Peptide Side Chains Research Articles

Exploring novel antioxidant cyclic peptides in corn protein hydrolysate: Preparation, identification and molecular docking analysis

Antioxidant cyclic peptides were successfully identified from a corn protein hydrolysate. Hydrolysate by Alcalase + Flavourzyme showed the highest cyclic peptide purity (48.36 ± 1.81 %) and higher antioxidant activities compared with other hydrolysate. The success of peptide cyclization in hydrolysate was demonstrated by thermogravimetric analysis and thin-layer chromatography (TLC) analysis. Thermogravimetric analysis showed that the thermal stability of hydrolysate after cyclization was significantly increased, which was related to the formation of cyclic peptides. Peptides with molecular weight less than 1000 Da accounted for more than 80 % in hydrolysate after cyclization. After separation using gel silica chromatography and semi-preparative reverse phase high performance liquid chromatography (RP-HPLC), 22 novel antioxidant cyclic peptides were identified by ultra performance liquid chromatography-quadrupole-time of flight mass spectrometry (UPLC-Q-TOF-MS) and orbitrap-tandem mass spectrometry (Orbitrap-MS/MS). Synthetic cyclic peptides with the same sequence were synthesized and characterized for their antioxidant activity. Molecular docking suggested that the free radical molecules could bind with the cyclic backbone and side chain of cyclic peptides through hydrogen bonding, hydrophobic interaction as well as electrostatic interaction. This study has important implications for the high-value utilization of corn protein and new cyclic peptides drugs or functional food development.

Conformational modulation and polymerization-induced folding of proteomimetic peptide brush polymers.

Peptide-brush polymers generated by graft-through living polymerization of peptide-modified monomers exhibit high proteolytic stability, therapeutic efficacy, and potential as functional tandem repeat protein mimetics. Prior work has focused on polymers generated from structurally disordered peptides that lack defined conformations. To obtain insight into how the structure of these polymers is influenced by the folding of their peptide sidechains, a set of polymers with varying degrees of polymerization was prepared from peptide monomers that adopt α-helical secondary structure for comparison to those having random coil structures. Circular dichroism and nuclear magnetic resonance spectroscopy confirm the maintenance of the secondary structure of the constituent peptide when polymerized. Small-angle X-ray scattering (SAXS) studies reveal the solution-phase conformation of PLPs in different solvent environments. In particular, X-ray scattering shows that modulation of solvent hydrophobicity, as well as hydrogen bonding patterns of the peptide sidechain, plays an important role in the degree of globularity and conformation of the overall polymer, with polymers of helical peptide brushes showing less spherical compaction in conditions where greater helicity is observed. These structural insights into peptide brush folding and polymer conformation inform the design of these proteomimetic materials with promise for controlling and predicting their artificial fold and morphology.

Hyperpolarized nuclear Overhauser enhancement of alanine methyl groups by doubly relayed proton exchange

Hyperpolarized water in dissolution dynamic nuclear polarization (dDNP) experiments has emerged as a promising method for enhancing nuclear magnetic resonance (NMR) signals, particularly in studies of proteins and peptides. Herein, we focus on the application of “proton exchange-doubly relayed” nuclear Overhauser effects (NOE) from hyperpolarized water to achieve positive signal enhancement of methyl groups in the side chain of an alanine-glycine peptide. In particular, we show a cascade hyperpolarization transfer. Initial proton exchange between solvent and amide introduces hyperpolarization into the peptide. Subsequently, intermolecular NOE relays the hyperpolarization first to Ala-Hα and then in a second step to the Ala-CH3 moiety. Both NOEs have negative signs. Hence, the twice-relayed NOE pathway leads to a positive signal enhancement of the methyl group with respect to the thermal equilibrium magnetization. This effect might indicate a way towards hyperpolarized water-based signal enhancement for methyl groups, which are often used for NMR studies of large proteins in solution.

