The evolution mechanism of intron length.

Within two years of their discovery in 1977, introns were found to have a positive effect on gene expression. Our result shows that introns can achieve gene expression and regulation through interaction with corresponding mRNA sequences. On the base of Smith-Waterman method, local comparing helps us get the optimal matched segments between intron sequences and mRNA sequences. Studying the distribution regulation of the optimal matching region on intron sequences of ribosomal protein genes about 27 species, we find that the intron length evolution processes beginning from 5' end to 3' end and increasing one by one structural unit, which comes up with a possible mechanism for the intron length evolution. The intron of structure units is conservative with about 60bp length, but the length of linker sequence between structure units changes a lot. Interestingly, distributions of the length and matching rate of optimal matched segments are consistent with sequence features of miRNA and siRNA. These results indicate that the interaction between intron sequences and mRNA sequences is a kind of functional RNA-RNA interaction. Meanwhile, the two kinds of sequences above are co-evolved and interactive to play their functions.

[Preparation and luminescence properties of nanomaterials TiO2-SiO2 doped with Eu3+].

In the present paper, the samples of nanomaterials TiO2-SiO2:Eu3+ with different proportion of Ti/Si were prepared with the sol-gel method, and influence of the proportion of Ti/Si on the luminescence properties of samples have was studied. The structure of the samples was examined by FTIR, indicating that the compound TiO2 and SiO2 reacted, forming the new chemical bond of Ti-O-Si. The TEM of samples show that TiO2-SiO2:Eu3+ are sphericity nanoparticles with monodispersion and uniform size of 35 nm. The samples were still anatase phase after annealing at 900 degrees C, which was studied by XRD and SAED, suggesting that the bond of Ti-O-Si was conducive to the stability of anatase phase. There will be isoelectronic trap as Si4+ enters the TiO2 lattice replacing some of the Ti4+ position, and this structure is conducive to transfering energy and improving the transition of Eu3+ (7F0 --> 5D2), which were found by excitation and emission spectra.

[Preparation and luminescent properties of CaMoO4:Tb3+].

The precursor of the sample CaMoO4:Tb3+ was prepared by the coprecipitation method. TG-DTA spectra show that there is, at 850 degrees C, an energy absorption peak, suggesting that the sample reaches the activation spot of its response. The XRD pattern of the roasted sample shows that CaMoO4:Tb3+, in the single phase, is a representative scheelite structure of CaMoO4, but the peaks shift toward right, implying that tiny crystal defect in the crystal is produced. The defect is likely to be formed by the formation of the holes as two Tb3+ replace three Ca2+ in a cell. The excitation and emission spectra of the sample were investigated and revealed that the defect structure of the sample is in favor of the energy transfer of the characteristic peak (488 nm) of the MoO4(2-) effectively to Tb3+, and makes the 4f electrons of the Tb3+ transit, especially the (7)F6-->(5)D4 electronic transition (488 nm) of the Tb3+, to be greatly strengthened. As a result, the emission spectra with lamdaex=488 nm show that the emission intensity of the spontaneously activated fluorescence MoO4(2-) is greatly weakened, while the green light luminescence intensity of the (5)D4-->(7)F5 transition (544 nm) of the Tb3+ is greatly enhanced. This suggests that the sample CaMoO4:Tb3+ will become the luminescence material with potentially great application value.