Thermodynamics of imidazole-ligand binding to Ni-nitrilotriacetate in solution and covalently attached to agarose beads: imidazole, his-6 (his-tag) peptide and a new bis-imidazolo-dithiane.

A new imidazolo- and thiol-containing ligand is prepared and characterized with the intent to serve as surrogate and mimic for the canonical ligands imidazole and hexa-histidinyl peptide (his-6) in immobilized metal affinity chromatography (IMAC) [1,2] systems. The affinity of this ligand: 1,8 bis (N1,N1')imidazolo-octa-(3,6)-dithiane or bImOdS, to Ni-nitrilotriacetic acid (Ni-NTA) complex in solution is measured and compared with that of imidazole and his-6 peptide via isothermal titration calorimetry (ITC). In addition, bImOdS is compared with his-6 binding to the solid-state matrix of Ni-NTA-charged agarose beads, as employed routinely in IMAC.

Transverse ionic mobility measured in a dynamic light scattering device.

We describe here some novel experiments with a commercial dynamic light scattering device. By inserting a quarter-wave plate in the light beam of the HeNe laser used in the Malvern DLS 'Zetasizer', one can obtain right handed (RH) or left-handed (LH) circularly polarized light from the incoming horizontally polarized laser light. This RH vs LH light is used in the ionic mobility (ζ-potential) measuring mode to detect what we believe are phenomena related to transverse ionic mobility, i.

DNA bending by charged peptides: electrophoretic and spectroscopic analyses.

We are testing the idea that placement of fixed charges near one face of the DNA double helix can induce DNA bending by a purely electrostatic mechanism. If stretching forces between DNA phosphates are significant, fixed charges should induce DNA bending by asymmetrically modulating these forces. We have previously tested this hypothesis by adding charged residues to small bZIP DNA binding peptides and monitoring DNA bending using electrophoretic phasing assays.

The binding of 1,8 ANS congeners to I-FABP and comparison of some hypotheses about ANS' spectral sensitivity to environment.

The ANS congeners 1-anilinonaphthalene and 1-amino,8-sulfonato naphthalene were investigated as analogs of 1,8 anilinonaphthalene sulfonate. Like 1,8 ANS, they also bind to I-FABP, and the fully-bound spectra reveal interesting similarities and differences with respect to ANS binding. The nature of these differences suggests that certain hypotheses in the literature about ANS photophysics ought to be revised.