1
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Pike SJ, Telford R, Male L. Reversible conformational switching of a photo-responsive ortho-azobenzene/2,6-pyridyldicarboxamide heterofoldamer. Org Biomol Chem 2023; 21:7717-7723. [PMID: 37565617 DOI: 10.1039/d3ob01137b] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 08/12/2023]
Abstract
We report on a convenient synthetic route to rapidly access a new photo-responsive ortho-azobenzene/2,6-pyridyldicarboxamide heterofoldamer. The adoption of a stable helical conformation has been established for this scaffold in both the solid state and in solution using single crystal X-ray diffraction and circular dichroism (CD) spectroscopy respectively. Reversible control over the stimuli-driven structural re-ordering of the supramolecular scaffold, from a stable helical conformation under non-irradiative conditions, to a less well-ordered state under irradiative conditions, has been identified. The robust nature of the responsive, conformational, molecular switching behaviour has been determined using UV/Vis, 1H NMR and CD spectroscopy. Minimal loss in the efficiency of the stimuli-driven, structural re-ordering processes of the foldamer scaffold is observed, even upon multiple cyclic treatments with irradiative/non-irradiative conditions.
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Affiliation(s)
- Sarah J Pike
- School of Chemistry, University of Birmingham, Edgbaston, Birmingham, B15 2TT, UK.
- School of Chemistry and Biosciences, Faculty of Life Sciences, University of Bradford, Bradford, West Yorkshire, BD7 1DP, UK
| | - Richard Telford
- School of Chemistry and Biosciences, Faculty of Life Sciences, University of Bradford, Bradford, West Yorkshire, BD7 1DP, UK
| | - Louise Male
- School of Chemistry, University of Birmingham, Edgbaston, Birmingham, B15 2TT, UK.
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2
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Delfosse P, Seaton CC, Male L, Lord RM, Pike SJ. Influence of Terminal Functionality on the Crystal Packing Behaviour and Cytotoxicity of Aromatic Oligoamides. Front Chem 2021; 9:709161. [PMID: 34277574 PMCID: PMC8277928 DOI: 10.3389/fchem.2021.709161] [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] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2021] [Accepted: 06/10/2021] [Indexed: 11/13/2022] Open
Abstract
The synthesis and characterization of three aromatic oligoamides, constructed from the same pyridyl carboxamide core but incorporating distinct end groups of acetyl (Ac) 1, tert-butyloxycarbonyl (Boc) 2 and amine 3 is reported. Single crystal X-ray diffraction analysis of 1-3 and a dimethylsulfoxide (DMSO) solvate of 2 (2-DMSO), has identified the presence of a range of intra- and intermolecular interactions including N-H⋯N, N-H⋯O=C and N-H⋯O=S(CH3)2 hydrogen-bonding interactions, C-H⋯π interactions and off-set, face-to-face stacking π-π interactions that support the variety of slipped stack, herringbone and cofacial crystal packing arrangements observed in 1-3. Additionally, the cytotoxicity of this series of aromatic oligoamides was assessed against two human ovarian (A2780 and A2780cisR), two human breast (MCF-7 and MDA-MB-231) cancerous cell lines and one non-malignant human epithelial cell line (PNT-2), to investigate the influence of the terminal functionality of these aromatic oligoamides on their biological activity. The chemosensitivity results highlight that modification of the terminal group from Ac to Boc in 1 and 2 leads to a 3-fold increase in antiproliferative activity against the cisplatin-sensitive ovarian carcinoma cell line, A2780. The presence of the amine termini in 3 gave the only member of the series to display activity against the cisplatin-resistance ovarian carcinoma cell line, A2780cisR. Compound 2 is the lead candidate of this series, displaying high selectivity towards A2780 cancer cells when compared to non-malignant PNT-2 cells, with a selectivity index value >4.2. Importantly, this compound is more selective towards A2780 (cf. PNT-2) than the clinical platinum drugs oxaliplatin by > 2.6-fold and carboplatin by > 1.6-fold.
