PubMed Health⌕ Search

Biomedical subjects

Jeffrey D Hartgerink

Publications and source records attributed to Jeffrey D Hartgerink.

8 recordsLinked to original sources
PubMed2006

Self-assembly of peptide-amphiphile nanofibers: the roles of hydrogen bonding and amphiphilic packing.

The role of hydrogen bonding and amphiphilic packing in the self-assembly of peptide-amphiphiles (PAs) was investigated using a series of 26 PA derivatives, including 19 N-methylated variants and 7 alanine mutants. These were studied by circular dichroism spectroscopy, a variety of Fourier transform infrared spectroscopies, rheology, and vitreous ice cryo-transmission electron microscopy. From these studies, we have been able to determine which amino acids are critical for the self-assembly of PAs into nanofibers, why the nanofiber is favored over other possible nanostructures, the orientation of hydrogen bonding with respect to the nanofiber axis, and the constraints placed upon the portion of the peptide most intimately associated with the biological environment. Furthermore, by selectively eliminating key hydrogen bonds, we are able to completely change the nanostructure resulting from self-assembly in addition to modifying the macroscopic mechanical properties associated with the assembled gel. This study helps to clarify the mechanism of self-assembly for peptide amphiphiles and will thereby help in the design of future generations of PAs.

Amino Acid Sequence↗
PubMed2006

Modulation of peptide-amphiphile nanofibers via phospholipid inclusions.

In this communication, we illustrate a new method to modulate the chemical and mechanical properties of peptide-amphiphile nanofibers. Hydrogels containing a mixture of peptide-amphiphile and phospholipid were prepared and evaluated for their mechanical properties, peptide conformation, and nanostructure. It was found that the storage modulus achieved a maximum at 5 mol % phospholipid and that this coincided with the maximum beta sheet signal as observed by circular dichroism. Throughout the ratios of peptide-amphiphile to phospholipid tested, the storage modulus and peptide secondary structure were closely correlated indicating the coupling between molecular structure and macroscopic properties. The nanostructure of the composite fibers was assessed by vitreous ice cryo-TEM and found to be largely independent of the mixture ratio. These new findings will enhance the versatility of peptide-amphiphiles in nanostructured tissue engineering and drug delivery applications.

Cryoelectron Microscopy↗
PubMed2006

Short homodimeric and heterodimeric coiled coils.

In this communication, we discuss the design, synthesis, and characterization of four peptides which are able to self-assemble into five different homo- and heterodimeric alpha-helical coiled coils based on the pH of their environment. These peptides are very short, containing only 14 or 21 amino acids each, and illustrate the minimum requirements necessary to form dimeric coiled coils which are critical in a large number of biological and materials design applications.

Amino Acid Sequence↗
PubMed2006

Chain-length-dependent vibrational resonances in alkanethiol self-assembled monolayers observed on plasmonic nanoparticle substrates.

Alkanethiol self-assembled monolayers (SAMs) on gold exhibit a series of sharp resonances in their surface-enhanced Raman spectrum that depend dramatically on carbon chain length. This unusual behavior suggests a coupling of the gold-sulfur bond stretch with the longitudinal acoustic, "accordion", vibrations of the molecular alkane chain. A simple model of a one-dimensional chain attached to a surface quantitatively reproduces these previously unreported experimental observations in this important nanomaterial system.

Alkanes↗
PubMed2004

Covalent capture: a natural complement to self-assembly.

The utility of peptide self-assembly can be extended by covalent capture of these supramolecular materials. Disulfide bond formation, native chemical ligation, olefin metathesis, radical capture and oxidative lysine cross-linking have been used recently to help stabilize and characterize a variety of self-assembled peptides. These include natural peptides, proteins and protein mimics such as alpha-helical coiled coils, amyloid-like beta-sheet fibres, portions of p53, glutathione S-transferase and elastin as well as unnatural peptide constructs such as cyclic peptide nanotubes and cylindrical micelles of peptide amphiphiles.

Deamination↗
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

Peptide-amphiphile nanofibers: a versatile scaffold for the preparation of self-assembling materials.

Twelve derivatives of peptide-amphiphile molecules, designed to self-assemble into nanofibers, are described. The scope of amino acid selection and alkyl tail modification in the peptide-amphiphile molecules are investigated, yielding nanofibers varying in morphology, surface chemistry, and potential bioactivity. The results demonstrate the chemically versatile nature of this supramolecular system and its high potential for manufacturing nanomaterials. In addition, three different modes of self-assembly resulting in nanofibers are described, including pH control, divalent ion induction, and concentration.

Amino Acids↗