| 1. |
- Kehoe, Laura, et al.
(författare)
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Make EU trade with Brazil sustainable
- 2019
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Ingår i: Science. - : American Association for the Advancement of Science (AAAS). - 0036-8075 .- 1095-9203. ; 364:6438, s. 341-
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)
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| 2. |
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| 3. |
- Cleland, Dougal, et al.
(författare)
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Molecular dynamics approaches to the design and synthesis of PCB targeting molecularly imprinted polymers: interference to monomer-template interactions in imprinting of 1,2,3-trichlorobenzene
- 2014
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Ingår i: Organic and biomolecular chemistry. - : Royal Society of Chemistry (RSC). - 1477-0520 .- 1477-0539. ; 12:5, s. 844-853
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Tidskriftsartikel (refereegranskat)abstract
- The interactions between each component of the pre-polymerisation mixtures used in the synthesis of molecularly imprinted polymers (MIP) specific for 1,2,3,4,5-pentachlorobenzene (1) and 1,2,3-trichlorobenzene (2) were examined in four molecular dynamics simulations. These simulations revealed that the relative frequency of functional monomer template (FM T) interactions was consistent with results obtained by the synthesis and evaluation of the actual MIPs. The higher frequency of 1 interaction with tri-methylstyrene (TMS; 54.7%) than 1 interaction with pentafluorostyrene (PFS; 44.7%) correlated with a higher imprinting factor (IF) of 2.1 vs. 1.7 for each functional monomer respectively. The higher frequency of PFS interactions with 2 (29.6%) than TMS interactions with 2 (1.9%) also correlated well with the observed differences in IF (3.7) of 2 MIPs imprinted using PFS as the FM than the IF (2,8) of 2 MIPs imprinted using TMS as the FM. The TMS-1 interaction dominated the molecular simulation due to high interaction energies, but the weaker TMS-2 resulted in low interaction maintenance, and thus lower IF values. Examination of the other pre-polymerisation mixture components revealed that the low levels of TMS-2 interaction was, in part, due to interference caused by the cross linker (CL) ethyleneglycol dimethylacrylate (EGDMA) interactions with TMS. The main reason was, however, attributed to MeOH interactions with TMS in both a hydrogen bond and perpendicular configuration. This positioned a MeOH directly above the it-orbital of all TMS for an average of 63.8% of MD2 creating significant interference to pi-pi stacking interactions between 2 and TMS. These findings are consistent with the deviation from the 'normal' molecularly imprinted polymer synthesis ratio of 1 : 4 : 20 (T : FM : CL) of 20 : 1 : 29 and 15 : 6 : 29 observed with 2 and TMS and PFS respectively. Our molecular dynamics simulations correctly predicted the high level of interference from other MIP synthesis components. The effect on PFS-1 interaction by MeOH was significantly lower and thus this system was not adversely affected.
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| 4. |
- Golker, Kerstin, et al.
(författare)
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Influence of composition and morphology on template recognition in molecularly imprinted polymers
- 2013
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Ingår i: Macromolecules. - : American Chemical Society (ACS). - 0024-9297 .- 1520-5835. ; 46:4, s. 1408-1414
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Tidskriftsartikel (refereegranskat)abstract
- A combination of theoretical and experimental studies has provided correlations between molecularly imprinted polymer composition, morphology, and recognition behavior obtained using a series of bupivacaine-imprinted methacrylic acid (MAA)–ethylene glycol dimethacrylate copolymers differing in molar ratios of the respective monomers. Results extracted from analysis of molecular dynamics (MD) trajectory data demonstrated that stability and frequency of interactions between bupivacaine and the monomers in the prepolymerization phase were strongly affected by minor changes in polymer composition, which in turn affected binding site affinity and heterogeneity of the imprinted polymers. Moreover, through the characterization of polymer morphology, we show that higher molar fractions of MAA resulted in polymeric materials with increased pore size, a feature that enhanced the binding capacity of the polymers. Furthermore, the results presented point at the strength of MD for predicting MIP-template binding capacity and affinity.
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| 5. |
- Golker, Kerstin, 1969-, et al.
