2-Aminotropones form fluorescent BODIPY analogues via N,O-chelation with quantum yield 0.16 and their structures are confirmed by X-ray studies.

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New PNA analogues derived from aminoethylpyrrolidin-5-one backbone show stabilization of aepone-PNA:DNA hybrids and destabilization of the corresponding RNA hybrids compared to unmodified PNA.

Study of self-assembly of PNA TC8 monitored by UV thermal transition at 295 nm indicates formation of a C-C+ tetraplex (i-motif) in acidic pH, with higher stability than the analogous dTC8.

Chalcogenated amino acids/peptides are recently being considered therapeutic drug candidates. This report describes a handy synthetic method for the Pd-catalyzed picolinamide directed site-selective C(sp2)-H chalcogenation of α- amino acids and...

Nucleic (DNA) acids having contiguous stretch of G sequence form quadruplex structure, which is very critical to control cell division. Recently the existence of G-quadruplex in RNA is also reported in presence of monovalent metal ion. PNA is a promising DNA analogue which binds strongly to DNA to form PNA:DNA duplex or PNA(2):DNA triplex. PNA also forms quadruplexes such G-quadruplex and i-motif in G and C-rich sequences respectively. aep-PNA containing a prolyl ring is one of several PNA analogues that provide rigidity and chirality in backbone and has binding affinity to natural DNA which is higher than that of PNA. Here we examine the ability of aep-PNA-G to form a quadruplex by UV, CD and mass spectroscopic techniques.

Isopentenyl diphosphate isomerase (IDI) catalyzes the interconversion of isopentenyl diphosphate (IPP) and dimethylallyl diphosphate (DMAPP), the basic five-carbon building blocks of isoprenoid molecules. Two structurally unrelated classes of IDI are known. Type I IPP isomerase (IDI-1) utilizes a divalent metal in a protonation-deprotonation reaction. In contrast, the type II enzyme (IDI-2) requires reduced flavin, raising the possibility that the reaction catalyzed by IDI-2 involves the net addition/abstraction of a hydrogen atom. As part of our studies of the mechanism of isomerization for IDI-2, we synthesized allene and alkyne substrate analogues for the enzyme. These molecules are predicted to be substantially less reactive toward proton addition than IPP and DMAPP, but have similar reactivities toward hydrogen atom addition. This prediction was verified by calculations of gas phase heats of reaction for addition of a proton and of a hydrogen atom to 1-butyne (3) and 1,2-butadiene (4) to form the 1-buten-2-yl carbocation and radical, respectively, and related affinities for 2-methyl-1-butene (5) and 2-methyl-2-butene (6) using G3MP2B3 and CBS-QB3 protocols. Alkyne 1-OPP and allene 2-OPP were not substrates for Thermus thermophilus IDI-2 or Escherichia coli IDI-1, but instead were competitive inhibitors. The experimental and computational results are consistent with a protonation-deprotonation mechanism for the enzyme-catalyzed isomerization of IPP and DMAPP.

Tropolone (2‐hydroxycyclohepta‐2,4,6‐triene‐1‐one and tautomer) is a non‐benzenoid bioactive natural chromophore with pH‐dependent fluorescence character and extraordinary metal binding affinities, especially with transition‐metal ions Cu2+/Zn2+/Ni2+. This report describes the syntheses and biophysical studies of a new tropolonyl thymidine [(4(5)‐hydroxy‐5(4)‐oxo‐5(4)H‐cyclohepta‐1,3,6‐trienyl)thymidine] (tr‐T) nucleoside and of corresponding tropolone‐conjugated DNA oligonucleotides that form B‐form DNA duplex structures with a complementary DNA strand, although their duplex structures are less stable than that of the control. Furthermore, the stabilities of those DNA duplex structures are lowered by the presence of increasing numbers of tr‐T residue or by decreasing pH of their environments. Most importantly, these duplex structures are made fluorescent because of the presence of the tropolone moieties conjugated to the thymidine residues. The fluorescence behavior of those duplex structures exhibits pH dependence, with stronger fluorescence at lower pH and weaker fluorescence at high pH. Importantly, the fluorescence characters of tr‐DNA oligonucleotides are significantly enhanced by nearly threefold after duplex structure formation with their complementary control DNA oligonucleotide. Further, the fluorescence behavior of these tr‐DNA duplex structures is also dependent on the pH conditions. Hence, tropolonyl‐conjugated DNA represents a class of new fluorescent analogues that might be be employed for sensing DNA duplex formation and provide opportunities to improve fluorescence properties further.