1
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Kaczmarek K, Artym J, Bojarska J, Pacholczyk-Sienicka B, Waśko J, Jelemenska I, Wolf WM, Breza M, Zimecki M. The Immunosuppressive Properties of Cyclo-[ D-Pro-Pro- β3-HoPhe-Phe-] Tetrapeptide Selected from Stereochemical Variants of Cyclo-[Pro-Pro- β3-HoPhe-Phe-] Peptide. Pharmaceutics 2024; 16:1106. [PMID: 39204451 PMCID: PMC11359963 DOI: 10.3390/pharmaceutics16081106] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2024] [Revised: 08/08/2024] [Accepted: 08/20/2024] [Indexed: 09/04/2024] Open
Abstract
The anti-inflammatory, antiviral, and anti-cancer properties, as well as the mechanism of action of cyclo-[Pro-Pro-β3-HoPhe-Phe-] tetrapeptide (denoted as 4B8M), were recently described. The aim of this work was to synthesize and evaluate the immunosuppressive actions of the stereochemical variants of 4B8M by sequential substitution of L-amino acids by D-amino acids (a series of peptides denoted as P01-P07) using parent 4B8M as a reference compound. In addition, diverse available bioinformatics tools using machine learning and artificial intelligence were tested to find the bio-pharmacokinetic and polypharmacological attributes of analyzed stereomers. All peptides were non-toxic to human peripheral blood mononuclear cells (PBMCs) and only cyclo-[D-Pro-Pro-β3-HoPhe-Phe-] peptide (P03) was capable of inhibiting mitogen-induced PBMC proliferation. The peptides inhibited the lipopolysaccharide (LPS)-induced production of tumor necrosis factor-alpha (TNF-α) to various degrees, with P04 (cyclo-[Pro-Pro-D-β3-HoPhe-Phe-]) and P03 being the most potent. For further in vivo studies, P03 was selected because it had the combined properties of inhibiting cell proliferation and TNF-α production. P03 demonstrated a comparable ability to 4B8M in the inhibition of auricle edema and lymph node cell number and in the normalization of a distorted blood cell composition in contact sensitivity to the oxazolone mouse model. In the mouse model of carrageenan-induced inflammation of the air pouch, P03 exhibited a similar inhibition of the cell number in the air pouches as 4B8M, but its inhibitory effects on the percentage of neutrophils and eosinophils in the air pouches and blood, as well as on mastocyte degranulation in the air pouches, were stronger in comparison to 4B8M. Lastly, in a mouse model of dextran sulfate-induced colitis, similar effects to 4B8M regarding thymocyte number restoration and normalization of the blood cell pictures by P03 were observed. In summary, depending on either experimental findings or in silico predictions, P03 demonstrated comparable, or even better, anti-inflammatory and bio-pharmacokinetic properties to 4B8M and may be considered as a potential therapeutic. The possibility of P00 and P03 identification by circular dichroism measurements was tested by quantum-chemical calculations.
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Affiliation(s)
- Krzysztof Kaczmarek
- Institute of Organic Chemistry, Łódź University of Technology, S. Żeromskiego Str. 116, 90-924 Łódź, Poland; (B.P.-S.); (J.W.)
| | - Jolanta Artym
- Department of Experimental Therapy, Hirszfeld Institute of Immunology and Experimental Therapy, R. Weigla Str. 12, 53-114 Wrocław, Poland; (J.A.); (M.Z.)
| | - Joanna Bojarska
- Institute of Inorganic and Ecological Chemistry, Chemistry Department, Łódź University of Technology, S. Żeromskiego Str. 116, 90-924 Łódź, Poland;
| | - Barbara Pacholczyk-Sienicka
- Institute of Organic Chemistry, Łódź University of Technology, S. Żeromskiego Str. 116, 90-924 Łódź, Poland; (B.P.-S.); (J.W.)
| | - Joanna Waśko
- Institute of Organic Chemistry, Łódź University of Technology, S. Żeromskiego Str. 116, 90-924 Łódź, Poland; (B.P.-S.); (J.W.)
| | - Ingrid Jelemenska
- Department of Physical Chemistry, Slovak Technical University, Radlinskeho 9, SK-81237 Bratislava, Slovakia; (I.J.); (M.B.)
| | - Wojciech M. Wolf
- Institute of Inorganic and Ecological Chemistry, Chemistry Department, Łódź University of Technology, S. Żeromskiego Str. 116, 90-924 Łódź, Poland;
| | - Martin Breza
- Department of Physical Chemistry, Slovak Technical University, Radlinskeho 9, SK-81237 Bratislava, Slovakia; (I.J.); (M.B.)
| | - Michał Zimecki
- Department of Experimental Therapy, Hirszfeld Institute of Immunology and Experimental Therapy, R. Weigla Str. 12, 53-114 Wrocław, Poland; (J.A.); (M.Z.)