(författare)
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The influence of a methyl substituent on molecularly imprinted polymer morphology and recognition – Acrylic acid versus methacrylic acid
- 2017
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Ingår i: European Polymer Journal. - : Elsevier. - 0014-3057 .- 1873-1945. ; 92, s. 137-149
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Tidskriftsartikel (refereegranskat)abstract
- In this report, we have investigated factors contributing to the morphology and template recognition of bupivacaine-imprinted copolymers of methacrylic acid (MAA) and ethyleneglycol dimethacrylate (EGDMA). To this end, MAA, the most commonly used functional monomer in non-covalent molecular imprinting protocols, was compared and contrasted with the closely related acrylic acid (AA) in terms of polymer morphologies, recognition characteristics, and molecular level events in the corresponding pre-polymerization mixtures. Two series of analogous bupivacaine-imprinted EGDMA-copolymers containing increasing fractions of either AA or MAA were studied through all-component MD simulations in the pre-polymerization phase, equilibrium binding experiments on corresponding synthesized polymers and morphology characterization by N2-sorption measurements. A higher degree of hydrogen bonding frequency between respective functional monomer and bupivacaine was recorded for the mixtures containing AA compared to those containing MAA. In contrast, results from binding experiments demonstrated higher binding capacities for the polymers prepared with MAA than for those prepared with AA, which is explained by differences in polymer morphology. The surface areas and pore volumes of the AA-polymers were higher than for the MAA-polymers and the overall pore structure in the AA-polymers was ink-bottle shaped while the pores in the MAA-polymers were slit-shaped. We suggest that the methyl substituent of MAA contributes to differences in the reaction kinetics for AA and MAA during polymerization and resulted in different morphologies, in particular pore shape, which affected mass-transfer and consequently the binding qualities of the materials. © 2017 Elsevier Ltd
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| 6. |
- Golker, Kerstin, et al.
(författare)
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Towards Molecular Dynamics-Based Rational Design of Polymeric Recognition Systems
- 2010
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Konferensbidrag (refereegranskat)abstract
- Molecular imprinting is a technique used to design polymeric recognition materials with selectivity for a predetermined structure. The molecular imprinting process generates cavities in the polymer matrix that are complementary in size, shape and functionality to the template-structure. The recognition properties of molecularly imprinted polymers (MIPs) are comparable to those of antibodies and enzymes, which make MIPs utilizable in a wide range of application areas including biomimetic assays and biosensors [1]. Previous studies have shown that the prepolymerization step is central for the establishment of high affinity binding sites in MIPs [2]. However, our understanding of the physical mechanisms underlying MIP formation and template recognition is still limited. With the rapid increase of computational power and the development of suitable software molecular dynamics (MD) simulation methods have become a valuable theoretical tool to aid our understanding of the molecular imprinting process, and even in the development of rational design strategies [2]. Recently the first simulation of a complete prepolymerization mixture was presented [3].Here we present 10 ns MD simulations of a series of all-component prepolymerization mixtures. The simulated systems were assembled with different molar ratios using the local anaesthetic bupivacaine as the template, methacrylic acid (MAA) as the functional monomer, ethylene glycol dimethacrylate (EGDMA) as the crosslinker, 2,2’-azobis-(2-methylpropionitrile) (AIBN) as the initiator and toluene as the solvent. The simulations were performed using the AMBER (v. 10.0 UCSF, San Francisco, CA) suite of programs (4) and the GAFF [6] force field. Molecular trajectories were evaluated with radial distribution functions and hydrogen bond analysis. ReferencesAlexander, C.; Andersson, H. S.; Andersson, L. I.; Ansell, R. J.; Kirsch, N.; Nicholls, I. A.; O´Mahony, J.; Whitcombe, J., J. Mol. Recognit. (2006), 19, 106-180Nicholls, I. A.; Andersson, H. S.; Charlton, C.; Henschel, H.; Karlsson, B. C. G.; Karlsson, J. G.; O´Mahony, J.; Rosengren, A. M.; Rosengren, K. J.; Wikman, S. Biosens. Bioelectron. (2009), 25, 543-552Karlsson, B. C. G.; O´Mahony, J.; Karlsson, J. G.; Bengtsson, H.; Eriksson, L. A.; Nicholls, I. A. J. Am. Chem. Soc. (2009), 131, 13297-13304Case, D. A.; Cheatham, T. E.; Darden, T.; Gohlke, H.; Luo, R.; Merz, K. M.; Onufriev, A.; Simmerling, C.; Wang, B.; Woods, R. J. Comput. Chem. (2009), 26, 1668-1688Wang, J.; Wolf, R. M.; Caldwell, J. W.; Kollman, P. A.; Case, D. A. J. Comput. Chem. (2004), 25, 1157-1174
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| 7. |
- Golker, Kerstin, et al.
