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641.
642.
The vibrational spectra and structure of poly(rA-rU)-poly(rA-rU) 总被引:2,自引:0,他引:2
K Morikawa M Tsuboi S Takahashi Y Kyogoku Y Mitsui Y Iitaka G J Thomas 《Biopolymers》1973,12(4):799-816
Infrared and Raman spectra of aqueous poly(rA-rU)·poly(rA-rU), the double-helical complex containing strands of alternating riboadenylate and ribouridylate residues, display significant differences from one another and from corresponding spectra of poly(rA)·poly(rU), the double-helical complex of riboadenylate and ribouridylate homopolymers. Parallel studies on the copolymer and homopolymer complexes by cesium sulfate density gradient centrifugation, ultraviolet absorption spectroscopy, hydrogenion titration, 1-N oxidation of adenine residues by monoperphthalic acid and X-ray diffraction reveal, however, that the geometry of base pairing between adenine and uracil is closely similar in each complex and apparently of the Watson-Crick type. Therefore the differences observed between vibrational spectra of poly (rA-rU)·poly (rA-rU) and poly(rA)·poly(rU) are not due to different base-pairing schemes but may be attributed to differences in vibrational coupling between vertically stacked bases. Vibrational coupling may also account for the differences between infrared and Raman spectra of the same complex. Thus, the present results indicate that infrared and Raman frequencies of RNA in the region 1750–1550 cm?1 should be dependent on the base sequence. 相似文献
643.
Age-related changes in cell surfaces of human diploid fibroblasts (TIG-1) were investigated using the concanavalin A (ConA)-mediated red blood cell (RBC) adsorption assay. When ConA-coated RBCs were adsorbed to fibroblasts (RBC coating method), the amount of RBCs adsorbed per mg of fibroblast protein increased continuously from the early phases of cell passage up through cell senescence. On the other hand, when RBCs were adsorbed to ConA-coated fibroblasts (fibroblast coating method), RBC adsorption did not occur throughout phase II and increased with the advance of phase III. [3H]ConA binding to fibroblasts, however, did not change with aging to the extent that could explain the observed changes in RBC adsorption. These age-related characteristics in RBC adsorption and [3H]ConA binding were also observed for WI38 and IMR-90 cells. In addition, SV40- and 60Co-transformed WI38 cells showed a close resemblance in their RBC adsorption capacity to early phase III cells.RBC adsorption with both the RBC and fibroblast coating methods was not a function of cell cycle phase and time spent in culture (metabolic time). Co-culturing of young cells with old or transformed cells did not affect the RBC adsorption capacity of respective cells. These results suggest that RBC adsorption with the RBC and fibroblast coating methods may represent cell surface markers for division age and senescence of aging human diploid cells. 相似文献
644.