| 1. |
- Apell, Peter, 1952, et al.
(författare)
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Body mass index - a physics perspective
- 2011
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Ingår i: arXiv.
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Almost two centuries ago Adolphe Quetelet came up with an index to characterize man which is frequently used today to make predictions about health status. We show that this so called body mass index is directly related to the ratio between the physical quantities metabolic rate and heat loss
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| 2. |
- Jumeaux, Coline, et al.
(författare)
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MicroRNA Detection by DNA-Mediated Liposome Fusion
- 2018
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Ingår i: ChemBioChem. - : Wiley. - 1439-7633 .- 1439-4227. ; 19:5, s. 434-438
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Tidskriftsartikel (refereegranskat)abstract
- Membrane fusion is a process of fundamental importance in biological systems that involves highly selective recognition mechanisms for the trafficking of molecular and ionic cargos. Mimicking natural membrane fusion mechanisms for the purpose of biosensor development holds great potential for amplified detection because relatively few highly discriminating targets lead to fusion and an accompanied engagement of a large payload of signal-generating molecules. In this work, sequence-specific DNA-mediated liposome fusion is used for the highly selective detection of microRNA. The detection of miR-29a, a known flu biomarker, is demonstrated down to 18 nm within 30 min with high specificity by using a standard laboratory microplate reader. Furthermore, one order of magnitude improvement in the limit of detection is demonstrated by using a novel imaging technique combined with an intensity fluctuation analysis, which is coined two-color fluorescence correlation microscopy.
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| 3. |
- Peerboom, Nadia, 1990, et al.
(författare)
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Binding Kinetics and Lateral Mobility of HSV-1 on End-Grafted Sulfated Glycosaminoglycans
- 2017
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Ingår i: Biophysical Journal. - : Elsevier BV. - 0006-3495 .- 1542-0086. ; 113:6, s. 1223-1234
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Tidskriftsartikel (refereegranskat)abstract
- Many viruses, including herpes simplex (HSV), are recruited to their host cells via interaction between their envelope glycoproteins and cell-surface glycosaminoglycans (GAGs). This initial attachment is of a multivalent nature, i.e., it requires the establishment of multiple bonds between amino acids of viral glycoproteins and sulfated saccharides on the GAG chain. To gain understanding of how this binding process is modulated, we performed binding kinetics and mobility studies using end-grafted GAG chains that mimic the end attachment of these chains to proteoglycans. Total internal reflection fluorescence microscopy was used to probe binding and release, as well as the diffusion of single HSV-1 particles. To verify the hypothesis that the degree of sulfation, but also the arrangement of sulfate groups along the GAG chain, plays a key role in HSV binding, we tested two native GAGs (chondroitin sulfate and heparan sulfate) and compared our results to chemically sulfated hyaluronan. HSV-1 recognized all sulfated GAGs, but not the nonsulfated hyaluronan, indicating that binding is specific to the presence of sulfate groups. Furthermore we observed that a notable fraction of GAG-bound virions exhibit lateral mobility, although the multivalent binding to the immobilized GAG brushes ensures firm virus attachment to the interface. Diffusion was faster on the two native GAGs, one of which, chondroitin sulfate, was also characterized by the highest association rate per GAG chain. This highlights the complexity of multivalent virus-GAG interactions and suggests that the spatial arrangement of sulfates along native GAG chains may play a role in modulating the characteristics of the HSV-GAG interaction. Altogether, these results, obtained with a minimal and well-controlled model of the cell membrane, provide, to our knowledge, new insights into the dynamics of the HSV-GAG interaction.
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| 4. |
- Ulmefors, Hanna, et al.
(författare)
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Formation of Supported Lipid Bilayers Derived from Vesicles of Various Compositional Complexity on Conducting Polymer/Silica Substrates
- 2021
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Ingår i: Langmuir. - : American Chemical Society (ACS). - 0743-7463 .- 1520-5827. ; 37:18, s. 5494-5505
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Tidskriftsartikel (refereegranskat)abstract
- Supported lipid bilayers (SLBs) serve important roles as minimalistic models of cellular membranes in multiple diagnostic and pharmaceutical applications as well as in the strive to gain fundamental insights about their complex biological function. To further expand the utility of SLBs, there is a need to go beyond simple lipid compositions to thereby better mimic the complexity of native cell membranes, while simultaneously retaining their compatibility with a versatile range of analytical platforms. To meet this demand, we have in this work explored SLB formation on PEDOT:PSS/silica nanoparticle composite films and mesoporous silica films, both capable of transporting ions to an underlying conducting PEDOT:PSS film. The SLB formation process was evaluated by using the quartz crystal microbalance with dissipation (QCM-D) monitoring, total internal reflection fluorescence (TIRF) microscopy, and fluorescence recovery after photobleaching (FRAP) for membranes made of pure synthetic lipids with or without the reconstituted membrane protein β-secretase 1 (BACE1) as well as cell-derived native lipid vesicles containing overexpressed BACE1. The mesoporous silica thin film was superior to the PEDOT:PSS/silica nanoparticle composite, providing successful formation of bilayers with high lateral mobility and low defect density even for the most complex native cell membranes.