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2
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Menant S, Tognetti V, Oulyadi H, Guilhaudis L, Ségalas-Milazzo I. A Joint Experimental and Theoretical Study on the Structural and Spectroscopic Properties of the Piv-Pro-d-Ser-NHMe Peptide. J Phys Chem B 2024; 128:6704-6715. [PMID: 38967625 DOI: 10.1021/acs.jpcb.4c01664] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 07/06/2024]
Abstract
In this paper, we investigate the secondary structure of the Piv-Pro-d-Ser-NHMe peptide by means of nuclear magnetic resonance (NMR) and electronic circular dichroism (ECD) experiments, in conjunction with theoretical simulations based on molecular dynamics and time-dependent density functional theory calculations including polarizable embedding to account for solvent effects. The various experimental and theoretical protocols are assessed and validated, and are shown to provide a consistent description of the turn structure adopted by this peptide in solution. In addition, a simple fitting procedure is proposed to make the simulated and experimental ECD almost perfectly match. This full methodology is finally tested on another small peptide, enlightening its efficiency and robustness.
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Affiliation(s)
- Sébastien Menant
- Univ Rouen Normandie, INSA Rouen Normandie, CNRS, Normandie Univ, COBRA UMR 6014, INC3M FR 3038, F-76000 Rouen, France
| | - Vincent Tognetti
- Univ Rouen Normandie, INSA Rouen Normandie, CNRS, Normandie Univ, COBRA UMR 6014, INC3M FR 3038, F-76000 Rouen, France
| | - Hassan Oulyadi
- Univ Rouen Normandie, INSA Rouen Normandie, CNRS, Normandie Univ, COBRA UMR 6014, INC3M FR 3038, F-76000 Rouen, France
| | - Laure Guilhaudis
- Univ Rouen Normandie, INSA Rouen Normandie, CNRS, Normandie Univ, COBRA UMR 6014, INC3M FR 3038, F-76000 Rouen, France
| | - Isabelle Ségalas-Milazzo
- Univ Rouen Normandie, INSA Rouen Normandie, CNRS, Normandie Univ, COBRA UMR 6014, INC3M FR 3038, F-76000 Rouen, France
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3
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Gómez S, Ambrosetti M, Giovannini T, Cappelli C. Close-Up Look at Electronic Spectroscopic Signatures of Common Pharmaceuticals in Solution. J Phys Chem B 2024; 128:2432-2446. [PMID: 38416564 DOI: 10.1021/acs.jpcb.3c07795] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/29/2024]
Abstract
Simulating electronic properties and spectral signals requires robust computational approaches that need tuning with the system's peculiarities. In this paper, we test implicit and fully atomistic solvation models for the calculation of UV-vis and electronic circular dichroism (ECD) spectra of two pharmaceutically relevant molecules, namely, (2S)-captopril and (S)-naproxen, dissolved in aqueous solution. Room temperature molecular dynamics simulations reveal that these two drugs establish strong contacts with the surrounding solvent molecules via hydrogen bonds. Such specific interactions, which play a major role in the spectral response and are neglected in implicit approaches, are further characterized and quantified with natural bond orbital methods. Our calculations show that simulated spectra, and especially ECD, are in good agreement with experiments solely when conformational and configurational dynamics, mutual polarization, and solute-solvent repulsion effects are considered.
