| Abstract
| - In the presence of DNA and calcium, multilamellar liposomes of DPPC when in excess form complexesin which two distinct lamellar lipid phases coexist. The structure and phase behavior of both of these havebeen investigated using high-resolution small-angle X-ray scattering. The coexisting lipid phases existwithin the same precipitated condensate with the phase behavior of the unbound lipid being affected bythe complexed lipid phase. While the thermotropic phase transitions of the uncomplexed lipid from Lβ‘-Pβ‘-Lαoccur as expected, the transitions of the bound lipid are substantially altered. This is manifested as anincrease in the main transition temperature, Tm, of the bound lipid, which has been observed before(Tarahovsky, Y. S.; Khusainova, R. S.; Gorelov, A. V.; Nicolaeva, T. I.; Deev, A. A.; Dawson, K. A.; Ivanitsky,G. R. FEBS Lett.1996, 390, 133. Kharakoz, D. P.; Khusainova, R. S.; Gorelov, A. V.; Dawson, K. A. FEBSLett.1999, 446, 27). However, we also observe an apparent disappearance of the ripple phase (Pβ‘) withincreasing calcium concentration in the bound lipid phase. In addition we are in a position to commenton the mechanism of formation for complexes prepared in this way.
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