Medical College of Wisconsin
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Depth dependence of the perturbing effect of placing a bulky group (oxazolidine ring spin labels) in the membrane on the membrane phase transition. Biochim Biophys Acta 1996 Jan 12;1278(1):68-72



Pubmed ID





Electron paramagnetic resonance (EPR) and differential scanning calorimetry (DSC) have been used to study the effect on the phase transition of dimyristoylphosphatidylcholine membranes of incorporating various stearic acid spin labels (SASL's) that contain the bulky oxazolidine ring at various positions along the stearyl chain. SASL's lowered the phase transition temperature and decreased the size of the cooperative unit, with the effects stronger in the order of 9- > 12- > 5- > 16-SASL > stearic acid (no label). Incorporation of stearic acid without the spin label slightly increases the phase transition temperature. Incorporation of 9-SASL (3 mol% of lipid) decreased the transition temperature by 1.8 degrees C and the cooperative unit to 1/5 of that without the spin label, while the effect of 16-SASL was slight. The effect on transition enthalpy was small. It is concluded that the perturbing effect of placing a bulky group on the alkyl chain on phase transition is through inducing packing defects in the gel-phase.

Author List

Wisniewska A, Nishimoto Y, Hyde JS, Kusumi A, Subczynski WK


Witold K. Subczynski PhD Professor in the Biophysics department at Medical College of Wisconsin

MESH terms used to index this publication - Major topics in bold

Calorimetry, Differential Scanning
Electron Spin Resonance Spectroscopy
Lipid Bilayers
Molecular Structure
Spin Labels
Stearic Acids