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Peters AD, Borsley S, Della Sala F, Cairns-Gibson DF, Leonidou M, Clayden J, Whitehead GFS, Vitórica-Yrezábal IJ, Takano E, Burthem J, Cockroft SL, Webb SJ. Switchable foldamer ion channels with antibacterial activity. Chem Sci 2020; 11:7023-7030. [PMID: 32953034 PMCID: PMC7481839 DOI: 10.1039/d0sc02393k] [Citation(s) in RCA: 25] [Impact Index Per Article: 6.3] [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: 04/27/2020] [Accepted: 06/04/2020] [Indexed: 12/19/2022] Open
Abstract
Synthetic ion channels may have applications in treating channelopathies and as new classes of antibiotics, particularly if ion flow through the channels can be controlled. Here we describe triazole-capped octameric α-aminoisobutyric acid (Aib) foldamers that "switch on" ion channel activity in phospholipid bilayers upon copper(ii) chloride addition; activity is "switched off" upon copper(ii) extraction. X-ray crystallography showed that CuCl2 complexation gave chloro-bridged foldamer dimers, with hydrogen bonds between dimers producing channels within the crystal structure. These interactions suggest a pathway for foldamer self-assembly into membrane ion channels. The copper(ii)-foldamer complexes showed antibacterial activity against B. megaterium strain DSM319 that was similar to the peptaibol antibiotic alamethicin, but with 90% lower hemolytic activity.
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Affiliation(s)
- Anna D Peters
- Department 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
| | - Stefan Borsley
- Department of Chemistry , University of Manchester , Oxford Road , Manchester M13 9PL , UK . .,EaStCHEM School of Chemistry , University of Edinburgh , Joseph Black Building, David Brewster Road , Edinburgh EH9 3FJ , UK
| | - Flavio Della Sala
- Department 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
| | - Dominic F Cairns-Gibson
- EaStCHEM School of Chemistry , University of Edinburgh , Joseph Black Building, David Brewster Road , Edinburgh EH9 3FJ , UK
| | - Marios Leonidou
- Department 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
| | - George F S Whitehead
- Department of Chemistry , University of Manchester , Oxford Road , Manchester M13 9PL , UK .
| | | | - Eriko Takano
- Department 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
| | - John Burthem
- Department of Haematology , Manchester Royal Infirmary , Manchester University NHS Foundation Trust , Manchester M13 9WL , UK.,Division of Cancer Sciences , School of Medical Sciences , University of Manchester , Manchester , UK
| | - Scott L Cockroft
- EaStCHEM School of Chemistry , University of Edinburgh , Joseph Black Building, David Brewster Road , Edinburgh EH9 3FJ , UK
| | - Simon J Webb
- Department 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
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2
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Cummings M, Peters AD, Whitehead GFS, Menon BRK, Micklefield J, Webb SJ, Takano E. Assembling a plug-and-play production line for combinatorial biosynthesis of aromatic polyketides in Escherichia coli. PLoS Biol 2019; 17:e3000347. [PMID: 31318855 PMCID: PMC6638757 DOI: 10.1371/journal.pbio.3000347] [Citation(s) in RCA: 25] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2019] [Accepted: 06/14/2019] [Indexed: 11/19/2022] Open
Abstract
Polyketides are a class of specialised metabolites synthesised by both eukaryotes and prokaryotes. These chemically and structurally diverse molecules are heavily used in the clinic and include frontline antimicrobial and anticancer drugs such as erythromycin and doxorubicin. To replenish the clinicians' diminishing arsenal of bioactive molecules, a promising strategy aims at transferring polyketide biosynthetic pathways from their native producers into the biotechnologically desirable host Escherichia coli. This approach has been successful for type I modular polyketide synthases (PKSs); however, despite more than 3 decades of research, the large and important group of type II PKSs has until now been elusive in E. coli. Here, we report on a versatile polyketide biosynthesis pipeline, based on identification of E. coli-compatible type II PKSs. We successfully express 5 ketosynthase (KS) and chain length factor (CLF) pairs-e.g., from Photorhabdus luminescens TT01, Streptomyces resistomycificus, Streptoccocus sp. GMD2S, Pseudoalteromonas luteoviolacea, and Ktedonobacter racemifer-as soluble heterodimeric recombinant proteins in E. coli for the first time. We define the anthraquinone minimal PKS components and utilise this biosynthetic system to synthesise anthraquinones, dianthrones, and benzoisochromanequinones (BIQs). Furthermore, we demonstrate the tolerance and promiscuity of the anthraquinone heterologous biosynthetic pathway in E. coli to act as genetically applicable plug-and-play scaffold, showing it to function successfully when combined with enzymes from phylogenetically distant species, endophytic fungi and plants, which resulted in 2 new-to-nature compounds, neomedicamycin and neochaetomycin. This work enables plug-and-play combinatorial biosynthesis of aromatic polyketides using bacterial type II PKSs in E. coli, providing full access to its many advantages in terms of easy and fast genetic manipulation, accessibility for high-throughput robotics, and convenient biotechnological scale-up. Using the synthetic and systems biology toolbox, this plug-and-play biosynthetic platform can serve as an engine for the production of new and diversified bioactive polyketides in an automated, rapid, and versatile fashion.
