Effective creases and contact angles between membrane domains with high spontaneous curvature.

We show that the short-scale elastic distortions that are excited in the vicinity of the joint between different lipidic membrane domains (at a scale of approximately 10nm) may produce a "crease" from the point of view of the standard elastic description of membranes, i.e., an effective discontinuity in the membrane slope at the level of Helfrich's theory. This "discontinuity" may be accounted for by introducing a line tension with an effective angular dependence. We show that domains bearing strong spontaneous curvatures, such as biological rafts, should exhibit creases with a finite contact angle, almost prescribed, corresponding to a steep extremum of the line energy. Finite contact angles might also occur in symmetric membranes from the recruitment of impurities at the boundary.