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Kai Johnsson

Cette personne a quitté l’EPFL

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Publications associées (122)

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A Fluorescent Sensor for GABA and Synthetic GABA(B) Receptor Ligands

Kai Johnsson, Luc Reymond, Anastasiya Masharina

While gamma-aminobutyric acid (GABA) is the main inhibitory neurotransmitter, suitable tools to measure its concentration in living cells with high spatiotemporal resolution are missing. Herein, we describe the first ratiometric fluorescent sensor for GABA ...

American Chemical Society2012

Posttranslational covalent labeling reveals heterogeneous mobility of individual G protein-coupled receptors in living cells

Horst Arthur Vogel, Kai Johnsson, Jean-Manuel Segura, Nathalie George, Bruno Meyer

2006

Protein tag-mediated conjugation of oligonucleotides to recombinant affinity binders for proximity ligation

Kai Johnsson

While antibodies currently play a dominant role as affinity reagents in biological research and for diagnostics, a broad range of recombinant proteins are emerging as promising alternative affinity reagents in detection assays and quantification. DNA-media ...

Elsevier2013

Tetrahydrobiopterin Biosynthesis as a Potential Target of the Kynurenine Pathway Metabolite Xanthurenic Acid

Kai Johnsson, Rudolf Hovius, Miriam Grønlund Pedersen, Hirohito Haruki

Tryptophan metabolites in the kynurenine pathway are up-regulated by pro-inflammatory cytokines or glucocorticoids, and are linked to anti-inflammatory and immunosuppressive activities. In addition, they are up-regulated in pathologies such as cancer, auto ...

Amer Soc Biochemistry Molecular Biology Inc2015

Bioluminescent Antibodies for Point-of-Care Diagnostics

Kai Johnsson, Rudolf Griss, Alberto Schena, Qiuliyang Yu, Lin Xue

We introduce a general method to transform antibodies into ratiometric, bioluminescent sensor proteins for the no-wash quantification of analytes. Our approach is based on the genetic fusion of antibody fragments to NanoLuc luciferase and SNAP-tag, the lat ...

Wiley-VCH Verlag GmbH2017

Protein-Functionalized Polymer Brushes

Harm-Anton Klok, Kai Johnsson, Stefano Tugulu, India Christina Sielaff, Anke Arnold

A new strategy for the prepn. of protein-functionalized polymer brushes is reported, which is based on a combination of surface-initiated atom transfer radical polymn. (ATRP), p-nitrophenyl chloroformate activation of the surface hydroxyl groups, and subse ...

American Chemical Society2005

SNAP-tag2 for faster and brighter protein labeling

Kai Johnsson

SNAP-tag is a powerful tool for labeling proteins with synthetic fluorophores in bioimaging. However, its utility in live-cell applications can be constrained by its relatively slow labeling kinetics and the limited cell permeability of its substrates. Her ...

2025

Protein-functionalized polymer brushes

Harm-Anton Klok, Kai Johnsson, Stefano Tugulu, India Christina Sielaff, Anke Arnold

Understanding and controlling the interactions between synthetic and biol. materials is of great importance for the development of novel materials for a variety of biomedical and bioanal. applications, including for example stents, vascular grafts and prot ...

2005

Selective Chemical Crosslinking Reveals a Cep57-Cep63-Cep152 Centrosomal Complex

Kai Johnsson, Pierre Gönczy, Luc Reymond, Grazvydas Lukinavicius

The centrosome functions as the main microtubule-organizing center of animal cells and is crucial for several fundamental cellular processes [1]. Abnormalities in centrosome number and composition correlate with tumor progression [2, 3] and other diseases ...

Elsevier2013

Semisynthesis of fluorescent metabolite sensors on cell surfaces

Horst Arthur Vogel, Kai Johnsson, Luc Reymond, Rudolf Griss, Joachim Piguet, Matthias Albert Brun, Kui Thong Tan

Progress in understanding signal transduction and metabolic pathways is hampered by a shortage of suitable sensors for tracking metabolites, second messengers, and neurotransmitters in living cells. Here we introduce a class of rationally designed semisynt ...

