Self-Assembly of Discrete Cyclic Nanostructures Mediated by Transition Metals

Leininger, Stefan; Olenyuk, Bogdan; Stang, Peter J.

doi:10.1021/cr9601324

Cited by 3,466 publications

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“…In our experience, the encapsulation of guest molecules stabilizes the host assemblies, thus enabling ionization without fragmentation. The binding constants for the different guest molecules used in this study were previously determined by NMR spectroscopy: Me 4 (the binding constant for Cp* 2 Co ϩ could not be determined by NMR spectroscopy due to insolubility upon addition of more than one equivalent of guest molecules). The large binding constant of Et 4 N ϩ and the high stability of these host-guest complexes might explain the greater reliability for obtaining consistent mass spectral data, whereas previous detection of weaker bound host-guest complexes were strongly dependent on experimental conditions [6].…”

Section: Resultsmentioning

confidence: 99%

“…The formation of discrete molecular architectures relies on labile coordinative bonds that allow for self-correction and exclusive formation of the thermodynamic product. A great variety of self-assembled structures of different molecular sizes and shapes is present in the literature [1][2][3][4][5]. Here, we focus on contributions to this field made by Raymond and coworkers [2, 6 -10].…”

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Characterization of self-assembled supramolecular [Ga₄L₆] host-guest complexes by electrospray ionization mass spectrometry

Andersen

Seeber

Fiedler

et al. 2006

J. Am. Soc. Mass Spectrom.

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Self-assembled supramolecular host-guest complexes have been characterized by electrospray ionization mass spectrometry. The spectra obtained by use of a Q-TOF instrument equipped with a Z-spray ion source show primarily the 3-and 4-charge states of the assemblies. The assemblies have the general formula [guest ʚ Ga 4 L 6 ] 11Ϫ where L represents the chelating bidentate catechol ligand 1,5-bis(2=,3=-dihydroxy-benzamido)naphthalene and guests are tetramethyl ammonium (Me 4 N ϩ ), tetraethyl ammonium (Et 4 N ϩ ), tetra-n-propyl ammonium (Pr 4 N ϩ ) and decamethylcobaltocenium (Cp* 2 Co ϩ ) cations. For the first time, the mass spectrum of the empty assembly [Ga 4 L 6 ] 12Ϫ is reported. This article also reports that provided the electrospray ion source is capable of preserving noncovalent interactions, it is possible to observe host-guest complexes containing both weak binding guests as well as sterically demanding guests in the mass spectra. The present data suggest that electrospray mass spectrometry is a powerful tool for characterization of supramolecular host-guest complexes. ( I n the area of supramolecular chemistry, metal-ligand interactions have been exploited to design highly symmetric closed shell structures that selfassemble from simple metal and ligand components. The formation of discrete molecular architectures relies on labile coordinative bonds that allow for self-correction and exclusive formation of the thermodynamic product. A great variety of self-assembled structures of different molecular sizes and shapes is present in the literature [1][2][3][4][5]. Here, we focus on contributions to this field made by Raymond and coworkers [2, 6 -10]. The common theme in these metal-ligand assemblies is the presence of chelating bidentate catechol amide ligands, which bear certain geometric constraints upon coordination to octahedral metal centers resulting in M 4 L 6 coordination tetrahedra (Figure 1). The complexes are highly charged, rendering them soluble in polar solvents such as water and methanol, yet contain hydrophobic cavities of variable sizes. The presence of these hydrophobic cavities affords rich host-guest chemistry, enabling encapsulation of monocationic guest molecules [2, 6 -8]. Several analytical methods are necessary to efficiently characterize these host-guest complexes. 1 H-NMR spectroscopy shows remarkable upfield shifts in the proton signals of encapsulated guests within the cavities [2]. However, since the structures exhibit high point symmetry and the metal components are often paramagnetic, complete characterization by NMR is not always possible. Although solid-state structures may, in the best of cases, be determined by single crystal X-ray crystallography, intrinsically labile metal-ligand interactions do not always allow for unambiguous characterization of solution state structures. Additionally, mass spectrometry is more sensitive than NMR spectroscopy and allows analysis of lower concentrations, thus observing species with solubility properties insufficient for NMR measureme...

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Section: Resultsmentioning

confidence: 99%

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confidence: 99%

Characterization of self-assembled supramolecular [Ga₄L₆] host-guest complexes by electrospray ionization mass spectrometry

Andersen

Seeber

Fiedler

et al. 2006

J. Am. Soc. Mass Spectrom.

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“…[1][2][3][4][5] Much inspiration for this work comes from biological precedents in which optimal combinations of hydrogen-bond, electrostatic, and hydrophobic interactions are used to assemble polypeptides and nucleic acids into robust structural motifs. 2,4 To further expand the tools for preparing such materials, continuing efforts are being directed towards gaining a better understanding of how various combination of non-covalent interactions can be used to prepare self-assembled materials having predictable and well-defined morphologies.…”