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Affiliation(s)
- Matthew Cummings
- Manchester Synthetic Biology Research Centre SYNBIOCHEM, Manchester Institute of Biotechnology, School of Chemistry, The University of Manchester, Manchester, United Kingdom
| | - Anna D. Peters
- Manchester Synthetic Biology Research Centre SYNBIOCHEM, Manchester Institute of Biotechnology, School of Chemistry, The University of Manchester, Manchester, United Kingdom
| | - George F. S. Whitehead
- Manchester Synthetic Biology Research Centre SYNBIOCHEM, Manchester Institute of Biotechnology, School of Chemistry, The University of Manchester, Manchester, United Kingdom
| | - Binuraj R. K. Menon
- Manchester Synthetic Biology Research Centre SYNBIOCHEM, Manchester Institute of Biotechnology, School of Chemistry, The University of Manchester, Manchester, United Kingdom
- Warwick Integrative Synthetic Biology Centre, WISB, School of Life Sciences, The University of Warwick, Coventry, United Kingdom
| | - Jason Micklefield
- Manchester Synthetic Biology Research Centre SYNBIOCHEM, Manchester Institute of Biotechnology, School of Chemistry, The University of Manchester, Manchester, United Kingdom
| | - Simon J. Webb
- Manchester Synthetic Biology Research Centre SYNBIOCHEM, Manchester Institute of Biotechnology, School of Chemistry, The University of Manchester, Manchester, United Kingdom
| | - Eriko Takano
- Manchester Synthetic Biology Research Centre SYNBIOCHEM, Manchester Institute of Biotechnology, School of Chemistry, The University of Manchester, Manchester, United Kingdom
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3
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Peters AD, McCallion C, Booth A, Adams JA, Rees-Unwin K, Pluen A, Burthem J, Webb SJ. Synthesis and biological activity of a CXCR4-targeting bis(cyclam) lipid. Org Biomol Chem 2019; 16:6479-6490. [PMID: 30155533 DOI: 10.1039/c8ob01439f] [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] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
A bis(cyclam)-capped cholesterol lipid designed to bind C-X-C chemokine receptor type 4 (CXCR4) was synthesised in good overall yield from 4-methoxyphenol through a seven step synthetic route, which also provided a bis(cyclam) intermediate bearing an octaethyleneglycol-primary amine that can be easily derivatised. This bis(cyclam)-capped cholesterol lipid was water soluble and self-assembled into micellar and non-micellar aggregates in water at concentrations above 8 μM. The bioactivity of the bis(cyclam)-capped cholesterol lipid was assessed using primary chronic lymphocytic leukaemia (CLL) cells, first with a competition binding assay then with a chemotaxis assay along a C-X-C motif chemokine ligand 12 (CXCL12) concentration gradient. At 20 μM, the bis(cyclam)-capped cholesterol lipid was as effective as the commercial drug AMD3100 for preventing the migration of CLL cells, despite a lower affinity for CXCR4 than AMD3100.
