Confirmation of the human thymidine kinase locus, 17q21 → 17qter,by means of a man-mouse somatic cell hybrid,D98/AH-2 X LMTK−Cl-1D

Summary A large metacentric marker chromosome, m20, in a line of human D98/AH-2 cells was identified by Q bands as being a translocation (1;17)(p36;q21). This was confirmed by means of somatic cell hybridization between D98/AH-2 and thymidine kinase (TK) deficient mouse cells. The hybrid clones by HAT selective system retained m20, indicating the presence of TK locus on this chromosome. The results also provide evidence that TK gene is located on the distal region of the breakpoint in 17q21 but not on 17q21 17pter.     

Development of microbodies in Candida tropicalis during incubation in a n-alkane medium

Development of microbodies in Candida tropicalis pK 233 was studied mainly by electron microscopical observation. The yeast cells, precultured on malt extract, scarcely contained microbodies and showed very low catalase activity. When the precultured cells were transferred to a n-alkane medium and incubated with shaking, the number of microbodies increased and concomitantly the activity of catalase was enhanced. That is, both the area ratio of microbodies in the cell and the ratio of microbodies to cytoplasm in area increased significantly during the utilization of n-alkanes for 8 hrs. Localization of catalase in the microbodies was demonstrated cytochemically by use of 3,3'-diaminobenzidine, but other organella in the cell, except for vacuoles appearing in the early growth phase and mitochondria, were not stained with this reagent. Microbodies seemed to grow by division. Biogenesis of microbodies in the yeast cells is also discussed.     

DNA strand scission by neocarzinostatin: molecular recognition process responsible for site-specificity

A series of hexanucleotides possessing A-T, G-C, inosine (I)-C and 2-aminoadenine (ANH2)-T base pairs at 5'-side of the target thymine were prepared and their selectivity for C-5' and C4' oxidation in the NCS-mediated degradation was investigated. Quantitative product analysis indicated that preferential C5' oxidation of deoxyribose moiety of the target T occurs at -5'-AT- and 5'-IT- sites, whereas C5' and C4' oxidation occurs competitively at T of -5'-GT- and -5'-ANH2T- sites. Based on the experimental results, an intercalation model that permits competitive hydrogen abstraction from C5' and C4' of deoxyribose moiety has been proposed.     

Oxygen concentration-dependent induction of a 140-kDa protein in magnetic bacterium Magnetospirillum magnetotacticum MS-1

Abstract The magnetic bacterium Magnetospirillum magnetotacticum prefers a microaerobic habitat and should be able to sense oxygen. Therefore, the bacterium was cultured under atmospheres containing 0–5% O₂ and analyzed for oxygen-dependent changes in the levels of its protein components by sodium dodecyl sulfate-polyccrylamide gel electrophoresis (SDS-PAGE). The analysis revealed a marked anaerobic induction of a 140-kDa protein, which was suppressed when M. magnetotacticum was switched from microaerobic (<1% O₂) to aerobic (>1% O₂) growth conditions. Although its function remains to be determined, the 140-kDa protein may serve as a useful tool to gain insight into the physiology of the organism.     

The transition in frequency of Y chromatin in males during the neonatal period

Summary The frequency of Y chromatin, visualized as fluorescent bodies in cell nuclei from lymphocytes in blood smears, was signficantly less in newborn males than in three-month-old male infants and adults. The frequency of Y chromatin-positive cells on day 0 was 36.16±9.11% and then increased daily. At one month after birth the frequency was 55.07±9.29%, which was not significantly different from that in adult males (57.08±5.97%).     

Analysis of the effects of snake venom proteinases on the activity of human plasma C1 esterase inhibitor, alpha 1-antichymotrypsin and alpha 2-antiplasmin

Incubation of C1 esterase inhibitor with Crotalid, Viperid and Colubrid snake venoms resulted in enzymatic inactivation of the inhibitor. Intact inhibitor (104 kDa) was converted into an active intermediate species of 89 kDa and then a further cleavage resulted in formation of an 86-kDa inactive inhibitor. In contrast, C1 esterase inhibitor did not lose activity during incubation with Elapid venoms; however, the intact inhibitor was gradually converted to an active species of 89 kDa during the incubation. Human alpha 1-antichymotrypsin was inactivated by all venoms tested, including those from the Elapid family. The 67-kDa intact inhibitor was converted by the venom proteinases to an inactive 63-kDa form. The results suggest that this acute-phase plasma protein is readily susceptible to inactivation by venom proteinases. Human alpha 2-antiplasmin (68 kDa) was cleaved to form a 61-kDa active intermediate, which then underwent a second cleavage to produce an inactive 53-kDa product. Elapid venoms had no effect on alpha 2-antiplasmin activity and did not cleave this inhibitor. All inhibitors were inactivated with catalytic amounts of venom proteinases. No stable proteinase-proteinase inhibitor complexes were detected, and no random proteolysis of the inhibitors occurred.     

Impact of Noncovalent Sulfur–Fluorine Interaction Position on Properties,Structures, and Photovoltaic Performance in Naphthobisthiadiazole‐Based Semiconducting Polymers

Controlling the energetics and backbone order of semiconducting polymers is essential for the performance improvement of polymer‐based solar cells. The use of fluorine as the substituent for the backbone is known to effectively deepen the molecular orbital energy levels and coplanarize the backbone by noncovalent interactions with sulfur of the thiophene ring. In this work, novel semiconducting polymers are designed and synthesized based on difluoronaphthobisthiadiazole (FNTz) as a new family of naphthobisthiadiazole (NTz)–quaterthiophene copolymer systems, which are one of the highest performing polymers in solar cells. The effect of the fluorination position on the energetics and backbone order is systematically studied. It is found that the dependence of the solar cell fill factor on the active layer thickness is very sensitive to the fluorination position. It is thus further investigated and discussed how the structural features of the polymers influence the photovoltaic parameters as well as the diode characteristics and bimolecular recombination. Further, the polymer with fluorine on both the naphthobisthiadiazole and quaterthiophene moieties exhibits a quite high power conversion efficiency of 10.8% in solar cells in combination with a fullerene. It is believed that the results would offer new insights into the development of semiconducting polymers.