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Mingxuan Gao, Lin Yang, Yi Zheng, Xiaoxi Yang, Hongyan Zou, Jing Han, Zexi Liu, Yuanfang Li, Cheng Zhi Huang
Surface functionalization is an essential prerequisite for wide and specific applications of nanoparticles such as photoluminescent (PL) carbon quantum dots (CQDs), but still remains as a major challenge. In this report, alkynylated CQDs, which were prepared at first from carboxyl-rich CQDs through amidation with propargylamine in the presence of 1,1'-carbonyldiimidazole, were efficiently modified with azido molecular beacon DNA through copper(I)-catalyzed alkyne-azide cycloaddition reaction (CuAAC). As the proof of concept, the DNA-modified CQDs was then bonded with 5-nm gold nanoparticles (AuNPs) through gold-sulfur bond...
December 3, 2016: Chemistry: a European Journal
Adegoke Ojewole, Anna Lowegard, Pablo Gainza, Stephanie M Reeve, Ivelin Georgiev, Amy C Anderson, Bruce R Donald
Drug resistance in protein targets is an increasingly common phenomenon that reduces the efficacy of both existing and new antibiotics. However, knowledge of future resistance mutations during pre-clinical phases of drug development would enable the design of novel antibiotics that are robust against not only known resistant mutants, but also against those that have not yet been clinically observed. Computational structure-based protein design (CSPD) is a transformative field that enables the prediction of protein sequences with desired biochemical properties such as binding affinity and specificity to a target...
2017: Methods in Molecular Biology
Malek Boukallaba, Boutheïna Kerkeni, Christine Lepetit, Dorothée Berthomieu
A quantum chemistry study of mononuclear metal coordination with four 4-methylimidazole ligands (4-MeIm) was investigated. The four complexes [Cu(4-MeIm)4](2+), [Cu(4-MeIm)4, H2O](2+), [Zn(4-MeIm)4](2+) and [Zn(4-MeIm)4, H2O](2+) were studied with particular attention to the Nπ or Nτ possible coordinations of the 4-MeIm ring with the metals, using different DFT methods. The results suggest that the Nτ coordination of 4-MeIm ring to Zn(II) or Cu(II) is more favorable whatever the level of calculation. In contrast, the addition of one water molecule in the first coordination sphere of the metal ions provides five-coordinated complexes showing no Nπ or Nτ preferences...
December 2016: Journal of Molecular Modeling
Dinh Bao Nguyen, Thanh Danh Nguyen, Sangsoo Kim, Sang-Woo Joo
Spectral differences between cytosine (Cyt) and 5-methylcytosine (5MC) were investigated by means of Raman spectroscopy with a combination of density functional theory (DFT) calculations. Surface-enhanced Raman scattering (SERS) revealed discriminating peaks of 5MC from those of Cyt upon adsorption on gold nanoparticles (AuNPs). Among the notable features, the multiple bands between 850 and 700cm(-1) for the ring-breathing modes of 5MC and Cyt could be correlated well with the simulated spectra based on the DFT calculations of the adsorbates on the gold cluster atoms...
November 9, 2016: Spectrochimica Acta. Part A, Molecular and Biomolecular Spectroscopy
Jesse D Marshall, Jin Zhong Li, Yanping Zhang, Yiyang Gong, François St-Pierre, Michael Z Lin, Mark J Schnitzer
Electrophysiological field potential dynamics are of fundamental interest in basic and clinical neuroscience, but how specific cell types shape these dynamics in the live brain is poorly understood. To empower mechanistic studies, we created an optical technique, TEMPO, that records the aggregate trans-membrane voltage dynamics of genetically specified neurons in freely behaving mice. TEMPO has >10-fold greater sensitivity than prior fiber-optic techniques and attains the noise minimum set by quantum mechanical photon shot noise...
December 1, 2016: Cell
Daniel Mann, Christian Teuber, Stefan A Tennigkeit, Grit Schröter, Klaus Gerwert, Carsten Kötting
Heterotrimeric G proteins are crucial molecular switches that maintain a large number of physiological processes in cells. The signal is encoded into surface alterations of the Gα subunit that carries GTP in its active state and GDP in its inactive state. The ability of the Gα subunit to hydrolyze GTP is essential for signal termination. Regulator of G protein signaling (RGS) proteins accelerates this process. A key player in this catalyzed reaction is an arginine residue, Arg178 in Gαi1, which is already an intrinsic part of the catalytic center in Gα in contrast to small GTPases, at which the corresponding GTPase-activating protein (GAP) provides the arginine "finger...
