RSSEvaluation of COMU as a coupling reagent for in situ neutralization Boc solid phase peptide synthesis.
Source
Institute for Molecular Bioscience, The University of Queensland, St Lucia, 4072, Australia; Center for Insoluble Protein Structures (inSPIN), Interdisciplinary Nanoscience Center, Department of Chemistry, Aarhus University, Langelandsgade 140, 8000, Aarhus, Denmark.
Abstract
Benzotriazole-based coupling reagents have dominated the last two decades of solid phase peptide synthesis. However, a growing interest in synthesizing complex peptides has stimulated the search for more efficient and low-cost coupling reagents, such as COMU which has been introduced as a nonexplosive alternative to the classic benzotriazole coupling reagents. Here, we present a comparative study of the coupling efficiency of COMU with the benzotriazole-based HBTU and HCTU for use in in situ neutralization Boc-SPPS. Difficult sequences, such as ACP(65-74), Jung-Redeman 10-mer, and HIV-1 PR(81-99), were used as model target peptides on polystyrene-based resins, as well as polyethylene glycol-based resins. Coupling yields obtained using fast in situ Boc-SPPS cycles were determined with the quantitative ninhydrin test as well as via LC-MS analysis of the crude cleavage products. Our results demonstrate that COMU coupling efficiency was less effective compared to HBTU and HCTU with HCTU ≥ HBTU > COMU, when polystyrene-based resins were employed. However, when the PEG resin was employed in combination with a safety catch amide (SCAL) linker, more comparable yields were observed for the three coupling reagents with the same ranking HCTU ≥ HBTU > COMU. Copyright © 2012 European Peptide Society and John Wiley & Sons, Ltd.
Copyright © 2012 European Peptide Society and John Wiley & Sons, Ltd.
A convenient approach to synthesizing peptide C-terminal N-alkyl amides.
Source
Department of Medicinal Chemistry, The University of Kansas, Lawrence, KS 66045.
Abstract
Peptide C-terminal N-alkyl amides have gained more attention over the past decade due to their biological properties, including improved pharmacokinetic and pharmacodynamic profiles. However, the synthesis of this type of peptide on solid phase by current available methods can be challenging. Here we report a convenient method to synthesize peptideC-terminal N-alkyl amides using the well-known Fukuyama N-alkylation reaction on a standard resin commonly used for the synthesis of peptide C-terminal primary amides, the peptide amide linker-polyethylene glycol-polystyrene (PAL-PEG-PS) resin. The alkylation and oNBS deprotection were conducted under basic conditions and were therefore compatible with this acid labile resin. The alkylation reaction was very efficient on this resin with a number of different alkyl iodides or bromides, and the synthesis of model enkephalin N-alkyl amide analogs using this method gave consistently high yields and purities, demonstrating the applicability of this methodology. The synthesis of N-alkyl amides was more difficult on a Rink amide resin, especially the coupling of the first amino acid to the N-alkyl amine, resulting in lower yields for loading the first amino acid onto the resin. This method can be widely applied in the synthesis of peptide N-alkyl amides. © 2011 Wiley Periodicals, Inc. Biopolymers (Pept Sci) 96: 715-722, 2011.
Copyright © 2011 Wiley Periodicals, Inc.
Structural basis of high-affinity nuclear localization signal interactions with importin-α
Source
School of Chemistry and Molecular Biosciences Australian Infectious Diseases Research Centre Australian Research Council Centre of Excellence for Integrative Legume Research, The University of Queensland, Brisbane, QLD 4072, Australia School of Biomedical Sciences, Charles Sturt University, Wagga Wagga, NSW 2650, Australia Institute for Molecular Bioscience, The University of Queensland, Brisbane, QLD 4072, Australia.
