Interactions between DNA and a Pyrene-Labeled Surfactant Probed by Pyrene Excimer Formation, Transmission Electron Microscopy, and Dynamic Light Scattering.

The interactions between calf thymus DNA and a pyrene-labeled gemini surfactant termed PyO-3-12 were investigated by using dynamic light scattering (DLS), transmission electron microscopy (TEM), and pyrene excimer formation (PEF) between an excited and a ground-state pyrene. PyO-3-12 was prepared with two dimethylammonium bromide headgroups linked with a propyl spacer, with one ammonium bearing a dodecyl tail and the other bearing a 1-pyrenemethoxyhexyl pendent. The size and electrostatic properties of the colloidal species were characterized by DLS, and TEM was used to describe the overall dimensions and morphologies of the aggregates.

Characterization of the Interactions between an Unassociated Cationic Pyrene-Labeled Gemini Surfactant and Anionic Sodium Dodecyl Sulfate.

The gemini surfactant PyO-3-12, made of two dimethylammonium bromides joined by a propyl linker and bearing a dodecyl pendant on one side and a 1-pyrenemethoxyhexyl group on the other side, was employed to probe the interactions between positively charged PyO-3-12 and negatively charged sodium dodecyl sulfate (SDS). PyO-3-12 was selected for its ability to respond to the polarity of its local environment through the fluorescence intensity ratio / of the first-to-third fluorescence peaks of the pyrene monomer and the local pyrene concentration [] through the / ratio of the pyrene excimer-to-pyrene monomer fluorescence intensity. Furthermore, analysis of the fluorescence decays of aqueous solutions of PyO-3-12 and SDS yielded a measure of the internal dynamics, local concentration, and state (associated vs unassociated) of PyO-3-12 in solution.

Synthesis and Characterization of a Pyrene-Labeled Gemini Surfactant Sensitive to the Polarity of Its Environment.

The cationic gemini surfactant PyO-3-12 was designed to include two dimethyl ammonium groups, one dodecyl tail, and 1-pyrenemethyl hexyl ether tail into the structure of the surfactant. The pyrenyl label ensured that the fluorescence of pyrene could be employed to probe the behavior of PyO-3-12 at the molecular level. The introduction of the oxygen atom in the β-position to pyrene was found to be critical for restoring the sensitivity of the pyrenyl label to the polarity of its environment.

Determination of the Aggregation Number of Pyrene-Labeled Gemini Surfactant Micelles by Pyrene Fluorescence Quenching Measurements.

A cationic gemini surfactant referred to as Py-3-12 and composed of two alkylated diammonium bromide head groups, a propyl spacer, and dodecyl and 1-pyrenehexyl hydrophobic tails was synthesized. Its critical micellar concentration (CMC) was determined to equal 0.15 (±0.

Gd-Complexes of New Arylpiperazinyl Conjugates of DTPA-Bis(amides): Synthesis, Characterization and Magnetic Relaxation Properties.

Two new DTPA-bis(amide) based ligands conjugated with the arylpiperazinyl moiety were synthesized and subsequently transformed into their corresponding Gd(III) complexes 1 and 2 of the type [Gd(L)H2O]·nH2O. The relaxivity (R1) of these complexes was measured, which turned out to be comparable with that of Omniscan®, a commercially available MRI contrast agent. The cytotoxicity studies of these complexes indicated that they are non-toxic, which reveals their potential and physiological suitability as MRI contrast agents.