Fusion of intracellular transport vesicles requires soluble N-ethylmaleimide-sensitive factor attachment protein receptors (SNAREs) and Sec1/Munc18-family (SM) proteins. Membrane-bridging SNARE complexes are critical for fusion, but their spontaneous assembly is inefficient and may require SM proteins in vivo. We report x-ray structures of Vps33, the SM subunit of the yeast homotypic fusion and...

Full length v-SNARE protein in lipid vesicles when exposed to t-SNARE-reconstituted lipid membrane results in the self-assembly of a t-/v-SNARE complex in a ring pattern, forming pores, and establishing continuity between the opposing bilayers. It is known that smaller vesicles fuse more efficiently than larger ones, and hence the curvature of secretory vesicles may dictate the potency and effi...

We represent the elements of K 1 of an exact category by means of two-and three-edge loops in the triple G-construction. The corresponding algebraic data are double short exact sequences and non-commutative 33-diagrams of short exact sequences. We state conjectural relations for the elements of K 1 in terms of 3 3-diagrams. 1. Review of the G-and the triple G-construction In GG] Gillet and Gray...

Systems composed of many interacting dynamical networks-such as the human body with its biological networks or the global economic network consisting of regional clusters-often exhibit complicated collective dynamics. Three fundamental processes that are typically present are failure, damage spread and recovery. Here we develop a model for such systems and find a very rich phase diagram that be...

During spermiogenesis, hydrolytic enzymes are sorted from the Golgi apparatus to the acrosome, a supranuclear megavesicle. At fertilization, the enzymatic content of the acrosome is released by exocytosis when a portion of the plasma membrane enveloping the sperm head fuses with the outer membrane of the acrosome. Membrane fusion involves the interaction of a specific pair of proteins, called S...

BACKGROUND Peripapillary loops of venous origin are extremely rare. CASE A 55-year-old woman was referred to us for further examination of peripapillary vascular abnormalities. OBSERVATIONS Fundus examination and fluorescein angiography clearly showed a venous and an arterial peripapillary loop in both her right and left fundi. The venous loop in the right eye was in a large hairpin configu...

SNARE (soluble N-ethylmaleimide-sensitive factor attachment protein receptor) proteins mediate fusion by pulling biological membranes together via a zippering mechanism. Recent biophysical studies have shown that t- and v-SNAREs can assemble in multiple stages from the N-termini toward the C-termini. Here we show that functionally, membrane fusion requires a sequential, two-step folding pathway...

In quantum geometry, we consider a set of loops, compact orientable surface and solid spatial region, all inside ℝ × ℝ3 = ℝ4, which forms triple. We want to define an ambient isotopic equivalence relation on such triples, so that can obtain invariants. These invariants describe how these submanifolds are causally related or ‘linked’ with each other, they closely associated the linking number be...

The discoidin domain receptors, DDR1 and DDR2, are widely expressed receptor tyrosine kinases that are activated by triple-helical collagen. They control important aspects of cell behavior and are dysregulated in several human diseases. The major DDR2-binding site in collagens I-III is a GVMGFO motif (O is hydroxyproline) that also binds the matricellular protein SPARC. We have determined the c...

This paper establishes a link between Noncommutative Geometry and canonical quantum gravity. A semi-finite spectral triple over a space of connections is presented. The triple involves an algebra of holonomy loops and a Dirac type operator which resembles a global functional derivation operator. The interaction between the Dirac operator and the algebra reproduces the Poisson structure of Gener...