81 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
The Role of pH in Modulating the Electronic State Properties of Minocycline Drug and Its Inclusion within Micellar Carriers
No full textA detailed investigation of the spectral and photophysical properties of minocycline (MC) in water at different pHs, solvents of different polarity, and micellar surfactant solutions was carried out in this study. An unusual behavior was highlighted with respect to other tetracyclines due to the presence of an additional dimethylamino group in the MC molecular structure. In particular, four equilibrium constants associated with monodeprotonation reactions were characterized by steady-state spectroscopy. Femtosecond time resolved pump probe and fluorescence up-conversion measurements allowed the dynamics of the lowest excited singlet state of the five different acid base species of MC to be characterized in terms of lifetimes and transient spectra. Two emissive species associated with keto enol tautomerism resulting from excited-state intramolecular proton transfer (ESIPT) were revealed with time constants of a few and tens of picoseconds. TD-DFT quantum mechanical calculations were also performed to define the state order and nature of the differently protonated species, together with their absorption spectra. The role of pH proved to be fundamental in modulating the drug charge and therefore the interaction with cationic micelles where the neutral form of MC, that is the biologically active one, resulted efficiently included
Esercizio di lettura: il prodigio delle ragazzine rese strabiche
No full textA specific passage of the Life of Symeon Salos (pp. 157, 17 - 158, 8 in the critical edition of Rydén) is dealt at length, especially from the linguistic and stylistic point of view, in order to catch the peculiar features of that author. It is an useful 'exercise' for students of Late Greek
Per Leone di Centuripe e i suoi encomi di s. Nettario (BHG 2284) e di s. Giacomo Maggiore (BHG 786D)
No full textLeon of Sicily or of Centuripe is the enigmatic author of two hagiographical texts, the Encomium to St Nektarios, patriarch of Constantinople, edited by F. Halkin, and the still unedited Hypomnema to St James the Apostle and brother of St John the Evangelist (BHG 2284 and 768d). Enrica Follieri, who is the only scholar to have written extensively on Leon, plausibly dates him between the second half of the eleventh and the early twelfth century. This article delves into the places where he might have taught as a grammatikos (southern Italy-Sicily and Constantinople) and comments on the titles and literary aspects of his extant work. The discussion focuses on his use of prosimetrum (here the alternation of segments of prose with verse), a rare feature in Greek hagiography itself as well as in Byzantine literature at large
Introduzione storico-letteraria
No full textSort of book-within-the-book, this text (almost 200 pages with 1000 footnotes) is the first part of the exhaustive prolegomena to the critical edition of Eustathios' commentary. It gives full information (at the light of international bibliography) about Eustathios' life and works as well as about the literary genre of the commentaries on liturgical canons, the structure of Eustathios' exegesis and its intended audience, the author's philological approach to the text and its author, the source exploited by Eustathios, his judgement about the text, and more
Oltre la «polis felice e imperiale». Alcuni elementi di spatiality letteraria nella Vita di santa Teofano (BHG 1794)
No full textA study of the spatial implications present in the text of the Life of St. Theophano (BHG 1794) may give a contribution to a deeper understanding of the aims of the author
Photoinduced Intramolecular Charge Transfer and Hyperpolarizability Coefficient in Push‐Pull Pyridinium Salts with Increasing Strength of the Acceptor Group
No full textThe synthesis of three push-pull cationic dyes is reported here together with a photophysical study carried out by stationary and ultrafast spectroscopies. The hyperpolarizability (β) values of the three molecules have been estimated through a simple solvatochromic method based on conventional, low-cost equip- ment, which had been tested previously with success in our laboratory. The investigated pyridinium salts showing strong negative solvatochromism bear the same piperidine ring as a strong electron-donor group and the same thiophenes as electron-rich π-linkers, but differ in terms of the N-substituent on the electron-acceptor pyridinium unit, namely N-methyl in compound A, N-pyrimidin-2yl in B and N-2,4-dinitrophenyl in C.
