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Feid C, Luma L, Fischer T, Löffler JG, Grebenovsky N, Wachtveitl J, Heckel A, Bredenbeck J. Iminothioindoxyl Donors with Exceptionally High Cross Section for Protein Vibrational Energy Transfer. Angew Chem Int Ed Engl 2024; 63:e202317047. [PMID: 38103205 DOI: 10.1002/anie.202317047] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2023] [Revised: 12/10/2023] [Accepted: 12/15/2023] [Indexed: 12/18/2023]
Abstract
Various protein functions are related to vibrational energy transfer (VET) as an important mechanism. The underlying transfer pathways can be experimentally followed by ultrafast Vis-pump/IR-probe spectroscopy with a donor-sensor pair of non-canonical amino acids (ncAAs) incorporated in a protein. However, so far only one donor ncAA, azulenylalanine (AzAla), exists, which suffers from a comparably low Vis extinction coefficient. Here, we introduce two novel donor ncAAs based on an iminothioindoxyl (ITI) chromophore. The dimethylamino-ITI (DMA-ITI) and julolidine-ITI (J-ITI) moieties overcome the limitation of AzAla with a 50 times higher Vis extinction coefficient. While ITI moieties are known for ultrafast photoswitching, DMA-ITI and J-ITI exclusively form a hot ground state on the sub-ps timescale instead, which is essential for their usage as vibrational energy donor. In VET measurements of donor-sensor dipeptides we investigate the performance of the new donors. We observe 20 times larger signals compared to the established AzAla donor, which opens unprecedented possibilities for the study of VET in proteins.
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Affiliation(s)
- Carolin Feid
- Institute of Biophysics, Goethe University Frankfurt, Max-von-Laue-Straße 1, 60438, Frankfurt (Main), Germany
| | - Larita Luma
- Institute for Organic Chemistry and Chemical Biology, Goethe University Frankfurt, Max-von-Laue-Straße 7, 60438, Frankfurt (Main), Germany
| | - Tobias Fischer
- Institute for Physical and Theoretical Chemistry, Goethe University Frankfurt, Max-von-Laue-Straße 7, 60438, Frankfurt (Main), Germany
| | - Jan Gerrit Löffler
- Institute of Biophysics, Goethe University Frankfurt, Max-von-Laue-Straße 1, 60438, Frankfurt (Main), Germany
| | - Nikolai Grebenovsky
- Institute for Organic Chemistry and Chemical Biology, Goethe University Frankfurt, Max-von-Laue-Straße 7, 60438, Frankfurt (Main), Germany
| | - Josef Wachtveitl
- Institute for Physical and Theoretical Chemistry, Goethe University Frankfurt, Max-von-Laue-Straße 7, 60438, Frankfurt (Main), Germany
| | - Alexander Heckel
- Institute for Organic Chemistry and Chemical Biology, Goethe University Frankfurt, Max-von-Laue-Straße 7, 60438, Frankfurt (Main), Germany
| | - Jens Bredenbeck
- Institute of Biophysics, Goethe University Frankfurt, Max-von-Laue-Straße 1, 60438, Frankfurt (Main), Germany
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Murfin LC, Lewis SE. Azulene-A Bright Core for Sensing and Imaging. Molecules 2021; 26:molecules26020353. [PMID: 33445502 PMCID: PMC7826776 DOI: 10.3390/molecules26020353] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2020] [Revised: 01/06/2021] [Accepted: 01/08/2021] [Indexed: 12/13/2022] Open
Abstract
Azulene is a hydrocarbon isomer of naphthalene known for its unusual colour and fluorescence properties. Through the harnessing of these properties, the literature has been enriched with a series of chemical sensors and dosimeters with distinct colorimetric and fluorescence responses. This review focuses specifically on the latter of these phenomena. The review is subdivided into two sections. Section one discusses turn-on fluorescent sensors employing azulene, for which the literature is dominated by examples of the unusual phenomenon of azulene protonation-dependent fluorescence. Section two focuses on fluorescent azulenes that have been used in the context of biological sensing and imaging. To aid the reader, the azulene skeleton is highlighted in blue in each compound.
