1
|
Alkhaibari IS, Zhang X, Zhao J, Stonelake TM, Knighton RC, Horton PN, Coles SJ, Buurma NJ, Richards E, Pope SJA. Tuning Excited State Character in Iridium(III) Photosensitizers and Its Influence on TTA-UC. Inorg Chem 2024. [PMID: 38738860 DOI: 10.1021/acs.inorgchem.4c01003] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/14/2024]
Abstract
A series of mixed ligand, photoluminescent organometallic Ir(III) complexes have been synthesized to incorporate substituted 2-phenyl-1H-naphtho[2,3-d]imidazole cyclometalating ligands. The structures of three example complexes were categorically confirmed using X-ray crystallography each sharing very similar structural traits including evidence of interligand hydrogen bond contacts that account for the shielding effects observed in the 1H NMR spectra. The structural iterations of the cyclometalated ligand provide tuning of the principal electronic transitions that determine the visible absorption and emission properties of the complexes: emission can be tuned in the visible region between 550 and 610 nm and with triplet lifetimes up to 10 μs. The nature of the emitting state varies across the series of complexes, with different admixtures of ligand-centered and metal-to-ligand charge transfer triplet levels evident. Finally, the use of the complexes as photosensitizers in triplet-triplet annihilation energy upconversion (TTA-UC) was investigated in the solution state. The study showed that the complexes possessing the longest triplet lifetimes showed good viability as photosensitizers in TTA-UC. Therefore, the use of an electron-withdrawing group on the 2-phenyl-1H-naphtho[2,3-d]imidazole ligand framework can be used to rationally promote TTA-UC using this class of complex.
Collapse
Affiliation(s)
- Ibrahim S Alkhaibari
- School of Chemistry, Main Building, Cardiff University, Cardiff, Cymru/Wales CF10 3AT, U.K
- Department of Chemistry, College of Science, Qassim University, Buraydah 52571, Saudi Arabia
| | - Xue Zhang
- State Key Laboratory of Fine Chemicals, Frontiers Science Center for Smart Materials, School of Chemical Engineering, Dalian University of Technology, Dalian 116024, PR China
| | - Jianzhang Zhao
- State Key Laboratory of Fine Chemicals, Frontiers Science Center for Smart Materials, School of Chemical Engineering, Dalian University of Technology, Dalian 116024, PR China
| | - Thomas M Stonelake
- School of Chemistry, Main Building, Cardiff University, Cardiff, Cymru/Wales CF10 3AT, U.K
| | - Richard C Knighton
- School of Chemistry, University of Southampton, Highfield, Southampton SO17 1BJ, U.K
| | - Peter N Horton
- UK National Crystallographic Service, Chemistry, Faculty of Natural and Environmental Sciences, University of Southampton, Highfield, Southampton SO17 1BJ, U.K
| | - Simon J Coles
- UK National Crystallographic Service, Chemistry, Faculty of Natural and Environmental Sciences, University of Southampton, Highfield, Southampton SO17 1BJ, U.K
| | - Niklaas J Buurma
- School of Chemistry, Main Building, Cardiff University, Cardiff, Cymru/Wales CF10 3AT, U.K
| | - Emma Richards
- School of Chemistry, Main Building, Cardiff University, Cardiff, Cymru/Wales CF10 3AT, U.K
| | - Simon J A Pope
- School of Chemistry, Main Building, Cardiff University, Cardiff, Cymru/Wales CF10 3AT, U.K
| |
Collapse
|
2
|
Buurma NJ, Bagley SW. A focus on computer vision for non-contact monitoring of catalyst degradation and product formation kinetics. Chem Sci 2023; 14:10994-10996. [PMID: 37860646 PMCID: PMC10583670 DOI: 10.1039/d3sc90145a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2023] Open
Abstract
Chemists know the value of looking at a reaction for clues about reaction progress and success, but what-it-looks-like has never been quantified. Reid and co-workers (C. Yan, M. Cowie, C. Howcutt, K. M. P. Wheelhouse, N. S. Hodnett, M. Kollie, M. Gildea, M. H. Goodfellow and M. Reid, Chem. Sci., 2023, 14, 5323-5331, https://doi.org/10.1039/d2sc05702f) have developed an approach that uses camera footage of reactions to obtain quantitative descriptors of changes in reaction mixtures to support kinetic analysis.
Collapse
Affiliation(s)
- Niklaas J Buurma
- Physical Organic Chemistry Centre, School of Chemistry, Cardiff University Main Building, Park Place Cardiff CF10 3AT UK
| | - Scott W Bagley
- Pfizer Medicine Design Eastern Point Road Groton CT 06340 USA
| |
Collapse
|
3
|
Pritchard MF, Powell LC, Adams JYM, Menzies G, Khan S, Tøndervik A, Sletta H, Aarstad O, Skjåk-Bræk G, McKenna S, Buurma NJ, Farnell DJJ, Rye PD, Hill KE, Thomas DW. Structure-Activity Relationships of Low Molecular Weight Alginate Oligosaccharide Therapy against Pseudomonas aeruginosa. Biomolecules 2023; 13:1366. [PMID: 37759766 PMCID: PMC10527064 DOI: 10.3390/biom13091366] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2023] [Revised: 08/26/2023] [Accepted: 08/31/2023] [Indexed: 09/29/2023] Open
Abstract
Low molecular weight alginate oligosaccharides have been shown to exhibit anti-microbial activity against a range of multi-drug resistant bacteria, including Pseudomonas aeruginosa. Previous studies suggested that the disruption of calcium (Ca2+)-DNA binding within bacterial biofilms and dysregulation of quorum sensing (QS) were key factors in these observed effects. To further investigate the contribution of Ca2+ binding, G-block (OligoG) and M-block alginate oligosaccharides (OligoM) with comparable average size DPn 19 but contrasting Ca2+ binding properties were prepared. Fourier-transform infrared spectroscopy demonstrated prolonged binding of alginate oligosaccharides to the pseudomonal cell membrane even after hydrodynamic shear treatment. Molecular dynamics simulations and isothermal titration calorimetry revealed that OligoG exhibited stronger interactions with bacterial LPS than OligoM, although this difference was not mirrored by differential reductions in bacterial growth. While confocal laser scanning microscopy showed that both agents demonstrated similar dose-dependent reductions in biofilm formation, OligoG exhibited a stronger QS inhibitory effect and increased potentiation of the antibiotic azithromycin in minimum inhibitory concentration and biofilm assays. This study demonstrates that the anti-microbial effects of alginate oligosaccharides are not purely influenced by Ca2+-dependent processes but also by electrostatic interactions that are common to both G-block and M-block structures.
Collapse
Affiliation(s)
- Manon F. Pritchard
- Advanced Therapies Group, School of Dentistry, Cardiff University, Cardiff CF14 4XY, UK; (L.C.P.); (J.Y.M.A.); (S.K.); (S.M.); (D.J.J.F.); (K.E.H.); (D.W.T.)
| | - Lydia C. Powell
- Advanced Therapies Group, School of Dentistry, Cardiff University, Cardiff CF14 4XY, UK; (L.C.P.); (J.Y.M.A.); (S.K.); (S.M.); (D.J.J.F.); (K.E.H.); (D.W.T.)
- Microbiology and Infectious Disease Group, Swansea University Medical School, Swansea SA2 8PP, UK
| | - Jennifer Y. M. Adams
- Advanced Therapies Group, School of Dentistry, Cardiff University, Cardiff CF14 4XY, UK; (L.C.P.); (J.Y.M.A.); (S.K.); (S.M.); (D.J.J.F.); (K.E.H.); (D.W.T.)
| | - Georgina Menzies
- School of Biosciences, Cardiff University, Cardiff CF10 3AX, UK;
| | - Saira Khan
- Advanced Therapies Group, School of Dentistry, Cardiff University, Cardiff CF14 4XY, UK; (L.C.P.); (J.Y.M.A.); (S.K.); (S.M.); (D.J.J.F.); (K.E.H.); (D.W.T.)
| | - Anne Tøndervik
- Department of Bioprocess Technology, SINTEF Materials and Chemistry, N-7465 Trondheim, Norway; (A.T.); (H.S.)
| | - Håvard Sletta
- Department of Bioprocess Technology, SINTEF Materials and Chemistry, N-7465 Trondheim, Norway; (A.T.); (H.S.)
| | - Olav Aarstad
- Department of Biotechnology, Norwegian University of Science and Technology, N-7491 Trondheim, Norway; (O.A.); (G.S.-B.)
| | - Gudmund Skjåk-Bræk
- Department of Biotechnology, Norwegian University of Science and Technology, N-7491 Trondheim, Norway; (O.A.); (G.S.-B.)
| | - Stephen McKenna
- Advanced Therapies Group, School of Dentistry, Cardiff University, Cardiff CF14 4XY, UK; (L.C.P.); (J.Y.M.A.); (S.K.); (S.M.); (D.J.J.F.); (K.E.H.); (D.W.T.)
