Photophysics of preassociated pyrenes in aqueous polymer solutions and in other organized media

Winnik, Françoise M.

doi:10.1021/cr00018a001

Cited by 1,694 publications

(1,729 citation statements)

References 53 publications

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“…Relevant examples include the multiple phosphorescence bands in *Hg n excimeric clusters, 39 copper halide clusters, 40 and ruthenium(II) complexes 41 and also multiple fluorescence bands in excimer-forming aromatic hydrocarbons such as pyrene. 42 We have carried out temperature-dependent lifetime studies for crystals of the three compounds on the basis of the assignment discussed above. The data illustrate a large increase in the lifetime values for each band upon cooling.…”

Section: Resultsmentioning

confidence: 99%

Metal Effect on the Supramolecular Structure, Photophysics, and Acid−Base Character of Trinuclear Pyrazolato Coinage Metal Complexes

Omary¹,

Rawashdeh‐Omary²,

Gonser³

et al. 2005

Inorg. Chem.

280

359

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Varying the coinage metal in cyclic trinuclear pyrazolate complexes is found to significantly affect the solid-state packing, photophysics, and acid−base properties. The three isoleptic compounds used in this study are {[3,5-(CF 3 ) 2 Pz]M} 3 with M ) Cu, Ag, and Au (i.e., Cu 3 , Ag 3 , and Au 3 , respectively). They form isomorphous crystals and exist as trimers featuring nine-membered M 3 N 6 rings with linear two-coordinate metal sites. On the basis of the M−N distances, the covalent radii of two-coordinate Cu I , Ag I , and Au I were estimated as 1.11, 1.34, and 1.25 Å, respectively. The cyclic {[3,5-(CF 3 ) 2 Pz]M} 3 complexes pack as infinite chains of trimers with a greater number of pairwise intertrimer M‚‚‚M interactions upon proceeding to heavier coinage metals. However, the intertrimer distances are conspicuously short in Ag 3 (3.204 Å) versus Au 3 (3.885 Å) or Cu 3 (3.813 Å) despite the significantly larger covalent radius of Ag I . Remarkable luminescence properties are found for the three M 3 complexes, as manifested by the appearance of multiple unstructured phosphorescence bands whose colors and lifetimes change qualitatively upon varying the coinage metal and temperature. The multiple emissions are assigned to different phosphorescent excimeric states that exhibit enhanced M‚‚‚M bonding relative to the ground state. The startling luminescence thermochromic changes in crystals of each compound are related to relaxation between the different phosphorescent excimers. The trend in the lowest energy phosphorescence band follows the relative triplet energy of the three M I atomic ions. DFT calculations indicate that {[3,5-(R) 2 Pz]M} 3 trimers with R ) H or Me are bases with the relative basicity order Ag , Cu < Au while fluorination (R ) CF 3 ) renders even the Au trimer acidic. These predictions were substantiated experimentally by the isolation of the first acid−base adduct, {[Au 3 ] 2 :toluene} ∞ , in which a trinuclear Au I complex acts as an acid.

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Section: Resultsmentioning

confidence: 99%

Metal Effect on the Supramolecular Structure, Photophysics, and Acid−Base Character of Trinuclear Pyrazolato Coinage Metal Complexes

Omary¹,

Rawashdeh‐Omary²,

Gonser³

et al. 2005

Inorg. Chem.

280

359

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“…Refs. [31][32][33][34][35]. Its spectral characteristics are sensitive to the environment, and it has an extremely long singlet excited state lifetime (ϳ100 ns), which makes it especially useful for studying macromolecular motions.…”

Section: Purification Of His-gp96 and Modification Of A Vsv Peptidementioning

confidence: 99%

“…These spectra were consistently reproducible. Emission peaks at 452 and 494 nm are characteristic of pyrene excimers (excited state dimers) (35)(36)(37). Surprisingly, no pyrene monomer emission was detected (the E max values of monomer are at 376 and 394 nm; e.g.…”

Section: Purification Of His-gp96 and Modification Of A Vsv Peptidementioning

confidence: 99%

Molecular Mechanisms of Peptide Loading by the Tumor Rejection Antigen/Heat Shock Chaperone gp96 (GRP94)