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3
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Watkins EJ, Almhjell PJ, Arnold FH. Direct Enzymatic Synthesis of a Deep-Blue Fluorescent Noncanonical Amino Acid from Azulene and Serine. Chembiochem 2019; 21:80-83. [PMID: 31513332 DOI: 10.1002/cbic.201900497] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2019] [Indexed: 12/21/2022]
Abstract
We report a simple, one-step enzymatic synthesis of the blue fluorescent noncanonical amino acid β-(1-azulenyl)-l-alanine (AzAla). By using an engineered tryptophan synthase β-subunit (TrpB), stereochemically pure AzAla can be synthesized at scale starting from commercially available azulene and l-serine. Mutation of a universally conserved catalytic glutamate in the active site to glycine has only a modest effect on native activity with indole but abolishes activity on azulene, suggesting that this glutamate activates azulene for nucleophilic attack by stabilization of the aromatic ion.
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Affiliation(s)
- Ella J Watkins
- Division of Biology and Biological Engineering, California Institute of Technology, MC 210-41, 1200 E. California Boulevard, Pasadena, CA, 91125, USA
| | - Patrick J Almhjell
- Division of Chemistry and Chemical Engineering, California Institute of Technology, MC 210-41, 1200 E. California Boulevard, Pasadena, CA, 91125, USA
| | - Frances H Arnold
- Division of Biology and Biological Engineering, California Institute of Technology, MC 210-41, 1200 E. California Boulevard, Pasadena, CA, 91125, USA.,Division of Chemistry and Chemical Engineering, California Institute of Technology, MC 210-41, 1200 E. California Boulevard, Pasadena, CA, 91125, USA
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4
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Biondi B, Peggion C, De Zotti M, Pignaffo C, Dalzini A, Bortolus M, Oancea S, Hilma G, Bortolotti A, Stella L, Pedersen JZ, Syryamina VN, Tsvetkov YD, Dzuba SA, Toniolo C, Formaggio F. Conformational properties, membrane interaction, and antibacterial activity of the peptaibiotic chalciporin A: Multitechnique spectroscopic and biophysical investigations on the natural compound and labeled analogs. Biopolymers 2017; 110. [PMID: 29127716 DOI: 10.1002/bip.23083] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2017] [Revised: 10/06/2017] [Accepted: 10/15/2017] [Indexed: 02/28/2024]
Abstract
In this work, an extensive set of spectroscopic and biophysical techniques (including FT-IR absorption, CD, 2D-NMR, fluorescence, and CW/PELDOR EPR) was used to study the conformational preferences, membrane interaction, and bioactivity properties of the naturally occurring synthetic 14-mer peptaibiotic chalciporin A, characterized by a relatively low (≈20%), uncommon proportion of the strongly helicogenic Aib residue. In addition to the unlabeled peptide, we gained in-depth information from the study of two labeled analogs, characterized by one or two residues of the helicogenic, nitroxyl radical-containing TOAC. All three compounds were prepared using the SPPS methodology, which was carefully modified in the course of the syntheses of TOAC-labeled analogs in view of the poorly reactive α-amino function of this very bulky residue and the specific requirements of its free-radical side chain. Despite its potentially high flexibility, our results point to a predominant, partly amphiphilic, α-helical conformation for this peptaibiotic. Therefore, not surprisingly, we found an effective membrane affinity and a remarkable penetration propensity. However, chalciporin A exhibits a selectivity in its antibacterial activity not in agreement with that typical of the other members of this peptide class.
