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Conjugation
Kinds of Conjugation Terms modified by Conjugation Selected AbstractsFacile Functionalization and Phase Reduction Route of Magnetic Iron Oxide Nanoparticles for Conjugation of Matrix Metalloproteinase,ADVANCED ENGINEERING MATERIALS, Issue 6 2010Dan Li Abstract A protocol for the simultaneous functionalization and phase reduction route of iron oxide magnetic nanoparticles (MNPs) and its further bioconjugation is presented. It was found that surface functionalization of maghemite (,-Fe2O3) nanoparticles with mercaptopropyltrimethoxysilane (MPTMS) under anoxic environment at above 80,°C promotes in situ conversion to magnetite (Fe3O4). Full conversion to Fe3O4, as probed by Mössbauer spectroscopy, with accompanied increase in the composite saturation magnetization, was achieved at 120,°C. By controlling the MPTMS concentration, the resultant silane-MNPs morphology can be tuned from having homogeneous thin layer (<1,nm) to thick continuous silane with embedded MNP multicores. Likewise the amount of surface distal thiol moieties was dependent on the silanization conditions. The density of distal thiols (i.e., amount of thiol per surface area) and resultant aggregate size have direct impact on the attachment, as well as the activity and reusability of the conjugated matrix metalloproteinase (MMP-2, using sulfo-SMCC as crosslinker). The work has important implication to the field of magneto-chemotherapeutics, where spatial control of conjugated active biomolecules under magnetic field and T2 -weighted MRI contrast can be achieved simultaneously. [source] Click Chemistry Inspired Synthesis of Novel Ferrocenyl-Substituted Amino Acids or PeptidesEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 13 2009V. Sai Sudhir Abstract This work reports on the synthesis of a wide range of ferrocenyl-substituted amino acids and peptides in excellent yield. Conjugation is established via copper-catalyzed 1,3-dipolar cycloaddition. Two complementary strategies were employed for conjugation, one involving cycloaddition of amino acid derived azides with ethynyl ferrocene 1 and the other involves cycloaddition between amino acid derived alkynes with ferrocene-derived azides 2 and 3. Labeling of amino acids at multiple sites with ferrocene is discussed. A new route to 1,1,-unsymmetrically substituted ferrocene conjugates is reported. A novel ferrocenophane 19 is accessed via bimolecular condensation of amino acid derived bis-alkyne 9b with the azide 2. The electrochemical behavior of some selected ferrocene conjugates has been studied by cyclic voltammetry.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009) [source] Poly(9,9-dioctylfluorene)-Based Conjugated Polyelectrolyte: Extended ,-Electron Conjugation Induced by Complexation with a Surfactant ZwitterionADVANCED MATERIALS, Issue 18 2010Giuseppina Pace We report on a conjugated polyelectrolyte (CPE) based on fluorene repeat units, which forms a supramolecular complex with a zwitterion surfactant. The complex self-assembles into multilamellar structures on solid substrates. The luminescence efficiency, low in the uncomplexed polymer, is strongly increased after complexation. This originates from the phase segregation between the aromatic backbone and ionic sides, reducing conformational defects and ionic dipole-induced quenching. [source] Facile Conjugation of Biomolecules onto Surfaces via Mussel Adhesive Protein Inspired CoatingsADVANCED MATERIALS, Issue 4 2009Haeshin Lee A new surface bioconjugation strategy is presented. A polydopamine surface coating provides chemical activation on material surfaces, is resistant to hydrolysis, and offers selectivity in coupling of biomolecules via nucleophilic groups through simple pH control. Control of orientation of immobilized biomolecules may be possible using terminally modified DNA or His-containing proteins. [source] Conjugation of methotrexate to immunoglobulins kills macrophages by Fc receptor mediated uptake?INTERNATIONAL JOURNAL OF LABORATORY HEMATOLOGY, Issue 3 2008X. WANG Summary The aim of this study was to conjugate methotrexate (MTX) with intravenous immunoglobulin (IVIG) and investigate whether the conjugate produce selective cytotoxicity on macrophages to provide a new strategy for the management of idiopathic thrombocytopenic purpura. MTX was bound to IVIG via human serum albumin as an intermediary. The binding activity of the Fc fragment of the conjugate was assayed by flow cytometry. The selective cytotoxicity of the conjugate was determined by trypan blue exclusion. After conjugating, the binding activity of the conjugate to Fc receptors did not diminish when compared with IVIG. In vitro, the conjugate showed significantly higher cytotoxicity to macrophages than Hela cells. The conjugate of IVIG and MTX showed potent and selective cytotoxicity to macrophages in vitro. [source] Conjugation of isometamidium chloride to antibodies and the use of the conjugate against the haemoflagellate, Cryptobia salmositica Katz, 1951: an immuno-chemotherapeutic strategyJOURNAL OF FISH DISEASES, Issue 8 2001B F Ardelli