Unusual sequence effects on nucleotide excision repair of arylamine lesions: DNA bending/distortion as a primary recognition factor.

The environmental arylamine mutagens are implicated in the etiology of various sporadic human cancers. Arylamine-modified dG lesions were studied in two fully paired 11-mer duplexes with a -G*CN- sequence context, in which G* is a C8-substituted dG adduct derived from fluorinated analogs of 4-aminobiphenyl (FABP), 2-aminofluorene (FAF) or 2-acetylaminofluorene (FAAF), and N is either dA or dT. The FABP and FAF lesions exist in a simple mixture of 'stacked' (S) and 'B-type' (B) conformers, whereas the N-acetylated FAAF also samples a 'wedge' (W) conformer.

Structural mechanism associated with domain opening in gain-of-function mutations in SHP2 phosphatase.

The SHP2 phosphatase plays a central role in a number of signaling pathways were it dephosphorylates various substrate proteins. Regulation of SHP2 activity is, in part, achieved by an intramolecular interaction between the PTP domain of the protein, which contains the catalytic site, and the N-SH2 domain leading to a "closed" protein conformation and autoinhibition. Accordingly, "opening" of the N-SH2 and PTP domains is required for the protein to become active.

Nearest-neighbor nonparametric method for estimating the configurational entropy of complex molecules.

A method for estimating the configurational (i.e., non-kinetic) part of the entropy of internal motion in complex molecules is introduced that does not assume any particular parametric form for the underlying probability density function.

Estimation of the absolute internal-rotation entropy of molecules with two torsional degrees of freedom from stochastic simulations.

A method of statistical estimation is applied to the problem of evaluating the absolute entropy of internal rotation in a molecule with two torsional degrees of freedom. The configurational part of the entropy is obtained as that of the joint probability density of an arbitrary form represented by a two-dimensional Fourier series, the coefficients of which are statistically estimated using a sample of the torsional angles of the molecule obtained by a stochastic simulation. The internal rotors in the molecule are assumed to be attached to a common frame, and their reduced moments of inertia are initially calculated as functions of the two torsional angles, but averaged over all the remaining internal degrees of freedom using the stochastic-simulation sample of the atomic configurations of the molecule.

Application of molecular dynamics simulations to spin-labeled oligonucleotides.

The EPR study of spin labeled macromolecules has provided insight into structural and dynamical properties of DNA, proteins, and related systems. While spin labeling has been useful, it is experimentally difficult to determine if the spin label significantly alters the conformation of the macromolecule to which it is attached. Molecular modeling has proven to be a powerful tool for studying structure and dynamics of biologically important molecules.

Probing triplex formation by EPR spectroscopy using a newly synthesized spin label for oligonucleotides.

Spin labels have been extensively used to study the dynamics of oligonucleotides. Spin labels that are more rigidly attached to a base in an oligonucleotide experience much larger changes in their range of motion than those that are loosely tethered. Thus, their electron paramagnetic resonance spectra show larger changes in response to differences in the mobility of the oligonucleotides to which they are attached.