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1.
Chemistry ; 29(7): e202202337, 2023 Feb 01.
Artigo em Inglês | MEDLINE | ID: mdl-36224099

RESUMO

Protonated achiral H2 TPPS4 spontaneously self-arranges at acids pH and high ionic strength to build mesoscopic J-aggregates that are intrinsically chiral. According to the symmetry rule aggregation leads to a racemate that, however, can be unbalanced by chemical (chiral pollutants) or physical stimuli (as vortexing the solution). Vortexing the title racemate, in principle, might either induce chiral separation or chiral enrichment. Indeed, herein it is shown that vortices enable the resolution of this racemic solution exploiting the tendency to deposit, onto the quartz cuvette walls, of the enantiomer favored by the stirring sense. Simultaneously, over time, it was found that the opposite chiral conformation becomes prevalent in solution realizing a significant enantiomeric resolution. Therefore, after removing all stirring-favored chiral J-aggregate from the solution, the recovering and isolating of the desired enantiomers from the cuvette walls was successfully obtained without complex procedures. In this sense, it has been demonstrated that the stirring forces are executively able to fulfil the chiral separation in H2 TPPS4 J-aggregates, employed as model of a self-assembled system in aqueous solution.

2.
Chemistry ; 26(16): 3515-3518, 2020 Mar 18.
Artigo em Inglês | MEDLINE | ID: mdl-31990096

RESUMO

The hierarchical assembly, in aqueous solution, of a new multi-metalloporphyrin/calixarene aggregate has been accomplished. In this supramolecular system transfer of chirality, from the outermost components to the central porphyrin reporter, takes place as a result of favorable and fully noncovalent long-range electronic communication.

3.
Front Chem ; 8: 616961, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-33409269

RESUMO

Chiral porphyrin hetero-aggregates, produced from meso-tetrakis(4-N-methylpyridyl) porphyrin H2T4 and copper(II) meso-tetrakis(4-sulfonatophenyl)porphyrin CuTPPS by an imprinting effect in the presence of L-3,4-dihydroxyphenylalanine (L-DOPA), are shown herein to serve as templates for the generation of chiral structures during the oxidative conversion of the amino acid to melanin. This remarkable phenomenon is suggested to involve the initial role of L-DOPA and related chiral intermediates like dopachrome as templates for the production of chiral porphyrin aggregates. When the entire chiral pool from DOPA is lost, chiral porphyrin hetero-aggregate would elicit axially chiral oligomer formation from 5,6-dihydroxyindole intermediates in the later stages of melanin synthesis. These results, if corroborated by further studies, may open unprecedented perspectives for efficient strategies of asymmetric melanin synthesis with potential biological and technological applications.

4.
Molecules ; 24(18)2019 Sep 14.
Artigo em Inglês | MEDLINE | ID: mdl-31540076

RESUMO

The dispersion of para-nitroaniline (p-NA) in water poses a threat to the environment and human health. Therefore, the development of functional adsorbents to remove this harmful compound is crucial to the implementation of wastewater purification strategies, and electrospun mats represent a versatile and cost-effective class of materials that are useful for this application. In the present study, we tested the ability of some polyethersulfone (PES) nanofibers containing adsorbed porphyrin molecules to remove p-NA from water. The functional mats in this study were obtained by two different approaches based on fiber impregnation or doping. In particular, meso-tetraphenyl porphyrin (H2TPP) or zinc(II) meso-tetraphenyl porphyrin (ZnTPP) were immobilized on the surface of PES fiber mats by dip-coating or added to the PES electrospun solution to obtain porphyrin-doped PES mats. The presence of porphyrins on the fiber surfaces was confirmed by UV-Vis spectroscopy, fluorescence measurements, and XPS analysis. p-NA removal from water solutions was spectrophotometrically detected and evaluated.


Assuntos
Compostos de Anilina/química , Nanofibras/química , Polímeros/química , Sulfonas/química , Águas Residuárias/química , Purificação da Água , Porfirinas/química
5.
Molecules ; 24(1)2018 Dec 27.
Artigo em Inglês | MEDLINE | ID: mdl-30591641

RESUMO

We report of the interactions between four amino acids lysine (Lys), arginine (Arg), histidine (His), and phenylalanine (Phe) with the J-aggregates of the protonated 5,10,15,20-tetrakis(4-sulfonatophenyl)-porphyrin H4TPPS. Several aspects of these self-assembled systems have been analyzed: (i) the chiral transfer process; (ii) the hierarchical effects leading to the aggregates formation; and, (iii) the influence of the amino acid concentrations on both transferring and storing chiral information. We have demonstrated that the efficient control on the J-aggregates chirality is obtained when all amino acids are tested and that the chirality transfer process is under hierarchical control. Finally, the chiral porphyrin aggregates obtained exhibit strong chiral inertia.