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Affiliation(s)
- Pierre Delfosse
- School of Chemistry and Biosciences, University of Bradford, Bradford, United Kingdom
| | - Colin C. Seaton
- School of Chemistry and Biosciences, University of Bradford, Bradford, United Kingdom
| | - Louise Male
- School of Chemistry, University of Birmingham, Birmingham, United Kingdom
| | - Rianne M. Lord
- School of Chemistry and Biosciences, University of Bradford, Bradford, United Kingdom
- School of Chemistry, University of East Anglia, Norwich Research Park, Norwich, United Kingdom
| | - Sarah J. Pike
- School of Chemistry and Biosciences, University of Bradford, Bradford, United Kingdom
- School of Chemistry, University of Birmingham, Birmingham, United Kingdom
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3
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Abstract
A series of cyclometallated mono- and di-nuclear platinum(II) complexes and the parent organic ligand, 2,6-diphenylpyridine 1 (HC^N^CH), have been synthesized and characterized. This library of compounds includes [(C^N^C)PtII (L)] (L=dimethylsulfoxide (DMSO) 2 and triphenylphosphine (PPh3 ) 3) and [((C^N^C)PtII )2 (L')] (where L'=N-heterocycles (pyrazine (pyr) 4, 4,4'-bipyridine (4,4'-bipy) 5 or diphosphine (1,4-bis(diphenylphosphino)butane (dppb) 6). Their cytotoxicity was assessed against four cancerous cell lines and one normal cell line, with results highlighting significantly increased antiproliferative activity for the dinuclear complexes (4-6), when compared to the mononucleated species (2 and 3). Complex 6 is the most promising candidate, displaying very high selectivity towards cancerous cells, with selectivity index (SI) values >29.5 (A2780) and >11.2 (A2780cisR), and outperforming cisplatin by >4-fold and >18-fold, respectively.
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Affiliation(s)
- Angélique Kergreis
- School of Chemistry and BiosciencesFaculty of Life SciencesUniversity of BradfordBradford, West YorkshireBD7 1DPUK
| | - Rianne M. Lord
- School of Chemistry and BiosciencesFaculty of Life SciencesUniversity of BradfordBradford, West YorkshireBD7 1DPUK
- School of ChemistryUniversity of East AngliaNorwich Research ParkNorwichNR4 7TJUK
| | - Sarah J. Pike
- School of Chemistry and BiosciencesFaculty of Life SciencesUniversity of BradfordBradford, West YorkshireBD7 1DPUK
- School of ChemistryUniversity of BirminghamEdgbastonBirminghamB15 2TTUK
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4
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Abstract
The solid state behaviour of a short series aromaticC-nitroso compounds has been studied as a function of the electronic and steric nature of theortho-substituent on the ring.
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Affiliation(s)
- Sarah J. Pike
- School of Chemistry
- University of Birmingham
- Birmingham
- UK
- School of Chemistry and Biosciences
| | - Armelle Heliot
- School of Chemistry and Biosciences
- Faculty of Life Sciences
- University of Bradford
- Bradford
- UK
| | - Colin C. Seaton
- School of Chemistry and Biosciences
- Faculty of Life Sciences
- University of Bradford
- Bradford
- UK
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5
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Pike SJ, Hunter CA, Brammer L, Perutz RN. Benchmarking of Halogen Bond Strength in Solution with Nickel Fluorides: Bromine versus Iodine and Perfluoroaryl versus Perfluoroalkyl Donors. Chemistry 2019; 25:9237-9241. [PMID: 30985028 PMCID: PMC6771525 DOI: 10.1002/chem.201900924] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2019] [Indexed: 12/18/2022]
Abstract
The energetics of halogen bond formation in solution have been investigated for a series of nickel fluoride halogen bond acceptors; trans-[NiF(2-C5 NF4 )(PEt3 )2 ] (A1), trans-[NiF{2-C5 NF3 (4-H)}(PEt3 )2 ] (A2), trans-[NiF{2-C5 NF3 (4-NMe2 )}(PEt3 )2 ] (A3) and trans-[NiF{2-C5 NF2 H(4-CF3 )}(PCy3 )2 ] (A4) with neutral organic halogen bond donors, iodopentafluorobenzene (D1), 1-iodononafluorobutane (D2) and bromopentafluorobenzene (D3), in order to establish the significance of changes from perfluoroaryl to perfluoroalkyl donors and from iodine to bromine donors. 19 F NMR titration experiments have been employed to obtain the association constants, enthalpy, and entropy for the halogen bond formed between these donor-acceptor partners in protiotoluene. For A2-A4, association constants of the halogen bonds formed with iodoperfluoroalkane (D2) are consistently larger than those obtained for analogous complexes with the iodoperfluoroarene (D1). For complexes formed with A2-A4, the strength of the halogen bond is significantly lowered upon modification of the halogen donor atom from I (in D1) to Br (in D3) (for D1: 5≤K285 ≤12 m-1 , for D3: 1.0≤K193 ≤1.6 m-1 ). The presence of the electron donating NMe2 substituent on the pyridyl ring of acceptor A3 led to an increase in -ΔH, and the association constants of the halogen bond complexes formed with D1-D3, compared to those formed by A1, A2 and A4 with the same donors.
