Methods for measuring nanometer-scale distances between specific sites in proteins are essential analysis of their structure and function. In this work we introduce Gd3+ spin labeling nanometer-range distance measurements by high-field pulse electron paramagnetic resonance (EPR). To evaluate the performance such measurements, carried out four-pulse double-electron (DEER) on two proteins, p75ICD τC14, labeled at strategically selected with either nitroxides or labels. analogy to conventional...

Self-assembly of amyloid-β (Aβ) peptides in human brain tissue leads to neurodegeneration Alzheimer's disease (AD). Amyloid fibrils, whose structures have been extensively characterized by solid state nuclear magnetic resonance (ssNMR) and other methods, are the thermodynamic end point Aβ self-assembly. Oligomeric protofibrillar assemblies, less well-understood, also observed as intermediates assembly process vitro implicated important neurotoxic species AD. We report experiments which...

Pulse electron−electron double resonance distance measurements between two high spin Gd3+ ions in a novel bis-Gd3+ complex involving pyridine-based gadolinium tetracarboxylate systems linked by rigid aryl−alkyne unit were carried out at Ka- and W-band frequencies. The experimental found was 2.02 ± 0.02 nm, it further compared with the Gd3+−Gd3+ (2.2126 nm) determined density functional theory.

In the overwhelming majority of exchange-coupled clusters investigated in field molecular magnetism, exchange interaction is constant on temperature. "Breathing" crystals composition Cu(hfac)2LR undergo temperature-induced reversible structural rearrangements accompanied by significant changes effective magnetic moment. Using high-field (W-band) EPR, we provide a solid proof drastic temperature dependence J(T) these compounds that originates from inter-spin distances. Strong revealed EPR...

The binding of NO to reduced myoglobin in solution results the formation two paramagnetic nitrosyl (MbNO) complexes: one with a rhombic g-factor and other an axial one, referred as R- A-forms. In spite past extensive studies MbNO by crystallography, spectroscopy quantum chemical calculations it is still not clear what factors determine appearance forms. this work we applied combination state art high field pulsed EPR (W-band, 3.4 T/95 GHz) further characterize Specifically, have used 1H 2H...

Exchange-coupled spin triads nitroxide–copper(II)–nitroxide are the key building blocks of molecular magnets Cu(hfac)2LR. These compounds exhibit thermally induced structural rearrangements and transitions, where exchange interaction between spins copper(II) ion nitroxide radicals changes typically by 1 order magnitude. We have shown previously that electron paramagnetic resonance (EPR) spectroscopy is sensitive to observed magnetic anomalies provides information on both inter- intracluster...

In our previous study of the fatal R160Q mutant human sulfite oxidase (hSO) at low pH (Astashkin et al. J. Am. Chem. Soc.2008, 130, 8471–8480), a new Mo(V) species, denoted "species 1", was observed values. Species 1 ascribed to six-coordinate center with an exchangeable terminal oxo ligand and equatorial sulfate group on basis pulsed EPR spectroscopy 33S 17O labeling. Here we report results for species R160Q, based substitution sulfur-containing by phosphate group, in Ka- W-bands, extensive...

Double electron resonance (DEER) is an experimental technique used to determine distance between spins. In this work, we show that it can be study the properties of micelles in solution, specifically their volume and aggregation number. The feasibility method tested on Pluronic block copolymers, PEO(x)-PPO(y)-PEO(x), built from chains poly(ethylene oxide) (PEO), comprising more hydrophilic corona, a poly(propylene (PPO) constituting hydrophobic core. dimensions core L64 (x = 13, y 30), P123...

A new, triple resonance, pulse electron paramagnetic resonance (EPR) sequence is described. It provides spin links between forbidden transitions (ΔMS=±1, ΔMI≠0) and allowed nuclear (ΔMI=±1), thus, facilitating the assignment of frequencies to their respective manifolds centers. also yields relative signs hyperfine couplings different nuclei. The technique based on combination electron-nuclear double (ENDOR) electron-electron (ELDOR)–detected NMR experiments in a way similar TRIPLE...

The RNA helicase DbpA promotes remodeling coupled to ATP hydrolysis. It is unique because of its specificity hairpin 92 23S rRNA (HP92). Although kinetic pathways leading hydrolysis and unwinding have been recently elucidated, the molecular (atomic) basis for coupling remains unclear. This is, in part, due lack detailed structural information on ATPase site presence absence solution. We used high-field pulse ENDOR (electron-nuclear double resonance) spectroscopy detect analyze fine...

Hard-ligand, high-potential copper sites have been characterized in double mutants of Pseudomonas aeruginosa azurin (C112D/M121X (X = L, F, I)). These feature a small Azz(Cu) splitting the EPR spectrum together with enhanced electron transfer activity. Due to these unique properties, constructs called "type zero" sites. In contrast, single mutant, C112D, features large value characteristic typical type 2 CuII. general, comprises contributions from Fermi contact, spin dipolar, and orbital...

Abstract Regulated degradation of mature, cytoplasmic mRNA is a key step in eukaryotic gene regulation. This process typically initiated by the recruitment deadenylase enzymes cis ‐acting elements 3' untranslated region resulting shortening and removal 3′ poly(A) tail target mRNA. The Ccr4‐Not complex, major deadenylase, contains two exoribonuclease subunits with selectivity toward poly(A): Caf1 Ccr4. subunit binds MIF4G domain large CNOT1 (Not1) that scaffold complex. Ccr4 nuclease...

High resolution pulse EPR techniques applied to half integer high spin systems, such as Mn2+ (S = 5/2), usually focus only on the central |−1/2〉→ |1/2〉 transition. The reason is that at fields, where zero field splitting considerably smaller than Zeeman interaction, spectrum of this transition intense and narrow. However, because experiments are carried out low temperatures, lying levels heavily populated signal nevertheless diminished. This, in turn affects sensitivity technique applied. A...

The coordination of bicarbonate to Mn2+ is the simplest model system for carboxylate residues in a protein. Recently, structure such complex has been investigated by means X-band pulse EPR (electron paramagnetic resonance) experiments (Dasgupta, J.; et al. J. Phys. Chem. B 2006, 110, 5099). Based on results, together with electrochemical titrations, it concluded that consists two ligands, one which monodentate and other bidentate, but only latter observed pulsed techniques. measurements,...