Spin-labeled biomolecules.

Spin-labeled biomolecules.

are remarkably stable and inert,1 and show sharp, well-resolved, and simple paramagnetic resonance spectra2 that are sensitive to molecular motion,3 and, to a lesser extent, sensitive to polarity of the molecular environment.4 As shown below, such nitroxide radicals containing an isocyanate group can be bound to proteins and synthetic polypeptides in a manner similar to that used previously to ...

Multiple-spin analysis of chemical-shift-selective (13C, 13C) transfer in uniformly labeled biomolecules.

Chemical-shift-selective (13C, 13C) polarization transfer is analyzed in uniformly labeled biomolecules. It is shown that the spin system dynamics remain sensitive to the distance of interest and can be well reproduced within a quantum-mechanical multiple-spin analysis. These results lead to a general approach on how to describe chemical-shift-selective transfer in uniformly labeled systems. As...

Electron Spin Resonance of Biomolecules

Spin-labeled hemoglobin.

In the present paper we describe the results of a preliminary study of the paramagnetic resonance spectrum of spin-labeled horse hemoglobin in solution. Our results provide strong evidence that on oxygenation the A chains undergo a significant structural change near the "reactive" sulfhydryl group (f693), a change not yet resolved by X-ray diffraction.' We also find features in the paramagnetic...

Spin-Labeled Membranes

In the next few minutes I shall present a very brief discussion of what the spin-label technique is, and how it may be used to study biological membranes, x, 2 A "spin label" is a synthetic organic paramagnetic free radical. Most spin