177,974 research outputs found
Materiali Organici p-Coniugati Chirali
No full textThe research conducted during the Ph.D. is divided into two main lines, both joined together by the key role played by chiral p-conjugated synthons within novel supramolecular systems. The first part involved the synthesis and utilization of 1,1'-binaphthylic derivatives. Starting from them, new chiral molecular cages capable of acting as chiroptical sensors for an important radioactive environmental pollutant (99TcO4-) were synthesized and studied (Chapter 2, in collaboration with Prof. Valeria Amendola, Pavia). The interaction between the cage and anion, mainly caused by hydrogen bonds, is transduced into a large modulation of the chiroptical signal.1 In chapter 3, in collaboration with Prof. Dominique Armspach (University of Strasbourg), new cyclodextrins "capped" with atropoisomeric 1,1'-biphenylic systems were synthesized. The process of chirality transfer from cyclodextrin (point chirality) to the biphenyl moiety (axial chirality) was investigated in detail, both in solution and in the solid state. The key role of intramolecular hydrogen bonds responsible for the efficient chirality transfer was demonstrated, and finally the temperature-dependent chiroptical activity of such systems was studied. The second research line involved the synthesis and utilization of triptycene synthons.2 New triptycene-fused quinacridone dyes were synthesized and studied, following our general strategy of merging nonplanar p-conjugated synthons and high-performance pigments (Chapter 4). Subsequently, after several unsuccessful attempts to resolve crucial chiral triptycene intermediates, such resolution was achieved by using chiral HPLC, in collaboration with the research group of Prof. Roberto Cirilli (chapter 5).2 Finally (chapter 6), in collaboration with Prof. Amendola's research group, new triptycene-fused benzimidazoles were synthesized. These derivatives were successfully used for the self-assembly via hydrogen bonding of chiral polymers consisting of triptycene-benzimidazoles and chiral (non-chromophoric) carboxylic acids. In this case, chirality is transferred via non-covalent interactions from simple chiral carboxylic acids to an equilibrating mixture (resulting from tautomeric equilibria) of triptycene/benzimidazole isomers. The resulting supramolecular structures proved to be capable of emitting circularly polarized light with glum dissymmetry factors up to 6*10-3.
References and Pubblications
1) R. Mobili ±, G. Preda ±,S. La Cognata, L. Toma, D. Pasini, V. Amendola, Chem. Commun., 2022, 58, 3897–3900.
2) G. Preda, A. Nitti, D. Pasini, ChemistryOpen 2020, 9, 719–727.
3) A. Rosetti, G. Preda, C. Villani, M. Pierini, D. Pasini, R. Cirilli, Chirality, 2021; 33, 883–890.La ricerca condotta durante il dottorato è divisa in due filoni principali, entrambi accumunati dal ruolo chiave rivestito da sintoni -coniugati chirali all’interno nuovi sistemi supramolecolari. Il primo filone ha riguardato la sintesi e l’utilizzo di derivati 1,1’-binaphthylic. A partire da essi, sono stati sintetizzati e studiati nuove gabbie molecolari in grado agire come sensori chirottici per un importante inquinante ambientale radioattivo (99TcO4-) (capitolo 2, in collaborazione con la Prof.ssa Valeria Amendola, Pavia). L’interazione tra gabbia e anione, causata principalmente da legami a idrogeno, viene tradotta in ampio cambiamento del segnale (chir)ottico.1 Nel capitolo successivo, in collaborazione con il Prof. Dominique Armspach (Università di Strasburgo) sono stati sintetizzate ciclodestrine “cappate” con sistemi atropoisomerici di tipo 1,1’-bifenilico. Il processo di trasferimento di chiralità dalla ciclodestrina (chiralità puntuale) alla prozione bifenilica (chiralità assiale) è stato studiato in dettaglio, sia in soluzione che a stato solido. Il ruolo chiave dei legami legami idrogeno intramolecolari responsabili dell’efficiente trasferimento di chiralità è stato dimostrato ed infine la attività chirottica temperatura dipendente di tali sistemi è stata studiata. Il secondo filone di ricerca ha riguardato la sintesi e l’utilizzo di sintoni tripticenici.2 Sono stati sintetizzati e studiati nuovi coloranti triptycene-fused quinacridone, seguendo la nostra strategia generale che prevede la fusione di sintoni -coniugati non planari e pigmenti ad altre prestazioni. Successivamente (capitolo 5), dopo diversi tentativi di risoluzione falliti, la risoluzione di cruciali sintoni tripticenici chirali è stata ottenuta mediante utilizzo di HPLC chirale, in collaborazione con il gruppo di ricerca del Prof. Roberto Cirilli (Università La Sapienza, Roma).3 Infine, in collaborazione con il gruppo di ricerca della Prof. Amendola, sono stati sintetizzati nuovi derivati di tripticene/benzimidazolo. Tali derivati sono stati impiegati con successo per l’autoassemblaggio via legame a idrogeno di polimeri chirali costituiti da derivati tripticene/benzimidazolo e acidi carbossilici chirali (non cromoforici). In questo caso la chiralità viene trasferita tramite interazioni non covalenti da semplici acidi carbossibili chirali a una miscela in equilibrio (derivante da equilibri tauromerici) di isomeri tripticene/benzimidazolo. Le strutture supramolecoalri così ottenute si sono rivelate in grado emettere luce polarizzata circolarmente con fattori di disimmetria glum fino a 6*10-3.
