNA-directed synthesis of encoded combinatorial libraries of small organic compounds most often involves transfer of organic building blocks from one DNA strand to another. This requires cleavable linkers to enable cleavage of the link to the original DNA strand from which the building block is transferred. Relatively few cleavable linkers are available for DNA-directed synthesis and most often they leave an amino group at the organic molecule. Here we have extended the application of aryltriazenes as traceless linkers for DNA-directed synthesis. After reaction of one building block with a building block at another DNA strand the triazene linker is cleaved and reduced with hypophosphorous acid in high yield to leave the aryl group with a hydrogen in place of the triazene i.e. without a functional group trace. It was also demonstrated that alternatively the triazene could be converted to an azide, which was used in a cycloaddition reaction. The linker is generally stable at pH > 7 and could be stored for several months in a freezer without significant degradation.

An ew and facile methodf or the preparation of single-walled carbon nanotubes( SWCNTs) decorated with Cu nanoparticles (CuNPs)f ormed on ad ouble-stranded DNAt emplate in aqueous solution has been developed.Aspecially designed synthetic DNAsequence,containing asingle-stranded domain for the dispersion of carbon nanotubes and double-strandeddomainsfor the selective growth of CuNPs,w as utilized. Thef inal SWCNT/CuNP hybrids were characterized using fluorescence spectroscopy and transmission electron microscopy.T he analyses clearly demonstrated the selective formation of uniform CuNPs on the carbon nanotubescaffold.Introduction. -Novel 1D single-walled carbon nanotubes (SWCNTs)/nanoparticle hybrid materials,i nw hich SWCNTs are oftenu sed as scaffolds for the assemblyo f nanoparticles,a re of great importance due to their considerableh ardness and toughness [1].S WCNT/metal nanoparticle hybrids, especially transition metal nanoparticle-decoratedS WCNTs,h ave aroused great interest because of their vast applications in sensor devices [2], photoelectrochemicalc ells [3], as catalytics upporters [4], and in surface-enhanced Raman spectroscopy [5].Controlled decoration of SWCNTsw ith metal nanoparticles modifies their electronic structure resulting in better electroanalytical performance due to the synergetic effect of the two materials compared to bare metal nanoparticles [6], making important not only fundamental studies of the interactionsb etween the carbon matrix and the metallic nanoparticles, but also the aspects of their broad potential applications.Currently,v arious methods are being explored, generallyb eing divided into covalent or noncovalent attachment of certain metal nanoparticles onto carbon nanotubes [7 -12].Covalent deposition requires prefunctionalization of the nanotubes by modifying their surface.Inmany cases,itinvolves acid treatment to create COOH, C¼O, or OH groups for subsequent anchoring of metal nanoparticles [8]. Theh arsh acidic treatment of SWCNTs may introduce many extensive defects in the sidewall, thusconsiderablyperturbing the mechanical and electronic performance of the tubes. On the other hand, the noncovalentapproach maintains the properties of the nanotube, the carbon scaffold being minimally perturbed by utilizing functional compounds,such as organic molecules [9], polyelectrolytes [10], and single-stranded DNA( ssDNA)