Abstract
Classical nuclear localization signals (cNLSs), comprising one (monopartite cNLSs) or two clusters of basic residues connected by a 10-12 residue linker (bipartite cNLSs), are recognised by the nuclear import factor importin-α. The cNLSs bind along a concave groove on importin-α, however, specificity determinants of cNLSs remain poorly understood. We present a structural and interaction analysis study of importin-α binding to both designed and naturally-occurring high-affinity cNLS-like sequences; the peptide inhibitors Bimax1 and Bimax2, and cNLS peptides of cap-binding protein 80. Our data suggest that cNLSs and cNLS-like sequences can achieve high affinity through maximising interactions at the importin-α minor site, and by taking advantage of multiple linker-region interactions. Our study defines an extended set of binding cavities on the importin-α surface, and also expands on recent observations that longer linkersequences are allowed, and that long-range electrostatic complementarity can contribute to cNLS-binding affinity. Altogether, our study explains the molecular and structural basis of the results of a number of recent studies including systematic mutagenesis and peptide library approaches, and provides an improved level of understanding on the specificity determinants of a cNLS. Our results have implications for identifying cNLSs in novel proteins.
© 2012 John Wiley & Sons A/S.
Novel poly(L-lysine) particles for gene delivery.
Source
National Key Laboratory of Biochemical Engineering, Institute of Process Engineering, Chinese Academy of Sciences, Beijing 100190, China.
Abstract
In this work, we designed replica particles based on poly(L-lysine) (PLL) polymers crosslinked via a homobifunctionallinker to support coadsorption of a plasmid DNA and a peptide hormone for concurrent transfection and induction of a cellular function. PLL replica particles (PLL(RP)) were prepared. Based on this PLL(RP) gene delivery system, we simultaneously evaluated the melanin stimulation and gene expression by fluorescence microscopy. Our data suggest that the PLL(RP) is a promising vector for gene therapy and hormone stimulation.
Copyright © 2011. Published by Elsevier B.V.
Nanomolar cellular antisense activity of peptide nucleic acid (PNA) cholic acid ("umbrella") and cholesterol conjugates delivered by cationic lipids.
Abstract
Limited cellular uptake and low bioavailability of peptide nucleic acids (PNAs) have restricted widespread use of PNAs as antisense/antigene agents for cells in culture and not least for in vivo applications. We now report the synthesis and cellular antisense activity in cultured HeLa pLuc705 cells of cholesterol and cholic acid ("umbrella") derivatives of splice correction antisense PNA oligomers. While the conjugates alone were practically inactive up to 1 μM, their activity was dramatically improved when delivered by a cationic lipid transfection agent (LipofectAMINE2000). In particular, PNAs, conjugated to cholesterol through an ester hemisuccinate linker or to cholic acid exhibited low nanomolar activity (EC50 ~ 25 nM). Excellent sequence specificity was retained as mismatch PNA conjugates did not show any significant antisense activity. Furthermore, we show that increasing the transfection volume improved transfection efficiency suggesting that accumulation (condensation) of the PNA/lipid complex on the cellular surface is part of the uptake mechanism. These results provide a novel, simple method for very efficient cellular delivery of PNA oligomers, especially using PNA-cholic acid conjugates which, in contrast to PNA-cholesterol conjugates exhibit sufficient water solubility. The results also question the generality of using cholic acid "umbrella" derivatives as a delivery modality for antisense oligomers.
Single Molecule Dynamics of Lysozyme Processing Distinguishes Linear and Cross-linked Peptidoglycan Substrates.
Abstract
The dynamic processivity of individual T4 lysozyme molecules was monitored in the presence of either linear or cross-linked peptidoglycan substrates. Single molecule monitoring was accomplished using a novel electronic technique in which lysozyme molecules were tethered to single-walled carbon nanotube field effect transistors through pyrene linkermolecules. The substrate driven, hinge bending motions of lysozyme induced dynamic elec-tronic signals in the underlying transistor, allowing long-term monitoring of the same molecule without the limita-tions of optical quenching or bleaching. For both sub-strates, lysozyme exhibits processive slow turnover rates of 20 - 50 s-1 and rapid 200 - 400 s-1 nonproductive motions. The latter, nonproductive binding events occupy 43% of the enzyme's time in the presence of the cross-linked pepti-doglycan, but only 7% with the linear substrate. Further-more, lysozyme catalyzed the hydrolysis of glycosidic bonds to the end of the linear substrate, but appears to sidestep the peptide cross-links to zigzag through the wild-type substrate.
Study on CCR5 analogs and affinity peptides.
Source
Biopharmaceutical Centre, State Key Laboratory of Biocontrol, College of Life Sciences, Sun Yat-Sen University, Guangdong 510275, China.
