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Gangemi CMA, Barattucci A, Bonaccorsi PM. A Portrait of the OPE as a Biological Agent. Molecules 2021; 26:3088. [PMID: 34064279 PMCID: PMC8196911 DOI: 10.3390/molecules26113088] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2021] [Revised: 05/19/2021] [Accepted: 05/19/2021] [Indexed: 11/17/2022] Open
Abstract
Oligophenylene ethynylenes, known as OPEs, are a sequence of aromatic rings linked by triple bonds, the properties of which can be modulated by varying the length of the rigid main chain or/and the nature and position of the substituents on the aromatic units. They are luminescent molecules with high quantum yields and can be designed to enter a cell and act as antimicrobial and antiviral compounds, as biocompatible fluorescent probes directed towards target organelles in living cells, as labelling agents, as selective sensors for the detection of fibrillar and prefibrillar amyloid in the proteic field and in a fluorescence turn-on system for the detection of saccharides, as photosensitizers in photodynamic therapy (due to their capacity to highly induce toxicity after light activation), and as drug delivery systems. The antibacterial properties of OPEs have been the most studied against very popular and resistant pathogens, and in this paper the achievements of these studies are reviewed, together with almost all the other roles held by such oligomers. In the recent decade, their antifungal and antiviral effects have attracted the attention of researchers who believe OPEs to be possible biocides of the future. The review describes, for instance, the preliminary results obtained with OPEs against severe acute respiratory syndrome coronavirus 2, the virus responsible for the COVID-19 pandemic.
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Affiliation(s)
| | - Anna Barattucci
- Dipartimento di Scienze Chimiche, Biologiche, Farmaceutiche ed Ambientali (ChiBioFarAm), Università degli Studi di Messina, 98168 Messina, Italy; (C.M.A.G.); (P.M.B.)
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Wang J, Yang X, Zhao P, Deng H, Zhuo LG, Wang G, Yang Y, Wei H, Zhou Z, Liao W. Investigating Antibacterial Efficiency and Mechanism of Oligo-thiophenes under White Light and Specific Biocidal Activity against E. coli in Dark. ACS APPLIED BIO MATERIALS 2021; 4:3561-3570. [DOI: 10.1021/acsabm.1c00077] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Affiliation(s)
- Jing Wang
- Institute of Nuclear Physics and Chemistry, China Academy of Engineering Physics, 64 Mianshan Road, Mianyang, Sichuan 621900, People’s Republic of China
- Key Laboratory of Nuclear Medicine and Molecular Imaging of Sichuan Province, Mianyang, Sichuan 621900, People’s Republic of China
| | - Xia Yang
- Institute of Nuclear Physics and Chemistry, China Academy of Engineering Physics, 64 Mianshan Road, Mianyang, Sichuan 621900, People’s Republic of China
- Key Laboratory of Nuclear Medicine and Molecular Imaging of Sichuan Province, Mianyang, Sichuan 621900, People’s Republic of China
| | - Peng Zhao
- Institute of Nuclear Physics and Chemistry, China Academy of Engineering Physics, 64 Mianshan Road, Mianyang, Sichuan 621900, People’s Republic of China
| | - Hao Deng
- Department of Nuclear Medicine, The Affiliated Hospital of Southwest Medical University, Luzhou, Sichuan 646000, People’s Republic of China
| | - Lian-Gang Zhuo
- Institute of Nuclear Physics and Chemistry, China Academy of Engineering Physics, 64 Mianshan Road, Mianyang, Sichuan 621900, People’s Republic of China
- Key Laboratory of Nuclear Medicine and Molecular Imaging of Sichuan Province, Mianyang, Sichuan 621900, People’s Republic of China
| | - Guanquan Wang