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Affiliation(s)
- Sarah J. Pike
- Department of ChemistryUniversity of York, HeslingtonYorkYO10 5DDUK
| | | | - Lee Brammer
- Department of ChemistryUniversity of Sheffield, Brook HillSheffieldS3 7HFUK
| | - Robin N. Perutz
- Department of ChemistryUniversity of York, HeslingtonYorkYO10 5DDUK
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6
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Abstract
UV/Vis absorption and NMR spectroscopy titrations have been used to investigate the formation of complexes between cations and neutral H-bond acceptors in organic solvents. Complexes formed by two different H-bond acceptors with fifteen different cations were studied in acetone and in acetonitrile. The effects of water and ion pairing with the counter-anion were found to be negligible in the two polar solvents employed for this study. The data were used to determine self-consistent H-bond donor parameters (α) for a series of organic and inorganic cations; guanidinium, primary, tertiary and quaternary ammonium, imidazolium, methylpyridinium, lithium, sodium, potassium, rubidium and caesium. The results demonstrate the transferability of α parameters for cations between different solvents and different H-bond acceptor partners, allowing reliable prediction of cation recognition properties in different environments. Lithium and protonated nitrogen cations form the most stable complexes, but the α parameter is only 5.0, which is similar to the neutral H-bond donor 3-trifluoromethyl,4-nitrophenol (α = 5.1). Quaternary ammonium is the weakest H-bond donor investigated with an α value of 2.7, which is comparable to an alcohol. The α parameters for alkali metal cations decrease down the group from 5.0 (Li+) to 3.5 (Cs+).
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Affiliation(s)
- Sarah J Pike
- Department of Chemistry , University of Cambridge , Lensfield Road , Cambridge , CB2 1EW , UK .
| | - Ennio Lavagnini
- Department of Chemistry , University of Cambridge , Lensfield Road , Cambridge , CB2 1EW , UK .
| | - Lisa M Varley
- Department of Chemistry , University of Sheffield , Sheffield , S3 7HF , UK
| | - Joanne L Cook
- Unilever R&D Port Sunlight , Quarry Road East , Bebington , Wirral CH63 3JW , UK
| | - Christopher A Hunter
- Department of Chemistry , University of Cambridge , Lensfield Road , Cambridge , CB2 1EW , UK .
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7
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Lister FGA, Eccles N, Pike SJ, Brown RA, Whitehead GFS, Raftery J, Webb SJ, Clayden J. Bis-pyrene probes of foldamer conformation in solution and in phospholipid bilayers. Chem Sci 2018; 9:6860-6870. [PMID: 30310619 PMCID: PMC6114994 DOI: 10.1039/c8sc02532k] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [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: 06/08/2018] [Accepted: 07/16/2018] [Indexed: 11/21/2022] Open
Abstract
Exploring the detailed structural features of synthetic molecules in the membrane phase requires sensitive probes of conformation. Here we describe the design, synthesis and characterization of bis(pyrene) probes that report conformational changes in membrane-active dynamic foldamers. The probes were designed to distinguish between left-handed (M) and right-handed (P) screw-sense conformers of 310-helical α-aminoisobutyric acid (Aib) peptide foldamers, both in solution and in bilayer membranes. Several different bis(pyrene) probes were synthesized and ligated to the C-terminus of Aib tetramers that had different chiral residues at the N-terminus, residues that favored either an M or a P screw-sense in the 310-helix. The readily synthesized and conveniently incorporated N-acetyl-1,2-bis(pyren-1'-yl)ethylenediamine probe proved to have the best properties. In solution, changes in foldamer screw-sense induced substantial changes in the ratio of excimer/monomer fluorescence emission (E/M) for this reporter of conformation, with X-ray crystallography revealing that opposite screw-senses produce very different interpyrene distances in the reporter. In bilayers, this convenient and sensitive fluorescent reporter allowed, for the first time, an investigation of how the chirality of natural phospholipids affects foldamer conformation.
