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51.
Agnes?Jankowska Christopher?K.?JankowskiEmail author Julien?B.?Chiasson 《Journal of inclusion phenomena and macrocyclic chemistry》2005,52(3-4):213-221
α-Chloralose is a useful mild anaesthetic, providing stable but not deep anaesthesia. Host–guest complexes of α-chloralose with α-, β- and γ-cyclodextrin (CD) were studied using electrospray ionisation (ESI-MS) mass spectrometry and molecular modelling (MD). As it is currently administered, chloralose is transported in a convenient water-soluble complex, and released to react on a physiological level with the reactor sites. It is believed that the chloraloses (α and its isomer β) are encapsulated within the CD cavity. However, the ESI spectra did not reveal such the presence of inclusion compounds. Searching of alternative mechanisms of transportation of these anaesthetic agents, we found that outer-cavity complexes of inserted chloraloses, as found from MD calculations, do have a reasonable stability.This revised version was published online in July 2005 with a corrected issue number. 相似文献
52.
Elbieta Jankowska Mirosaw Gilski Mariusz Jasklski Zbigniew Grzonka Leszek ankiewicz 《Acta Crystallographica. Section C, Structural Chemistry》2002,58(6):o353-o354
The crystal structure of the title compound, alternatively called 3‐[4‐(benzyloxy)phenyl]‐2‐(N‐tert‐butoxycarbonyl‐N‐methylamino)propionic acid, C22H27NO5, has been studied in order to examine the role of N‐methylation as a determinant of peptide conformation. The conformation of the tert‐butoxycarbonyl group is trans–trans. The side chain has a folded conformation and the two phenyl rings are effectively perpendicular to one another. The carboxylate hydroxyl group and the urethane carbonyl group form a strong intermolecular O—H?O hydrogen bond. 相似文献
53.
Aleksandra Jankowska Andrzej Kowalczyk Magorzata Rutkowska Marek Michalik Lucjan Chmielarz 《Molecules (Basel, Switzerland)》2021,26(6)
Aluminum containing silica spherical MCM-41 was synthesized and modified with copper by the template ion-exchange method (TIE) and its modified version, including treatment of the samples with ammonia solution directly after template ion-exchange (TIE-NH3). The obtained samples were characterized with respect to their chemical composition (ICP-OES), structure (XRD), texture (low temperature N2 sorption), morphology (SEM-EDS), form and aggregation of deposited copper species (UV-vis DRS), reducibility of copper species (H2-TPR), and surface acidity (NH3-TPD). The deposition of copper by the TIE-NH3 method resulted in much better dispersion of this metal on the MCM-41 surface comparing to copper introduced by TIE method. It was shown that such highly dispersed copper species, mainly monomeric Cu2+ cations, deposited on aluminum containing silica spheres of MCM-41, are significantly more catalytically effective in the NH3-SCR process than analogous catalysts containing aggregated copper oxide species. The catalysts obtained by the TIE-NH3 method effectively operated in much broader temperature and were less active in the side process of direct ammonia oxidation by oxygen. 相似文献
54.
Urszula Foryś Natalia Jankowska Katarzyna Cytlak Monika Joanna Piotrowska 《Mathematical Methods in the Applied Sciences》2020,43(18):10593-10618
In this paper, a delayed model of interactions between two actors in the context of their internal optimism and pessimism is studied. Considered model is based on the model proposed earlier in the context of romantic relationships. With the use of the system of nonlinear delay differential equations, we describe the change of emotions of two actors. Delays in the inertial component and in the influence function are introduced, and their influence on the system dynamics is investigated focusing on most beneficial meetings for actors. Finally, the modified systems are compared with the nondelayed case, and results are illustrated by numerical solutions for particular investigated scenarios. 相似文献
55.
Excited‐State Intramolecular Proton Transfer: Photoswitching in Salicylidene Methylamine Derivatives 下载免费PDF全文
Joanna Jankowska Dr. Michał F. Rode Prof. Joanna Sadlej Prof. Andrzej L. Sobolewski 《Chemphyschem》2014,15(8):1643-1652
The effect of chemical substitutions on the photophysical properties of the salicylidene methylamine molecule (SMA) (J. Jankowska, M. F. Rode, J. Sadlej, A. L. Sobolewski, ChemPhysChem, 2012 , 13, 4287–4294) is studied with the aid of ab initio electronic structure methods. It is shown that combining π‐electron‐donating and π‐electron‐withdrawing substituents results in an electron‐density push‐and‐pull effect on the energetic landscape of the ground and the lowest excited ππ* and nπ* singlet states of the system. The presented search for the most appropriate SMA derivatives with respect to their photoswitching functionality offers an efficient prescreening tool for finding chemical structures before real synthetic realization. 相似文献
56.
Zofia Peimel-Stuglik Stanisaw Kowalak Aldona Jankowska 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2008,69(5):1395
The aim of the work was to collect information concerning boundary effects which are suspected in α-alanine dosimeters consisted of powdered microcrystalline α-alanine and binders. In our experiments the conventional binders were replaced by molecular sieves (MS). MS are inorganic porous materials (host structures) with well organized and uniform intra-crystalline pore systems of nano-scale size. The guest molecules can be either physically adsorbed on very large inner MS surface, or chemically bound to the active sites. They can be also encapsulated inside the intracrystalline cavities. The EPR spectra of gamma irradiated dl-α-alanine supported on NaY, CeY, SOD, mordenite, ZSM-5 and ALPO4-5 were very similar to that one observed for irradiated microcrystalline dl-α-alanine. In the case of alanine supported on HY an initial EPR spectrum was different and only after some weeks it made resemble to the well known quintet observed in microcrystalline samples. In sodalites synthesized in the presence of dl-α-alanine EPR signal appeared in non-irradiated sample was very low and structureless. The irradiated sample showed a distinct spectrum which was quite different from that one observed for crystalline dl-α-alanine. 相似文献
57.