A Method for Rigorously Selective Capture and Simultaneous Fluorescent Labeling of N-Terminal Glycine Peptides.

Although chemical methods for the selective derivatization of amino acid (AA) side chains in peptides and proteins are available, selective N-terminal labeling is challenging, especially for glycine, which has no side chain at the α-carbon position. We report here a double activation at glycine's α-methylene group that allows this AA to be differentiated from the other 19 AAs. A condensation reaction of dibenzoylmethane with glycine results in the formation of an imine, and subsequent tautomerization is followed by intramolecular cyclization, leading to the formation of a fluorescent pyrrole ring. Additionally, the approach exhibits compatibility with AAs possessing reactive side chains. Further, the method allows for selective pull-down assays of N-terminal glycine peptides from mixtures without prior knowledge of the N-terminal peptide distribution.

Three novel umami peptides from watermelon soybean paste and the revelation of the umami mechanism through molecular docking with T1R1/T1R3

Watermelon soybean paste is a condiment popular in Henan, Shandong and Anhui provinces of China for the strong umami taste. This work used ultrafiltration and gel filtration chromatography to separate three novel umami peptides from watermelon soybean paste aqueous extract with sequences of AKEKFD, LAELK and LTFVER. The three peptides were all determined to be umami peptides by sensory evaluation and electronic tongue. Through molecular docking with umami receptor T1R1/T1R3, the umami taste mechanisms of the three umami peptides were revealed. The charged side chains in the umami peptides and T1R1/T1R3 played a key role in the perception of umami, and the primary factors of the interaction between umami peptides and T1R1/T1R3 were van der Waals forces and hydrogen bonds, which mainly contributed to the umami mechanism. This study will supplement the umami peptide database and offered a theoretical framework for further investigation on umami peptide.

Investigation of the peptides with calcium chelating capacity in hydrolysate derived from spent hen meat.

Calcium peptide chelates are developed as efficient supplements for preventing calcium deficiency. Spent hen meat (SHM) contains a high percentage of proteins but is generally wasted due to the disadvantages such as hard texture. We chose the underutilized SHM to produce peptides to bind calcium by proteolysis and aimed to investigate chelation between calcium and peptides in hydrolysate for a sustainable purpose. The optimized proteolysis conditions calculated from the result of response surface methodology for two-step hydrolysis were 0.30% (wenzyme/wmeat) for papain with a hydrolysis time of 3.5h and 0.18% (wenzyme/wmeat) for flavourzyme with a hydrolysis time of 2.8h. The enzymatic hydrolysate (EH) showed a binding capacity of 63.8±1.8mg calcium/g protein. Ethanol separation for EH improved the capacity up to a higher value of 68.6±0.6mg calcium/g protein with a high association constant of 420M-1 (25°C) indicating high stability. The separated fraction with a higher amount of Glu, Asp, Lys, and Arg had higher calcium-binding capacity, which was related to the number of ─COOH and ─NH2 groups in peptide side chains according to the result from amino acid analysis and Fourier transform infrared spectroscopy. Two-step enzymatic hydrolysis and ethanol separation were an efficient combination to produce peptide mixtures derived from SHM with high calcium-binding capacity. The high percentage of hydrophilic amino acids in the separated fraction was concluded to increase calcium-binding capacity. This work provides foundations for increasing spent hen utilization and developing calcium peptide chelates based on underutilized meat.

In-Bridge Stereochemistry: A Determinant of Stapled Peptide Conformation and Activity.

Peptide side chain stapling has been proven to be an effective strategy for fine-tuning peptide properties. This innovative approach leads to the creation of stapled peptides characterized by stabilized α-helical conformations, enhanced protein-binding affinity, improved cell permeability, superior enzymatic stability, and numerous other advantages. Extensive research has explored the impact of various stapling bridges on the properties of these peptides, with limited investigation into the influence of bridge chirality, until very recently. In this concise review, we provide a brief overview of the current state of knowledge regarding the stereochemistry within the bridges of stapled peptides, offering insights into the potential applications of chiral bridges in the design and development of stapled peptides.

