Kai Johnsson
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View article: SiR‐XActin: A Fluorescent Probe for Imaging Actin Dynamics in Live Cells
SiR‐XActin: A Fluorescent Probe for Imaging Actin Dynamics in Live Cells Open
Imaging actin‐dependent processes in live cells is important for understanding numerous biological processes. However, currently used natural‐product‐based fluorescent probes for actin filaments affect the dynamics of actin polymerization …
View article: SiR‐XActin: A Fluorescent Probe for Imaging Actin Dynamics in Live Cells
SiR‐XActin: A Fluorescent Probe for Imaging Actin Dynamics in Live Cells Open
Imaging actin‐dependent processes in live cells is important for understanding numerous biological processes. However, currently used natural‐product‐based fluorescent probes for actin filaments affect the dynamics of actin polymerization …
View article: Real-life application of a point-of-care biosensor for phenylalanine in patients with phenylketonuria
Real-life application of a point-of-care biosensor for phenylalanine in patients with phenylketonuria Open
Phenylketonuria (PKU) is a rare metabolic disorder characterized by elevated phenylalanine (PHE) levels, requiring lifelong dietary management and regular monitoring. Current PHE monitoring methods, such as tandem mass spectrometry (FIA-MS…
View article: Molecular recording of cellular protein kinase activity with chemical labeling
Molecular recording of cellular protein kinase activity with chemical labeling Open
Protein kinases control most cellular processes and aberrant kinase activity is involved in numerous diseases. Here we introduce molecular recorders of kinase activities for later analysis to investigate the link between specific kinase ac…
View article: Fast, Bright and Reversible Rhodamine Tags for Live-Cell Imaging
Fast, Bright and Reversible Rhodamine Tags for Live-Cell Imaging Open
We present Rho-tag and SiR-tag, engineered protein tags derived from bacterial multidrug-resistance proteins that bind unsubstituted (silicon-) rhodamines with nanomolar affinity, enabling fast, reversible, and fluorogenic protein labeling…
View article: A high-affinity split-HaloTag for live-cell protein labeling
A high-affinity split-HaloTag for live-cell protein labeling Open
We introduce a high-affinity split-HaloTag comprised of a short peptide tag (Hpep, 14 residues) and a large, inactive fragment (cpHaloΔ3). Hpep binds to cpHaloΔ3 spontaneously with nanomolar affinity, enabling subsequent labeling with fluo…
View article: Improving split‐ <scp>HaloTag</scp> through computational protein engineering
Improving split‐ <span>HaloTag</span> through computational protein engineering Open
Split‐HaloTag can be used to transform transient molecular interactions into permanent marks through chemical labeling, thereby enabling the recording of transient physiological events in individual cells. However, applications of split‐Ha…
View article: Exploiting Covalent Chemical Labeling with Self-Labeling Proteins
Exploiting Covalent Chemical Labeling with Self-Labeling Proteins Open
The visualization and manipulation of proteins in live cells are critical for studying complex biological processes. Self-labeling proteins do so by enabling the specific and covalent attachment of synthetic probes, offering unprecedented …
View article: A Silicon Rhodamine‐fused Glibenclamide to Label and Detect Malaria‐infected Red Blood Cells
A Silicon Rhodamine‐fused Glibenclamide to Label and Detect Malaria‐infected Red Blood Cells Open
The malaria parasite Plasmodium falciparum affects the lives of millions of people worldwide every year. The detection of replicating parasites within human red blood cells is of paramount importance, requiring appropriate diagnostic tools…
View article: A silicon rhodamine-fused glibenclamide to label and detect malaria-infected red blood cells
A silicon rhodamine-fused glibenclamide to label and detect malaria-infected red blood cells Open
The malaria parasite Plasmodium falciparum affects the lives of millions of people worldwide every year. The detection of replicating parasites within human red blood cells is of paramount importance, requiring appropriate diagnostic tools…
View article: SiR-XActin: A fluorescent probe for imaging actin dynamics in live cells
SiR-XActin: A fluorescent probe for imaging actin dynamics in live cells Open
Imaging actin-dependent processes in live cells is important for understanding numerous biological processes. However, currently used natural-product based fluorescent probes for actin filaments affect the dynamics of actin polymerization …
View article: Chemigenetic Ca2+ indicators report elevated Ca2+ levels in endothelial Weibel-Palade bodies
Chemigenetic Ca2+ indicators report elevated Ca2+ levels in endothelial Weibel-Palade bodies Open
Weibel-Palade bodies (WPB) are secretory organelles exclusively found in endothelial cells and among other cargo proteins, contain the hemostatic von-Willebrand factor (VWF). Stimulation of endothelial cells results in exocytosis of WPB an…
View article: <i>In vivo</i>multiplex imaging of dynamic neurochemical networks with designed far-red dopamine sensors
<i>In vivo</i>multiplex imaging of dynamic neurochemical networks with designed far-red dopamine sensors Open
Neurochemical signals like dopamine (DA) play a crucial role in a variety of brain functions through intricate interactions with other neuromodulators and intracellular signaling pathways. However, studying these complex networks has been …
View article: Long‐Term Single‐Molecule Tracking in Living Cells using Weak‐Affinity Protein Labeling
Long‐Term Single‐Molecule Tracking in Living Cells using Weak‐Affinity Protein Labeling Open