The trypanocidal drug isometamidium chloride (Samorin) was conjugated to polyclonal and monoclonal antibodies produced against the pathogenic haemoflagellate Cryptobia salmositica. Under in vitro conditions the unconjugated drug normally accumulates rapidly in the kinetoplast in the parasite; however, once it was conjugated to antibodies (either polyclonal or monoclonal) it was found throughout the parasite. Isometamidium conjugated to polyclonal antibodies lysed C. salmositica under in vitro conditions, but parasites were not agglutinated. In contrast, isometamidium conjugated to monoclonal antibodies (against a 200 kDa surface membrane glycoprotein) did not lyse C. salmositica, but parasites were agglutinated. Because of the low efficacy of the monoclonal conjugate against the parasite in vitro, its cryptobiocidal effect was not evaluated further. The infectivity of C. salmositica (incubated either in culture medium or whole blood) was reduced in fish after in vitro exposure to isometamidium conjugated to polyclonal antibodies. Parasitaemias were reduced in infected chinook salmon, Oncorhynchus tshawytscha, after treatment with isometamidium conjugated to polyclonal antibodies. [source] Synthesis and reactivity of spiro[1,3,4-thiadiazoline-2,4,-thioflavans] and analoguesJOURNAL OF HETEROCYCLIC CHEMISTRY, Issue 3 2009László Somogyi Racemic thioflavanone (thio)acylhydrazones undergo transformation into racemic 3-acetylspiro[1,3,4-oxa(thia)-diazoline-2,4,-thioflavans] with trans O(1) or S(1) and Ph(2,eq) under acetylating conditions. Conjugation between the ethylenic bond and sp2 C(4) in thioflavones encumber both the formation of (thio)acylhydrazones and their subsequent spirocyclization. On the other hand, subsequent dehydrogenation of the thiopyran moiety of spiro compounds results in formation of sp2 C(4) and simultaneous degradation of the spirodiazoline ring. J. Heterocyclic Chem., 46, 399 (2009). [source] Synthesis and preliminary biological evaluation of a 99mTc-labeled hypericin derivative as a necrosis avid imaging agentJOURNAL OF LABELLED COMPOUNDS AND RADIOPHARMACEUTICALS, Issue 1 2008Humphrey Fonge Abstract Mono-[123I]iodohypericin and mono-[123I]iodohypericin monocarboxylic acid are iodine-123-labeled hypericin derivatives which have shown great promise in preclinical studies as necrosis avid imaging agents in animal models of infarction. In view of the more attractive properties of a 99mTc-labeled hypericin derivative, we have synthesized a conjugate of protohypericin monocarboxylic acid with S -benzoylmercaptoacetyldiglycyl-diaminopentane in an overall yield of 15%. The conjugate was labeled with technetium-99m by exchange labeling at pH 10 in a labeling yield of 95% followed by photocyclization to yield 99mTc-mercaptoacetyldiglycyl-1,5-diaminopentylene hypericincarboxamide (99mTc-13). The negatively charged 99mTc-13 complex was purified by reversed phase high-pressure liquid chromatography and the log,P7.4 was determined to be 2.36. In normal NMRI mice, the complex showed slow hepatobiliary clearance while plasma clearance was rapid. The tracer was evaluated in rats with reperfused hepatic infarction by ex vivo autoradiography, gamma counting and histochemical techniques. Unlike the radioiodinated hypericin derivatives, the new tracer agent did not show preferential uptake in necrotic tissue on autoradiography and gamma counting techniques. Conjugation of hypericin with a 99mTc-chelate, resulting in a change in size, charge and lipophilicity, had a profound effect on the necrosis avidity of the tracer agent. The results show that 99mTc-13 is not suitable for imaging necrosis. Copyright © 2008 John Wiley & Sons, Ltd. [source] Conjugation of two functional groups through an unsaturated systemJOURNAL OF PHYSICAL ORGANIC CHEMISTRY, Issue 1 2006Otto Exner Abstract Energies of 51 1-(E),4-(E)-disubstituted 1,3-butadienes (1), 36 1,4-disubstituted benzenes (2) and 36 (E)-1,2-disubstituted ethenes (3) with dipolar substituents were calculated at the B3LYP/6,311,+,G(d,p) level and evaluated in terms of isodesmic reactions expressing the interaction of substituents through the conjugated system. The energy of interaction reaches up to 40,kJ,mol,1, it is roughly similar in the three series and most regular in the series 1. While its correlation within the framework of dual substituent parameter analysis lacks physical meaning, it is possible to separate the conjugative (resonance) component by subtracting the inductive component with reference to 1,4-disubstituted bicyclo[2.2.2]octanes 4. The conjugative interaction is strongly stabilizing for the combination acceptor,donor and destabilizing for two donors; in these cases it is parallel to changes of geometry as they are predicted by the common resonance equations. Interaction of two acceptors is weak; in addition, there are groups that cannot be classified either as donors or as acceptors. Therefore, one can construct a scale of the resonance ability of donors in conjugation with an acceptor and vice versa, but it is not possible to express the interaction of two donors or of two acceptors on a unified scale