Resolving the nanometer-scale structure of biomolecules in natural conditions still remains a challenging task. We report first distance measurement nucleic acid at physiological temperature using electron paramagnetic resonance (EPR). The model 10-mer DNA duplex has been labeled with reactive forms triarylmethyl radicals and then immobilized on sorbent water solution investigated by double quantum coherence EPR. succeeded development optimal triarylmethyl-based labels, approach for...

Triarylmethyl radicals (trityls, TAMs) represent a relatively new class of spin labels. The long relaxation trityls at room temperature in liquid solutions makes them promising alternative for traditional nitroxides. In this work we have synthesized series TAMs including perdeuterated Finland trityl (D36 form), mono-, di-, and triester derivatives Finland-D36 trityl, the deuterated form OX63, dodeca-n-butyl homologue triamide with primary secondary amines attached. We studied...

Triarylmethyl (trityl, TAM) based spin labels represent a promising alternative to nitroxides for EPR distance measurements in biomolecules. Herewith, we report synthesis and comparative study of series model DNA duplexes, 5′-spin-labeled with TAMs nitroxides. We have found that the accuracy (width) distributions obtained by double electron–electron resonance (DEER/PELDOR) strongly depends on type radical. Replacement both same spin-labeled duplex allows narrowing factor 3. one nitroxide TAM...

Pulsed Dipolar Spectroscopy (PDS) methods of Electron Paramagnetic Resonance (EPR) were used to detect and characterize reversible non-covalent dimers Human Serum Albumin (HSA), the most abundant protein in human plasma. The spin labels, MTSL OX063, attached Cys-34 these chemical modifications did affect dimerization HSA, indicating that other post-translational can modulate dimer formation. At physiologically relevant concentrations, HSA does form weak, with a well-defined structure. Dimer...

The nitroxides of 7-azadispiro[5.1.5.2]pentadecane and 7-azadispiro[5.1.5.2]pentadeca-14-ene series have been prepared, including thiol-specific methane thiosulfonate spin label for site-directed labeling. effect spirocyclohexane moieties on chemical spectral properties has studied. obtained temperature dependencies electron relaxation parameters demonstrate that new may be suitable PELDOR distance measurements at 80–120 K. Moreover, the demonstrated much higher stability toward reduction by...

Abstract Trityl radicals (TAMs) have recently appeared as an alternative source of spin labels for measuring long distances in biological systems. Finland trityl radical (FTAM) served the basis this new generation labels, but FTAM is rather lipophilic and susceptible to self‐aggregation, noncovalent binding with sites proteins, docking at termini duplex DNA. In paper very hydrophilic OX063 TAM low toxicity little tendency aggregation used a label. Human serum albumin (HSA) labeled has...

Zeolite imidazolate framework-8 (ZIF-8) is a promising platform for drug delivery, and information regarding the stability of ZIF-8 nanoparticles in cell culture media essential proper interpretation vitro experimental results. In this work, we report quantitative investigation nanoparticle's most common media. To purpose, containing sterically shielded nitroxide probes with high resistance to reduction were synthesized studied using electron paramagnetic resonance (EPR). The degradation was...

In cancer diagnostics, magnetic resonance imaging (MRI) uses contrast agents to enhance the distinction between target tissue and background. Several promising approaches have been developed increase MRI sensitivity, one of which is Overhauser dynamic nuclear polarization (ODNP)-enhanced (OMRI). this study, a macromolecular construct based on human serum albumin nitroxyl radicals (HSA-NIT) was using new synthesis method that significantly increased modification 21 nitroxide residues per...

The interaction of sodium phytate hydrate C6H18O24P6·xNa·yH2O (phytNa) with Cu(OAc)2·H2O and 1,10-phenanthroline (phen) led to the anionic tetranuclear complex [Cu4(H2O)4(phen)4(phyt)]·2Na+·2NH4+·32H2O (1), structure latter was determined by X-ray diffraction analysis. 1 is completely deprotonated; six phosphate− fragments (with atoms P1–P6) are characterized different spatial arrangements relative cyclohexane ring (1a5e conformation), which determines two types coordination complexing...

In this study, we investigated the structural variability of mRNA in human ribosome by comparing two spin-labeling strategies: one involving an analog bearing spin labels attached to ribose-phosphate backbone and other placing at nucleotide bases. The use strategies labeling mRNAs allowed us study for first time effect structure location on measured interspin distances complexes. Experiments using dipolar EPR spectroscopy, supported molecular dynamics calculations, demonstrated that...

