Structural properties of phospholipids in the XXXX liver inner mitochondrial membrane.

@entity141 @entity2434 @entity3633 @entity35 @entity857
1. The 31P-NMR characteristics of intact @entity35 liver mitochondria, mitoplasts and isolated inner mitochondrial membranes, as well as mitochondrial @entity3633 and @entity2434 , have been examined. 2. @entity35 liver mitochondrial @entity3633 hydrated in excess aqueous buffer undergoes a bilayer-to-hyexagonal (HII) polymorphic phase transition as the temperature is increased through 10 degrees C, and thus prefers the HII arrangement at 37 degrees C. @entity35 liver mitochondiral @entity2434 , on the other hand, adopts the bilayer phase at 37 degrees C. 3. Total inner mitochondrial membrane lipids. dispersed in an excess of aqueous buffer, exhibit 31P-NMR spectra consistent with a bilayer arrangment for the majority of the endogeneous phospholipids; the remainer exhibit spectra consistent with structure allowing isotropic motional averaging. Addition of @entity141 results in hexagonal (HII) phase formation for a portion of the phospholipids, as well as formation of 'lipidic particles' as detected by freeze-fracture techniques. 4. Preparations of inner mitochondrial membrane at 4 and 37 degrees C exhibit 31P-NMR spectra consistent with a bilayer arrangement of the large majority of the endogenous phospholipids which are detected. Approx. 10% of the signal intensity has characteristics indicating isotropic motional averaging processes. Addition of @entity141 results in an increase in the size of this component, which can become the domiant spectral feature. 5. Intact mitochondria, at 4 degrees C, exhibit 31P-NMR spectra arising from both phospholid and small water-soluble molecules ( @entity857 , Pi, etc.). The phospholipid spectrum is characteristic of a bilayer arrangement. At 37 degrees C the phospholipids again give spectra consistent with a bilayer; however, the labile nature of these systems is reflected by increased isotropic motion at longer (at least 30 min) incubation times. 6. It is suggested that the uncoupling action of high @entity141 concentrations on intact mitochondria may be related to a @entity141 -induced disruption of the integrity of the inner mitochondrial phospholipid bilayer. Further, the possibility that non-bilayer lipid structures such as inverted micelles occur in the inner mitochondrial membrane cannot be excluded.