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Affiliation(s)
- Anna D Peters
- School of Chemistry, University of Manchester, Oxford Road, Manchester M13 9PL, UK
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4
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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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5
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Adam C, Peters AD, Lizio MG, Whitehead GFS, Diemer V, Cooper JA, Cockroft SL, Clayden J, Webb SJ. The Role of Terminal Functionality in the Membrane and Antibacterial Activity of Peptaibol-Mimetic Aib Foldamers. Chemistry 2018; 24:2249-2256. [PMID: 29210477 DOI: 10.1002/chem.201705299] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [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: 11/08/2017] [Indexed: 01/04/2023]
Abstract
Peptaibols are peptide antibiotics that typically feature an N-terminal acetyl cap, a C-terminal aminoalcohol, and a high proportion of α-aminoisobutyric acid (Aib) residues. To establish how each feature might affect the membrane-activity of peptaibols, biomimetic Aib foldamers with different lengths and terminal groups were synthesised. Vesicle assays showed that long foldamers (eleven Aib residues) with hydrophobic termini had the highest ionophoric activity. C-terminal acids or primary amides inhibited activity, while replacement of an N-terminal acetyl with an azide group made little difference. Crystallography showed that N3 Aib11 CH2 OTIPS folded into a 310 helix 2.91 nm long, which is close to the bilayer hydrophobic width. Planar bilayer conductance assays showed discrete ion channels only for N-acetylated foldamers. However long foldamers with hydrophobic termini had the highest antibacterial activity, indicating that ionophoric activity in vesicles was a better indicator of antibacterial activity than the observation of discrete ion channels.
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Affiliation(s)
- Catherine Adam
- School of Chemistry, University of Bristol, Cantock's Close, Bristol, BS8 1TS, UK
| | - Anna D Peters
- 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
| | - M Giovanna Lizio
- 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
| | - George F S Whitehead
- School of Chemistry, University of Manchester, Oxford Road, Manchester, M13 9PL, UK
| | - Vincent Diemer
- 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
| | - James A Cooper
- EaStCHEM School of Chemistry, University of Edinburgh, Joseph Black Building, David Brewster Road, Edinburgh, EH9 3FJ, UK
| | - Scott L Cockroft
- EaStCHEM School of Chemistry, University of Edinburgh, Joseph Black Building, David Brewster Road, Edinburgh, EH9 3FJ, UK
| | - Jonathan Clayden
- School of Chemistry, University of Bristol, Cantock's Close, Bristol, BS8 1TS, 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
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6
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Abstract
There is growing evidence that in a variety of organisms the majority of meiotic recombination events occur at a relatively small fraction of loci, known as recombination hotspots. If hotspot activity results from the DNA sequence at or near the hotspot itself (in cis), these hotspots are expected to be rapidly lost due to biased gene conversion, unless there is strong selection in favor of the hotspot itself. This phenomenon makes it very difficult to maintain existing hotspots and even more difficult for new hotspots to evolve; it has therefore come to be known as the "hotspot conversion paradox." I develop an analytical framework for exploring the evolution of recombination hotspots under the forces of selection, mutation, and conversion. I derive the general conditions under which cis- and trans-controlled hotspots can be maintained, as well as those under which new hotspots controlled by both a cis and a trans locus can invade a population. I show that the conditions for maintenance of and invasion by trans- or cis-plus-trans-controlled hotspots are broader than for those controlled entirely in cis. Finally, I show that a combination of cis and trans control may allow for long-lived polymorphisms in hotspot activity, the patterns of which may explain some recently observed features of recombination hotspots.
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Affiliation(s)
- A D Peters
- Department of Zoology, University of Wisconsin, Madison, Wisconsin 53706, USA.
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7
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Abstract
We explored the evolution of recombination under antagonistic coevolution, concentrating on the equilibrium frequencies of modifier alleles causing recombination in initially nonrecombining populations. We found that the equilibrium level of recombination in the host depended not only on parasite virulence, but also on the strength of the modifier allele, and on whether or not the modifier was physically linked to the parasite interaction loci. Nonetheless, the maximum level of recombination for linked loci at equilibrium was about 0.3 (60% of free recombination) for interactions with highly virulent parasites; the level decreased for unlinked modifiers, and for lower levels of parasite virulence. We conclude that recombination spreads because it provides a combination of an immediate (next-generation) fitness benefit and a delayed (two or more generations) increase in the rate of response to directional selection. The relative impact of these two mechanisms depends on the virulence of parasites early in the spread of the modifier, but a trade-off between the two dictates the equilibrium modifier frequency for all nonzero virulences that we examined. In addition, population mean fitness was higher in populations at intermediate equilibria than populations fixed for free recombination or no recombination. The difference, however, was not enough on its own to overcome the two-fold cost of producing males.