| | - Niklaas J. Buurma
- Physical Organic Chemistry Centre, School of Chemistry, Cardiff University, Cardiff CF10 3AT, UK;
| | - Damian J. J. Farnell
- Advanced Therapies Group, School of Dentistry, Cardiff University, Cardiff CF14 4XY, UK; (L.C.P.); (J.Y.M.A.); (S.K.); (S.M.); (D.J.J.F.); (K.E.H.); (D.W.T.)
| | - Philip D. Rye
- AlgiPharma AS, Industriveien 33, N-1337 Sandvika, Norway;
| | - Katja E. Hill
- Advanced Therapies Group, School of Dentistry, Cardiff University, Cardiff CF14 4XY, UK; (L.C.P.); (J.Y.M.A.); (S.K.); (S.M.); (D.J.J.F.); (K.E.H.); (D.W.T.)
| | - David W. Thomas
- Advanced Therapies Group, School of Dentistry, Cardiff University, Cardiff CF14 4XY, UK; (L.C.P.); (J.Y.M.A.); (S.K.); (S.M.); (D.J.J.F.); (K.E.H.); (D.W.T.)
| |
Collapse
|
4
|
Saud Z, Tyrrell VJ, Zaragkoulias A, Protty MB, Statkute E, Rubina A, Bentley K, White DA, Rodrigues PDS, Murphy RC, Köfeler H, Griffiths WJ, Alvarez-Jarreta J, Brown RW, Newcombe RG, Heyman J, Pritchard M, Mcleod RW, Arya A, Lynch CA, Owens D, Jenkins PV, Buurma NJ, O'Donnell VB, Thomas DW, Stanton RJ. The SARS-CoV2 envelope differs from host cells, exposes procoagulant lipids, and is disrupted in vivo by oral rinses. J Lipid Res 2022; 63:100208. [PMID: 35436499 PMCID: PMC9010312 DOI: 10.1016/j.jlr.2022.100208] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2022] [Revised: 03/23/2022] [Accepted: 04/04/2022] [Indexed: 12/14/2022] Open
Abstract
The lipid envelope of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is an essential component of the virus; however, its molecular composition is undetermined. Addressing this knowledge gap could support the design of antiviral agents as well as further our understanding of viral-host protein interactions, infectivity, pathogenicity, and innate immune system clearance. Lipidomics revealed that the virus envelope comprised mainly phospholipids (PLs), with some cholesterol and sphingolipids, and with cholesterol/phospholipid ratio similar to lysosomes. Unlike cellular membranes, procoagulant amino-PLs were present on the external side of the viral envelope at levels exceeding those on activated platelets. Accordingly, virions directly promoted blood coagulation. To investigate whether these differences could enable selective targeting of the viral envelope in vivo, we tested whether oral rinses containing lipid-disrupting chemicals could reduce infectivity. Products containing PL-disrupting surfactants (such as cetylpyridinium chloride) met European virucidal standards in vitro; however, components that altered the critical micelle concentration reduced efficacy, and products containing essential oils, povidone-iodine, or chlorhexidine were ineffective. This result was recapitulated in vivo, where a 30-s oral rinse with cetylpyridinium chloride mouthwash eliminated live virus in the oral cavity of patients with coronavirus disease 19 for at least 1 h, whereas povidone-iodine and saline mouthwashes were ineffective. We conclude that the SARS-CoV-2 lipid envelope i) is distinct from the host plasma membrane, which may enable design of selective antiviral approaches; ii) contains exposed phosphatidylethanolamine and phosphatidylserine, which may influence thrombosis, pathogenicity, and inflammation; and iii) can be selectively targeted in vivo by specific oral rinses.
Collapse
Affiliation(s)
- Zack Saud
- Division of Infection & Immunity, School of Medicine, Cardiff University, Cardiff, United Kingdom
| | - Victoria J Tyrrell
- Division of Infection & Immunity, School of Medicine, Cardiff University, Cardiff, United Kingdom
| | - Andreas Zaragkoulias
- Division of Infection & Immunity, School of Medicine, Cardiff University, Cardiff, United Kingdom
| | - Majd B Protty
- Division of Infection & Immunity, School of Medicine, Cardiff University, Cardiff, United Kingdom
| | - Evelina Statkute
- Division of Infection & Immunity, School of Medicine, Cardiff University, Cardiff, United Kingdom
| | - Anzelika Rubina
- Division of Infection & Immunity, School of Medicine, Cardiff University, Cardiff, United Kingdom
| | - Kirsten Bentley
- Division of Infection & Immunity, School of Medicine, Cardiff University, Cardiff, United Kingdom
| | - Daniel A White
- Division of Infection & Immunity, School of Medicine, Cardiff University, Cardiff, United Kingdom
| | | | - Robert C Murphy
- Department of Pharmacology, University of Colorado Denver, Aurora, CO, USA
| | - Harald Köfeler
- Core Facility Mass Spectrometry, Medical University of Graz, Graz, Austria
| | | | - Jorge Alvarez-Jarreta
- Division of Infection & Immunity, School of Medicine, Cardiff University, Cardiff, United Kingdom
| | - Richard William Brown
- ENT Department, Betsi Cadwaladr University Health Board, Wrexham Maelor Hospital, Wrexham, United Kingdom
| | - Robert G Newcombe
- Division of Population Medicine, School of Medicine, Cardiff University, Cardiff, United Kingdom
| | - James Heyman
- Division of Surgery, Cardiff and Vale University Health Board, Cardiff, United Kingdom
| | - Manon Pritchard
- Advanced Therapies Group, School of Dentistry, Cardiff University, Cardiff, United Kingdom
| | - Robert Wj Mcleod
- Division of Surgery, Cardiff and Vale University Health Board, Cardiff, United Kingdom
| | - Arvind Arya
- ENT Department, Betsi Cadwaladr University Health Board, Wrexham Maelor Hospital, Wrexham, United Kingdom
| | - Ceri-Ann Lynch
- Anaesthetics and Critical Care Directorate, Cwm Taf University Health Board, Royal Glamorgan Hospital, Llantrisant, United Kingdom
| | - David Owens
- Division of Surgery, Cardiff and Vale University Health Board, Cardiff, United Kingdom
| | - P Vince Jenkins
- Haemostasis Diagnosis and Research, University Hospital Wales, Cardiff, United Kingdom
| | - Niklaas J Buurma
- Physical Organic Chemistry Centre, School of Chemistry, Cardiff University, Cardiff, United Kingdom
| | - Valerie B O'Donnell
- Division of Infection & Immunity, School of Medicine, Cardiff University, Cardiff, United Kingdom.
| | - David W Thomas
- Advanced Therapies Group, School of Dentistry, Cardiff University, Cardiff, United Kingdom.
| | - Richard J Stanton
- Division of Infection & Immunity, School of Medicine, Cardiff University, Cardiff, United Kingdom.
| |
Collapse
|
5
|
Dasgupta A, Stefkova K, Babaahmadi R, Yates BF, Buurma NJ, Ariafard A, Richards E, Melen RL. Site-Selective C sp3-C sp/C sp3-C sp2 Cross-Coupling Reactions Using Frustrated Lewis Pairs. J Am Chem Soc 2021; 143:4451-4464. [PMID: 33719443 PMCID: PMC8041292 DOI: 10.1021/jacs.1c01622] [Citation(s) in RCA: 21] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2021] [Indexed: 02/08/2023]
Abstract
The donor-acceptor ability of frustrated Lewis pairs (FLPs) has led to widespread applications in organic synthesis. Single electron transfer from a donor Lewis base to an acceptor Lewis acid can generate a frustrated radical pair (FRP) depending on the substrate and energy required (thermal or photochemical) to promote an FLP into an FRP system. Herein, we report the Csp3-Csp cross-coupling reaction of aryl esters with terminal alkynes using the B(C6F5)3/Mes3P FLP. Significantly, when the 1-ethynyl-4-vinylbenzene substrate was employed, the exclusive formation of Csp3-Csp cross-coupled products was observed. However, when 1-ethynyl-2-vinylbenzene was employed, solvent-dependent site-selective Csp3-Csp or Csp3-Csp2 cross-coupling resulted. The nature of these reaction pathways and their selectivity has been investigated by extensive electron paramagnetic resonance (EPR) studies, kinetic studies, and density functional theory (DFT) calculations both to elucidate the mechanism of these coupling reactions and to explain the solvent-dependent site selectivity.