The derived β values were found to increase (in the order A< B < C) along with the increasing electron-acceptor strength of the pyridinium substituent, with the highest polarizability being estimated for the derivative bearing the strongest electron- withdrawing substituent dinitrobenzene. State-of-the-art femto- second transient absorption measurements evidenced fast kinetics and dynamics in the singlet excited state in agreement with charge transfer (CT) processes promoted by excitation, with a proper ICT state observed in the case of C. This finding confirms the efficiency of photoinduced intramolecular CT as a significant factor that affects the NLO response
Microplastic and Extracellular Vesicle Interactions: Recent Studies on Human Health and Environment Risks
No full textMicroplastics (MPs) are widespread environmental pollutants that have drawn significant attention due to their possible health risks to humans and animals, as well as their extensive presence in ecosystems. Recent growing evidence highlights a remarkable relationship between MPs and extracellular vesicles (EVs), nanoscale particles involved in intercellular communication. The purpose of this review was to investigate how the relationships between MPs and EVs can affect cellular functions and how this interaction could impact environmental conditions leading to broader ecological risks. The interaction patterns and bioactivity of both MPs and EVs are strongly influenced by biophysical characteristics such as hydrophobicity, surface charge, and particle size, which have received particular attention from the scientific community. Recent studies indicate that MPs affect EV distribution and their capacity to function appropriately in biological systems. Additionally, MPs can modify the molecular cargo of EVs, which may result in alterations of cell signaling pathways. Understanding the interactions between MPs and EVs could provide important opportunities to comprehend their potential effects on human health and environmental systems, especially when it comes to cancer development, endocrine, metabolic, and inflammatory disorders, and ecological disruptions. This review emphasizes the necessity of multidisciplinary research to clarify the molecular and biophysical mechanisms regulating the interaction between MPs and EVs
"Vigrino" e gli altri. Considerazioni sui nomi di persona nella Vita di Andrea salos (BHG 115z)
No full textIl testo è dedicato a una indagine storico-letteraria sulla Vita di Andrea il Folle (BHG 115z), testo agiografico bizantino ascritto alla metà del X secolo, opera di un autore che si presenta come “Niceforo prete di Santa Sofia”. Egli distingue il suo santo (non una figura storica ma una creazione letteraria dell’autore) dalla folla anonima di Costantinopoli, la Città che lo circonda, in tal modo sottolineando la solitudine del protagonista. Intorno ad Andrea, solo una ristrettissima cerchia di personaggi è connotata dalla esplicita individuazione in base al nome proprio. Si tratta di nomi che a una lettura attenta appaiono emblematici e cifrati, carichi di significati nascosti. Tra essi è particolarmente significativo il nome inusitato di “Vigrino”, attribuito a un mago che agisce per influsso demoniaco. Alla luce della propensione dell’autore per i puns linguistici e per i giochi di parola, e considerato anche l’elemento paleografico, si propone di leggere il nome come una studiata deformazione di “Virgilio”, la cui fama di mago pervase il Medioevo bizantino oltre che quello occidentale.The byzantine hagiographical text known as "Life of Andrew salos" presents a wide range of characters, but only few of them are labelled with proper name. This is a literary choice in order to outline the loneliness of the hero of the text. Given the passion of the author for literary puns, these few names seem to be loaded with a series of implications, and this is especially true of the wizard "Vigrinos" - an important character in the strategy of the text - whose name is a sort of "riddle" for the scholars. My paper suggests on historical-cultural as well as palaeographical basis that "Vigrinos" is a literary metamorphosis of "Virgilios", the Latin poet who was famous as a sorcerer not only in the West but also in the Byzantine East
Esercizio di lettura: il prodigio delle ragazzine rese strabiche
No full textA specific passage of the Life of Symeon Salos (pp. 157, 17 - 158, 8 in the critical edition of Rydén) is dealt at length, especially from the linguistic and stylistic point of view, in order to catch the peculiar features of that author. It is an useful 'exercise' for students of Late Greek
- …