- Institute of Nuclear Physics and Chemistry, China Academy of Engineering Physics, 64 Mianshan Road, Mianyang, Sichuan 621900, People’s Republic of China
- Key Laboratory of Nuclear Medicine and Molecular Imaging of Sichuan Province, Mianyang, Sichuan 621900, People’s Republic of China
| | - Yuchuan Yang
- Institute of Nuclear Physics and Chemistry, China Academy of Engineering Physics, 64 Mianshan Road, Mianyang, Sichuan 621900, People’s Republic of China
- Collaborative Innovation Center of Radiation Medicine of Jiangsu, Higher Education Institutions, Suzhou, Sichuan 215123, People’s Republic of China
- Key Laboratory of Nuclear Medicine and Molecular Imaging of Sichuan Province, Mianyang, Sichuan 621900, People’s Republic of China
| | - Hongyuan Wei
- Institute of Nuclear Physics and Chemistry, China Academy of Engineering Physics, 64 Mianshan Road, Mianyang, Sichuan 621900, People’s Republic of China
- Collaborative Innovation Center of Radiation Medicine of Jiangsu, Higher Education Institutions, Suzhou, Sichuan 215123, People’s Republic of China
- Key Laboratory of Nuclear Medicine and Molecular Imaging of Sichuan Province, Mianyang, Sichuan 621900, People’s Republic of China
| | - Zhijun Zhou
- Collaborative Innovation Center of Radiation Medicine of Jiangsu, Higher Education Institutions, Suzhou, Sichuan 215123, People’s Republic of China
| | - Wei Liao
- Institute of Nuclear Physics and Chemistry, China Academy of Engineering Physics, 64 Mianshan Road, Mianyang, Sichuan 621900, People’s Republic of China
- Key Laboratory of Nuclear Medicine and Molecular Imaging of Sichuan Province, Mianyang, Sichuan 621900, People’s Republic of China
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Martin TD, Brinkley G, Whitten DG, Chi EY, Evans DG. Computational Investigation of the Binding Dynamics of Oligo p-Phenylene Ethynylene Fluorescence Sensors and Aβ Oligomers. ACS Chem Neurosci 2020; 11:3761-3771. [PMID: 33141569 DOI: 10.1021/acschemneuro.0c00360] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
Amyloid protein aggregates are pathological hallmarks of neurodegenerative disorders such as Alzheimer's (AD) and Parkinson's (PD) diseases and are believed to be formed well before the onset of neurodegeneration and cognitive impairment. Monitoring the course of protein aggregation is thus vital to understanding and combating these diseases. We have recently demonstrated that a novel class of fluorescence sensors, oligomeric p-phenylene ethynylene (PE)-based electrolytes (OPEs) selectively bind to and detect prefibrillar and fibrillar aggregates of AD-related amyloid-β (Aβ) peptides over monomeric Aβ. In this study, we investigated the binding between two OPEs, anionic OPE12- and cationic OPE24+, and to two different β-sheet rich Aβ oligomers using classical all-atom molecular dynamics simulations. Our simulations have revealed a number of OPE binding sites on Aβ oligomer surfaces, and these sites feature hydrophobic amino acids as well as oppositely charged amino acids. Binding energy calculations show energetically favorable interactions between both anionic and cationic OPEs with Aβ oligomers. Moreover, OPEs bind as complexes as well as single molecules. Compared to free OPEs, Aβ protofibril bound OPEs show backbone planarization with restricted rotations and reduced hydration of the ethyl ester end groups. These characteristics, along with OPE complexation, align with known mechanisms of binding induced OPE fluorescence turn-on and spectral shifts from a quenched, unbound state in aqueous solutions. This study thus sheds light on the molecular-level details of OPE-Aβ protofibril interactions and provides a structural basis for fluorescence turn-on sensing modes of OPEs.