Pyoverdine binding aptamers and label-free electrochemical detection of pseudomonads.

Pyoverdines are iron-chelating siderophores employed by various pseudomonads to promote their growth in iron-limited environments, facilitating both beneficial and detrimental interactions with co-inhabiting microbes or hosts, including plants and animals. The fluorescent pseudomonads produce fluorescent pyoverdines comprised of a conserved central chromophore and a unique strain-specific peptidic side chain produced by non-ribosomal peptide synthetases. Pyoverdine Pf5 (PVD-Pf5) is produced by Pseudomonas protegens Pf-5, a species known for supporting plant growth and its involvement in plant pathogen control. To develop a means of exploring the dynamics of P. protegens activity in soil and in the rhizosphere, we selected DNA aptamers that specifically recognize PVD-Pf5 with high affinities. Two selected aptamers with only 16% identity in sequence were examined for structure and function. We found evidence that both aptamers form structures in their apo-forms and one aptamer has structural features suggesting the presence of a G-quadruplex. Although their tertiary structures are predicted to be different, both aptamers bind the target PVD-Pf5 with similar affinities and do not bind other siderophores, including the related pyoverdine, pseudobactin, produced by Pseudomonas sp. B10. One aptamer binds the pyoverdine peptide component and may also interact with the chromophore. This aptamer was integrated into a nanoporous aluminum oxide biosensor and demonstrated to successfully detect PVD-Pf5 and not to detect other siderophores that do not bind to the aptamer when evaluated in solution. This sensor provides a future opportunity to track the locations of P. protegens around plant roots and to monitor PVD-Pf5 production and movement through the soil.

Rapid On-Resin N-Formylation of Peptides as One-Pot Reaction.

N-formylation is a common pre- and post-translational modification of the N-terminus or the lysine side chain of peptides and proteins that plays a role in the initiation of immune responses, gene expression, or epigenetics. Despite its high biological relevance, protocols for the chemical N-formylation of synthetic peptides are scarce. The few available methods are elaborate in their execution and the yields are highly sequence-dependent. We present a rapid, easy-to-use one-pot procedure that runs at room temperature and can be used to formylate protected peptides at both the N-terminus and the lysine side chain on the resin in near-quantitative yields. Only insensitive, storage-stable standard chemicals - formic acid, acetic anhydride, pyridine and DMF - are used. Formylation works for both short and long peptides of up to 34 amino acids and over the spectrum of canonical amino acids.

Potential alteration enabled peptide elongation for direct serum detection of S100B in the early screening of phenylketonuria

DNA and aptamers have introduced new possibilities for utilizing synthetic probes in biosensing, effectively substituting antibodies. This substitution not only significantly cuts costs but also preserves analytical performance. However, in some cases, other biomacromolecules such as DNA processing enzymes remain indispensable for achieving signal amplification and high sensitivity. In this context, a novel bioassay has been developed, entirely eliminating the need for biomacromolecules. Instead, this approach employs fully synthesizable and modifiable peptides as the sensing probes. In lieu of enzymes, the strategy involves utilizing electrochemical potentials to guide peptide strand cleavage and the cross-coupling of peptide side chains at specific amino acids. This process mimics DNA-like chain elongation. The technique has already demonstrated success in detecting peripheral blood S100B levels, offering an early screening method for phenylketonuria in infants. These promising results suggest that the novel approach of utilizing electrochemical potentials to direct peptide bonding and cross-linking could find practical applications in clinical scenarios in the near future.

Photoinduced C(sp3)-H Functionalization of Glycine Derivatives: Preparation of Unnatural α-Amino Acids and Late-Stage Modification of Peptides.

