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In order to make clear the structural role of the C-terminal amide group of endomorphin-2 (EM2, H-Tyr-Pro-Phe-Phe-NH₂), an endogenous µ-receptor ligand, in the biological function, the solution conformations of endomorphin-2 and its C-terminal free acid (EM2OH, H-Tyr-Pro-Phe-Phe-OH), studied using two-dimensional ¹H NMR measurements and molecular modeling calculations, were compared. Both peptides were in equilibrium between the cis and trans isomers around the Tyr-Pro ω bond in a population ratio of ≈ 1 : 2. The lack of significant temperature and concentration dependence of NH protons suggested that the NMR spectra reflected the conformational features of the respective molecules themselves. Fifty possible 3D structures for the each isomer were generated by the dynamical simulated annealing method under the proton-proton distance constraints derived from the ROE cross-peaks. These energy-minimized conformers, which were all in the φ torsion angles estimated from J_NHCαH coupling constants within ± 30°, were then classified in groups one or two according to the folding backbone structures. All trans and cis EM2 conformers adopt an open conformation in which their extended backbone structures are twisted at the Pro²-Phe³ moiety. In contrast, the trans and cis conformers of EM2OH show conformational variation between the 'bow'-shaped extended and folded backbone structures, although the cis conformers of its zwitterionic form are refined into the folded structure of the close disposition of C- and N-terminal groups. These results indicate clearly that the substitution of carboxyl group for C-terminal amide group makes the peptide flexible. The conformational requirement for µ-receptor activation has been discussed based on the active form proposed for endomorphin-1 and by comparing conformational features of EM2 and EM2OH.

The morphology and properties of multicomponent polymers based on polystyrene/polyarylate blockcopolymers (PS–b–PAr) are investigated. The PS–b–PAr molecule was synthesised by a novel procedure using carboxy terminated polystyrene. The architectures of the PS–b–PAr copolymers were predicted by a kinetic simulation model. Based on the results of the simulation and analysis of morphology, both the optical and mechanical properties of the PS–b–PAr are explained. The domain size, which dominates the transparency, was found to be sensitive to the purity of the block copolymer, while the birefringence was determined not only by the PS/PAr ratio but also by the length of each segment. On the basis of the experimental analyses, conditions were designed for the synthesis of PS–b–PAr copolymers with high transparency and low birefringence. The mechanical properties of the PS–b–PAr were controlled by modification of the miscibility between the PS and PAr segments. Acrylonitrile was introduced into the PS chain as a miscibility modifier. The volume fraction of the interfacial layer increased with the increase in miscibility. In particular, around the acrylonitrile concentration at which the miscibility reaches a maximum, the flexural strength was dramatically improved, changing the fracture behaviour from brittle to ductile. Furthermore, the PS–b–PAr copolymer was used as a compatibiliser for several immiscible polymer blend systems, including high impact polystyrene–polycarbonate and polyamide 6–acrylonitrile/butadiene/styrene. In these applications the PAr unit was used not as a macromolecular anchor but as a reactive unit. The experimental results showed that PS–b–PAr could compatibilise these blend systems effectively via an in situreaction between the PAr chain and either polycarbonate or polyamide 6 during the melt mixing process.

Pancreatic tissue from 20 horses was examined using immunocytochemical techniques. In aged horses, neogenesis of endocrine cells, neoformation, and hyperplasia of islets occurred closely associated with the pancreatic duct; these changes were regarded as nesidioblastosis. In addition, pancreatic fibrosis accompanied by ductal proliferation and endocrine neogenesis was considered a regenerative change. Thus, the origin of neoformation in the endocrine pancreas was in the ductal system, and it is suggested that the pancreatic endocrine cells were of endodermal origin.

A new simple analytical method for radial magnetic pull force in salient pole machines with eccentric rotors is presented. Calculation results are verified by experiments. As this method presents the precise calculation of flux density in the air gap of the entire circumference and the saturation effect of magnetization, the estimation of radial magnetic pull has been improved.

A precise analysis of temperature distribution in strands of a stator coil of a rotating machine with one turn coil is presented. The analysis includes effects of severe unbalanced distribution of current. The result of calculation is verified by the experiment, and by simulations, the effect of clamping pressure of stator core and the effect of the direction of cooling air flow are also studied.

DnaA protein, the initiation factor for chromosomal DNA replication in Escherichia coli, is activated by binding to ATP. We earlier reported that 3-acetoxy-2,2'-bi-1H-indol inhibited the ATP binding to DnaA protein (Sasaki, S., Mizushima, T., Hashimoto, T., Maeda, M., and Sekimizu, K. (1994) Bioorg. Med. Chem. Lett. 4, 1771-1774). In the present study, derivatives of 3-acetoxy-2,2'-bi-1H-indol with different lengths of aliphatic chains at the 3-O position were synthesized, and their potential to inhibit the ATP binding to DnaA protein was examined. Elongation of the aliphatic chain resulted in inhibition of the ATP binding to DnaA protein at lower concentrations. Among the derivatives, 3-[N-(11-carboxyundecyl)]carbamoylmethoxy-2,2'-bi-1H-indol (structure 7 (3-CUCM-BI)) exhibited the most potent inhibition with an IC50 value of 7 microM. The mode of the inhibition was competitive. We further demonstrated that structure 7 (3-CUCM-BI) inhibited DNA replication of the oriC plasmid in a system reconstituted from purified proteins. This inhibition was specific for the initiation of DNA replication rather than for the elongation. The inhibition was overcome by preincubation of DnaA protein with ATP. Furthermore, structure 7 (3-CUCM-BI) showed little inhibition on DNA synthesis in the ABC primosome system. We propose that structure 7 (3-CUCM-BI) functions in the in vitro oriC DNA replication by inhibiting the ATP binding to DnaA protein.

We isolated DNA clones of intracisternal A-particle (IAP) genes from the genome of an Asian wild mouse, Mus caroli. A typical M. caroli IAP gene was 6.5 kilobase pairs in length and had long terminal repeat (LTR) sequences at both ends. The size of the LTR was 345 base pairs in clone L20, and two LTRs at both ends of this clone were linked to directly repeating cellular sequences of 6 base pairs. Each LTR possessed most of the structural features commonly associated with the retrovirus LTR. The restriction map of the M. caroli IAP gene resembled that of Mus musculus, although the M. caroli IAP gene was 0.4 kilobase pairs shorter than the M. musculus IAP gene in two regions. Sequence homology between the M. caroli and M. musculus IAP LTRs was calculated as about 80%, whereas the LTR sequence of the Syrian hamster IAP gene was about 60% homologous to the M. caroli LTR. The reiteration frequency of the M. caroli IAP genes was estimated as 200 to 400 copies per haploid genome, which is at least 10 times the reported value. These results suggest that the IAP genes observed in the genus Mus are present in multiple copies with structures closely resembling the integrated retrovirus gene.

In order to elucidate the key atoms and/or stereostructures necessary for the inhibitory emergence of aldose reductase, crystal structure determinations were carried out for 11 oxazolecarbamate analogues, which have similar chemical and physicochemical properties but different inhibitory activities. The molecular conformations, revealed by X-ray analyses, were also ascertained to be energetically stable from theoretical conformational energy calculations. A surprising degree of conformational similarity was observed for the potent inhibitors. The analyses of the quantitative structure--activity relationships showed that the molecular conformation and the dipole moment, as well as the hydrophobicity at the oxazole C5-site, were important for high activity.