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Affiliation(s)
- Tye D. Martin
- Biomedical Engineering Graduate Program, University of New Mexico, Albuquerque 87131, New Mexico, United States
- Center for Biomedical Engineering, University of New Mexico, Albuquerque 87131, New Mexico, United States
| | - Gabriella Brinkley
- Department of Chemical Engineering, University of Minnesota Duluth, Duluth 55812, Minnesota, United States
| | - David G. Whitten
- Center for Biomedical Engineering, University of New Mexico, Albuquerque 87131, New Mexico, United States
- Department of Chemical and Biological Engineering, University of New Mexico, Albuquerque 87131, New Mexico, United States
| | - Eva Y. Chi
- Center for Biomedical Engineering, University of New Mexico, Albuquerque 87131, New Mexico, United States
- Department of Chemical and Biological Engineering, University of New Mexico, Albuquerque 87131, New Mexico, United States
| | - Deborah G. Evans
- Department of Chemistry and Chemical Biology, University of New Mexico, Albuquerque 87131, New Mexico, United States
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Whitten DG, Tang Y, Zhou Z, Yang J, Wang Y, Hill EH, Pappas HC, Donabedian PL, Chi EY. A Retrospective: 10 Years of Oligo(phenylene-ethynylene) Electrolytes: Demystifying Nanomaterials. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2019; 35:307-325. [PMID: 30056722 DOI: 10.1021/acs.langmuir.8b01810] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
In this retrospective, we first reviewed the synthesis of the oligo(phenylene-ethynylene) electrolytes (OPEs) we created in the past 10 years. Since the general antimicrobial activity of these OPEs had been reported in our previous account in Langmuir, we are focusing only on the unusual spectroscopic and photophysical properties of these OPEs and their complexes with anionic scaffolds and detergents in this Feature Article. We applied classical all-atom MD simulations to study the hydrogen bonding environment in the water surrounding the OPEs with and without detergents present. Our finding is that OPEs could form a unit cluster or unit aggregate with a few oppositely charged detergent molecules, indicating that the photostability and photoreactivity of these OPEs might be considerably altered with important consequences to their activity as antimicrobials and fluorescence-based sensors. Thus, in the following sections, we showed that OPE complexes with detergents exhibit enhanced light-activated biocidal activity compared to either OPE or detergent individually. We also found that similar complexes between certain OPEs and biolipids could be used to construct sensors for the enzyme activity. Finally, the OPEs could covalently bind to microsphere surfaces to make a bactericidal surface, which is simpler and more ordered than the surface grafted from microspheres with polyelectrolytes. In the Conclusions and Prospects section, we briefly summarize the properties of OPEs developed so far and future areas for investigation.
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Affiliation(s)
- David G Whitten
- Department of Chemical and Biological Engineering , University of New Mexico , Albuquerque , New Mexico 87131 , United States
| | - Yanli Tang
- Department of Chemical and Biological Engineering , University of New Mexico , Albuquerque , New Mexico 87131 , United States
| | - Zhijun Zhou
- Department of Chemical and Biological Engineering , University of New Mexico , Albuquerque , New Mexico 87131 , United States
| | - Jianzhong Yang
- Department of Chemical and Biological Engineering , University of New Mexico , Albuquerque , New Mexico 87131 , United States
| | - Ying Wang
- Department of Chemical and Biological Engineering , University of New Mexico , Albuquerque , New Mexico 87131 , United States
| | - Eric H Hill
- Department of Chemical and Biological Engineering , University of New Mexico , Albuquerque , New Mexico 87131 , United States
| | - Harry C Pappas
- Department of Chemical and Biological Engineering , University of New Mexico , Albuquerque , New Mexico 87131 , United States
| | - Patrick L Donabedian
- Department of Chemical and Biological Engineering , University of New Mexico , Albuquerque , New Mexico 87131 , United States
| | - Eva Y Chi
- Department of Chemical and Biological Engineering , University of New Mexico , Albuquerque , New Mexico 87131 , United States
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Martin TD, Hill EH, Whitten DG, Chi EY, Evans DG. Oligomeric Conjugated Polyelectrolytes Display Site-Preferential Binding to an MS2 Viral Capsid. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2016; 32:12542-12551. [PMID: 27464311 DOI: 10.1021/acs.langmuir.6b01667] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