ConspectusPeptides are essential components of living systems and contribute to critical biological processes, such as cell proliferation, immune defense, tumor formation, and differentiation. Therefore, peptides have attracted considerable attention as targets for the development of therapeutic products. The incorporation of unnatural amino acid residues into peptides can considerably impact peptide immunogenicity, toxicity, side effects, water solubility, action duration, and distribution and enhance the peptides' druggability. Typically, the direct modification of natural amino acids is a practical and effective approach for promptly obtaining unnatural amino acids. However, selective functionalization of multiple C(sp3)-H bonds with comparable chemical reactivities in the peptide side chains remains a formidable challenge. Furthermore, chemical modifications aimed at highly reactive (nucleophilic and aromatic) groups on peptide side chains can interfere with the biological activity of peptides.In recent years, the rapid advancement of photoinduced radical reactions has made photoredox radical-radical cross-coupling a practical approach for constructing C(sp3)-C(sp3) bonds under mild conditions. Glycine, a naturally occurring amino acid and the fundamental skeleton of all α-amino acids, provides a basis for the alkylated modification of its own α-C(sp3)-H bond under mild conditions. This Account describes our recent research endeavors for systematically investigating the photocatalytic α-C(sp3)-H alkylation of glycine derivatives via radical-radical coupling between N-aryl glycinate-derived radicals and various alkyl radicals. In 2018, we disclosed the photoinduced Cu-catalyzed decarboxylative α-C(sp3)-H alkylation of glycine derivatives. Subsequently, we developed a catalyst-free method for alkylating glycine derivatives and glycine residues in peptides via electron donor-acceptor (EDA)-complex-promoted single electron transfer. Moreover, we developed a photoinduced method for the radical alkylation of N-aryl glycinate α-C(sp3)-H bonds using unactivated alkyl chlorides (iodides) under photocatalyst-free conditions. Notably, by building on racemic alkylations of glycine derivatives and glycine-residue-containing peptides, we recently stereoselectively alkylated the N-aryl glycinate α-C(sp3)-H bond using a dual-functional Cu catalyst generated in situ for synthesizing a series of unnatural chiral α-amino and C-glycoamino acids.We have developed a series of methods for synthesizing unnatural amino acids through the α-C(sp3)-H alkylation of glycine derivatives using photoredox-promoted radical coupling as a key strategy. These methods are efficient and versatile and can be used for the late-stage modification of peptides in various contexts. Our work builds on the fundamental importance of glycine as the basic scaffold of all α-amino acids and highlights the potential of radical-based chemistry for developing chemical transformations in peptide synthesis. These findings have broad implications for chemical biology and may open doors for discovering peptide drugs and developing therapeutics.

Development of Orally Bioavailable Peptides Targeting an Intracellular Protein: From a Hit to a Clinical KRAS Inhibitor.

Cyclic peptides as a therapeutic modality are attracting a lot of attention due to their potential for oral absorption and accessibility to intracellular tough targets. Here, starting with a drug-like hit discovered using an mRNA display library, we describe a chemical optimization that led to the orally available clinical compound known as LUNA18, an 11-mer cyclic peptide inhibitor for the intracellular tough target RAS. The key findings are as follows: (i) two peptide side chains were identified that each increase RAS affinity over 10-fold; (ii) physico-chemical properties (PCP) including Clog P can be adjusted by side-chain modification to increase membrane permeability; (iii) restriction of cyclic peptide conformation works effectively to adjust PCP and improve bio-activity; (iv) cellular efficacy was observed in peptides with a permeability of around 0.4 × 10-6 cm/s or more in a Caco-2 permeability assay; and (v) while keeping the cyclic peptide's main-chain conformation, we found one example where the RAS protein structure was changed dramatically through induced-fit to our peptide side chain. This study demonstrates how the chemical optimization of bio-active peptides can be achieved without scaffold hopping, much like the processes for small molecule drug discovery that are guided by Lipinski's rule of five. Our approach provides a versatile new strategy for generating peptide drugs starting from drug-like hits.

X-ray and Electron Diffraction Observations of Steric Zipper Interactions in Metal-Induced Peptide Cross-β Nanostructures.