Collapse
Affiliation(s)
- Ayan Dasgupta
- Cardiff
Catalysis Institute, School of Chemistry, Cardiff University, Main Building, Park Place, Cardiff CF10 3AT, Cymru/Wales, United Kingdom
| | - Katarina Stefkova
- Cardiff
Catalysis Institute, School of Chemistry, Cardiff University, Main Building, Park Place, Cardiff CF10 3AT, Cymru/Wales, United Kingdom
| | - Rasool Babaahmadi
- School
of Natural Sciences-Chemistry, University
of Tasmania Private Bag 75, Hobart, Tasmania 7001, Australia
| | - Brian F. Yates
- School
of Natural Sciences-Chemistry, University
of Tasmania Private Bag 75, Hobart, Tasmania 7001, Australia
| | - Niklaas J. Buurma
- Cardiff
Catalysis Institute, School of Chemistry, Cardiff University, Main Building, Park Place, Cardiff CF10 3AT, Cymru/Wales, United Kingdom
| | - Alireza Ariafard
- School
of Natural Sciences-Chemistry, University
of Tasmania Private Bag 75, Hobart, Tasmania 7001, Australia
| | - Emma Richards
- Cardiff
Catalysis Institute, School of Chemistry, Cardiff University, Main Building, Park Place, Cardiff CF10 3AT, Cymru/Wales, United Kingdom
| | - Rebecca L. Melen
- Cardiff
Catalysis Institute, School of Chemistry, Cardiff University, Main Building, Park Place, Cardiff CF10 3AT, Cymru/Wales, United Kingdom
| |
Collapse
|
6
|
Nelson A, Phipps RJ, Crane GJ, Venanzi NAE, Lockley WJS, Tredwell M, Buurma NJ, Ballard A, Ahmad HO, Narduolo S, Rosa L, Chand N, Cosgrove DA, Varkonyi P, Asaad N, Tomasi S, Leach AG, Summerhill N, Bloom J, Newby M, Madden S, Roman D, Exner RM, Cortezon-Tamarit F, Ge H, Paisey S, Pascu SI, de Rosales RTM, Hailes HC, Wang Y, Zhao J, Méndez-Sánchez D, Rodan R, Subrizi F, Lichman BR, Keep NH, Ward JM, Harris M, Lamb M, Wilson V, Iafrate P, Bulat F, Néves AA, Hesse F, Hu DE, Aigbirhio F, Leeper FJ, Brindle KM, Rowbotham JS, Urata K, Reeve HA, Vincent KA, Hueting R. Abstracts of the 28 th International Isotope Society (UK group) Symposium: The Synthesis & Applications of Labelled Compounds 2019. J Labelled Comp Radiopharm 2020; 63:608-617. [PMID: 32678462 DOI: 10.1002/jlcr.3867] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2020] [Accepted: 04/23/2020] [Indexed: 11/08/2022]
|
7
|
Ballard A, Narduolo S, Ahmed HO, Keymer NI, Asaad N, Cosgrove DA, Buurma NJ, Leach AG. Frontispiece: Racemisation in Chemistry and Biology. Chemistry 2020. [DOI: 10.1002/chem.202081761] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Affiliation(s)
- Andrew Ballard
- School of ChemistryCardiff University Main Building, Park Place Cardiff CF10 3AT UK
| | - Stefania Narduolo
- School of ChemistryCardiff University Main Building, Park Place Cardiff CF10 3AT UK
| | - Hiwa O. Ahmed
- School of ChemistryCardiff University Main Building, Park Place Cardiff CF10 3AT UK
- Pharmaceutical Chemistry DepartmentHawler Medical University Erbil Kurdistan Region Iraq
| | - Nathaniel I. Keymer
- School of ChemistryCardiff University Main Building, Park Place Cardiff CF10 3AT UK
| | - Nabil Asaad
- AstraZeneca Mereside, Alderley Park Macclesfield SK10 4TG UK
| | | | - Niklaas J. Buurma
- School of ChemistryCardiff University Main Building, Park Place Cardiff CF10 3AT UK
| | - Andrew G. Leach
- Division of Pharmacy and OptometryUniversity of Manchester Oxford Road Manchester M13 9PL UK
| |
Collapse
|
8
|
Ballard A, Narduolo S, Ahmed HO, Keymer NI, Asaad N, Cosgrove DA, Buurma NJ, Leach AG. Racemisation in Chemistry and Biology. Chemistry 2020; 26:3661-3687. [PMID: 31709642 DOI: 10.1002/chem.201903917] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2019] [Indexed: 11/09/2022]
Abstract
The two enantiomers of a compound often have profoundly different biological properties and thus their liability to racemisation in aqueous solutions is an important piece of information. The authors reviewed the available data concerning the process of racemisation in vivo, in the presence of biological molecules (e.g., racemase enzymes, serum albumin, cofactors and derivatives) and under purely chemical but aqueous conditions (acid, base and other aqueous systems). Mechanistic studies are described critically in light of reported kinetic data. The types of experimental measurement that can be used to effectively determine rate constants of racemisation in various conditions are discussed and the data they provide is summarised. The proposed origins of enzymatic racemisation are presented and suggest ways to promote the process that are different from processes taking place in bulk water. Experimental and computational studies that provide understanding and quantitative predictions of racemisation risk are also presented.
Collapse
Affiliation(s)
- Andrew Ballard
- School of Chemistry, Cardiff University, Main Building, Park Place, Cardiff, CF10 3AT, UK
| | - Stefania Narduolo
- School of Chemistry, Cardiff University, Main Building, Park Place, Cardiff, CF10 3AT, UK
| | - Hiwa O Ahmed
- School of Chemistry, Cardiff University, Main Building, Park Place, Cardiff, CF10 3AT, UK.,Pharmaceutical Chemistry Department, Hawler Medical University, Erbil, Kurdistan Region, Iraq
| | - Nathaniel I Keymer
- School of Chemistry, Cardiff University, Main Building, Park Place, Cardiff, CF10 3AT, UK
| | - Nabil Asaad
- AstraZeneca, Mereside, Alderley Park, Macclesfield, SK10 4TG, UK
| | | | - Niklaas J Buurma
- School of Chemistry, Cardiff University, Main Building, Park Place, Cardiff, CF10 3AT, UK
| | - Andrew G Leach
- Division of Pharmacy and Optometry, University of Manchester, Oxford Road, Manchester, M13 9PL, UK
| |
Collapse
|
9
|
Day AH, Übler MH, Best HL, Lloyd-Evans E, Mart RJ, Fallis IA, Allemann RK, Al-Wattar EAH, Keymer NI, Buurma NJ, Pope SJA. Targeted cell imaging properties of a deep red luminescent iridium(iii) complex conjugated with a c-Myc signal peptide. Chem Sci 2020; 11:1599-1606. [PMID: 32206278 PMCID: PMC7069228 DOI: 10.1039/c9sc05568a] [Citation(s) in RCA: 24] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2019] [Accepted: 12/14/2019] [Indexed: 12/05/2022] Open
Abstract
A nuclear localisation sequence (NLS) peptide, PAAKRVKLD, derived from the human c-Myc regulator gene, has been functionalised with a long wavelength (λ ex = 550 nm; λ em = 677 nm) cyclometalated organometallic iridium(iii) complex to give the conjugate Ir-CMYC. Confocal fluorescence microscopy studies on human fibroblast cells imaged after 18-24 h incubation show that Ir-CMYC concentrations of 80-100 μM promote good cell uptake and nuclear localisation, which was confirmed though co-localisation studies using Hoechst 33342. In comparison, a structurally related, photophysically analogous iridium(iii) complex lacking the peptide sequence, Ir-PYR, showed very different biological behaviour, with no evidence of nuclear, lysosomal or autophagic vesicle localisation and significantly increased toxicity to the cells at concentrations >10 μM that induced mitochondrial dysfunction. Supporting UV-visible and circular dichroism spectroscopic studies show that Ir-PYR and Ir-CMYC display similarly low affinities for DNA (ca. 103 M-1), consistent with electrostatic binding. Therefore the translocation and nuclear uptake properties of Ir-CMYC are attributed to the presence of the PAAKRVKLD nuclear localisation sequence in this complex.
Collapse
Affiliation(s)
- Adam H Day
- School of Chemistry , Cardiff University , Main Building , Cardiff , CF10 3AT , UK .
| | - Martin H Übler
- School of Chemistry , Cardiff University , Main Building , Cardiff , CF10 3AT , UK .
| | - Hannah L Best
- School of Biosciences , Cardiff University , Sir Martin Evans Building , Cardiff , UK
| | - Emyr Lloyd-Evans
- School of Biosciences , Cardiff University , Sir Martin Evans Building , Cardiff , UK
| | - Robert J Mart
- School of Chemistry , Cardiff University , Main Building , Cardiff , CF10 3AT , UK .
| | - Ian A Fallis
- School of Chemistry , Cardiff University , Main Building , Cardiff , CF10 3AT , UK .
| | - Rudolf K Allemann
- School of Chemistry , Cardiff University , Main Building , Cardiff , CF10 3AT , UK .
| | - Eman A H Al-Wattar
- School of Chemistry , Cardiff University , Main Building , Cardiff , CF10 3AT , UK .
| | - Nathaniel I Keymer
- School of Chemistry , Cardiff University , Main Building , Cardiff , CF10 3AT , UK .
| | - Niklaas J Buurma
- School of Chemistry , Cardiff University , Main Building , Cardiff , CF10 3AT , UK .
| | - Simon J A Pope
- School of Chemistry , Cardiff University , Main Building , Cardiff , CF10 3AT , UK .
| |
Collapse
|
10
|
Ballard A, Narduolo S, Ahmad HO, Cosgrove DA, Leach AG, Buurma NJ. The problem of racemization in drug discovery and tools to predict it. Expert Opin Drug Discov 2019; 14:527-539. [PMID: 30882254 DOI: 10.1080/17460441.2019.1588881] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
INTRODUCTION Racemization has long been an ignored risk in drug development, probably because of a lack of convenient access to good tools for its detection and an absence of methods to predict racemization risk. As a result, the potential effects of racemization have been systematically underestimated. Areas covered: Herein, the potential effects of racemization are discussed through a review of drugs for which activity and side effects for both enantiomers are known. Subsequently, drugs known to racemize are discussed and the authors review methods to predict racemization risk. Application of a method quantitatively predicting racemization risk to databases of compounds from the medicinal chemistry literature shows that success in clinical trials is negatively correlated with racemization risk. Expert opinion: It is envisioned that a quantitative method of predicting racemization risk will remove a blind spot from the drug development pipeline. Removal of the blind spot will make drug development more efficient and result in less late-stage attrition of the drug pipeline.