(författare)
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Towards Molecular Dynamics-Based Rational Design of Synthetic Polymer Recognition Systems
- 2010
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Konferensbidrag (refereegranskat)abstract
- Molecularly imprinted polymers (MIPs) are polymeric receptors with selectivity for a predetermined structure. The molecular imprinting process generates cavities in a synthetic polymer matrix that are complementary in size, shape and functionality to the template. MIPs exhibit recognition properties analogous to their biological counterparts, such as antibodies, and can be utilized in a wide range of application areas [1]. Nonetheless, the physical mechanisms underlying MIP formation and template recognition are still poorly understood. Molecular dynamics (MD) based computer simulations are a valuable theoretical tool which may be used to aid our understanding of the molecular imprinting process, and even for the development of rational design strategies [2]. Recently the first MD simulation of a complete prepolymerization mixture was presented [3].In the present work, MD simulations of a series of all-component prepolymerization mixtures were performed, using the local anaesthetic bupivacaine as the template, methacrylic acid (MAA) as the functional monomer, ethylene glycol dimethacrylate (EGDMA) as the crosslinker, 2,2’-azobis-(2-methylpropionitrile) (AIBN) as the initiator and toluene as the solvent. The simulated systems differed in the molar fraction of MAA. Systems were evaluated with radial distribution functions and hydrogen bond analyses. By correlating the results with the rebinding behaviour of a series of synthesized MIPs the importance of the stoichiometry between template, functional monomer and crosslinker was highlighted. The analysis of the MD simulations revealed strong competition for hydrogen bonding between the carbonyl oxygen’s of MAA and EGDMA and the amide proton of bupivacaine. Moreover, the hydrogen bonding contact between EGDMA and bupivacaine remained nearly unaffected by the varied molar fraction MAA in the different systems demonstrating the role of the crosslinker being more important as generally accepted. References [1] Alexander, C.; Andersson, H. S.; Andersson, L. I.; Ansell, R. J.; Kirsch, N.; Nicholls, I. A.; O´Mahony, J.; Whitcombe, J., J. Mol. Recognit., 19, 106-180 (2006)[2] Nicholls, I. A.; Andersson, H. S.; Charlton, C.; Henschel, H.; Karlsson, B. C. G.; Karlsson, J. G.; O´Mahony, J.; Rosengren, A. M.; Rosengren, K. J.; Wikman, S. Biosens. Bioelectron., 25, 543-552 (2009)[3] Karlsson, B. C. G.; O´Mahony, J.; Karlsson, J. G.; Bengtsson, H.; Eriksson, L. A.; Nicholls, I. A. J. Am. Chem. Soc., 131, 13297-13304 (2009)
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| 8. |
- Golker, Kerstin, et al.
(författare)
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Towards the use of molecular dynamics as a predictive tool in the design of molecularly imprinted polymers
- 2010
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Konferensbidrag (refereegranskat)abstract
- Through the rapid increase in computational power and the development of suitable software, molecular dynamics (MD) has become a promising tool for use in the development of molecularly imprinted polymers (MIPs).1 MD is a computational method based on Newtonian mechanics, which enables the simultaneous simulation of thousands of discrete molecules, and can be used to establish the states of the molecular species present in MIP-prepolymerization mixtures. As detailed understanding of the molecular basis for formation of high affinity MIP sites is still lacking and the physical mechanism underlying specific recognition is still a matter of debate, the use of MD as a tool to investigate MIP-prepolymerization mixtures is highly motivated.1 Recently the first MD simulation of an all-component prepolymerization mixture was presented, which gave a detailed picture of the underlying monomer-template interactions important for the “molecular memory” in MIPs.2Here, we present results obtained from a series of MD simulations representing all-component MIP/REF prepolymerization mixtures assembled with differences in stoichiometries of functional and crosslinking monomer. In these mixtures, the local anaesthetic drug bupivacaine was used as a template, methacrylic acid as the functional monomer, ethylene dimethacrylate as crosslinking monomer, 2,2’-azobis-(2-methylpropionitrile) as the initiator and toluene as the solvent. Bupivacaine complexation in each system was evaluated with radial distribution functions and hydrogen bond analyses. By correlating the results with the rebinding behaviour of a series of synthesized bupivacaine-MIPs, the relationship between the degree of crosslinking and MIP-performance was highlighted.[1] Nicholls, I. A.; Andersson, H. S.; Charlton, C.; Henschel, H.; Karlsson, B. C. G.; Karlsson, J. G.; O´Mahony, J.; Rosengren, A. M.; Rosengren, K. J.; Wikman, S. Biosens. Bioelectron., 25, 543-552 (2009)[2] Karlsson, B. C. G.; O´Mahony, J.; Karlsson, J. G.; Bengtsson, H.; Eriksson, L. A.; Nicholls, I. A. J. Am. Chem. Soc., 131, 13297-13304 (2009)
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| 9. |
- Karlsson, Björn C. G., et al.