The steric zipper is a common hydrophobic packing structure of peptide side chains that forms between two adjacent β-sheet layers in amyloid and related fibrils. Although previous studies have revealed that peptide fragments derived from native protein sequences exhibit steric zipper structures, their de novo designs have rarely been studied. Herein, steric zipper structures were artificially constructed in the crystalline state by metal-induced folding and assembly of tetrapeptide fragments Boc-3pa-X1-3pa-X2-OMe (3pa: β-(3-pyridyl)-l-alanine; X1 and X2: hydrophobic amino acids). Crystallographic studies revealed two types of packing structures, interdigitation and hydrophobic contact, that result in a class 1 steric zipper geometry when the X1 and X2 residues contain alkyl side chains. Furthermore, a class 3 steric zipper geometry was also observed for the first time among any reported steric zippers when using tetrapeptide fragments with (X1, X2) = (Thr, Thr) and (Phe, Leu). The system could also be extended to a knob-hole-type zipper using a pentapeptide sequence.

Alanine‐Induced Alteration of Organogelation Properties of Phenylalanine‐Based Shortest Peptide Sequence

AbstractShort peptide based Low‐molecular‐weight‐organogelators (LMWGs), or supramolecular gels have recently gained large attention due to their enormous application in several biophysical and biochemical contexts. Out of the 20 naturally occurring amino acids Phenylalanine (Phe) acts as a good organogelators. Biophysical parameters like heat, pH, and solvent polarity, along with light, ultrasound, ions, can affect in alteration of supramolecular self‐aggregation at the molecular level in moderate length of peptide sequences; however, we focused here on how the conformational characteristics and supramolecular assemblages of the excellent LMWG Phe would be influenced by its substitution with similar hydrophobic amino acids (e.g Ala) in the same organic solvent even in the shortest two residue sequence. Using different microscopic and biophysical techniques, it is observed that the supreme capability of Phe residue as LMWG in the formation of supramolecular self‐aggregation in Hex‐Phe(1)‐Phe(2)‐OMe (FF) in organic solvents has been completely altered from fibrillary dendrimeric network to the crystalline phase by substitution with Ala at the C‐terminal [Hex‐Phe(1)‐Ala(2)‐OMe](FA) in a simple two residue sequence. This demonstrates unequivocally how a little change in the peptide side chain has the unique ability to form a distinct 3D supramolecular assembly and establishes the context‐dependent supramolecular morphology of the peptide‐based LMWG.

Dynamic Response of Surface-Bound Peptides to a pH Perturbation Under Controlled Electrostatic Conditions.

The dynamic conformations of a thin peptide film covalently-linked to the surface of a transparent electrode are characterized over the course of a perturbation to their local pH by a photoacid under a controlled electrostatic potential. The local environment at this functionalized electrified interface is probed by the ultrafast fluorescence intensity and transient anisotropy of chromophores sparsely attached to the peptide side chains. A partition of chromophores into two sub-populations is observed, one buried in the peptide layer and another that is solvent exposed, and their relative contributions to the observed fluorescence signal are affected by both pH and voltage stimuli. The photophysical properties of solvent-exposed chromophores reveal that while the average conformation of the peptide mat is dictated by the pH of the surrounding electrolyte, their fluctuations are largely determined by the local electrostatic conditions set by the electrode's surface potential.