Single‐particle tracking (SPT) has become a powerful tool to monitor the dynamics of membrane proteins in living cells. However, permanent labeling strategies for SPT suffer from photobleaching as a major limitation, restricting observatio…
View article: Long‐Term Single‐Molecule Tracking in Living Cells using Weak‐Affinity Protein Labeling
Long‐Term Single‐Molecule Tracking in Living Cells using Weak‐Affinity Protein Labeling Open
Single‐particle tracking (SPT) has become a powerful tool to monitor the dynamics of membrane proteins in living cells. However, permanent labeling strategies for SPT suffer from photobleaching as a major limitation, restricting observatio…
View article: Improving Split-HaloTag through Computational Protein Engineering
Improving Split-HaloTag through Computational Protein Engineering Open
Split-HaloTag can be used to transform transient molecular interactions into permanent marks through chemical labeling, thereby enabling the recording of transient physiological events in individual cells. However, applications of split-Ha…
View article: Gentle Rhodamines for Live-Cell Fluorescence Microscopy
Gentle Rhodamines for Live-Cell Fluorescence Microscopy Open
Rhodamines have been continuously optimized in brightness, biocompatibility, and color to fulfill the demands of modern bioimaging. However, the problem of phototoxicity caused by the excited fluorophore under long-term illumination has be…
View article: Molecular recording of cellular protein kinase activity with chemical labeling
Molecular recording of cellular protein kinase activity with chemical labeling Open
Protein kinases control most cellular processes and aberrant kinase activity is involved in numerous diseases. To investigate the link between specific kinase activities and cellular phenotypes in heterogeneous cell populations and in vivo…
View article: SNAP-tag2: faster and brighter protein labeling
SNAP-tag2: faster and brighter protein labeling Open
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 it…
View article: Long-term single-molecule tracking in living cells using weak-affinity protein labeling
Long-term single-molecule tracking in living cells using weak-affinity protein labeling Open
Single-particle tracking (SPT) has become a powerful tool to monitor the dynamics of membrane proteins in living cells. However, permanent labeling strategies for SPT suffer from photobleaching as a major limitation, restricting observatio…
View article: AspSnFR: A genetically encoded biosensor for real-time monitoring of aspartate in live cells
AspSnFR: A genetically encoded biosensor for real-time monitoring of aspartate in live cells Open
Aspartate is crucial for nucleotide synthesis, ammonia detoxification, and maintaining redox balance via the malate-aspartate-shuttle (MAS). To disentangle these multiple roles of aspartate metabolism, tools are required that measure aspar…
View article: Purification of time-resolved insulin granules reveals proteomic and lipidomic changes during granule aging
Purification of time-resolved insulin granules reveals proteomic and lipidomic changes during granule aging Open
Endocrine cells employ regulated exocytosis of secretory granules to secrete hormones and neurotransmitters. Secretory granule exocytosis depends on spatiotemporal variables such as proximity to the plasma membrane and age, with newly gene…
View article: Recording physiological history of cells with chemical labeling
Recording physiological history of cells with chemical labeling Open
Recordings of the physiological history of cells provide insights into biological processes, yet obtaining such recordings is a challenge. To address this, we introduce a method to record transient cellular events for later analysis. We de…
View article: Gentle rhodamines for live-cell fluorescence microscopy
Gentle rhodamines for live-cell fluorescence microscopy Open
Rhodamines have been continuously optimized in brightness, biocompatibility, and colors to fulfill the demands of modern bioimaging. However, the problem of phototoxicity caused by the excited fluorophore under long-term illumination has b…
View article: Metal-free introduction of primary sulfonamide into electron-rich aromatics
Metal-free introduction of primary sulfonamide into electron-rich aromatics Open
Inspired by the Burgess reagent, we report a mild and practical synthesis of primary sulfonamides from electron-rich aromatic compounds by using in situ formed N -sulfonylamine as the electrophile.
View article: Neural network-assisted single-molecule localization microscopy with a weak-affinity protein tag
Neural network-assisted single-molecule localization microscopy with a weak-affinity protein tag Open
Single-molecule localization microscopy achieves nanometer spatial resolution by localizing single fluorophores separated in space and time. A major challenge of single-molecule localization microscopy is the long acquisition time, leading…
View article: Absence of mitochondrial SLC25A51 enhances PARP1-dependent DNA repair by increasing nuclear NAD+ levels
Absence of mitochondrial SLC25A51 enhances PARP1-dependent DNA repair by increasing nuclear NAD+ levels Open
Though the effect of the recently identified mitochondrial NAD+ transporter SLC25A51 on glucose metabolism has been described, its contribution to other NAD+-dependent processes throughout the cell such as ADP-ribosylation remains elusive.…
View article: Chemical Probe for Imaging of Polo-like Kinase 4 and Centrioles
Chemical Probe for Imaging of Polo-like Kinase 4 and Centrioles Open
Polo-like kinase (Plk4) is a serine/threonine-protein kinase that is essential for biogenesis of the centriole organelle and is enriched at centrioles. Herein, we introduce Cen-TCO, a chemical probe based on the Plk4 inhibitor centrinone, …