Opportunistic bacteria and viruses are a worldwide health threat prompting the need to develop new targeting modalities. A class of novel synthetic poly(phenylene ethynylene) (PPE)-based oligomeric conjugated polyelectrolytes (OPEs) have demonstrated potent wide-spectrum biocidal activity. A subset of cationic OPEs display high antiviral activity against the MS2 bacteriophage. The oligomers have been found to inactivate the bacteriophage and perturb the morphology of the MS2 viral capsid. However, details of the initial binding and interactions between the OPEs and the viruses are not well understood. In this study, we use a multiscale computational approach, including random sampling, molecular dynamics, and electronic structure calculations, to gain an understanding of the molecular-level interactions of a series of OPEs that vary in length, charge, and functional groups with the MS2 capsid. Our results show that OPEs strongly bind to the MS2 capsid protein assembly with binding energies of up to -30 kcal/mol. Free-energy analysis shows that the binding is dominated by strong van der Waals interactions between the hydrophobic OPE backbone and the capsid surface and strong electrostatic free energy contributions between the OPE charged moieties and charged residues on the capsid surface. This knowledge provides molecular-level insight into how to tailor the OPEs to optimize viral capsid disruption and increase OPE efficacy to target amphiphilic protein coats of icosahedral-based viruses.
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Affiliation(s)
- Tye D Martin
- Department of Chemical and Biological Engineering and the Center for Biomedical Engineering, ‡The Nanoscience and Microsystems Engineering Program, and §Department of Chemistry and Chemical Biology, University of New Mexico , Albuquerque, New Mexico 87131, United States
| | - Eric H Hill
- Department of Chemical and Biological Engineering and the Center for Biomedical Engineering, ‡The Nanoscience and Microsystems Engineering Program, and §Department of Chemistry and Chemical Biology, University of New Mexico , Albuquerque, New Mexico 87131, United States
| | - David G Whitten
- Department of Chemical and Biological Engineering and the Center for Biomedical Engineering, ‡The Nanoscience and Microsystems Engineering Program, and §Department of Chemistry and Chemical Biology, University of New Mexico , Albuquerque, New Mexico 87131, United States
| | - Eva Y Chi
- Department of Chemical and Biological Engineering and the Center for Biomedical Engineering, ‡The Nanoscience and Microsystems Engineering Program, and §Department of Chemistry and Chemical Biology, University of New Mexico , Albuquerque, New Mexico 87131, United States
| | - Deborah G Evans
- Department of Chemical and Biological Engineering and the Center for Biomedical Engineering, ‡The Nanoscience and Microsystems Engineering Program, and §Department of Chemistry and Chemical Biology, University of New Mexico , Albuquerque, New Mexico 87131, United States
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Aggregation of cationic p-phenylene ethynylenes on Laponite clay in aqueous dispersions and solid films. J Colloid Interface Sci 2015; 449:347-56. [DOI: 10.1016/j.jcis.2014.12.006] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2014] [Revised: 12/03/2014] [Accepted: 12/03/2014] [Indexed: 12/24/2022]
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Lechner BD, Ebert H, Prehm M, Werner S, Meister A, Hause G, Beerlink A, Saalwächter K, Bacia K, Tschierske C, Blume A. Temperature-dependent in-plane structure formation of an X-shaped bolapolyphile within lipid bilayers. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2015; 31:2839-2850. [PMID: 25695502 DOI: 10.1021/la504903d] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Polyphilic compound B12 is an X-shaped molecule with a stiff aromatic core, flexible aliphatic side chains, and hydrophilic end groups. Forming a thermotropic triangular honeycomb phase in the bulk between 177 and 182 °C but no lyotropic phases, it is designed to fit into DPPC or DMPC lipid bilayers, in which it phase separates at room temperature, as observed in giant unilamellar vesicles (GUVs) by fluorescence microscopy. TEM investigations of bilayer aggregates support the incorporation of B12 into intact membranes. The temperature-dependent behavior of the mixed samples was followed by differential scanning calorimetry (DSC), FT-IR spectroscopy, fluorescence spectroscopy, and X-ray scattering. DSC results support in-membrane phase separation, where a reduced main transition and new B12-related transitions indicate the incorporation of lipids into the B12-rich phase. The phase separation was confirmed by X-ray scattering, where two different lamellar repeat distances are visible over a wide temperature range. Polarized ATR-FTIR and fluorescence anisotropy experiments support the transmembrane orientation of B12, and FT-IR spectra further prove a stepwise "melting" of the lipid chains. The data suggest that in the B12-rich domains the DPPC chains are still rigid and the B12 molecules interact with each other via π-π interactions. All results obtained at temperatures above 75 °C confirm the formation of a single, homogeneously mixed phase with freely mobile B12 molecules.
