Peptide-based Systems Research Articles

Selective DNA delivery to tumor cells using an oligoarginine-LTVSPWY peptide.

DNA therapy for cancer requires efficient, selective and safe DNA delivery systems. Compared with other non-viral methods such as lipid or polymer-based DNA delivery vectors, peptide-based DNA delivery systems are biocompatible and biodegradable, which leads to lower immunogenicity and lower toxicity. Moreover, peptide vectors are easier to produce and their compositions easier to control because solid-phase peptide synthesis has been extensively developed. However, peptide-based systems for DNA delivery toward special tumor cells or tissues are still lacking. In this study, we constructed a non-viral 9rR-LTVSPWY peptide-based DNA delivery system and showed that it is able to efficiently and selectively transfect DNA into targeted tumor cells. This work presents a novel strategy for tumor cell-specific DNA delivery and a reference for designing more efficient DNA delivery systems targeted towards various types of cancer.

Specificity and Regenerability of Short Peptide Ligands Supported on Polymer Layers for Immunoglobulin G Binding and Detection

We demonstrate the specificity, regenerability, and excellent storage stability of short peptide-based systems for detection of immunoglobulin G (IgG). The bioactive component consisted of acetylated-HWRGWVA (Ac-HWRGWVA), a peptide with high IgG binding affinity, which was immobilized onto copolymer matrixes of poly(2-aminoethyl methacrylate hydrochloride-co-2-hydroxyethyl methacrylate) (poly(AMA-co-HEMA)). Surface plasmon resonance (SPR) and quartz crystal microgravimetry (QCM) were utilized with other complementary techniques to systematically investigate interfacial activities, mainly IgG binding performance as a function of the graft density and degree of polymerization of the poly(AMA-co-HEMA) support layer. Results from sodium dodecyl sulfate polyacrylamide gel electrophoresis and fluorescence microscopy indicate that the bioactive system is highly specific to IgG and resistant to nonspecific interactions when tested in mixed protein solutions.

The role of ECM proteins and protein fragments in guiding cell behavior in regenerative medicine

The promise of biomaterials design for regenerative medicine tissue engineering is predicated on the fundamental ability to direct or guide specific and highly coordinated cellular behaviors that culminate in the creation of physiologically functional tissues and organs. To date, our efforts have focused primarily on the grafting and presentation of short synthetic peptides with just cause. Short peptides are capable of high levels of control, can be manufactured relatively easily in a highly reproducible manner under GMP guidelines and are readily modified to enable their integration with numerous current and emerging chemistries for biomaterials grafting. However, while extracellular matrix (ECM)-derived peptides have demonstrated their initial purpose of promoting cell adhesion, their general lack of specificity and significantly decreased receptor binding affinities have proven detrimental in attempts to regulate highly specific and integrated processes necessary for tissue regeneration. Unlike adhesion peptides, the natural ECM displays a complex interplay with cells by supporting environmentally sensitive and cell dependent integrin specificity and binding affinity. Furthermore, the adhesion ligands on ECM proteins display a finely tuned and evolutionarily directed spatial periodicity, of which is dynamically controlled through both mechanical and chemical modifications. These and other emerging concepts from matrix biology require our attention if biomaterials design is to fulfill its promise. Here, we are charged with debating the statement ‘The use of short synthetic adhesion peptides, like RGD, is the best approach in the design of biomaterials that guide cell behavior for regenerative medicine tissue engineering’. In this Leading Opinion Paper I will focus on aspects of natural ECM proteins and protein fragments that have proven difficult, if not impossible to date, to recapitulate in peptide-based systems. While this represents an argument against the use of peptides per se, it might also be viewed as outlining the challenges and opportunities for the biomaterials field.

Design and Development of Peptides and Peptide Mimetics as Antagonists for Therapeutic Intervention

The concept of peptides as therapeutic agents has been historically disregarded by the pharmaceutical industry on account of their susceptibility to degradation, their size and consequent limitations in methods of delivery. Recently, however, there has been a surge of interest in peptides and their mimetics as potential antagonists for therapeutic intervention. This is in part due to the increased half-life and oral availability that has been achieved for a number of peptide-based systems, the introduction and acceptance of alternative delivery methods, and the prevalence of proteomics to identify countless protein-protein interaction targets. The use of peptides and molecules that mimic their function therefore has great potential to effectively target a range of proteins that are pathogenically implicated in numerous diseases.

