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Wyświetlanie 1-10 z 17
Tytuł:
Contribution of the intra- and intermolecular routes in autocatalytic zymogen activation: application to pepsinogen activation
Autorzy:
Varón, Ramón
Fuentes, Matilde
García-Moreno, Manuela
Garcìa-Sevilla, Francisco
Arias, Enrique
Valero, Edelmira
Arribas, Enrique
Tematy:
intermolecular activation
intramolecular activation
autocatalysis
enzyme kinetics
proenzyme activation
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Wydawca:
Polskie Towarzystwo Biochemiczne
Powiązania:
https://bibliotekanauki.pl/articles/1041258.pdf  Link otwiera się w nowym oknie
Opis:
Taking as the starting point a recently suggested reaction scheme for zymogen activation involving intra- and intermolecular routes and the enzyme-zymogen complex, we carry out a complete analysis of the relative contribution of both routes in the process. This analysis suggests the definition of new dimensionless parameters allowing the elaboration, from the values of the rate constants and initial conditions, of the time course of the contribution of the two routes. The procedure mentioned above related to a concrete reaction scheme is extrapolated to any other model of autocatalytic zymogen activation involving intra- and intermolecular routes. Finally, we discuss the contribution of both of the activating routes in pepsinogen activation into pepsin using the values of the kinetic parameters given in the literature.
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Conformation of the Ester Group Governs the Photophysics of Highly Polarized Benzo[g]coumarins
Autorzy:
Sobolewski, Andrzej
Szychta, Kamil
Clark, John A.
Banasiewicz, Marzena
Barboza, Cristina A.
Gryko, Daniel T.
Vullev, Valentine I.
Koszarna, Beata
O’Mari, Omar
Wydawca:
American Chemical Society
Cytata wydawnicza:
JACS Au 2023, 3, 7, 1918–1930 ; https://doi.org/10.1021/jacsau.3c00169
Opis:
Polish National Science Center (HARMONIA 2018/30/M/ST5/00460; OPUS 2016/23/B/ST5/03322); Foundation for Polish Science (TEAM POIR.04.04.00-00-3CF4/16-00); USA National Science Foundation (grant numbers CHE 1800602 and CHE 2154609); American Chemical Society Petroleum Research Fund (grant number 60651-ND4); European Union’s Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreements no. 101007804 (Micro4Nano) and no. 860762 (MSC ITN CHAIR)
Photosensitizers that display “unusual” emission from upper electronically excited states offer possibilities for initiating higher-energy processes than what the governing Kasha’s rule postulates. Achieving conditions for dual fluorescence from multiple states of the same species requires molecular design and conditions that favorably tune the excited-state dynamics. Herein, we switch the position of the electron-donating NMe2 group around the core of benzo[g]coumarins (BgCoum) and tune the electronic coupling and the charge-transfer character of the fluorescent excited states. For solvents with intermediate polarity, three of the four regioisomers exhibit fluorescence from two different excited states with bands that are well separated in the visible and the near-infrared spectral regions. Computational analysis, employing ab initio methods, reveals that the orientation of an ester on the pyrone ring produces two conformers responsible for the observed dual fluorescence. Studies with solid solvating media, which restricts the conformational degrees of freedom, concur with the computational findings. These results demonstrate how “seemingly inconsequential” auxiliary substituents, such as the esters on the pyrone coumarin rings, can have profound effects leading to “anti-Kasha” photophysical behavior important for molecular photonics, materials engineering, and solar-energy science.
Dostawca treści:
Repozytorium Centrum Otwartej Nauki
Artykuł
Tytuł:
Novel Method for the Synthesis of Merocyanines: New Photophysical Possibilities for a Known Class of Fluorophores
Autorzy:
Vakuliuk, Olena
Gryko, Daniel T.
Terenziani, Francesca
Bardi, Brunella
Dobrzycki, Łukasz
Painelli, Anna
Koszarna, Beata
Vygranenko, Katerina V.
