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Sci Rep ; 9(1): 14509, 2019 Oct 10.
Artigo em Inglês | MEDLINE | ID: mdl-31601826


Assembly of interacting molecular spins is an attractive candidate for spintronic and quantum computing devices. Here, we report on-surface chemical assembly of aminoferrocene molecules on a graphene oxide (GO) sheet and their magnetic properties. On the GO surface, organometallic molecules having individual spins through charge transfer between the molecule and the sheet are arranged in nanoclusters having diameters of about 2 nm. The synthetic fine tuning of the reaction time enables to change the interspacing between the nanoclusters, keeping their size intact. Their magnetism changes from paramagnetic behavior to collective one gradually as the interspacing decreases. The creation of collective nature among weakly interacting molecular spins through their nanoscale arrangement on the GO surface opens a new avenue to molecular magnetism.

ACS Appl Mater Interfaces ; 8(3): 2380-92, 2016 Jan 27.
Artigo em Inglês | MEDLINE | ID: mdl-26736132


Fabrication of protein-inorganic hybrid materials of innumerable hierarchical patterns plays a major role in the development of multifunctional advanced materials with their improved features in synergistic way. However, effective fabrication and applications of the hybrid structures is limited due to the difficulty in control and production cost. Here, we report the controlled fabrication of complex hybrid flowers with hierarchical porosity through a green and facile coprecipitation method by using industrial waste natural silk protein sericin. The large surface areas and porosity of the microsize hybrid flowers enable water purification through adsorption of different heavy metal ions. The high adsorption capacity depends on their morphology, which is changed largely by sericin concentration in their fabrication. Superior adsorption and greater selectivity of the Pb(II) ions have been confirmed by the characteristic growth of needle-shaped nanowires on the hierarchical surface of the hybrid flowers. These hybrid flowers show excellent thermal stability even after complete evaporation of the protein molecules, significantly increasing the porosity of the flower petals. A simple, cost-effective and environmental friendly fabrication method of the porous flowers will lead to a new solution to water pollution required in the modern industrial society.

Metais Pesados/isolamento & purificação , Sericinas/química , Sericinas/síntese química , Adsorção , Animais , Cádmio/isolamento & purificação , Chumbo/isolamento & purificação , Mercúrio/isolamento & purificação , Microscopia Eletrônica de Varredura , Estabilidade Proteica , Sericinas/ultraestrutura , Espectroscopia de Infravermelho com Transformada de Fourier , Temperatura
Chem Commun (Camb) ; 50(83): 12556-9, 2014 Oct 25.
Artigo em Inglês | MEDLINE | ID: mdl-25198430


Morphological transition and the fabrication of unique architectures through molecular self-assembly of dipeptides are caused by the formation of a small nucleus in artificial supersaturation, achieved by quick drying of the solvent due to the local Joule heating. The growth mechanism of "diatom-like" porous microspheres and microtubes is proposed on the basis of several new techniques developed in the study.

Dipeptídeos/química , Dessecação , Calefação , Microesferas , Microtecnologia , Porosidade , Solventes/química
Small ; 8(7): 984-90, 2012 Apr 10.
Artigo em Inglês | MEDLINE | ID: mdl-22323423


An opioid (leucine-enkephalin) conformational analogue forms diverse nanostructures such as vesicles, tubes, and organogels through self-assembly. The nanovesicles encapsulate the natural hydrophobic drug curcumin and allow the controlled release through cation-generated porogens in membrane mimetic solvent.

Encefalina Leucina/química , Nanoestruturas/química , Nanotecnologia/métodos , Curcumina/administração & dosagem , Curcumina/química , Portadores de Fármacos/química , Microscopia de Força Atômica , Microscopia Eletrônica de Varredura , Microscopia Eletrônica de Transmissão , Microscopia de Fluorescência , Nanoestruturas/ultraestrutura
J Nanosci Nanotechnol ; 11(8): 6747-56, 2011 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-22103076


A set of backbone modified peptides of general formula Boc-Xx-m-ABA-Yy-OMe where m-ABA is meta-aminobenzoic acid and Xx and Yy are natural amino acids such as Phe, Gly, Pro, Leu, Ile, Tyr and Trp etc., are found to self-assemble into soft nanovesicular structures in methanol-water solution (9:1 by v/v). At higher concentration the peptides generate larger vesicles which are formed through fusion of smaller vesicles. The formation of vesicles has been facilitated through the participation of various noncovalent interactions such as aromatic pi-stacking, hydrogen bonding and hydrophobic interactions. Model study indicates that the pi-stacking induced self-assembly, mediated by m-ABA is essential for well structured vesicles formation. The presence of conformationally rigid m-ABA in the backbone of the peptides also helps to form vesicular structures by restricting the conformational entropy. The vesicular structures get disrupted in presence of various salts such as KCI, CaCl2, N(n-Bu)4Br and (NH4)2SO4 in methanol-water solution. Fluorescence microscopy and UV studies reveal that the soft nanovesicles encapsulate organic dye molecules such as Rhodamine B and Acridine Orange which could be released through salts induced disruption of vesicles.

Nanoestruturas , Oligopeptídeos/química , Sais/química , Cristalografia por Raios X , Microscopia de Força Atômica , Microscopia Eletrônica/métodos , Microscopia de Fluorescência , Modelos Moleculares , Espectrofotometria Infravermelho , Termogravimetria
Protein Pept Lett ; 16(9): 1063-73, 2009.
Artigo em Inglês | MEDLINE | ID: mdl-19508219


Single crystal X-ray diffraction studies and solvent dependent (1)H NMR titrations reveal that a set of four tetrapeptides with general formula Boc-Xx(1)-Aib(2)-Yy(3)-Zz(4)-OMe, where Xx, Yy and Zz are coded L-amino acids, adopt equivalent conformations that can be described as overlapping double turn conformations stabilized by two 4-->1 intramolecular hydrogen bonds between Yy(3)-NH and Boc C=O and Zz(4)-NH and Xx(1)C=O. In the crystalline state, the double turn structures are packed in head-to-tail fashion through intermolecular hydrogen bonds to create supramolecular helical structures. Field emission scanning electron microscopic (FE-SEM) images of the tetrapeptides in the solid state reveal that they can form flat tape-like structures. The results establish that synthetic Aib containing supramolecular helices can form highly ordered self-aggregated amyloid plaque like human amylin.

Ácidos Aminoisobutíricos/química , Oligopeptídeos/química , Amiloide/química , Cristalização , Cristalografia por Raios X , Polipeptídeo Amiloide das Ilhotas Pancreáticas , Microscopia Eletrônica de Varredura , Ressonância Magnética Nuclear Biomolecular , Conformação Proteica , Estrutura Secundária de Proteína