(författare)
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How warfarin’s structural diversity influences its phospholipid bilayer membrane permeation
- 2013
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Ingår i: Journal of Physical Chemistry B. - : American Chemical Society (ACS). - 1520-6106 .- 1520-5207. ; 117:8, s. 2384-2395
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Tidskriftsartikel (refereegranskat)abstract
- The role of the structural diversity of the widely used anticoagulant drug warfarin on its distribution in 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC) bilayer membranes was investigated using a series of both restrained (umbrella sampling) and unrestrained molecular dynamics simulations. Data collected from unrestrained simulations revealed favorable positions for neutral isomers of warfarin, the open side chain form (OCO), and the cyclic hemiketal (CCO), along the bilayer normal close to the polar headgroup region and even in the relatively distant nonpolar lipid tails. The deprotonated open side chain form (DCO) was found to have lower affinity for the DOPC bilayer membrane relative to the neutral forms, with only a small fraction interacting with the membrane, typically within the polar headgroup region. The conformation of OCO inside the lipid bilayer was found to be stabilized by intramolecular hydrogen bonding thereby mimicking the structure of CCO. Differences in free energies, for positions of OCO and CCO inside the bilayer membrane, as compared to positions in the aqueous phase, were −97 and −146 kJ·mol–1. Kinetic analysis based on the computed free energy barriers reveal that warfarin will diffuse through the membranes within hours, in agreement with experimental results on warfarin’s accumulation in the plasma, thus suggesting a passive diffusion mechanism. We propose that this membrane transport may be an isomerization-driven process where warfarin adapts to the various local molecular environments encountered under its journey through the membrane. Collectively, these results improve our understanding of the influence of warfarin’s structural diversity on the drug’s distribution and bioavailability, which in turn may provide insights for developing new formulations of this important pharmaceutical to better address its narrow therapeutic window.
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| 10. |
- Karlsson, Björn C. G., et al.
(författare)
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The Effect of Warfarin’s Structural Diversity on Permeation Across a DPPC Bilayer Membrane
- 2010
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Konferensbidrag (refereegranskat)abstract
- Warfarin is an oral anticoagulant drug used to prevent thrombolic disorders such as myocardial infarction and stroke by inhibiting the active site of vitamin-K dependent epoxide reductase (VKOR) [1]. Despite being in widespread use and having a narrow therapeutic window, its mechanisms of action are not yet fully understood and incorrect warfarin dosage often leads to severe side effects. A factor limiting our understanding of warfarin’s bioavailability is warfarin’s structural diversity, which has been shown to be strongly affected by the nature of molecular environment e.g. solvent polarity and pH [2-7]. One of the major factors contributing to a drug’s biological effect is membrane transport, a process involving exposure of warfarin to environments of quite different character. Since a drug’s transport across membrane may include both active transport by carriers as well as diffusion-controlled processes, it may be envisaged that in order to fully predict warfarin’s anticoagulant effect these mechanisms must be carefully elucidated. Molecular dynamics (MD) simulations have previously been performed in order to obtain detailed information on static equilibrium as well as dynamic properties of small organic drugs in biomembranes. One of the most studied lipids in cell membrane simulations has been dipalmitoylphosphatidylcholine (DPPC) which is the most abundant phospholipid in cell membranes. Here we present lipid bilayer membrane transport properties for a series of warfarin structures previously reported in the literature using a fully solvated DPPC membrane model. Data extracted from simulations shed light on differences in membrane partioning as well as mobilities of warfarin isomers studied and a mechanism by which warfarin permeates through membranes in vivo is presented. ReferencesLandefeld, C.; Beyth, R. Am. J. Med. 1993, 95, 315-328.Karlsson, B. C. G.; Rosengren, A. M.; Andersson, P. O.; Nicholls, I. A. J. Phys. Chem. B 2007, 111, 10520-10528.Karlsson, B. C. G.; Rosengren, A. M.; Andersson, P. O.; Nicholls, I. A. J. Phys. Chem. B 2009, 113, 7945-7949.Karlsson, B. C. G.; Rosengren, A. M.; Näslund, I.; Andersson, P. O.; Nicholls, I. A. Submitted 2010.Rosengren, A. M.; Karlsson, B. C. G.; Näslund, I.; Andersson, P. O.; Nicholls, I. A. Submitted 2010.Nicholls, I. A.; Karlsson, B. C. G.; Rosengren, A. M.; Henschel, H. J. Mol. Recognit. 2010, In press.Henschel, H.; Karlsson, B. C. G.; Rosengren, A. M.; Nicholls, I. A. Submitted 2010.
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