Chemical Modification Of Peptides Research Articles

A Synthetic Multivalent Lipopeptide Derived from Pam3CSK4 with Irreversible Influenza Inhibition and Immuno-Stimulating Effects.

The activation of the host adaptive immune system is crucial for eliminating viruses. However, influenza infection often suppresses the innate immune response that precedes adaptive immunity, and the adaptive immune responses are typically delayed. Dendritic cells, serving as professional antigen-presenting cells, have a vital role in initiating the adaptive immune response. In this study, an immuno-stimulating antiviral system (ISAS) is introduced, which is composed of the immuno-stimulating adjuvant lipopeptide Pam3CSK4 that acts as a scaffold onto which it is covalently bound 3 to 4 influenza-inhibiting peptides. The multivalent display of peptides on the scaffold leads to a potent inhibition against H1N1 (EC50 =20nM). Importantly, the resulting lipopeptide, Pam3FDA, shows an irreversible inhibition mechanism. The chemical modification of peptides on the scaffold maintains Pam3CSK4's ability to stimulate dendritic cell maturation, thereby rendering Pam3FDA a unique antiviral. This is attributed to its immune activation capability, which also acts in synergy to expedite viral elimination.

Research progress on chemical modifications of tyrosine residues in peptides and proteins.

The chemical modifications (CMs) of protein is an important technique in chemical biology, protein-based therapy, and material science. In recent years, there has been rapid advances in the development of CMs of peptides and proteins, providing new approaches for peptide and protein functionalization, as well as drug discovery. In this review, we highlight the methods for chemically modifying tyrosine (Tyr) residues in different regions, offering a comprehensive exposition of the research content related to Tyr modification. This review summarizes and provides an outlook on Tyr residue modification, aiming to offer readers assistance in the site-selective modification of macromolecules and to facilitate application research in this field.

Sequence-dependent catalysis and assembly to form peptide/Au nanoenzyme for glucose and plasma GSH detecting in cancer patients

Metal ions play a pivotal role in regulating and determining the functions of proteins and peptides in nature. This study aims to investigate the regulatory role of metal ions in peptide assembly and explore the influence of sequence variations and metal ions on the structure and function of resulting peptide nanoarchitectures. Dipeptide sequences with distinct charged properties (positive and negative) and functional groups (-COOH, -NH2, and phenolic hydroxyl) were meticulously selected and co-assembled with various metal ions (Au3+, Ag+, and Pt4+). The findings highlight the crucial functional role of the phenolic hydroxyl group of tyrosine in metal ion reduction, while positively charged groups promote metal ion accumulation through electrostatic forces, facilitating co-assembly. The formation of ordered structures in Au@Fmoc-YK and Au@Fmoc-YR nanoarchitectures further validates the significant interaction among metal ions, tyrosine-OH, and positively charged NH2. Notably, these nanoarchitectures possess the unique attribute of being prepared under physiological conditions, specifically at 37 °C, without the need for organic solvents or chemical modifications of peptides. This approach offers a straightforward means of constructing diverse functional nanoarchitectures based on peptides and metal ions. Moreover, Au@Fmoc-YR exhibits good performance as a nanoenzyme for detecting glucose in complex bodily fluids and plasma GSH in tumor patients, showcasing its promising potential for medical applications.

Chemical Modification of Peptides and Proteins Using Spirooxindole Oxirane Derivatives

AbstractMethods for chemical modification of proteins and peptides at certain positions are required for the preparation of antibody‐drug conjugates, protein‐ or peptide‐biotin conjugates, and conjugates used as therapeutics or as tools in biomedical research. We have developed chemical modification methods that use spirooxindole oxirane derivatives for the synthesis of protein‐ and peptide‐conjugates. In most cases, the epoxide group of the spirooxindole oxirane derivatives reacted to form a covalent bond with certain histidine residues and/or the N‐terminal amino group of peptides and proteins. The modification reactions of various proteins resulted in the formation of proteins modified at only one or two positions.

