Abstract:
:The spin label Tempo-maleimide, when "immobilized" in hemoglobin, is shown to exhibit motional fluctuation whose amplitude and/or frequency depend on temperature and solution conditions. These motional fluctuations are observable by several electron spin resonance techniques. For desalted hemoglobin the fluctuations are detectable at approximately -15 degrees C using saturation transfer techniques and at approximately +25 degrees C using line-width measurements of normal absorption spectra. In ammonium sulfate precipitated hemoglobin, however, motional fluctuations are not detectable by either technique up to at least 40 degrees C. The most probable mechanism for spin-label motion appears to be either fluctuations in protein conformation which affect the label binding site or conformational transitions of the nitroxide ring itself. These motional fluctuations are shown to introduce a librational character to the overall label motion during hemoglobin rotational diffusion, with the librational motion significantly affecting the use of spin-label spectral shapes to calculate hemoglobin rotational correlation times.
journal_name
Biochemistryjournal_title
Biochemistryauthors
Johnson MEdoi
10.1021/bi00600a014subject
Has Abstractpub_date
1978-04-04 00:00:00pages
1223-8issue
7eissn
0006-2960issn
1520-4995journal_volume
17pub_type
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