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Affiliation(s)
- Barbara Biondi
- Institute of Biomolecular, Chemistry, Padova Unit, CNR, Padova, 35131, Italy
| | - Cristina Peggion
- Department of Chemical Sciences, University of Padova, Padova, 35131, Italy
| | - Marta De Zotti
- Department of Chemical Sciences, University of Padova, Padova, 35131, Italy
| | - Chiara Pignaffo
- Department of Chemical Sciences, University of Padova, Padova, 35131, Italy
| | - Annalisa Dalzini
- Department of Chemical Sciences, University of Padova, Padova, 35131, Italy
| | - Marco Bortolus
- Department of Chemical Sciences, University of Padova, Padova, 35131, Italy
| | - Simona Oancea
- Department of Agricultural Sciences and Food Engineering, "Lucian Blaga" University of Sibiu, Sibiu, 550012, Romania
| | - Geta Hilma
- Department of Medicine, "Lucian Blaga" University of Sibiu, Sibiu, 550012, Romania
| | - Annalisa Bortolotti
- Department of Chemical Sciences and Technologies, University of Rome Tor Vergata, Rome, 00133, Italy
| | - Lorenzo Stella
- Department of Chemical Sciences and Technologies, University of Rome Tor Vergata, Rome, 00133, Italy
| | - Jens Z Pedersen
- Department of Biology, University of Rome Tor Vergata, Rome, 00133, Italy
| | - Victoria N Syryamina
- Institute of Chemical Kinetics and Combustion, Novosibirsk, 630090, Russian Federation
| | - Yuri D Tsvetkov
- Institute of Chemical Kinetics and Combustion, Novosibirsk, 630090, Russian Federation
| | - Sergei A Dzuba
- Institute of Chemical Kinetics and Combustion, Novosibirsk, 630090, Russian Federation
| | - Claudio Toniolo
- Institute of Biomolecular, Chemistry, Padova Unit, CNR, Padova, 35131, Italy
- Department of Chemical Sciences, University of Padova, Padova, 35131, Italy
| | - Fernando Formaggio
- Institute of Biomolecular, Chemistry, Padova Unit, CNR, Padova, 35131, Italy
- Department of Chemical Sciences, University of Padova, Padova, 35131, Italy
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5
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De Zotti M, Wright K, d’Aboville E, Toffoletti A, Toniolo C, Longhi G, Mazzeo G, Abbate S, Formaggio F. Synthesis of Intrinsically Blue-Colored bis-Nitronyl Nitroxide Peptidomimetic Templates and Their Conformational Preferences as Revealed by a Combined Spectroscopic Analysis. J Org Chem 2017; 82:10033-10042. [DOI: 10.1021/acs.joc.7b01498] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Marta De Zotti
- Department
of Chemistry, University of Padova, 35131 Padova, Italy
| | - Karen Wright
- Institute
Lavoisier de Versailles, UMR 8180, University of Versailles St-Quentin en Yvelines, 78035 Versailles, France
| | - Edouard d’Aboville
- Institute
Lavoisier de Versailles, UMR 8180, University of Versailles St-Quentin en Yvelines, 78035 Versailles, France
| | | | - Claudio Toniolo
- Department
of Chemistry, University of Padova, 35131 Padova, Italy
- ICB,
Padova Unit, CNR, Department of Chemistry, University of Padova, 35131 Padova, Italy
| | - Giovanna Longhi
- Department
of Molecular and Translational Medicine, University of Brescia, 25123 Brescia, Italy
| | - Giuseppe Mazzeo
- Department
of Molecular and Translational Medicine, University of Brescia, 25123 Brescia, Italy
| | - Sergio Abbate
- Department
of Molecular and Translational Medicine, University of Brescia, 25123 Brescia, Italy
| | - Fernando Formaggio
- Department
of Chemistry, University of Padova, 35131 Padova, Italy
- ICB,
Padova Unit, CNR, Department of Chemistry, University of Padova, 35131 Padova, Italy
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6
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Gosavi PM, Moroz YS, Korendovych IV. β-(1-Azulenyl)-L-alanine--a functional probe for determination of pKa of histidine residues. Chem Commun (Camb) 2016; 51:5347-50. [PMID: 25645241 DOI: 10.1039/c4cc08720h] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
β-(1-Azulenyl)-L-alanine (AzAla) can be incorporated into the influenza A virus M2 proton channel. AzAla's sensitivity to the protonation state of the nearby histidines and the lack of environmental fluorescence dependence allow for direct and straightforward determination of histidine pKa values in ion channels.