Ca2+-Responsive Glyco-insulin.

Chemical modification of peptides and proteins, such as PEGylation and lipidation, creates conjugates with new properties. However, they are typically not dynamic or stimuli-responsive. Self-assembly controlled by a stimulus will allow adjusting properties directly. Here, we report that conjugates of oligogalacturonic acids (OGAs), isolated from plant-derived pectin, are Ca2+-responsive. We report the conjugation of OGA to human insulin (HI) to create new glyco-insulins. In addition, we coupled OGA to model peptides. We studied their self-assembly by dynamic light scattering, small-angle X-ray scattering, and circular dichroism, which showed that the self-assembly to form nanostructures depended on the length of the OGA sequence and Zn2+ and Ca2+ concentrations. Subcutaneous administration of OGA12-HI with Zn2+ showed a stable decrease in blood glucose over a longer period of time compared to HI, despite the lower receptor binding affinity.

Peptide-Tetrapyrrole Supramolecular Self-Assemblies: State of the Art.

The covalent and noncovalent association of self-assembling peptides and tetrapyrroles was explored as a way to generate systems that mimic Nature’s functional supramolecular structures. Different types of peptides spontaneously assemble with porphyrins, phthalocyanines, or corroles to give long-range ordered architectures, whose structure is determined by the features of both components. The regular morphology and ordered molecular arrangement of these systems enhance the photochemical properties of embedded chromophores, allowing applications as photo-catalysts, antennas for dye-sensitized solar cells, biosensors, and agents for light-triggered therapies. Chemical modifications of peptide and tetrapyrrole structures and control over the assembly process can steer the organization and influence the properties of the resulting system. Here we provide a review of the field, focusing on the assemblies obtained from different classes of self-assembling peptides with tetrapyrroles, their morphologies and their applications as innovative functional materials.

Synthesis and conformation of backbone N-aminated peptides.

The chemical modification of peptides is a promising approach for the design of protein-protein interaction inhibitors and peptide-based drug candidates. Among several peptidomimetic strategies, substitution of the amide backbone maintains side-chain functionality that may be important for engagement of biological targets. Backbone amide substitution has been largely limited to N-alkylation, which can promote cis amide geometry and disrupt important H-bonding interactions. In contrast, N-amination of peptides induces distinct backbone geometries and maintains H-bond donor capacity. In this chapter we discuss the conformational characteristics of designed N-amino peptides and present a detailed protocol for their synthesis on solid support. The described methods allow for backbone N-amino scanning of biologically active parent sequences.

Signature Fragment Ions of Biotinylated Peptides.

The use of biotin or biotin-containing reagents is an essential component of many protein purification and labeling technologies. Owing to its small size and high affinity to the avidin family of proteins, biotin is a versatile molecular handle that permits both enrichment and purity that is not easily achieved by other reagents. Traditionally, the use of biotinylation to enrich for proteins has not required the detection of the site of biotinylation. However, newer technologies for discovery of protein-protein interactions, such as APEX and BioID, as well as some of the click chemistry-based labeling approaches have underscored the importance of determining the exact residue that is modified by biotin. Anti-biotin antibody-based enrichment of biotinylated peptides (e.g., BioSITe) coupled to LC-MS/MS permit large-scale detection and localization of sites of biotinylation. As with any chemical modification of peptides, understanding the fragmentation patterns that result from biotin modification is essential to improving its detection by LC-MS/MS. Tandem mass spectra of biotinylated peptides has not yet been studied systematically. Here, we describe the various signature fragment ions generated with collision-induced dissociation of biotinylated peptides. We focused on biotin adducts attached to peptides generated by BioID and APEX experiments, including biotin, isotopically heavy biotin, and biotin-XX-phenol, a nonpermeable variant of biotin-phenol. We also highlight how the detection of biotinylated peptides in high-throughput studies poses certain computational challenges for accurate quantitation which need to be addressed. Our findings about signature fragment ions of biotinylated peptides should be helpful in the confirmation of biotinylation sites.

