Spin labels paramagnetic

Paramagnetic spin labels offer the opportunity to screen for binding sites remote from a known binding site. ° The introduction of these labels increases the Tj-relaxation rate of binding components and therefore results in an observable 

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In ref. 5, a method has been suggested of controlling the character of the spatial distribution of the additive in solid matrices, which is based on analyzing the EPR spectra of spin-labelled molecules introduced into the system under study. Due to the magnetic dipole dipole interactions of the paramagnetic spin-labelled molecules, the width of their EPR lines in the diluted (concentration N < 1 M) vitrified solutions changes in proportion to their concentration... 

Paramagnetic spin label Slow relaxation — Rapid relaxation 81, 82... 

Method of paramagnetic spin labeling. The first experimental proof of SC stabilization on the silica surface and, most likely, in quartz glass in general was obtained in Ref. [70], where I applied the paramagnetic probe... 

For unfolded and partly folded states, the spin label reports on parts of the polypeptide chain that are in transient contact with the segment bearing the spin label. The extent of relaxation enhancement (line broadening) depends on both the distance to the paramagnetic spin label and the lifetime of the interaction. When the chain conformers rapidly interconvert, as is the case... 

Figure 8 Introduction of paramagnetic spin labels for second site screening. Paramagnetic spin labels drastically alter the relaxation properties of binding components. The large gyromagnetic ratio of unpaired electrons amplifies the relaxation via dipole-dipole interaction, which is represented by the arrows. Stars at the edges of the binding ligand illustrate the increased transverse relaxation...

Polnaszek and Bryant (1984a,b) measured the frequency dependence of water proton relaxation for solutions of bovine serum albumin reacted with a nitroxide spin label (4.6 mol of nitroxide per mol of protein). The relaxation is dominated by interaction between water and the paramagnetic spin label. The data were best fit with a translational diffusion model, with the diffusion constant for the surface water in the immediate vicinity of the nitroxide being five times smaller than that for... 

In this section, recent NMR studies of large paramagnetic proteins will be presented. The determination of the solution structures of small paramagnetic proteins will not be discussed, as this has been well covered in recent reviews.189190 The use of paramagnetic spin labels to introduce selective broadening of resonances and to probe solvent-exposed regions of proteins will also be discussed. 

Paramagnetic spin labels as probes of protein structure... 

Note that clarification of the spatial localization of the electron-transfer chain components inside the artificial bilayer membranes is of a key value for the development of biomimetic systems modeling natural photosynthesis. The direct methods of identification of localization specificity of the functional molecules are usually quite laborious. For this reason, in practice, in this particular research, some studies commonly make use of certain analogs of molecular electron relays or of special molecules such as, e.g., paramagnetic spin labeled ones [2,5,6]. 

In the previous sections, we focused on the heme pocket of the heme proteins, whereby the intrinsic paramagnetic centers were used as the probes for structural information. However, the introduction of site-directed spin labeling has revolutionized the world of EPR in the sense that now also intrinsic diamagnetic proteins can be studied by EPR [77,78]. Indeed, in site-directed labeling, a paramagnetic spin label is attached to the protein through reaction of its functional group with the... 

PRE effects. Schilder and co-workers investigated encounter complexes between cytochrome c peroxidase and cytochrome c carrying a paramagnetic spin label. Burmann et reported a related study of conformation and dynamics of a periplasmic chaperone and its complexes with outer-membrane proteins. 

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