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Affiliation(s)
- Sara Gómez
- Scuola Normale Superiore, Classe di Scienze, Piazza dei Cavalieri 7, Pisa 56126, Italy
| | - Matteo Ambrosetti
- Scuola Normale Superiore, Classe di Scienze, Piazza dei Cavalieri 7, Pisa 56126, Italy
| | - Tommaso Giovannini
- Scuola Normale Superiore, Classe di Scienze, Piazza dei Cavalieri 7, Pisa 56126, Italy
| | - Chiara Cappelli
- Scuola Normale Superiore, Classe di Scienze, Piazza dei Cavalieri 7, Pisa 56126, Italy
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4
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Truttmann V, Loxha A, Banu R, Pittenauer E, Malola S, Matus MF, Wang Y, Ploetz EA, Rupprechter G, Bürgi T, Häkkinen H, Aikens C, Barrabés N. Directing Intrinsic Chirality in Gold Nanoclusters: Preferential Formation of Stable Enantiopure Clusters in High Yield and Experimentally Unveiling the "Super" Chirality of Au 144. ACS NANO 2023; 17:20376-20386. [PMID: 37805942 PMCID: PMC10604085 DOI: 10.1021/acsnano.3c06568] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/17/2023] [Accepted: 09/28/2023] [Indexed: 10/10/2023]
Abstract
Chiral gold nanoclusters offer significant potential for exploring chirality at a fundamental level and for exploiting their applications in sensing and catalysis. However, their widespread use is impeded by low yields in synthesis, tedious separation procedures of their enantiomeric forms, and limited thermal stability. In this study, we investigated the direct synthesis of enantiopure chiral nanoclusters using the chiral ligand 2-MeBuSH in the fabrication of Au25, Au38, and Au144 nanoclusters. Notably, this approach leads to the unexpected formation of intrinsically chiral clusters with high yields for chiral Au38 and Au144 nanoclusters. Experimental evaluation of chiral activity by circular dichroism (CD) spectroscopy corroborates previous theoretical calculations, highlighting the stronger CD signal exhibited by Au144 compared to Au38 or Au25. Furthermore, the formation of a single enantiomeric form is experimentally confirmed by comparing it with intrinsically chiral Au38(2-PET)24 (2-PET: 2-phenylethanethiol) and is supported theoretically for both Au38 and Au144. Moreover, the prepared chiral clusters show stability against diastereoisomerization, up to temperatures of 80 °C. Thus, our findings not only demonstrate the selective preparation of enantiopure, intrinsically chiral, and highly stable thiolate-protected Au nanoclusters through careful ligand design but also support the predicted "super" chirality in the Au144 cluster, encompassing hierarchical chirality in ligands, staple configuration, and core structure.
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Affiliation(s)
- Vera Truttmann
- Institute
of Materials Chemistry, TU Wien, Getreidemarkt 9/E165, 1060 Vienna, Austria
| | - Adea Loxha
- Institute
of Materials Chemistry, TU Wien, Getreidemarkt 9/E165, 1060 Vienna, Austria
| | - Rareş Banu
- Institute
of Materials Chemistry, TU Wien, Getreidemarkt 9/E165, 1060 Vienna, Austria
| | - Ernst Pittenauer
- Institute
of Chemical Technologies and Analytics, TU Wien, Getreidemarkt
9/E164, 1060 Vienna, Austria
| | - Sami Malola
- Departments
of Physics and Chemistry, Nanoscience Center, University of Jyväskylä, FI-40014 Jyväskylä, Finland
| | - María Francisca Matus
- Departments
of Physics and Chemistry, Nanoscience Center, University of Jyväskylä, FI-40014 Jyväskylä, Finland
| | - Yuchen Wang
- Department
of Chemistry, Kansas State University, Manhattan, Kansas 66506, United States
of America
| | - Elizabeth A. Ploetz
- Department
of Chemistry, Kansas State University, Manhattan, Kansas 66506, United States
of America
| | - Günther Rupprechter
- Institute
of Materials Chemistry, TU Wien, Getreidemarkt 9/E165, 1060 Vienna, Austria
| | - Thomas Bürgi
- Department
of Physical Chemistry, University of Geneva, 30 Quai Ernest-Ansermet, 1211 Geneva 4, Switzerland
| | - Hannu Häkkinen
- Departments
of Physics and Chemistry, Nanoscience Center, University of Jyväskylä, FI-40014 Jyväskylä, Finland
| | - Christine Aikens
- Department
of Chemistry, Kansas State University, Manhattan, Kansas 66506, United States
of America
| | - Noelia Barrabés
- Institute
of Materials Chemistry, TU Wien, Getreidemarkt 9/E165, 1060 Vienna, Austria
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5
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Monti M, Scarel E, Hassanali A, Stener M, Marchesan S. Diverging conformations guide dipeptide self-assembly into crystals or hydrogels. Chem Commun (Camb) 2023; 59:10948-10951. [PMID: 37605851 DOI: 10.1039/d3cc02682e] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 08/23/2023]
Abstract
The prediction of dipeptide assembly into crystals or gels is challenging. This work reveals the diverging conformational landscape that guides self-organization towards different outcomes. In silico and experimental data enabled deciphering of the electronic circular dichroism (ECD) spectra of self-assembling dipeptides to reveal folded or extended conformers as key players.
