TY - JOUR A1 - Harma, Harri A1 - Pihlasalo, Sari A1 - Cywinski, Piotr J. A1 - Mikkonen, Piia A1 - Hammann, Tommy A1 - Löhmannsröben, Hans-Gerd A1 - Hanninen, Pekka T1 - Protein quantification using resonance energy transfer between donor nanoparticles and acceptor quantum dots JF - Analytical chemistry N2 - A homogeneous time-resolved luminescence resonance energy transfer (TR-LRET) assay has been developed to quantify proteins. The competitive assay is based on resonance energy transfer (RET) between two luminescent nanosized particles. Polystyrene nanoparticles loaded with Eu3+ chelates (EuNPs) act as donors, while protein-coated quantum dots (QDs), either CdSe/ZnS emitting at 655 nm (QD655-strep) or CdSeTe/ZnS with emission wavelength at 705 nm (QD705-strep), are acceptors. In the absence of analyte protein, in our case bovine serum albumin (BSA), the protein-coated QDs bind nonspecifically to the EuNPs, leading to RET. In the presence of analyte proteins, the binding of the QDs to the EuNPs is prevented and the RET signal decreases. RET from the EuNPs to the QDs was confirmed and characterized with steady-state and time-resolved luminescence spectroscopy. In accordance with the Forster theory, the approximate average donor acceptor distance is around 15 nm at RET efficiencies, equal to 15% for QD655 and 13% for QD705 acceptor, respectively. The limits of detection are below 10 ng of BSA with less than a 10% average coefficient of variation. The assay sensitivity is improved, when compared to the most sensitive commercial methods. The presented mix-and-measure method has potential to be implemented into routine protein quantification in biological laboratories. Y1 - 2013 U6 - https://doi.org/10.1021/ac303586n SN - 0003-2700 VL - 85 IS - 5 SP - 2921 EP - 2926 PB - American Chemical Society CY - Washington ER - TY - JOUR A1 - Julich-Gruner, Konstanze K. A1 - Löwenberg, Candy A1 - Neffe, Axel T. A1 - Behl, Marc A1 - Lendlein, Andreas T1 - Recent trends in the chemistry of shape-memory polymers JF - Macromolecular chemistry and physics N2 - Shape-memory polymers (SMPs) are stimuli-sensitive materials capable of performing complex movements on demand, which makes them interesting candidates for various applications, for example, in biomedicine or aerospace. This trend article highlights current approaches in the chemistry of SMPs, such as tailored segment chemistry to integrate additional functions and novel synthetic routes toward permanent and temporary netpoints. Multiphase polymer networks and multimaterial systems illustrate that SMPs can be constructed as a modular system of different building blocks and netpoints. Future developments are aiming at multifunctional and multistimuli-sensitive SMPs. KW - multifunctional polymers KW - networks KW - shape-memory polymers KW - stimuli-sensitive polymers KW - triple-shape effect Y1 - 2013 U6 - https://doi.org/10.1002/macp.201200607 SN - 1022-1352 VL - 214 IS - 5 SP - 527 EP - 536 PB - Wiley-VCH CY - Weinheim ER - TY - JOUR A1 - Beye, Martin A1 - Föhlisch, Alexander T1 - Soft X-ray probes of ultrafast dynamics for heterogeneous catalysis JF - Chemical physics : a journal devoted to experimental and theoretical research involving problems of both a chemical and physical nature N2 - Soft X-ray spectroscopy is one of the best tools to directly address the electronic structure, the driving force of chemical reactions. It enables selective studies on sample surfaces to single out reaction centers in heterogeneous catalytic reactions. With core-hole clock methods, specific dynamics are related to the femtosecond life time of a core-hole. Typically, this method is used with photoemission spectroscopy, but advancements in soft X-ray emission techniques render more specific studies possible. With the advent of bright femtosecond pulsed soft X-ray sources, highly selective pump-probe X-ray emission studies are enabled with temporal resolutions down to tens of femtoseconds. This finally allows to study dynamics in the electronic structure of adsorbed reaction centers on the whole range of