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Affiliation(s)
- Francis G A Lister
- School of Chemistry , University of Manchester , Oxford Road , Manchester M13 9PL , UK .
| | - Natasha Eccles
- School of Chemistry , University of Manchester , Oxford Road , Manchester M13 9PL , UK . .,Manchester Institute of Biotechnology , University of Manchester , 131 Princess St , Manchester M1 7DN , UK
| | - Sarah J Pike
- School of Chemistry , University of Manchester , Oxford Road , Manchester M13 9PL , UK . .,Manchester Institute of Biotechnology , University of Manchester , 131 Princess St , Manchester M1 7DN , UK.,Faculty of Life Sciences , University of Bradford , Bradford , West Yorkshire BD7 1DP , UK
| | - Robert A Brown
- School of Chemistry , University of Manchester , Oxford Road , Manchester M13 9PL , UK .
| | - George F S Whitehead
- School of Chemistry , University of Manchester , Oxford Road , Manchester M13 9PL , UK .
| | - James Raftery
- School of Chemistry , University of Manchester , Oxford Road , Manchester M13 9PL , UK .
| | - Simon J Webb
- School of Chemistry , University of Manchester , Oxford Road , Manchester M13 9PL , UK . .,Manchester Institute of Biotechnology , University of Manchester , 131 Princess St , Manchester M1 7DN , UK
| | - Jonathan Clayden
- School of Chemistry , University of Bristol , Cantock's Close , Bristol BS8 1TS , UK .
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8
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Lizio MG, Andrushchenko V, Pike SJ, Peters AD, Whitehead GFS, Vitórica-Yrezábal IJ, Mutter ST, Clayden J, Bouř P, Blanch EW, Webb SJ. Optically Active Vibrational Spectroscopy of α-Aminoisobutyric Acid Foldamers in Organic Solvents and Phospholipid Bilayers. Chemistry 2018; 24:9399-9408. [PMID: 29745985 DOI: 10.1002/chem.201801121] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [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: 03/05/2018] [Indexed: 12/12/2022]
Abstract
Helical α-aminoisobutyric acid (Aib) foldamers show great potential as devices for the communication of conformational information across phospholipid bilayers, but determining their conformation in bilayers remains a challenge. In the present study, Raman, Raman optical activity (ROA), infrared (IR) and vibrational circular dichroism (VCD) spectroscopies have been used to analyze the conformational preferences of Aib foldamers in solution and when interacting with bilayers. A 310 -helix marker band at 1665-1668 cm-1 in Raman spectra was used to show that net helical content increased strongly with oligomer length. ROA and VCD spectra of chiral Aib foldamers provided the chiroptical signature for both left- and right-handed 310 -helices in organic solvents, with VCD establishing that foldamer screw-sense was preserved when the foldamers became embedded within bilayers. However, the population distribution between different secondary structures was perturbed by the chiral phospholipid. These studies indicate that ROA and VCD spectroscopies are valuable tools for the study of biomimetic structures, such as artificial signal transduction molecules, in phospholipid bilayers.
