Publications by Kai Johnsson | EPFL Graph Search

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Cell-permeable DNA stains are popular markers in live-cell imaging. Currently used DNA stains for live-cell imaging are either toxic, require illumination with blue light or are not compatible with super-resolution microscopy, thereby limiting their utilit ...

Fluorescent protein reporters have become the mainstay for tracing cellular circuitry in vivo but are limited in their versatility. Here we generated Cre-dependent reporter mice expressing the Snap-tag to target synthetic indicators to cells. Snap-tag labe ...

Infrared scanning near-field optical microscopy is used to detect AMPA-type glutamate receptor clusters in hippocampal neuron cells. AMPA's GluR2-subunits were marked with the fluorophore Alexa488 and high-resolution micrographs were taken at 6.25 µm wavel ...

The present invention relates to methods of transferring a label from novel substrates to O-alkylguanine-DNA alkyltransferases (AGT) and O-alkylguanine-DNA alkyltransferase fusion proteins, and to novel substrates suitable in such methods. Proteins of interest are incorporated into an AGT fusion protein, the AGT fusion protein is contacted with particular AGT substrates carrying a label, and the AGT fusion protein is detected and optionally further manipulated using the label in a system designed for

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 flexibility in th ...

The introduction of sulfa drugs for the chemotherapy of bacterial infections in 1935 revolutionized medicine. Although their mechanism of action is understood, the molecular bases for most of their side effects remain obscure. Here, we report that sulfamet ...

We report herein a direct and practical synthesis of arylsulfonamides from electron-rich aromatic compounds by using in situ generated N-sulfonylamine as the active electrophile. Substrates include derivatives of aniline, indole, pyrrole, furan, styrene an ...

A review, with 30 refs., on enzymes designed to catalyze chem. reactions and their folded conformations. [on SciFinder (R)]

Benzothiazinones (BTZs) are antituberculosis drug candidates with nanomolar bactericidal activity against tubercle bacilli. Here we demonstrate that BTZs are suicide substrates of the FAD-dependent decaprenylphosphoryl-beta-D-ribofuranose 2'-oxidase DprE1, an enzyme involved in cell-wall biogenesis. BTZs are reduced by DprE1 to an electrophile, which then reacts in a near-quantitative manner with an active-site cysteine of DprE1, thus providing a rationale for the extraordinary potency of BTZs. Mutant DprE1

Funded by the Swiss National Science Foundation to promote cutting edge research as well as the advancement of young researchers and women, technology transfer, outreach and education, the NCCR (Swiss National Centre of Competence in Research) Chemical Bio ...

HaloTag variants offer distinct brightness and fluorescence lifetimes compared with HaloTag7 when labeled with rhodamines. These variants were used for multiplexed imaging with a single fluorophore and to create lifetime-based cell cycle indicators. ...

The inactivation of the enoyl-reductase InhA from Mycobacterium tuberculosis by reactive intermediates formed during the oxidn. of isoniazid and ethionamide was studied. Both drugs can generate electrophilic intermediates capable of reacting with a nucleophilic group of InhA, leading to its inactivation. After inactivation of InhA by isoniazid, one mol. of isoniazid per InhA is covalently bound to the enzyme. Mapping studies suggest that Cys243 is the residue modified in the course of the inactivation. [on

There is an urgent need to discover new antitubercular agents with novel mechanisms of action in order to tackle the scourge of drug-resistant tuberculosis. Here, we report the identification of such a molecule - an AminoPYrimidine-Sulfonamide (APYS1) that ...

We are introducing a new approach to evaluate cellular uptake of drugs and drug candidates into living cells. The approach is based on converting the protein target of a given class of compounds into a fluorescent biosensor. By measuring the binding of dif ...

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-HaloTag-based recor ...

The authors report on a method for the multicolor imaging of cell surface proteins which is based on the labeling of carrier protein (CP) fusion proteins with different fluorophores. In one application, different generations of a cell surface protein can b ...

The invention relates to substrates for O-alkylguanine-DNA alkyltransferases (AGT) of formula R1-A-X-CH2-R3-R4-L1, wherein A is a group recognized by AGT as a substrate, X is oxygen or sulfur, R1 is a group -R2-L2 or a group R5, R2 and R4 are, independe ...

Labeling proteins with synthetic probes is important for studying and characterizing protein function. We have recently introduced a general method for the specific in vivo and in vitro labeling of fusion proteins that is based on the reaction of O6-alkylguanine-DNA alkyltransferase (AGT) with O6-benzylguanine derivs. Here we report two complementary routes for the synthesis of O6-benzylguanine derivs., which allow for the labeling of AGT fusion proteins with bifunctional synthetic probes and demonstrate th

A general method for the covalent immobilization of fusion proteins is presented. The approach is based on the unusual mechanism of the human O6-alkylguanine-DNA alkyltransferase, which irreversibly transfers the alkyl group from its substrate, alkylated or benzylated guanine, to a reactive cysteine residue. By attaching the benzyl group to a surface, hAGT fusion proteins immobilize themselves in a specific and covalent manner. The specificity of the reaction of hAGT with its substrate even allows the speci

Formation of a triple helix between an oligodeoxyribonucleotide contg. 8-oxo-2'-deoxyadenosine and a DNA duplex target was studied as a function of pH. Above pH 7.4, the triple helix with the 8-oxo-2'-deoxyadenosine was more stable than the complex with an analogous oligodeoxyribonucleotide contg. deoxycytidine instead of 8-oxo-2'-deoxyadenosine.

Kai Johnsson

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SiR–Hoechst is a far-red DNA stain for live-cell nanoscopy

Genetic targeting of chemical indicators in vivo

AMPA receptor imaging by infrared scanning near-field optical microscopy

Substrates for o-alkylguanine-dna alkyltransferase

Exploiting Covalent Chemical Labeling with Self-Labeling Proteins

Tetrahydrobiopterin Biosynthesis as an Off-Target of Sulfa Drugs

Metal-free introduction of primary sulfonamide into electron-rich aromatics

Designed enzymes: new peptides that fold in aqueous solution and catalyze reactions

Benzothiazinones Are Suicide Inhibitors of Mycobacterial Decaprenylphosphoryl-β-

NCCR Chemical Biology: Interdisciplinary Research Excellence, Outreach, Education, and New Tools for Switzerland

Engineered HaloTag variants for fluorescence lifetime multiplexing

Studies on the Mechanism of Action of Isoniazid and Ethionamide in the Chemotherapy of Tuberculosis

Identification of aminopyrimidine-sulfonamides as potent modulators of Wag31-mediated cell elongation in mycobacteria

Evaluating Cellular Drug Uptake with Fluorescent Sensor Proteins

Improving split-HaloTag through computational protein engineering

Multicolor Imaging of Cell Surface Proteins

Specific substrates for O6- alkylguanine-DNA alkyltransferase

Synthesis and characterization of bifunctional probes for the specific labeling of fusion proteins

Covalent and selective immobilization of fusion proteins

Triple helix binding of oligodeoxyribonucleotides containing 8-oxo-2'-deoxyadenosine