@article{20321, abstract = {Microsecond-to-millisecond motions are instrumental for many biomolecular functions, including enzymatic activity and ligand binding. Bloch-McConnell Relaxation Dispersion (BMRD) Nuclear Magnetic Resonance (NMR) spectroscopy is a key technique for studying these dynamic processes. While BMRD experiments are routinely used to probe protein motions in solution, the experiment is more demanding in the solid state, where dipolar couplings complicate the spin dynamics. It is believed that high deuteration levels are required and sufficient to obtain accurate and quantitative data. Here we show that even under fast magic-angle spinning and high levels of deuteration artifactual “bumps” in 15N R1ρ BMRD profiles are common. The origin of these artifacts is identified as a second-order three-spin Mixed Rotational and Rotary Resonance (MIRROR) recoupling condition. These artifacts are found to be a significant confounding factor for the accurate quantification of microsecond protein dynamics using BMRD in the solid state. We show that the application of low-power continuous wave (CW) decoupling simultaneously with the 15N spin-lock leads to the suppression of these conditions and enables quantitative measurements of microsecond exchange in the solid state. Remarkably, the application of decoupling allows the measurement of accurate BMRD even in fully protonated proteins at 100 kHz MAS, thus extending the scope of μs dynamics measurements in MAS NMR.}, author = {Tatman, Benjamin and Sridharan, Vidhyalakshmi and Uttarkabat, Motilal and Jaroniec, Christopher P. and Ernst, Matthias and Rovo, Petra and Schanda, Paul}, issn = {1520-5126}, journal = {Journal of the American Chemical Society}, number = {32}, pages = {29315--29326}, publisher = {American Chemical Society}, title = {{Bumps on the road: The way to clean relaxation dispersion magic-angle spinning NMR}}, doi = {10.1021/jacs.5c09057}, volume = {147}, year = {2025}, } @article{18168, abstract = {Despite the considerable interest in the recombinant production of synthetic spider silk fibers that possess mechanical properties similar to those of native spider silks, such as the cost-effectiveness, tunability, and scalability realization, is still lacking. To address this long-standing challenge, we have constructed an artificial spider silk gene using Golden Gate assembly for the recombinant bacterial production of dragline-mimicking silk, incorporating all the essential components: the N-terminal domain, a 33-residue-long major-ampullate-spidroin-inspired segment repeated 16 times, and the C-terminal domain (N16C). This designed silk-like protein was successfully expressed in Escherichia coli, purified, and cast into films from formic acid. We produced uniformly 13C–15N-labeled N16C films and employed solid-state magic-angle spinning nuclear magnetic resonance (NMR) for characterization. Thus, we could demonstrate that our bioengineered silk-like protein self-assembles into a film where, when hydrated, the solvent-exposed layer of the rigid, β-nanocrystalline polyalanine core undergoes a transition to an α-helical structure, gaining mobility to the extent that it fully dissolves in water and transforms into a highly dynamic random coil. This hydration-induced behavior induces chain dynamics in the glycine-rich amorphous soft segments on the microsecond time scale, contributing to the elasticity of the solid material. Our findings not only reveal the presence of structurally and dynamically distinct segments within the film’s superstructure but also highlight the complexity of the self-organization responsible for the exceptional mechanical properties observed in proteins that mimic dragline silk.}, author = {Wu, Dongqing and Koscic, Anamaria and Schneider, Sonja and Dubini, Romeo C. A. and Rodriguez Camargo, Diana C. and Schneider, Sabine and Rovo, Petra}, issn = {1526-4602}, journal = {Biomacromolecules}, number = {3}, pages = {1759--1774}, publisher = {American Chemical Society}, title = {{Unveiling the dynamic self-assembly of a recombinant dragline-silk-mimicking protein}}, doi = {10.1021/acs.biomac.3c01239}, volume = {25}, year = {2024}, } @article{17078, abstract = {For the emergence of life, the abiotic synthesis of RNA from its monomers is a central step. We found that in alkaline, drying conditions in bulk and at heated air‐water interfaces, 2′,3′‐cyclic nucleotides oligomerised without additional catalyst, forming up to 10‐mers within a day. The oligomerisation proceeded at a pH range of 7–12, at temperatures between 40–80 °C and was marginally enhanced by K+ ions. Among the canonical ribonucleotides, cGMP oligomerised most efficiently. Quantification was performed using HPLC coupled to ESI‐TOF by fitting the isotope distribution to the mass spectra. Our study suggests a oligomerisation mechanism where cGMP aids the incorporation of the relatively unreactive nucleotides C, A and U. The 2′,3′‐cyclic ribonucleotides are byproducts of prebiotic phosphorylation, nucleotide syntheses and RNA hydrolysis, indicating direct recycling pathways. The simple reaction condition offers a plausible entry point for RNA to the evolution of life on early Earth.