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991.
Antonio Tito Claudia Jimenez-Lopez Agnieszka Kowalska Stanisaw Wysocki 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2009,72(5):1000-1006
The formation of tolmetin/N-acetyl-l-tyrosine ethyl ester (ATEE) complex has been reported by means of both theoretical and experimental studies, including quantum mechanical calculations as well as UV–vis absorption, fluorescence and time-resolved spectroscopy measurements. It has been found that the fluorescence of ATEE is quenched due to the formation of a non-fluorescent complex between ATEE and tolmetin in the ground state. The geometrical parameters of ATEE/tolmetin complex have been determined with the use of the DFT method applying the B3LYP correlation-exchange functional and 6-31G(d) basis set. The results of experiments indicated the static ATEE quenching by tolmetin. Additionally, the experimental and theoretically predicted Gibbs free energy of complexation has been calculated. 相似文献
992.
Mixed complexes of the type: Zn(Hsal)2(2-MeHim)2, Zn(Han)2(2-MeHim)2, Cd(Hsal)2(2-MeHim)2, Cd(Han)2(2-MeHim)2, where Hsal=OHC6H4COO−, Han=NH2C6H4COO−, 2-MeHim=2-methylimidazol) have been synthesized and characterized by IR spectroscopic and X-ray diffraction studies. Single-crystal
X-ray structure of Cd(Hsal)2(2-MeHim)2 has been obtained. Thermal behaviour of the compounds was investigated by thermal analysis (TG, DTG, DTA). A coupled TG-MS
system was used to analyse the principal volatile products of complexes. Thermal decomposition pathways have been postulated. 相似文献
993.
Dynamical response of nanomechanical cantilever structures immersed in a viscous fluid is important to in vitro single-molecule force spectroscopy, biomolecular recognition of disease-specific proteins, and the study of microscopic protein dynamics. Here we study the stochastic response of biofunctionalized nanomechanical cantilever beams in a viscous fluid. Using the fluctuation-dissipation theorem we derive an exact expression for the spectral density of displacement and a linear approximation for resonance frequency shift. We find that in a viscous solution the frequency shift of the nanoscale cantilever is determined by surface stress generated by biomolecular interaction with negligible contributions from mass loading due to the biomolecules. 相似文献
994.
Aleksandra Owczarzy Andrzej Ziba Jadwiga Poycka Karolina Kulig Wojciech Rog Agnieszka Szkudlarek Magorzata Maciek-Jurczyk 《Molecules (Basel, Switzerland)》2021,26(16)
Plasma proteins play a fundamental role in living organisms. They participate in the transport of endogenous and exogenous substances, especially drugs. 5-alkyl-12(H)-quino[3,4-b][1,4]benzothiazinium salts, have been synthesized as potential anticancer substances used for cancer treatment. Most anticancer substances generate a toxic effect on the human body. In order to check the toxicity and therapeutic dosage of these chemicals, the study of ligand binding to plasma proteins is very relevant. The present work presents the first comparative analysis of the binding of one of the 5-alkyl-12(H)-quino[3,4-b][1,4]benzothiazinium derivatives (Salt1) with human serum albumin (HSA), α-1-acid glycoprotein (AGP) and human gamma globulin (HGG), assessed using fluorescence, UV-Vis and CD spectroscopy. In order to mimic in vivo ligand–protein binding, control normal serum (CNS) was used. Based on the obtained data, the Salt1 binding sites in the tertiary structure of all plasma proteins and control normal serum were identified. Both the association constants (Ka) and the number of binding site classes (n) were calculated using the Klotz method. The strongest complex formed was Salt1–AGPcomplex (Ka = 7.35·104 and 7.86·104 mol·L−1 at excitation wavelengths λex of 275 and 295 nm, respectively). Lower values were obtained for Salt1–HSAcomplex (Ka = 2.45·104 and 2.71·104 mol·L−1) and Salt1–HGGcomplex (Ka = 1.41·104 and 1.33·104 mol·L−1) at excitation wavelengths λex of 275 and 295 nm, respectively, which is a positive phenomenon and contributes to the prolonged action of the drug. Salt1 probably binds to the HSA molecule in Sudlow sites I and II; for the remaining plasma proteins studied, only one binding site was observed. Moreover, using circular dichroism (CD), fluorescence and UV-Vis spectroscopy, no effect on the secondary and tertiary structures of proteins in the absence or presence of Salt1 has been demonstrated. Despite the fact that the conducted studies are basic, from the scientific point of view they are novel and encourage further in vitro and in vivo investigations. As a next part of the study (Part 2), the second new synthetized quinobenzothiazine derivative (Salt2) will be analyzed and published. 相似文献
995.
