| 1. |
- Torres, Nuria Albet, et al.
(författare)
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Drug effect unveils inter-head cooperativity and strain-dependent ADP release in fast skeletal actomyosin
- 2009
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Ingår i: Journal of Biological Chemistry. - 0021-9258 .- 1083-351X. ; 284:34, s. 22926-22937
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Tidskriftsartikel (refereegranskat)abstract
- Amrinone is a bipyridine compound with characteristic effects on the force-velocity relationship of fast skeletal muscle, including a reduction in the maximum shortening velocity and increased maximum isometric force. Here we performed experiments to elucidate the molecular mechanisms for these effects, with the additional aim to gain insight into the molecular mechanisms underlying the force-velocity relationship. In vitro motility assays established that amrinone reduces the sliding velocity of heavy meromyosin-propelled actin filaments by 30% at different ionic strengths of the assay solution. Stopped-flow studies of myofibrils, heavy meromyosin and myosin subfragment 1, showed that the effects on sliding speed were not because of a reduced rate of ATP-induced actomyosin dissociation because the rate of this process was increased by amrinone. Moreover, optical tweezers studies could not detect any amrinone-induced changes in the working stroke length. In contrast, the ADP affinity of acto-heavy meromyosin was increased about 2-fold by 1 mM amrinone. Similar effects were not observed for acto-subfragment 1. Together with the other findings, this suggests that the amrinone-induced reduction in sliding velocity is attributed to inhibition of a strain-dependent ADP release step. Modeling results show that such an effect may account for the amrinone-induced changes of the force-velocity relationship. The data emphasize the importance of the rate of a strain-dependent ADP release step in influencing the maximum sliding velocity in fast skeletal muscle. The data also lead us to discuss the possible importance of cooperative interactions between the two myosin heads in muscle contraction.
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| 2. |
- Boventi, Matteo, et al.
(författare)
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Porosity of Molecularly Imprinted Polymers Investigated by 129Xe NMR Spectroscopy
- 2022
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Ingår i: ACS Applied Polymer Materials. - : American Chemical Society (ACS). - 2637-6105. ; 4:12, s. 8740-8749
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Tidskriftsartikel (refereegranskat)abstract
- Molecularly imprinted polymers (MIPs) display intriguing recognition properties and can be used as sensor recognition elements or in separation. In this work, we investigated the formation of hierarchical porosity of compositionally varied MIPs using 129Xe Nuclear Magnetic Resonance (NMR) and 1H Time Domain Nuclear Magnetic Resonance (TD-NMR). Variable temperature 129Xe NMR established the morphological variation with respect to the degree of cross-linking, supported by 1H TDNMR determination of polymer chain mobility. Together, the results indicate that a high degree of cross-linking stabilizes the porous structure: highly cross-linked samples display a significant amount of accessible mesopores that instead collapse in less structured polymers. No significant differences can be detected due to the presence of templated pores in molecularly imprinted polymers: in the dry state, these specific shapes are too small to accommodate xenon atoms, which, instead, probe higher levels in the porous structure, allowing their study in detail. Additional resonances at a high chemical shift are detected in the 129Xe NMR spectra. Even though their chemical shifts are compatible with xenon dissolved in bulk polymers, variable temperature experiments rule out this possibility. The combination of 129Xe and TDNMR data allows attribution of these resonances to softer superficial regions probed by xenon in the NMR time scale. This can contribute to the understanding of the surface dynamics of polymers.
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| 3. |
- Golker, Kerstin, et al.
(författare)
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A Functional Monomer Is Not Enough : Principal Component Analysis of the Influence of Template Complexation in Pre-Polymerization Mixtures on Imprinted Polymer Recognition and Morphology
- 2014
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Ingår i: International Journal of Molecular Sciences. - : MDPI AG. - 1661-6596 .- 1422-0067. ; 15:11, s. 20572-20584
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Tidskriftsartikel (refereegranskat)abstract
- In this report, principal component analysis (PCA) has been used to explore the influence of template complexation in the pre-polymerization phase on template molecularly imprinted polymer (MIP) recognition and polymer morphology. A series of 16 bupivacaine MIPs were studied. The ethylene glycol dimethacrylate (EGDMA)-crosslinked polymers had either methacrylic acid (MAA) or methyl methacrylate (MMA) as the functional monomer, and the stoichiometry between template, functional monomer and crosslinker was varied. The polymers were characterized using radioligand equilibrium binding experiments, gas sorption measurements, swelling studies and data extracted from molecular dynamics (MD) simulations of all-component pre-polymerization mixtures. The molar fraction of the functional monomer in the MAA-polymers contributed to describing both the binding, surface area and pore volume. Interestingly, weak positive correlations between the swelling behavior and the rebinding characteristics of the MAA-MIPs were exposed. Polymers prepared with MMA as a functional monomer and a polymer prepared with only EGDMA were found to share the same characteristics, such as poor rebinding capacities, as well as similar surface area and pore volume, independent of the molar fraction MMA used in synthesis. The use of PCA for interpreting relationships between MD-derived descriptions of events in the pre-polymerization mixture, recognition properties and morphologies of the corresponding polymers illustrates the potential of PCA as a tool for better understanding these complex materials and for their rational design.