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| 5. |
- Wahlsten, Olov, 1989
(författare)
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Assay development for studies of G protein-coupled receptors at the single-molecule level
- 2014
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- G protein-coupled receptors (GPCRs), also known as seven transmembrane (7TM) receptors,is the largest family of cell surface receptors. These receptors play a key role in transmittinga wide variety of signals across the cell membrane and are involved in physiologicalprocesses such as sensory transduction, cell-cell communication, neuronal transmission,and hormonal signaling. For this reason the GPCRs are considered as one of the mostpertinent targets for design and development of novel therapeutic compounds, a statementfurther accentuated by the fact that more than half of the therapeutic agents currently onthe market target GPCRs.In this thesis two methods with single molecule sensitivity have been developed for characterizationof biomolecular interactions with transmembrane proteins. Single GPCR sensitivitywas enabled using total internal reflection fluorescence (TIRF) microscopy, withoutlabeling the GPCR, but instead the lipid membrane of the vesicles containing the GPCR.In the first project the interaction between the GPCR CXCR3 and two of its naturalchemokine ligands (CXCL10 and CXCL11) was investigated with the intention to makethe developed assay a complementary tool in drug candidate screening. The chemokineligand (CXCL10) was immobilized on a supported lipid bilayer with polyethylene glycol(PEG) chains to minimize unspecific binding. Vesicles derived from membranes of cellsover-expressing CXCR3 were fluorescently labeled by sonicating them together with syntheticfluorescently labeled vesicles. Addition of these labeled native membrane vesicles tothe functionalized surface enabled characterization of the ligand-receptor interaction viaTIRF mode imaging. Additionally, preliminary results suggest that the method does notrequire over-expression of the GPCR, which is a major advantage for studying this classof sensitive and low-abundant type of membrane proteins. In the second project a colocalizationassay was developed to confirm a specific interaction between a virus particleand a transmembrane protein. The assay is thought to be advantageous due to the facileelimination of unspecific interactions and the possibility to control the number of bindingsites on the surface. These advantages in the context of developing robust, cheap andgeneric assays for future drug discovery are further analyzed and discussed.
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| 6. |
- Wahlsten, Olov, 1989
(författare)
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Development of novel bioanalytical assays with single-molecule readout for biomarker detection and drug candidate characterization
- 2017
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Bioanalytical assays with single-molecule readout for studying molecular interactions have in the past decades received increasing attention. The high sensitivity often offered by this readout scheme has for example enabled ultra-sensitive analyte detection, having important implications for monitoring early disease progression and the effects of drug treatment. In addition, single-molecule studies of molecular interactions with membrane protein receptors have proven useful for the development of new and more effective drugs. Ultra-sensitive detection as well as the possibility to unravel heterogeneities in molecular interactions, offered by single-molecule readout schemes, are both key components for the future of personalized health care and the discovery of new disease biomarkers.This thesis mainly focuses on the development of new bioanalytical assays with single-molecule readout, with the purpose to enable studies of molecular interactions with membrane protein receptors (an important class of drug targets) and to detect diagnostically relevant biomarkers and pathogens. Lipid assemblies, either in the form of liposomes or supported lipid bilayers, have been exploited for their compatibility and flexibility offered in the context of studying many essential biological interactions. In the first part of the thesis, two surface-based assays, both utilizing total internal fluorescence (TIRF) microscopy, were developed to study molecular interactions with a low-abundant and sensitive class of membrane proteins; G protein-coupled receptors (GPCRs). With the insights gained from that work, the focus was shifted towards solution-based detection schemes, based on a home-built dual-color fluorescence microscopy setup. Two detection schemes, based on Förster resonance energy transfer (FRET), for biomarker detection (phospholipase and miRNA), and a third scheme for detection of virus particles via induced colocalization of fluorescent liposomes, were developed.As for future perspectives the thesis puts emphasis on how the different bioanalytical assays can have implications for personalized health care and how the performance of the solution-based colocalization assay can be further improved to become a generic tool for biosensing purposes.
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| 7. |
- Wahlsten, Olov, 1989, et al.