Heterofunctional polymeric degrading chimeras (HYDRAC) for targeted protein degradation.

e15106 Background: Here we utilize a novel proteomimetic polymer platform technology which packages peptide side chains as globular structures with benificial emergent properties for the development of compounds capable of targeted protein degradation. We refer to this class of compounds as Heterofunctional polYmeric DegRAding Chimeras (HYDRACs) and demonstrate the selective degradation of the oncoprotein Myc as a proof-of-concept. Methods: HYDRACs were generated using ring-opening metathesis polymerization (ROMP), resulting in structures highly resistant to proteolysis. Heterofunctional constructs were designed incorporating secondary sequences in addition to Myc-targeting H1. The degron sequence (RRRG) was incorporated to engage endogenous cellular machinery for targeted protein degradation. Immunofluorescence/confocal microscopy were used to assess cellular penetration; cellular viability assays coupled with use of both cellular (isogenic pairs, Myc-dependent and independent lines) and biochemical (scrambled H1 sequence, homopolymers, monomeric peptides) controls were used to assess tumor antiproliferative effects and Myc-specific responses. Myc target engagement was assessed via immunoprecipitation assays, NMR, circular dichroism, and fluorescence polarization with protein degradation monitored by Western blot. A CRISPR knockdown library screen of all known E3 ligases and mass spec was used to identify pathways responsible for HYDRAC-induced protein degradation. Results: A library of HYDRACs with narrow polydispersity and predetermined degrees of polymerization were generated. These compounds are cell-penetrating with antiproliferative effects at micromolar IC50s. HYDRAC treatment resulted in significant decreases in Myc protein levels, which was rescued by inhibition with MG132 and MLN4924. RNAseq showed selective overexpression of Myc pathway genes. Biophysical analysis showed strong HYDRAC-Myc interactions, supported by the presence of Myc protein following pull-down of biotin-terminated HYDRACs. Identification of E3 ligases implicated in the degradation pathway using a combination of a CRISPR knock down library and mass spectrometry are ongoing. Mice bearing Myc-CaP tumors showed delayed tumor growth following treatment with Myc-degrading HYDRACs. Studies on biodistribution and pharmacokinetic profile of the compound, as well as the ability to degrade other proteins of interest using combinations of degron sequences are ongoing. Conclusions: The presented work demonstrates the feasibility of HYDRACs for targeted protein degradation of Myc, providing rationale for further studies in Myc-driven tumor models. This successful demonstration of this first-in-class compound also opens the door for the development of HYDRACs targeting other proteins of interest and incorporation of different E3 ligase recruiters for tissue or disease-specific activity.

Chelator PBT2 Forms a Ternary Cu2+ Complex with β-Amyloid That Has High Stability but Low Specificity.

The metal chelator PBT2 (5,7-dichloro-2-[(dimethylamino)methyl]-8-hydroxyquinoline) acts as a terdentate ligand capable of forming binary and ternary Cu2+ complexes. It was clinically trialed as an Alzheimer's disease (AD) therapy but failed to progress beyond phase II. The β-amyloid (Aβ) peptide associated with AD was recently concluded to form a unique Cu(Aβ) complex that is inaccessible to PBT2. Herein, it is shown that the species ascribed to this binary Cu(Aβ) complex in fact corresponds to ternary Cu(PBT2)NImAβ complexes formed by the anchoring of Cu(PBT2) on imine nitrogen (NIm) donors of His side chains. The primary site of ternary complex formation is His6, with a conditional stepwise formation constant at pH 7.4 (Kc [M-1]) of logKc = 6.4 ± 0.1, and a second site is supplied by His13 or His14 (logKc = 4.4 ± 0.1). The stability of Cu(PBT2)NImH13/14 is comparable with that of the simplest Cu(PBT2)NIm complexes involving the NIm coordination of free imidazole (logKc = 4.22 ± 0.09) and histamine (logKc = 4.00 ± 0.05). The 100-fold larger formation constant for Cu(PBT2)NImH6 indicates that outer-sphere ligand-peptide interactions strongly stabilize its structure. Despite the relatively high stability of Cu(PBT2)NImH6, PBT2 is a promiscuous chelator capable of forming a ternary Cu(PBT2)NIm complex with any ligand containing an NIm donor. These ligands include histamine, L-His, and ubiquitous His side chains of peptides and proteins in the extracellular milieu, whose combined effect should outweigh that of a single Cu(PBT2)NImH6 complex regardless of its stability. We therefore conclude that PBT2 is capable of accessing Cu(Aβ) complexes with high stability but low specificity. The results have implications for future AD therapeutic strategies and understanding the role of PBT2 in the bulk transport of transition metal ions. Given the repurposing of PBT2 as a drug for breaking antibiotic resistance, ternary Cu(PBT2)NIm and analogous Zn(PBT2)NIm complexes may be relevant to its antimicrobial properties.