Collapse
Affiliation(s)
- Andrew Ballard
- a Physical Organic Chemistry Centre , School of Chemistry, Cardiff University , Cardiff , UK
| | - Stefania Narduolo
- a Physical Organic Chemistry Centre , School of Chemistry, Cardiff University , Cardiff , UK
| | - Hiwa O Ahmad
- a Physical Organic Chemistry Centre , School of Chemistry, Cardiff University , Cardiff , UK.,b Pharmaceutical Chemistry Department , College of Pharmacy, Hawler Medical University , Erbil , Kurdistan Region , Iraq
| | | | - Andrew G Leach
- d School of Pharmacy and Biomolecular Sciences , Liverpool John Moores University , Liverpool , UK
| | - Niklaas J Buurma
- a Physical Organic Chemistry Centre , School of Chemistry, Cardiff University , Cardiff , UK
| |
Collapse
|
11
|
Abstract
I2CITC allows the analysis of isothermal titration calorimetry (ITC) data for complex coupled equilibria. Here we describe how, using I2CITC, ITC data for systems involving a self-aggregating ligand and a host offering one or two binding sites can be analyzed, how interaction models can be tested, and how confidence intervals for the optimized parameters can be determined.
Collapse
Affiliation(s)
- Ibrahim Q Saeed
- Department of Chemistry, College of Science, Salahaddin University, Erbil, Kurdistan Region, Iraq
| | - Niklaas J Buurma
- Physical Organic Chemistry Centre, School of Chemistry, Cardiff University, Cardiff, UK.
| |
Collapse
|
12
|
Powell LC, Pritchard MF, Ferguson EL, Powell KA, Patel SU, Rye PD, Sakellakou SM, Buurma NJ, Brilliant CD, Copping JM, Menzies GE, Lewis PD, Hill KE, Thomas DW. Targeted disruption of the extracellular polymeric network of Pseudomonas aeruginosa biofilms by alginate oligosaccharides. NPJ Biofilms Microbiomes 2018; 4:13. [PMID: 29977590 PMCID: PMC6026129 DOI: 10.1038/s41522-018-0056-3] [Citation(s) in RCA: 102] [Impact Index Per Article: 17.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2017] [Revised: 05/20/2018] [Accepted: 06/06/2018] [Indexed: 11/29/2022] Open
Abstract
Acquisition of a mucoid phenotype by Pseudomonas sp. in the lungs of cystic fibrosis (CF) patients, with subsequent over-production of extracellular polymeric substance (EPS), plays an important role in mediating the persistence of multi-drug resistant (MDR) infections. The ability of a low molecular weight (Mn = 3200 g mol−1) alginate oligomer (OligoG CF-5/20) to modify biofilm structure of mucoid Pseudomonas aeruginosa (NH57388A) was studied in vitro using scanning electron microscopy (SEM), confocal laser scanning microscopy (CLSM) with Texas Red (TxRd®)-labelled OligoG and EPS histochemical staining. Structural changes in treated biofilms were quantified using COMSTAT image-analysis software of CLSM z-stack images, and nanoparticle diffusion. Interactions between the oligomers, Ca2+ and DNA were studied using molecular dynamics (MD) simulations, Fourier transform infrared spectroscopy (FTIR) and isothermal titration calorimetry (ITC). Imaging demonstrated that OligoG treatment (≥0.5%) inhibited biofilm formation, revealing a significant reduction in both biomass and biofilm height (P < 0.05). TxRd®-labelled oligomers readily diffused into established (24 h) biofilms. OligoG treatment (≥2%) induced alterations in the EPS of established biofilms; significantly reducing the structural quantities of EPS polysaccharides, and extracellular (e)DNA (P < 0.05) with a corresponding increase in nanoparticle diffusion (P < 0.05) and antibiotic efficacy against established biofilms. ITC demonstrated an absence of rapid complex formation between DNA and OligoG and confirmed the interactions of OligoG with Ca2+ evident in FTIR and MD modelling. The ability of OligoG to diffuse into biofilms, potentiate antibiotic activity, disrupt DNA-Ca2+-DNA bridges and biofilm EPS matrix highlights its potential for the treatment of biofilm-related infections. Small carbohydrate molecules derived from marine algae show potential for inhibiting biofilm formation in multi-drug resistant infections. A research team led by Lydia Powell at Cardiff University, UK, investigated the action of carbohydrates called alginate oligosaccharides, composed of a small number of linked sugar molecules. The oligosaccharides modified and disrupted the structure of cultured biofilms of Pseudomonas aeruginosa, the cause of many serious drug resistant infections. This effect significantly inhibited the formation and maintenance of the biofilm state, which is known to be a crucial factor allowing the bacteria to resist drug treatment. Antibiotics proved more effective following the oligosaccharide intervention. The researchers uncovered key molecular details involved in the ability of the oligosaccharides to diffuse into and disrupt biofilms. The therapeutic potential of these small carbohydrates is currently being investigated in clinical trials.
Collapse
Affiliation(s)
- Lydia C Powell
- 1Advanced Therapies Group, Cardiff University School of Dentistry, Heath Park, Cardiff, CF14 4XY UK
| | - Manon F Pritchard
- 1Advanced Therapies Group, Cardiff University School of Dentistry, Heath Park, Cardiff, CF14 4XY UK
| | - Elaine L Ferguson
- 1Advanced Therapies Group, Cardiff University School of Dentistry, Heath Park, Cardiff, CF14 4XY UK
| | - Kate A Powell
- 1Advanced Therapies Group, Cardiff University School of Dentistry, Heath Park, Cardiff, CF14 4XY UK
| | - Shree U Patel
- 1Advanced Therapies Group, Cardiff University School of Dentistry, Heath Park, Cardiff, CF14 4XY UK
| | | | | | - Niklaas J Buurma
- 3Physical Organic Chemistry Centre, School of Chemistry, Cardiff University, Cardiff, UK
| | | | - Jack M Copping
- 4Respiratory Diagnostics Group, Swansea University, Swansea, UK
| | | | - Paul D Lewis
- 4Respiratory Diagnostics Group, Swansea University, Swansea, UK
| | - Katja E Hill
- 1Advanced Therapies Group, Cardiff University School of Dentistry, Heath Park, Cardiff, CF14 4XY UK
| | - David W Thomas
- 1Advanced Therapies Group, Cardiff University School of Dentistry, Heath Park, Cardiff, CF14 4XY UK
| |
Collapse
|
13
|
Ballard A, Ahmad HO, Narduolo S, Rosa L, Chand N, Cosgrove DA, Varkonyi P, Asaad N, Tomasi S, Buurma NJ, Leach AG. Quantitative Prediction of Rate Constants for Aqueous Racemization To Avoid Pointless Stereoselective Syntheses. Angew Chem Int Ed Engl 2018; 57:982-985. [PMID: 29072355 PMCID: PMC5820753 DOI: 10.1002/anie.201709163] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2017] [Indexed: 11/22/2022]
Abstract
Racemization has a large impact upon the biological properties of molecules but the chemical scope of compounds with known rate constants for racemization in aqueous conditions was hitherto limited. To address this remarkable blind spot, we have measured the kinetics for racemization of 28 compounds using circular dichroism and 1H NMR spectroscopy. We show that rate constants for racemization (measured by ourselves and others) correlate well with deprotonation energies from quantum mechanical (QM) and group contribution calculations. Such calculations thus provide predictions of the second‐order rate constants for general‐base‐catalyzed racemization that are usefully accurate. When applied to recent publications describing the stereoselective synthesis of compounds of purported biological value, the calculations reveal that racemization would be sufficiently fast to render these expensive syntheses pointless.