Wydawca:
Wiley
Cytata wydawnicza:
Chem. Eur. J. 2023, e202300979 ; https://doi.org/10.1002/chem.202300979
Opis:
Foundation for Polish Science (TEAM POIR.04.04.00-00-3CF4/16-00); European Union Horizon 2020 research and innovation programme (GA 101007804, Micro4Nano); PNRR-MUR project ECS_00000033_ECOSISTER; HPC (High Performance Computing) University of Parma; COMP-HUB and COMP—R Initiatives, funded by the 'Departments of Excellence’ (Italian Ministry for University and Research (MIUR, 2018–2022 and MUR, 2023–2027))
A new, transformative method for the preparation of rhodols and other merocyanines from readily available tetrafluorohydroxybenzaldehyde and aminophenols has been developed. It is now possible to prepare merocyanines bearing three fluorine atoms and additional conjugated rings, and the whole one-pot process occurs under neutral, mild conditions. Three heretofore unknown merocyanine-based architectures were prepared using this strategy from aminonaphthols and 4-hydroxycoumarins. The ability to change the structure of original rhodol chromophore into π-expanded merocyanines translates to a comprehensive method for the modulation of photophysical properties, such as shifting the absorption and emission bands across almost the entire visible spectrum, reaching a huge Stokes shift i. e. 4800 cm−1, brightness approximately 80.000 M−1 cm−1, two-photon absorption cross-section above 150 GM and switching-on/off solvatofluorochromism. A detailed investigation allowed to rationalize the different spectroscopic behavior of rhodols and new merocyanines, addressing solvatochromism and two-photon absorption.
Dostawca treści:
Repozytorium Centrum Otwartej Nauki
Artykuł
Tytuł:
Intrinsic deuterium isotope effects on NMR chemical shifts of hydrogen bonded systems
Autorzy:
Hansen, P.
Tematy:
C-H hydrogen bonds
deuterium isotope effects
intramolecular hydrogen bonds
intrinsic isotope effects
nuclear shielding
steric effects
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Wydawca:
Instytut Chemii i Techniki Jądrowej
Powiązania:
https://bibliotekanauki.pl/articles/146965.pdf  Link otwiera się w nowym oknie
Opis:
This mini review describes intrinsic deuterium isotope effects on 13C chemical shifts of rigid hydrogen bonded compounds primarily in solution. The steric effects of intramolecularly hydrogen bonded compounds are dissected into different bond interactions leading either to steric compression or to steric twist. One-bond isotope effects involving CH(D) bonds are analyzed in terms of substituent effects and the question is raised whether isotope effects can be useful in the study of CHhydrogen bonds.
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Modelling DNA and RNA secondary structures using matrix insertion-deletion systems
Autorzy:
Kuppusamy, L.
Mahendran, A.
Tematy:
biomolecular structure
insertion deletion system
intermolecular
intramolecular
secondary structure
struktura biomolekularna
struktura międzycząsteczkowa
struktura wtórna
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Wydawca:
Uniwersytet Zielonogórski. Oficyna Wydawnicza
Powiązania:
https://bibliotekanauki.pl/articles/330807.pdf  Link otwiera się w nowym oknie
Opis:
Insertion and deletion are operations that occur commonly in DNA processing and RNA editing. Since biological macromolecules can be viewed as symbols, gene sequences can be represented as strings and structures can be interpreted as languages. This suggests that the bio-molecular structures that occur at different levels can be theoretically studied by formal languages. In the literature, there is no unique grammar formalism that captures various bio-molecular structures. To overcome this deficiency, in this paper, we introduce a simple grammar model called the matrix insertion–deletion system, and using it we model several bio-molecular structures that occur at the intramolecular, intermolecular and RNA secondary levels.
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Atroposelektywna synteza naturalnych chiralnych osiowo związków biarylowych. Część 2
Atroposelective synthesis of natural axially chiral biaryl compounds. Part 2
Autorzy:
Kołodziejska, R.
Tafelska-Kaczmarek, A.
Studzińska, R.