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Affiliation(s)
- Bob-Dan Lechner
- Institut für Chemie - Physikalische Chemie and ‡Institut für Chemie - Organische Chemie, Martin-Luther-Universität Halle-Wittenberg , D-06120 Halle (Saale), Germany
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Hill EH, Pappas HC, Evans DG, Whitten DG. Cationic oligo-p-phenylene ethynylenes form complexes with surfactants for long-term light-activated biocidal applications. Photochem Photobiol Sci 2014; 13:247-53. [PMID: 24149833 DOI: 10.1039/c3pp50277e] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Cationic oligo-p-phenylene ethynylenes are highly effective light-activated biocides that deal broad-spectrum damage to a variety of pathogens, including bacteria. A potential problem arising in the long-term usage of these compounds is photochemical breakdown, which nullifies their biocidal activity. Recent work has shown that these molecules complex with oppositely-charged surfactants, and that the resulting complexes are protected from photodegradation. In this manuscript, we determine the biocidal activity of an oligomer and a complex formed between it and sodium dodecyl sulfate. The complexes are able to withstand prolonged periods of irradiation, continuing to effectively kill both Gram-negative and Gram-positive bacteria, while the oligomer by itself loses its biocidal effectiveness quickly in the presence of light. In addition, damage and stress responses induced by these biocides in both E. coli and S. aureus are discussed. This work shows that complexation with surfactants is a viable method for long-term light-activated biocidal applications.
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Affiliation(s)
- Eric H Hill
- Center for Biomedical Engineering, Department of Chemical and Nuclear Engineering, University of New Mexico, Albuquerque, New Mexico 87131-1341, USA.
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Barattucci A, Chiara Aversa M, Deni E, Papalia T, Bonaccorsi P. Synthesis of Enantiomerically Pure Bis-Sulfinyl Substituted Phenylene Ethynylenes. Helv Chim Acta 2014. [DOI: 10.1002/hlca.201400144] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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Barattucci A, Deni E, Bonaccorsi P, Ceraolo MG, Papalia T, Santoro A, Sciortino MT, Puntoriero F. Oligo(phenylene ethynylene) glucosides: modulation of cellular uptake capacity preserving light ON. J Org Chem 2014; 79:5113-20. [PMID: 24815093 DOI: 10.1021/jo500661u] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
A new family of oligo(phenylene ethynylene) (OPE) glucosides has been prepared and characterized. Our results demonstrate that fine-tuning of their photophysical properties can be obtained by acting on the electronics of the core and molecular skeleton. Modulation of the hydrophobic chain length and substituents on the central moieties influences the bioaffinity too. In particular, introducing a NMe2 group on the aromatic central core affords a highly efficient biocompatible fluorescent probe that can be taken up in cytoplasmic vesicles of HEp-2 cells (cells from epidermoid carcinoma larynx tissue). The photophysical behavior, high quantum yield, and stability open the way to the use of the OPE family as stains for cellular imaging analysis by fluorescence microscopy.
