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Solid Support (solid + support)
Selected AbstractsToward Diels,Alder Reactions on a Solid Support Using Polymer Bound N -Substituted 3-Hydroxy-4,4-dimethyl-2-pyrrolidinone Acrylate DerivativesEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 11 2004Rhalid Akkari Abstract Several N -substituted 3-hydroxy-4,4-dimethyl-2-pyrrolidinone acrylate derivatives, selected to allow their attachment to a polymer, have been prepared and tested as dienophiles in the Diels,Alder reaction. The experiments, performed under TiCl4 catalysis in solution or the solid phase with isoprene and cyclopentadiene as dienes, pointed out the difficulties associated with some of these compounds that failed to give the corresponding cycloadduct. 13C NMR studies provided some evidence regarding the nature of the interactions between the acrylate compounds and TiCl4. It appears that the outcome of the reaction is dependent on the acrylate structure and that the 4-(3-hydroxy-4,4-dimethyl-2-oxopyrrolidin-1-yl)benzoic acid acrylate derivatives are highly efficient to give the cycloadduct in good yield and with high regio- or endoselectivity in both solution and solid-phase reaction conditions. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004) [source] A Novel Oxime-Derived Solid Support for the Synthesis of 3-Phosphorylated OligonucleotidesHELVETICA CHIMICA ACTA, Issue 10 2003Simon Oligonucleotides containing terminal phosphate groups serve as useful intermediates for different applications in molecular and cell biology, as well as for diagnostic purposes. The chemical synthesis of these derivatives has been an important topic of oligonucleotide research. We report here a novel polystyrene-based solid support bearing an , -hydroxy oximate linker that allows the synthesis of 3,-phosphorylated oligodeoxynucleotides as well as oligoribonucleotides in high quality. The formation of the phosphorylated oligonucleotides likely proceeds through an eliminative pathway with concurrent nitroso-ene production. [source] Microreactor Array Assembly, Designed for Diversity Oriented Synthesis Using a Multiple Core Structure Library on Solid SupportMOLECULAR INFORMATICS, Issue 11 2006Alexander Groß Abstract The application of spatially encoded principles in solid phase combinatorial synthesis requires no chemical or physical coding strategies. The resulting products are encoded by their position inside the array and their synthesis history. The advantages of microreactor arrays for solid phase synthesis as one of the embodiments in the field of microreaction technology are discussed. Here, we review the reactor design, necessary process steps, and a strategy for the diversity oriented array synthesis. In particular, the glass-made microreactor and its assembly for 1563 parallel solid phase reactions, which can be performed at temperatures up to 120,°C, are described. Bead loading and liquid handling steps were adapted to this array. The production of large libraries demands suitable synthesis protocols and building blocks. The optimization of appropriate synthesis conditions is a time-consuming process. A multiple core structure library approach for the efficient synthesis of diverse heterocyclic libraries is described. The aim of this work was to prove the feasibility of the glass-microreaction array for massive parallel library synthesis. [source] Electrically Addressable Multistate Volatile Memory with Flip-Flop and Flip-Flap-Flop Logic Circuits on a Solid Support,ANGEWANDTE CHEMIE, Issue 28 2010Graham de, Ruiter Flip-Flops: Auf der Grundlage elektrisch ansprechbarer Os2+ -basierter Mehrfachschichten wurde ein mehrwertiger Arbeitsspeicher verwirklicht. Die kontrollierbaren optischen Eigenschaften der Mehrfachschichten ermöglichen den Aufbau von Speichereinheiten, die abhängig von der elektrischen Eingabe bis zu fünf verschiedene Zustände speichern können (siehe Bild). Die Speicheroperationen können durch sequenzielle, zu Flip-Flop-und Flip-Flap-Flop-Funktionseinheiten äquivalente Logikschaltkreise dargestellt werden. [source] ChemInform Abstract: Microwave Assisted Synthesis of 1,3,4-Oxadiazolyl 1,8-Naphthyridines under Solvent-Free Conditions Using Solid Support.CHEMINFORM, Issue 7 2010K. Mogilaiah Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source] ChemInform Abstract: Microwave-Assisted Solvent-Free Synthesis of Some Bioactive Substituted Dihalo 1,4-Benzoquinones on Silica Gel Solid Support.CHEMINFORM, Issue 40 2009Manoj Kumar Batra Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source] ChemInform Abstract: Synthesis of (.