Scaling law for second-order hyperpolarizability in poly(triacetylene) molecular wires

Poly(triacetylenes) are rodlike molecules with electrons delocalized over a one-dimensional path. We show that they exhibit a power-law dependence of the second-order hyperpolarizability gamma on the monomer unit n for short molecules and a smooth saturation toward a linear increase in longer molecules. The power law of gamma?n(a) with a approximately 2.5 from dengenerate four-wave mixing and third-harmonic generation measurements is in good agreement with quantum-chemical calculations. The critical conjugation length for saturation in the three cases is shown to be approximately 60 carbon-carbon bonds, which indicates the upper boundary for the electron delocalization in such a one-dimensional molecular wire.     

Expanding the repertoire of natural product-inspired ring pairs for molecular recognition of DNA

A furan amino acid, inspired by the recently discovered proximicin natural products, was incorporated into the scaffold of a DNA-binding hairpin polyamide. While unpaired oligomers of 2,4-disubstituted furan amino acids show poor DNA-binding activity, furan (Fn) carboxamides paired with N-methylpyrrole (Py) and N-methylimidazole (Im) rings demonstrate excellent stabilization of duplex DNA as well as discrimination of noncognate sequences, consistent with function as a Py mimic according to the Py/Im polyamide pairing rules.     

Gram scale synthesis of 3-fluoro-1-hydroxyacetone phosphate: a novel donor substrate in rabbit muscle aldolase-catalyzed aldol reactions

An efficient gram scale synthesis of 3-fluoro-1-hydroxyacetone phosphate (FHAP) has been developed. As a close analog to dihydroxyacetone phosphate, FHAP was used as a novel donor substrate for rabbit muscle aldolase catalyzed reactions. The different binding affinities of the gem-diol and keto form of FHAP were studied by (19)F-NMR.     

A Bayesian analysis of the nucleon QCD sum rules

QCD sum rules of the nucleon channel are reanalyzed, using the maximum-entropy method (MEM). This new approach, based on the Bayesian probability theory, does not restrict the spectral function to the usual “pole + continuum” form, allowing a more flexible investigation of the nucleon spectral function. Making use of this flexibility, we are able to investigate the spectral functions of various interpolating fields, finding that the nucleon ground state mainly couples to an operator containing a scalar diquark. Moreover, we formulate the Gaussian sum rule for the nucleon channel and find that it is more suitable for the MEM analysis to extract the nucleon pole in the region of its experimental value, while the Borel sum rule does not contain enough information to clearly separate the nucleon pole from the continuum.