We have used the pH-induced self-assembly of a peptide-amphiphile to make a nanostructured fibrous scaffold reminiscent of extracellular matrix. The design of this peptide-amphiphile allows the nanofibers to be reversibly cross-linked to enhance or decrease their structural integrity. After cross-linking, the fibers are able to direct mineralization of hydroxyapatite to form a composite material in which the crystallographic c axes of hydroxyapatite are aligned with the long axes of the fibers. This alignment is the same as that observed between collagen fibrils and hydroxyapatite crystals in bone.

http://science.sciencemag.org/content/sci/294/5547/1684.full.pdf

Self-assembly and mineralization of peptide-amphiphile nanofibers

9-Fluorenylmethoxycarbonyl (Fmoc) amino acids were first used for solid phase peptide synthesis a little more than a decade ago. Since that time, Fmoc solid phase peptide synthesis methodology has been greatly enhanced by the introduction of a variety of solid supports, linkages, and side chain protecting groups, as well as by increased understanding of solvation conditions. These advances have led to many impressive syntheses, such as those of biologically active and isotopically labeled peptides and small proteins. The great variety of conditions under which Fmoc solid phase peptide synthesis may be carried out represents a truly "orthogonal" scheme, and thus offers many unique opportunities for bioorganic chemistry.

Solid phase peptide synthesis utilizing 9‐fluorenylmethoxycarbonyl amino acids

https://www.cell.com/cell/pdf/0092-8674(88)90262-0.pdf

Autonomous functional domains of chemically synthesized human immunodeficiency virus tat trans-activator protein.

One of the initial steps in the development of therapeutic agents is the identification of lead compounds that bind to the receptor or enzyme target of interest. Many analogs of these lead compounds are then synthesized to define the key recognition elements for maximal activity. In general, many compounds must be evaluated in both the lead identification and optimization steps. Increasing burdens have been placed on these efforts due to the large number of new therapeutic targets that continue to be identified thorough modern molecular biology methods.1 To address this demand, very powerful chemical and biological methods have been developed for the generation of large combinatorial libraries of peptides2 and oligonucleotides3 that are then screened against a receptor or enzyme to identify high-affinity ligands or potent inhibitors, respectively. While these studies have clearly demonstrated the power of library synthesis and screening strategies, peptides and oligonucleotides generally have poor oral activities and rapid in vivo clearance;4 therefore their utility as bioavailable therapeutic agents is often limited. Due to the favorable pharmacokinetic properties of many small organic molecules (<600-700 molecular weight),5 the design, synthesis, and evaluation of libraries of these compounds6 has rapidly become a major frontier in organic chemistry. Lorin A. Thompson was born in Lexington, KY, in 1970. He received the Bachelor of Science degree from the University of North Carolina, Chapel Hill, in 1992 where he worked under the guidance of Joseph Desimone. He is currently pursuing his doctorate in the laboratory of Jonathan Ellman at UC Berkeley where he is the 1994 Glaxo-Wellcome fellow. His research interests include the development of synthetic methodology for organic library construction.

/pdf/synthesis-and-applications-of-small-molecule-libraries-3n3gol8dyk.pdf

Synthesis and Applications of Small Molecule Libraries.

A convenient and versatile approach to the direct synthesis of a peptide-antigen matrix by the solid-phase method is described. The approach is called the multiple antigen peptide system (MAP) and it utilizes a simple scaffolding of a low number of sequential levels (n) of a trifunctional amino acid as the core matrix and 2n peptide antigens to form a macromolecule with a high density of peptide antigens of final Mr 10,000. The MAP model chosen for study was an octa-branching MAP consisting of a core matrix made up of three levels of lysine and eight amino terminals for anchoring peptide antigens. The MAP, containing both the core matrix and peptides of 9-16 amino acids, was prepared in a single synthesis by the solid-phase method. Six different MAPs elicited specific antibodies in rabbits and mice, of which five produced antibodies that reacted with their corresponding native proteins. In rabbits, the sera had a considerably higher titer of antibodies than sera prepared from the same peptides anchored covalently to keyhole limpet hemocyanin as carrier. Thus, the MAP provided a general, but chemically unambiguous, approach for the preparation of carrier-bound antigens of predetermined and reproducible structure and might be suitable for generating vaccines.

https://www.pnas.org/content/pnas/85/15/5409.full.pdf

Synthetic peptide vaccine design: synthesis and properties of a high-density multiple antigenic peptide system

Quantitative monitoring of solid-phase peptide synthesis by the ninhydrin reaction.

Peptide-resins containing linear peptides up to 6000 molecular weight-were prepared by stepwise solid-phase synthesis of the repeating model sequence Leu-Ala-Gly-Val-oxymethylphenylacetic acid on copoly(styrene-l% divinylbenzene) resin beads. Initial substitutions of 0.22 and 0.95 mmol/g of polystyrene were used and the resulting peptide-resins contained 11-81% peptide. Representative samples were taken after the addition of each model sequence unit and the diameters of the dry beads were measured by direct microscopic examination. The volume of 1 g of the unsubstituted dry beads was 1.0 mL and was found to increase by more than fivefold as the peptide content approached 80%. Similar measurements of the samples in CH2Cl2 or DMF showed that the swollen volumes of 1 g of the unsubstituted beads were 6.2 and 3.3 mL, respectively. The volumes of the swollen peptide-resins showed a dramatic increase in the course of the synthesis, and at 80% peptide the volumes/g of polystyrene were 12 mL in CH2Cl2 and 28 mL in DMF. There was no indication that the upper limits of swelling of the peptide-containing resin had been reached. The solvation properties of the cross-linked polymer network and the pendant peptide chains mutually affect one another and at high loadings of peptide in a solvent such as DMF the peptide component has a dominating influence on the swelling of the peptide-resin beads. The swelling of the unsubstituted resin is due to a decrease in free energy from solvation of the polystyrene and, at equilibrium, is balanced by the elastic restraining force resulting from deformation of the loosely cross-linked polymer network. The increased swelling of the peptide-resin can then be attributed to the additional net decrease in free energy from solvation of the linear peptide chains, which is counteracted by an increase in the elastic restraining force arising from further deformation of the loosely cross-linked network structure of the polymer support. No such additional counterforce is expected to arise from deformation of the linear peptide chain imposed by the expansion of the polymeric support. In either CH2Cl2 or DMF, the space available for peptide chain growth within the swollen resin beads is not a limiting factor in solid-phase peptide synthesis. After the synthesis of the 60-residue model there was actually more space within the bead for chain growth than at the beginning of the synthesis. The results of this study allow a rational choice of the level of loading of peptide on the resin and of an appropriate protocol for the synthesis of a particular peptide.

Virender K. Sarin

Papers

Quantitative monitoring of solid-phase peptide synthesis by the ninhydrin reaction.

Properties of swollen polymer networks. Solvation and swelling of peptide-containing resins in solid-phase peptide synthesis

A general approach to the quantitation of synthetic efficiency in solid-phase peptide synthesis as a function of chain length

Synthesis of a cyclic analog of oxidized glutathione by an intersite reaction in a swollen polymer network