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Affiliation(s)
- A D Peters
- Department of Zoology, University of British Columbia, Vancouver, BC, Canada and Department of Zoology, University of Wisconsin-Madison, Madison, WI 53706, USA
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8
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Peters AD, Halligan DL, Whitlock MC, Keightley PD. Dominance and Overdominance of Mildly Deleterious Induced Mutations for Fitness Traits inCaenorhabditis elegans. Genetics 2003; 165:589-99. [PMID: 14573472 PMCID: PMC1462798 DOI: 10.1093/genetics/165.2.589] [Citation(s) in RCA: 58] [Impact Index Per Article: 2.8] [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: 11/14/2022] Open
Abstract
AbstractWe estimated the average dominance coefficient of mildly deleterious mutations (h, the proportion by which mutations in the heterozygous state reduce fitness components relative to those in the homozygous state) in the nematode Caenorhabditis elegans. From 56 worm lines that carry mutations induced by the point mutagen ethyl methanesulfonate (EMS), we selected 19 lines that are relatively high in fitness and estimated the viabilities, productivities, and relative fitnesses of heterozygotes and homozygotes compared to the ancestral wild type. There was very little effect of homozygous or heterozygous mutations on egg-to-adult viability. For productivity and relative fitness, we found that the average dominance coefficient, h, was ∼0.1, suggesting that mildly deleterious mutations are on average partially recessive. These estimates were not significantly different from zero (complete recessivity) but were significantly different from 0.5 (additivity). In addition, there was a significant amount of variation in h among lines, and analysis of average dominance coefficients of individual lines suggested that several lines showed overdominance for fitness. Further investigation of two of these lines partially confirmed this finding.
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Affiliation(s)
- A D Peters
- Institute of Cell, Animal and Population Biology, University of Edinburgh, Edinburgh EH9 3JT, United Kingdom.
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9
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Abstract
Synergistic epistasis, in which deleterious mutations tend to magnify each other's effects, is a necessary component of the mutational deterministic hypothesis for the maintenance of sexual production. We tested for epistasis for life-history traits in the soil nematode Caenorhabditis elegans by inducing mutations in two genetic backgrounds: a wild-type strain and a set of genetically loaded lines that contain large numbers of independent mildly detrimental mutations. There was no significant difference between the effect of new mutations on the wild-type background and the genetically loaded background for four out of five fitness correlates. In these four cases, the maximum level of epistasis compatible with the data was very low. The fifth trait, late productivity, is not likely to be an important component of fitness. This suggests either that specific environmental conditions are required to cause epistasis or that synergistic epistasis is not a general phenomenon. We also suggest a new mechanism by which deleterious mutations may provide an advantage to sexual reproduction under low selection coefficients.
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Affiliation(s)
- A D Peters
- Institute of Cell, Animal and Population Biology, University of Edinburgh, Edinburgh EH9 3JT, United Kingdom.
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10
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Affiliation(s)
- S A West
- Institute of Cell, Animal, and Population Biology, University of Edinburgh, UK
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11
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Keightley PD, Davies EK, Peters AD, Shaw RG. Properties of ethylmethane sulfonate-induced mutations affecting life-history traits in Caenorhabditis elegans and inferences about bivariate distributions of mutation effects. Genetics 2000; 156:143-54. [PMID: 10978281 PMCID: PMC1461248 DOI: 10.1093/genetics/156.1.143] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.1] [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: 11/14/2022] Open
Abstract
The homozygous effects of ethylmethane sulfonate (EMS)-induced mutations in Caenorhabditis elegans are compared across life-history traits. Mutagenesis has a greater effect on early than late reproductive output, since EMS-induced mutations tend to cause delayed reproduction. Mutagenesis changes the mean and variance of longevity much less than reproductive output traits. Mutations that increase total or early productivity are not detected, but the net effect of mutations is to increase and decrease late productivity to approximately equal extents. Although most mutations decrease longevity, a mutant line with increased longevity was found. A flattening of mortality curves with age is noted, particularly in EMS lines. We infer that less than one-tenth of mutations that have fitness effects in natural conditions are detected in the laboratory, and such mutations have moderately large effects ( approximately 20% of the mean). Mutational correlations for life-history traits are strong and positive. Correlations between early or late productivity and longevity are of similar magnitude. We develop a maximum-likelihood procedure to infer bivariate distributions of mutation effects. We show that strong mutation-induced genetic correlations do not necessarily imply strong directional correlations between mutational effects, since correlation is also generated by lines carrying different numbers of mutations.