relevant time scales - closing the gap between kinetic soft X-ray studies and the atto- to femtosecond core-hole clock techniques. KW - Core-hole clock KW - Resonant inelastic X-ray scattering KW - Ultrafast surface science KW - Photoelectron spectroscopy Y1 - 2013 U6 - https://doi.org/10.1016/j.chemphys.2012.03.023 SN - 0301-0104 SN - 1873-4421 VL - 414 IS - 5 SP - 130 EP - 138 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Jechow, Andreas A1 - Norton, B. G. A1 - Händel, S. A1 - Blums, V. A1 - Streed, E. W. A1 - Kielpinski, D. T1 - Controllable optical phase shift over one radian from a single isolated atom JF - Physical review letters N2 - Fundamental optics such as lenses and prisms work by applying phase shifts of several radians to incoming light, and rapid control of such phase shifts is crucial to telecommunications. However, large, controllable optical phase shifts have remained elusive for isolated quantum systems. We have used a single trapped atomic ion to induce and measure a large optical phase shift of 1.3 +/- 0.1 radians in light scattered by the atom. Spatial interferometry between the scattered light and unscattered illumination light enables us to isolate the phase shift in the scattered component. The phase shift achieves the maximum value allowed by atomic theory over the accessible range of laser frequencies, pointing out new opportunities in microscopy and nanophotonics. Single-atom phase shifts of this magnitude open up new quantum information protocols, in particular long-range quantum phase-shift-keying cryptography. DOI: 10.1103/PhysRevLett.110.113605 Y1 - 2013 U6 - https://doi.org/10.1103/PhysRevLett.110.113605 SN - 0031-9007 VL - 110 IS - 11 PB - American Physical Society CY - College Park ER - TY - JOUR A1 - Osterloh, Lukas A1 - Böckmann, Christine A1 - Nicolae, Doina A1 - Nemuc, Anca T1 - Regularized inversion of microphysical atmospheric particle parameters - theory and application JF - Journal of computational physics N2 - Retrieving the distribution of aerosols in the atmosphere via remote sensing techniques is a highly complex task that requires dealing with a wide range of different problems stemming both from Physics and Mathematics. We focus on retrieving this distribution from multi-wavelength lidar data for aerosol ensembles consisting of spherical particles via an iterative regularization technique. The optical efficiencies for spherical scatterers are examined to account for the behavior of the underlying integral equation. The ill-posedness of the problem and the conditioning of the discretized problem are analyzed. Some critical points in the model, like the assumed wavelength-independence of the refractive index and the fixed grid of investigated refractive indices, are studied with regard to their expected impact on the regularized solution. A new Monte-Carlo type method is proposed for retrieval of the refractive index. To validate the results, the developed algorithm is applied to two measurement cases of burning biomass gained from multi-wavelength Raman lidar. KW - Inverse ill-posed problem KW - Regularization KW - Lidar remote sensing KW - Microphysical particle properties Y1 - 2013 U6 - https://doi.org/10.1016/j.jcp.2012.11.040 SN - 0021-9991 VL - 237 IS - 11 SP - 79 EP - 94 PB - Elsevier CY - San Diego ER - TY - JOUR A1 - Lemke, Karina A1 - Prietzel, Claudia Christina A1 - Koetz, Joachim T1 - Fluorescent gold clusters synthesized in a poly(ethyleneimine) modified reverse microemulsion JF - Journal of colloid and interface science N2 - This paper is focused on the formation of gold clusters in a tailor-made polyelectrolyte-modified reverse microemulsion using poly(ethyleneimine) (PEI) as a cationic polyelectrolyte. PEI incorporated into a ternary w/o microemulsion consisting of water/heptanol/zwitterionic surfactant 3-(N,N-dimethyl-dodecylammonio)-propanesulfonate (SB) acts as a reducing and stabilizing agent and shows an additional template effect. The nanoparticle synthesis is performed by a simple mixing of two microemulsions, one containing the PEI and the other one