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Affiliation(s)
- Pallavi M Gosavi
- Department of Chemistry, Syracuse University, 111 College Place, Syracuse, NY 13244, USA.
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7
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Amdursky N. Electron Transfer across Helical Peptides. Chempluschem 2015; 80:1075-1095. [DOI: 10.1002/cplu.201500121] [Citation(s) in RCA: 48] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2015] [Revised: 05/06/2015] [Indexed: 02/05/2023]
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8
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Milov AD, Tsvetkov YD, Bortolus M, Maniero AL, Gobbo M, Toniolo C, Formaggio F. Synthesis and conformational properties of a TOAC doubly spin-labeled analog of the medium-length, membrane active peptaibiotic ampullosporin a as revealed by cd, fluorescence, and EPR spectroscopies. Biopolymers 2014; 102:40-8. [DOI: 10.1002/bip.22362] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2013] [Revised: 07/10/2013] [Accepted: 07/12/2013] [Indexed: 11/10/2022]
Affiliation(s)
- Alexander D. Milov
- Institute of Chemical Kinetics and Combustion; Novosibirsk 630090 Russian Federation
| | - Yuri D. Tsvetkov
- Institute of Chemical Kinetics and Combustion; Novosibirsk 630090 Russian Federation
| | - Marco Bortolus
- Department of Chemical Sciences; University of Padova; 35131 Padova Italy
| | - Anna Lisa Maniero
- Department of Chemical Sciences; University of Padova; 35131 Padova Italy
| | - Marina Gobbo
- Department of Chemical Sciences; University of Padova; 35131 Padova Italy
- Institute of Biomolecular Chemistry; Padova Unit, CNR 35131 Padova Italy
| | - Claudio Toniolo
- Department of Chemical Sciences; University of Padova; 35131 Padova Italy
- Institute of Biomolecular Chemistry; Padova Unit, CNR 35131 Padova Italy
| | - Fernando Formaggio
- Department of Chemical Sciences; University of Padova; 35131 Padova Italy
- Institute of Biomolecular Chemistry; Padova Unit, CNR 35131 Padova Italy
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9
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Moroz YS, Binder W, Nygren P, Caputo GA, Korendovych IV. Painting proteins blue: β-(1-azulenyl)-L-alanine as a probe for studying protein-protein interactions. Chem Commun (Camb) 2013; 49:490-2. [PMID: 23207368 PMCID: PMC3547328 DOI: 10.1039/c2cc37550h] [Citation(s) in RCA: 45] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
We demonstrated that β-(1-azulenyl)-L-alanine, a fluorescent pseudoisosteric analog of tryptophan, exhibits weak environmental dependence and thus allows for using weak intrinsic quenchers, such as methionines, to monitor protein-protein interactions while not perturbing them.
