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Dr. Thien H. Ngo Dr. Hülya Berndt Dr. Michael Wilsdorf Prof. Dr. Hans‐Ulrich Reissig 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(45):15155-15165
The dipeptide isostere 5‐aminothiophene carboxylic acid has been combined with L ‐phenylalanine moieties to provide linear and cyclic hybrid oligopeptides. A suitable protecting group strategy and appropriate coupling methods have been developed to guarantee a high degree of enantiopurity of the resulting amides. Cyclic tetraamides have been efficiently obtained by macrocyclization of the linear derivatives. In the case of racemized cyclization precursors, two diastereomeric macrocycles (S,S/R,R and meso) have been isolated. Their crystal structures show clear effects of the stereogenic centers on the ring conformations and molecular packing. 相似文献
23.
Specific ion effects on the electrophoretic mobility of small,highly charged peptides: A modeling study
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Stuart A. Allison Hengfu Wu Tuyen M. Bui Lac Dang Giang H. Huynh Tam Nguyen Linda Soegiarto Bi C. Truong 《Journal of separation science》2014,37(17):2403-2410
In this work, we use coarse‐grained modeling to study the free solution electrophoretic mobility of small highly charged peptides (lysine, arginine, and short oligos thereof (up to nonapeptides)) in NaCl and Na2SO4 aqueous solutions at neutral pH and room temperature. The experimental data are taken from the literature. A bead modeling methodology that treats the electrostatics at the level of the nonlinear Poisson Boltzmann equation developed previously in our laboratory is able to account for the mobility of all peptides in NaCl, but not Na2SO4. The peptide mobilities in Na2SO4 can be accounted for by including sulfate binding in the model and this is proposed as one possible explanation for the discrepancy. Oligo arginine peptides bind more sulfate than oligo lysines and sulfate binding increases with the oligo length. 相似文献
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Ngo Ngoc Ha Nguyen Truong Giang Tran Ngoc Khiem Nguyen Duc Dung Tom Gregorkiewicz 《固体物理学:研究快报》2016,10(11):824-827
Photogenerated carriers in Si–Ge alloy nanocrystals (NCs) prepared by co‐sputtering method were investigated by mean of transient induced absorption. The carrier relaxation features multiple components, with three decay life times of τ ≈ 600 fs, 12 ps, and 15 ns, established for Si0.2Ge0.8 alloy NCs of a mean crystal size of 9 nm and standard deviation of 3 nm. Deep carrier traps, identified at the boundary between the NCs and the SiO2 host with the ionization energy of about 1 eV, are characterized by a long‐range Coulombic potential. These are responsible for rapid depletion of free carrier population within a few picoseconds after the excitation, which explains the low emissivity of the investigated materials, and also sheds light on the generally low luminescence of Si/Ge and Ge NCs. (© 2016 WILEY‐VCH Verlag GmbH &Co. KGaA, Weinheim) 相似文献
26.
Yaqin Xu Zhuyuan Zhang Dr. M. Monsur Ali Joanna Sauder Xudong Deng Karen Giang Sergio D. Aguirre Prof. Dr. Robert Pelton Prof. Dr. Yingfu Li Prof. Dr. Carlos D. M. Filipe 《Angewandte Chemie (International ed. in English)》2014,53(10):2620-2622
An odor‐based sensor system that exploits the metabolic enzyme tryptophanase (TPase) as the key component is reported. This enzyme is able to convert an odorless substrate like S‐methyl‐L ‐cysteine or L ‐tryptophan into the odorous products methyl mercaptan or indole. To make a biosensor, TPase was biotinylated so that it could be coupled with a molecular recognition element, such as an antibody, to develop an ELISA‐like assay. This method was used for the detection of an antibody present in nM concentrations by the human nose. TPase can also be combined with the enzyme pyridoxal kinase (PKase) for use in a coupled assay to detect adenosine 5′‐triphosphate (ATP). When ATP is present in the low μM concentration range, the coupled enzymatic system generates an odor that is easily detectable by the human nose. Biotinylated TPase can be combined with various biotin‐labeled molecular recognition elements, thereby enabling a broad range of applications for this odor‐based reporting system. 相似文献
27.
