Search results for "TYR"
showing 10 items of 2017 documents
Molecular aggregation in selected crystalline 1:1 complexes of hydrophobicD- andL-amino acids. IV. TheL-phenylalanine series
2009
The amino acid L-phenylalanine has been cocrystallized with D-2-aminobutyric acid, C(9)H(11)NO(2).C(4)H(9)NO(2), D-norvaline, C(9)H(11)NO(2).C(5)H(11)NO(2), and D-methionine, C(9)H(11)NO(2).C(5)H(11)NO(2)S, with linear side chains, as well as with D-leucine, C(9)H(11)NO(2).C(6)H(13)NO(2), D-isoleucine, C(9)H(11)NO(2).C(6)H(13)NO(2), and D-allo-isoleucine, C(9)H(11)NO(2).C(6)H(13)NO(2), with branched side chains. The structures of these 1:1 complexes fall into two classes based on the observed hydrogen-bonding pattern. From a comparison with other L:D complexes involving hydrophobic amino acids and regular racemates, it is shown that the structure-directing properties of phenylalanine closel…
Probe diffusion in homogeneous diblock copolymers
1998
Forced Rayleigh scattering was used to investigate the diffusion of a photoreactive dye molecule in two homogeneous poly(styrene-b-isoprene) (SI) diblock copolymers with overall molecular weights of approximately 2000. Although diffusion rates were intermediate to TTI transport in homopolymer polystyrene (PS) and polyisoprene (PI), system dynamics appear to be largely dictated in each case by the PI block. The size of the polymer jumping unit, on the other hand, is evaluated from a free-volume analysis of the data, and is found to be governed predominantly by the PS component of the copolymer. The mechanism for tracer diffusion in low-molecular-weight block copolymers appears analogous to t…
Tyramine action on motoneuron excitability and adaptable tyramine/octopamine ratios adjust Drosophila locomotion to nutritional state
2019
Adrenergic signaling profoundly modulates animal behavior. For example, the invertebrate counterpart of norepinephrine, octopamine, and its biological precursor and functional antagonist, tyramine, adjust motor behavior to different nutritional states. In Drosophila larvae, food deprivation increases locomotor speed via octopamine-mediated structural plasticity of neuromuscular synapses, whereas tyramine reduces locomotor speed, but the underlying cellular and molecular mechanisms remain unknown. We show that tyramine is released into the CNS to reduce motoneuron intrinsic excitability and responses to excitatory cholinergic input, both by tyraminehonoka receptor activation and by downstrea…
Biological effects of short-chain fatty acids in nonruminant mammals.
1993
propionate, volatile fatty acids (VFAs), cholesterol, cell prolifera tion, human gastric lipase
Towards storage-stable high-content recycled tyre rubber modified bitumen
2018
The addition of crumb rubber particles as bitumen modifier can be currently considered as a well-established alternative to conventional polymers for bitumen modification. However, Recycle Tyre Rubber (RTR) modified binders still present drawbacks such as poor mix workability and hot storage stability. Within this study the authors try unlocking the full potential of devulcanised tyre rubber-heavy oils blend, named Liquid Rubber (LR), by exploring the possibility of tailoring recycled polymer modified bitumen with unconventional high-content of RTR and designed to overcome the above mentioned technological problems of RTR modified bitumen while keeping its advantages. Results show that LR-b…
Molecular dynamics of solid polymers as revealed by deuteron NMR
1983
Pulsed deuteron NMR spectroscopy is described, which has recently been developed to become a powerful tool for studying molecular dynamics in solid polymers. It is shown that by analyzing the line shapes of2H absorption spectra and spectra obtained via solid echo and spin alignment, respectively, both type and timescale of rotational motions can be determined over an extraordinary wide range of characteristic frequencies, approximately 10 MHz to 1 Hz. By applying these techniques to selectively deuterated polymers, motional mechanisms involving different segments of the monomer unit can be monitored. In addition, motional heterogeneities in glassy polymers can be detected. The information a…
Cyclodextrins in Polymer Synthesis: Free Radical Copolymerization of Methylated β-Cyclodextrin Complexes of Hydrophobic Monomers with N-Isopropylacr…
2000
Methylated β-cyclodextrin (me-β-CD) was used to form water-soluble host/guest complexes with the hydrophobic monomers n-butyl methacrylate (1), cyclohexyl methacrylate (2), isobornyl acrylate (3), isobornyl methacrylate (4), and styrene (5), respectively. The free-radical copolymerizations of the water-soluble N-isopropylacrylamide (NIPAAm) with these complexed monomers were carried out in water at different molar ratios.
Nonionic Maleic Surfmers
2002
ABSTRACT A set of nonionic maleic surfactants have been prepared, all coming from the derivatization of maleic hemiesters with a long alkyl chain. They are either amidoesters or diester products. In the case of amidoesters, the acid group was first activated and then reacted with primary or secondary or tertiary ethanolamine compounds. In the case of diesters, the hemiester was reacted directly with glycidol, in acid or basic conditions. These surfactants were characterized for their structure by 1H NMR, and for their surface active properties, by surface tension measurements. They were also used in batch emulsion polymerisation of styrene, and seeded core-shell copolymerisation of a 1/1 mi…
Basis for the Preparative Fractionation of a Statistical Copolymer (SAN) with Respect to Either Chain Length or Chemical Composition
2003
The possibilities to fractionate copolymers with respect to their chemical composition on a preparative scale by means of the establishment of liquid/liquid phase equilibria were studied for random copolymers of styrene and acrylonitrile (SAN). Experiments with solutions of SAN in toluene have shown that fractionation does in this quasi-binary system, where demixing results from marginal solvent quality, take place with respect to the chain length of the polymer only. On the other hand, if phase separation is induced by a second, chemically different polymer, one can find conditions under which fractionation with respect to composition becomes dominant. This opportunity is documented for th…
Deuteron n.m.r. in relation to the glass transition in polymers
1985
Abstract 2H n.m.r. is introduced as a tool for investigating slow molecular motion in the glass transition region of amorphous polymers. In particular, we compare 2H spin alignment echo spectra of chain deuterated polystyrene with models for restricted rotational Brownian motion. Molecular motion in the polystyrene-toluene system has been investigated by analysing 2H n.m.r. of partially deuterated polystyrene and toluene, respectively. The diluent mobility in the mixed glass has been decomposed into ‘solid’ and ‘liquid’ components where the respective average correlation times differ by more than 5 decades.