Sequence-specific double-strand cleavage of DNA by penta-N-methylpyrrolecarboxamide-EDTA·Fe(II)

In the presence of O2 and 5 mM dithiothreitol, penta-N-methylpyrrolecarboxamide-EDTA·Fe(II) [P5E·Fe(II)] at 0.5 µ M cleaves pBR322 plasmid DNA (50 µ M in base pairs) on opposite strands to afford discrete DNA fragments as analyzed by agarose gel electrophoresis. High-resolution denaturing gel electrophoresis of a 32P-end-labeled 517-base-pair restriction fragment containing a major cleavage site reveals that P5E·Fe(II) cleaves 3-5 base pairs contiguous to a 6-base-pair sequence, 5'-T-T-T-T-T-A-3' (4,323-4,328 base pairs). The major binding orientation of the pentapeptide occurs with the amino terminus at the adenine side of this sequence. In the presence of 5 mM dithiothreitol, 0.01 µ M P5E·Fe(II) converts form I pBR322 DNA at 0.22 µ M plasmid (1.0 mM in base pairs) to 40% form II, indicating the cleavage reaction is catalytic, turning over a minimum of nine times. This synthetic molecule achieves double-strand cleavage of DNA (pH 7.9, 25 degrees C) at the 6-base-pair recognition level and may provide an approach to the design of "artificial restriction enzymes.

Comment on "Central limit behavior in deterministic dynamical systems"

We check claims for a generalized central limit theorem holding at the Feigenbaum (infinite bifurcation) point of the logistic map, made recently by U. Tirnakli, C. Beck, and C. Tsallis (Phys. Rev. {\bf 75}, 040106(R) (2007)). We show that there is no obvious way that these claims can be made consistent with high statistics simulations. We also refute more recent claims by the same authors that extend the claims made in the above reference.Comment: 3 pages, including 3 figure

Higgs bundles and the real symplectic group

We give an overview of the work of Corlette, Donaldson, Hitchin and Simpson leading to the non-abelian Hodge theory correspondence between representations of the fundamental group of a surface and the moduli space of Higgs bundles. We then explain how this can be generalized to a correspondence between character varieties for representations of surface groups in real Lie groups G and the moduli space of G-Higgs bundles. Finally we survey recent joint work with Bradlow, Garc\'ia-Prada and Mundet i Riera on the moduli space of maximal Sp(2n,R)-Higgs bundles.Comment: 12 page

Electroweak Fits and Constraints on the Higgs Mass

The current status of the quantities entering into the global electroweak fits is reviewed, highlighting changes since Summer 2003. These data include the precision electroweak properties of the Z and W bosons, the top-quark mass and the value of the electromagnetic coupling constant, at the scale of the Z boson mass. Using these Z and W (high Q^2) data, the value of the Higss mass is extracted, within the context of the Standard Model (SM). The consistency of the data, and the overall agreement with the SM, are discussed.Comment: 8 pages, 5 postscript figure