containing the gold chloride precursor. UV-vis measurements in the microemulsion show two pronounced absorption maxima, one at 360 nm and the other one at 520 nm, indicating two particle fractions. The absorption maximum at 360 nm in combination to the unique fluorescence properties indicate the formation of gold clusters. After a complete solvent evaporation the redispersed nanoparticles have been characterized by using UV-vis and fluorescence spectroscopy, in combination to dynamic light scattering and transmission electron microscopy (TEM). In addition to the gold nanoparticle fraction (>5 nm) the fluorescent gold cluster fraction (<2 nm) can be redispersed without particle aggregation. By means of asymmetric flow field flow fractionation (AF-FFF) two different cluster fractions with particle diameter (<2 nm) can be identified. KW - Microemulsion KW - Gold cluster KW - Field flow fractionation KW - Polymer capped gold nanoparticles Y1 - 2013 U6 - https://doi.org/10.1016/j.jcis.2012.11.057 SN - 0021-9797 VL - 394 SP - 141 EP - 146 PB - Elsevier CY - San Diego ER - TY - JOUR A1 - Dell'Angela, M. A1 - Anniyev, Toyli A1 - Beye, Martin A1 - Coffee, Ryan A1 - Föhlisch, Alexander A1 - Gladh, J. A1 - Katayama, T. A1 - Kaya, S. A1 - Krupin, O. A1 - LaRue, J. A1 - Mogelhoj, A. A1 - Nordlund, D. A1 - Norskov, J. K. A1 - Oberg, H. A1 - Ogasawara, H. A1 - Ostrom, H. A1 - Pettersson, Lars G. M. A1 - Schlotter, W. F. A1 - Sellberg, J. A. A1 - Sorgenfrei, Nomi A1 - Turner, J. J. A1 - Wolf, M. A1 - Wurth, W. A1 - Nilsson, A. T1 - Real-time observation of surface bond breaking with an X-ray Laser JF - Science N2 - We used the Linac Coherent Light Source free-electron x-ray laser to probe the electronic structure of CO molecules as their chemisorption state on Ru(0001) changes upon exciting the substrate by using a femtosecond optical laser pulse. We observed electronic structure changes that are consistent with a weakening of the CO interaction with the substrate but without notable desorption. A large fraction of the molecules (30%) was trapped in a transient precursor state that would precede desorption. We calculated the free energy of the molecule as a function of the desorption reaction coordinate using density functional theory, including van der Waals interactions. Two distinct adsorption wells-chemisorbed and precursor state separated by an entropy barrier-explain the anomalously high prefactors often observed in desorption of molecules from metals. Y1 - 2013 U6 - https://doi.org/10.1126/science.1231711 SN - 0036-8075 VL - 339 IS - 6125 SP - 1302 EP - 1305 PB - American Assoc. for the Advancement of Science CY - Washington ER - TY - JOUR A1 - Kleinpeter, Erich A1 - Werner, Peter A1 - Koch, Andreas T1 - Push-pull allenes-conjugation, (anti)aromaticity and quantification of the push-pull character JF - Tetrahedron N2 - Structures, H-1/C-13 chemical shifts, and pi electron distribution/conjugation of an experimentally available and theoretically completed set of push-pull allenes Acc(2)C=C=CDon(2) (Acc=F, CHO, CF3, C N; Don=t-Bu, OMe, OEt, SMe, SEt, NCH2R) have been computed at the OFT level of theory. Both orthogonal linear and orthogonal bent structures have been obtained. In the latter case the push-pull character could be quantified by the quotient method. The C-13 chemical shift of the central allene carbon atom C-2 and chemical shift differences Delta delta(C-1, C-2) and Delta delta(C-2, C-3) of allene carbon atoms proved to be a quantitative alternative. TSNMRS of ring-closed push-pull allenes have been computed in addition and were employed to identify polar, carbene-like and carbone-like canonical structures of these molecules. KW - Push-pull allenes KW - Push-pull character KW - C-13 NMR spectroscopy KW - Quotient method KW - TSNMRS KW - ICSS KW - Aromaticity Y1 - 2013 U6 - https://doi.org/10.1016/j.tet.2013.01.027 SN - 0040-4020 VL - 69 IS - 11 SP - 2436 EP - 2445 PB - Elsevier CY - Oxford ER - TY - JOUR A1 - Pohl, Martin A1 - Eichler, David T1 - Understanding TeV-band cosmic-ray anistropy JF - The astrophysical journal : an international review of spectroscopy and astronomical physics N2 - We investigate the temporal and spectral correlations between flux and anisotropy fluctuations of TeV-band cosmic rays in light of recent data taken with IceCube. We find that for a conventional distribution of cosmic-ray sources, the dipole anisotropy is higher than observed, even if source discreteness is taken into account. Moreover, even for a shallow distribution of galactic cosmic-ray sources and a reacceleration model, fluctuations arising from source discreteness provide a probability only of the order of 10% that the cosmic-ray anisotropy limits of the recent IceCube analysis are met. This probability estimate is nearly independent of the exact choice of source rate, but generous for a large halo size. The location of the intensity maximum far from the Galactic Center is naturally reproduced. KW - cosmic rays Y1 - 2013 U6 - https://doi.org/10.1088/0004-637X/766/1/4 SN - 0004-637X VL - 766 IS - 1 PB - IOP Publ. Ltd. CY - Bristol ER - TY - JOUR A1 - Taft, Linda A1 - Wiechert, Uwe A1 - Zhang, Hucai A1 - Lei, Guoliang A1 - Mischke, Steffen A1 - Plessen, Birgit A1 - Weynell, Marc A1 - Winkler, Andreas A1 - Riedel, Frank T1 - Oxygen and carbon isotope patterns archived in shells of the aquatic gastropod Radix - hydrologic and climatic signals across the Tibetan Plateau in sub-monthly resolution JF - Quaternary international : the journal of the International Union for Quaternary Research N2 - The Tibetan Plateau (TP), including its surrounding mountain ranges, represents the largest store of ice outside the polar regions. It hosts numerous lakes as well as the head waters of major Asian rivers, on which billions of people depend, and it is particularly sensitive to climate change. The moisture transport to the TP is controlled by the Indian and Pacific monsoon and the Westerlies. Understanding the evolution of the interaction of these circulation systems requires studies on climate archives in different spatial and temporal contexts. The objective of this study is to learn more about the interannual variability of precipitation patterns across the TP and how different hydrologic systems react to different climatic factors. Aragonite shells of the aquatic gastropod Radix, which is widely distributed in the region, may represent suitable archives for inferring hydrologic and climatic signals in particularly high resolution. Therefore, sclerochronological studies of delta O-18 and delta C-13 ratios in Radix shells from seven lakes were conducted, each representing a different hydrologic and climatic setting, on a transect from the Pamirs across the TP. The shell patterns exhibit an increasing influence of precipitation and a decreasing influence of evaporation on the isotope compositions from west to east. delta O-18 values of shells from lakes on the eastern and central TP (Donggi Cona, Yamdrok Yumco, Tarab Co) mirror monsoon signals, indicated by more negative values and higher variabilities compared to the more western lakes (Karakul, Bangong/Nyak, Manasarovar). In Yadang Co, located on the central southern TP, the monsoon rains did not reach the lake in the sampling year, although it is located in a region which is usually affected by monsoon circulation. The delta O-18 values are used to differentiate the annual hydrological cycle into ice cover period, melt water period, precipitation period and evaporation period. delta C-13 compositions in the shells particularly depend on specific habitats, which vary in biological productivity and in carbon sources. delta O-18 and delta C-13 patterns show a positive covariance in shells originating from large closed basins. The results show that Radix shells mirror general climatic differences between the seven lake regions. These differences reflect both regional and local climate signals in sub-seasonal resolution, without noticeable dependence on the particular lake system. Y1 - 2013 U6 - https://doi.org/10.1016/j.quaint.2012.10.031 SN - 1040-6182 VL - 290 IS - 1 SP - 282 EP - 298 PB - Elsevier CY - Oxford ER -