Collapse
Affiliation(s)
- Andrew Ballard
- Physical Organic Chemistry Centre, School of Chemistry, Cardiff University, Main Building, Park Place, Cardiff, CF10 3AT, UK
| | - Hiwa O Ahmad
- Physical Organic Chemistry Centre, School of Chemistry, Cardiff University, Main Building, Park Place, Cardiff, CF10 3AT, UK.,Pharmaceutical Chemistry Department, College of Pharmacy, Hawler Medical University, Erbil, Kurdistan Region, Iraq
| | - Stefania Narduolo
- Physical Organic Chemistry Centre, School of Chemistry, Cardiff University, Main Building, Park Place, Cardiff, CF10 3AT, UK
| | - Lucy Rosa
- AstraZeneca Pharmaceuticals, Mereside, Alderley Park, Macclesfield, SK10 4TG, UK
| | - Nikki Chand
- AstraZeneca Pharmaceuticals, Mereside, Alderley Park, Macclesfield, SK10 4TG, UK
| | - David A Cosgrove
- AstraZeneca Pharmaceuticals, Mereside, Alderley Park, Macclesfield, SK10 4TG, UK
| | - Peter Varkonyi
- AstraZeneca R+D, Pepparedsleden 1, 43183, Mölndal, Sweden
| | - Nabil Asaad
- AstraZeneca Pharmaceuticals, Mereside, Alderley Park, Macclesfield, SK10 4TG, UK
| | - Simone Tomasi
- AstraZeneca, Charter Way, Silk Road Business Park, Macclesfield, SK10 2NA, UK
| | - Niklaas J Buurma
- Physical Organic Chemistry Centre, School of Chemistry, Cardiff University, Main Building, Park Place, Cardiff, CF10 3AT, UK
| | - Andrew G Leach
- School of Pharmacy and Biomolecular Sciences, Liverpool John Moores University, Liverpool, L3 3AF, UK
| |
Collapse
|
14
|
Ballard A, Ahmad HO, Narduolo S, Rosa L, Chand N, Cosgrove DA, Varkonyi P, Asaad N, Tomasi S, Buurma NJ, Leach AG. Quantitative Prediction of Rate Constants for Aqueous Racemization To Avoid Pointless Stereoselective Syntheses. Angew Chem Int Ed Engl 2017. [DOI: 10.1002/ange.201709163] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
- Andrew Ballard
- Physical Organic Chemistry Centre; School of Chemistry; Cardiff University; Main Building, Park Place, Cardiff CF10 3AT UK
| | - Hiwa O. Ahmad
- Physical Organic Chemistry Centre; School of Chemistry; Cardiff University; Main Building, Park Place, Cardiff CF10 3AT UK
- Pharmaceutical Chemistry Department; College of Pharmacy; Hawler Medical University; Erbil Kurdistan Region Iraq
| | - Stefania Narduolo
- Physical Organic Chemistry Centre; School of Chemistry; Cardiff University; Main Building, Park Place, Cardiff CF10 3AT UK
| | - Lucy Rosa
- AstraZeneca Pharmaceuticals, Mereside; Alderley Park Macclesfield SK10 4TG UK
| | - Nikki Chand
- AstraZeneca Pharmaceuticals, Mereside; Alderley Park Macclesfield SK10 4TG UK
| | - David A. Cosgrove
- AstraZeneca Pharmaceuticals, Mereside; Alderley Park Macclesfield SK10 4TG UK
| | | | - Nabil Asaad
- AstraZeneca Pharmaceuticals, Mereside; Alderley Park Macclesfield SK10 4TG UK
| | - Simone Tomasi
- AstraZeneca; Charter Way, Silk Road Business Park Macclesfield SK10 2NA UK
| | - Niklaas J. Buurma
- Physical Organic Chemistry Centre; School of Chemistry; Cardiff University; Main Building, Park Place, Cardiff CF10 3AT UK
| | - Andrew G. Leach
- School of Pharmacy and Biomolecular Sciences; Liverpool John Moores University; Liverpool L3 3AF UK
| |
Collapse
|
15
|
Saeed HK, Jarman PJ, Archer S, Sreedharan S, Saeed IQ, Mckenzie LK, Weinstein JA, Buurma NJ, Smythe CGW, Thomas JA. Homo‐ and Heteroleptic Phototoxic Dinuclear Metallo‐Intercalators Based on Ru
II
(dppn) Intercalating Moieties: Synthesis, Optical, and Biological Studies. Angew Chem Int Ed Engl 2017. [DOI: 10.1002/ange.201707350] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Affiliation(s)
- Hiwa K. Saeed
- Department of Chemistry University of Sheffield Sheffield S3 7HF UK
| | - Paul J. Jarman
- Department of Chemistry University of Sheffield Sheffield S3 7HF UK
| | - Stuart Archer
- Department of Chemistry University of Sheffield Sheffield S3 7HF UK
| | | | - Ibrahim Q. Saeed
- Physical Organic Chemistry Centre School of Chemistry Cardiff University Main Building, Park Place Cardiff CF10 3AT UK
| | - Luke K. Mckenzie
- Department of Chemistry University of Sheffield Sheffield S3 7HF UK
| | | | - Niklaas J. Buurma
- Physical Organic Chemistry Centre School of Chemistry Cardiff University Main Building, Park Place Cardiff CF10 3AT UK
| | - Carl G. W. Smythe
- Department of Biomedical Science University of Sheffield Sheffield S10 2TN UK
| | - Jim A. Thomas
- Department of Chemistry University of Sheffield Sheffield S3 7HF UK
| |
Collapse
|
16
|
Saeed HK, Jarman PJ, Archer S, Sreedharan S, Saeed IQ, Mckenzie LK, Weinstein JA, Buurma NJ, Smythe CGW, Thomas JA. Homo‐ and Heteroleptic Phototoxic Dinuclear Metallo‐Intercalators Based on Ru
II
(dppn) Intercalating Moieties: Synthesis, Optical, and Biological Studies. Angew Chem Int Ed Engl 2017; 56:12628-12633. [DOI: 10.1002/anie.201707350] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2017] [Indexed: 11/06/2022]
Affiliation(s)
- Hiwa K. Saeed
- Department of Chemistry University of Sheffield Sheffield S3 7HF UK
| | - Paul J. Jarman
- Department of Chemistry University of Sheffield Sheffield S3 7HF UK
| | - Stuart Archer
- Department of Chemistry University of Sheffield Sheffield S3 7HF UK
| | | | - Ibrahim Q. Saeed
- Physical Organic Chemistry Centre School of Chemistry Cardiff University Main Building, Park Place Cardiff CF10 3AT UK
| | - Luke K. Mckenzie
- Department of Chemistry University of Sheffield Sheffield S3 7HF UK
| | | | - Niklaas J. Buurma
- Physical Organic Chemistry Centre School of Chemistry Cardiff University Main Building, Park Place Cardiff CF10 3AT UK
| | - Carl G. W. Smythe
- Department of Biomedical Science University of Sheffield Sheffield S10 2TN UK
| | - Jim A. Thomas
- Department of Chemistry University of Sheffield Sheffield S3 7HF UK
| |
Collapse
|
17
|
Saeed HK, Saeed IQ, Buurma NJ, Thomas JA. Inside Cover: The Structure of Linkers Affects the DNA Binding Properties of Tethered Dinuclear Ruthenium(II) Metallo‐Intercalators (Chem. Eur. J. 23/2017). Chemistry 2017. [DOI: 10.1002/chem.201700460] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
- Hiwa K. Saeed
- Department of Chemistry University of Sheffield Sheffield S3 7HF UK
| | - Ibrahim Q. Saeed
- Physical Organic Chemistry Centre School of Chemistry Cardiff University, Main Building Park Place Cardiff CF10 3AT UK
| | - Niklaas J. Buurma
- Physical Organic Chemistry Centre School of Chemistry Cardiff University, Main Building Park Place Cardiff CF10 3AT UK
| | - Jim A. Thomas
- Department of Chemistry University of Sheffield Sheffield S3 7HF UK
| |
Collapse
|
18
|
Saeed HK, Saeed IQ, Buurma NJ, Thomas JA. The Structure of Linkers Affects the DNA Binding Properties of Tethered Dinuclear Ruthenium(II) Metallo-Intercalators. Chemistry 2017; 23:5467-5477. [PMID: 28072487 DOI: 10.1002/chem.201605750] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2016] [Indexed: 12/12/2022]
Abstract
With the long-term aim of enhancing the binding properties of dinuclear RuII -based DNA light-switch complexes, a series of eight structurally related mono- and dinuclear systems are reported in which the linker of the bridging ligand has been modulated. These tethered systems have been designed to explore issues of steric demand at the binding site and the thermodynamic cost of entropy loss upon binding. Detailed spectroscopic and isothermal titration calorimetry (ITC) studies on the new complexes reveal that one of the linkers produces a dinuclear system that binds to duplex DNA with an affinity (Kb >107 m-1 ) that is higher than its corresponding monometallic complex and is the highest affinity for a non-threading bis-intercalating metal complex. These studies confirm that the tether has a major effect on the binding properties of dinuclear complexes containing intercalating units and establishes key design rules for the construction of dinuclear complexes with enhanced DNA binding characteristics.
Collapse
Affiliation(s)
- Hiwa K Saeed
- Department of Chemistry, University of Sheffield, Sheffield, S3 7HF, UK
| | - Ibrahim Q Saeed
- Physical Organic Chemistry Centre, School of Chemistry, Cardiff University, Main Building Park Place, Cardiff, CF10 3AT, UK
| | - Niklaas J Buurma
- Physical Organic Chemistry Centre, School of Chemistry, Cardiff University, Main Building Park Place, Cardiff, CF10 3AT, UK
| | - Jim A Thomas
- Department of Chemistry, University of Sheffield, Sheffield, S3 7HF, UK
| |
Collapse
|
19
|
Cao T, Zhang FT, Cai LY, Zhou YL, Buurma NJ, Zhang XX. Investigation of the interactions between methylene blue and intramolecular G-quadruplexes: an explicit distinction in electrochemical behavior. Analyst 2017; 142:987-993. [DOI: 10.1039/c7an00083a] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
An explicit difference for binding affinity between MB and different intramolecular G-quadruplexes was quickly and easily obtained by an electrochemical method.