Mass spectral analysis of acetylated peptides: Implications in proteomics.

Sequence determination of peptides using mass spectrometry plays a crucial role in the bottom-up approaches for the identification of proteins. It is crucially important to minimise false detection and validate sequence of the peptides in order to correctly identify a protein. Chemical modification of peptides followed by mass spectrometry is an option for improving the spectral quality. In silico-derived tryptic peptides with different N-terminal amino acids were designed from human proteins and synthesized. The effect of acetylation on the fragmentation of peptides was studied. N-terminal acetylation of the tryptic peptides was shown to form b1-ions, improve the abundance and occurrence of b-ions. In some cases, the intensity and occurrence of some y-ions also varied. Thus, it is demonstrated that acetylation plays an important role in improving the de novo sequencing efficiency of the peptides. The acetylation method was extended to tryptic peptides generated from the proteome of an Antarctic bacterium Pseudomonas syringae Lz4W using the proteomics work flow and mass spectra of the peptides were analysed. Comparison of the MS/MS spectra of the acetylated and unacetylated peptides revealed that acetylation helped in improving the spectral quality and validated the peptide sequences. Using this method, 673 proteins of the 1070 proteins identified were validated.

Isotopic N,N-Dimethyl Leucine (iDiLeu) for Absolute Quantification of Peptides Using a Standard Curve Approach.

Quantitative proteomics studies require an absolute quantification step to accurately measure changes in protein concentration. Absolute quantification using liquid chromatography-mass spectrometry (LC-MS) traditionally combines triple quadrupole instrumentation with stable isotope-labeled standards to measure protein concentrations via their enzymatically produced peptides. Chemical modification of peptides using labels like mass differential tags for relative and absolute quantification (mTRAQ) provides another route to determine protein quantities. This chapter describes a cost-effective and high-throughput chemical labeling method that utilizes five amine-reactive, isotopic N,N-dimethyl leucine (iDiLeu) reagents. These tags enable generation of four-point calibration curves in one LC-MS run to determine protein concentrations from labeled peptides. In particular, we provide a detailed workflow for protein quantification using the iDiLeu reagent that includes important considerations like labeling conditions and isotopic interference correction.

Polymer-based Oral Peptide Nanomedicines

Oral peptide delivery has been one of the major challenges of pharmaceutical sciences as it could lead to a great improvement of classical therapies, such as insulin, alongside making an important number of new therapies feasible. Successful oral delivery needs to fulfill two key tasks: to protect the macromolecules from degradation in the GI tract and to shuttle them across the intestinal epithelium in a safe and efficient fashion. Over the last decade, there have been numerous approaches based on the chemical modification of peptides and on the use of permeation enhancers, enzyme inhibitors and drug-delivery systems. Among the approaches developed to overcome these restrictions, the design of nanocarriers seems to be a particularly promising approach. This article is an overview on the state of the art of oral-peptide formulation strategies, with special attention to insulin delivery and the use of polymeric nanocarriers as delivery systems.

Chemical Modifications of Peptides and Their Impact on Food Properties

Chemical Modifications of Peptides and Their Impact on Food Properties

Fluorine in Peptide Design and Protein Engineering

AbstractThe use of fluorine has become well established in the analysis of protein structure and function, e.g. in tools such as 19F NMR spectroscopy. The application of the unique electronic properties of this element for the structural and chemical modification of peptides and proteins emerged as a promising approach. However, the influences of amino acid fluorination on side‐chain interactions in proteins are still controversially discussed. The systematic investigation of the interaction properties of fluoroalkyl groups in a native polypeptide environment broadens the scope of fluorinated amino acids to the rational design of structural motifs and protein interfaces. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)

Highly informative proteome analysis by combining improved N-terminal sulfonation for de novo peptide sequencing and online capillary reverse-phase liquid chromatography/tandem mass spectrometry.

