Search results for "Spectrophotometry"
showing 10 items of 644 documents
Interactions of zinc octacarboxyphthalocyanine with selected amino acids and with albumin
2015
Effect of selected amino acids (glycine, l-histidine, l-cysteine, l-serine, l-tryptophan) and albumin on the spectroscopic properties and photostability of zinc octacarboxyphthalocyanine (ZnPcOC) was explored in the phosphate buffer at a pH of 7.0. The photodegradation of ZnPcOC alone and in the presence of amino acids or albumin has been investigated in aqueous phase using UV-366 nm and daylight irradiation. Kinetic analysis showed that the interaction with amino acids or albumin enhances the photostability of ZnPcOC. To answer the question of how zinc phthalocyanine interacts with amino acids extensive DFT calculations were performed. Analysis of the optimized geometry features of ZnPcOC:…
Structural and Molecular Characterization of meso-Substituted Zinc Porphyrins: A DFT Supported Study
2011
Structural parameters of a range of over 100 meso-substituted zinc porphyrins were reviewed and compared to show how far the nature of the functional group may affect the interatomic distances and bond angles within the porphyrin core. It was proved that even despite evident deformations of the molecular structure, involving twisting of the porphyrin's central plane, the coupled π-bonding system remains flexible and stable. DFT calculations were applied to a number of selected porphyrins representative for the reviewed compounds to emphasize the relevance of theoretical methods in structural investigations of complex macrocyclic molecular systems. Experimental and DFT-simulated IR spectral …
Thermodynamic studies of actinide complexes. 1. A reappraisal of the solution equilibria between plutonium(IV) and ethylenediaminetetraacetic acid (E…
2007
Abstract A detailed reevaluation of the complexation equilibria of plutonium(IV) with the polyaminocarboxylic sequestering agent EDTA4− has been performed in 1 M (H,K)NO3 media at 298 K by means of visible absorption spectrophotometry and glass-electrode potentiometry at millimolar concentration levels. The high binding affinity even under strongly acidic conditions supports the exclusive formation of the neutral Pu(EDTA) complex over the range 0.01 ≤ [H+] ≤ 0.9 M with an apparent formation constant of log β110 = 25.8(1) at 0.9 M HNO3. Extrapolation to zero ionic strength using the SIT approach provides the first ever-reported NEA–TDB compliant estimate of β 110 0 ( log β 110 0 = 32.2 ( 3 )…
Thermo-setting glass ionomer cements promote variable biological responses of human dental pulp stem cells.
2017
To evaluate the in vitro cytotoxicity of Equia Forte (GC, Tokyo, Japan) and Ionostar Molar (Voco, Cuxhaven, Germany) on human dental pulp stem cells (hDPSCs).hDPSCs isolated from third molars were exposed to several dilutions of Equia Forte and Ionostar Molar eluates (1/1, 1/2 and 1/4). These eluates were obtained by storing material samples in respective cell culture medium for 24h (n=40). hDPSCs in basal growth culture medium were the control. Cell viability and cell migration assays were performed using the MTT and wound-healing assays, respectively. Also, induction of apoptosis and changes in cell phenotype were evaluated by flow cytometry. Changes in cell morphology were analysed by im…
Synthesis and molecular properties of donor–π-spacer–acceptor ynamides with up to four conjugated alkyne units
2010
A set of push-pull ynamides with up to four conjugated triple bonds has been synthesized and the molecular properties of these new carbon rods have been characterised showing effective intramolecular charge transfers and high values for the change of the electrical dipole moment after transition from the ground to the Franck-Condon excited state.
Communication: Electronic UV-Vis transient spectra of the ·OH reaction products of uracil, thymine, cytosine, and 5,6-dihydrouracil by using the comp…
2013
Addition of ∙OH radicals to pyrimidine nucleobases is a common reaction in DNA/RNA damage by reactive oxygen species. Among several experimental techniques, transient absorption spectroscopy has been during the last decades used to characterize such compounds. Discrepancies have however appeared in the assignment of the adduct or adducts responsible for the reported transient absorption UV-Vis spectra. In order to get an accurate assignment of the transient spectra and a unified description of the absorption properties of the ∙OH reaction products of pyrimidines, a systematic complete active space self-consistent field second-order perturbation (CASPT2//CASSCF) theory study has been carried…
Quantitative Analysis of the Interactions of Metal Complexes and Amphiphilic Systems: Calorimetric, Spectroscopic and Theoretical Aspects.
2022
Metals and metal-based compounds have many implications in biological systems. They are involved in cellular functions, employed in the formation of metal-based drugs and present as pollutants in aqueous systems, with toxic effects for living organisms. Amphiphilic molecules also play important roles in the above bio-related fields as models of membranes, nanocarriers for drug delivery and bioremediating agents. Despite the interest in complex systems involving both metal species and surfactant aggregates, there is still insufficient knowledge regarding the quantitative aspects at the basis of their binding interactions, which are crucial for extensive comprehension of their behavior in sol…
Reversible Dioxygen Binding and Phenol Oxygenation in a Tyrosinase Model System
2000
The complex [Cu2(L-66)]2+ (L-66 = a,a'-bis¿bis[2-(1'-methyl-2'-benzimidazolyl)ethyl]amino¿-m-xylene) undergoes fully reversible oxygenation at low temperature in acetone. The optical [lambda(max) = 362 (epsilon 15000), 455 (epsilon 2000), and 550 nm (epsilon 900M(-1)cm(-1))] and resonance Raman features (760 cm(-1), shifted to 719cm(-1)(-1) with 18O2) of the dioxygen adduct [Cu2(L-66)(O2)]2+ indicate that it is a mu-eta2:eta2-peroxodicopper(II) complex. The kinetics of dioxygen binding, studied at - 78 degrees C, gave the rate constant k1 = 1.1M(-1) 5(-1) for adduct formation, and k(-1) =7.8 x 10(-5)s(-1), for dioxygen release from the Cu2O2 complex. From these values, the O2 binding consta…
Background Correction and Multivariate Curve Resolution of Online Liquid Chromatography with Infrared Spectrometric Detection
2011
J.K. acknowledges the “V Segles” grant provided by the University of Valencia to carry out this study. Authors acknowledge the financial support of Ministerio de Educación y Ciencia (Projects AGL2007-64567 and CTQ2008-05719/BQU) and Conselleria d'Educació de la Generalitat Valenciana (Project PROMETEO 2010-055).
Determination of vinegar acidity by attenuated total reflectance infrared measurements through the use of second-order absorbance-pH matrices and par…
2007
Univariate (zero-order), multivariate (first-order) and multiway (second-order) calibrations were assayed for the determination of vinegar acidity using a mechanized procedure based upon vibrational spectroscopy and the emerging multicommutation methodology. The second-order methodology relies on the use of a flow system based on multicommutation and binary sampling. The flow network comprises a set of three-way solenoid valves, computer-controlled to provide facilities to handle the sample and to generate a time-dependent pH gradient using two carrier solutions. The procedure is based on the volumetric fraction variation approach that maintains the same volume of sample solution and dynami…