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Affiliation(s)
- Yurii S. Moroz
- Department of Chemistry, Syracuse University, 111 College Place, Syracuse, NY 13244, USA
| | - Wolfgang Binder
- Department of Chemistry, Syracuse University, 111 College Place, Syracuse, NY 13244, USA
- Department of Chemistry, Technical University of Graz, Graz, Austria
| | - Patrik Nygren
- Department of Hematology and Oncology, University of Pennsylvania Medical School, Philadelphia, PA 19014, USA
| | - Gregory A. Caputo
- Department of Chemistry and Biochemistry, Rowan University, Glassboro, NJ 08028, USA
| | - Ivan V. Korendovych
- Department of Chemistry, Syracuse University, 111 College Place, Syracuse, NY 13244, USA
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10
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Short peptide constructs mimic agonist sites of AT(1)R and BK receptors. Amino Acids 2012; 44:835-46. [PMID: 23096780 DOI: 10.1007/s00726-012-1405-9] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2012] [Accepted: 09/17/2012] [Indexed: 10/27/2022]
Abstract
Extracellular peptide ligand binding sites, which bind the N-termini of angiotensin II (AngII) and bradykinin (BK) peptides, are located on the N-terminal and extracellular loop 3 regions of the AT(1)R and BKRB(1) or BKRB(2) G-protein-coupled receptors (GPCRs). Here we synthesized peptides P15 and P13 corresponding to these receptor fragments and showed that only constructs in which these peptides were linked by S-S bond, and cyclized by closing the gap between them, could bind agonists. The formation of construct-agonist complexes was revealed by electron paramagnetic resonance spectra and fluorescence measurements of spin labeled biologically active analogs of AngII and BK (Toac(1)-AngII and Toac(0)-BK), where Toac is the amino acid-type paramagnetic and fluorescence quencher 2, 2, 6, 6-tetramethylpiperidine-1-oxyl-4-amino-4-carboxylic acid. The inactive derivatives Toac(3)-AngII and Toac(3)-BK were used as controls. The interactions characterized by a significant immobilization of Toac and quenching of fluorescence in complexes between agonists and cyclic constructs were specific for each system of peptide-receptor construct assayed since no crossed reactions or reaction with inactive peptides could be detected. Similarities among AT, BKR, and chemokine receptors were identified, thus resulting in a configuration for AT(1)R and BKRB cyclic constructs based on the structure of the CXCR(4), an α-chemokine GPCR-type receptor.
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11
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The spin label amino acid TOAC and its uses in studies of peptides: chemical, physicochemical, spectroscopic, and conformational aspects. Biophys Rev 2012; 4:45-66. [PMID: 22347893 PMCID: PMC3271205 DOI: 10.1007/s12551-011-0064-5] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2011] [Accepted: 12/20/2011] [Indexed: 01/21/2023] Open
Abstract
We review work on the paramagnetic amino acid 2,2,6,6-tetramethyl-N-oxyl-4-amino-4-carboxylic acid, TOAC, and its applications in studies of peptides and peptide synthesis. TOAC was the first spin label probe incorporated in peptides by means of a peptide bond. In view of the rigid character of this cyclic molecule and its attachment to the peptide backbone via a peptide bond, TOAC incorporation has been very useful to analyze backbone dynamics and peptide secondary structure. Many of these studies were performed making use of EPR spectroscopy, but other physical techniques, such as X-ray crystallography, CD, fluorescence, NMR, and FT-IR, have been employed. The use of double-labeled synthetic peptides has allowed the investigation of their secondary structure. A large number of studies have focused on the interaction of peptides, both synthetic and biologically active, with membranes. In the latter case, work has been reported on ligands and fragments of GPCR, host defense peptides, phospholamban, and β-amyloid. EPR studies of macroscopically aligned samples have provided information on the orientation of peptides in membranes. More recent studies have focused on peptide–protein and peptide–nucleic acid interactions. Moreover, TOAC has been shown to be a valuable probe for paramagnetic relaxation enhancement NMR studies of the interaction of labeled peptides with proteins. The growth of the number of TOAC-related publications suggests that this unnatural amino acid will find increasing applications in the future.