Recently, various chemical modifications of peptides have been incorporated into mass spectrometric analyses of proteome samples, predominantly in conjunction with matrix-assisted laser desorption/ionization mass spectrometry (MALDI MS), to facilitate de novo sequencing of peptides. In this work, we investigate systematically the utility of N-terminal sulfonation of tryptic peptides by 4-sulfophenyl isothiocyanate (SPITC) for proteome analysis by capillary reverse-phase liquid chromatography/tandem mass spectrometry (cRPLC/MS/MS). The experimental conditions for the sulfonation were carefully adjusted so that SPITC reacts selectively with the N-terminal amino groups, even in the presence of the epsilon-amino groups of lysine residues. Mass spectrometric analyses of the modified peptides by cRPLC/MS/MS indicated that SPITC derivatization proceeded toward near completion under the experimental conditions employed here. The SPITC-derivatized peptides underwent facile fragmentation, predominantly resulting in y-series ions in the MS/MS spectra. Combining SPITC derivatization and cRPLC/MS/MS analyses facilitated the acquisition of sequence information for lysine-terminated tryptic peptides as well as arginine-terminated peptides without the need for additional peptide pretreatment, such as guanidination of lysine amino group. This process alleviated the biased detection of arginine-terminated peptides that is often observed in MALDI MS experiments. We will discuss the utility of the technique as a viable method for proteome analyses and present examples of its application in analyzing samples having different levels of complexity.

Large-scale Analysis of in Vivo Phosphorylated Membrane Proteins by Immobilized Metal Ion Affinity Chromatography and Mass Spectrometry

Global analyses of protein phosphorylation require specific enrichment methods because of the typically low abundance of phosphoproteins. To date, immobilized metal ion affinity chromatography (IMAC) for phosphopeptides has shown great promise for large-scale studies, but has a reputation for poor specificity. We investigated the potential of IMAC in combination with capillary liquid chromatography coupled to tandem mass spectrometry for the identification of plasma membrane phosphoproteins of Arabidopsis. Without chemical modification of peptides, over 75% pure phosphopeptides were isolated from plasma membrane digests and detected and sequenced by mass spectrometry. We present a scheme for two-dimensional peptide separation using strong anion exchange chromatography prior to IMAC that both decreases the complexity of IMAC-purified phosphopeptides and yields a far greater coverage of monophosphorylated peptides. Among the identified sequences, six originated from different isoforms of the plasma membrane H(+)-ATPase and defined two previously unknown phosphorylation sites at the regulatory C terminus. The potential for large-scale identification of phosphorylation sites on plasma membrane proteins will have wide-ranging implications for research in signal transduction, cell-cell communication, and membrane transport processes.

FindPept, a tool to identify unmatched masses in peptide mass fingerprinting protein identification.

FindPept (http://www.expasy.org/tools/findpept.html) is a software tool designed to identify the origin of peptide masses obtained by peptide mass fingerprinting which are not matched by existing protein identification tools. It identifies masses resulting from unspecific proteolytic cleavage, missed cleavage, protease autolysis or keratin contaminants. It also takes into account post-translational modifications derived from the annotation of the SWISS-PROT database or supplied by the user, and chemical modifications of peptides. Based on a number of experimental examples, we show that the commonly held rules for the specificity of tryptic cleavage are an oversimplification, mainly because of effects of neighboring residues, experimental conditions, and contaminants present in the enzyme sample.

