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Investigates the helix packing in the lactose permease of Escherichia coli. Distances between site-directed nitroxides and a lanthanide; Substrate protection of Cys148 in lactose permease; Specific direction of a methanethiosulfonate nitroxide spin-label to one of two Cys residues in a double-Cys mutant; Nitroxide-nitroxide interactions.

Deals with a study which examined the tertiary contacts between helices V and VII, VIII or X using a general cross-linking approach in the lactose permease. Experimental procedures; Results of the study; Discussion of the results.

Highlights a study which explored the N-terminal six transmembrane helices and the C-terminal transmembrane helices of the lactose permease, containing a single-Cys residue. Methodology; Cross-linking permease with paired Cys residues in helices IV and VII; Ligand-induced changes in cross-linking.

Studies the N-terminal six transmembrane helices (N6) and the C-terminal six transmembrane helices (C6) of lactose permease. Methods of the study; Relationships between helices I and VII; Effect of ligand in N6/C6 permease containing paired Cys residues; Results of the study.

Presents a study on the expressing of lactose permease. Expression in polypeptide fragments containing the N-terminal (N6) and C-terminal (C6) transmembrane domains; Views on the stability of the N6 and C6; Ability of C6 to catalyze lactose translocation.

Presents a study on the identification of the epitope for monoclonal antibody 4B1 which uncouples lactose and proton translocation in the lactose permease of Escherichia coli. Demonstration that 4B1 binds specifically to the periplasmic loop between helices VII and VIII; High specific interactions involved in the uncoupling effect of 4B1.

Describes the findings of a study on Escherichia coli, with mutants of a single Cys residue in place of Phe27, Pro28, Phe29, Phe30 or Pro31 at the periplasmic end of putative transmembrame helix I to find out the interaction of lactose permease with ligand by site-directed chemical modification or fluorescence spectroscopy.

Describes the use of site-directed fluorescence labeling to provide more direct evidence for the contention that cysteine (Cys) 148 is located in a binding site in the lactose (lac) permease of Escherichia coli. Plasmid construction; Purification of biotinated lac permease with single Cys residues; Protein determinations; Fluorescence quenching studies.

Metathesis cyclopolymerization (MCP)of ionic 1,6-heptadiyne is successfully applied to synthesize polyacetylene(PA) ionomer in different solvents especially in imidazolium-basedionic liquid (IL), and MCP of ionic monomer in the mixture of THF/ILproceeded in a controlled manner by the action of Grubbs second andthird generation catalysts (Ru–II, Ru–III). The influence of catalysts and solvents on polymerization behaviorand chain microstructure was investigated, and the results revealedthat the isolated polymer yield could reach to 97% and 82% by Ru–IIIand Ru–II, respectively,in 1:2 THF/IL after optimization, and PAs incorporating imidazoliumpendent contained ≥95% five-membered-ring structure and almostall trans-double bonds along the backbone. PAs formedin different solvents reflected significant variance in optical absorptionproperties, and a bathochromic shift effect was observed with themixture of THF/IL. [ABSTRACT FROM AUTHOR]

The flow performanceof a high-viscosity fluid in novel staticmixers with multitwisted leaves was investigated numerically in therange of Re= 0.1–150. The effects of mixing-segmentconstruction, Reynolds number, and aspect ratio on the chaotic mixingcharacteristics of different static mixers were evaluated based onthe Lagrangian tracking method. The tracer particle distributions, Gvalues, extensional efficiency characteristics, and stretchingfields were used to evaluate the dispersion and distribution mixingperformances in the new static mixers. Compared with the Kenics staticmixer (KSM), the static mixers with three twisted leaves (TKSM) andfour twisted leaves (FKSM) achieved chaotic mixing status much earlierand could also maintain this status by successive mixing-element groups.In contrast, there were large unmixed zones in the static mixer withdouble twisted leaves (DKSM). Stretching rates calculated from pathlineswere found to be in good agreement with results reported in the literature.The particle trajectories revealed that the logarithm of the stretchingrate increased linearly with the dimensionless axial length. For agiven length of static mixer, a decrease in aspect ratio benefitedan increasing stretching rate. When the number of multitwisted leavesin the cross section was greater than 2, the range of the probabilitydensity curve became larger than that of the KSM. All of the staticmixers were found to have small groups of material points experiencingvery high stretching. The TKSM and FKSM were found to have highermixing efficiencies than the KSM, whereas the DKSM exhibited a worsemicromixing ability. [ABSTRACT FROM AUTHOR]