Spin-labeling

Figure Bl.15.14. Comparison of 95.1 GHz (A) and 9.71 GHz (B) EPR spectra for a frozen solution of a nitroxide spin label attached to insulin measured at 170 K.

The structure of spin-labeled acetylenes includes 7r-electron-rich pyrazole and... 

Sodium dodecyl sulfate micelle 71,72,77,79 Spin label 139 Starch 100, 104 —, crosslinked 106 —, graft polymers 105, 107, 125, 127 Styrene 160—162 Styrene-divinylbenzene resins 167 Styrenesulfonic acid, copolymers 74—76 Surface area 147... 

Interaction of spin labels with transition metals. S. S. Eaton and G. R. Eaton, Coord. Chem. Rev., 1978,26, 207-262 (218). 

The values for the lipid molecules compare well (althoughJgiey are still somewhat larger) with the experimental value of 1.5x10 cm /s as measured with the use of a nitroxide spin label. We note that the discrepancy of one order of magnitude, as found in the previous simulation with simplified head groups, is no longer observed. Hence we may safely conclude that the diffusion coefficient of the lipid molecules is determined by hydrodynamic interactions of the head groups with the aqueous layer rather than by the interactions within the lipid layer. The diffusion coefficient of water is about three times smaller than the value of the pure model water thus the water in the bilayer diffuses about three times slower than in the bulk. 

In the second case, the 180° pulse is applied only to nucleus A, causing an exchange of spin labels of the A spin states to occur, so the direction of rotation of the X magnetization vectors is reversed during the second... 

An expansion of the method can be found in second-site SLAPSTIC, where, in favorable cases, a second binding site close to the binding site of interest can be used to infer a spin label via a second ligand [116]. 

Berliner, L.J. (1976) Spin-labelling Theory and Applications Academic Press, New York. 

Ligeza A, Tikhonov AN, Hyde JS, Subczynski WK. 1998. Oxygen permeability of thylakoid membranes Electron paramagnetic resonance spin labeling study. Biochim Biophys Acta 1365 453. 

However, the equilibrium of the indicator adsorbed at an interface may also be affected by a lower dielectric constant as compared to bulk water. Therefore, it is better to use instead pH, the interfacial and bulk pK values in Eq. (50). The concept of the use at pH indicators for the evaluation of Ajy is also basis of other methods, like spin-labeled EPR, optical and electrochemical probes [19,70]. The results of the determination of the Aj by means of these methods may be loaded with an error of up to 50mV [19]. For some the potentials determined by these methods, Ajy values are in a good agreement with the electrokinetic (zeta) potentials found using microelectrophoresis [73]. It is proof that, for small systems, there is lack of methods for finding the complete value of A>. 

Fig. 1.11 Structure of spin-labelled adenosine (l-oxyl-2,2,5,5-tetramethylpyrroline-3-carboxylate (5-aminoadenosine) -amide).

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