Pulsed electron double resonance

Weber et al. have developed pulsed electron double resonance (PELDOR) at S-band, and used it to probe the dipolar and exchange interactions in the bis-nitroxides 13 - 16, where in the ester-bridged compounds the exchange interactions are diminished relative to the acetylene-bridged compounds, whilst maintaining a similar separation.10 They also demonstrate distance measurements by this technique. 

Milov, A. D., Maryasov, A. G., and Tsvetkov, Y. D. (1998). Pulsed electron double resonance (PELDOR) and its applications in ffee-radicals research. Appl. Magn. Reson. 15, 107—143. 

Pulsed methods [82] increase the range of distance sensitivity. They can be used to separate the dipole-dipole interaction from other contributions of the spin Hamiltonian. At very large available microwave power, distances can be measured well by double quantum coherence (DQC) that uses a single frequency. With the power available on commercial spectrometers, double electron electron resonance [DEER, an acronym which is synonymously used with PELDOR (Pulsed Electron Double Resonance)] is the more sensitive technique and is thus most widely applied in the... 

C. Elsasser, M. Brecht and R. Bittl, Pulsed electron-electron double resonance on multinuclear metal clusters Assignment of spin projection factors bsed on the dipolar interaction, J. Am. Chem. Soc., 2002, 124, 12606. 

Double-resonance spectroscopy involves the use of two different sources of radiation. In the context of EPR, these usually are a microwave and a radiowave or (less common) a microwave and another microwave. The two combinations were originally called ENDOR (electron nuclear double resonance) and ELDOR (electron electron double resonance), but the development of many variations on this theme has led to a wide spectrum of derived techniques and associated acronyms, such as ESEEM (electron spin echo envelope modulation), which is a pulsed variant of ENDOR, or DEER (double electron electron spin resonance), which is a pulsed variant of ELDOR. The basic principle involves the saturation (partially or wholly) of an EPR absorption and the subsequent transfer of spin energy to a different absorption by means of the second radiation, leading to the detection of the difference signal. The requirement of saturability implies operation at close to liquid helium, or even lower, temperatures, which, combined with long experimentation times, produces a... 

Two traditions have evolved concerning the naming of pulsed electron-electron double resonance, calling these experiments either DEER (double electron-electron resonance) or PELDOR (pulsed electron-electron double resonance). In the ensuing discussion we use each author s preferred designation for their experiments. The absence of a dead-time in the four-pulse DEER experiment is an advantage relative to the three-pulse DEER experiment. When all of the pulses of the three-pulse DEER experiment are at the same frequency, it becomes the 2 +1 pulse sequence.13,14... 

Mapping Global Folds of Oligonucleotides by Pulsed Electron-Electron Double Resonance... 

The understanding of structure-dynamics-function relationships in oligonucleotides or oligonucleotide/protein complexes calls for biophysical methods that can resolve the structure and dynamics of such systems on the critical nanometer length scale. A modern electron paramagnetic resonance (EPR) method called pulsed electron-electron double resonance (PELDOR or DEER) has been shown to reliably and precisely provide distances and distance distributions in the range of 1.5-8 nm. In addition, recent experiments proved that a PELDOR experiment also contains information on the orientation of labels,... 

Denysenkov, V. P., Prisner, T. F., Stubbe, J., and Bennati, M. (2006). High-field pulsed electron-electron double resonance spectroscopy to determine the orientation of the tyrosyl radicals in ribonucleotide reductase. Proc. Natl. Acad. Sci. USA 103, 13386-13390. 

Several pulse methods were developed for estimation distances between two slowly-relaxing spins. In a pulse electron-electron double resonance (PELDOR) technique a spin echo is created by a two-pulse sequence at one microwave frequency. The timing of a pulse at a second microwave frequency is varied (Milov et al., 1998). This method is suitable for analysis of weak dipolar interactions. 3-pulse PELDOR with all three pulses at the same microwave frequency ( 2 + 1 sequence) was proposed by Raitsimling and his co-workers (2000). A specific feature of the 2 + 1 technique is suppression of dipolar interaction of randomly distributed spins, which allows the selection of a dipolar interaction between radicals. Using a 4- pulse experiments it was possible to eliminate an inherent dead experimental deadtime that limits the magnitude of the dipolar interaction in 2 + 1 sequence and in 3-pulse ELDOR experiments (Pannier et al., 2000). 

Astashkin, A.V., Hara, H., and Kawamori, A. (1998) The pulsed electron-electron double resonance and 2=1 electron spin echo study of the oriented oxygen-evolving and Mn-depleted preparation ofphotoystem II, J. Chem. Phys. 108, 3805-3812. 

Lukoyanov D, Barney BM, Dean DR, Seefeldt LC, Hoffman BM. Coimecting nitrogenase intermediates with the kinetic scheme for N2 reduction by a relaxation protocol and identification of the N2 binding state. Proc. Natl. Acad. Sci. U.S.A. 2007 104 1451-1455. Denysenkov VP, Prisner TF, Stubbe J, Bennati M. High-field pulsed electron-electron double resonance spectroscopy to determine the orientation of the tyrosyl radicals in ribonucleotide reductase. Proc. Natl. Acad. Sci. U.S.A. 2006 103 13386-13390. Schiemann O, Prisner TF. Long-range distance determinations in biomacromolecules by EPR spectroscopy. Quarterly Rev. Biophys. 2007 40 1-53. 

To this list can be added various major specialized sub-systems that are required for some of the more sophisticated experiments. Some of the basic sub-systems also require modification for these experiments. (7) Pulse programmer for time domain ESR (8) programmable radio frequency source for electron-nuclear double resonance (ENDOR) (9) pump microwave source for electron-electron double resonance (ELDOR). 

When tr is sufficiently long, cw EPR spectra become insensitive to nitroxide motion, and the spectra are indistinguishable from powder patterns. Thus, one must rely on spectroscopic methods beyond cw EPR for the extraction of motional processes. Historically, the motional regime between 1(K) nsec and 1 psec has presented a blind spot to EPR spectroscopy, and reliable methods for extraction of t did not exist. More recently, though, this problem has been solved. The technique combines the methods of pulsed saturation recovery EPR (SR-EPR) and pulsed saturation recovery electron-electron double resonance (SR-ELDOR). Spectroscopic saturation occurs when the applied radiation is sufficiently intense... 

Milov AD, Tsvetkov YD, FormaggioE, OanceaS.TonioloC, Raap J (2004) Solvent effect on the distance distribution between spin labels in aggregated spin labeled trichogin GA IV dimer peptides as studied by pulsed electron-electron double resonance. Phys Chem Chem Phys 6 3596-3603... 

Bode BE, Margraf D, Plackmeyer J, Dumer G, Prisner TF, Schiemann O (2007) Counting the monomers in nanometer-sized oligomers by pulsed electron - electron double resonance. J Am Chem Soc 129 6736-6745... 

Dastvan R, Bode BE, Karuppiah MP, Marko A, Lyubenova S, Schwalbe H, Prisner TF (2010) Optimization of transversal relaxation of nitroxides for pulsed electron-electron double resonance spectroscopy in phospholipid membranes. J Phys Chem B 114(42) 13507-13516... 

Marko A, Margraf D, Yu H, Mu Y, Stock G, Prisner T (2009) Molecular orientation studies by pulsed electron-electron double resonance experiments. J Chem Phys 130(6) 064102. doi 10.1063/1.3073040... 

DEER Dead-time free pulsed Electron-Electron double Resonance ... 

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