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Affiliation(s)
- M Monti
- Chem. Pharm. Sc. Dept., University of Trieste, Via L. Giorgieri 1, Trieste 34127, Italy.
| | - E Scarel
- Chem. Pharm. Sc. Dept., University of Trieste, Via L. Giorgieri 1, Trieste 34127, Italy.
| | - A Hassanali
- The Abdus Salam International Centre for Theoretical Physics, Strada Costiera 11, Trieste 34151, Italy
| | - M Stener
- Chem. Pharm. Sc. Dept., University of Trieste, Via L. Giorgieri 1, Trieste 34127, Italy.
| | - S Marchesan
- Chem. Pharm. Sc. Dept., University of Trieste, Via L. Giorgieri 1, Trieste 34127, Italy.
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6
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Aschi M, Palombi L, Amadei A. Theoretical-Computational Modeling of CD Spectra of Aqueous Monosaccharides by Means of Molecular Dynamics Simulations and Perturbed Matrix Method. Molecules 2023; 28:molecules28083591. [PMID: 37110825 PMCID: PMC10144652 DOI: 10.3390/molecules28083591] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2023] [Revised: 04/12/2023] [Accepted: 04/13/2023] [Indexed: 04/29/2023] Open
Abstract
The electronic circular dichroism (ECD) spectra of aqueous d-glucose and d-galactose were modeled using a theoretical-computational approach combining molecular dynamics (MD) simulations and perturbed matrix method (PMM) calculations, hereafter termed MD-PMM. The experimental spectra were reproduced with a satisfactory accuracy, confirming the good performances of MD-PMM in modeling different spectral features in complex atomic-molecular systems, as already reported in previous studies. The underlying strategy of the method was to perform a preliminary long timescale MD simulation of the chromophore followed by the extraction of the relevant conformations through essential dynamics analysis. On this (limited) number of relevant conformations, the ECD spectrum was calculated via the PMM approach. This study showed that MD-PMM was able to reproduce the essential features of the ECD spectrum (i.e., the position, the intensity, and the shape of the bands) of d-glucose and d-galactose while avoiding the rather computationally expensive aspects, which were demonstrated to be important for the final outcome, such as (i) the use of a large number of chromophore conformations; (ii) the inclusion of quantum vibronic coupling; and (iii) the inclusion of explicit solvent molecules interacting with the chromophore atoms within the chromophore itself (e.g., via hydrogen bonds).
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Affiliation(s)
- Massimiliano Aschi
- Dipartimento di Scienze Fisiche e Chimiche, Università dell'Aquila via Vetoio (Coppito 2), 67010 l'Aquila, Italy
| | - Laura Palombi
- Dipartimento di Scienze Fisiche e Chimiche, Università dell'Aquila via Vetoio (Coppito 2), 67010 l'Aquila, Italy
| | - Andrea Amadei
- Dipartimento di Scienze e Tecnologie Chimiche, Università di Roma "Tor Vergata", Via della Ricerca Scientifica 1, 00133 Roma, Italy
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7
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Monti M, Stener M, Coccia E. Electronic circular dichroism from real-time propagation in state space. J Chem Phys 2023; 158:084102. [PMID: 36859092 DOI: 10.1063/5.0136392] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
In this paper, we propose to compute the electronic circular dichroism (ECD) spectra of chiral molecules using a real-time propagation of the time-dependent Schrödinger equation (TDSE) in the space of electronic field-free eigenstates, by coupling TDSE with a given treatment of the electronic structure of the target. The time-dependent induced magnetic moment is used to compute the ECD spectrum from an explicit electric perturbation. The full matrix representing the transition magnetic moment in the space of electronic states is generated from that among pairs of molecular orbitals. In the present work, we show the ECD spectra of methyloxirane, of several conformers of L-alanine, and of the Λ-Co(acac)3 complex, computed from a singly excited ansatz of time-dependent density functional theory eigenstates. The time-domain ECD spectra properly reproduce the frequency-domain ones obtained in the linear-response regime and quantitatively agree with the available experimental data. Moreover, the time-domain approach to ECD allows us to naturally go beyond the ground-state rotationally averaged ECD spectrum, which is the standard outcome of the linear-response theory, e.g., by computing the ECD spectra from electronic excited states.