Abstract
The G protein-coupled receptor of human chemokine receptor 5 (CCR5) is a key target in the human immunodeficiency virus (HIV) infection process due to its major involvement in binding to the HIV type 1 (HIV-1) envelope glycoprotein gp120 and facilitating virus entry into the cells. The identification of naturally occurring CCR5 mutations (especially CCR5 delta-32) has allowed us to address the CCR5 molecule as a promising target to prevent or resist HIV infection in vivo. To obtain high-affinity peptides that can be used to block CCR5, CCR5 analogs with high conformational similarity are required. In this study, two recombinant proteins named CCR5 N-Linker-E2 and CCR5 mN-E1-E2 containing the fragments of the CCR5 N-terminal, the first extracellular loop or the second extracellular loop are cloned from a full-length human CCR5 cDNA. The recombinant human CCR5 analogs with self-cleavage activity of the intein Mxe or Ssp in the vector pTwinI were then produced with a high-yield expression and purification system in Escherichia coli. Experiments of extracellular epitope-activity identification (such as immunoprecipitation and indirective/competitive enzyme-linked immunosorbent assay) confirmed the close similarity between the epitope activity of the CCR5 analogs and that of the natural CCR5, suggesting the applicability of the recombinant CCR5 analogs as antagonists of the chemokine ligands. Subsequent screening of high-affinity peptides from the phage random-peptides library acquired nine polypeptides, which could be used as CCR5 peptide antagonists. The CCR5 analogs and affinity peptides elucidated in this paper provide us with a basis for further study of the mechanism of inhibition of HIV-1 infection.
- PMID:
- 22238429
- [PubMed - as supplied by publisher]
Conversion of TSH Heterodimer to a Single Polypeptide Chain Increases Bioactivity and Longevity.
Source
Department of Human Biology (N.A., R.B.-S., F.F.), Faculty of Natural Sciences, University of Haifa, Haifa 31095, Israel; and Department of Molecular Genetics (N.A., F.F.), Carmel Medical Center, Haifa 34362, Israel.
Abstract
TSH is a dimeric glycoprotein hormone composed of a common α-subunit noncovalently linked to a hormone-specific β-subunit. Previously, the TSH heterodimer was successfully converted to an active single-chain hormone by genetically fusing α and β genes with [TSHβ- carboxyl-terminal peptide (CTP)-α] or without (TSHβ-α) the CTP of human chorionic gonadotropin β-subunit as a linker. In the present study, TSH variants were expressed in Chinese hamster ovarian cells. The results indicated that TSHβ-α single chain has the highest binding affinity to TSH receptor and the highest in vitro bioactivity. With regard to the in vivo bioactivity, all TSH variants increased the levels of T(4) in circulation after 2 and 4 h of treatment. However, the level of T(4) after treatment with TSH-wild type was significantly decreased after 6 and 8 h, compared with the levels after treatment with the other TSH variants. TSHβ-α and TSHβ-CTP-α single chains exhibited almost the same bioactivity after 8 h of treatment. Evaluating the half-life of TSH variants, TSHβ-CTP-α single chain revealed the longest half-life in circulation, whereas TSH-wild type exhibited the shortest serum half-life. These findings indicate that TSH single-chain variants with or without CTP as a linker may display conformational structures that increase binding affinity and serum half-life, thereby, suggesting novel attitudes for engineering and constructing superagonists of TSH, which may be used for treating different conditions of defected thyroid gland activity. Other prominent potential clinical use of these variants is in a diagnostic test for metastasis and recurrence of thyroid cancer.
The architecture of functional modules in the Hsp90 co-chaperone Sti1/Hop.
Source
Department Chemie, Center for Integrated Protein Science (CIPSM), Technische Universität München, Garching, Germany.