Chemical Probing of the Human Sirtuin 5 Active Site Reveals Its Substrate Acyl Specificity and Peptide‐Based Inhibitors
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Claudia Roessler Theresa Nowak Martin Pannek Dr. Melanie Gertz Giang T. T. Nguyen Michael Scharfe Dr. Ilona Born Prof. Dr. Wolfgang Sippl Prof. Dr. Clemens Steegborn Prof. Dr. Mike Schutkowski 《Angewandte Chemie (International ed. in English)》2014,53(40):10728-10732
Sirtuins are NAD+‐dependent deacetylases acting as sensors in metabolic pathways and stress response. In mammals there are seven isoforms. The mitochondrial sirtuin 5 is a weak deacetylase but a very efficient demalonylase and desuccinylase; however, its substrate acyl specificity has not been systematically analyzed. Herein, we investigated a carbamoyl phosphate synthetase 1 derived peptide substrate and modified the lysine side chain systematically to determine the acyl specificity of Sirt5. From that point we designed six potent peptide‐based inhibitors that interact with the NAD+ binding pocket. To characterize the interaction details causing the different substrate and inhibition properties we report several X‐ray crystal structures of Sirt5 complexed with these peptides. Our results reveal the Sirt5 acyl selectivity and its molecular basis and enable the design of inhibitors for Sirt5. 相似文献
28.
Son Tung Ngo Trung Hai Nguyen Nguyen Thanh Tung Pham Cam Nam Khanh B. Vu Van V. Vu 《Journal of computational chemistry》2020,41(7):611-618
Determination of the ligand-binding affinity is an extremely interesting problem. Normally, the free energy perturbation (FEP) method provides an appropriate result. However, it is of great interest to improve the accuracy and precision of this method. In this context, temperature replica exchange molecular dynamics implementation of the FEP computational approach, which we call replica exchange free energy perturbation (REP) was proposed. In particular, during REP simulations, the system can easily escape from being trapped in local minima by exchanging configurations with high temperatures, resulting in significant improvement in the accuracy and precision of protein–ligand binding affinity calculations. The distribution of the decoupling free energy was enlarged, and its mean values were decreased. This results in changes in the magnitude of the calculated binding free energies as well as in alteration in the binding mechanism. Moreover, the REP correlation coefficient with respect to experiment ( RREP = 0.85 ± 0.15 ) is significantly boosted in comparison with the FEP one ( RFEP = 0.64 ± 0.30 ). Furthermore, the root-mean-square error (RMSE) of REP is also smaller than FEP, RMSEREP = 4.28 ± 0.69 versus RMSEFEP = 5.80 ± 1.11 kcal/mol, respectively. © 2019 Wiley Periodicals, Inc. 相似文献
29.
Optics and Spectroscopy - The design of neutral nonpolarizing interference systems formed on the face of one of the two prisms that are components of an optical element in the form of a cube is... 相似文献
30.
We study the nature of the smectic–isotropic phase transition using a mobile 6-state Potts model. Each Potts state represents a molecular orientation. We show that with the choice of an appropriate microscopic Hamiltonian describing the interaction between individual molecules modeled by a mobile 6-state Potts spins, we observe the smectic phase dynamically formed when we cool the molecules from the isotropic phase to low temperatures (T). In order to elucidate the order of the transition and the low-T properties, we use the high-performance Wang–Landau flat energy-histogram technique. We show that the smectic phase goes to the liquid (isotropic) phase by melting/evaporating layer by layer starting from the film surface with increasing T. At a higher T, the whole remaining layers become orientationally disordered. The melting of each layer is characterized by a peak of the specific heat. Such a succession of partial transitions cannot be seen by the Metropolis algorithm. The successive layer meltings/evaporations at low T are found to have a first-order character by examining the energy histogram. These results are in agreement with experiments performed on some smectic liquid crystals. 相似文献