Assuntos
Aminoácidos/química , Porfirinas/química , Dicroísmo Circular , Ponto Isoelétrico , Espectrofotometria Ultravioleta , Estereoisomerismo
6.
Angew Chem Int Ed Engl ; 57(33): 10656-10660, 2018 08 13.
Artigo em Inglês | MEDLINE | ID: mdl-29939459

RESUMO

Cationic polylysine promotes, under neutral conditions, the spontaneous aggregation of opposite charged ZnTPPS in water. Spectroscopic investigations evidence a different preorganization of ZnTPPS onto the polypeptide matrix depending on the chain length. Spinodal decomposition theory in confined geometry is used to model this mechanism by considering the time evolution of a homogeneous distribution of randomly adsorbed particles (porphyrins) onto a rodlike polyelectrolyte (polymer) of variable length L.

7.
J Phys Chem B ; 119(14): 4898-904, 2015 Apr 09.
Artigo em Inglês | MEDLINE | ID: mdl-25781213

RESUMO

Cysteine is a sulfur-containing amino acid that easily coordinates to soft metal ions and grafts to noble metal surfaces. Recently, chiroptical activity of Ag(+)/cysteine coordination polymers has been widely studied, while, on the other hand, the appearance of a plasmon-enhanced circular dichroic signal (PECD) at the plasmonic spectral region (λ > 400 nm) has been observed for AgNPs capped with chiral sulfur-containing amino acids. These two events are both potentially exploited for sensing applications. However, the presence of Ag(+) ions in AgNP colloidal solution deals with the competition of cysteine grafting at the metal NP surface and/or metal ion coordination. Herein we demonstrate that the chiroptical activity observed by adding cysteine to AgNP colloids prepared by pulsed laser ablation in liquids (PLAL) is mainly related to the formation of CD-active Ag(+)/cysteine supramolecular polymers. The strict correlation between supramolecular chirality and hierarchical effects, driven by different chemical environments experienced by cysteine when different titration modalities are used, is pivotal to validate cysteine as a fast and reliable probe to characterize the surface oxidation of AgNPs prepared by pulsed laser ablation in liquids by varying the laser wavelengths.


Assuntos
Complexos de Coordenação/química , Cisteína/química , Polímeros/química , Prata/química , Nanopartículas Metálicas/química , Modelos Moleculares , Conformação Molecular , Nitrato de Prata/química , Estereoisomerismo
8.
J Colloid Interface Sci ; 437: 270-276, 2015 Jan 01.
Artigo em Inglês | MEDLINE | ID: mdl-25441360

RESUMO

Understanding the factors that governs spontaneous molecular transfer from solution to solid surface is fundamental to control noncovalent surface functionalization strategies, both in term of robustness and reproducibility. The comprehension of the nature of interaction involved in the mechanism of spontaneous adsorption will allow for a fine modulation of the deposition process. Herein, we provide experimental evidences to demonstrate that poly-lysine secondary structure represents a crucial factor profoundly influencing the outcome of its spontaneous deposition on quartz surfaces. In particular, random coil to α-helix transition is required to drive an effective transfer of the poly-l-lysine at the liquid-solid interface. ß-sheet deposition requires longer times to be accomplished, while random-coil deposition is highly unfavored. Accordingly, polylysine deposition on quartz and silicon is effective when α-helix is formed in solution (pH>10). This surface noncovalent functionalization represents a simple strategy to fabricate hybrid organic-inorganic or biocompatible materials. In fact, the proposed methodology is proven robust and repeatable and compatible for combination with solution or vapor phases (i.e. MOCVD) nanomaterial deposition approaches.


Assuntos
Polilisina/química , Dicroísmo Circular , Microscopia Eletrônica de Varredura , Estrutura Secundária de Proteína , Espectrofotometria Ultravioleta , Propriedades de Superfície
9.
Chem Commun (Camb) ; 50(39): 4993-6, 2014 May 21.
Artigo em Inglês | MEDLINE | ID: mdl-24504122

RESUMO

A chiral organic-inorganic hybrid material, based on a porous silicon surface functionalized with a chiral cavitand, was designed and synthesized. The affinity of this device in water toward a bromine-marked alkyl-ammonium salt has been evaluated using XPS detection. UV and CD measurements highlight the enantioselective extraction from a racemic mixture in water of the S-enantiomer of the selected guest (ee ≥ 80%).


Assuntos
Bromo/química , Éteres Cíclicos/química , Compostos de Amônio Quaternário/isolamento & purificação , Resorcinóis/química , Silício/química , Água/química , Dicroísmo Circular , Modelos Moleculares , Estrutura Molecular , Espectroscopia Fotoeletrônica , Porosidade , Compostos de Amônio Quaternário/química , Estereoisomerismo , Propriedades de Superfície
11.
Chirality ; 21(1): 92-6, 2009 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-18655011

RESUMO

The interactions between Lambda and Delta enantiomers of ruthenium(II)-phenanthroline cationic complex ([Ru(phen)(3)](2+)) and three anionic porphyrins have been characterized by absorption, circular dichroism (CD), fluorescence, and resonance light scattering (RLS). The three porphyrins used in this study have been chosen for the different number (two or four) and reciprocal (symmetrical, cis or trans) disposition of the anionic (4-sulphonatophenyl) peripheral groups in the meso positions. All the techniques evidence the formation of inorganic-organic hybrids. In particular, CD and fluorescence measurements show that the inorganic moiety is able to transfer to porphyrins not only chirality (as shown from the appearance of an induced CD signal (ICD) in the absorption region of porphyrins) but, most likely, also energy.

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