Collapse
Affiliation(s)
- Ting Cao
- Beijing National Laboratory for Molecular Sciences (BNLMS)
- MOE Key Laboratory of Bioorganic Chemistry and Molecular Engineering
- College of Chemistry
- Peking University
- Beijing 100871
| | - Fang-Ting Zhang
- Beijing National Laboratory for Molecular Sciences (BNLMS)
- MOE Key Laboratory of Bioorganic Chemistry and Molecular Engineering
- College of Chemistry
- Peking University
- Beijing 100871
| | - Liang-Yuan Cai
- Beijing National Laboratory for Molecular Sciences (BNLMS)
- MOE Key Laboratory of Bioorganic Chemistry and Molecular Engineering
- College of Chemistry
- Peking University
- Beijing 100871
| | - Ying-Lin Zhou
- Beijing National Laboratory for Molecular Sciences (BNLMS)
- MOE Key Laboratory of Bioorganic Chemistry and Molecular Engineering
- College of Chemistry
- Peking University
- Beijing 100871
| | - Niklaas J. Buurma
- Physical Organic Chemistry Centre
- School of Chemistry
- Cardiff University
- Cardiff
- UK
| | - Xin-Xiang Zhang
- Beijing National Laboratory for Molecular Sciences (BNLMS)
- MOE Key Laboratory of Bioorganic Chemistry and Molecular Engineering
- College of Chemistry
- Peking University
- Beijing 100871
| |
Collapse
|
20
|
Abstract
The interactions of the water-soluble tetraazaperopyrene dye 1 with ct-DNA, duplex-[(dAdT)12 ⋅(dAdT)12 ], duplex-[(dGdC)12 ⋅(dGdC)12 ] as well as with two G-quadruplex-forming sequences, namely the human telomeric 22AG and the promotor sequence c-myc, were investigated by means of UV/visible and fluorescence spectroscopy, isothermal titration calorimetry (ITC) and molecular docking studies. Dye 1 exhibits a high affinity for G-quadruplex structures over duplex DNA structures. Furthermore, the ligand shows promising G-quadruplex discrimination, with an affinity towards c-myc of 2×10(7) m(-1) (i.e., Kd =50 nm), which is higher than for 22AG (4×10(6) m(-1) ). The ITC data reveal that compound 1 interacts with c-myc in a stoichiometric ratio of 1:1 but also indicate the presence of two identical lower affinity secondary binding sites per quadruplex. In 22AG, there are two high affinity binding sites per quadruplex, that is, one on each side, with a further four weaker binding sites. For both quadruplex structures, the high affinity interactions between compound 1 and the quadruplex-forming nucleic acid structures are weakly endothermic. Molecular docking studies suggest an end-stacking binding mode for compound 1 interacting with quadruplex structures, and a higher affinity for the parallel conformation of c-myc than for the mixed-hybrid conformation of 22AG. In addition, docking studies also suggest that the reduced affinity for duplex DNA structures is due to the non-viability of an intercalative binding mode.
Collapse
Affiliation(s)
- Lena Hahn
- Anorganisch-Chemisches-Institut, Universität Heidelberg, Im Neuenheimer Feld 270, 69120, Heidelberg, Germany), Fax
| | - Niklaas J Buurma
- Physical Organic Chemistry Centre, School of Chemistry, Cardiff University, Main Building, Park Place, Cardiff, CF10 3AT, UK), Fax.
| | - Lutz H Gade
- Anorganisch-Chemisches-Institut, Universität Heidelberg, Im Neuenheimer Feld 270, 69120, Heidelberg, Germany), Fax.
| |
Collapse
|
21
|
Zheng G, Kaefer K, Mourdikoudis S, Polavarapu L, Vaz B, Cartmell SE, Bouleghlimat A, Buurma NJ, Yate L, de Lera ÁR, Liz-Marzán LM, Pastoriza-Santos I, Pérez-Juste J. Palladium Nanoparticle-Loaded Cellulose Paper: A Highly Efficient, Robust, and Recyclable Self-Assembled Composite Catalytic System. J Phys Chem Lett 2015; 6:230-238. [PMID: 26263455 DOI: 10.1021/jz5024948] [Citation(s) in RCA: 41] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
We present a novel strategy based on the immobilization of palladium nanoparticles (Pd NPs) on filter paper for development of a catalytic system with high efficiency and recyclability. Oleylamine-capped Pd nanoparticles, dispersed in an organic solvent, strongly adsorb on cellulose filter paper, which shows a great ability to wick fluids due to its microfiber structure. Strong van der Waals forces and hydrophobic interactions between the particles and the substrate lead to nanoparticle immobilization, with no desorption upon further immersion in any solvent. The prepared Pd NP-loaded paper substrates were tested for several model reactions such as the oxidative homocoupling of arylboronic acids, the Suzuki cross-coupling reaction, and nitro-to-amine reduction, and they display efficient catalytic activity and excellent recyclability and reusability. This approach of using NP-loaded paper substrates as reusable catalysts is expected to open doors for new types of catalytic support for practical applications.
Collapse
Affiliation(s)
- Guangchao Zheng
- †Departamento de Química Física, Universidade de Vigo, 36310 Vigo, Spain
| | - Katharina Kaefer
- †Departamento de Química Física, Universidade de Vigo, 36310 Vigo, Spain
| | | | - Lakshminarayana Polavarapu
- ‡Bionanoplasmonics Laboratory, CIC biomaGUNE, Paseo de Miramón 182, 20009 Donostia - San Sebastián, Spain
| | - Belén Vaz
- §Departamento de Química Orgánica, Universidade de Vigo, 36310 Vigo, Spain
| | - Samantha E Cartmell
- ∥Physical Organic Chemistry Centre, School of Chemistry, Cardiff University, Main Building, Park Place, Cardiff, CF10 3AT, United Kingdom
| | - Azzedine Bouleghlimat
- ∥Physical Organic Chemistry Centre, School of Chemistry, Cardiff University, Main Building, Park Place, Cardiff, CF10 3AT, United Kingdom
| | - Niklaas J Buurma
- ∥Physical Organic Chemistry Centre, School of Chemistry, Cardiff University, Main Building, Park Place, Cardiff, CF10 3AT, United Kingdom
| | - Luis Yate
- ‡Bionanoplasmonics Laboratory, CIC biomaGUNE, Paseo de Miramón 182, 20009 Donostia - San Sebastián, Spain
| | - Ángel R de Lera
- §Departamento de Química Orgánica, Universidade de Vigo, 36310 Vigo, Spain
| | - Luis M Liz-Marzán
- †Departamento de Química Física, Universidade de Vigo, 36310 Vigo, Spain
- ‡Bionanoplasmonics Laboratory, CIC biomaGUNE, Paseo de Miramón 182, 20009 Donostia - San Sebastián, Spain
- ⊥Ikerbasque, Basque Foundation for Science, 48011 Bilbao, Spain
| | | | - Jorge Pérez-Juste
- †Departamento de Química Física, Universidade de Vigo, 36310 Vigo, Spain
| |
Collapse
|
22
|
Regan EM, Hallett AJ, Wong LC, Saeed IQ, Langdon-Jones EE, Buurma NJ, Pope SJ, Estrela P. A novel cobalt complex for enhancing amperometric and impedimetric DNA detection. Electrochim Acta 2014. [DOI: 10.1016/j.electacta.2013.10.028] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
|
23
|
Dávila-Ibáñez AB, Buurma NJ, Salgueiriño V. Assessment of DNA complexation onto polyelectrolyte-coated magnetic silica nanoparticles. Nanoscale 2013; 5:4797-4807. [PMID: 23612682 DOI: 10.1039/c3nr34358h] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
The polyelectrolyte-DNA complexation method to form magnetoplexes using silica-coated iron oxide magnetic nanoparticles as inorganic substrates is an attractive and promising process in view of the potential applications including magnetofection, DNA extraction and purification, and directed assembly of nanostructures. Herein, we present a systematic physico-chemical study that provides clear evidence of the type of interactions established, reflects the importance of the DNA length, the nanoparticle size and the ionic strength, and permits the identification of the parameters controlling both the stability and the type of magnetoplexes formed. This information can be used to develop targeted systems with properties optimized for the various proposed applications of magnetoplexes.
