Conjugation of DNA to proteins is increasingly used in academia and industry to provide proteins with tags for identification or handles for hybridization to other DNA strands. Assay technologies such as immuno-PCR and proximity ligation and the imaging technology DNA-PAINT require DNA-protein conjugates. In DNA nanotechnology, the DNA handle is exploited to precisely position proteins by self-assembly. For these applications, site-selective conjugation is almost always desired because fully functional proteins are required to maintain the specificity of antibodies and the activity of enzymes. The introduction of a bioorthogonal handle at a specific position of a protein by recombinant techniques provides an excellent approach to site-specific conjugation, but for many laboratories and for applications where several proteins are to be labeled, the expression of recombinant proteins may be cumbersome. In recent years, a number of chemical methods that target conjugation to specific sites at native proteins have become available, and an overview of these methods is provided in this Account. Our laboratory has investigated DNA-templated protein conjugation (DTPC), which offers an alternative approach to site-selective conjugation of DNA to proteins. The method is inspired by the concept of DNA-templated synthesis where functional groups conjugated to DNA strands are preorganized by DNA hybridization to dramatically increase the reaction rate. In DPTC, we target metal binding sites in proteins to template selective covalent conjugation reactions. By chelation of a DNA-metal complex with a metal binding site of the protein, an electrophile on a second DNA strand is aligned for reaction with a lysine side chain on the protein in the proximity of the metal binding site. The method is quite general because approximately one-third of all wild-type proteins contain metal-binding sites, including many IgG antibodies, and it is also applicable to His-tagged proteins. This emerging field provides direct access to site-selective conjugates of DNA to commercially available proteins. In this Account, we introduce these methods to the reader and describe current developments and future aspects.

Photopharmacology relies on ligands that change their pharmacodynamics upon photoisomerization. Many of these ligands are azobenzenes that are thermodynamically more stable in their elongated trans‐configuration. Often, they are biologically active in this form and lose activity upon irradiation and photoisomerization to their cis‐isomer. Recently, cyclic azobenzenes, so‐called diazocines, have emerged, which are thermodynamically more stable in their bent cis‐form. Incorporation of these switches into a variety of photopharmaceuticals could convert dark‐active ligands into dark‐inactive ligands, which is preferred in most biological applications. This “pharmacological sign‐inversion” is demonstrated for a photochromic blocker of voltage‐gated potassium channels, termed CAL, and a photochromic opener of G protein‐coupled inwardly rectifying potassium (GIRK) channels, termed CLOGO.

G-protein coupled inwardly rectifying potassium (GIRK) channels are an integral part of inhibitory signal transduction pathways, reducing the activity of excitable cells via hyperpolarization. They play crucial roles in processes such as cardiac output, cognition and the coordination of movement. Therefore, the precision control of GIRK channels is of critical importance. Here, we describe the development of the azobenzene containing molecule VLOGO (Visible Light Operated GIRK channel Opener), which activates GIRK channels in the dark and is promptly deactivated when illuminated with green light. VLOGO is a valuable addition to the existing tools for the optical control of GIRK channels as it circumvents the need to use potentially harmful UV irradiation. We therefore believe that VLOGO will be a useful research tool for studying GIRK channels in biological systems.

Herein, we report a photoswitchable modulator for a nuclear hormone receptor that exerts its hormonal effects in a light-dependent fashion.

The field of molecular electronics has progressed in recent years and demonstrated functionalities such as singlemolecule switches, [1,2] field emitters, [3] and even gateable structures. [4,5] Variations of the overall conductance of all these structures in nominally identical junctions were, however, large. Differences in conductance between these junctions were identified by recording conductance histograms of all measured junctions. Large conductance variations could be demonstrated between highand low-conductance states by using quantum interference effects [5] or by changing the molecular structures in a controlled way. [6] To be able to use molecules as future components in electronic applications, it would be useful not only to have binary, high and low, conductance states available, but also a range of possible modifications to fine-tune the exact properties of the circuit. Metallorganic components lend themselves for this purpose because of the broad palette of ions, promising also a broad range of achievable conductance properties. The influence of metal ions incorporated into porphyrin molecules has already been investigated, showing a decrease in conductance due to destabilization of the π-system by metalThe creation of molecular components for use as electronic devices has made enormous progress. In order to advance the field further toward realistic electronic concepts, methods for the controlled modification of the conducting properties of the molecules contacted by metallic electrodes need to be further developed. Here a comprehensive study of charge transport in a class of molecules that allows modifications by introducing metal centers into organic structures is presented. Single molecules are electrically contacted and characterized in order to understand the role of the metal centers in the conductance mechanism through the molecular junctions. It is shown that the presence of single metal ions modifies the energy levels and the coupling of the molecules to the electrical contacts, and that these modifications lead to systematic variations in the statistical behavior of transport properties of the molecular junctions. A rigorous statistical analysis of thousands of junctions is performed to reveal this correlation. The understanding of the role of the metal ion in the resulting conductance properties is an essential step toward the development of molecular electronic circuits.

Photopharmacology relies on ligands that change their pharmacodynamics upon photoisomerization. Many of these ligands are azobenzenes that are thermodynamically more stable in their elongated trans‐configuration. Often, they are biologically active in this form and lose activity upon irradiation and photoisomerization to their cis‐isomer. Recently, cyclic azobenzenes, so‐called diazocines, have emerged, which are thermodynamically more stable in their bent cis‐form. Incorporation of these switches into a variety of photopharmaceuticals could convert dark‐active ligands into dark‐inactive ligands, which is preferred in most biological applications. This “pharmacological sign‐inversion” is demonstrated for a photochromic blocker of voltage‐gated potassium channels, termed CAL, and a photochromic opener of G protein‐coupled inwardly rectifying potassium (GIRK) channels, termed CLOGO.

Amides of 1,4-dihydropyridine (DHP) are activated by oxidation for acyl transfer to amines, alcohols and thiols. In the reduced form the DHP amide is stable towards reaction with amines at room temperature. However, upon oxidation with DDQ the acyl donor is activated via a proposed pyridinium intermediate. The activated intermediate reacts with various nucleophiles to give amides, esters, and thio-esters in moderate to high yields.

Oxidative Activation of Dihydropyridine Amides to Reactive Acyl Donors. -On-off switchable acyl donors in the form of dihydropyridine alkyl and arylamides are reacting with various primary and secondary aryl, benzyl, and alkyl amines as well as benzyl alcohols and benzylthiols. The method tolerates free carboxylic acid groups and is applicable to the preparation of peptides and 2,5-diketopiperazines. -(FUNDER, E. D.; TRADS, J. B.; GOTHELF*, K. V.; Org. Biomol. Chem. 13 (2015) 1, 185-198, http://dx.doi.org/10.1039/C4OB01931H ; Cent. DNA Nanotechnol., Dep. Chem., DK-8000 Aarhus, Den.; Eng.) -F. Schill 21-049