(författare)
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Electrical field landscape of two electroceuticals
- 2016
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Ingår i: Journal of Electrical Bioimpedance. - : Walter de Gruyter GmbH. - 1891-5469. ; 7:1, s. 13-19
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Tidskriftsartikel (refereegranskat)abstract
- In recent years several electrical wound management systems, so called electroceuticals, have been introduced claiming an induced electrical response in the wounded tissue. Some have external current and voltage sources while others have internal constructions aiming at creating necessary therapeutic currents. We investigate two representative electroceuticals by mapping out their electrical field landscapes using a previously developed skin model within a numerical simulation scheme. We find very strong fields from the electroceuticals of the order of 1 kV/m amenable for electrotaxic influence on pertinent cell types for wound healing. Current densities can locally be as high as 1 A/cm2.
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| 8. |
- Wahlsten, Olov, 1989, et al.
(författare)
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Equilibrium-Fluctuation Analysis for Interaction Studies between Natural Ligands and Single G Protein-Coupled Receptors in Native Lipid Vesicles
- 2015
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Ingår i: Langmuir. - : American Chemical Society (ACS). - 1520-5827 .- 0743-7463. ; 31:39, s. 10774-10780
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Tidskriftsartikel (refereegranskat)abstract
- G protein-coupled receptors (GPCRs) constitute the most versatile family of cell-membrane receptors and have been increasingly identified as important mediators of many physiological functions. They also belong to one of the most central drug target classes, but current screening technologies are limited by the requirements of overexpression and stabilization of GPCRs. This calls for sensitivity-increased detection strategies preferably meeting single-molecule detection limits. This challenge is here addressed by employing total internal reflection fluorescence microscopy to characterize the interaction kinetics between CXCR3, a GPCR involved in inflammatory responses, and two of its chemokine ligands, CXCL10 and CXCL11. Fluorescence labeling of the lipid membrane, rather than the membrane protein itself, of GPCR-containing native vesicles, and immobilization of the corresponding ligand on the surface, enabled determination of the interaction kinetics using single-molecule equilibrium-fluctuation analysis. With a limit of detection of GPCR-containing vesicles in the low picomolar concentration regime, the results demonstrate the possibility to use inhibition in solution screening of high affinity ligands/drug candidates, which due to target-binding depletion of the inhibiting compounds is demanding using assays with more moderate detection limits.
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| 9. |
- Wahlsten, Olov, 1989, et al.
(författare)
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Quantitative Detection of Biological Nanoparticles in Solution via Their Mediation of Colocalization of Fluorescent Liposomes
- 2019
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Ingår i: Physical Review Applied. - 2331-7019. ; 12:6
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Tidskriftsartikel (refereegranskat)abstract
- Detection of biomolecules and biological nanoparticles by means of induced aggregation of larger nanoparticles using light scattering as readout was first accomplished in the middle of the last century. Since then, technical advances together with novel nanomaterials have enabled more sophisticated readout schemes, paving the way for methods exploiting dual-probe hybridization for biomolecular or nonoparticle recognition that today can compete with established bioanalytical methods. Herein, we present a quantitative assay, with single-nanoparticle readout, utilizing receptor-containing cell-membrane mimics in the shape of approximately 100-nm lipid liposomes rather than conventional antibody-modified nanoparticles to enable detection of virus particles in solution. Specifically, the method is based on virus-mediated aggregation of differently fluorescent-labeled liposomes that contain the ganglioside GM1 receptor for the Simian Virus 40 (SV40). The aggregation kinetics of the differently colored liposomes is studied by monitoring the spatial colocalization level of the liposomes and a theoretical model that successfully represents aggregation kinetics versus virus concentration is proposed. The limits of detection are identified experimentally for our current setup and theoretically in a more general context. The consistency between theory and experiments suggests that the approach will be generically applicable for similar biosensing applications or for the study of related systems where natural interactions with cell-membrane components can be used to induce liposome aggregation.
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| 10. |
- Wahlsten, Olov, 1989, et al.
(författare)
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Wounds as probes of electrical properties of skin
- 2010
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Ingår i: Journal of Electrical Bioimpedance. - : Walter de Gruyter GmbH. - 1891-5469. ; 1:1, s. 63-70
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Tidskriftsartikel (refereegranskat)abstract
- We have built a model where we use a wound as a probe of the dielectric properties of skin. In this way one is able to infer infor-mation about skin dielectric properties in situ. We introduce the notion of a skin electrochemical capacitor. This gives good agreement with recent measurements for the electric potential landscape around a wound. Possible diagnostic consequences are briefly touched upon.
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