Tematy:
chiralne osiowo biaryle
wewnątrzcząsteczkowa reakcja sprzęgania
międzycząsteczkowa reakcja sprzęgania
axially chiral biaryls
intramolecular coupling
intermolecular coupling
Pokaż więcej
Wydawca:
Polskie Towarzystwo Chemiczne
Powiązania:
https://bibliotekanauki.pl/articles/171989.pdf  Link otwiera się w nowym oknie
Opis:
A direct aryl-aryl coupling reaction is the most common method for the synthesis of axially chiral biaryls. Atroposelective coupling can be accomplished by three main strategies (Scheme 1) [1, 11]: a) intramolecular coupling reaction between two aryl substrates by the use of the chiral tether as a source of asymmetric information (Scheme 2), b) intermolecular reaction of the modified aryl compounds containing a chiral auxiliary. A source of chiral information can be a planar-chiral element, the chiral leaving group, and the chiral ortho substituent (Scheme 12, 16, 17), c) intermolecular coupling in the presence of chiral additives, for example, stoichiometric or catalytic oxidation in the presence of the transition metal complexes containing chiral ligands, and the redox-neutral coupling reactions catalyzed by transition metal complexes with chiral bidentate N/P- -ligands (Scheme 18, 20–22). These methods have been applied in the synthesis of various biologically active compounds. For example, Lipshutzet et al. obtained a fragment of the antibiotic vancomycin [15], and O-permethyltellimagrandin II [16]. Lin and coworkers synthesized (P)-kotanin [17], the natural metabolite from Aspergillus glaucus (Scheme 3). Waldvogel and coworkers [19] received steganacin derivative, a cytostatic drug (Scheme 5). Coleman et al. in the oxidative dimerization reaction of aryls with a chiral ortho substituents obtained a precursor in the synthesis of calphostin A (Scheme 8) [26]. Meyers and coworkers [27, 28] applied the Ullmann homocoupling for the synthesis of gossypol (Scheme 9). The oxidative coupling of phenols allows to obtain the natural precursor of nigerone (Scheme 13) [42]. Whereas the calphostin [18] derivative, an inhibitor of protein kinase C, was obtained by the oxidative coupling reaction (Scheme 4). The schizandrin [23] from Schisandra chinensis and isodiospyrin [24] from Diospyros morrisiana were obtained by intermolecular coupling reaction of aryl substrates with the chiral ortho substituents (Scheme 7).
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Prolina – pospolity aminokwas wyjątkowy katalizator. Część I, Biosynteza proliny. Wewnątrzcząsteczkowa kondensacja aldolowa
Proline as a common amino acid and an exceptional catalyst. Part I, Proline biosynthesis. Intramolecular aldol reaction
Autorzy:
Wróblewski, M.
Kołodziejska, R.
Studzińska, R.
Karczmarska-Wódzka, A.
Dramiński, M.
Tematy:
biosynteza proliny
mechanizm kondensacji aldolowej
wewnątrzcząsteczkowa reakcja aldolowa
proline biosynthesis
mechanism of aldol reaction
intramolecular aldol reaction
Pokaż więcej
Wydawca:
Polskie Towarzystwo Chemiczne
Powiązania:
https://bibliotekanauki.pl/articles/172473.pdf  Link otwiera się w nowym oknie
Opis:
In asymmetric synthesis of organic compounds more effective solutions are being looked for which will result in higher yield(s) of product(s) and their high enantioselectivity [1]. One of such solutions is an use of a multilevel and cheap catalyst. Proline used as a catalyst is a substance of natural origin which was synthetically obtained by Willstätter who was carrying out research on hygric acid (Scheme 1) [10]. The cells of many organisms have a suitable enzymatic system essential for proline biosynthesis [15]. So far, three proline biosynthesis pathways have been described: from glutamate (Scheme 3 and 4), ornithine (Scheme 5 and 6), and arginine (Scheme 7) [16–28]. Proline which is obtained as a result of biosynthesis or supplementation is a substrate for many proteins. Characteristic and significant content (about 23%) of this amino acid was observed in collage. In cells proline can play an important role of osmoregulator [31–35] – a protective substance regulating the activity of such enzymes as catalase and peroxidase [36]. Proline as a secondary amine shows exceptional nucleophilicity facilitating imine and enamine formation. Used as a catalyst in aldol reaction makes with substrates like imine or enamine transition state imitating the activity of naturally occurring enzymes for this type of reaction, that is aldolases. In their research Hajos and Parrish, and Eder, Sauer and Wiechert used proline in intramolecular aldol reaction obtaining proper enones (Scheme 9) [60–62]. The process of intramolecular aldol reaction was used for a separation of racemic mixture of diketones (Scheme 10) [63, 64], cyclization of ortho-substituted aromatic aldehydes and ketones (Scheme 11) [65], synthesis of cyclic diketones (Scheme 13) [68] and domino reaction to obtain substituted cyclohexanones from beta-diketones and unsaturated ketones (Scheme 14) [69].
Dostawca treści:
Biblioteka Nauki
Artykuł
Wyświetlanie 1-10 z 17

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