Peptide vaccine candidates against classical swine fever virus: T cell and neutralizing antibody responses of dendrimers displaying E2 and NS2–3 epitopes

Three peptide-based systems integrating B and T antigenic sites of CSFV and displaying the B epitopes in fourfold presentation have been designed and produced, and shown to bring about significant enhancements in immunogenicity over the peptides in monomeric form. Of the different strategies tested for producing the dendrimeric constructs, stepwise SPPS using 3,6-dioxaoctanoic acid as flexible, PEG-like spacer units at the branching points is clearly advantageous, in particular over ligation in solution. The constructs have been used for immunization of domestic pigs, in order to evaluate the protective response induced by each peptide constructs, and to characterize the B- and T-cell response against CSFV in the natural host.

Protein Disulfide Isomerases fromC. elegansare Equally Efficient at Thiol-Disulfide Exchange in Simple Peptide-Based Systems But Show Differences in Reactivity Towards Protein Substrates

Although the formation of disulfide bonds is an essential process in every living organism, only little is known about the mechanisms in multicellular eukaryotic systems. The reason for this uncertainty is that in addition to the well-known key enzyme protein disulfide isomerase (PDI), several PDI-like proteins are present in the ER of metazoans. In total, there are now 18 PDI-family members in the human endoplasmic reticulum, with different domain architectures and active site chemistries. To understand why multicellular organisms express multiple proteins with similarity to the archetypal mammalian PDI, the properties of three PDIs from the nematode C. elegans were investigated. Here the authors demonstrate that PDI-1, PDI-2, and PDI-3 show comparable kinetic properties in catalyzing thiol:disulfide exchange reactions in two simple peptide-based assays. However, the three enzymes exhibited clear differences in their reactivity towards protein substrates. The authors therefore propose that the three PDIs can catalyze similar thiol-disulfide exchange reactions in a substrate, but due to differences in substrate binding, they can direct a folding polypeptide chain onto different folding pathways and hence fulfil distinct and different functions in the organism.

Introduction by guest editors

We are delighted to participate in this special issue of Biopolymers—Peptide Science, dedicated to peptides as “templates.” The scientific community has marveled at the complexity of protein structure and function throughout the modern scientific era. We continue to study the protein folding problem from an inspiring range of perspectives, spanning the natural and physical sciences. At the same time, we are drawn to the extraction of emerging principles from the structural world into the design of functional systems. Of course, the choice of function seems a matter of taste—can we design materials that will function as catalysts? Can these same principles spawn the development of materials that will exhibit new biological, electronic, or mechanical properties? This special issue attempts to bring together some of the work targeted toward one of these objectives, the development of catalysts for organic reactions. The field benefits from a natural affinity with enzymatic catalysts because the fundamental building blocks may bear some overlap. The diversity of function imprinted in the twenty coded amino acids enables a staggering array of chemical processes in both nature and the laboratory. At the same time, noncoded amino acids may be employed to expand the range of reactions that may be addressed with peptide-based systems. And of course, many of the physical organic principles that appear in the application of peptide-based catalysts may stimulate new directions in the development of nonpeptide-based catalysts. In the end, we anticipate a continuing synergy among many fields as scientists inch toward a deeper understanding of the protein folding problem, the conundrum of the correlation between primary structure and polymer function, and ultimately the application of new principles to the design of powerful new systems from first principles. The organization of this special issue attempts to provide an introduction to this exciting field. Although it by no means provides a comprehensive coverage of the subject matter, some representative topics are covered. For Part I: Peptides as Templates, we are grateful to Lila Gierasch and Dieter Seebach who, along with a contribution from the Padova group, have submitted manuscripts that offer perspectives on peptide three-dimensional structural themes. For Part II: Peptide-Based Catalysts, the topics shift to the application of peptides as catalysts. The array of chemistry presented is wide, indeed. Scott Gilbertson and coworkers have contributed a valuable manuscript on the use of peptides containing unnatural amino acids as ligands. The laboratories of Stanley Roberts and David Kelly, along with those of Albrecht Berkessel and the Padova group, have provided a state-of-the-art analysis of peptide-catalyzed epoxidations in the tradition of the Juliá-Colonna reaction. Paolo Scrimin and the Padova group have described high-precision studies of peptide-catalyzed kinetic resolutions through acyl transfer and also a novel set of oxidation reactions. Helma Wennemers and Jean-Louis Reymond have discovered useful systems for aldol and hydrolysis reactions, respectively, taking advantage of the power of combinatorial assay development. A contribution from the Boston College laboratory presents a range of catalytic reactions stemming from a variety of secondary structural templates. In the end, we are hopeful that this issue reflects the richness of an area that is ripe for future discoveries, with relevance to both the disciplines of chemistry and biology. We also take this opportunity to thank our colleagues who were able to participate in this editorial adventure.