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81.
We have calculated the correction to the density-of-states in two-dimensional weakly disordered systems. It is shown that the electron-electron interaction gives rise to a singularity in the density-of-states at the Fermi level, the form of which is very sensitive to the width of the sample. The transition from a two-dimensional behaviour to the quasi-one-dimensional regime is discussed. The effects should be observable by electron tunnelling measurements. 相似文献
82.
Dr. Giulia Giubertoni Gijs Rombouts Dr. Federico Caporaletti Dr. Antoine Deblais Rianne van Diest Prof. Dr. Joost N. H. Reek Prof. Dr. Daniel Bonn Prof. Dr. Sander Woutersen 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2023,135(2):e202213424
Inspired by ideas from NMR, we have developed Infrared Diffusion-Ordered Spectroscopy (IR-DOSY), which simultaneously characterizes molecular structure and size. We rely on the fact that the diffusion coefficient of a molecule is determined by its size through the Stokes–Einstein relation, and achieve sensitivity to the diffusion coefficient by creating a concentration gradient and tracking its equilibration in an IR-frequency resolved manner. Analogous to NMR-DOSY, a two-dimensional IR-DOSY spectrum has IR frequency along one axis and diffusion coefficient (or equivalently, size) along the other, so the chemical structure and the size of a compound are characterized simultaneously. In an IR-DOSY spectrum of a mixture, molecules with different sizes are nicely separated into distinct sets of IR peaks. Extending this idea to higher dimensions, we also perform 3D-IR-DOSY, in which we combine the conformation sensitivity of femtosecond multi-dimensional IR spectroscopy with size sensitivity. 相似文献
83.
Gijs van Soest Johan G Bosch Antonius F W van der Steen 《IEEE transactions on information technology in biomedicine》2008,12(3):348-355
Imaging modalities that use a mechanically rotated endoscopic probe to scan a tubular volume, such as an artery, often suffer from image degradation due to nonuniform rotation distortion (NURD). In this paper, we present a new method to align individual lines in a sequence of images. It is based on dynamic time warping, finding a continuous path through a cost matrix that measures the similarity between regions of two frames being aligned. The path represents the angular mismatch corresponding to the NURD. The prime advantage of this novel approach compared to earlier work is the line-to-line continuity, which accurately captures slow intraframe variations in rotational velocity of the probe. The algorithm is optimized using data from a clinically available intravascular optical coherence tomography (OCT) instrument in a realistic vessel phantom. Its efficacy is demonstrated on an in vivo recording, and compared with conventional global rotation block matching. Intravascular OCT is a particularly challenging modality for motion correction because, in clinical situations, the image is generally undersampled, and correlation between the speckle in different lines or frames is absent. The algorithm can be adapted to ingest data frame-by-frame, and can be implemented to work in real time. 相似文献
84.
Maarten IJsselstijn Begoña Aguilera Gijs A. van der Marel Floris L. van Delft Herman S. Overkleeft 《Tetrahedron letters》2004,45(22):4379-4382
The application of ring-closing alkyne metathesis to synthesise conformationally restricted peptidic β-turn mimics has been investigated. A range of oligopeptides containing either two acetylenic amino acids, or two cysteine residues have been synthesised and subjected to suitable cyclisation conditions. The structures of the cyclic compounds are investigated by 2D NMR analysis. 相似文献
85.
Verdoes M Florea BI van der Linden WA Renou D van den Nieuwendijk AM van der Marel GA Overkleeft HS 《Organic & biomolecular chemistry》2007,5(9):1416-1426
The synthesis and evaluation of hybrid proteasome inhibitors that contain structural elements of the known inhibitors bortezomib, epoxomicin and peptide vinyl sulfones is described. From the panel of 15 inhibitors some structure activity relationships can be deduced with regard to inhibitory activity in relation to peptide recognition element, inhibitor size and nature of the electrophilic trap. Further, the panel contains one of the most potent peptide-based pan-proteasome inhibitors reported to date. 相似文献
86.
87.
Knijnenburg AD Tuin AW Spalburg E de Neeling AJ Mars-Groenendijk RH Noort D Otero JM Llamas-Saiz AL van Raaij MJ van der Marel GA Overkleeft HS Overhand M 《Chemistry (Weinheim an der Bergstrasse, Germany)》2011,17(14):3995-4004
Monobenzylated sugar amino acids (SAAs) that differ in ether ring size (containing an oxetane, furanoid, and pyranoid ring) were synthesized and incorporated in one of the β-turn regions of the cyclo-decapeptide gramicidin S (GS). CD, NMR spectroscopy, modeling, and X-ray diffraction reveal that the ring size of the incorporated SAA moieties determines the spatial positioning of their cis-oriented carboxyl and aminomethyl substituents, thereby subtly influencing the amide linkages with the adjacent amino acids in the sequence. Unlike GS itself, the conformational behavior of the SAA-containing peptides is solvent dependent. The derivative containing the pyranoid SAA is slightly less hydrophobic and displays a diminished haemolytic activity, but has similar antimicrobial properties as GS. 相似文献
88.
Schmidt KS Boudvillain M Schwartz A van der Marel GA van Boom JH Reedijk J Lippert B 《Chemistry (Weinheim an der Bergstrasse, Germany)》2002,8(24):5566-5570
A solid-phase approach is described that provides facile access to monofunctionally trans-PtII-modified PNA oligomers of arbitrary sequence for potential use both in antigene and antisense strategies. The approach includes the synthesis of a platinated building block 1 and its subsequent incorporation into three different PNA oligomers 5-7 by solid-phase synthesis. In a model cross-linking reaction one of the latter is found to recognize sequence-specifically a target oligonucleotide 8 and to cross-link to it. The resulting structure is the trans-PtII-cross-linked PNA/DNA duplex 9 as revealed by mass spectrometry in combination with a Maxam-Gilbert sequencing experiment. 相似文献
89.
Poly(N-vinyl-2-pyrrolidone)-stabilized Pd-nanoclusters, for the first time exclusively supported on the hydrotalcite lateral surface, showed a remarkable catalytic performance in the selective hydrogenation of 3-hexyn-1-ol, which can be ascribed to both the influence of the protecting polymer PVP as well as the nature of the support. 相似文献
90.
Shinichi Takaichi Takashi Maoka Dimitry Yu. Sorokin Horia Banciu J. Gijs Kuenen 《Tetrahedron letters》2004,45(45):8303-8305
Two novel membrane-bound yellow pigments natronochrome (1) and chloronatronochrome (2) were isolated from the obligately chemolithoautotrophic sulfur-oxidizing natrono(alkali)philic bacterium Thialkalivibrio versutus strain ALJ 15. They were derivatives of fully unsaturated fatty acids with a phenyl group, and their structures were determined by spectral data. 相似文献