The effect of irregularity of chemical structure on melting points, densities and crystal structures was studied for 6-66 and 6-68 copolyamides. All copolyamides showed V-shaped melting point vs. composition curves. The densities, corrected for the difference in molecular weights between comonomers, also showed a minimum a t similar compositions with respect t o melting points. X-ray diffraction angles of the two main reflections, (200) and (202/002) in polyamide 6, and (100) and (110/010) in polyamides 66 and 68, respectively, approached in the copolymers. In melt-crystallized 6-66 copolyamides, the approach of the reflections was especially prominent, and the crystal structure of the copolyamide containing 30 mole-% of the 66 monomer was rather close to pseudo-hexagonal. The crystallites are transformed easily to the oc form by annealing in boiling water.

No abstract

Genomic in situ hybridization (GISH) was used to identify alien chromosomes in a series of eight different Allium fistulosum -A. cepa monosomic addition lines. Biotin-labeled total genomic DNA from shallot (A. cepa L. Aggregatum group) was used as a probe together with an excess amount of unlabeled blocking DNA from the recipient plant, Japanese bunching onion (A. fistulosum L.). Probe hybridization sites were detected by FITC-conjugated avidin and anti-avidin antibody using an epifluorescence microscope. In each mitotic metaphase cell of all the eight types of monosomic addition lines, the alien chromosomes were successfully discriminated from other 16 A. fistulosum chromosomes. Furthermore, no clear exchanges of chromosome segments between A. cepa and A. fistulosum were observed. This finding indicates that in each addition line an entire (unrecombined) A. cepa chromosome is present in an integral diploid background of A. fistulosum.

No abstract

No abstract