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12
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Gobbo M, Merli E, Biondi B, Oancea S, Toffoletti A, Formaggio F, Toniolo C. Synthesis and preliminary conformational analysis of TOAC spin-labeled analogues of the medium-length peptaibiotic tylopeptin B. J Pept Sci 2011; 18:37-44. [DOI: 10.1002/psc.1413] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2011] [Revised: 07/18/2011] [Accepted: 08/02/2011] [Indexed: 11/09/2022]
Affiliation(s)
- Marina Gobbo
- ICB-Padova Unit, CNR, Department of Chemical Sciences; University of Padova; 35131 Padova Italy
| | - Elisabetta Merli
- ICB-Padova Unit, CNR, Department of Chemical Sciences; University of Padova; 35131 Padova Italy
| | - Barbara Biondi
- ICB-Padova Unit, CNR, Department of Chemical Sciences; University of Padova; 35131 Padova Italy
| | - Simona Oancea
- Department of Biochemistry and Toxicology; University “Lucian Blaga” Sibiu; Sibiu 550012 Romania
| | - Antonio Toffoletti
- ICB-Padova Unit, CNR, Department of Chemical Sciences; University of Padova; 35131 Padova Italy
| | - Fernando Formaggio
- ICB-Padova Unit, CNR, Department of Chemical Sciences; University of Padova; 35131 Padova Italy
| | - Claudio Toniolo
- ICB-Padova Unit, CNR, Department of Chemical Sciences; University of Padova; 35131 Padova Italy
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13
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Membrane perturbation by the antimicrobial peptide PMAP-23: a fluorescence and molecular dynamics study. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2009; 1788:1523-33. [PMID: 19397893 DOI: 10.1016/j.bbamem.2009.04.013] [Citation(s) in RCA: 61] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/23/2009] [Revised: 04/03/2009] [Accepted: 04/13/2009] [Indexed: 01/16/2023]
Abstract
Several bioactive peptides exert their biological function by interacting with cellular membranes. Structural data on their location inside lipid bilayers are thus essential for a detailed understanding of their mechanism of action. We propose here a combined approach in which fluorescence spectroscopy and molecular dynamics (MD) simulations were applied to investigate the mechanism of membrane perturbation by the antimicrobial peptide PMAP-23. Fluorescence spectra, depth-dependent quenching experiments, and peptide-translocation assays were employed to determine the location of the peptide inside the membrane. MD simulations were performed starting from a random mixture of water, lipids and peptide, and following the spontaneous self-assembly of the bilayer. Both experimental and theoretical data indicated a peptide location just below the polar headgroups of the membrane, with an orientation essentially parallel to the bilayer plane. These findings, together with experimental results on peptide-induced leakage from large and giant vesicles, lipid flip-flop and peptide exchange between vesicles, support a mechanism of action consistent with the "carpet" model. Furthermore, the atomic detail provided by the simulations suggested the occurrence of an additional, more specific and novel mechanism of bilayer destabilization by PMAP-23, involving the unusual insertion of charged side chains into the hydrophobic core of the membrane.
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14
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Mandal HS, Kraatz HB. Effect of the surface curvature on the secondary structure of peptides adsorbed on nanoparticles. J Am Chem Soc 2007; 129:6356-7. [PMID: 17458962 DOI: 10.1021/ja0703372] [Citation(s) in RCA: 108] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Himadri S Mandal
- Department of Chemistry, University of Saskatchewan, 110 Science Place, Saskatoon, Canada
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15
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Fabris L, Antonello S, Armelao L, Donkers RL, Polo F, Toniolo C, Maran F. Gold Nanoclusters Protected by Conformationally Constrained Peptides. J Am Chem Soc 2005; 128:326-36. [PMID: 16390162 DOI: 10.1021/ja0560581] [Citation(s) in RCA: 112] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The preparation and properties of a series of gold nanoclusters protected by thiolated peptides based on the alpha-aminoisobutyric acid (Aib) unit are described. The peptides were devised to form 0-3 C=O...H-N intramolecular hydrogen bonds, as required by their 3(10)-helical structure. The monolayer-protected clusters (MPCs) were prepared, using a modified version of the two-phase Brust-Schiffrin preparation, and fully characterized with (1)H NMR spectrometry, IR and UV-vis absorption spectroscopies, transmission electron microscopy (TEM), thermogravimetric analysis (TGA), and X-ray photoelectron spectroscopy (XPS). The MPCs were obtained with core diameters in the range of 1.1-2.3 nm, depending on the reaction conditions. Structured peptides formed smaller clusters. The smallest MPC obtained is in agreement with the average formula Au(38)Pep(18). The results showed that the chemical integrity of the peptide is maintained upon monolayer formation and that the average number of peptide ligands per gold cluster is typically 75-85% the value calculated for alkanethiolate MPCs of similar sizes. The IR and NMR spectra indicated that in the monolayer the peptides are involved in both intra- and interligand C=O...H-N hydrogen bonds.
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Affiliation(s)
- Laura Fabris
- Department of Chemistry, University of Padua, via Marzolo 1, 35131 Padua, Italy
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