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Affiliation(s)
- Anna Barattucci
- Dipartimento di Scienze Chimiche and SolarChem-Centro di Ricerca Interuniversitario per la Conversione Chimica dell'Energia Solare, Università di Messina , 98166 Messina, Italia
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Hill EH, Pappas HC, Whitten DG. Activating the antimicrobial activity of an anionic singlet-oxygen sensitizer through surfactant complexation. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2014; 30:5052-5056. [PMID: 24786342 DOI: 10.1021/la501230m] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
Cationic oligo-p-phenylene ethynylenes have shown much promise as broad-spectrum light-activated antimicrobial compounds against both Gram-positive and Gram-negative bacteria. The anionic varieties, however, have weak biocidal activity. In this study, a complex is formed between a weakly biocidal anionic oligomer and a cationic surfactant, and the effects on their biocidal activity against Gram-negative E. coli and Gram-positive S. aureus are explored. The enhancement in biocidal activity that is observed when the complex is irradiated suggests that interfacial surfactant gives the complex a net-positive charge, allowing it to associate strongly with the bacterial membrane. The results of this study demonstrate a method for the enhancement of biocidal activity of singlet-oxygen sensitizers and corroborate the use of surfactants as trans-membrane drug-delivery agents.
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Affiliation(s)
- Eric H Hill
- Center for Biomedical Engineering, Department of Chemical and Nuclear Engineering and the Nanoscience and Microsystems Engineering Program, University of New Mexico , Albuquerque, New Mexico 87131-1341, United States
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Hill EH, Evans DG, Whitten DG. The influence of structured interfacial water on the photoluminescence of carboxyester-terminated oligo-p-phenylene ethynylenes. J PHYS ORG CHEM 2014. [DOI: 10.1002/poc.3258] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Affiliation(s)
- Eric H. Hill
- Center for Biomedical Engineering, Department of Chemical and Nuclear Engineering; University of New Mexico; Albuquerque NM 87131-1341 USA
- The Nanoscience and Microsystems Engineering Program and Department of Chemistry and Chemical Biology; University of New Mexico; Albuquerque NM 87131-1341 USA
| | - Deborah G. Evans
- The Nanoscience and Microsystems Engineering Program and Department of Chemistry and Chemical Biology; University of New Mexico; Albuquerque NM 87131-1341 USA
| | - David G. Whitten
- Center for Biomedical Engineering, Department of Chemical and Nuclear Engineering; University of New Mexico; Albuquerque NM 87131-1341 USA
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Hill EH, Sanchez D, Evans DG, Whitten DG. Structural basis for aggregation mode of oligo-p-phenylene ethynylenes with ionic surfactants. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2013; 29:15732-15737. [PMID: 24279339 DOI: 10.1021/la4038827] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
In this letter, the aggregation modes of two classes of ionic p-phenylene ethynylene oligomers with oppositely charged surfactants are studied. The location of the ionic side chains was found to influence the type of aggregate formed when an equivalent number of surfactant molecules are added to solution. When the charged groups were located at the terminal ends of the molecule, strong H-aggregates were observed to form. Alternatively, when the ionic groups were both located on opposite sides of the central phenyl ring, the formation of J-aggregates was observed. Interestingly, as the surfactant concentration approaches the critical micelle concentration, the weakly bound aggregates are dissociated and the absorbance spectrum returns to what is observed in water. This study reveals the structural basis for aggregation effects between molecules based on the p-phenylene ethynylene backbone, and gives an understanding of how to influence the aggregation mode of similar compounds.
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Affiliation(s)
- Eric H Hill
- Center for Biomedical Engineering, Department of Chemical and Nuclear Engineering and ‡The Nanoscience and Microsystems Engineering Program and Department of Chemistry and Chemical Biology, University of New Mexico , Albuquerque, New Mexico 87131-1341, United States
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