Abstract
Sti1/Hop is a modular protein required for the transfer of client proteins from the Hsp70 to the Hsp90 chaperone system in eukaryotes. It binds Hsp70 and Hsp90 simultaneously via TPR (tetratricopeptide repeat) domains. Sti1/Hop contains three TPR domains (TPR1, TPR2A and TPR2B) and two domains of unknown structure (DP1 and DP2). We show that TPR2A is the high affinity Hsp90-binding site and TPR1 and TPR2B bind Hsp70 with moderate affinity. The DP domains exhibit highly homologous α-helical folds as determined by NMR. These, and especially DP2, are important for client activation in vivo. The core module of Sti1 for Hsp90 inhibition is the TPR2A-TPR2B segment. In the crystal structure, the two TPR domains are connected via a rigid linker orienting their peptide-binding sites in opposite directions and allowing the simultaneous binding of TPR2A to the Hsp90 C-terminal domain and of TPR2B to Hsp70. Both domains also interact with the Hsp90 middle domain. The accessory TPR1-DP1 module may serve as an Hsp70-client delivery system for the TPR2A-TPR2B-DP2 segment, which is required for client activation in vivo.
Elucidating protein inter- and intramolecular interacting domains using chemical cross-linking and matrix-assisted laser desorption ionization-time of flight/time of flight mass spectrometry.
Source
Department of Pharmacology and Experimental Neuroscience, University of Nebraska Medical Center, Omaha, NE 68198-5800, USA.
Abstract
Among many methods used to investigate protein/protein interactions, chemical cross-linking combined with mass spectrometry remains a vital experimental approach. Mapping peptides modified by cross-linker provides clues about proteins' interacting domains. One complication is that such modification may result from intra- but not intermolecular interactions. Therefore, for overall data interpretation, a combination of results from various platforms is necessary. It is postulated that the secretory isoform of gelsolin regulates several biological processes through interactions with proteins such as actin, fibronectin, vitamin D-binding protein, and unidentified receptors on the surface of eukaryotes; it also has been shown to self-assemble eventually leading to the formation of homo-multimers. As such, it is an excellent model for this study. We used four cross-linkers with arm length ranging from 7.7 to 21.7Å and MALDI-TOF/TOF mass spectrometry as the analytical platform. Results of this study show that MALDI-based mass spectrometry generates high quality data to show lysine residues modified by cross-linkers and combined with existing data based on crystallography (Protein Data Bank, PDB) can be used to discriminate between inter- and intramolecular linking.
Copyright © 2011 Elsevier Inc. All rights reserved.
Click Chemistry Facilitates Formation of Reporter Ions and Simplified Synthesis of Amine-Reactive Multiplexed Isobaric Tags for Protein Quantification.
Abstract
We report the development of novel reagents for cell-level protein quantification, referred to as Caltech Isobaric Tags (CITs), which offer several advantages in comparison with other isobaric tags (e.g., iTRAQ and TMT). Click chemistry, copper-catalyzed azide-alkyne cycloaddition (CuAAC), is applied to generate a gas-phase cleavable linker suitable for the formation of reporter ions. Upon collisional activation, the 1,2,3-triazole ring constructed by CuAAC participates in a nucleophilic displacement reaction forming a six-membered ring and releasing a stable cationic reporter ion. To investigate its utility in peptide mass spectrometry, the energetics of the observed fragmentation pathway are examined by density functional theory. When this functional group is covalently attached to a target peptide, it is found that the nucleophilic displacement occurs in competition with formation of b- and y-type backbone fragment ions regardless of the amino acid side-chains present in the parent bioconjugate, confirming that calculated reaction energetics of reporter ion formation are similar to those of backbone fragmentations. Based on these results, we apply this selective fragmentation pathway for the development of CIT reagents. For demonstration purposes, duplex CIT reagent is prepared using a single isotope-coded precursor, allyl-d5-bromide, with reporter ions appearing at m/z 164 and 169. Isotope-coded allyl azides for the construction of the reporter ion group can be prepared from halogenated alkyl groups which are also employed for the mass balance group via N-alkylation, reducing the cost and effort for synthesis of isobaric pairs. Owing to their modular designs, an unlimited number of isobaric combinations of CIT reagents are, in principle, possible. The reporter ion mass can be easily tuned to avoid overlapping with common peptide MS/MS fragments as well as the low mass cut-off problems inherent in ion trap mass spectrometers. The applicability of the CIT reagent is tested with several model systems involving protein mixtures and cellular systems.
Integrating structure and function of 'tandem-repeat' galectins.