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Affiliation(s)
- P D Keightley
- Institute of Cell, Animal and Population Biology, University of Edinburgh, Edinburgh EH9 3JT, Scotland.
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12
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Abstract
Host-parasite coevolution has been shown to provide an advantage to recombination, but the selective mechanism underlying this advantage is unclear. One possibility is that recombination increases the frequency of advantageous genotypes that are disproportionately rare because of fluctuating epistasis. However, for this mechanism to work, epistasis for fitness must fluctuate over a very narrow timescale: two to five generations. Alternatively, recombination may speed up the response to directional selection by breaking up linkage disequilibria that decrease additive genetic variance. Here we analyze the results of a numerical simulation of host-parasite coevolution to assess the importance of these two mechanisms. We find that linkage disequilibria may tend to increase, rather than decrease, additive genetic variance. In addition, the sign of epistasis changes every two to five generations under several of the parameter values investigated, and epistasis and linkage disequilibrium are frequently of opposite signs. These results are consistent with the idea that selection for recombination is mediated by fluctuating epistasis. Finally, we explore the conditions under which an allele causing free recombination can spread in a nonrecombining host population and find general agreement between the predictions of a population genetic model of fluctuating epistasis and our simulation model.
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13
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Abstract
Deleterious mutations with very small phenotypic effects could be important for several evolutionary phenomena, but the extent of their contribution has been unknown. Fitness effects of induced mutations in lines of Caenorhabditis elegans were measured using a system for which the number of deleterious point mutations in the DNA can be estimated. In fitness assays, only about 4 percent of the deleterious mutations fixed in each line were detectable. The remaining 96 percent, though cryptic, are significant for mutation load and, potentially, for the evolution of sex.
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Affiliation(s)
- E K Davies
- Institute of Cell, Animal and Population Biology, University of Edinburgh, West Mains Road, Edinburgh EH9 3JT, UK
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14
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Jokela J, Lively CM, Taskinen J, Peters AD. Effect of starvation on parasite-induced mortality in a freshwater snail ( Potamopyrgus antipodarum). Oecologia 1999; 119:320-325. [PMID: 28307754 DOI: 10.1007/s004420050792] [Citation(s) in RCA: 55] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Affiliation(s)
- J Jokela
- Experimental Ecology, ETH-Zürich, ETH-Zentrum NW, CH-8092 Zürich, Switzerland , Tel.: +41-1-6327106, Fax: +41-1-6321271, , , , , , CH
| | - C M Lively
- Department of Biology, Indiana University, Bloomington, IN 47405, USA, , , , , , IN
| | - J Taskinen
- Department of Biological and Environmental Sciences, University of Jyväskylä, Box 35, FIN-40351 Jyväskylä, Finland, , , , , , FI
| | - A D Peters
- Department of Biology, Indiana University, Bloomington, IN 47405, USA, , , , , , IN
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15
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Abstract
Determining the way in which deleterious mutations interact in their effects on fitness is crucial to numerous areas in population genetics and evolutionary biology. For example, if each additional mutation leads to a greater decrease in log fitness than the last (synergistic epistasis), then the evolution of sex and recombination may be favored to facilitate the elimination of deleterious mutations. However, there is a severe shortage of relevant data. Three relatively simple experimental methods to test for epistasis between deleterious mutations in haploid species have recently been proposed. These methods involve crossing individuals and examining the mean and/or skew in log fitness of the offspring and parents. The main aim of this paper is to formalize these methods, and determine the most effective way in which tests for epistasis could be carried out. We show that only one of these methods is likely to give useful results: crossing individuals that have very different numbers of deleterious mutations, and comparing the mean log fitness of the parents with that of their offspring. We also reconsider experimental data collected on Chlamydomonas moewussi using two of the three methods. Finally, we suggest how the test could be applied to diploid species.