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Affiliation(s)
- M Monti
- Dipartimento di Scienze Chimiche e Farmaceutiche, Università di Trieste, Via L. Giorgieri 1, 34127 Trieste, Italy
| | - M Stener
- Dipartimento di Scienze Chimiche e Farmaceutiche, Università di Trieste, Via L. Giorgieri 1, 34127 Trieste, Italy
| | - E Coccia
- Dipartimento di Scienze Chimiche e Farmaceutiche, Università di Trieste, Via L. Giorgieri 1, 34127 Trieste, Italy
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8
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Monti M, Brancolini G, Coccia E, Toffoli D, Fortunelli A, Corni S, Aschi M, Stener M. The Conformational Dynamics of the Ligands Determines the Electronic Circular Dichroism of the Chiral Au 38(SC 2H 4Ph) 24 Cluster. J Phys Chem Lett 2023; 14:1941-1948. [PMID: 36787099 PMCID: PMC9940292 DOI: 10.1021/acs.jpclett.2c03923] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/28/2022] [Accepted: 02/10/2023] [Indexed: 06/18/2023]
Abstract
Effects of the conformational dynamics of 2-PET protective ligands on the electronic circular dichroism (ECD) of the chiral Au38(SC2H4Ph)24 cluster are investigated. We adopt a computational protocol in which ECD spectra are calculated via the first principle polTDDFT approach on a series of conformations extracted from MD simulations by using Essential Dynamics (ED) analysis, and then properly weighted to predict the final spectrum. We find that the experimental spectral features are well reproduced, whereas significant discrepancies arise when the spectrum is calculated using the experimental X-ray structure. This result unambiguously demonstrates the need to account for the conformational effects in the ECD modeling of chiral nanoclusters. The present procedure proved to be able of capturing the essential conformational features of the dynamic Au38(SC2H4Ph)24 system, opening the possibility to model the ECD of soluble chiral nanoclusters in a realistic way.
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Affiliation(s)
- M. Monti
- Dipartimento
di Scienze Chimiche e Farmaceutiche, Università
di Trieste, Via L. Giorgieri 1, 34127 Trieste, Italy
| | - G. Brancolini
- Istituto
Nanoscienze, CNR-NANO, Center S3, Via G. Campi 213/A, 41100 Modena, Italy
| | - E. Coccia
- Dipartimento
di Scienze Chimiche e Farmaceutiche, Università
di Trieste, Via L. Giorgieri 1, 34127 Trieste, Italy
| | - D. Toffoli
- Dipartimento
di Scienze Chimiche e Farmaceutiche, Università
di Trieste, Via L. Giorgieri 1, 34127 Trieste, Italy
| | - A. Fortunelli
- CNR-ICCOM, Consiglio Nazionale delle Ricerche, via G. Moruzzi 1, 56124, Pisa, Italy
| | - S. Corni
- Istituto
Nanoscienze, CNR-NANO, Center S3, Via G. Campi 213/A, 41100 Modena, Italy
- Dipartimento
di Scienze Chimiche, Università di
Padova, Via Francesco Marzolo 1, 35131 Padova, Italy
| | - M. Aschi
- Dipartimento
di Scienze Fisiche e Chimiche, Università
dell’Aquila, Via Vetoio, 67100, l’Aquila, Italy
| | - M. Stener
- Dipartimento
di Scienze Chimiche e Farmaceutiche, Università
di Trieste, Via L. Giorgieri 1, 34127 Trieste, Italy
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9
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Pyrlin S, Lenzi V, Silva A, Ramos M, Marques L. Adhesion of Bis-Salphen-Based Coordination Polymers to Graphene: Insights from Free Energy Perturbation Study. Polymers (Basel) 2022; 14:4525. [PMID: 36365517 PMCID: PMC9657960 DOI: 10.3390/polym14214525] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2022] [Revised: 10/17/2022] [Accepted: 10/18/2022] [Indexed: 09/08/2024] Open
Abstract
Manipulation of nanoscale objects using molecular self-assembly is a potent tool to achieve large scale nanopatterning with small effort. Coordination polymers of bis-salphen compounds based on zinc have demonstrated their ability to align carbon nanotubes into micro-scale networks with an unusual "rings-and-rods" pattern. This paper investigates how the compounds interact with pristine and functionalized graphene using density functional theory calculations and molecular dynamic simulations. Using the free energy perturbation method we will show how the addition of phenyl side groups to the core compound and functionalization of graphene affect the stability, mobility and conformation adopted by a dimer of bis-(Zn)salphen compound adsorbed on graphene surface and what it can reveal about the arrangement of chains of bis-(Zn)salphen polymer around carbon nanotubes during the self-assembly of microscale networks.
