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Abstract Background Even after years of exploration, the terrestrial origin of bio-molecules remains unsolved and controversial. Today, observation of amino acid composition in proteins has become an alternative way for a global understanding of the mystery encoded in whole genomes and seeking clues for the origin of amino acids. Results In this study, we statistically monitored the frequencies of 20 alpha-amino acids in 549 taxa from three kingdoms of life: archaebacteria, eubacteria, and eukaryotes. We found that the amino acids evolved independently in these three kingdoms; but, conserved linkages were observed in two groups of amino acids, (A, G, H, L, P, Q, R, and W) and (F, I, K, N, S, and Y). Moreover, the amino acids encoded by GC-poor codons (F, Y, N, K, I, and M) were found to "lose" their usage in the development from single cell eukaryotic organisms like S. cerevisiae to H. sapiens, while the amino acids encoded by GC-rich codons (P, A, G, and W) were found to gain usage. These findings further support the co-evolution hypothesis of amino acids and genetic codes. Conclusion We proposed a new chronological order of the appearance of amino acids (L, A, V/E/G, S, I, K, T, R/D, P, N, F, Q, Y, M, H, W, C). Two conserved evolutionary paths of amino acids were also suggested: A→G→R→P and K→Y.

Imidazopyridines, benzimidazoles and their derivatives are important heterocyclic substances with a wide range of future applications in the field of fluorescent sensors due to their excellent solid-state luminescence properties, long fluorescence lifetimes, and large Stokes shifts. Two 3-phenylimidazo[1,5-a]pyridines and two 2-phenyl-1H-benzo[d]imidazoles were synthesized and spectroscopically characterized by NMR spectroscopy and fluorescence spectroscopy analysis. The molecular structures and crystal stacking properties of three types of compounds, namely, imidazo[1,2-a]pyridine, imidazo[1,5-a]pyridine and benzimidazole, have been investigated by single-crystal X-ray diffraction analysis, and the results show that the different positions of the N atoms affect the stacking of the crystals, whereas the molecules are connected mostly through intermolecular π–π stacking and C–H⋯N and C–H⋯π interactions. Tight π-stacking contacts lead to a decrease in the fluorescence quantum yield of the molecules. Also, the shortened distance between imidazolepyridine or benzimidazole units and the strong aromatic interactions from polar substituents lead to solid-state fluorescence quenching. With the help of Hirshfeld surface analysis and electrostatic potential analysis, the roles of various noncovalent forces including hydrogen bonding, π-stacking, and C–H⋯π interactions in the formation of solid-state molecules are elucidated. The redshift of the emission spectra in solution with increasing solvent polarity and the apparent separation of the electron cloud densities between the HOMO and LUMO orbitals suggest that all seven compounds are typical intramolecular charge transfer (ICT) molecules. The HOMO–LUMO energy gap results are consistent with the fluorescence emission behavior of the compounds in solution and solid states. [ABSTRACT FROM AUTHOR]

An efficient I2 (10 mmol %)/H2O2 mediated oxidative formal [4+1] cyclization of 2‐pyridinemethylamine or o‐phenylenediamine (2‐aminobenzenethiol) with benzaldehyde via C−N bond formation has been developed. This strategy provides a straightforward approach to imidazo[1,5‐a]pyridines, iodo‐substituted imidazo[1,5‐a]pyridines and benzimidazole (benzothiazole) derivatives in yields ranging from 60 % to 98 %, respectively. Several heterocyclic products exhibit promising blue luminous performance with satisfactory fluorescence quantum yields of up to 64 %, large Stokes shifts, and a longer lifetime (7.35 ns). The band gap energies obtained from DFT are also consistent with the absorption spectra. [ABSTRACT FROM AUTHOR]

Cp2Fe-mediated electrochemical synthesis of a diverse array of phosphorylated azaspiro[4.5]di/trienones has been developed, which demonstrated broad substrate scope and good diastereoselectivity. It represents the first example of electrochemical synthesis of phosphorylated azaspiro[4.5]di/trienones, circumventing the need for external oxidants and high temperatures. Moreover, a plausible mechanism including radical-initiated dearomative cyclization driven by ferrocenium cations has been provided, which was supported by the related mechanistic study. [ABSTRACT FROM AUTHOR]

Gap junctional connection (GJC) in the cumulus–oocyte complex (COC) provides necessary support for message communication and nutrient transmission required for mammalian oocyte maturation. Cyclic adenosine monophosphate (cAMP) is not only a prerequisite for regulating oocyte meiosis, but also the key intercellular factor for affecting GJC function in COCs. However, there are no reports on whether cAMP regulates connexin 37 (Cx37) expression, one of the main connexin proteins, in sheep COCs. In this study, the expression of Cx37 protein and gene in immature sheep COC was detected using immunohistochemistry and PCR. Subsequently, the effect of cAMP on Cx37 expression in sheep COCs cultured in a gonadotropin-free culture system for 10 min or 60 min was evaluated using competitive ELISA, real-time fluorescent quantitative PCR (RT-qPCR), and Western blot. The results showed that the Cx37 protein was present in sheep oocytes and cumulus cells; the same results were found with respect to GJA4 gene expression. In the gonadotropin-free culture system, compared to the control, significantly higher levels of cAMP as well as Cx37 gene and protein expression were found in sheep COCs following treatment in vitro with Forskolin and IBMX (100 μM and 500 μM)) for 10 min (p < 0.05). Compared to the controls (at 10 or 60 min), cAMP levels in sheep COCs were significantly elevated as a result of Forskolin and IBMX treatment (p < 0.05). Following culturing in vitro for 10 min or 60 min, Forskolin and IBMX treatment can significantly promote Cx37 expression in sheep COCs (p < 0.05), a phenomenon which can be counteracted when the culture media is supplemented with RP-cAMP, a cAMP-specific competitive inhibitor operating through suppression of the protein kinase A (PKA). In summary, this study reports the preliminary regulatory mechanism of cAMP involved in Cx37 expression for the first time, and provides a novel explanation for the interaction between cAMP and GJC communication during sheep COC culturing in vitro. [ABSTRACT FROM AUTHOR]