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51.
52.
The synthesis of two oligomers, of a bifunctional diketopiperazine scaffold DKP-1, formally derived from the cyclization of l-aspartic acid and (S)-2,3-diaminopropionic acid, is reported. A trimeric and a tetrameric structure were prepared by solution-phase peptide synthesis (Boc strategy). Conformational analysis of these derivatives was carried out by a combination of 1H NMR spectroscopy, CD spectroscopy, and molecular modeling, and revealed the formation of β-bend ribbon involving 10-membered H-bonded rings and a reverse turn of the growing peptide chain. 相似文献
53.
Umberto M. Battisti Marina M. Carrozzo Carlo Parenti Luigino Troisi 《Tetrahedron letters》2010,51(33):4433-4436
A simple and efficient synthetic path for N-1 or N-2 alkyl-substituted 2-aminobenzenesulfonamides was developed based on regioselective reduction with NaBH3CN in different solvents. 相似文献
54.
Umberto Casellato Rodolfo Graziani Giuseppe Maccarrone Angel J. di Bilio 《Journal of chemical crystallography》1986,16(5):695-702
cis-Diaquabis(2,2-bipyridyl)chromium(III) nitrate crystallizes in the mono-clinic system, space groupP21/c, witha=16.102(6),b=10.792(5),c=15.076(6) Å,=112.90(5)°, andZ=4. The saltlike structure was determined from X-ray crystallography and refined toR=7.5% for 3342 observed reflections. The Cr atom is octahedrally surrounded by twocis water molecules and by two chelated 2,2-bypiridyl ligands forming two nearly orthogonal planes. Selected bond distances are: Cr-O, 2.00(1) and 1.98(1) Å, Cr-N, 2.04 Å (mean). 相似文献
55.
Pegna R Nobili AM Shao M Turyshev SG Catastini G Anselmi A Spero R Doravari S Comandi GL De Michele A 《Physical review letters》2011,107(20):200801
Mechanical oscillators can be sensitive to very small forces. Low frequency effects are up-converted to higher frequency by rotating the oscillator. We show that for 2-dimensional oscillators rotating at frequency much higher than the signal the thermal noise force due to internal losses and competing with it is abated as the square root of the rotation frequency. We also show that rotation at frequency much higher than the natural one is possible if the oscillator has 2 degrees of freedom, and describe how this property applies also to torsion balances. In addition, in the 2D oscillator the signal is up-converted above resonance without being attenuated as in the 1D case, thus relaxing requirements on the read out. This work indicates that proof masses weakly coupled in 2D and rapidly rotating can play a major role in very small force physics experiments. 相似文献
56.
Alberto Bolognesi Paolo DiGianvincenzo Umberto Giovanella Raniero Mendichi Alberto Giacometti Schieroni 《European Polymer Journal》2008,44(3):793-800
The control of the organization of polymeric films from the nano- to the meso-scale is an ongoing field and different approaches have been proposed by many authors with the aim to drive the organization and the morphology of the materials to optimize their properties. One of the driving force of the organization at the micrometric and submicrometric scale is the degree of interaction between different polymeric chains and many successful examples of ordered supramolecular organization based on nano and microphase separation have been reported by using block copolymers and polymer blends. In this work we report on a synthetic approach to prepare a copolymeric structure formed by polystyrene and 3,4-ethylenedioxythiophene (EDOT) oligomers with the aim of preparing thin polymeric films exhibiting organized morphologies. 相似文献
57.
JPC – Journal of Planar Chromatography – Modern TLC - Anew OPLC method has been established for separation and quantitative determination of three alditols (d-xylitol, L-arabitol, and... 相似文献
58.
A groupG is said to be (2,3)-generated if it can be generated by two elements of respective orders 2 and 3. The class of these groups has recently received a lot of attention by several authors: a brief survey of the results in this area is given in the introduction. In this paper we show that, ifR is a ring generated by one element of finite multiplicative order, then the analogues of classical groups overR are (2,3)-generated, provided that their rank is sufficiently large. Our lower bound for the rank improves previous results. 相似文献
59.
Simone Zanella Dr. Michele Mingozzi Alberto Dal Corso Dr. Roberto Fanelli Dr. Daniela Arosio Prof. Dr. Marco Cosentino Dr. Laura Schembri Dr. Franca Marino Dr. Marta De Zotti Prof. Dr. Fernando Formaggio Dr. Luca Pignataro Prof. Dr. Laura Belvisi Prof. Dr. Umberto Piarulli Prof. Dr. Cesare Gennari 《ChemistryOpen》2015,4(5):633-641
A dual-action ligand targeting both integrin αVβ3 and vascular endothelial growth factor receptors (VEGFRs), was synthesized via conjugation of a cyclic peptidomimetic αVβ3 Arg-Gly-Asp (RGD) ligand with a decapentapeptide. The latter was obtained from a known VEGFR antagonist by acetylation at the Lys13 side chain. Functionalization of the precursor ligands was carried out in solution and in the solid phase, affording two fragments: an alkyne VEGFR ligand and the azide integrin αVβ3 ligand, which were conjugated by click chemistry. Circular dichroism studies confirmed that both the RGD and VEGFR ligand portions of the dual-action compound substantially adopt the biologically active conformation. In vitro binding assays on isolated integrin αVβ3 and VEGFR-1 showed that the dual-action conjugate retains a good level of affinity for both its target receptors, although with one order of magnitude (10/20 times) decrease in potency. The dual-action ligand strongly inhibited the VEGF-induced morphogenesis in Human Umbilical Vein Endothelial Cells (HUVECs). Remarkably, its efficiency in preventing the formation of new blood vessels was similar to that of the original individual ligands, despite the worse affinity towards integrin αVβ3 and VEGFR-1. 相似文献
60.
A method for crack localization, based on so-called Local Modal Crack Sensitivity (LMCS), has recently been proposed by one of the Authors. As a major feature, the method only involves measuring eigenfrequencies. The method has already been used for beams of uniform cross section and homogeneous boundary conditions. In this paper, the method is extended to stepped beams, with both homogeneous and non-homogeneous boundary conditions. Experimental results confirm its usefulness for crack localization. Satisfactory localization of a second crack was also possible, so confirming the effectiveness of the method. 相似文献