Jankowska E Pietruszka M Kowalik-Jankowska T 《Dalton transactions (Cambridge, England : 2003)》2012,41(6):1683-1694
A potentiometric, spectroscopic (UV-Vis, CD and EPR) and mass spectrometric (ESI-MS) study of Cu(II) binding to the (1-2,7-21)NPG, Asp(1)-Ala-Ile(7)-Ser-His(9)-Lys-Arg-His(12)-Lys-Thr-Asp-Ser-Phe-Val-Gly-Leu-Met(21)-NH(2), and Ac-(1-2,7-21)NPG, Ac-Asp(1)-Ala-Ile(7)-Ser-His(9)-Lys-Arg-His(12)-Lys-Thr-Asp-Ser-Phe-Val-Gly-Leu-Met(21)-NH(2), fragments of neuropeptide gamma were carried out. The results clearly indicate the stabilization of the 1 N {NH(2), β-COO(-)}, 2 N {NH(2), β-COO(-), N(Im)} and 3 N {NH(2), β-COO(-), 2N(Im)} complexes by the coordination of the β-carboxylate group of the D(1) residue. For the (1-2,7-21)NPG the CuH(2)L complex with 3 N {NH(2), β-COO(-), 2N(Im)}, the binding mode dominates in a wide pH range of 4-8.5. With the sequential increase of pH, deprotonated amide nitrogens are involved in copper coordination. For the Ac-(1-2,7-21)NPG peptide the imidazole nitrogen atoms are the primary metal binding sites forming macrochelates in the pH range 4 to 7. The CuHL complex with 4 N {N(Im), N(-), N(-), N(Im)} coordination mode is formed in pH range 6-9. Deprotonation and co-ordination of the third amide nitrogen were detected at pH ~8.6. Metal-catalyzed oxidation (MCO) of proteins is mainly a site-specific process in which one or a few amino acids at metal-binding sites on the protein are preferentially oxidized. To elucidate the products of the copper(II)-catalyzed oxidation of the (1-2,7-21)NPG and Ac-(1-2,7-21)NPG, the liquid chromatography-mass spectrometry (LC-MS) method and Cu(II)/hydrogen peroxide as a model oxidizing system were employed. In the presence of hydrogen peroxide with 1?:?4 peptide-H(2)O(2) molar ratio for the Ac-(1-2,7-21)NPG peptide the oxidation of the methionine residue to methionine sulfoxide and for (1-2,7-21)NPG to sulfone was observed. For the Cu(II)-peptide-hydrogen peroxide in 1?:?1?:?4 molar ratio systems, oxidation of the histidine residues to 2-oxohistidines was detected. Under experimental conditions the (1-2,7-21)NPG and Ac-(1-2,7-21)NPG undergo fragmentations by cleavage of the S(8)-H(9), H(9)-K(10), R(11)-H(12) and H(12)-K(13) peptide bonds supporting the participation of the H(9) and H(12) residues in the coordination of copper(II) ions. For the (1-2,7-21)NPG peptide chain the involvement of the D(1) residue in the coordination of metal ions is supported by the alkoxyl radical modification of this amino acid residue. 相似文献
58.
Catalytic asymmetric aldol reactions in aqueous media have been developed using chiral zinc complex. The aldol products have been obtained in high yields, high diastereocontrol, and good level of enantioselectivity. Various aromatic and alpha,beta-unsaturated aldehydes and silyl enol ethers derived from ketones can be employed in this reaction to provide the aldol adducts in good to high yield. The elaborated catalytic system has been found as selective for aliphatic aldehydes as well. 相似文献
59.
Cieślak J Jankowska J Stawiński J Kraszewski A 《The Journal of organic chemistry》2000,65(21):7049-7054
Transformation of nucleoside H-phosphonate monoesters into the corresponding H-phosphonothioate and H-phosphonodithioate derivatives and possible side-reactions that may accompany this process were studied using (31)P NMR spectroscopy. These provided new insight into a possible mechanism involved in this transformation and constituted the basis for development of efficient methods for the preparation of nucleoside H-phosphonothioate and nucleoside H-phosphonodithioate monoesters using readily available H-phosphonate monoesters as starting materials. 相似文献
60.
Agnes Jankowska Christopher K. Jankowski Julien B. Chiasson 《Journal of inclusion phenomena and macrocyclic chemistry》2005,52(3):213-221
α-Chloralose is a useful mild anaesthetic, providing stable but not deep anaesthesia. Host–guest complexes of α-chloralose with α-, β- and γ-cyclodextrin (CD) were studied using electrospray ionisation (ESI-MS) mass spectrometry and molecular modelling (MD). As it is currently administered, chloralose is transported in a convenient water-soluble complex, and released to react on a physiological level with the reactor sites. It is believed that the chloraloses (α and its isomer β) are encapsulated within the CD cavity. However, the ESI spectra did not reveal such the presence of inclusion compounds. Searching of alternative mechanisms of transportation of these anaesthetic agents, we found that outer-cavity complexes of inserted chloraloses, as found from MD calculations, do have a reasonable stability. 相似文献