699 research outputs found
Complexes of tetracyclines with divalent metal cations investigated by stationary and femtosecond-pulsed techniques
No full textPhysical Chemistry Chemical Physics
Volume 14, Issue 2, 14 January 2012, Pages 823-834
Complexes of tetracyclines with divalent metal cations investigated by stationary and femtosecond-pulsed techniques (Article)
Carlotti, B., Cesaretti, A., Elisei, F.
Chemistry Department, Centro di Eccellenza sui Materiali Innovativi Nanostrutturati (CEMIN), University of Perugia, via Elce di Sotto 8, 06123 Perugia, Italy
View references (56)
Abstract
Spectroscopic techniques both in steady-state (in absorption and emission) and pulsed (absorption of excited states with femtosecond resolution) conditions were used to study the complexation process between six molecules belonging to the tetracycline family and Mg 2+; in the case of TC the study was extended to the metal ions Ca 2+ and Cu 2+. The study was carried out in aqueous solution at various pH values, where one acid-base form of the substrate prevails over the others. The processing of experimental results, performed by means of Singular Value Decomposition and Global Analysis methods, allowed us to evaluate the extent of interaction through the association constants, to identify the number of equilibria present in solution and the stoichiometry (11 or 12) of the tetracyclinemetal ion complex, and to define the spectral and photophysical properties of the latter (in terms of fluorescence quantum yields, lifetimes and rate constants). In fact, the (allowed) radiative decay process is a minor root for the lowest excited state of the complexes which mainly decay to the ground state by internal conversion. Details of the complexation sites are proposed for the various protonated forms of tetracyclines, and for the various cations in the case of TC. In particular, the molecular structure seems to affect significantly the dynamics of interaction when the upper peripheral region of tetracycline is rich in additional hydroxyl groups. Moreover, the state of protonation of the substrate produces changes in the order of the complexation sites, whose affinity for the cation increases significantly when they are negatively charged owing to the loss of protons. Magnesium and calcium (hard cations) give similar interactions, at least in acid solution, while copper(ii) (borderline cation) binds more efficiently on different sites, thus forming complexes with different properties
Expression of calcitonin gene-related peptide in medullary thyroid cancer
No full textWe studied the expression of calcitonin (CT) and calcitonin gene-related peptide (CGRP) in 18 patients with medullary thyroid cancer (MTC) in the neoplastic (primary or metastatic) tissue by immunohistochemistry and in the plasma by radioimmunoassay. CT immunoreactivity was found in 100% of the primary and metastatic MTC, CGRP was expressed in 66% of the primary tumors and in 73% of the metastases. Both the number of positive cells and the degree of staining were always higher for CT than for CGRP staining. While plasma CT concentrations were always increased in patients with metastases, 3 patients with metastases had undetectable plasma CGRP levels. A positive correlation was found between plasma CT and CGRP levels. These data indicate that CGRP is frequently expressed in MTC sections and that plasma CGRP measurement is an additional marker for MTC, although has no advantage with respect to CT measurements in monitoring the progression of the disease
Obesity as a risk factor for thyroid cancer
No full textPurpose of review In this review, we evaluate recent findings related to the association between obesity and thyroid cancer. Recent findings During the last several decades, the prevalence of obesity and thyroid cancer have been increasing in parallel on a global scale. Current evidence suggests that the growing incidence of differentiated thyroid cancer (DTC) is pathogenically linked to the spread of obesity, but the biological mechanisms that may explain this connection have been only partially described. Furthermore, unlike other tumors, data on the impacts of obesity on the aggressiveness of DTC and response to treatment of DTC remain conflicting. Summary Emergent knowledge regarding the links between obesity and thyroid cancer suggests a relevant role for obesity as a risk factor for DTC, with no apparent impact on its aggressiveness
Homolytic vs Heterolytic C-H Bond Cleavage in Alkylaromatic Radical Cations. Formation of Diarylmethyl Cation in the Photoinduced Electron Transfer Reaction of Bis(4-methoxyphenyl)methane Sensitized by Chloranil
No full textEffect of the size of polycyclic aryl groups on the competition between adiabatic/diabatic photoisomerization mechanisms of: Cis -styrylarenes
No full textThe occurrence of adiabatic photoisomerization in the singlet manifold directly from 1Z∗ to 1E∗ has been found to be more common than expected. This mechanism has been experimentally evidenced through a detailed fluorimetric study for a large series of styrylarenes. Its weight on the overall cis-trans photoisomerization has been determined and found to increase when increasing the size of the polycyclic chromophore
Photoinduced substitution reactions in halothiophene derivatives. Steady state and laser flash photolytic studies
No full textSerum bone Gla-protein (osteocalcin) in patients with bone metastases from thyroid cancer
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