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| 4. |
- Golker, Kerstin, 1969-
(författare)
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Fundamental Studies on Molecularly Imprinted Materials
- 2014
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The thesis focuses on fundamental studies aimed at elucidating factors that influence molecularly imprinted polymer (MIP) formation and ligand recognition. To this end, a series of computational techniques, in particular chemometrics and molecular dynamics (MD) in conjunction with polymer synthesis and physical characterization studies have been employed. In Paper I, the multivariate analysis method principal component analysis (PCA) was used to investigate the role of incubation media on polymer-ligand recognition, and results highlighted the importance of several solvent parameters on recognition. In Paper II, all-component MD simulations were used to examine the role of polymerization mixture stoichiometry on MIP-template recognition. Correlations between nature and extent of template complexation and recognition were observed. The influence of the acidic functionality of the methacrylic acid used in these polymers on polymer-template recognition and morphology was examined in Paper III. PCA was then used in Paper IV to identify relationships between interactions in the pre-polymerization mixture, polymer functionality, recognition and morphology using the polymers described in Paper II and III.
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| 5. |
- Golker, Kerstin, et al.
(författare)
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Hydrogen bond diversity in the pre-polymerization stage contributes to morphology and MIP-template recognition - MAA versus MMA
- 2015
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Ingår i: European Polymer Journal. - : Elsevier BV. - 0014-3057 .- 1873-1945. ; 66, s. 558-568
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Tidskriftsartikel (refereegranskat)abstract
- This report demonstrates that the diversity of hydrogen bond interactions present in molecularly imprinted polymer pre-polymerization mixtures, typically associated with binding-site heterogeneity, can also contribute to morphological characteristics that may influence polymer-template recognition. Comparisons have been made between a series of bupivacaine molecularly imprinted methacrylic acid (MAA)-ethylene glycol dimethacrylate (EGDMA) copolymers and a series of analogous methyl methacrylate (MMA)-EGDMA copolymers using comprehensive molecular dynamics studies of the respective pre-polymerization mixtures, template-polymer binding studies and detailed BET surface area and BJH porosity analyses. The role of the carboxylic acid functionality of MAA, and in particular the acidic proton, in generating morphological features conducive to analyte access (slit-like rather than ink bottle-like structures) and recognition is discussed.
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| 6. |
- 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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| 7. |
- Golker, Kerstin, et al.
(författare)
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The effect of crosslinking density on molecularly imprinted polymer morphology and recognition
- 2016
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Ingår i: European Polymer Journal. - : Elsevier BV. - 0014-3057 .- 1873-1945. ; 75, s. 423-430
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Tidskriftsartikel (refereegranskat)abstract
- In this report, the crosslinking density of bupivacaine molecularly imprinted methacrylic acid (MAA)-ethylene glycol dimethacrylate (EGDMA) copolymers was investigated through replacement of EGDMA by methyl methacrylate (MMA). The effects were examined using a series of full-scale MD simulations of pre-polymerization mixtures, equilibrium rebinding studies on the corresponding synthesized polymers and morphology characterization through nitrogen sorption measurements. While the extent of hydrogen bonding between the functional monomer MAA and bupivacaine observed in the MD pre-polymerization mixtures was comparable in each of the systems studied, the decrease in degree of crosslinking impacted directly on polymer morphology as observed in BET and BJH studies of surface area and porosity. Further, decreases in the crosslinking density induced reductions in template rebinding capacity as seen from a series of radio-ligand binding studies, demonstrating the importance of crosslinking on the performance of molecularly imprinted MAA-EGDMA copolymers, the polymer system most commonly used in molecular imprinting science and technology. (C) 2016 Elsevier Ltd. All rights reserved.
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| 8. |
- 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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| 9. |
- 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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| 10. |
- 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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