Section: Introductionmentioning

confidence: 99%

Self-Organization of porphyrin-peptide units by metal-mediated peptide assembly

Carvalho¹,

Ogawa²

2010

J. Braz. Chem. Soc.

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O polipeptídeo H21(30-mer) forma dímeros "coiled-coil" que apresentam dois resíduos histidínicos expostos ao solvente nos lados opostos de sua superfície. Este peptídeo reage com a protoporfirina IX de cobalto, Co(ppIX), para produzir [Co(ppIX){(H21(30-mer)} 2 ], como determinado por espectroscopia UV-Vis. Esta ligação bi-axial disponibiliza um potencial domínio de oligomerização "coiled-coil" em cada face do anel porfirínico de cobalto. Dicroísmo circular e cromatografia líquida de exclusão de alto desempenho forneceram evidências da auto-organização destas unidades porfirina-peptídeo em solução. A evaporação da solução porfirina-peptídeo em uma superfície sólida resultou na formação de longos materiais cilíndricos com milímetros de comprimento e micrometros de diâmetro. A presença do complexo Co(ppIX) nestes materiais foi confirmada por microscopia Raman. Estes materiais, entretanto, foram formados somente com o tampão fosfato, e não com tampões orgânicos ou água pura, indicando que sua formação deve envolver um processo mais complicado do que originalmente antecipado.The polypeptide H21(30-mer) folds into a two-stranded coiled-coil in which two solventexposed histidine residues reside on opposite sides of its surface. This peptide was allowed to react with cobalt(III) protoporphyrin IX, Co(ppIX), to produce [Co(ppIX){(H21(30-mer)} 2 ], as determined by UV-Vis spectroscopy. This bis-axial ligation thus positions a potential coiledcoil oligomerization domain onto each face of the cobalt porphyrin ring. Circular dichroism spectroscopy and high performance size exclusion chromatography provide evidence for the solution-phase self-assembly of these porphyrin-peptide units. Evaporation of the porphyrinpeptide solution on a solid support results in the formation of long rod-like materials having millimeter-scale lengths and micron-scale diameters. The presence of Co(ppIX) in these materials was confirmed by Raman microscopy. However, they were formed only from phosphate buffer, and not from organic buffers or pure water, indicating that their formation might involve a more complicated process than originally anticipated.Keywords: cobalt protoporphyrin IX, peptides, fibers, self-assembly IntroductionMolecular self-assembly has proven to be a valuable approach towards the bottom-up design of synthetic materials. [1][2][3][4][5] Much inspiration for this work comes from biological precedents in which optimal combinations of hydrogen-bond, electrostatic, and hydrophobic interactions are used to assemble polypeptides and nucleic acids into robust structural motifs. 2,4 To further expand the tools for preparing such materials, continuing efforts are being directed towards gaining a better understanding of how various combination of non-covalent interactions can be used to prepare self-assembled materials having predictable and well-defined morphologies. 6,7 Inspired by workers in the field of supramolecular coordination chemistry, we 8-12 and others [13][14][15][16] have been exploring a new route for preparing self-assem...

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“…In host-guest complexes, two independent entities are supramolecularly associated resulting typically in the entrapment of one of these (guest or cargo) inside the available volume of the other (host) 2 . Host-guest complexes based on synthetic molecular hosts, such as cyclodextrins 3 , calixarenes 4 , cucurbiturils 5 , porphyrins 6 , crown ethers 7 , zeolites 8 and cryptands 9 , form structurally well-defined, synthetic scaffolds. A general strategy to achieve encapsulation within synthetic hosts involves the controlled polymerization of host units resulting in a well-defined cavity within which the guest (cargo) is accommodated and stabilized by molecular recognition 2 .…”

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A synthetic icosahedral DNA-based host–cargo complex for functional in vivo imaging

et al. 2011

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The encapsulation of molecular cargo within well-defined supramolecular architectures is highly challenging. Synthetic hosts are desirable because of their well-defined nature and addressability. Encapsulation of biomacromolecules within synthetic hosts is especially challenging because of the former's large size, sensitive nature, retention of functionality postencapsulation and demonstration of control over the cargo. Here we encapsulate a fluorescent biopolymer that functions as a pH reporter within synthetic, DNA-based icosahedral host without molecular recognition between host and cargo. Only those cells bearing receptors for the DNA casing of the host-cargo complex engulf it. We show that the encapsulated cargo is therefore uptaken cell specifically in Caenorhabditis elegans. Retention of functionality of the encapsulated cargo is quantitatively demonstrated by spatially mapping pH changes associated with endosomal maturation within the coelomocytes of C. elegans. This is the first demonstration of functionality and emergent behaviour of a synthetic host-cargo complex in vivo.

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Self-Assembly of Discrete Cyclic Nanostructures Mediated by Transition Metals

Cited by 3,466 publications

References 278 publications

Characterization of self-assembled supramolecular [Ga₄L₆] host-guest complexes by electrospray ionization mass spectrometry

Characterization of self-assembled supramolecular [Ga₄L₆] host-guest complexes by electrospray ionization mass spectrometry

Self-Organization of porphyrin-peptide units by metal-mediated peptide assembly

A synthetic icosahedral DNA-based host–cargo complex for functional in vivo imaging

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Self-Assembly of Discrete Cyclic Nanostructures Mediated by Transition Metals

Cited by 3,466 publications

References 278 publications

Characterization of self-assembled supramolecular [Ga4L6] host-guest complexes by electrospray ionization mass spectrometry

Characterization of self-assembled supramolecular [Ga4L6] host-guest complexes by electrospray ionization mass spectrometry

Self-Organization of porphyrin-peptide units by metal-mediated peptide assembly

A synthetic icosahedral DNA-based host–cargo complex for functional in vivo imaging

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Characterization of self-assembled supramolecular [Ga₄L₆] host-guest complexes by electrospray ionization mass spectrometry

Characterization of self-assembled supramolecular [Ga₄L₆] host-guest complexes by electrospray ionization mass spectrometry