A new series of five-ring banana-shaped mesogens derived from isophthalaldehyde was synthesized and investigated. Some of the compounds exhibit a B 2 -B 4 dimorphism. The mesophases were characterized alternatively by optical methods, X-ray studies, and dielectric and electro-optical measurements.
We converted the small homodimeric four-helix bundle repressor of primer protein (Rop) into a monomeric four-helix bundle by introduction of connecting loops. Both left- and right-handed four-helix bundles were produced. The left-handed bundles were more stable and were used to introduce biologically interesting peptides in one of the loops.
The temperature and frequency dependence of their dielectric constants have been investigated for two dimers consisting of swallow-tailed terminal groups connected via siloxane central parts of di erent length. The results have been compared with those of the respective monomer. The central part contributes in di erent ways to the static dielectric constants in the isotropic phase. From relaxation measurements, it can be concluded that the reorientation process about the short axis of the terminal groups is comparable with the respective process in monomers. The relaxation frequencies as well as intensities are almost unin¯uenced by the siloxane part which suggests a very¯exible structure of such dimers. Unfortunately, the maintenance of the antiparallel arrangement of swallow-tailed parts of the dimers could not be proved because of insu cient material for experimental work on the SA phase.
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