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Affiliation(s)
- Sergey Pyrlin
- Physics Center of Minho and Porto Universities (CF-UM-UP), University of Minho, Campus de Gualtar, 4710-057 Braga, Portugal
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10
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Pyo K, Matus MF, Malola S, Hulkko E, Alaranta J, Lahtinen T, Häkkinen H, Pettersson M. Tailoring the interaction between a gold nanocluster and a fluorescent dye by cluster size: creating a toolbox of range-adjustable pH sensors. NANOSCALE ADVANCES 2022; 4:4579-4588. [PMID: 36425249 PMCID: PMC9606730 DOI: 10.1039/d2na00487a] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/27/2022] [Accepted: 09/21/2022] [Indexed: 06/16/2023]
Abstract
We present a novel strategy for tailoring the fluorescent azadioxatriangulenium (KU) dye-based pH sensor to the target pH range by regulating the pK a value of the gold nanoclusters. Based on the correlation between the pK a and surface curvature of ligand-protected nanoparticles, the pK a value of the gold nanoclusters was controlled by size. In particular, three different-sized para-mercaptobenzoic acid (p-MBA) protected gold nanoclusters, Au25(p-MBA)18, Au102(p-MBA)44, and Au210-230(p-MBA)70-80 were used as the regulator for the pH range of the KU response. The negatively charged gold nanoclusters enabled the positively charged KU to bind to the surface, forming a complex and quenching the fluorescence of the KU by the energy transfer process. The fluorescence was restored after adjusting the surface charge of the gold nanocluster by controlling the solution pH. In addition, the KU exhibited a significantly different pH response behaviour for each gold nanocluster. Au210-230(p-MBA)70-80 showed a higher pH response range than Au102(p-MBA)44, which was intuitive. However, Au25(p-MBA)18 showed an unexpectedly high pH response behaviour. pK a titration measurement, molecular dynamics simulations, and essential dynamics analysis showed that small nanoclusters do not follow the scaling between the curvature and the pK a value. Instead, the behaviour is governed by the distribution and interaction of p-MBA ligands on the nanocluster surface. This work presents an effective design strategy for fabricating a range adjustable pH sensor by understanding the protonation behaviour of the ultrasmall gold nanoclusters in an atomic range.
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Affiliation(s)
- Kyunglim Pyo
- Department of Chemistry, Nanoscience Centre, University of Jyväskylä P. O. Box 35 FI-40014 Finland
| | - María Francisca Matus
- Department of Physics, Nanoscience Centre, University of Jyväskylä P. O. Box 35 FI-40014 Finland
| | - Sami Malola
- Department of Physics, Nanoscience Centre, University of Jyväskylä P. O. Box 35 FI-40014 Finland
| | - Eero Hulkko
- Department of Chemistry, Nanoscience Centre, University of Jyväskylä P. O. Box 35 FI-40014 Finland
| | - Johanna Alaranta
- Department of Chemistry, Nanoscience Centre, University of Jyväskylä P. O. Box 35 FI-40014 Finland
| | - Tanja Lahtinen
- Department of Chemistry, Nanoscience Centre, University of Jyväskylä P. O. Box 35 FI-40014 Finland
| | - Hannu Häkkinen
- Department of Chemistry, Nanoscience Centre, University of Jyväskylä P. O. Box 35 FI-40014 Finland
- Department of Physics, Nanoscience Centre, University of Jyväskylä P. O. Box 35 FI-40014 Finland
| | - Mika Pettersson
- Department of Chemistry, Nanoscience Centre, University of Jyväskylä P. O. Box 35 FI-40014 Finland
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