P-Chloropropynyl Phenylalanine, a Versatile Non-Canonical Amino Acid for Co-Translational Peptide Macrocyclization and Side Chain Diversification.

Macrocyclization has proven to be a beneficial strategy to improve upon some of the disadvantages of peptides as therapeutics. Nevertheless, many peptide cyclization strategies are not compatible with in vitro display technologies like mRNA display. Here we describe the novel amino acid p-chloropropynyl phenylalanine (pCPF). pCPF is a substrate for a mutant phenylalanyl-tRNA synthetase and its introduction into peptides via in vitro translation leads to spontaneous peptide macrocyclization in the presence of peptides containing cysteine. Macrocyclization occurs efficiently with a wide variety of ring sizes. Moreover, pCPF can be reacted with thiols after charging onto tRNA, enabling the testing of diverse ncAAs in translation. The versatility of pCPF should facilitate downstream studies of translation and enable the creation of novel macrocyclic peptide libraries.

Fine Tuning the Properties of Stapled Peptides by Stereogenic α-Amino Acid Bridges.

Peptide stapling represents a versatile strategy to generate peptide derivatives with stable helical structures. While a wide range of skeletons have been investigated for cyclizing the side chains of peptides, the stereochemical outcomes from the linkers remain to be better understood. In this study, we incorporated α-amino acids (α-AAs) as bridges to construct side chain-stapled analogs of an interleukin-17A-binding peptide (HAP) and evaluated the impacts of the staples on the peptide's properties. While all AA-derived peptidyl staples drastically increase the enzymatic stability of HAP, our results indicate that compared to the D-amino acid bridges, the L-AA-based staples may generate more significant impacts in increasing the helicity and enhancing the interleukin-17A(IL-17A)-binding affinity of the modified peptide. Using Rosetta modelling and molecular dynamics (MD) simulations, we demonstrate that the chirality (L/D) possessed within the AAs substantially influences the conformation of stapled HAP peptides, providing either stabilizing or destabilizing effects. Based on the computational model, a modification of the stapled HAP leads to the discovery of a peptide with further enhanced helicity, enzymatic stability and IL-17A-inhibiting ability. This systematic study reveals that chiral AAs can serve as modulatory linkers for optimizing the structures and properties of stapled peptides.

Metal-Assembled Collagen Peptide Microflorettes as Magnetic Resonance Imaging Agents

Magnetic resonance imaging (MRI) is a medical imaging technique that provides detailed information on tissues and organs. However, the low sensitivity of the technique requires the use of contrast agents, usually ones that are based on the chelates of gadolinium ions. In an effort to improve MRI signal intensity, we developed two strategies whereby the ligand DOTA and Gd(III) ions are contained within Zn(II)-promoted collagen peptide (NCoH) supramolecular assemblies. The DOTA moiety was included in the assembly either via a collagen peptide sidechain (NHdota) or through metal-ligand interactions with a His-tagged DOTA conjugate (DOTA-His6). SEM verified that the morphology of the NCoH assembly was maintained in the presence of the DOTA-containing peptides (microflorettes), and EDX and ICP-MS confirmed that Gd(III) ions were incorporated within the microflorettes. The Gd(III)-loaded DOTA florettes demonstrated higher intensities for the T1-weighted MRI signal and higher longitudinal relaxivity (r1) values, as compared to the clinically used contrast agent Magnevist. Additionally, no appreciable cellular toxicity was observed with the collagen microflorettes loaded with Gd(III). Overall, two peptide-based materials were generated that have potential as MRI contrast agents.