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Affiliation(s)
- Maria Giovanna Lizio
- Manchester Institute of Biotechnology, University of Manchester, 131 Princess St, Manchester, M1 7DN, UK.,School of Chemistry, University of Manchester, Oxford Road, Manchester, M13 9PL, UK
| | - Valery Andrushchenko
- Institute of Organic Chemistry and Biochemistry, Academy of Sciences, Flemingovo náměstí 2, 16610, Prague 6, Czech Republic
| | - Sarah J Pike
- Manchester Institute of Biotechnology, University of Manchester, 131 Princess St, Manchester, M1 7DN, UK.,School of Chemistry, University of Manchester, Oxford Road, Manchester, M13 9PL, UK.,Faculty of Life Sciences, University of Bradford, Bradford, West Yorkshire, BD7 1DP, UK
| | - Anna D Peters
- Manchester Institute of Biotechnology, University of Manchester, 131 Princess St, Manchester, M1 7DN, UK.,School of Chemistry, University of Manchester, Oxford Road, Manchester, M13 9PL, UK
| | - George F S Whitehead
- School of Chemistry, University of Manchester, Oxford Road, Manchester, M13 9PL, UK
| | | | - Shaun T Mutter
- Manchester Institute of Biotechnology, University of Manchester, 131 Princess St, Manchester, M1 7DN, UK
| | - Jonathan Clayden
- School of Chemistry, University of Bristol, Cantock's Close, Bristol, BS8 1TS, UK
| | - Petr Bouř
- Institute of Organic Chemistry and Biochemistry, Academy of Sciences, Flemingovo náměstí 2, 16610, Prague 6, Czech Republic
| | - Ewan W Blanch
- School of Science, RMIT University, GPO Box 2476, Melbourne, Victoria, 3001, Australia
| | - Simon J Webb
- Manchester Institute of Biotechnology, University of Manchester, 131 Princess St, Manchester, M1 7DN, UK.,School of Chemistry, University of Manchester, Oxford Road, Manchester, M13 9PL, UK
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9
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Thangavadivale V, Aguiar PM, Jasim NA, Pike SJ, Smith DA, Whitwood AC, Brammer L, Perutz RN. Self-complementary nickel halides enable multifaceted comparisons of intermolecular halogen bonds: fluoride ligands vs. other halides. Chem Sci 2018; 9:3767-3781. [PMID: 29780509 PMCID: PMC5939608 DOI: 10.1039/c8sc00890f] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [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: 02/23/2018] [Accepted: 03/19/2018] [Indexed: 11/21/2022] Open
Abstract
Studies of X–Ni–C6F4I···X–Ni–C6F4I halogen-bonded networks reveal pronounced differences between fluoride (X = F) and other halides: the 19F-MAS NMR spectrum is a sensitive probe of the halogen bond.
The syntheses of three series of complexes designed with self-complementary motifs for formation of halogen bonds between an iodotetrafluorophenyl ligand and a halide ligand at square-planar nickel are reported, allowing structural comparisons of halogen bonding between all four halides C6F4I···X–Ni (X = F, Cl, Br, I). In the series trans-[NiX(2,3,5,6-C6F4I)(PEt3)2] 1pX and trans-[NiX(2,3,4,5-C6F4I)(PEt3)2] (X = F, Cl, Br, I) 1oX, the iodine substituent on the benzene ring was positioned para and ortho to the metal, respectively. The phosphine substituents were varied in the series, trans-[NiX(2,3,5,6-C6F4I)(PEt2Ph)2] (X = F, I) 2pX. Crystal structures were obtained for the complete series 1pX, and for 1oF, 1oCl, 1oI and 2pI. All these complexes exhibited halogen bonds in the solid state, of which 1pF exhibited unique characteristics with a linear chain, the shortest halogen bond d(C6F4I···F–Ni) = 2.655(5) Å and the greatest reduction in halogen bond distance (I···F) compared to the sum of the Bondi van der Waals radii, 23%. The remaining complexes form zig-zag chains of halogen bonds with distances also reduced with respect to the sum of the van der Waals radii. The magnitude of the reductions follow the pattern F > Cl ∼ Br > I, 1pX > 1oX, consistent with the halogen bond strength following the same order. The variation in the I···X–Ni angles is consistent with the anisotropic charge distribution of the halide ligand. The temperature dependence of the X-ray structure of 1pF revealed a reduction in halogen bond distance of 0.055(7) Å on cooling from 240 to 111 K. Comparison of three polymorphs of 1oI shows that the halogen bond geometry may be altered significantly by the crystalline environment. The effect of the halogen bond on the 19F NMR chemical shift in the solid state is demonstrated by comparison of the magic-angle spinning NMR spectra of 1pF and 1oF with that of a complex incapable of halogen bond formation, trans-[NiF(C6F5)(PEt3)2] 3F. Halogen bonding causes deshielding of δiso in the component of the tensor perpendicular to the nickel coordination plane. The results demonstrate the potential of fluoride ligands for formation of halogen bonds in supramolecular structures.
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Affiliation(s)
| | - Pedro M Aguiar
- Department of Chemistry , University of York , York YO10 5DD , UK . ; .,Département de Chimie , l'Université de Montréal , Montréal , QC H3C 3J7 , Canada
| | - Naseralla A Jasim
- Department of Chemistry , University of York , York YO10 5DD , UK . ;
| | - Sarah J Pike
- Department of Chemistry , University of York , York YO10 5DD , UK . ;
| | - Dan A Smith
- Department of Chemistry , University of York , York YO10 5DD , UK . ;
| | - Adrian C Whitwood
- Department of Chemistry , University of York , York YO10 5DD , UK . ;
| | - Lee Brammer
- Department of Chemistry , University of Sheffield , Sheffield S3 7HF , UK .
| | - Robin N Perutz
- Department of Chemistry , University of York , York YO10 5DD , UK . ;
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10
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Abstract
Six different crystal structures are obtained depending on the crystallization solvent.