Referenze e Pubblicazioni
1) R. Mobili ±, G. Preda ±,S. La Cognata, L. Toma, D. Pasini, V. Amendola, Chem. Commun., 2022, 58, 3897–3900.
2) G. Preda, A. Nitti, D. Pasini, ChemistryOpen 2020, 9, 719–727.
3) A. Rosetti, G. Preda, C. Villani, M. Pierini, D. Pasini, R. Cirilli, Chirality, 2021; 33, 883–890
Săpăturile arheologice de la Sîncrăieni (r. Ciuc, Reg. Autonomă Maghiară) / Les fouilles archéologiques de Sîncrăieni
No full textPreda Constantin. Săpăturile arheologice de la Sîncrăieni (r. Ciuc, Reg. Autonomă Maghiară) / Les fouilles archéologiques de Sîncrăieni. In: Materiale şi cercetări arheologice, N°6 1959. pp. 825-869
Săpăturile de la Spanţov (r. Olteniţa, reg. Bucureşti) / Les fouilles de Spanţov
No full textMorintz Sebastian, Preda Constantin. Săpăturile de la Spanţov (r. Olteniţa, reg. Bucureşti) / Les fouilles de Spanţov. In: Materiale şi cercetări arheologice, N°5 1959. pp. 163-173
A version of a theorem of R. Datko for nonuniform exponential contractions
No full textAbstractWe point out versions of a well-known theorem of R. Datko for nonuniform exponential contractions. More precisely, we obtain theorems that characterize the nonuniform exponential stability and the nonuniform exponential dichotomy for nonuniform exponential contractions. Thus, we generalize the results in Datko (1972) [8] and Preda and Megan (1985) [14]
Săpăturile de salvare de la Alexandria (r. Alexandria, reg. Bucureşti) / Les fouilles de sauvegarde d’Alexandria
No full textMitrea Bucur, Preda Constantin. Săpăturile de salvare de la Alexandria (r. Alexandria, reg. Bucureşti) / Les fouilles de sauvegarde d’Alexandria. In: Materiale şi cercetări arheologice, N°5 1959. pp. 175-181
PREDA: An R-package to identify regional variations in genomic data
No full textChromosomal patterns of genomic signals represent molecular ngerprints that may reveal how the local structural organization of a genome impacts the functional control mechanisms. Thus, the integrative analysis of multiple sources of genomic data and information deepens the resolution and enhances the interpretation of stand-alone high-throughput data. In this note, we present PREDA (Position RElated Data Analysis), an R package for detecting regional variations in genomics data. PREDA identies relevant chromosomal patterns in high-throughput data using a smoothing approach that accounts for distance and density variability of genomics features. Custom-designed data structures allow efciently managing diverse signals in different genomes. A variety of smoothing functions and statistics empower exible and robust workows. The modularity of package design allows an easy deployment of custom analytical pipelines. Tabular and graphical representations facilitate downstream biological interpretation of results. © The Author 2011. Published by Oxford University Press. All rights reserved
PREDA: an R-package to identify regional variations in genomic data
No full textSUMMARY:Chromosomal patterns of genomic signals represent molecular fingerprints that may reveal how the local structural organization of a genome impacts the functional control mechanisms. Thus, the integrative analysis of multiple sources of genomic data and information deepens the resolution and enhances the interpretation of stand-alone high-throughput data. In this note, we present PREDA (Position RElated Data Analysis), an R package for detecting regional variations in genomics data. PREDA identifies relevant chromosomal patterns in high-throughput data using a smoothing approach that accounts for distance and density variability of genomics features. Custom-designed data structures allow efficiently managing diverse signals in different genomes. A variety of smoothing functions and statistics empower flexible and robust workflows. The modularity of package design allows an easy deployment of custom analytical pipelines. Tabular and graphical representations facilitate downstream biological interpretation of results.AVAILABILITY:PREDA is available in Bioconductor and at http://www.xlab.unimo.it/PREDA
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