Although the mode of action of the ribosomes, the multi-component universal effective protein-synthesis organelles, has been thoroughly explored, their mere appearance remained elusive. Our earlier comparative structural studies suggested that a universal internal small RNA pocket-like segment called by us the protoribosome, which is still embedded in the contemporary ribosome, is a vestige of the primordial ribosome. Herein, after constructing such pockets, we show using the "fragment reaction" and its analyses by MALDI-TOF and LC–MS mass spectrometry techniques, that several protoribosome constructs are indeed capable of mediating peptide-bond formation. These findings present strong evidence supporting our hypothesis on origin of life and on ribosome's construction, thus suggesting that the protoribosome may be the missing link between the RNA dominated world and the contemporary nucleic acids/proteins life.
Modulation
of the H-bond basicity (pK
HB) of various
functional groups (FGs) by attaching fluorine functions
and its impact on lipophilicity and bioisosterism considerations are
described. In general, H/F replacement at the α-position to
H-bond acceptors leads to a decrease of the pK
HB value, resulting, in many cases, in a dramatic increase
in the compounds’ lipophilicity (log P
o/w). In the case of α-CF2H, we found
that these properties may also be affected by intramolecular H-bonds
between CF2H and the FG. A computational study of ketone
and sulfone series revealed that α-fluorination can significantly
affect overall polarity, charge distribution, and conformational preference.
The unique case of α-di- and trifluoromethyl ketones, which
exist in octanol/water phases as ketone, hemiketal, and gem-diol forms,
in equilibrium, prevents direct log P
o/w determination by conventional methods, and therefore, the
specific log P
o/w values of these
species were determined directly, for the first time, using Linclau’s 19F NMR-based method.
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Direct preparation of beta,beta-disubstituted C- and N-vinylindoles from condensation of aldehydes on indole derivatives is presented. Heating 1-methyl- and 1-benzylindole 3a,b with alkyl and aryl alpha-branched aldehydes and TFA in acetonitrile using microwave irradiation furnished 3-vinylindoles 1a-e in 18-76% yields. Under similar conditions, 3-substituted indoles 4a-c provided N-vinylindoles 2a-h in 16-98% yields.
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