Textured domains on tense surfaces and membranes: Effect of tilt and chirality.

We study the shape and texture of finite domains comprising chiral or achiral molecules carrying tilt, embedded in a two-dimensional surface or membrane, using a combination of simulations and exact variational calculations. We find a variety of shapes and textures including rectangular-shaped domains and a spontaneously broken chiral texture, when the molecules are achiral. We show that chiral tilt domains nucleating in a region of two-phase coexistence repel each other, thereby preventing coalescence and further growth.

Caste and sex specific olfactory glomerular organization and brain architecture in two sympatric ant species Camponotus sericeus and Camponotus compressus (Fabricius, 1798).

We use monoclonal antibodies against synaptic proteins and anterograde tracing with neurobiotin to describe the architecture of the antennal lobes in different castes of two ant species -Camponotus sericeus and Camponotus compressus. The reproductives and worker classes are readily categorized based on size and external morphology. The overall organization of brain neuropile is comparable between castes with differences only in the visual ganglia.

Chirality-induced budding: a raft-mediated mechanism for endocytosis and morphology of caveolae?

The formation of transport carriers (spherical vesicles and tubules) involves membrane budding, growth, and ultimately fission. We propose a mechanism of membrane budding, wherein the tilt and chirality of constituent molecules, confined to a patch of area A, induces buds of approximately 50-100 nm that are comparable to vesicles involved in endocytosis. Because such chiral and tilted lipid molecules are likely to exist in "rafts", we suggest the involvement of this mechanism in generating membrane buds in the clathrin and dynamin-independent, raft-component mediated endocytosis of glycosylphosphatidylinositol-anchored proteins.

Nanoscale organization of multiple GPI-anchored proteins in living cell membranes.

Cholesterol and sphingolipid-enriched "rafts" have long been proposed as platforms for the sorting of specific membrane components including glycosyl-phosphatidylinositol-anchored proteins (GPI-APs), however, their existence and physical properties have been controversial. Here, we investigate the size of lipid-dependent organization of GPI-APs in live cells, using homo and hetero-FRET-based experiments, combined with theoretical modeling. These studies reveal an unexpected organization wherein cell surface GPI-APs are present as monomers and a smaller fraction (20%-40%) as nanoscale (<5 nm) cholesterol-sensitive clusters.

Active fusion and fission processes on a fluid membrane.

We investigate the steady states and dynamical instabilities resulting from "particles" depositing on (fusion) and pinching off (fission) a fluid membrane. These particles could be either small lipid vesicles or isolated proteins. In the stable case, such fusion/fission events suppress long wavelength fluctuations of the membrane.