Source
Institute of Biological Chemistry and Physicochemistry (UBA-CONICET), Department of Biological Chemistry, School of Pharmacy and Biochemistry, University of Buenos Aires.
Abstract
Galectins (GALs) are evolutionarily-conserved lectins defined by at least one carbohydrate recognition domain (CRD) with affinity for beta-galactosides and conserved sequence motifs. Although the biological roles of some members of this family, including the 'proto-type' GAL-1 and the 'chimera-type' GAL-3 have been widely studied, the functions of 'tandem-repeat' galectins are just emerging. The subgroup of 'tandem-repeat' galectins (GAL-4, -6, -8, -9, and -12) contain two distinct CRDs, connected by a linker peptide. Here we integrated and distilled the available information on 'tandem-repeat' galectins, their specific structures, potential ligands and biological activities in inflammatory and neoplastic diseases. While GAL-4 has been implicated in inflammatory bowel diseases, either as a pro-inflammatory or pro-apoptotic mediator, GAL-8 plays roles in autoimmune diseases such as rheumatoid arthritis and lupus erythematosus and modulates tumor progression. GAL-9 controls allergic inflammation and Th1/Th17-mediated autoimmunity and has prognostic value in certain tumor types. Finally, GAL-12 plays important roles in adipocyte physiology. Although this information is just emerging, further studies are needed to dissect the biological roles of 'tandem-repeat' galectins in health and disease.
- PMID:
- 22202096
- [PubMed - in process]
Peptide molecular junctions: Distance dependent electron transmission through oligoprolines.
Abstract
We have investigated the efficiency of electron transmission through thiolated oligoproline derivatives of general formula: Cys-(Pro)(n)-CSA, where CSA is a cystamine linker and n=1-4. The conductance measurements were performed using STM-based molecular junction approach. We have noted that the conductance of the oligoprolines decays exponentially with increasing length of the molecules and the decay constant was 4.3nm(-1). This indicates that electron transfer is dominated by superexchange mechanism. Based on this observation, we have concluded that the height of the barrier is affected by the specific conformation of the peptide backbone. Such conclusion is supported by the fact that the oligoprolines do not form intramolecular hydrogen bonds, which could provide alternative electron transfer pathways.
Copyright © 2011 Elsevier B.V. All rights reserved.
A simple oxazolidine linker for solid-phase synthesis of peptide aldehydes.
Source
Biotechnology and Pharmaceutical Engineering, Nanjing University of Technology, Nanjing 210008, China.
Abstract
A very simple and cheap linker has been used for solid-phase synthesis of peptide aldehydes. Protected amino acid aldehydes are immobilized on 2-Cl(trt) resin as oxazolidine formation via diethanolamine. After classical Fmoc SPPS, treatment of the resin with AcOH/DCM/H(2)O (8:1:1) affords peptide aldehydes in high yield and purity.
Copyright © 2011 Elsevier Ltd. All rights reserved.
Local injection of latency-associated peptide, a linker propeptide specific for active form of transforming growth factor-beta1, inhibits dermal sclerosis in bleomycin-induced murine scleroderma.
Source
Department of Dermatology, Fukushima Medical University, Fukushima, Japan.
Abstract
Transforming growth factor-β1 (TGF-β1) has been thought to play a key role in the pathogenesis of scleroderma; however, therapeutic approaches targeting TGF-β1 and/or related molecules have provided inconsistent results. In this study, we demonstrate the antifibrotic effects of local administration of latency-associated peptide (LAP), a linkerpropeptide that specifically converts the active form of TGF-β1 to the inactive from, in the bleomycin (BLM)-induced scleroderma mouse model. Histologically, co-injection of BLM and LAP into the dorsal skin prevented proinflammatory and later sclerotic responses, features seen in mice injected with BLM alone or together with PBS as control. In addition, the skin sites co-injected with BLM and LAP showed a marked decrease in mast cell infiltration. Isoform-specific ELISA and real-time RT-PCR revealed transient decreases in connective tissue growth factor and collagen α1(I) mRNA expression 2 weeks after the co-injection, preceded by a decrease in active TGF-β1 protein production. In contrast, the baseline expression of TGF-β1 mRNA remained unchanged. By contrast, after induction of scleroderma by BLM, the inhibitory effects of LAP did not occur, suggesting time course-dependent TGF-β1 regulation. Our data may have novel therapeutic implications regarding in vivo TGF-β1 inactivation in human scleroderma, and the post-transcriptional interrelationship between major fibrogenic cytokines in the autoimmune aspects of the disease.