November 28, 2016: Proceedings of the National Academy of Sciences of the United States of America
John F Barry, Matthew J Turner, Jennifer M Schloss, David R Glenn, Yuyu Song, Mikhail D Lukin, Hongkun Park, Ronald L Walsworth
Magnetic fields from neuronal action potentials (APs) pass largely unperturbed through biological tissue, allowing magnetic measurements of AP dynamics to be performed extracellularly or even outside intact organisms. To date, however, magnetic techniques for sensing neuronal activity have either operated at the macroscale with coarse spatial and/or temporal resolution-e.g., magnetic resonance imaging methods and magnetoencephalography-or been restricted to biophysics studies of excised neurons probed with cryogenic or bulky detectors that do not provide single-neuron spatial resolution and are not scalable to functional networks or intact organisms...
November 22, 2016: Proceedings of the National Academy of Sciences of the United States of America
Kosuke Kakuyanagi, Yuichiro Matsuzaki, Corentin Déprez, Hiraku Toida, Kouichi Semba, Hiroshi Yamaguchi, William J Munro, Shiro Saito
The hybridization of distinct quantum systems is now seen as an effective way to engineer the properties of an entire system leading to applications in quantum metamaterials, quantum simulation, and quantum metrology. Recent improvements in both fabrication techniques and qubit design have allowed the community to consider coupling large ensembles of artificial atoms, such as superconducting qubits, to a resonator. Here, we demonstrate the coherent coupling between a microwave resonator and a macroscopic ensemble composed of several thousand superconducting flux qubits, where we observe a large dispersive frequency shift in the spectrum of 250 MHz...
November 18, 2016: Physical Review Letters
Maika Takita, A D Córcoles, Easwar Magesan, Baleegh Abdo, Markus Brink, Andrew Cross, Jerry M Chow, Jay M Gambetta
We present parity measurements on a five-qubit lattice with connectivity amenable to the surface code quantum error correction architecture. Using all-microwave controls of superconducting qubits coupled via resonators, we encode the parities of four data qubit states in either the X or the Z basis. Given the connectivity of the lattice, we perform a full characterization of the static Z interactions within the set of five qubits, as well as dynamical Z interactions brought along by single- and two-qubit microwave drives...
November 18, 2016: Physical Review Letters
Fabian Ewert, Marcel Bergmann, Peter van Loock
We propose a projection measurement onto encoded Bell states with a static network of linear optical elements. By increasing the size of the quantum error correction code, both Bell measurement efficiency and photon-loss tolerance can be made arbitrarily high at the same time. As a main application, we show that all-optical quantum communication over large distances with communication rates similar to those of classical communication is possible solely based on local state teleportations using optical sources of encoded Bell states, fixed arrays of beam splitters, and photon detectors...
November 18, 2016: Physical Review Letters
C Krumnow, L Veis, Ö Legeza, J Eisert
Tensor network states and specifically matrix-product states have proven to be a powerful tool for simulating ground states of strongly correlated spin models. Recently, they have also been applied to interacting fermionic problems, specifically in the context of quantum chemistry. A new freedom arising in such nonlocal fermionic systems is the choice of orbitals, it being far from clear what choice of fermionic orbitals to make. In this Letter, we propose a way to overcome this challenge. We suggest a method intertwining the optimization over matrix product states with suitable fermionic Gaussian mode transformations...
November 18, 2016: Physical Review Letters
Piotr Tourkine, Pierre Vanhove
The monodromy relations in string theory provide a powerful and elegant formalism to understand some of the deepest properties of tree-level field theory amplitudes, like the color-kinematics duality. This duality has been instrumental in tremendous progress on the computations of loop amplitudes in quantum field theory, but a higher-loop generalization of the monodromy construction was lacking. In this Letter, we extend the monodromy relations to higher loops in open string theory. Our construction, based on a contour deformation argument of the open string diagram integrands, leads to new identities that relate planar and nonplanar topologies in string theory...
November 18, 2016: Physical Review Letters
Michael Förster, Timo Paschen, Michael Krüger, Christoph Lemell, Georg Wachter, Florian Libisch, Thomas Madlener, Joachim Burgdörfer, Peter Hommelhoff
We demonstrate coherent control of multiphoton and above-threshold photoemission from a single solid-state nanoemitter driven by a fundamental and a weak second harmonic laser pulse. Depending on the relative phase of the two pulses, electron emission is modulated with a contrast of the oscillating current signal of up to 94%. Electron spectra reveal that all observed photon orders are affected simultaneously and similarly. We confirm that photoemission takes place within 10 fs. Accompanying simulations indicate that the current modulation with its large contrast results from two interfering quantum pathways leading to electron emission...
