Poly(β-amino ester)-DNA complexes: time-resolved fluorescence and cellular transfection studies.

A large number of different polymers have been developed and studied for application as DNA carriers for non-viral gene delivery, but the DNA binding properties are not understood. This study describes the efficiency of nanoparticle formation by time-resolved fluorescence measurements for poly(β-amino esters), cationic biodegradable polymers with DNA complexation and transfection capability. From the large library of poly(β-amino esters) ten polymers with different transfection efficacies were chosen for this study.

Study of PEGylated lipid layers as a model for PEGylated liposome surfaces: molecular dynamics simulation and Langmuir monolayer studies.

We have combined Langmuir monolayer film experiments and all-atom molecular dynamics (MD) simulation of a bilayer to study the surface structure of a PEGylated liposome and its interaction with the ionic environment present under physiological conditions. Lipids that form both gel and liquid-crystalline membranes have been used in our study. By varying the salt concentration in the Langmuir film experiment and including salt at the physiological level in the simulation, we have studied the effect of salt ions present in the blood plasma on the structure of the poly(ethylene glycol) (PEG) layer.

Role of polyplex intermediate species on gene transfer efficiency: polyethylenimine-DNA complexes and time-resolved fluorescence spectroscopy.

Polyethylenimine (PEI) is a cationic DNA condensing polymer that facilitates gene transfer into the mammalian cells. The highest gene transfer with branched PEI is obtained at high nitrogen/phosphate (N/P) ratios with free PEI present. The small molecular weight PEI alone is not able to mediate DNA transfection.

Langmuir-Schaeffer films from a pi-pi stacking perylenediimide dye: organization and charge transfer properties.

The organization of pi-pi stacking perylenediimide (PDI) derivative, PDI12, was studied in solution and in thin films. Films were prepared with the Langmuir-Schaeffer (LS) method and characterized by means of AFM, optical profilometry, steady-state absorption, emission, fluorescence lifetime, and transient photovoltage measurements. The columnar aggregates observed previously in PDI12 solutions and in spin-coated films persist also in LS films.

Self-assembled films of hydrophobin proteins HFBI and HFBII studied in situ at the air/water interface.

Hydrophobins are a group of surface-active fungal proteins known to adsorb to the air/water interface and self-assemble into highly crystalline films. We characterized the self-assembled protein films of two hydrophobins, HFBI and HFBII from Trichoderma reesei, directly at the air/water interface using Brewster angle microscopy, grazing-incidence X-ray diffraction, and reflectivity. Already in zero surface pressure, HFBI and HFBII self-assembled into micrometer-sized rafts containing hexagonally ordered two-dimensional crystallites with lattice constants of 55 A and 56 A, respectively.

Time-resolved fluorescence spectroscopy reveals functional differences of cationic polymer-DNA complexes.

Cationic polymers bind DNA and form compacted nanoparticulates (i.e., polyplexes).

Nonlinear optical and structural properties of langmuir-blodgett films of thiohelicenebisquinones.

We provide a detailed investigation of the second-order nonlinear optical and structural properties of Langmuir-Blodgett (LB) films of nonracemic thiohelicenebisquinone (THBQ). We prepare both X- and Y-type films of different thicknesses and characterize them using optical second-harmonic generation and atomic-force microscopy (AFM). We find that the overall nonlinear properties of the samples are essentially independent of the film thickness and the deposition type and arise from susceptibility tensor components associated with chirality.

Self-assembled hydrophobin protein films at the air-water interface: structural analysis and molecular engineering.

Hydrophobins are amphiphilic proteins produced by filamentous fungi. They function in a variety of roles that involve interfacial interactions, as in growth through the air-water interface, adhesion to surfaces, and formation of coatings on various fungal structures. In this work, we have studied the formation of films of the class II hydrophobin HFBI from Trichoderma reesei at the air-water interface.

Advantages of polarized two-beam second-harmonic generation in precise characterization of thin films.

Polarized second-harmonic generation using two fundamental beams, instead of one, offers significant advantages for characterizing nonlinear optical thin films. The technique is more precise and allows the internal consistency of the results to be verified. The superiority of the two-beam arrangement over the traditional single-beam arrangement is demonstrated by determining the susceptibility tensors of Langmuir-Blodgett films.

A regression technique to analyze the second-order nonlinear optical response of thin films.

We present a new technique, based on regression analysis, to determine the second-order nonlinear optical susceptibility tensor of thin films. The technique does not require the absolute levels or phases of measured signals to be mutually calibrated. In addition it yields indicators that address the quality of theoretical models describing the sample.

Structural hierarchy in molecular films of two class II hydrophobins.

Hydrophobins are highly surface-active proteins that are specific to filamentous fungi. They function as coatings on various fungal structures, enable aerial growth of hyphae, and facilitate attachment to surfaces. Little is known about their structures and structure-function relationships.