© 2011 John Wiley & Sons A/S.
- PMID:
- 22188586
- [PubMed - as supplied by publisher]
Site-specific DOTA/europium-labeling of recombinant human relaxin-3 for receptor-ligand interaction studies.
Source
Institute of Protein Research, College of Life Sciences and Technology, Tongji University, Shanghai, 200092, China.
Abstract
Relaxin-3 (also known as INSL7) is a recently identified neuropeptide belonging to the insulin/relaxin superfamily. It has putative roles in the regulation of stress responses, food intake, and reproduction by activation of its cognate G-protein-coupled receptor RXFP3. It also binds and activates the relaxin family peptide receptors RXFP1 and RXFP4 in vitro. To obtain a europium-labeled relaxin-3 as tracer for studying the interaction of these receptors with various ligands, in the present work we propose a novel site-specific labeling strategy for the recombinant human relaxin-3 that has been previously prepared in our laboratory. First, the N-terminal 6×His-tag of the single-chain relaxin-3 precursor was removed by Aeromonas aminopeptidase and all of the primary amines of the resultant peptide were reversibly blocked by citroconic anhydride. Second, the A-chain N-terminus of the blocked peptide was released by endoproteinase Asp-N cleavage that removed the linker peptide between the B- and A-chains. Third, an alkyne moiety was introduced to the newly released A-chain N-terminus by reaction with the highly active primary amine-specific N-hydroxysuccinimide ester. Fourth, after removal of the reversible blockage under mild acidic condition, europium-loaded DOTA with an azide moiety was introduced to the two-chain relaxin-3 carrying the alkyne moiety through click chemistry. Using this site-specific labeling strategy, homogeneous monoeuropium-labeled human relaxin-3 could be obtained with good overall yield. In contrast, conventional random labeling resulted in a complex mixture that was poorly resolved because human relaxin-3 has four primary amine moieties that all react with the modification reagent. Both saturation and competition binding assays demonstrated that the DOTA/Eu(3+)-labeled relaxin-3 retained high binding affinity for human RXFP3, RXFP4, and RXFP1 and was therefore a suitable non-radioactive and stable tracer to study the interaction of various natural or designed ligands with these receptors. Using this site-specific labeling strategy, other functional probes, such as fluorescent dyes, biotin, or nanoparticles could also be introduced to the A-chain N-terminal of the recombinant human relaxin-3. Additionally, we improved the time-resolved fluorescence assay for the DOTA-bound europium ion which paves the way for the use of DOTA as a lanthanide chelator for protein and peptide labeling in future studies.
NMEGylation: a novel modification to enhance the bioavailability of therapeuticpeptides.
Source
Department of Chemical and Systems Biology, Stanford University School of Medicine, Stanford, CA 94305, USA.
Abstract
We have evaluated "NMEGylation"--the covalent attachment of an oligo-N-methoxyethylglycine (NMEG) chain--as a new form of peptide/protein modification to enhance the bioavailability of short peptides. OligoNMEGs are hydrophilic polyethylene glycol-like molecules made by solid-phase synthesis, typically up to 40 monomers in length. They have been studied as nonfouling surface coatings and as monodisperse mobility modifiers for free-solution conjugate capillary electrophoresis. However, polyNMEGs have not been demonstrated before this work as modifiers of therapeutic proteins. In prior published work, we identified a short peptide, "C20," as a potential extracellular inhibitor of the fusion of human respiratory syncytial virus with mammalian cells. The present study was aimed at improving the C20 peptide's stability and solubility. To this end, we synthesized and studied a series of NMEGylated C20 peptide-peptoid bioconjugates comprising different numbers of NMEGs at either the N- or C-terminus of C20. NMEGylation was found to greatly improve this peptide's solubility and serum stability; however, longer polyNMEGs (n > 3) deleteriously affectedpeptide binding to the target protein. By incorporating just one NMEG monomer, along with a glycine monomer as a flexible spacer, at C20's N-terminus (NMEG-Gly-C20), we increased both solubility and serum stability greatly, while recovering a binding affinity comparable to that of unmodified C20 peptide. Our results suggest that NMEGylation with an optimized number of NMEG monomers and a proper linker could be useful, more broadly, as a novel modification to enhance bioavailability and efficacy of therapeutic peptides.