Novel Peptide Dissociation: Gas-Phase Intramolecular Rearrangement of Internal Amino Acid Residues

Unique intramolecular rearrangement product ions have been observed in the product ion spectra of a number of peptides. Multiple stages of mass analysis (MSn), molecular modeling, and chemical modifications of peptides have been used to provide insight into the mechanism of this rearrangement reaction. The rearrangement process begins with a four-residue immonium ion that transfers a proton from the immonium nitrogen to the primary amine on the N-terminus. The proton transfer leads to the rearrangement of the peptide, exposing an internal amino acid on the terminus of the new ion. The internal amino acid that becomes the terminus of the new ion is then readily lost. The reaction seems to benefit from an extended experimental time frame available for reaction. The reaction is most prominent in quadrupole ion trap and Fourier-transform ion cyclotron resonance experiments, is observed under some conditions in a triple quadrupole, but is not seen in a sector instrument. Without previous knowledge of this process, the peptide sequence as determined by MS/MS could be misidentified.

消化管吸収の改善を目的としたペプチド性医薬品の脂肪酸修飾

It is well known that the oral bioavailability of peptide and protein drugs is generally poor because they are extensively degraded by proteases in the gastrointestinal tract and impermeable through the intestinal mucosa. Therefore, various approaches have been examined to overcome the delivery problems of these peptides and to improve their absorption via the gastrointestinal tract. Of these approaches, a potentially useful approach to solve these delivery problems may be chemical modification of peptides and proteins to produce prodrugs and analogues. Thus, it is plausible that this chemical approaches may protect peptides against degradation by peptidases and other enzymes present at the mucosal barrier and renders the peptides and proteins more lipophilic, resulting in increased bioavailability. From these standpoints, we synthesized lipophilic derivatives of peptides and proteins such as thyrotropin-releasing hormone (TRH), tetragastrin (TG), calcitonin and insulin by chemical modification with fatty acids. The pharmacological activities of these derivatives were relatively high as compared with the native peptides. A significant increase in the intestinal absorption of these derivatives of peptides was observed in comparison with native peptides. Overall, the effects of acylation on the intestinal absorption of these peptides were more predominant in the large intestine than those in the small intestine. In addition, these derivatives were more stable than the parent peptides in homogenates of the various intestinal mucosae. We also examined the intestinal transport characteristics of TG and its acyl derivatives using Caco-2 cell monolayer system in order to assess the contribution of enzymatic and transport barriers on their intestinal absorption. The degradation clearance of TG on the apical membrane was decreased by chemical modification with fatty acids. In addition, the permeability clearance of TG was improved by the acylation. On the other hand, CLp value of carboxyfluorescein, a paracellular transport marker, was increased by the coadministration with acyl-TGs, suggesting that these derivatives have absorption enhancing actions and may enhance themselves across the Caco-2 cell monolayers. In summary, this chemical modification approaches may be useful to improve the intestinal absorption of peptides and proteins.

Matrix‐Assisted Laser Desorption/Ionization Time‐of‐Flight Mass Analysis of Peptides

Matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) is one of the most useful techniques for determining the mass of biomolecules, with exceptional capabilities for mass analysis of peptides. Relative to other ionization techniques, it provides high sensitivity and excellent tolerance of salt and other common buffer components. Routine detection limits for peptides are in the subpicomole range. The ions commonly observed are the protonated molecules (M+H(+)), which makes data analysis relatively easy. This overview discusses instrument configuration and calibration, sample preparation, along with specific approaches for analyzing peptide mixtures, synthetic peptides, and chemical modifications of peptides.

Chemical modification of peptides containing .gamma.-carboxyglutamic acid

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTChemical modification of peptides containing .gamma.-carboxyglutamic acidNorman T. Boggs III, H. David Bruton, Daniel H. Craig, Joseph A. Helpern, Henry C. Marsh, Mark D. Pegram, David J. Vandenbergh, Karl A. Koehler, and Richard G. HiskeyCite this: J. Org. Chem. 1982, 47, 10, 1812–1816Publication Date (Print):May 1, 1982Publication History Published online1 May 2002Published inissue 1 May 1982https://doi.org/10.1021/jo00349a003RIGHTS & PERMISSIONSArticle Views175Altmetric-Citations11LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (717 KB) Get e-Alerts Get e-Alerts