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Affiliation(s)
- S A West
- Institute of Cell, Animal and Population Biology, University of Edinburgh, Edinburgh EH9 3JT, United Kingdom.
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16
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Abstract
Few studies investigating the effectiveness of methadone treatment for opiate dependence have emanated from the UK. The core feature of treatment offered by Lothian Health's Community Drug Problems Service involves the prescribing of methadone by the client's general practitioner. Of a cohort of 494 daily users of opiates attending the service, 39% remained in treatment for at least 12 months. Up to 2 years in-treatment follow-up revealed significant improvement in injecting and criminal behaviour. There were no HIV seroconversions reported during the treatment period. There was no improvement in injection equipment sharing, condom use, illicit drug use or employment status. 'Satisfactory' discharge was achieved for 40% of those in treatment for at least 6 months. These results are largely consistent with the outcomes of methadone programmes elsewhere.
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Affiliation(s)
- A D Peters
- Community Drug Problems Service, Edinburgh, UK
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17
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Peters AD, Meiers JC. Effect of polymerization mode of a dual-cured resin cement on time-dependent shear bond strength to porcelain. Am J Dent 1996; 9:264-8. [PMID: 9545881] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
PURPOSE To evaluate the shear bond strengths to porcelain and setting times of a dual-cured resin cement with light/chemical curing (dual) or chemical only curing versus time. MATERIALS AND METHODS Variolink resin cement was bonded to specimens of etched, silanated porcelain. Groups of specimens were cured by dual cured or by chemical curing only. Shear bond strengths were recorded at 2, 3, 5, 60 minutes and 24 hours for dual cured and at 10, 20, 40, 50, 60 minutes and 24 hours for chemical-cured only after mixing. Kinetic-temperature profiles of dual and chemical curing modes of cement were calculated. RESULTS Maximum bond strengths and time to attainment were 17.5 +/- 2.7 MPa at 60 minutes for chemical-cured and 26.1 +/- 2.3 MPa at 5 minutes for dual-cured. The peak in the kinetic-temperature setting profiles were 14.1 +/- 0.9 minutes for chemical curing and 52.2 +/- 5.2 seconds for dual curing. Dual curing provided significantly higher shear bond strengths versus chemical curing at both the 60-minute and 24-hour time periods.
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Affiliation(s)
- A D Peters
- Dept of Restorative Dentistry & Endodontology, School of Dental Medicine, UCHC, Farmington 06030-1715, USA
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18
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Abstract
A multi-site sample of currently-injecting drug users (IDUs) comprising 344 men and 136 women was recruited in Edinburgh. Sixty-seven per cent of the sample said they had at some time used injecting equipment already used by another person and 25% admitted doing so in the 6 months before interview. Whereas women who injected with used equipment obtained it predominantly from a sexual partner, for men the source was more often a close friend or someone whose HIV status they were unlikely to know. In the 6 months before interview, 40% of men, compared with 20% of women, had more than one heterosexual partner. This difference was associated with a higher proportion of men with steady partners also having casual partners. Women IDUs were more likely to have regular partners who injected (57% vs 26%). Though sharing of injecting equipment has already diminished in Edinburgh, further measures are needed to eliminate it. For injectors here, the risk of infection from unprotected heterosexual intercourse may now be greater than that from sharing injecting equipment, particularly for women. Other methods of encouraging changes in sexual behaviour need to be investigated and successful ones promoted.
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Peters AD, Jaffé C, Delos JB. Quantum manifestations of bifurcations of classical orbits: An exactly solvable model. Phys Rev Lett 1994; 73:2825-2828. [PMID: 10057205 DOI: 10.1103/physrevlett.73.2825] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
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Peters AD, Reid MM, Griffin SG. Edinburgh drug users: are they injecting and sharing less? AIDS 1994; 8:521-8. [PMID: 8011257] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
OBJECTIVE To describe epidemiological trends in injecting and equipment sharing among a sample drawn from a drug-using population with a high rate of HIV infection. DESIGN A structured interview was administered prior to treatment to cross-sectional samples of drug users over the period 1988-1991. Reports of injecting, sharing and HIV infection were compared annually. SETTING Lothian Health Board's Community Drug Problems Service is a secondary level service offering harm reduction and treatment of dependency. PARTICIPANTS A total of 734 consecutively referred drug users resident in Edinburgh. Re-referrals in the same calendar year were excluded. MEASURES History of injecting and sharing, recent injecting and sharing, HIV testing history, drugs used in previous month and substitute prescription status. RESULTS Large reductions in the frequency of injecting were found over the 4 years even among those who were not receiving oral substitutes. More participants in latter years were receiving prescriptions combining opioids and benzodiazepines. Fewer of those interviewed latterly had ever shared injecting equipment. Among recent injectors just as many share equipment as previously. HIV prevalence did not vary significantly over the period. An HIV prevalence of 19% was reported among recent injectors. CONCLUSIONS Edinburgh's drug users are engaging in far safer drug-taking behaviour than previously. Levels of HIV in this population suggest that the epidemic is being contained. A small number persist in high risk drug-related activities. Further investigation of the characteristics of these individuals and the need to develop novel methods of influencing their behaviour are recommended.