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Affiliation(s)
- Sarah J. Pike
- Department of Chemistry
- University of Cambridge
- Cambridge
- UK
| | - Andrew D. Bond
- Department of Chemistry
- University of Cambridge
- Cambridge
- UK
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11
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Abstract
UV/vis absorption titrations have been used to investigate the formation of H-bonded complexes between anionic H-bond acceptors (HBAs) and neutral H-bond donors (HBDs) in organic solvents. Complexes formed by three different HBDs with 15 different anions were studied in chloroform and in acetonitrile. The data were used to determine self-consistent HBA parameters (β) for chloride, bromide, iodide, phosphate diester, acetate, benzoate, perrhenate, nitrate, triflimide, perchlorate, hexafluorophosphate, hydrogen sulfate, methyl sulfonate, triflate, and perfluorobutyl sulfonate. The results demonstrate the transferability of H-bond parameters for anions between different solvents and different HBD partners, allowing reliable prediction of anion recognition properties in other scenarios. Carboxylates are the strongest HBAs studied, with β parameters (≈ 15) that are significantly higher than those of neutral organic HBAs, and the non-coordinating anion hexafluorophosphate is the weakest acceptor, with a β parameter comparable to that of pyridine. The effects of ion pairing with the counter-cation were found to be negligible, provided small polar cations were avoided in the less polar solvent (chloroform). There is no correlation between the H-bonding properties of the anions and the pKa values of the conjugate acids.
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Affiliation(s)
- Sarah J Pike
- Department of Chemistry, University of Cambridge , Lensfield Road, Cambridge CB2 1EW, U.K
| | | | - Christopher A Hunter
- Department of Chemistry, University of Cambridge , Lensfield Road, Cambridge CB2 1EW, U.K
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12
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Abstract
We report on the development of a dual molecular recognition probe for hydrogen bond acceptors.
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Affiliation(s)
- Sarah J. Pike
- Department of Chemistry
- University of Cambridge
- Cambridge
- UK
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13
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Pike SJ, Jones JE, Raftery J, Clayden J, Webb SJ. Helical peptaibol mimics are better ionophores when racemic than when enantiopure. Org Biomol Chem 2016; 13:9580-4. [PMID: 26327434 DOI: 10.1039/c5ob01652e] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Helical peptide foldamers rich in α-aminoisobutyric acid (Aib) act as peptaibol-mimicking ionophores in the phospholipid bilayers of artificial vesicles. Racemic samples of these foldamers are more active than their enantiopure counterparts, which was attributed to differing propensities to form aggregates with crystal-like features in the bilayer.
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Affiliation(s)
- Sarah J Pike
- School of Chemistry, University of Manchester, Oxford Road, Manchester, M13 9PL, UK.
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14
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Pike SJ, Raftery J, Webb SJ, Clayden J. Conformational analysis of helical aminoisobutyric acid (Aib) oligomers bearing C-terminal ester Schellman motifs. Org Biomol Chem 2016; 12:4124-31. [PMID: 24831537 DOI: 10.1039/c4ob00268g] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [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
The effect of Schellman motifs on the adoption of stable 310 helical conformations in a series of aminoisobutyric (Aib) oligomers has been studied in the solid state and solution. The destabilising effect of the Schellman motif (a local inversion of helical screw-sense due to a C-terminal ester residue) was quantified in the solid state using X-ray crystallography through analysis of the torsion angles and their deviation from those observed in an ideal 310 helix. Investigation of the intramolecular hydrogen-bonding interactions in the solid state led to the identification of a fully extended C5 conformation in one oligomer, which is a novel folding motif for Aib oligomers. The effect of ester groups with differing steric demands on intermolecular hydrogen-bonding contacts in the solid state was also ascertained. In solution, the adoption of a 310 conformation in Aib oligomers appeared to be more finely tuned, depending on a number of factors, including chain length and the steric demands of the C-terminal destabilising Schellman motif.