Sastry

Linderoth

1999

Journal of Biological Chemistry

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Complexes of gp96/GRP94 and peptides have been shown to elicit immunogenicity. We used fluorescence to understand peptide association with gp96. A pyrenepeptide conjugate was complexed with gp96 under a variety of conditions. At room temperature in low salt (20 mM NaCl), the peptide binds gp96 with a strong affinity (ϳ100 -150 nM) and forms pyrene excimers, suggesting that the peptides were assembled as dimers. In high salt (2.2 M NaCl), although peptide binding was stronger (K a Ϸ 55 nM) than in low salt, pyrene excimers were absent, implying that peptides were farther apart in the complex. Heat shock-activated peptide binding exhibited characteristics of both low salt and high salt modes of binding. Anisotropy and average lifetime of the bound pyrene suggested that peptides were probably located in a solvent-accessible hydrophobic binding pocket in low salt, whereas in high salt, the peptide may be buried in a less hydrophobic (more hydrophilic) environment. These results suggested that peptide-gp96 complexes were assembled in several different ways, depending on the assembly conditions. Resonance energy transfer between the intrinsic tryptophan(s) in gp96 and pyrene suggested that one or more tryptophan residues were within the critical Forster distance of 27-30 Å from the pyrene in the bound peptide. It is proposed that peptides are assembled within higher order gp96 complexes (dimers, etc.) in a hydrophobic pocket and that there may be a conformational change in gp96 leading to an open configuration for peptide loading.Heat shock proteins purified from tumor cells when injected into inbred mice bearing the same specific type of tumor elicit immune response against only that specific tumor (1-4). This paradigm, which has been extended to virus-infected cells (5-7), as well as to a variety of animal cancers (4), forms the basis for a new therapeutic strategy against human cancers using HSPs 1 as vaccines. The HSP-mediated specific immunogenicity has been attributed to endogenous peptides that are noncovalently bound to the HSPs (8). Examples of immunogenic HSP-peptide complexes include gp96 (GRP94), BiP, protein disulfide isomerase, and calreticulin. These stress proteins are abundant and are normally present in the lumen of the endoplasmic reticulum (9). Interestingly, HSPs display dual functionality. On the one hand, they act as molecular chaperones assisting in protein folding, and on the other, they appear to shunt peptides into the immune-response pathways. However, the relationship between the two functions remains unclear. From our perspective, it is the immunogenic function of HSPpeptide complexes that is the most intriguing and is of potential value to human health. The gp96 chaperone system is the most extensively studied from an immunological standpoint (10 -16). Gp96 is an abundant endoplasmic reticulum resident glycoprotein that binds a variety of peptides in vitro with no apparent amino acid sequence specificity (17). Unambiguous confirmation of the immunogenic properties of gp96-peptide complex...

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“…The functionalization of the two peptides with a Py group has the double aim to investigate the role of an aromatic moiety in the aggregation process and to provide the two compounds with a chromophore featuring strong absorption in the UV region and intense uorescence emission in the blue region of the visible spectrum. 20 These properties allowed us to apply several spectroscopic techniques (UV-Vis absorption, steady-state and time resolved uorescence, electronic CD) and IR absorption as well, triggering the aggregation process by adding increasing fractions of water to MeOH solutions. The morphology of the peptide aggregates when deposited on a hydrophilic mica surface was characterized by atomic force microscopy (AFM) imaging.…”

Section: Introductionmentioning

confidence: 99%

A single-residue substitution inhibits fibrillization of Ala-based pentapeptides. A spectroscopic and molecular dynamics investigation

et al. 2014

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The aggregation properties of two Ala-based pentapeptides were investigated by spectroscopic techniques and molecular dynamics (MD) simulations. The two peptides, both functionalized at the N-terminus with a pyrenyl group, differ in the insertion of an a-aminoisobutyric acid residue at position 4. We showed that this single modification of the homo-peptide sequence inhibits the aggregation of the pentapeptide in aqueous solutions. Atomic force microscopy imaging revealed that the two peptides form mesoscopic aggregates of very different morphologies when deposited on mica. MD experiments showed that the two peptides have a very different propensity to form b-pleated sheet structures, as confirmed by our spectroscopic measurements. The implications of these findings for our understanding of the mechanism leading to the formation of amyloid structures, primary responsible for numerous neurodegenerative diseases, are also discussed.

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Photophysics of preassociated pyrenes in aqueous polymer solutions and in other organized media

Cited by 1,694 publications

References 53 publications

Metal Effect on the Supramolecular Structure, Photophysics, and Acid−Base Character of Trinuclear Pyrazolato Coinage Metal Complexes

Metal Effect on the Supramolecular Structure, Photophysics, and Acid−Base Character of Trinuclear Pyrazolato Coinage Metal Complexes

Molecular Mechanisms of Peptide Loading by the Tumor Rejection Antigen/Heat Shock Chaperone gp96 (GRP94)

A single-residue substitution inhibits fibrillization of Ala-based pentapeptides. A spectroscopic and molecular dynamics investigation

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