Theoretical study of the effect of .alpha.-substituents on the silicon-29 hyperfine splitting constant in silyl radicals: an electronic rather than structural effect

1993 ◽  
Vol 115 (25) ◽  
pp. 11926-11929 ◽  
Author(s):  
Maurizio Guerra
Keyword(s):  
Hyperfine Splitting ◽  
Theoretical Study ◽  
Structural Effect ◽  
Silyl Radicals ◽  
Hyperfine Splitting Constant ◽  
Splitting Constant

scholarly journals What properties of non-electrolyte solutions does a DNA molecule feel?

2021 ◽  
Vol 13 (2) ◽  
pp. 129-136
Author(s):  
George G. Malenkov ◽  
Keyword(s):  
Relative Humidity ◽  
Ethylene Glycol ◽  
Water Activity ◽  
Hyperfine Splitting ◽  
Solvent Polarity ◽  
Electrolyte Solutions ◽  
Water Solutions ◽  
Hyperfine Splitting Constant ◽  
Splitting Constant ◽  
In The Beginning

As early as in 1953 it was reported that at low relative humidity of the atmosphere (about 70 %) DNA films were in A-form, while at higher humidity (more than 80%) they were in B-form. Relative humidity of the atmosphere corresponds to the water activity in the system. It was found in the beginning of the 70th that DNA transfers to the A-form when non-electrolytes, such as monoatomic alcohols, dioxane, tetrahydrofurane were added to water. It was reasonable to suppose that B to A transition of DNA occurs in the non-electrolyte solutions at the same values af water activity as in the moist atmosphere. This prediction was borne out. But in water solutions of very polar non-electrolytes such as methanol and ethylene glycol B to A DNA does not occur even at very low water activity values. It was supposed that A form of DNA can arise only in the medium with sufficiently low polarity. We used hyperfine splitting constant (A) of a nitroxide spin label determined from the EPR spectra as a measure of the liquid solvent polarity. It was found that DNA transition into B form occurs when A reached a certain value. Polarity of methanol and ethylene glycol is much higher than that of the solutions in which B to A DNA transition takes place. This transition also occurs in water solutions of trifluoroethanol. But in these solutions the transition takes place at hyperfine splitting values, which are much greater than in other non-electrolyte solutions. Water activity in the zone of B-A DNA transition in trifluoroethanol solutions does not correspond water activity which was calculated for other nob-electrolyte solutions in which B-A transition is observed.

First Synthesis of C-Phenyl N-tert-Butyl [15N]nitrone (PBN-15N) for the EPR Spin Trapping Methodology

1996 ◽  
Vol 51 (1) ◽  
pp. 139-143 ◽  
Author(s):  
Yong-Kang Zhang
Keyword(s):  
Hyperfine Splitting ◽  
Spin Trap ◽  
Spin Trapping ◽  
Paramagnetic Resonance ◽  
Tert Butyl ◽  
Hyperfine Splitting Constant ◽  
Percent Increase ◽  
Splitting Constant ◽  
Epr Spin Trapping ◽  
Electron Paramagnetic

As compared to normal PBN, about fifty percent increase of electron paramagnetic resonance (EPR) spin trapping sensitivity has been gained by using a new 100% 15N-enriched spin trap, C-phenyl N-tert-butyl[15N]nitrone (PBN-15N). PBN-15N has been prepared by a convenient four-step route using ammonium-15N chloride as the starting material. This synthetic method produces 2-methyl-2-[15N]nitropropane which is useful for the synthesis of many other PBN-15N type spin traps for the purpose of increasing spin trapping sensitivity. EPR spin trapping with PBN-15N in benzene and in phosphate buffer has been investigated. The 15N hyperfine splitting constant (15N-hfsc) is larger than 14N-hfsc by 40%. The larger 15N-hfsc gives more opportunity to identify different radical addends within the same system.

scholarly journals Dependence on freezing of the geometry and redox potential of type 1 and type 2 copper sites of Japanese-lacquer-tree (Rhus vernicifera) laccase

1981 ◽  
Vol 193 (2) ◽  
pp. 639-642 ◽  
Author(s):  
L Morpurgo ◽  
L Calabrese ◽  
A Desideri ◽  
G Rotilio
Keyword(s):  
Redox Potential ◽  
Hyperfine Splitting ◽  
Room Temperature ◽  
Redox Properties ◽  
Blue Copper ◽  
Hyperfine Splitting Constant ◽  
Splitting Constant ◽  
Rhus Vernicifera

The room-temperature e.p.r. spectrum of the Japanese-lacquer-tree (Rhus vernicifera) laccase shows A parallel (the hyperfine splitting constant) and g parallel values of both the Type 1 and Type 2 Cu appreciably different from those measured at liquid-N2 temperature. The geometry of the sites, as inferred from the room-temperature e.p.r. parameters, is more consistent with their redox properties. A rough correlation is found between A parallel and g parallel values and redox potential of the blue copper in several enzymes.

An estimation of the magnitudes of the contributions from spin polarization and from hyperconjugation to the hyperfine splitting constant of an hydroxylic proton

1969 ◽  
Vol 47 (20) ◽  
pp. 3717-3724 ◽  
Author(s):  
T. E. Gough ◽  
G. A. Taylor
Keyword(s):  
Harmonic Oscillator ◽  
Spin Polarization ◽  
Hyperfine Splitting ◽  
Elevated Temperatures ◽  
Hydroxyl Group ◽  
Positive Contribution ◽  
Hyperfine Splitting Constant ◽  
Splitting Constant ◽  
Spin Densities ◽  
Hydroxylic Proton

Proton hyperfine splitting constants of monoprotonated p-benzosemiquinone are presented for a range of solvents and sample-temperatures. The dependences of these splittings upon temperature, together with the assumption that the hydroxyl group can be described as a torsional harmonic oscillator, are used to evaluate an equation linking aOH, the hyperfine splitting constant of the hydroxylic proton, in gauss, with ρO and ρC, the spin densities on the hydroxyl oxygen and on the adjacent carbon atoms, and θ, the dihedral angle between the O—H bond and the plane of the aromatic ring.[Formula: see text]Experimental evidence of a positive contribution to aOH is obtained from the spectra of monoprotonated durosemiquinone in tri-n-butylphosphate at elevated temperatures.

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