Tight folds

Like the other paralytic toxins from Conus venom, a-conotoxins are small and very tightly folded, structural features which may be advantageous for rapid paralysis of prey (1). a-Conotoxins are typically 13 to 15 amino acids long with two disulfide bridges (see Table III). In addition to the five a-conotoxins shown, two new a-conotoxins (SIA and SIB) from C. striatus have recently been isolated, sequenced, and chemically synthesized. SIA is very unusual because it is 19 amino acid residues long and it contains 6 cysteine residues, three of which are contiguous near the amino terminus (C. Ramilo et al., unpublished results). 

Figure 7.9 Mechanisms of laying down chain segments on the growing face of a crystallite a) tight folds with adjacent re-entry, b) independent deposition of chain segments... 

Archaea or Archaebacteria, which live in sulphurous waters around undersea volcanic vents. An extraordinarily stable enzyme which functions even at 135 °C and survives at pH 3.2-12.7 has been identified [142]. This enzyme has been termed STABLE (stalk-associated archaebacterial endoprotease). It is suggested that such exceptional stability may be attributable to unusually large Mr and tight folding of the protein chain. Suggested uses include washing powders and detergents, as well as industrial catalysts. It is even proposed that such remarkable properties may have contributed to the early evolution of life on earth [142]. 

Creighton, A. M., Hulford, A., Mant, A., Robinson, D. and Robinson, C. (1995) A monomeric, tightly folded stromal intermediate on the delta pH-dependent thylakoidal protein transport pathway./. Biol. Cbem., 270, 1663-9. 

The MAX property lies near the north end of the Kootenay Arc in tightly folded, strongly sheared Palaeozoic... 

With a leer of triumph he opened one of his huge fists to reveal a tightly folded piece of paper. I found the note ... 

Crystallinity. Polymer chains which possess a regular structure, not only chemically but also sterically, are able to crystallize under suitable conditions, either from the melt, or from solution. This means that the chain molecules change from a coiled and disordered state to a tightly folded, aligned, and ordered state (Figure 2). 

The observation by Maddy and Malcolm (53) that the amide I band of bovine erythrocyte ghosts in D20 is not shifted is remarkable because it implies that all of the membrane protein is either deeply buried in an environment of hydrophobic lipids or exists in a tightly folded a-helical conformation. We have examined extensively the infrared spectra of bovine erythrocyte ghosts, both as dry films and as intact ghosts in D20 and H20 (73). The results for dry films essentially agree with those of other workers and show no evidence of f3 structure. Little change occurs in water. In D20, however, we consistently obtained a shift in the amide I band and a considerable decrease in absorption of the amide II band. 

In V. Cholerae, the Galp residue carries a 4,6-cyclic phosphate. The same repeating unit was found in the capsular polysaccharide. Multidimentional he-teronuclear NMR and molecular-modeling studies showed that the 0139 tetrasaccharide adopts a compact and tightly folded conformation that is relatively rigid and similar to the Leb conformation. The cyclic phosphate on the (3-galactopyranoside residue is in contact with the colitose residue linked to (3-GlcNAc.209 The capsular polysaccharide has been proposed as the basis for vaccine development.210... 

Cristae Tightly folded inner membranes of mitochondria where ATP is made. 

It is to be noted that the reflection assigned to the new phase in butyl branched alkanes is relatively weak compared to the reflections observed for the new phase in ethylene-1-octene copolymer (5.2 mol %). As explained in this chapter, we attribute the new phase to the crystallization of transient layer (butyl branches and fold surface). Considering the anticipated tight folds for butyl branched alkanes, the amount of crystallizable entities in the branched alkanes would be much less than in the ethylene-1-octene copolymers where the loose folds are expected. We would like to mention that, considering the d-value and intensity of the pseudo-hexagonal phase in branched alkanes, this reflection may be referred to as open-orthorhombic phase. 

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