Facile Synthesis of Peptide-Conjugated Gold Nanoclusters with Different Lengths

The synthesis of ultra-small gold nanoclusters (Au NCs) with sizes down to 2 nm has received increasing interest due to their unique optical and electronic properties. Like many peptide-coated gold nanospheres synthesized before, modified gold nanoclusters with peptide conjugation are potentially significant in biomedical and catalytic fields. Here, we explore whether such small-sized gold nanoclusters can be conjugated with peptides also and characterize them using atomic force microscopy. Using a long and flexible elastin-like polypeptide (ELP)20 as the conjugated peptide, (ELP)20-Au NCs was successfully synthesized via a one-pot synthesis method. The unique optical and electronic properties of gold nanoclusters are still preserved, while a much larger size was obtained as expected due to the peptide conjugation. In addition, a short and rigid peptide (EAAAK)3 was conjugated to the gold nanoclusters. Their Yong’s modulus was characterized using atomic force microscopy (AFM). Moreover, the coated peptide on the nanoclusters was pulled using AFM-based single molecule-force spectroscopy (SMFS), showing expected properties as one of the first force spectroscopy experiments on peptide-coated nanoclusters. Our results pave the way for further modification of nanoclusters based on the conjugated peptides and show a new method to characterize these materials using AFM-SMFS.

Traceless enzymatic protein synthesis without ligation sites constraint

Protein synthesis and semisynthesis offer immense promise for life science and have impacted pharmaceutical innovation. Nevertheless, the absence of a generally applicable method for traceless peptide conjugation with a flexible choice of junction sites remains a bottleneck for accessing many important synthetic targets. Here we introduce the protein activation and ligation with multiple enzymes (PALME) platform designed for the sequence-unconstrained synthesis and modification of biomacromolecules. The upstream activating modules accept and process easily accessible synthetic peptides and recombinant proteins, avoiding the challenges associated with the preparation and manipulation of activated peptide substrates. Cooperatively, the downstream coupling module provides comprehensive solutions for sequential peptide condensation, cyclization, and protein N/C-terminal or internal functionalization. This methodology's practical utility was demonstrated by synthesizing a series of bioactive targets ranging from pharmaceutical ingredients to synthetically challenging proteins. Together, the modular PALME platform exhibits unprecedented broad accessibility for the traceless protein synthesis and functionalization and holds enormous potential to extend the scope of protein chemistry and synthetic biology.

A Facile Procedure for One-Pot Stable Conjugation of Two Proglucagon Cysteine-Containing Peptide Analogs

Optimization of peptides for therapeutic purposes often includes chemical conjugation or modification with substituents that serve to broaden pharmacology or improve pharmacokinetics. We report a convenient and rapid procedure for one-pot, site-specific conjugation of two cysteine-containing peptides that utilizes a bivalent linker comprising maleimide and iodoacetyl functional groups. Following maleimide-mediated peptide conjugation the linker was converted from an unstable thiosuccinimide to a stable thioether bond suitable for biological study by mild aqueous hydrolysis. The procedure is exemplified by peptide-peptide, peptide-small molecule, and peptide-fatty acid conjugations. The method provides a facile approach to search for enhanced biological outcomes through additive and sustained peptide pharmacology unencumbered by the prospect of chemical rearrangement in the course of biological study.

Direct and Indirect Biomimetic Peptide Modification of Alginate: Efficiency, Side Reactions, and Cell Response

In the fast-developing field of tissue engineering there is a constant demand for new materials as scaffolds for cell seeding, which can better mimic a natural extracellular matrix as well as control cell behavior. Among other materials, polysaccharides are widely used for this purpose. One of the main candidates for scaffold fabrication is alginate. However, it lacks sites for cell adhesion. That is why one of the steps toward the development of suitable scaffolds for cells is the introduction of the biofunctionality to the alginate structure. In this work we focused on bone-sialoprotein derived peptide (TYRAY) conjugation to the molecule of alginate. Here the comparison study on four different approaches of peptide conjugation was performed including traditional and novel modification methods, based on 1-Ethyl-3-(3-dimethylaminopropyl)carbodiimide/N-hydroxy succinimide (EDC/NHS), 4-(4,6-dimethoxy-1,3,5-triazine-2-yl)-4-methylmorpholinium chloride (DMTMM), thiol-Michael addition and Cu-catalyzed azide–alkyne cycloaddition reactions. It was shown that the combination of the alginate amidation with the use of and subsequent Cu-catalyzed azide–alkyne cycloaddition led to efficient peptide conjugation, which was proven with both NMR and XPS methods. Moreover, the cell culture experiment proved the positive effect of peptide presence on the adhesion of human embryonic stem cells.

Traceless enzymatic protein synthesis without ligation sites constraint

Protein synthesis and semisynthesis offer immense promise for life science and have impacted pharmaceutical innovation. Nevertheless, the absence of a generally applicable method for traceless peptide conjugation with flexible choices of junction sites remains a bottleneck to accessing many important synthetic targets. Here we introduce the protein activation and ligation with multiple enzymes (PALME) platform designed for the sequence-unconstrained synthesis and modification of biomacromolecules. The upstream activating modules accept and process easily accessible synthetic peptides and recombinant proteins, avoiding the challenges associated with the preparation and manipulation of activated peptide substrates. Cooperatively, the downstream coupling module provides comprehensive solutions for sequential peptide condensation, cyclization, and protein N/C-terminal or internal functionalization. This methodology’s practical utility was showcased by synthesizing a series of bioactive targets, ranging from pharmaceutical ingredient to synthetically challenging protein. Together, the modular PALME platform exhibits unprecedented broad accessibility for the traceless protein synthesis and functionalization and holds enormous potential to extent the scope of protein chemistry and synthetic biology.

Poly(2-Ethyl-2-Oxazoline-co-Ethyleneimine)-block-Poly(ɛ-Caprolactone) Based Micelles: Synthesis, Characterization, Peptide Conjugation and Cytotoxic Activitiy

Here we present self-assembled polymeric micelles as potential delivery systems for therapeutic agents with highly tunable properties. The major goal of this study is to design breast and prostate cancer...

Effect of heparin and peptide conjugation on structure and functional properties of alginate in solutions and hydrogels

The mode and order of conjugating the heparin and the peptide to the alginate backbone greatly affect the modified alginate hydrogels’ structure–properties–function relations.

RNA-Peptide Conjugation through an Efficient Covalent Bond Formation

Many methods for modification of an oligonucleotide with a peptide have been developed to apply for the therapeutic and diagnostic applications or for the assembly of nanostructure. We have developed a method for the construction of receptor-based fluorescent sensors and catalysts using the ribonucleopeptide (RNP) as a scaffold. Formation of a covalent linkage between the RNA and the peptide subunit of RNP improved its stability, thereby expanding the application of functional RNPs. A representative method was applied for the formation of Schiff base or dihydroxy-morpholino linkage between a dialdehyde group at the 3′-end of sugar-oxidized RNA and a hydrazide group introduced at the C-terminal of a peptide subunit through a flexible peptide linker. In this report, we investigated effects of the solution pH and contribution of the RNA and peptide subunits to the conjugation reaction by using RNA and peptide mutants. The reaction yield reached 90% at a wide range of solution pH with reaction within 3 h. The efficient reaction was mainly supported by the electrostatic interaction between the RNA subunit and the cationic peptide subunit of the RNP scaffold. Formation of the RNP complex was verified to efficiently promote the reaction for construction of the RNA-peptide conjugate.