Influencing factors and significance of organic and inorganic nitrogen isotopic compositions in lacustrine sedimentary rocks

Comprehensive nitrogen biogeochemical cycle has been reconstructed for representative lacustrine organic-rich sedimentary rock in China,namely the Triassic Yanchang Formation(YF,199–230 Ma)in Ordos and the Cretaceous Qingshankou Formation(QF,86–92 Ma)in Songliao basins,by evaluating the organic and inorganic nitrogen isotopic compositions rather than only organic or bulk nitrogen isotopic compositions.The results indicate that the nitrogen isotope values of bulk rock(δ^(15)N_(bulk))in the non-metamorphic stage are significantly different from that of kerogen,which challenge the conceptual framework of sedimentary nitrogen isotope interpretation.Theδ^(15)N_(bulk)from the YF and QF were lower than their respective the nitrogen isotope values of kerogen(δ^(15)N_(ker)),with offsets up to5.1‰,which have the inverse relationship for the metamorphosed rock.Thermal evolution did not significantly modify the d15N of bulk rock and kerogen.The d15N of sediments from the YF(δ^(15)N_(bulk),1.6‰–5.6‰)were lower than that of rock from the QF(δ^(15)N_(bulk),10.2‰–15.3‰).The nitrogen isotope values of silicate incorporated nitrogen(δ^(15)N_(sil))were slightly lower than those of the d15Nker in the YF and obviously lower for the QF.The fact that different nitrogen cycles occur in the YF and QF due to the different depositional redox conditions leads to different isotopic results.The YF water environment dominated by oxic conditions is not conducive to the occurrence of denitrification and anammox,and no abundant N2 loss leads to the relatively lightδ^(15)N_(bulk).In the stratified water for the QF,redox transition zone promotes denitrification and anammox,resulting in the heavyδ^(15)N_(bulk)of rock and promotes the DNRA,resulting in heavyδ^(15)N_(ker)and lowδ^(15)N_(sil).

Action mechanisms and research methods of tRNA-derived small RNAs

tRNA-derived small RNAs(tsRNAs),including tRNA-derived fragments(tRFs)and tRNA halves(tiRNAs),are small regulatory RNAs processed from mature tRNAs or precursor tRNAs.tRFs and tiRNAs play biological roles through a variety of mechanisms by interacting with proteins or mRNA,inhibiting translation,and regulating gene expression,the cell cycle,and chromatin and epigenetic modifications.The establishment and application of research technologies are important in understanding the biological roles of tRFs and tiRNAs.To study the molecular mechanisms of tRFs and tiRNAs,researchers have used a variety of bioinformatics and molecular biology methods,such as microarray analysis,real-time quantitative reverse transcription-polymerase chain reaction(qRT-PCR);Northern blotting;RNA sequencing(RNA-seq);cross-linking,ligation and sequencing of hybrids(CLASH);and photoactivatable-ribonucleoside-enhanced cross-linking and immunoprecipitation(PAR-CLIP).This paper summarizes the classification,action mechanisms,and roles of tRFs and tiRNAs in human diseases and the related signal transduction pathways,targeted therapies,databases,and research methods associated with them.