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Affiliation(s)
- Sarah J Pike
- School of Chemistry, University of Manchester, Oxford Road, Manchester, M13 9PL, UK.
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15
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Pike SJ, Boddaert T, Raftery J, Webb SJ, Clayden J. Participation of non-aminoisobutyric acid (Aib) residues in the 310 helical conformation of Aib-rich foldamers: a solid state study. NEW J CHEM 2015. [DOI: 10.1039/c4nj01547a] [Citation(s) in RCA: 13] [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
310 helical conformations that extend over 21 Å result when selected non-Aib terminal and central residues are incorporated into Aib-rich foldamers.
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Affiliation(s)
- Sarah J. Pike
- School of Chemistry
- University of Manchester
- Manchester
- UK
| | | | - James Raftery
- School of Chemistry
- University of Manchester
- Manchester
- UK
| | - Simon J. Webb
- School of Chemistry
- University of Manchester
- Manchester
- UK
- Manchester Institute of Biotechnology
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16
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Pike SJ, Diemer V, Raftery J, Webb SJ, Clayden J. Designing foldamer-foldamer interactions in solution: the roles of helix length and terminus functionality in promoting the self-association of aminoisobutyric acid oligomers. Chemistry 2014; 20:15981-90. [PMID: 25280242 DOI: 10.1002/chem.201403626] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [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: 05/21/2014] [Indexed: 12/11/2022]
Abstract
The biological activity of antibiotic peptaibols has been linked to their ability to aggregate, but the structure-activity relationship for aggregation is not well understood. Herein, we report a systematic study of a class of synthetic helical oligomer (foldamer) composed of aminoisobutyric acid (Aib) residues, which mimic the folding behavior of peptaibols. NMR spectroscopic analysis was used to quantify the dimerization constants in solution, which showed hydrogen-bond donors at the N terminus promoted aggregation more effectively than similar modifications at the C terminus. Elongation of the peptide chain also favored aggregation. The geometry of aggregation in solution was investigated by means of titrations with [D6]DMSO and 2D NOE NMR spectroscopy, which allowed the NH protons most involved in intermolecular hydrogen bonds in solution to be identified. X-ray crystallography studies of two oligomers allowed a comparison of the inter- and intramolecular hydrogen-bonding interactions in the solid state and in solution and gave further insight into the geometry of foldamer-foldamer interactions. These solution-based and solid-state studies indicated that the preferred geometry for aggregation is through head-to-tail interactions between the N and C termini of adjacent Aib oligomers.
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Affiliation(s)
- Sarah J Pike
- School of Chemistry, University of Manchester, Oxford Road, Manchester, M13 9PL (UK), Fax: (+44) 161-275-4939
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Pike SJ, De Poli M, Zawodny W, Raftery J, Webb SJ, Clayden J. Diastereotopic fluorine substituents as 19F NMR probes of screw-sense preference in helical foldamers. Org Biomol Chem 2013; 11:3168-76. [DOI: 10.1039/c3ob40463c] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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Sooksawat D, Pike SJ, Slawin AMZ, Lusby PJ. Acid–base responsive switching between “3+1” and “2+2” platinum complexes. Chem Commun (Camb) 2013; 49:11077-9. [DOI: 10.1039/c3cc46587j] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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Ujma J, De Cecco M, Chepelin O, Levene H, Moffat C, Pike SJ, Lusby PJ, Barran PE. Shapes of supramolecular cages by ion mobility mass spectrometry. Chem Commun (Camb) 2012; 48:4423-4425. [DOI: 10.1039/c2cc30778b] [Citation(s) in RCA: 55] [Impact Index Per Article: 4.6] [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
Ion mobility mass spectrometry distinguishes between isobaric supramolecular complexes, revealing subtle structural differences and their effect on the stability of self assembled architectures.
