Folded flexible structure

Usually, crystallization of flexible-chain polymers from undeformed solutions and melts involves chain folding. Spherulite structures without a preferred orientation are generally formed. The structure of the sample as a whole is isotropic it is a system with a large number of folded-chain crystals distributed in an amorphous matrix and connected by a small number of tie chains (and an even smaller number of strained chains called loaded chains). In this case, the mechanical properties of polymer materials are determined by the small number of these ties and, hence, the tensile strength and elastic moduli of these polymers are not high. 

The spin-spin coupling constants [2-4] of the enkephalins in solution can be interpreted in terms of folded conformations resembling that of morphine in the placement of the residues which appear important for biological activity. X-ray crystallography and theoretical calculations (4-9) have also shown that methionine and leucine enkephalin adopt conformations similar to those concluded from NMR studies. Hence it would appear that opioid peptides can topographically resemble the opiates by assuming preferred, folded, conformations. However, earlier studies from this laboratory (TO) have shown that NMR data can be interpreted in terms of a conformationally flexible structure for methionine enkephalin. 

The selectivity of the interaction of Nef with the Hck-SH3 domain is based on the interaction that the RT loop of the SH3 domain can form by extending over the surface of Nef. The RT loop is a remarkably variable and flexible structure, which in Src kinases can be differentially stabilized by networks of hydrogen-bonding interactions, according to its particular sequence (121). These differences may at least in part account for the selectivity of the Nef-SH3 interaction by stabilizing a particular conformation of the loop necessary for an optimal interaction with Nef. The character of this interaction is hydrophobic the side chain of Ile-96 of the Fyn-SH3 R—>I mutant inserts into an exposed, remarkably hydro-phobic crevice between the aA and aB helices of Nef. A correlation exists between the character of residues contributing to this specificity pocket and the ability of HIV-1, HIV-2, or SIV to interact with different Src family SH3 domains (124). The importance of this interaction is confirmed by the selection of RT-loop mutants of the Hck-SH3 domain that bind to Nef with affinities up to 40-fold higher than those of parental... 

Flexible structure heated above Tgand compressed into folded shape... 

The linker region between the two chromophores has been studied extensively. When changing from monocationic to biscationic linkers, a 30-fold increase in potency was observed toward human cancer cell lines, while the potency against murine cell lines was unaltered. Symmetric and unsymmetric dimers were studied. No significant characters of the unsymmetric dimers were observed their potency was, as anticipated, between that of the corresponding two symmetric dimers. Variations in the linker flexibility, structure, and length were also studied. ... 

The flexibility of the SMP composite material is important for folding the structure into the spacecraft for transfer to space the folding temperature is highly dependent on both the resin and fibre properties. Once the structure is packed into its folded position, it is constrained in that position until cooled to approximately 15°C, or lower below Tg at which point the SMP composite structure will remain locked or frozen in the packed position umestrained until it is again heated above the Tg. When the SMP structure is heated, internal strain energy will cause it to return to its initial cured shape. The speed and the accuracy of the shape return are a function of the shape memory recovery force of the composite. 

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