Abstract Two experimental techniques—time domain spectroscopy (TDS) and a steady state frequency method—have been used to study dielectric spectra for the isotropic, nematic, SA, SC and SY phases of two thioesters (4-n-pentylphenyl-4′-n-octyloxy-and 4′-n-nonyloxythiobenzoates (C n H2n+1 O‒C6 H4‒COS‒C6H4‒C5H11, where n = 8 and n = 9) known as 8S5 and 9S5, in the frequency range from 10 Hz to 10 GHz. In the case of 8S5 a deuteriated sample (8S5-d 28) has been used to study relaxation processes in the nematic and smectic phases.
The cytoplasmic surface of bacteriorhodopsin is characterized by a group of carboxylates that function as a proton attractive domain [Checover, S., Nachliel, E., Dencher, N. A., and Gutman, M. (1997) Biochemistry 36, 13919−13928]. To identify these carboxylates, we selectively mutated them into cysteine residues and monitored the effects of the dynamics of proton transfer between the bulk and the surface of the protein. The measurements were carried out without attachment of a pH-sensor to the cysteine residue, thus avoiding any structural perturbation and change in the surface charge caused by the attachment of a reporter group, and the protein was in its BR state. The purple membranes were suspended in an unbuffered solution of pyranine (8-hydroxypyrene-1,3,6-trisulfonate) and exposed to a train of 1000 laser pulses (2.1 mJ/pulse, λ = 355 nm, at 10 Hz). The excitation of the dye ejected the hydroxyl's proton, and a few nanoseconds later, a pair of free protons and ground-state pyranine anion was formed. The experimental observation was the dynamics of the relaxation of the system to the prepulse state. The observed signals were reconstructed by a numeric method that replicates the chemical reactions proceeding in the perturbed space. The detailed reconstruction of the measured signal assigned the various proton-binding sites with rate constants for proton binding and proton exchange and the pK values. Comparison of the results obtained by the various mutants indicates that the dominant proton-binding cluster of the wild-type protein consists of D104, E161, and E234. The replacement of D104 or E161 with cysteine lowered the proton binding capacity of the cluster to ∼60% of that of the native protein. The replacement of E234 with cysteine disrupted the structure of the cluster, causing the two remaining carboxylates to function as isolated residues that do not interact with each other. The possibility of proton transfer between monomers is discussed.
One of the enabling technologies in long-term perspective for human space exploration is in-situ resource utilization (ISRU). When dealing with the prospect of future manned missions to Moon and Mars the use of ISRU seems useful and intended. The activities presented in this paper focus on lunar ISRU. This basically incorporates both the exploitation of lunar oxygen from indigenious rock and the extraction of solar wind implanted particles (SWIP) from regolith dust. Currently the the Institute of Astronautics (LRT) is examining possibilities for the extraction of SWIPs, which may provide several gaseous components (such as H2 and N2) valuable to a human presence on the Moon. This experiment, LUISE (LUnar ISru Experiment), will comprise a solar powered thermal process chamber for regolith heating. The proposed thermal extraction chamber uses an insulated double wall cavity receiver for heating, with regolith being filled into the gap between the two walls. The goal is to assess the thermal behavior of regolith within the process chamber. An experimental setup with two cylinders stacked into each other has been developed and built. Heating is accomplished by a molybdenum heater located within the inner cylinder. The overall setup is exposed to high vacuum during the complete heating run. With this simplified geometry we will heat several hundred grams of JSC-1A, a widely used lunar regolith simulant, to a temperature of 1000(^circ)C. The data gained during the testing is used to determine the influence of regolith layer thickness, thermal connection between the inner and outer wall of the cavity on the heating duration until steady state, power demand and overall heating homogeneity within the regolith.
Prepared in a three-step sequence including acid-catalysed cycloaddition of cyclopentadiene to 6-oxo-6H-1,3,4-oxadiazines, dehydrogenation with DDQ of the dihydro-α-pyrones formed and reduction of the resulting α-pyrones with DIBAL-H, 1,4-disubstituted cyclopenta[c]pyrans are shown to undergo electrophilic substitution; the molecular structures of 1-(4-anisyl)-4-phenylcyclopenta[c]pyran and 4-isopropyl-1-phenylcyclopenta[c]pyran-7-carbaldehyde have been determined by single crystal X-ray diffraction studies.