+-.)-(E)-2,6-Dimethyl-6-hydroxy-2,7-octadienoic Acid (III), Its Methyl Ester (V) and (.+-.)-(E)-2,6-Dimethyl-octa-2,7-diene-1,6-diol (VI) over Solid Support Using Microwave.CHEMINFORM, Issue 28 2009Ashima Singh Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source] ChemInform Abstract: DCC,Celite Hybrid Immobilized Solid Support as a New, Highly Efficient Reagent for the Synthesis of O-Alkyl Hydrogen Alkylphosphonates under Solvent-Free Conditions.CHEMINFORM, Issue 24 2008A. K. Gupta Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source] Convenient and Efficient Reduction of 1,1,-Binaphthyls to H8 -1,1,-Binaphthyl Derivatives with Pd and Ru Catalysts on Solid Support.CHEMINFORM, Issue 34 2004Andrei Korostylev Abstract For Abstract see ChemInform Abstract in Full Text. [source] ChemInform Abstract: Fluoroapatite/Sodium Nitrate as a Solid Support for the Knoevenagel Reaction.CHEMINFORM, Issue 39 2001Said Sebti Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source] ChemInform Abstract: Dry Media Synthesis of 4H-1,4-Benzothiazines under Microwave Irradiation Using Basic Alumina as Solid Support.CHEMINFORM, Issue 35 2001Satya Paul Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source] Insoluble Perfluoroalkylated Polymers: New Solid Supports for Supported Fluorous Phase CatalysisADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 13 2010Nicolas Audic Abstract New perfluoroalkylated polystyrene resins have been prepared by the suspension polymerisation of 4-(perfluoro- n -octyl)styrene. The evaluation of these highly fluorinated insoluble materials as catalyst supports for rhodium-catalysed hydrogenation of styrene and palladium-mediated Suzuki,Miyaura carbon-carbon bond forming reactions with 4-bromoacetophenone and 4-bromoanisole revealed improvements in the recycling of the perfluoroalkylated catalysts as compared to that achieved using fluorous reverse-phase silica gel. [source] Covalent Attachment of Bacteriorhodopsin Monolayer to Bromo-terminated Solid Supports: Preparation, Characterization, and Protein StabilityCHEMISTRY - AN ASIAN JOURNAL, Issue 7 2008Yongdong Jin Dr. Abstract The interfacing of functional proteins with solid supports and the study of related protein-adsorption behavior are promising and important for potential device applications. In this study, we describe the preparation of bacteriorhodopsin (bR) monolayers on Br-terminated solid supports through covalent attachment. The bonding, by chemical reaction of the exposed free amine groups of bR with the pendant Br group of the chemically modified solid surface, was confirmed both by negative AFM results obtained when acetylated bR (instead of native bR) was used as a control and by weak bands observed at around 1610,cm,1 in the FTIR spectrum. The coverage of the resultant bR monolayer was significantly increased by changing the pH of the purple-membrane suspension from 9.2 to 6.8. Although bR, which is an exceptionally stable protein, showed a pronounced loss of its photoactivity in these bR monolayers, it retained full photoactivity after covalent binding to Br-terminated alkyls in solution. Several characterization methods, including atomic force microscopy (AFM), contact potential difference (CPD) measurements, and UV/Vis and Fourier transform infrared (FTIR) spectroscopy, verified that these bR monolayers behaved significantly different from native bR. Current,voltage (I,V) measurements (and optical absorption spectroscopy) suggest that the retinal chromophore is probably still present in the protein, whereas the UV/Vis spectrum suggests that it lacks the characteristic covalent protonated Schiff base linkage. This finding sheds light on the unique interactions of biomolecules with solid surfaces and may be significant for the design of protein-containing device structures. [source] The biotin-streptavidin interaction can be reversibly broken using water at elevated temperaturesELECTROPHORESIS, Issue 3 2005Anders Holmberg Abstract The biotin-streptavidin system is the strongest noncovalent biological interaction known, having a dissociation constant, Kd, in the order of 4×10,14 M. The strength and specificity of the interaction has led it to be one of the