| 1. |
- Ausili, A., et al.
(author)
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Quartz crystal microbalance with dissipation monitoring and the real-time study of biological systems and macromolecules at interfaces
- 2012
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In: Biomedical Spectroscopy and Imaging. - 2212-8794 .- 2212-8808. ; 1:4, s. 325-338
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Journal article (peer-reviewed)abstract
- QCM-D technique is based on the physical phenomenon that generates an acoustic shear wave with an oscillating resonance in quartz resulting in an evanescent wave that arises at the interface of the quartz and the solution. The amplitude of the acoustic wave is influenced by the deposition of material onto the quartz surface and from the subsequent decrease of the frequency the bound mass can be calculated. The dissipation shift which arises inform about viscoelasticity and flexibility of the adsorbed material. QCM-D can be applied for real-time studies of several biological systems since it is a simple, fast, low-cost and sensitive technique without having to label any sample. Common applications in biological field include measurements on adsorption of lipids, proteins, DNA and cells directly onto the surface of the sensor, which generally are chemically modified by self-assembled monolayer (SAM) technique or by spin-coated polymers. QCM-D can also be used to study molecular interactions between macromolecules and adsorbed materials. Three examples of the use of this technique are presented, namely the docking orientation of the C2 domain of PKCε on phospholipid membranes, the conformational changes of fibrinogen adsorbed to model acrylic polymers and the attachment of endothelial cells to carboxylated polymers of different configuration.
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| 2. |
- Barth, Andreas
(author)
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Two sides of the same coin : How enzymes distort substrates and vice versa. An infrared spectroscopic view on pyruvate kinase and Ca2+-ATPase
- 2016
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In: Biomedical Spectroscopy and Imaging. - 2212-8794. ; 5:2, s. 101-114
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Journal article (peer-reviewed)abstract
- This review summarises our infrared spectroscopy and density functional theory studies on the mutual interactions between enzymes and their substrates. We investigated phosphoenolpyruvate bound to pyruvate kinase (EC 2.7.1.40, M1 isozyme), ATP bound to the Ca2+-ATPase (SERCA1a), and the aspartylphosphate moiety of the Ca2+-ATPase phosphoenzyme E2P. Conformational changes of the enzymes and distortions of substrate structure are discussed. In all cases, the infrared absorption of the substrate in the enzyme environment could be identified by a combination of reaction-induced difference spectroscopy and isotopic labelling. The experimentally-determined vibrational frequencies were interpreted in structural terms using experimental correlations or modelling of the active site in density functional theory calculations. For none of the three systems, a weakening of the bond that is cleaved in the following enzymatic reaction could be detected in the ground state of the enzyme-substrate complex. However, for the dephosphorylation reaction of the Ca2+-ATPase phosphoenzyme E2P, a high energy intermediate, not detected in experiments, is the reactant state according to density functional theory calculations.
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| 3. |
- Härmark, Johan, et al.
(author)
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Investigation of the elimination process of a multimodal polymer-shelled contrast agent in rats using ultrasound and transmission electron microscopy
- 2015
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In: Biomedical Spectroscopy and Imaging. - 2212-8794. ; 4:1, s. 81-93
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Journal article (peer-reviewed)abstract
- BACKGROUND: A novel polymer-shelled contrast agent (CA) with multimodal imaging and target specific potential was developed recently and tested for its acoustical properties using different in-vitro setups.OBJECTIVE: The aim of this study was to investigate the elimination of three types of the novel polymer-shelled CA, one unmodified and two shell modified versions, in rats.METHODS: The blood elimination time was estimated by measuring the image intensity, from ultrasound images of the common carotid artery, over time after a bolus injection of the three types of the novel CA. The commercially available CA SonoVue was used as a reference. The subcellular localization of the three CAs was investigated using transmission electron microscopy.RESULTS: The ultrasound measurements indicated a blood half-life of 17–85 s for the different types of the novel CA, which was significant longer than the blood half-life time for SonoVue. Additionally, CAs were exclusively found in the circulatory system, either taken up by, or found in the vicinity of macrophages.CONCLUSIONS: Compared to the commercially available CA SonoVue, the blood circulation times for the three types of the novel polymer-shelled CA were prolonged. Moreover, macrophages were suggested to be responsible for the elimination of the CA.
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