Collapse
|
24
|
Salvia MV, Addison F, Alniss HY, Buurma NJ, Khalaf AI, Mackay SP, Anthony NG, Suckling CJ, Evstigneev MP, Santiago AH, Waigh RD, Parkinson JA. Thiazotropsin aggregation and its relationship to molecular recognition in the DNA minor groove. Biophys Chem 2013; 179:1-11. [PMID: 23714424 DOI: 10.1016/j.bpc.2013.04.001] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2013] [Revised: 04/19/2013] [Accepted: 04/19/2013] [Indexed: 11/29/2022]
Abstract
Aggregated states have been alluded to for many DNA minor groove binders but details of the molecule-on-molecule relationship have either been under-reported or ignored. Here we report our findings from ITC and NMR measurements carried out with AIK-18/51, a compound representative of the thiazotropsin class of DNA minor groove binders. The free aqueous form of AIK-18/51 is compared with that found in its complex with cognate DNA duplex d(CGACTAGTCG)2. Molecular self-association of AIK-18/51 is consistent with anti-parallel, face-to-face dimer formation, the building block on which the molecule aggregates. This underlying structure is closely allied to the form found in the ligand's DNA complex. NMR chemical shift and diffusion measurements yield a self-association constant Kass=(61±19)×10(3)M(-1) for AIK-18/51 that fits with a stepwise self-assembly model and is consistent with ITC data. The deconstructed energetics of this assembly process are reported with respect to a design strategy for ligand/DNA recognition.
Collapse
Affiliation(s)
- Marie-Virginie Salvia
- WestCHEM Department of Pure and Applied Chemistry, University of Strathclyde, 295 Cathedral Street, Glasgow G1 1XL, United Kingdom
| | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
25
|
Postolachi R, Danac R, Buurma NJ, Pui A, Balan M, Shova S, Deleanu C. New cycloimmonium ylide ligands and their palladium(ii) affinities. RSC Adv 2013. [DOI: 10.1039/c3ra41911h] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
|
26
|
Saad FA, Buurma NJ, Amoroso AJ, Knight JC, Kariuki BM. Co-ordination behaviour of a novel bisthiourea tripodal ligand: structural, spectroscopic and electrochemical properties of a series of transition metal complexes. Dalton Trans 2012; 41:4608-17. [PMID: 22373815 DOI: 10.1039/c2dt11732k] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
The synthesis of a thiourea substituted derivative of tris(pyridyl-2-methyl)amine (TPA) is reported. Two of the three pyridine rings are substituted in the 6-position with benzoylthiourea groups. These thiourea groups undergo intramolecular hydrogen bonding to form six-membered rings which leaves one N-H group available to form hydrogen bonds with other molecules. This reports details how the complexation of this new ligand with transition metal ions yields complexes with differing geometries. Seven co-ordinate Mn(II) and Cd(II), six co-ordinate Ni(II) and five co-ordinate Co(II), Cu(II) and Zn(II) complexes have been isolated.
Collapse
Affiliation(s)
- Fawaz A Saad
- Cardiff University of Wales-Department of Chemistry, Main Building, Park Place, Cardiff, CF10 3AT, United Kingdom
| | | | | | | | | |
Collapse
|
27
|
Fujii S, Matsuzawa S, Hamasaki H, Nakamura Y, Bouleghlimat A, Buurma NJ. Polypyrrole-palladium nanocomposite coating of micrometer-sized polymer particles toward a recyclable catalyst. Langmuir 2012; 28:2436-2447. [PMID: 22204384 DOI: 10.1021/la204324f] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
A range of near-monodisperse, multimicrometer-sized polymer particles has been coated with ultrathin overlayers of polypyrrole-palladium (PPy-Pd) nanocomposite by chemical oxidative polymerization of pyrrole using PdCl(2) as an oxidant in aqueous media. Good control over the targeted PPy-Pd nanocomposite loading is achieved for 5.2 μm diameter polystyrene (PS) particles, and PS particles of up to 84 μm diameter can also be efficiently coated with the PPy-Pd nanocomposite. The seed polymer particles and resulting composite particles were extensively characterized with respect to particle size and size distribution, morphology, surface/bulk chemical compositions, and conductivity. Laser diffraction studies of dilute aqueous suspensions indicate that the polymer particles disperse stably before and after nanocoating with the PPy-Pd nanocomposite. The Fourier transform infrared (FT-IR) spectrum of the PS particles coated with the PPy-Pd nanocomposite overlayer is dominated by the underlying particle, since this is the major component (>96% by mass). Thermogravimetric and elemental analysis indicated that PPy-Pd nanocomposite loadings were below 6 wt %. The conductivity of pressed pellets prepared with the nanocomposite-coated particles increased with a decrease of particle diameter because of higher PPy-Pd nanocomposite loading. "Flattened ball" morphologies were observed by scanning/transmission electron microscopy after extraction of the PS component from the composite particles, which confirmed a PS core and a PPy-Pd nanocomposite shell morphology. X-ray diffraction confirmed the production of elemental Pd and X-ray photoelectron spectroscopy studies indicated the existence of elemental Pd on the surface of the composite particles. Transmission electron microscopy confirmed that nanometer-sized Pd particles were distributed in the shell. Near-monodisperse poly(methyl methacrylate) particles with diameters ranging between 10 and 19 μm have been also successfully coated with PPy-Pd nanocomposite, and stable aqueous dispersions were obtained. The nanocomposite particles functioned as an efficient catalyst for the aerobic oxidative homocoupling reaction of 4-carboxyphenylboronic acid in aqueous media for the formation of carbon-carbon bonds. The composite particles sediment in a short time (<several tens of minutes) by gravity alone and hence recycling of this catalyst is easy.
Collapse
Affiliation(s)
- Syuji Fujii
- Department of Applied Chemistry, Faculty of Engineering, Osaka Institute of Technology, 5-16-1 Ohmiya, Asahi-ku, Osaka, 535-8585, Japan.
| | | | | | | | | | | |
Collapse
|
28
|
Leach AG, Pilling EA, Rabow AA, Tomasi S, Asaad N, Buurma NJ, Ballard A, Narduolo S. Enantiomeric pairs reveal that key medicinal chemistry parameters vary more than simple physical property based models can explain. Med Chem Commun 2012. [DOI: 10.1039/c2md20010d] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
|
29
|
|
30
|
Affiliation(s)
- Lavinia Onel
- Physical Organic Chemistry Centre, School of Chemistry, Cardiff University, Main Building, Park Place, Cardiff CF10 3AT, United Kingdom
| | - Niklaas J. Buurma
- Physical Organic Chemistry Centre, School of Chemistry, Cardiff University, Main Building, Park Place, Cardiff CF10 3AT, United Kingdom
| |
Collapse
|
31
|
Jones JE, Amoroso AJ, Dorin IM, Parigi G, Ward BD, Buurma NJ, Pope SJA. Bimodal, dimetallic lanthanide complexes that bind to DNA: the nature of binding and its influence on water relaxivity. Chem Commun (Camb) 2011; 47:3374-6. [DOI: 10.1039/c1cc00111f] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
|
32
|
|
33
|
Taladriz-Blanco P, Buurma NJ, Rodríguez-Lorenzo L, Pérez-Juste J, Liz-Marzán LM, Hervés P. Reversible assembly of metal nanoparticles induced by penicillamine. Dynamic formation of SERS hot spots. ACTA ACUST UNITED AC 2011. [DOI: 10.1039/c1jm12175h] [Citation(s) in RCA: 74] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
|
34
|
|
35
|
|
36
|
|
37
|
|
38
|
Buurma NJ, Haq I. Calorimetric and spectroscopic studies of Hoechst 33258: self-association and binding to non-cognate DNA. J Mol Biol 2008; 381:607-21. [PMID: 18617189 DOI: 10.1016/j.jmb.2008.05.073] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2008] [Revised: 05/04/2008] [Accepted: 05/30/2008] [Indexed: 10/22/2022]
Abstract
Sequence and structure-specific molecular recognition of DNA by small molecules is an important goal in biophysical chemistry and drug discovery. Many candidate ligands possess flat aromatic surfaces and other molecular features that allow them to self-associate. In addition, non-specific binding to the target is a complicating feature of these interactions. Therefore, multiple equilibria are present and need to be accounted for in data analysis in order to obtain meaningful thermodynamic parameters. In order to address these issues we have systematically examined the bis-benzimidazole dye Hoechst 33258 (H33258) in terms of self-aggregation and binding to DNA oligonucleotides lacking any cognate minor groove A.T sites. This model system has been interrogated using isothermal titration calorimetry (ITC), circular dichroism (CD), fluorescence spectroscopy and pulsed gradient spin echo NMR. Three distinct binding events and ligand self-aggregation have been identified and, where possible, quantified. H33258 self-aggregation involves a step-wise aggregation mechanism, driven by stacking interactions. The DNA binding process includes two specific binding modes and non-specific DNA-templated H33258 stacking. We have written novel ITC data-fitting software (IC-ITC; freely available to the biophysics community), which simultaneously fits ligand aggregation and ligand-DNA binding. Here, this numerical analysis, which uses simulated annealing of complex calorimetric data representing multiple coupled equilibria, is described.