most widely used affinity pairs in molecular, immunological, and cellular assays. However, it has previously been impossible to re-use any streptavidin solid support, since the conditions needed to break the interaction with biotin has led to the denaturation of the streptavidin. Here, we show that a short incubation in nonionic aqueous solutions at temperatures above 70°C can efficiently break the interaction without denaturing the streptavidin tetramer. Both biotin and the streptavidin remain active after dissociation and both molecules can therefore be re-used. The efficiency of the regeneration allowed solid supports with streptavidin to be used many times, here exemplified with the multiple re-use of streptavidin beads used for sample preparation prior to automated DNA sequencing. The results suggest that streptavidin regeneration can be introduced as an improvement in existing methods and assays based on the streptavidin system as well as emerging solid phase applications in fields, such as microfluidics and nanotechnology. [source] Comparison of two glutaraldehyde immobilization techniques for solid-phase tryptic peptide mapping of human hemoglobin by capillary zone electrophoresis and mass spectrometryELECTROPHORESIS, Issue 9 2004Isabelle Migneault Abstract Stabilization of proteolytic enzymes, especially by immobilization, is of considerable interest because of their potential applications in medicine and the chemical and pharmaceutical industries. We report here a detailed comparison of two procedures for trypsin immobilization using the same homobifunctional agent, glutaraldehyde, for the purpose of peptide mapping. These methods include covalent coupling either to controlled pore glass (solid support) or via a cross-linking reaction (without any solid support). The immobilized trypsin preparations were characterized by the determination of immobilization efficiency, which ranged from 68 to > 95%, and measurement of apparent kinetic parameters toward a synthetic peptide-like substrate. Batch digestions of whole denaturated human normal adult hemoglobin (HbA) were performed to obtain peptide maps by capillary zone electrophoresis (CZE). Migration time reproducibility of the CZE maps was excellent, with a mean relative standard deviation of 1.5%. Moreover, the two immobilized enzyme preparations showed excellent reproducibility for repeated digestions. Matrix-assisted laser desorption/ionization (MALDI)-mass spectrometry was also used for peptide mass mapping of denaturated HbA digested using the two immobilized trypsin preparations. Even though the two immobilized trypsin preparations do not behave identically, similar sequence coverages of 57% and 61% (for the two HbA chains merged) were achieved for the support-based and cross-linked trypsin preparations, respectively. [source] Transcript and activity levels of different Pleurotus ostreatus peroxidases are differentially affected by Mn2+ENVIRONMENTAL MICROBIOLOGY, Issue 5 2001Roni Cohen The white-rot fungus Pleurotus ostreatus produces both manganese-dependent peroxidase (MnP) and versatile peroxidase (VP) in non-manganese-amended peptone medium (PM). We studied the effect of Mn2+ supplementation on MnPs and VPs in P. ostreatus by analysing the enzymatic and transcript abundance profiles of the peroxidases, as well as the lignin mineralization rate. The fungus was grown in PM under solid-state conditions using perlite as an inert solid support. Mn2+ amendment resulted in a 1.7-fold increase in [14C]-lignin mineralization relative to unamended medium. Anion-exchange chromatography was used to resolve the fungal peroxidase's enzymatic activity profile. Five peaks (P1,P5) of VP and one peak (P6) of MnP activity were detected in unamended medium. In Mn2+ -amended medium, a reduction in the activity of the VPs was observed. On the other hand, a sharp increase in the MnP activity level of peak P6 was detected. The P6 isoenzyme was purified and showed manganese-dependent peroxidation of phenolic substrates. Internal sequence analysis of the purified enzyme revealed 100% identity with the deduced amino acid sequence of P. ostreatus MnP3 (GenBank AB016519). The effect of Mn2+ on the relative abundance of gene transcripts of three VPs and one MnP from P. ostreatus was monitored using reverse transcription,polymerase chain reaction (RT,PCR) with oligonucleotide primer sets synthesized on the basis of