Nanoscale distance measurements by pulse dipolar Electron paramagnetic resonance (EPR) spectroscopy allow new insights into the structure and dynamics of complex biopolymers. EPR detection requires site directed spin labeling (SDSL) biomolecule(s), which remained challenging for long RNAs up-to-date. Here, we demonstrate that novel complementary-addressed SDSL approach allows efficient following structural studies RNAs. We succeeded to spin-label Hepatitis C Virus RNA internal ribosome entry...

Abstract Precise nanoscale distance measurements by pulsed electron paramagnetic resonance (EPR) spectroscopy play a crucial role in structural studies of biomolecules. The properties the spin labels used this approach determine sensitivity limits, attainable distances, and proximity to biological conditions. Herein, we propose validate use photoexcited fullerenes as for dipolar (PD) EPR measurements. Hyperpolarization narrower spectrum compared other triplets (e.g., porphyrins) boost...

Triarylmethyl (trityl, TAM) radicals are a promising class of spin labels for nanometer-scale distance measurements in biomolecules at physiological temperatures. However, to date, existing approaches site-directed TAM labeling DNA have been limited label attachment the termini oligonucleotides, thus hindering majority demanded applications. Herein, we report new versatile strategy arbitrary sites nucleic acids. It utilizes an achiral non-nucleoside phosphoramidite monomer automated...

Triplet states of photoexcited organic molecules are promising spin labels with advanced spectroscopic properties for pulsed dipolar electron paramagnetic resonance (PD EPR) spectroscopy. Recently proposed triplet fullerene have shown great potential double electron-electron (DEER) distance measurements as "observer spins" due to a high quantum yield the state, hyperpolarization and relatively narrow EPR spectra. Here, we demonstrate applicability other PD techniques, such relaxation induced...

Electron paramagnetic resonance (EPR) based nanometer distance measurements at ambient temperatures are of particular interest for structural biology applications. The nitroxide spin labels commonly used in EPR reveal relatively short transverse relaxation under these conditions, which limits their use detecting static dipolar interactions. At the same time, longitudinal is still long enough to allow using them as 'pumped' species induced modulation enhancement (RIDME) experiment where...

Four albumin-nitroxide conjugates were prepared and tested as metal-free organic radical contrast agents (ORCAs) for magnetic resonance imaging (MRI). Each human serum albumin (HSA) carrier bears multiple nitroxides conjugated via homocysteine thiolactones. These molecular retain important physical biological properties of their HSA component, the resistance nitroxide groups to bioreduction was retained or enhanced. The relaxivities are similar these four much greater than those individual...

Site-directed spin labeling (SDSL) is widely applied for structural studies of biopolymers by electron paramagnetic resonance (EPR). However, SDSL long RNA sequences still remains a challenging task. Here, we propose novel approach potentially suitable natural RNAs, which based on the attachment linker containing an aliphatic amino group to target nucleotide residue followed selective coupling label this group. Such can be attached desired via sequence-specific reaction with derivatives...

We propose a new potent approach for studying nano/microscopic heterogeneities in ionic liquids exploiting stochastic librations of nitroxides and pulse EPR.

Triarylmethyl (TAM) radicals are widely used in Electron Paramagnetic Resonance (EPR) spectroscopy as spin labels and EPR imaging probes for vivo oxymetry. One of the key advantages TAMs is extremely narrow line, especially case deuterated analogues (~5 μT). Another advantage their slow relaxation even at physiological temperatures allowing, particular, application pulsed dipolar methods distance measurements biomolecules. In this paper a large series TAM synthesized, corresponding...

Abstract Precise nanoscale distance measurements by pulsed electron paramagnetic resonance (EPR) spectroscopy play a crucial role in structural studies of biomolecules. The properties the spin labels used this approach determine sensitivity limits, attainable distances, and proximity to biological conditions. Herein, we propose validate use photoexcited fullerenes as for dipolar (PD) EPR measurements. Hyperpolarization narrower spectrum compared other triplets (e.g., porphyrins) boost...

RL2 is a recombinant analogue of human κ-casein fragment, capable penetrating cells and inducing apoptosis cancer with no toxicity to normal cells. The exact mechanism penetration into remains unknown. In this study, we investigated the lung A549 by combination electron paramagnetic resonance (EPR) spectroscopy confocal laser scanning microscopy. EPR spectra incubated (sRL2) spin-labeled highly stable 3-carboxy-2,2,5,5-tetraethylpyrrolidine-1-oxyl radical were found contain three components,...