Karolina Grabowska ukasz Pecio Agnieszka Galanty Pawe mudzki Wiesaw Oleszek Irma Podolak 《Molecules (Basel, Switzerland)》2021,26(16)
Two triterpene saponins, including a novel serjanic acid derivative, were isolated from Chenopodium hybridum L. (Amaranthaceae) aerial parts. Their structures were elucidated by a combination of spectroscopic methods (MS, 1D and 2D NMR). Both compounds were evaluated for cytotoxicity and selectivity on skin, prostate, gastrointestinal, thyroid and lung cancer cells. Their effect was dose and time-dependent with varied potency, the highest against prostate PC3 and melanoma WM793, where IC50 was lower than the reference drug doxorubicin. Structure–activity relationship is briefly discussed. 相似文献
996.
Agnieszka Ksiazek Piotr Borowski Krzysztof Wolinski 《Journal of magnetic resonance (San Diego, Calif. : 1997)》2009,197(2):153-160
Using quantum chemistry methods we have evaluated the solvent effects on the 14N NMR chemical shifts in five oxa- and oxadiazoles dissolved in twelve solvents. These solvents differ in their polarity with the dielectric constants varying from 2 to 80. Moreover, three of them have a hydrogen-bond donor character. All possible hydrogen-bonding in the water solution with the oxygen and nitrogen (hydrogen-acceptor) centers in oxazoles (2) and oxadiazoles (3) have been considered in our studies. It has been shown that both the pure solvent and hydrogen-bonding effects are significant and result in 14N magnetic shielding increase. In water solutions the pure solvent effect is larger than the hydrogen-bonding effect. In addition, the solvent effect has been analyzed in terms of its direct and indirect contributions. It should be emphasized that our theoretical results for 14N chemical shifts in oxa- and oxadiazoles remain in a very good agreement with the accurate experimental data. 相似文献
997.
We introduce a posteriori bounds for the eigenfunctions (eigenvalues) of non-selfadjoint diagonalizable PDE-eigenvalue problems which incorporates an inexact solution of the corresponding generalized matrix eigenvalue problem. The estimates combine the standard perturbation results with the saturation assumption for the eigenfunctions. (© 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
998.
999.
Agnieszka Kaamajska Miroslav Krbec 《Journal of Mathematical Analysis and Applications》2010,362(2):460-470
We consider a triple of N-functions (M,H,J) that satisfy the Δ′-condition, and suppose that an additive variant of interpolation inequality holds where , is an arbitrary set invariant with respect to external and internal dilations. We show that the above inequality implies its certain nonlinear variant involving the expressions and . Various generalizations of this inequality to the more general class of N-functions, measures and to higher order derivatives are also discussed and the examples are presented. 相似文献
1000.
Agnieszka B. Malinowska Delfim F.M. Torres 《Applied mathematics and computation》2010,217(3):1158-1162
The fundamental problem of the calculus of variations on time scales concerns the minimization of a delta-integral over all trajectories satisfying given boundary conditions. This includes the discrete-time, the quantum, and the continuous/classical calculus of variations as particular cases. In this note we follow Leitmann’s direct method to give explicit solutions for some concrete optimal control problems on an arbitrary time scale. 相似文献