non-conserved sequences of the different peroxidases. The reduction in VP gene transcript abundance and the increase in mnp3 transcript level were collinear with the changes observed in the enzyme activity profiles. These results indicate that the activity of peroxidases is regulated at the transcriptional level. We suggest that the expression of MnP and VP may be differentially regulated by the presence of Mn2+. [source] Application of Gel-Phase 195Pt NMR Spectroscopy in a Novel Solid-Phase Synthesis of a Primary Amine Dichloroplatinum(II) ComplexEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 8 2003Marc S. Robillard Abstract Gel-phase 195Pt NMR spectroscopy of dichloroplatinum peptide complexes attached to a solid support is described. The observed 195Pt chemical shifts of the support-bound platinum complexes are in good agreement with the solution-state 195Pt NMR spectra of the soluble and deprotected analogs. This non-destructive analytical method for on-resin-compound analysis was applied in the optimization of the solid-phase synthesis of the primary amine dichloroplatinum complex 6, which represents a new class of platinum complexes now available via solid-phase synthetic chemistry. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003) [source] Highly Enantioselective Synthesis of No-Carrier-Added 6-[18F]Fluoro- L -dopa by Chiral Phase-Transfer AlkylationEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 13 2004Christian Lemaire Abstract [18F]Fluoro- L -dopa, an important radiopharmaceutical for positron emission tomography (PET), has been synthesized using a phase-transfer alkylation reaction. A chiral quaternary ammonium salt derived from a Cinchona alkaloid served as phase-transfer catalyst for the enantioselective alkylation of a glycine derivative. The active methylene group of this Schiff-base substrate was deprotonated with cesium hydroxide and rapidly alkylated by the 2-[18F]fluoro-4,5-dimethoxybenzyl halide (X = Br, I). The reaction proceeded with high yield (> 90%) at 0 °C or room temperature in various solvents such as toluene or dichloromethane. Preparation of the [18F]alkylating agent on a solid support was developed. After labelling, the labeled [18F]fluoroveratraldehyde was trapped on a tC18 cartridge and then converted on the cartridge into the corresponding benzyl halide derivatives by addition of aqueous sodium borohydride and gaseous hydrobromic or -iodic acid. Hydrolysis and purification by preparative HPLC made 6-[18F]fluoro- L -dopa ready for human injection in a 25,30% decay-corrected radiochemical yield in a synthesis time of 100 min. The product was found to be chemically, radiochemically and enantiomerically pure (ee > 95%). (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004) [source] Synthesis of Peptide-PNA-Peptide Conjugates by Semi-Solid-Phase Chemical Ligation Combined with Deactivation/Capture of Excess ReactantsEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 4 2004Martijn C. de Koning Abstract An expeditious route to peptide-PNA-peptide conjugates following a two-step native chemical ligation (NCL) strategy is described. A cys-PNA-thioester is immobilized on PEGA-aldehyde resin by thiazolidine formation, followed by capping of excess resin aldehydes. The first NCL reaction is then performed with the immobilized PNA-thioester, to give, after release from the solid support, the cys-PNA-peptide intermediate with relatively high purity. The latter is then converted into the target compound by the second NCL reaction with a thioester peptide, the excess of which is captured using a cysteine-PEGA resin. The resulting peptide-PNA-peptide can then be readily isolated by a simple purification step. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004) [source] Solvent-Free Microwave-Assisted Efficient Synthesis of 4,4-Disubstituted 2-OxazolinesEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 22 2003Fernando García-Tellado Abstract 4,4-Disubstituted 2-oxazolines have been synthesized by a microwave-promoted solvent-free direct condensation of carboxylic acids and disubstituted ,-amino alcohols in good to excellent yields. Zinc oxide is a very good solid support in cases where a Lewis acid is required. The method described herein is a very good, safe, clean, economical, and environmentally friendly alternative to the classical procedures. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003) [source] From Molecular Machines to Microscale Motility of Objects: Application as "Smart Materials", Sensors, and NanodevicesADVANCED FUNCTIONAL MATERIALS, Issue 5 2007I. Willner Abstract Machinelike operations are common functions in biological systems, and substantial recent research efforts are directed to mimic such processes at the molecular or nanoscale dimensions. The present Feature Article presents three complementary approaches to design machinelike operations: by the signal-triggered mechanical shuttling of molecular components; by the signal-triggering of chemical processes on surfaces, resulting in mechanical motion of micro/nanoscale objects; and by the fuel-triggered motility of biomolecule,metal nanowire hybrid systems. The shuttling of molecular components on molecular wires assembled on surfaces in semirotaxane configurations using electrical or optical triggering signals is described. The control of the hydrophilic/hydrophobic surface properties through molecular shuttling or by molecular bending/stretching processes is presented. Stress generated on microelements, such as cantilevers, results in the mechanical deflection of the cantilever. The deposition of a redox-active polyaniline film on a cantilever allows the reversible electrochemically induced deflection and retraction of the cantilever by the electrochemical oxidation or reduction of the polymer film, respectively. A micro-robot consisting of the polypyrrole (PPy) polymer deposited on a multi-addressable configuration of electrodes is described. Au magnetic core/shell nanoparticles are incorporated into a polyaniline film, and the conductivity of the composite polymer is controlled by an external magnet. Finally, the synthesis of a hybrid nanostructure consisting of two actin filaments tethered to the two ends of a Au nanowire is described. The adenosine triphosphate (ATP)-fueled motility of the hybrid nanostructure on a myosin monolayer associated with a solid support is demonstrated. [source] A Novel Oxime-Derived Solid Support for the Synthesis of 3-Phosphorylated OligonucleotidesHELVETICA CHIMICA ACTA, Issue 10 2003Simon Oligonucleotides containing terminal phosphate groups serve as useful intermediates for different applications in molecular and cell biology, as well as for diagnostic purposes. The chemical synthesis of these derivatives has been an important topic of oligonucleotide research. We report here a novel polystyrene-based solid support bearing an , -hydroxy oximate linker that allows the synthesis of 3,-phosphorylated oligodeoxynucleotides as well as oligoribonucleotides in high quality. The formation of the phosphorylated oligonucleotides likely proceeds through an eliminative pathway with concurrent nitroso-ene production. [source] A new convenient way to synthesize 1-hydroxyphosphonates from heterocyclic aldehydes and ketones under microwave irradiationHETEROATOM CHEMISTRY, Issue 4 2007Dexin Feng A simple and efficient method has been developed for the synthesis of 1-hydroxyphosphonates from heterocyclic aldehydes and ketones under solvent-free conditions using microwave irradiation. Various phosphites have been used to find the influence of steric exclusion on the reaction. The products are readily obtained in satisfactory yields, on the solid support of MgO. The reactions are also induced by oil-heat, and we find that the condition of microwave is better than oil-heat with respect to reaction times and product yields. © 2007 Wiley Periodicals, Inc. Heteroatom Chem 18:347,353, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.20304 [source] Allylation of Aldehydes Promoted by the Cerium(III) Chloride Heptahydrate/Sodium Iodide System: the Dependence of Regio- and Stereocontrol on the Reaction ConditionsADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 11-13 2005G. Bartoli Abstract The cerium(III) chloride heptahydrate/sodium iodide complex (CeCl3,,,7,H2O/NaI) acts as a useful promoter in the carbon-carbon bond forming reaction by addition of allyltributylstannanes to aldehydes. The reaction of 2-butenyltributylstannane shows that the regio- and the stereochemical outcomes depend on the reaction conditions. When the promoter is adsorbed on a solid support (aluminum oxide), a highly prevalent formation of the ,-adduct is observed in solvent-free conditions. Conversely, when the reaction is carried out in acetonitrile as the solvent, the ,-adduct largely prevails. In the last case, a complete stereocontrol is observed, the less stable (Z)-isomer being obtained in high geometrical purity. [source] Methods for stabilizing and activating enzymes in ionic liquids,a reviewJOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 7 2010Hua Zhao Abstract Ionic liquids (ILs) have evolved as a new type of non-aqueous solvents for biocatalysis, mainly due to their unique and tunable physical properties. A number of recent review papers have described a variety of enzymatic reactions conducted in IL solutions; on the other hand, it is important to systematically analyze methods that have been developed for stabilizing and activating enzymes in ILs. This review discusses the biocatalysis in ILs from two unique aspects (1) factors that impact the enzyme's activity and stability, (2) methods that have been adopted or developed to activate and/or stabilize enzymes in ionic media. Factors that may influence the catalytic performance of enzymes include IL polarity, hydrogen-bond basicity/anion nucleophilicity, IL network, ion kosmotropicity, viscosity, hydrophobicity, the enzyme dissolution, and surfactant effect. To improve the enzyme's activity and stability in ILs, major methods being explored include the enzyme immobilization (on solid support, sol,gel, or CLEA), physical or covalent attachment to PEG, rinsing with n -propanol methods (PREP and EPRP), water-in-IL microemulsions, IL coating, and the design of enzyme-compatible ionic solvents. It is exciting to notice that new ILs are being synthesized to be more compatible with enzymes. To utilize the full potential of ILs, it is necessary to further improve these methods for better enzyme compatibility. This is what has been accomplished in the field of biocatalysis in conventional organic solvents. Copyright © 2010 Society of Chemical Industry [source] Synthesis of tritium labelled delta sleep-inducing peptideJOURNAL OF LABELLED COMPOUNDS AND RADIOPHARMACEUTICALS, Issue 7 2001Matthieu Giraud Abstract The ,,, -dehydro precursor of the delta sleep-inducing peptide (DSIP) for tritiation was prepared prior to tritiation using a 3+6 fragment coupling strategy on a solid support. The first fragment, ,,, -dehydrotripeptide, was prepared in solution in five steps in 79% overall yield while the second fragment was obtained by a step by step peptide synthesis on a Wang resin using an Fmoc strategy. The ,,, -dehydrotripeptide was coupled to the fragment linked to the resin, followed by a deprotection/cleavage step to yield the ,,, -dehydro-DSIP, 7. Catalytic reduction of unsaturated DSIP using tritium gas and palladium oxide as catalyst gave [3H]DSIP having a specific activity of 1.184 TBq/mmol(32 Ci/mmol). Copyright © 2001 John Wiley & Sons, Ltd. [source] Oligohis-tags: mechanisms of binding to Ni2+ -NTA surfacesJOURNAL OF MOLECULAR RECOGNITION, Issue 4 2009Steven Knecht Abstract Since immobilized metal ion affinity chromatography (IMAC) was first reported, several modifications have been developed. Among them, Ni2+ immobilized by chelation with nitrilotriacetic acid (NTA) bound to a solid support has become the most common method for the purification of proteins carrying either a C - or N -terminal histidine (His) tag. Despite its broad application in protein purification, only little is known about the binding properties of the His-tag, and therefore almost no thermodynamic and kinetic data are available. In this study, we investigated the binding mechanism of His-tags to Ni2+ -NTA. Different series of oligohistidines and mixed oligohistidines/oligoalanines were synthesized using automated solid-phase peptide synthesis (SPPS). Binding to Ni2+ -NTA was analyzed both qualitatively and quantitatively with surface plasmon resonance (SPR) using commercially available NTA sensor chips from Biacore. The hexahistidine tag shows an apparent equilibrium dissociation constant (KD) of 14,±,1,nM and thus the highest affinity of the peptides synthesized in this study. Furthermore, we could demonstrate that two His separated by either one or four residues are the preferred binding motifs within hexahis tag. Finally, elongation of these referred motifs decreased affinity, probably due to increased entropy costs upon binding. Copyright © 2009 John Wiley & Sons, Ltd. [source] Survey of the year 2005: literature on applications of isothermal titration calorimetryJOURNAL OF