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Affiliation(s)
- Jakub Ujma
- EastChem
- School of Chemistry
- University of Edinburgh
- Edinburgh EH9 3JJ
| | - Martin De Cecco
- EastChem
- School of Chemistry
- University of Edinburgh
- Edinburgh EH9 3JJ
| | - Oleg Chepelin
- EastChem
- School of Chemistry
- University of Edinburgh
- Edinburgh EH9 3JJ
| | - Hannah Levene
- EastChem
- School of Chemistry
- University of Edinburgh
- Edinburgh EH9 3JJ
| | - Chris Moffat
- EastChem
- School of Chemistry
- University of Edinburgh
- Edinburgh EH9 3JJ
| | - Sarah J. Pike
- EastChem
- School of Chemistry
- University of Edinburgh
- Edinburgh EH9 3JJ
| | - Paul J. Lusby
- EastChem
- School of Chemistry
- University of Edinburgh
- Edinburgh EH9 3JJ
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Lusby PJ, Müller P, Pike SJ, Slawin AMZ. Stimuli-Responsive Reversible Assembly of 2D and 3D Metallosupramolecular Architectures. J Am Chem Soc 2009; 131:16398-400. [DOI: 10.1021/ja907297z] [Citation(s) in RCA: 86] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Paul J. Lusby
- School of Chemistry, University of Edinburgh, Joseph Black Building, West Mains Road, Edinburgh EH9 3JJ, U.K., and School of Chemistry, University of St. Andrews, Purdie Building, St. Andrews, Fife KY16 9ST, U.K
| | - Peter Müller
- School of Chemistry, University of Edinburgh, Joseph Black Building, West Mains Road, Edinburgh EH9 3JJ, U.K., and School of Chemistry, University of St. Andrews, Purdie Building, St. Andrews, Fife KY16 9ST, U.K
| | - Sarah J. Pike
- School of Chemistry, University of Edinburgh, Joseph Black Building, West Mains Road, Edinburgh EH9 3JJ, U.K., and School of Chemistry, University of St. Andrews, Purdie Building, St. Andrews, Fife KY16 9ST, U.K
| | - Alexandra M. Z. Slawin
- School of Chemistry, University of Edinburgh, Joseph Black Building, West Mains Road, Edinburgh EH9 3JJ, U.K., and School of Chemistry, University of St. Andrews, Purdie Building, St. Andrews, Fife KY16 9ST, U.K
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Joyce CA, Zorich B, Pike SJ, Barber JC, Dennis NR. Williams-Beuren syndrome: phenotypic variability and deletions of chromosomes 7, 11, and 22 in a series of 52 patients. J Med Genet 1996; 33:986-92. [PMID: 9004128 PMCID: PMC1050807 DOI: 10.1136/jmg.33.12.986] [Citation(s) in RCA: 34] [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] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
Fluorescence in situ hybridisation (FISH) and conventional chromosome analysis were performed on a series of 52 patients with classical Williams-Beuren syndrome (WBS), suspected WBS, or supravalvular aortic stenosis (SVAS). In the classical WBS group, 22/23 (96%) had a submicroscopic deletion of the elastin locus on chromosome 7, but the remaining patient had a unique interstitial deletion of chromosome 11 (del(11)(q13.5q14.2)). In the suspected WBS group 2/22 (9%) patients had elastin deletions but a third patient had a complex karyotype including a ring chromosome 22 with a deletion of the long arm (r(22)(p11-->q13)). In the SVAS group, 1/7 (14%) had an elastin gene deletion, despite having normal development and minimal signs of WBS. Overall, some patients with submicroscopic elastin deletions have fewer features of Williams-Beuren syndrome than those with other cytogenetic abnormalities. These results, therefore, emphasise the importance of a combined conventional and molecular cytogenetic approach to diagnosis and suggest that the degree to which submicroscopic deletions of chromosome 7 extend beyond the elastin locus may explain some of the phenotypic variability found in Williams-Beuren syndrome.
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Affiliation(s)
- C A Joyce
- Genetics Laboratory, Salisbury District Hospital, UK
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Abstract
Bovine intestinal mucosal alkaline phosphatase is inactivated by the chelating agent EGTA. Several concentrations of the enzyme were incubated with EGTA and a range of concentrations of the substrate p-nitrophenyl phosphate to determine the substrate concentration as a function of time. As predicted by a recently developed theory [Duggleby (1986) J. Theor. Biol. 123, 67-80], catalysis ceases before all substrate is exhausted. An analysis of these final substrate concentrations according to the theory revealed that, whereas the free enzyme is unstable, the effect of EGTA is counteracted when either the substrate or product (phosphate) is bound. Comparison of the results with those obtained by direct stability measurements and steady-state kinetic experiments gave a qualitatively and quantitatively consistent body of evidence in support of this interpretation.
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Affiliation(s)
- S J Pike
- Department of Biochemistry, University of Queensland, St. Lucia, Australia
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