November 18, 2016: Physical Review Letters
Siavash Golkar, Dung Xuan Nguyen, Matthew M Roberts, Dam Thanh Son
Fractional quantum Hall liquids exhibit a rich set of excitations, the lowest energy of which are the magnetorotons with dispersion minima at a finite momentum. We propose a theory of the magnetorotons on the quantum Hall plateaux near half filling, namely, at filling fractions ν=N/(2N+1) at large N. The theory involves an infinite number of bosonic fields arising from bosonizing the fluctuations of the shape of the composite Fermi surface. At zero momentum there are O(N) neutral excitations, each carrying a well-defined spin that runs integer values 2,3,…...
November 18, 2016: Physical Review Letters
Xi-Lin Wang, Luo-Kan Chen, W Li, H-L Huang, C Liu, C Chen, Y-H Luo, Z-E Su, D Wu, Z-D Li, H Lu, Y Hu, X Jiang, C-Z Peng, L Li, N-L Liu, Yu-Ao Chen, Chao-Yang Lu, Jian-Wei Pan
We report the first experimental demonstration of quantum entanglement among ten spatially separated single photons. A near-optimal entangled photon-pair source was developed with simultaneously a source brightness of ∼12  MHz/W, a collection efficiency of ∼70%, and an indistinguishability of ∼91% between independent photons, which was used for a step-by-step engineering of multiphoton entanglement. Under a pump power of 0.57 W, the ten-photon count rate was increased by about 2 orders of magnitude compared to previous experiments, while maintaining a state fidelity sufficiently high for proving the genuine ten-particle entanglement...
November 18, 2016: Physical Review Letters
Hiroaki Ishizuka, Tomoya Hayata, Masahito Ueda, Naoto Nagaosa
The photovoltaic effect due to the adiabatic quantum phase in noncentrosymmetric Weyl semimetals is studied. We particularly focus on the case in which an external ac electric field is applied. By considering a generalized Weyl Hamiltonian with nonlinear terms, we show that the photocurrent is induced by circularly, rather than linearly, polarized light. This photovoltaic current can be understood as an emergent electromagnetic induction in momentum space; the Weyl node is a magnetic monopole in momentum space, the circular motion of which induces the electric field...
November 18, 2016: Physical Review Letters
Jonathan M Edge, Yaron Kedem, Ulrich Aschauer, Nicola A Spaldin, Alexander V Balatsky
This corrects the article DOI: 10.1103/PhysRevLett.115.247002.
November 18, 2016: Physical Review Letters
L Rigovacca, C Di Franco, B J Metcalf, I A Walmsley, M S Kim
Interference lies at the heart of the behavior of classical and quantum light. It is thus crucial to understand the boundaries between which interference patterns can be explained by a classical electromagnetic description of light and which, on the other hand, can only be understood with a proper quantum mechanical approach. While the case of two-mode interference has received a lot of attention, the multimode case has not yet been fully explored. Here we study a general scenario of intensity interferometry: we derive a bound on the average correlations between pairs of output intensities for the classical wavelike model of light, and we show how it can be violated in a quantum framework...
November 18, 2016: Physical Review Letters
Michael Schuler, Seth Whitsitt, Louis-Paul Henry, Subir Sachdev, Andreas M Läuchli
The low-energy spectra of many body systems on a torus, of finite size L, are well understood in magnetically ordered and gapped topological phases. However, the spectra at quantum critical points separating such phases are largely unexplored for (2+1)D systems. Using a combination of analytical and numerical techniques, we accurately calculate and analyze the low-energy torus spectrum at an Ising critical point which provides a universal fingerprint of the underlying quantum field theory, with the energy levels given by universal numbers times 1/L...
November 18, 2016: Physical Review Letters
R P M J W Notermans, R J Rengelink, W Vassen
We observe a dramatic difference in optical line shapes of a ^{4}He Bose-Einstein condensate and a ^{3}He degenerate Fermi gas by measuring the 1557-nm 2 ^{3}S-2 ^{1}S magnetic dipole transition (8 Hz natural linewidth) in an optical dipole trap. The 15 kHz FWHM condensate line shape is only broadened by mean field interactions, whereas the degenerate Fermi gas line shape is broadened to 75 kHz FWHM due to the effect of Pauli exclusion on the spatial and momentum distributions. The asymmetric optical line shapes are observed in excellent agreement with line shape models for the quantum degenerate gases...
November 18, 2016: Physical Review Letters
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