MOLECULAR RECOGNITION, Issue 1 2007Adessamad Ababou Abstract Isothermal titration calorimetry (ITC) can provide a full thermodynamic characterization of an interaction. Its usage does not suffer from constraints of molecular size, shape or chemical constitution. Neither is there any need for chemical modification or attachment to solid support. This ease of use has made it an invaluable instrumental resource and led to its appearance in many laboratories. Despite this, the value of the thermodynamic parameterization has, only quite recently, become widely appreciated. Although our understanding of the correlation between thermodynamic data and structural details continues to be somewhat naïve, a large number of publications have begun to improve the situation. In this overview of the literature for 2005, we have attempted to highlight works of interest and novelty. Furthermore, we draw attention to those works which we feel have provided a route to better analysis and increased our ability to understand the meaning of thermodynamic change on binding. Copyright © 2006 John Wiley & Sons, Ltd. [source] Benzhydrylamine linker grafting: a strategy for the improved synthesis of C -terminal peptide amides,JOURNAL OF PEPTIDE SCIENCE, Issue 10 2010Dianne Alewood Abstract The standard p -MBHA resin used during Boc-chemistry synthesis of peptides carrying C -terminal carboxamides is compromised by batch-to-batch variations in its performance. This can cause artificially ,difficult' couplings during peptide chain assembly, which may ultimately lead to failed syntheses given the inability to achieve acceptable coupling yields. To overcome these problems, we have developed a new approach by grafting a functionalized benzhydrylamine linker onto well-characterized and well-performing PAM resins. We combine optimized Boc-chemistry, high-performing PAM resins and new benzhydrylamine-based linkers to achieve improved syntheses of peptide amides. Here we present the synthesis of two new benzhydrylamine linkers and their attachment to selected PAM resins. This novel solid support was evaluated through the synthesis of selected ,difficult' conotoxins and monitoring the coupling efficiency using quantitative ninhydrin assay. The results show a superior performance of the novel linker solid support compared to the standard p -MBHA resins routinely used. In summary, we describe an alternative linker-resin system that allows improved access to C -terminal amide peptides employing Boc/Bzl chemistry. Copyright © 2010 European Peptide Society and John Wiley & Sons, Ltd. [source] Chemistry of ,-hydroxymethylserine: problems and solutions,JOURNAL OF PEPTIDE SCIENCE, Issue 11 2008Marcin Stasiak Abstract Further improvements related to the synthesis of peptides containing HmS are presented. Efficient synthetic protocols have been developed to synthesize "difficult" sequences containing a C -terminal HmS residue, MeA,HmS or consecutive HmS. Preparative methods for orthogonal N - and/or C -protected HmS(Ipr) derivatives are described. Their compatibility with standard solution or solid-phase peptide chemistry protocols allows synthetic flexibility toward HmS-containing peptides. In the synthesis of the sterically hindered dipeptides with the C -terminal HmS(Ipr) residue, HATU proves the highest efficiency, as compared with the fluoride and PyBroP/DMAP coupling methods. The HATU method also outperforms the fluoride activation in the solid-phase assembly of HmS homosequence. Specific protocols are described to overcome an undesired cyclization to diketopiperazines that occurs during the removal of Fmoc from dipeptides with the C -terminal HmS(Ipr) or HmS residues, thus precluding their C , N elongation. The successful protocols involve: (i) the 2 + 1 condensation using mixed anhydride activation yielding the desired product with the highest optical integrity or (ii) use of the 2-chlorotrityl resin as a solid support sterically suppressing the undesired cleavage due to diketopiperazine formation. The latter approach allows the mild conditions of peptide cleavage from solid support, preserving the isopropylidene protection and minimizing the undesired N , O -acyl migration that was observed under prolonged acid treatment used for cleaving the HmS peptide from the Wang resin. Copyright © 2008 European Peptide Society and John Wiley & Sons, Ltd. [source] | |||||||||||||||||||||||||||||||||||||