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Affiliation(s)
- A D Peters
- Community Drug Problems Service, Lothian Health Board, Edinburgh, UK
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Peters AD, Delos JB. Photodetachment cross section of H- in crossed electric and magnetic fields. II. Quantum formulas and their reduction to the result of the closed-orbit theory. Phys Rev A 1993; 47:3036-3043. [PMID: 9909276 DOI: 10.1103/physreva.47.3036] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
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Peters AD, Delos JB. Photodetachment cross section of H- in crossed electric and magnetic fields. I. Closed-orbit theory. Phys Rev A 1993; 47:3020-3035. [PMID: 9909275 DOI: 10.1103/physreva.47.3020] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
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Kay RW, Peters AD. A pilot survey of client opinion of the Lothian Community Drug Problem Service: likes, dislikes, efficacy and improvements. Health Bull (Edinb) 1992; 50:32-8. [PMID: 1319417] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
An open ended unstructured questionnaire was used to find out the opinion of clients of the Community Drug Problem Service of Lothian Health Board, concerning how the service had helped them and for suggestions for improvement. A total of 63 questionnaires were returned over a six month period. Analysis showed that 77% of respondents valued counselling services but 26% complained of too low oral substitute drug dosage. Improvement in personal development, stabilised drug use, less criminality and stopping injecting were reported as being the main benefits. A more detailed self reporting questionnaire will be developed from this pilot study to answer some of the questions raised and for use as a routine part of ongoing service monitoring and evaluation.
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Affiliation(s)
- R W Kay
- Community Drug Problem Service, Royal Edinburgh Hospital
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Scurletis TD, Peters AD, Robie WA. Attitudes of pediatricians toward day care. Pediatrics 1966; 38:44-7. [PMID: 5936879] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/17/2023] Open
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Peters AD. Striæ Atrophicæ.? Dyspituitarism. Proc R Soc Med 1939; 32:1578-1580. [PMID: 20916546] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/29/2023]
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Peters AD. Striæ Atrophicæ.? Dyspituitarism. Proc R Soc Med 1939; 32:1578-80. [PMID: 19992149 PMCID: PMC1998083] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
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Peters AD. Lichen Pilaris Seu Spinulosus. Proc R Soc Med 1939; 32:1031-1032. [PMID: 19992015 PMCID: PMC1997886] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
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Peters AD, Macbeth AN. Partial Resolution of Leukoplakia Vulvæ under Œstrin Therapy. Proc R Soc Med 1937; 30:1330-1333. [PMID: 20915653] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/29/2023]
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Peters AD, Macbeth AN. Partial Resolution of Leukoplakia Vulvæ under Œstrin Therapy. Proc R Soc Med 1937; 30:1330-3. [PMID: 19991256 PMCID: PMC2076501] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
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Peters AD. Granulosis Rubra Nasi. Proc R Soc Med 1937; 30:1054. [PMID: 19991180 PMCID: PMC2076337] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
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Peters AD. Case of Angioma Serpiginosum. Proc R Soc Med 1937; 30:363-364. [PMID: 19990980 PMCID: PMC2076424] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
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Peters AD. Dercum's Disease. Proc R Soc Med 1935; 28:367-368. [PMID: 19990131 PMCID: PMC2205253] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
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Peters AD. Case of Hirsuties treated by Ovarian Follicular Hormone. Proc R Soc Med 1934; 27:809-813. [PMID: 19989786 PMCID: PMC2205025] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
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