Mononuclear ruthenium complexes and dinuclear Ru...Pd complexes having a series of 2,2'-bipyrimidine ligands, [(bpy)2Ru(Ln)]2+ [Ln = 2,2'-bipyrimidine (L1), 5,5'-dimethyl-2,2'-bipyrimidine (L2), 5,5'-dibromo-2,2'-bipyrimidine (L3), 4,4'-dimethyl-2,2'-bipyrimidine (L4), and 4,4',6,6'-tetramethyl- 2,2'-bipyrimidine (L5)] and [(bpy)2Ru(Ln)PdL]m+ [Ln = L1-L3; PdL = PdMeCl (m = 2) and PdMe(solvent) (m = 3)], are prepared, and the obtained complexes are characterized by means of spectroscopic and crystallographic methods. Introduction of the substituents on the bipyrimidine ligands led to the substantial differences in their electrochemical and photophysical properties. Density functional theory calculations have been performed to understand the substituent effect on the ground-state molecular orbital energy level. Reactivity studies on the catalytic dimerization of alpha-methylstyrene revealed that the Pd complex having a Br-substituted bipyrimidine ligand were much more active than those of the corresponding Pd complexes having methyl-substituted or nonsubstituted bipyrimidine ligands.

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The smectic liquid crystal arrangements of binary mixtures of rod-like polymers, i.e., poly[ndecyl-(S)-2-methylbutylsilane]s, with narrow molecular weight distributions, were investigated by synchrotron radiation small-angle X-ray scattering (SR-SAXS) and atomic force microscopy (AFM) analyses. Depending on the molecular weight ratio, r (higher molecular weight/lower molecular weight), and the mixing ratio, three types of smectic phases are formed with different accommodations by two polymers. In the binary mixture of the shorter and longer polymers with the lower r values of 1.0-1.7, the two polymers are randomly mixed within a layer, forming the conventional smectic A1 phase with a layer thickness corresponding to an average length of the two polymers. In contrast, when two kinds of polymers with the higher r values of 1.7-2.8 are mixed, different types of smectic A structures are formed. Upon the addition of the shorter polymer to the abundant longer polymer, a smectic A2 phase in which a pair of smectic layers of shorter polymers nested in a smectic layer of the longer polymers was first formed, and then converted into the smectic A3 phase in which the longer polymers randomly straddled a pair of smectic layers of the shorter polymers. These experimental results are discussed along with a comparison of the theoretical predictions.

Although widely used, DMSO is toxic for pancreatic islets. We combined hydroxyethyl starch (HES) with DMSO to simplify the procedure of freezing and thawing, and to decrease the toxicity of DMSO. A preclinical study was performed using islets from beagle dogs. After storage for 4 weeks, the islets were thawed and examined. The islet structure was well maintained after thawing. Although the number of the islets decreased to 71.2 +/- 20.1%, the function of the islets was evaluated by static incubation after thawing and showed a 1.80 +/- 0.78 stimulation index. We have introduced this technique for the cryopreservation of human islets from non-heart-beating donors. Twelve cases of human islet cryopreservation were performed. The sample tube of each human cryopreservation was thawed to evaluate the morphology, contamination, and endocrine function. Although fragmentation was observed in five samples (41.6%), the other seven (58.4%) showed a normal structure when evaluated by microscopic and electron microscopic study. The stimulation index (SI) of static incubation deteriorated from 3.37 +/- 3.02 to 1.34 +/- 0.28 after thawing. We divided the thawed islets into two groups: group 1 (n=8), SI > 1.2; group 2 (n=4), SI < 1.2. The group 1 islets showed a higher rate of normal structure (87%) than did group 2 (25%). Moreover, the SI before cryopreservation was 4.01 +/- 3.57 in group 1, which was higher than the SI of 2.11 +/- 0.72 in group 2. Based on the good results from the preclinical study using a large-animal model, this method was introduced for clinical application. Even from the pancreata of non-heart-beating donors, a successful islet cryopreservation was achieved. However, the isolated islets with poor function should not be cryopreserved for transplantation.