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    STUDIA PHYSICA - Issue no. 1 / 2001  
         
  Article:   CORRELATION TIME AND MAGNETIC INTERACTIONS BETWEEN TEMPYO SPIN LABEL AND BLOOD PROTEINS.

Authors:  S. CAVALU, S. SIMON, GHEORGHE DAMIAN, M. DÂNŞOREANU, C.M. LUCACIU. 		 
       
         
  Abstract:  Nitroxyl radicals exihibit a number of chemical and physical properties that make them extremely useful molecules for studyng biochemical systems, especially the metaloporphyrins. The EPR spectrum can be affected by the motional constrains and orientationof the label in the sistem, by the polarity of the sistem and by the presence of other species in the system such as reducing agent and paramagnetic ions.Conversely, a spin label can affect the properties of system. The aim of this work was to investigate the tempyo spin label as a report group for the interactions and the conformational changes of hemoglobin and bovine serum albumin, as function of pH. X band EPR spectra of Tempyo spin label were recorded at room temperature for lyophylized samples containing bovin serum albumin and hemoglobin at various pH values, in order to follow the different type of interactions between the nitroxide radical and functional groups of proteins as well as the pH influence on molecular motion. The rotational correlation time, in the framework of the "moderate jump diffusion" model for rotational difussion, is strongly influenced by pH variation. In both cases, the mobility of tempyo has a reduced value in acidic environment, and encreased in basic environment as a consequence of electrostatic interactions and hydrogen bonding formation.  
         
     
         
         
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