Biomedical subjects

Jack J J M Donners

Publications and source records attributed to Jack J J M Donners.

5 recordsLinked to original sources

PubMed2005

Coassembly of amphiphiles with opposite peptide polarities into nanofibers.

The design, synthesis, and characterization of "reverse" peptide amphiphiles (PAs) with free N-termini is described. Use of an unnatural amino acid modified with a fatty acid tail allows for the synthesis of this new class of PA molecules. The mixing of these molecules with complementary ones containing a free C-terminus results in coassembled structures, as demonstrated by circular dichroism and NOE/NMR spectroscopy. These assemblies show unusual thermal stability when compared to assemblies composed of only one type of PA molecule. This class of reverse PAs has made it possible to create biologically significant assemblies with free N-terminal peptide sequences, which were previously inaccessible, including those derived from phage display methodologies.

Alkylation↗

PubMed2004

Tuning intermolecular interactions in a rodlike polymer assembled at surfaces and in solution.

The isolation of single polyelectrolyte chains of water-soluble poly(isocyanodipeptide)s (PICs) bearing carboxylic acid terminated side chains occurring both at surfaces and in solution was accomplished by reducing the intermolecular interactions through complexation with cations or positively charged surfactants. Scanning force microscopy and viscosity analyses revealed that this method allows to tune the conformation of the macromolecule, which is of importance for tailoring the physicochemical properties of the material. This is particularly significant for the use of these polymer chains as seed for biomineralization processes.

Carboxylic Acids↗

PubMed2003

Self-assembly combining two bioactive peptide-amphiphile molecules into nanofibers by electrostatic attraction.

We describe a new approach to peptide-amphiphile (PA) nanofiber preparation that allows PAs with different bioactive amino acid sequences to be combined into a single fiber. Oppositely charged PAs are synthesized separately and then mixed to produce gels of nanofiber networks at physiological pH. Transmission electron microscopy reveals the formation of fibers approximately 7 nm in diameter and several micrometers long in these dimeric systems. On the basis of NMR and microscopy, we suggest that these nanofibers are cylindrical micelles of mixed composition, formed due to electrostatic attraction between the oppositely charged PAs. This strategy for self-assembly may be useful in cell therapies that can be implemented without invasive surgery or in in vitro tissue engineering.

Amino Acid Sequence↗

PubMed2002

A shape-persistent polymeric crystallization template for CaCO3.

Alanyl-alanine-derived poly(isocyanide)s possess a helical structure that persists even in aqueous media. These rigid macromolecules possess a regular distribution of carboxylic acid-terminated side chains which for the first time allows the study of the templating process involved in biomineralization using a shape-persistent polymeric template. It is demonstrated that in the case where the polymer derived from l-Ala-d-Ala is used the formation of apple core-type calcite crystals is controlled both by nucleation of the (01.1) face and subsequent adsorption of the polymer to the {hk.0} faces of the growing crystal. A small change in the secondary structure of the template that is introduced by using the polymer derived from l-Ala-l-Ala is directly reflected in the lower degree of control over the crystallization process.

Alanine↗

PubMed2002

Control over calcium carbonate phase formation by dendrimer/surfactant templates.

Poly(propylene imine) dendrimers that are modified with long alkyl chains self-assemble to form well-defined aggregates. The geometry and surface chemistry of the dendrimer assemblies can be varied through the addition of surfactants. These dendrimer/surfactant aggregates can be tuned to template the formation of the different phases of calcium carbonate. The use of octadecylamine results in the formation of polyhedral aggregates that become embedded within an amorphous calcium carbonate phase that persists in competition with the thermodynamic product, calcite. In combination with hexadecyltrimethylammonium bromide, small spherical aggregates are formed that induce the formation of vaterite. The use of the negatively charged surfactant SDS results in growth retardation by the Ca(2+)-induced agglomeration of dendrimer/surfactant aggregates into giant spherical particles. Eventually these particles become overgrown by rhombohedral calcite.

Calcium Carbonate↗