2011

Activatable fluorescent probes for hydrolase enzymes based on coumarin-hemicyanine hybrid fluorophores with large Stokes shifts

Kai Johnsson

We show that the equilibrium of intramolecular spirocyclization of coumarin-hemicyanine hybrid fluorophores can be finely tuned by means of chemical modifications. We used this scaffold to develop activatable fluorescent probes with large Stokes shifts for ...

Royal Society of Chemistry2020

Engineering substrate specificity of O6-alkylguanine-DNA alkyltransferase for specific protein labeling in living cells

Kai Johnsson, Christian Heinis, Alexandre Juillerat, India Christina Sielaff, Béatrice Kunz, Hugues Jaccard

Fusion proteins of human O6-alkylguanine-DNA alkyltransferase (AGT) can be specifically labeled with a wide variety of synthetic probes in mammalian cells; this makes them an attractive tool for studying protein function. However, to avoid undesired labeli ...

2005

Acetylated tubulin is essential for touch sensation in mice

Kai Johnsson, Luc Reymond, Antonino Asaro

At its most fundamental level, touch sensation requires the translation of mechanical energy into mechanosensitive ion channel opening, thereby generating electro-chemical signals. Our understanding of this process, especially how the cytoskeleton influenc ...

Elife Sciences Publications Ltd2016

Kinetic and Structural Characterization of the Self-Labeling Protein Tags HaloTag7, SNAP-tag, and CLIP-tag

Kai Johnsson, Julien Hiblot, Iuliia Karpenko

The self-labeling protein tags (SLPs) HaloTag7, SNAP-tag, and CLIP-tag allow the covalent labeling of fusion proteins with synthetic molecules for applications in bioimaging and biotechnology. To guide the selection of an SLP-substrate pair and provide gui ...

AMER CHEMICAL SOC2021

Protein chemistry on the surface of living cells

Kai Johnsson, Nathalie George

A review. The interplay between carbohydrates, lipids, and proteins dets. the stability and flexibility as well as the adhesive and responsive features of the surfaces of all cells. The mol. understanding of the interactions among and between the different ...

2005

Semisynthetic fluorescent sensor proteins based on self-labeling protein tags

Kai Johnsson, Matthias Albert Brun, Marlon Hinner, Kui Thong Tan

Genetically encoded fluorescent sensor proteins offer the possibility to probe the concentration of key metabolites in living cells. The approaches currently used to generate Such fluorescent sensor proteins lack. generality, as they require a protein that ...

2009

Chemogenetic Control of Nanobodies

Kai Johnsson, Julien Hiblot, Helen Rebecca Ostlund Farrants

Engineered nanobody allows reversible control of activity in cells through the binding of small molecules. ...

NATURE PUBLISHING GROUP2020

Photobleaching-free infrared near-field microscopy localizes molecules in neurons

Giorgio Margaritondo, Kai Johnsson, Harald Hirling, Johanna Generosi

High-resolution detection of specific molecules in cells is a major challenge in biology. We show that infrared scanning near-field microscopy can detect the spatial distribution of alpha-amino-3-hydroxy-5-methyl-4-isoxazole-propionic acid–type glutamate r ...

2008

Fast directed evolution of non-immunoglobulin proteins by somatic hypermutation in immune cells

Kai Johnsson, Christian Heinis

A review. New, improved phenotypes. Somatic hypermutation in immune cells can be used for the fast directed evolution of proteins other than Igs (e.g., autofluorescent proteins). The target gene is inserted into the genome of activated B lymphocytes where ...

2005

Cell permeable, fluorescent dye

Kai Johnsson, Grazvydas Lukinavicius

The invention pertains to a near-infrared fluorescent dye that is cell permeable and can be attached to selected proteins in living cells. The dye has the general formula (I) or its or its corresponding spirolactone (II) wherein Y is chosen from the group ...

2013