An example is Electron Paramagnetic Resonance (EPR) spectroscopy with spin labels
, specially designed chemical "agents" that carry a stable unpaired electron.
Spin labels bounded at albumin binding sites could be released free to the serum when albumin structure was impaired.
This was a spectral diagram constructed from the data generated on the electron paramagnetic resonance spectrometer of the spin label and albumin complex.
Component 1 was attributed to the spin labels
H-bonded to the headgroups, while component 2 possibly arose from spin labels
H-bonded to water molecules or temporally non-hydrogen-bonded.
Changes in the mobility and accessibility of the spin labels, and the distances between spin labels, enables changes in the secondary and tertiary structure of proteins to be discerned.
Selected values for variables such as g-factors, hyperfine structure constants, and line widths can then be used to estimate the biophysical characteristics of the-16-doxyl stearic acid spin label. These biophysical characteristics include angle of the spin-labeled molecule axis' precession, polarity of the environment surrounding the spin label, and the rotation speed of the spin label.
Local elemental analysis by EPR can be used to detect proximity of the spin labels to the clay surface for fluoromica, which may potentially provide information on surfactant orientation with respect to the surface.
The simplest method for characterizing motion of the spin label is the measurement of the maximum splitting 2[A'.sub.zz] in the EPR spectrum, which corresponds to the difference of the resonance fields between the low-field maximum and the high-field minimum of the spectrum (Fig.