Development of homomultimers and heteromultimers of lung cancer-specific peptoids.
Source
Advanced Imaging Research Center, UT-Southwestern Medical Center, 5323 Harry Hines Boulevard, Dallas 75390, TX, USA.
Abstract
Multimeric interactions that occur in biology provide impetus for chemists to explore new types of synthetic multivalent ligands that alter cellular functions by mechanisms inaccessible to natural substances. While many different molecules such as peptides, antibody fragments, carbohydrates and organic moieties have been used in developing multimeric ligands, it is worth exploring other important molecular types that have hardly been tested in developing multimeric compounds. Peptoids are one such class of compounds with highly facile synthesis as well as much better biologically amenable qualities. Recently, we identified two HCC4017 lung cancer cell targeting peptoids. Here we explore the possibility of synthesizing multimers of these compounds completely through a solid phase synthesis approach. We have synthesized mini-libraries of homodimers, homotrimers and most importantly, heterodimers of our lung cancer specific compounds. The idea is to develop series of compounds that only differs by the linker portion, which is readily adjustable within the library. The purpose of this is to find the optimal distance between each monomeric unit of the multimer that allows them to perfectly interact with their individual biological targets displayed on the cell surface. Future screens of these minilibraries will identify the multimers with improved binding affinities.
- PMID:
- 22180904
- [PubMed - in process]
Helical Content of a β(3) -Octapeptide in Methanol: Molecular Dynamics Simulations Explain a Seeming Discrepancy between Conclusions Derived from CD and NMR Data.
Source
Laboratory of Physical Chemistry, Swiss Federal Institute of Technology, ETH, 8093 Zürich (Switzerland).
Abstract
Connecting experimental observables with the underlying conformational ensemble is a long-standing problem in the structure determination of biomolecules. The simulations described in this article attempt to resolve a seeming discrepancy between the conformational features derived from measured NOE intensities, (3) J-coupling constants, and circular dichroism (CD) spectra for two β-peptides differing in a linker between two side-chains. Although both peptidesare very similar in terms of the r(-6) averaged distances between atom pairs involved in the observed NOEs, the molecular dynamics trajectories suggest why the CD spectra show a greater 3(14) -helical propensity for the linked, cyclic peptide than for the linear one, whereas slightly more NMR NOE peaks are observed and assigned for the latter. The nine 100 ns unrestrained simulations show better agreement with the observed experimental data than the single conformations derived from the published NMR structures by additional energy minimization with the GROMOS force field. They show why the seemingly contradictory quantities obtained by NMR and CD spectroscopy can arise from a single conformational ensemble.
Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Synthesis and reactivity of a bis-sultone cross-linker for peptide conjugation and [(18)F]-radiolabelling via unusual "double click" approach.
Source
Advanced Accelerator Applications, 20 Rue Diesel, 01630, Saint-Genis-Pouilly, France. cedric.bouteiller@adacap.com.
Abstract
A novel homobifunctional cross-linker based on a bis-sultone benzenic scaffold was synthesised. The potential utility of this bioconjugation reagent was demonstrated through the preparation of an original prosthetic group suitable for the [(18)F]-labelling of peptides. The labelling strategy is based on the nucleophilic fluorination via the ring-opening of a first sultone moiety followed by the nucleophilic ring-opening of the second remanent sultone by a reactive amine of the biopolymer. Beyond the one-step radiolabelling of the peptide, the second main advantage of this strategy is the release of free sulfonic acid moieties making the separation of the targeted [(18)F]-tagged sulfonated compound from its non-sulfonated precursor easier and thus faster. This first report of the successful use of a bis-sultone moiety as a versatile bioconjugatable group was demonstrated through a comprehensive reactivity study involving various nucleophiles, especially those commonly found in biopolymers. An illustrative example, highlighting the potential of this unusual and promising "double click" conjugation approach, was devoted to the radiolabelling of a biological relevant peptide
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