}, author = {Dass, Avinash Vicholous and Wunnava, Sreekar and Langlais, Juliette and von der Esch, Beatriz and Krusche, Maik and Ufer, Lennard and Chrisam, Nico and Dubini, Romeo C. A. and Gartner, Florian and Angerpointner, Severin and Dirscherl, Christina F. and Rovo, Petra and Mast, Christof B. and Šponer, Judit E. and Ochsenfeld, Christian and Frey, Erwin and Braun, Dieter}, issn = {2570-4206}, journal = {ChemSystemsChem}, number = {1}, publisher = {Wiley}, title = {{RNA oligomerisation without added catalyst from 2′,3′‐cyclic nucleotides by drying at air-water interfaces}}, doi = {10.1002/syst.202200026}, volume = {5}, year = {2023}, } @article{12228, abstract = {The question of how RNA, as the principal carrier of genetic information evolved is fundamentally important for our understanding of the origin of life. The RNA molecule is far too complex to have formed in one evolutionary step, suggesting that ancestral proto-RNAs (first ancestor of RNA) may have existed, which evolved over time into the RNA of today. Here we show that isoxazole nucleosides, which are quickly formed from hydroxylamine, cyanoacetylene, urea and ribose, are plausible precursors for RNA. The isoxazole nucleoside can rearrange within an RNA-strand to give cytidine, which leads to an increase of pairing stability. If the proto-RNA contains a canonical seed-nucleoside with defined stereochemistry, the seed-nucleoside can control the configuration of the anomeric center that forms during the in-RNA transformation. The results demonstrate that RNA could have emerged from evolutionarily primitive precursor isoxazole ribosides after strand formation.}, author = {Xu, Felix and Crisp, Antony and Schinkel, Thea and Dubini, Romeo C. A. and Hübner, Sarah and Becker, Sidney and Schelter, Florian and Rovo, Petra and Carell, Thomas}, issn = {1521-3773}, journal = {Angewandte Chemie International Edition}, keywords = {General Chemistry, Catalysis}, number = {45}, publisher = {Wiley}, title = {{Isoxazole nucleosides as building blocks for a plausible proto‐RNA}}, doi = {10.1002/anie.202211945}, volume = {61}, year = {2022}, } @article{10758, abstract = {5-Carboxycytosine (5caC) is a rare epigenetic modification found in nucleic acids of all domains of life. Despite its sparse genomic abundance, 5caC is presumed to play essential regulatory roles in transcription, maintenance and base-excision processes in DNA. In this work, we utilize nuclear magnetic resonance (NMR) spectroscopy to address the effects of 5caC incorporation into canonical DNA strands at multiple pH and temperature conditions. Our results demonstrate that 5caC has a pH-dependent global destabilizing and a base-pair mobility enhancing local impact on dsDNA, albeit without any detectable influence on the ground-state B-DNA structure. Measurement of hybridization thermodynamics and kinetics of 5caC-bearing DNA duplexes highlighted how acidic environment (pH 5.8 and 4.7) destabilizes the double-stranded structure by ∼10–20 kJ mol–1 at 37 °C when compared to the same sample at neutral pH. Protonation of 5caC results in a lower activation energy for the dissociation process and a higher barrier for annealing. Studies on conformational exchange on the microsecond time scale regime revealed a sharply localized base-pair motion involving exclusively the modified site and its immediate surroundings. By direct comparison with canonical and 5-formylcytosine (5fC)-edited strands, we were able to address the impact of the two most oxidized naturally occurring cytosine derivatives in the genome. These insights on 5caC’s subtle sensitivity to acidic pH contribute to the long-standing questions of its capacity as a substrate in base excision repair processes and its purpose as an independent, stable epigenetic mark.}, author = {Dubini, Romeo C. A. and Korytiaková, Eva and Schinkel, Thea and Heinrichs, Pia and Carell, Thomas and Rovo, Petra}, issn = {2694-2445}, journal = {ACS Physical Chemistry Au}, number = {3}, pages = {237--246}, publisher = {American Chemical Society}, title = {{1H NMR chemical exchange techniques reveal local and global effects of oxidized cytosine derivatives}}, doi = {10.1021/acsphyschemau.1c00050}, volume = {2}, year = {2022}, }