Collapse
Affiliation(s)
- Niklaas J Buurma
- Centre for Chemical Biology, The Department of Chemistry, The University of Sheffield, Dainton Building, Brook Hill, Sheffield, South Yorkshire, S3 7HF, UK
| | | |
Collapse
|
39
|
Spillane CB, Dabo MN, Fletcher NC, Morgan JL, Keene FR, Haq I, Buurma NJ. The dichotomy in the DNA-binding behaviour of ruthenium(II) complexes bearing benzoxazole and benzothiazole groups. J Inorg Biochem 2008; 102:673-83. [DOI: 10.1016/j.jinorgbio.2007.10.011] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2007] [Revised: 10/06/2007] [Accepted: 10/18/2007] [Indexed: 11/29/2022]
|
40
|
Mullice LA, Laye RH, Harding LP, Buurma NJ, Pope SJA. Rhenium complexes of chromophore-appended dipicolylamine ligands: syntheses, spectroscopic properties, DNA binding and X-ray crystal structure. NEW J CHEM 2008. [DOI: 10.1039/b800999f] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
|
41
|
Buurma NJ, Haq I. Advances in the analysis of isothermal titration calorimetry data for ligand-DNA interactions. Methods 2007; 42:162-72. [PMID: 17472898 DOI: 10.1016/j.ymeth.2007.01.010] [Citation(s) in RCA: 119] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2006] [Revised: 12/20/2006] [Accepted: 01/08/2007] [Indexed: 11/22/2022] Open
Abstract
Isothermal titration calorimetry (ITC) is a well established technique for the study of biological interactions. The strength of ITC is that it directly measures enthalpy changes associated with interactions. Experiments can also yield binding isotherms allowing quantification of equilibrium binding constants, hence an almost complete thermodynamic profile can be established. Principles and application of ITC have been well documented over recent years, experimentally the technique is simple to use and in ideal scenarios data analysis is trivial. However, ITC experiments can be designed such that previously inaccessible parameters can be evaluated. We outline some of these advances, including (1) exploiting different experimental conditions; (2) low affinity systems; (3) high affinity systems and displacement assays. In addition we ask the question: What if data cannot be fit using the fitting functions incorporated in the data-analysis software that came with your ITC? Examples where such data might be generated include systems following non 1:n binding patterns and systems where binding is coupled to other events such as ligand dissociation. Models dealing with such data are now appearing in literature and we summarise examples relevant for the study of ligand-DNA interactions.
Collapse
|
42
|
Shibata T, Buurma NJ, Brazier JA, Thompson P, Haq I, Williams DM. 7,8-Dihydropyrido[2,3-d]pyrimidin-2-one; a bicyclic cytosine analogue capable of enhanced stabilisation of DNA duplexes. Chem Commun (Camb) 2006:3516-8. [PMID: 16921430 DOI: 10.1039/b606058g] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Incorporation of a bicyclic cytosine analogue, 3-beta-D-(2'-deoxyribofuranosyl)-7,8-dihydropyrido[2,3-d]pyrimidine, into synthetic DNA duplexes results in a greatly enhanced thermal stability (3-4 degrees C per modification) compared to the corresponding unmodified duplex.
Collapse
Affiliation(s)
- Takayuki Shibata
- Centre for Chemical Biology, Department of Chemistry, Richard Roberts Building, University of Sheffield, Brook Hill, Sheffield, UK
| | | | | | | | | | | |
Collapse
|
43
|
Li C, Buurma NJ, Haq I, Turner C, Armes SP, Castelletto V, Hamley IW, Lewis AL. Synthesis and characterization of biocompatible, thermoresponsive ABC and ABA triblock copolymer gelators. Langmuir 2005; 21:11026-33. [PMID: 16285767 DOI: 10.1021/la0515672] [Citation(s) in RCA: 103] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/05/2023]
Abstract
The synthesis of doubly thermoresponsive PPO-PMPC-PNIPAM triblock copolymer gelators by atom transfer radical polymerization using a PPO-based macroinitiator is described. Provided that the PPO block is sufficiently long, dynamic light scattering and differential scanning calorimetry studies confirm the presence of two separate thermal transitions corresponding to micellization and gelation, as expected. However, these ABC-type triblock copolymers proved to be rather inefficient gelators: free-standing gels at 37 degrees C required a triblock copolymer concentration of around 20 wt%. This gelator performance should be compared with copolymer concentrations of 6-7 wt% required for the PNIPAM-PMPC-PNIPAM triblock copolymers reported previously. Clearly, the separation of micellar self-assembly from gel network formation does not lead to enhanced gelator efficiencies, at least for this particular system. Nevertheless, there are some features of interest in the present study. In particular, close inspection of the viscosity vs temperature plot obtained for a PPO43-PMPC160-PNIPAM81 triblock copolymer revealed a local minimum in viscosity. This is consistent with intramicelle collapse of the outer PNIPAM blocks prior to the development of the intermicelle hydrophobic interactions that are a prerequisite for macroscopic gelation.
Collapse
Affiliation(s)
- Chengming Li
- Department of Chemistry, Dainton Building, University of Sheffield, Brook Hill, Sheffield, South Yorkshire, S3 7HF, UK
| | | | | | | | | | | | | | | |
Collapse
|
44
|
Abstract
The nature of rate-retarding effects of cationic micelles on the water-catalyzed hydrolyses of a series of para-substituted 1-benzoyl-1,2,4-triazoles (1a-f) and 1-benzoyl-3-phenyl-1,2,4-triazole (2) has been studied using kinetic methods. A comparison is drawn between medium effects in the micellar Stern region and in model solutions for the micellar Stern region. Simple model solutions involving concentrated aqueous solutions of a small ionic molecule resembling the surfactant headgroup, as reported before,(1) were improved. New model solutions for alkyltrimethylammonium bromide micelles contain both tetramethylammonium bromide (TMAB), mimicking micellar headgroups, and 1-propanol, mimicking hydrophobic tails. The rate-retarding effect of micelles on the hydrolysis of 1a-f and 2 is caused by the high concentration of headgroups as well as by hydrophobic tails in the Stern region where 1a-f and 2 bind to the micelle. Individual contributions of these interactions are quantified. Rate-retarding effects found for different probes, with different sensitivities for interactions as they occur when the probe binds to the micellar Stern region, as well as the micellar Stern region's micropolarity as reported by the E(T)(30) probe, are satisfactorily reproduced by new model solutions containing both TMAB and 1-propanol.
Collapse
Affiliation(s)
- Niklaas J Buurma
- Physical Organic Chemistry Unit, Stratingh Institute, University of Groningen, Nijenborgh 4, 9747 AG Groningen, The Netherlands
| | | | | | | |
Collapse
|
45
|
Blandamer MJ, Buurma NJ, Engberts JB, Reis JC. Kinetics of hydrolysis of 1-benzoyl-1,2,4-triazole in aqueous solution as a function of temperature near the temperature of maximum density, and the isochoric controversy. Org Biomol Chem 2003; 1:720-3. [PMID: 12929460 DOI: 10.1039/b210246c] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
At temperatures above and below the temperature of maximum density, TMD, for water at ambient pressure, pairs of temperatures exist at which the molar volumes of water are equal. First-order rate constants for the pH-independent hydrolysis of 1-benzoyl-1,2,4-triazole in aqueous solution at pairs of such isochoric temperatures show no unique features. Taken together with previously published kinetic data for the hydrolysis of a range of simple organic solutes in both water and D2O near their respective TMDs, we conclude that special significance in the context of rates of chemical reactions in aqueous solutions should not be attached to the isochoric condition.
Collapse
|
46
|
Buurma NJ, Blandamer MJ, Engberts JBFN. General-base catalysed hydrolysis and nucleophilic substitution of activated amides in aqueous solutions. J PHYS ORG CHEM 2003. [DOI: 10.1002/poc.607] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
|
47
|
Buurma NJ, Pastorello L, Blandamer MJ, Engberts JB. Kinetic evidence for hydrophobically stabilized encounter complexes formed by hydrophobic esters in aqueous solutions containing monohydric alcohols. J Am Chem Soc 2001; 123:11848-53. [PMID: 11724590 DOI: 10.1021/ja010617w] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The pH-independent hydrolysis of four esters, p-methoxyphenyl 2,2-dichloroethanoate (1a), p-methoxyphenyl 2,2-dichloropropanoate (1b), p-methoxyphenyl 2,2-dichlorobutanoate (1c), and p-methoxyphenyl 2,2-dichloropentanoate (1d), in dilute aqueous solution has been studied as a function of the molality of added cosolutes ethanol, 1-propanol, and 1-butanol. The rate constants for the neutral hydrolysis decrease with increasing cosolute concentration. These kinetic medium effects respond to both the hydrophobicity of the ester and of the monohydric alcohol. The observed rate effects were analyzed using both a thermodynamic and a kinetic model. The kinetic model suggests a molecular picture of a hydrophobically stabilized encounter complex, with equilibrium constants K(ec) often smaller than unity, in which the cosolute blocks the reaction center of the hydrolytic ester for attack by water. The formation of these encounter complexes leads to a dominant initial-state stabilization as follows from the thermodynamic model. Decreases in both apparent enthalpies and entropies of activation for these hydrolysis reactions correspond to unfavorable enthalpies and favorable entropies of complexation, which confirms that the encounter complexes are stabilized by hydrophobic interactions.
Collapse
Affiliation(s)
- N J Buurma
- Physical Organic Chemistry Unit, Stratingh Institute, University of Groningen, Nijenborgh 4, 9747 AG Groningen, The Netherlands
| | | | | | | |
Collapse
|
48
|
|