for all substituents. The resonance description is certainly appropriate for the typical examples (interaction of NO2 and NH2) but should not be generalized to all possible structures. Copyright © 2005 John Wiley & Sons, Ltd. [source] Influence of Maillard reaction conditions on the antigenicity of bovine ,-lactalbumin using response surface methodologyJOURNAL OF THE SCIENCE OF FOOD AND AGRICULTURE, Issue 14 2009Guanhao Bu Abstract BACKGROUND: Maillard reaction can modify functional properties of proteins. Bovine ,-lactalbumin (,-LA) is often supplemented to the new generation of infant formulae, but it is considered to be a main allergen. However, there is little information on the effect of Maillard reaction on ,-LA antigenicity. The objective of this study was to investigate the influence of Maillard reaction on the antigenicity of ,-LA in conjugates of whey protein isolate (WPI) with glucose under different conditions of protein/sugar weight ratio (0.17,7.83), temperature (40,60 °C) and time (24,120 h) using response surface methodology. RESULTS: Conjugation of WPI with glucose markedly reduced the antigenicity of ,-LA. This reduction in antigenicity could be controlled by regulating the three independent variables weight ratio, temperature and time. A model of optimal reaction conditions for lower antigenicity of ,-LA was established. According to the model, the minimum antigenicity of ,-LA was achieved at 52.8 °C, 78 h and 5.96:1 WPI/glucose weight ratio. WPI/glucose weight ratio had the greatest effect on the antigenicity of ,-LA, while reaction temperature influenced ,-LA antigenicity to a lesser extent. CONCLUSION: Well-controlled Maillard reaction between WPI and glucose is an efficient method to reduce ,-LA antigencity. Copyright © 2009 Society of Chemical Industry [source] A Polycation Scaffold Presenting Tunable "Click" Sites: Conjugation to Carbohydrate Ligands and Examination of Hepatocyte-Targeted pDNA DeliveryMACROMOLECULAR BIOSCIENCE, Issue 6 2010Chen-Chang Lee Abstract A versatile polycation scaffold that can easily be modified with targeting ligands has been designed, synthesized, and characterized. A series of galactose-containing polymers has been produced to demonstrate the ease of modification of this polynucleotide delivery vehicle motif via the click reaction and to study how various structural modifications affect recognition by ASGPr on hepatocytes. A small library of structures was created where DCS and alkyl spacer length between the targeting group and the polymer backbone was varied. The novel polymer scaffold described proves to be a valuable tool for understanding structure/activity relationships of complexes made with receptor-targeted polymers. [source] Geometries and Electronic Structures of Co-Oligomers and Co-Polymers Based on Tricyclic Nonclassical Thiophene: A Theoretical StudyMACROMOLECULAR THEORY AND SIMULATIONS, Issue 7-8 2008Yangwu Fu Abstract The geometries and electronic properties of four copolymers based on tricyclic nonclassical thiophene were studied using DFT at the B3LYP/6-31G(d) level. Bond lengths and their alternation, electron densities at BCPs, NICS, and WBIs were analyzed and correlated with the energy gap. The results show that the degree of conjugation increases upon main chain extension. The energy gap decreased steadily with increasing degree of polymerization. Conjugation is stronger in the central than in the outer section. The results suggest that the narrow HOMO/LUMO separation of tricyclic nonclassical thiophenes can be carried over to their co-polymers by using them as building blocks for the co-polymers. [source] Conjugation mediates transfer of the Ll.LtrB group II intron between different bacterial speciesMOLECULAR MICROBIOLOGY, Issue 5 2004Kamila Belhocine Summary Some self-splicing group II introns (ribozymes) are mobile retroelements. These retroelements, which can insert themselves into cognate intronless alleles or ectopic sites by reverse splicing, are thought to be the evolutionary progenitors of the widely distributed eukaryotic spliceosomal introns. Lateral or horizontal transmission of introns (i.e. between species), although never experimentally demonstrated, is a well-accepted model for intron dispersal and evolution. Horizontal transfer of the ancestral bacterial group II introns may have contributed to the dispersal and wide distribution of spliceosomal introns present in modern eukaryotic genomes. Here, the Ll.LtrB group II intron from the Gram-positive bacterium Lactococcus lactis was used as a model system to address the dissemination of introns in the bacterial kingdom. We report the first experimental demonstration of horizontal transfer of a group II intron. We show that the Ll.LtrB group II intron, originally discovered on an L. lactis conjugative plasmid (pRS01) and within a chromosomally located sex factor in L. lactis 712, invades new sites using both retrohoming and retrotransposition pathways after its transfer by conjugation. Ll.LtrB lateral transfer is shown among different L. lactis strains (intraspecies) (retrohoming and retrotransposition) and between L. lactis and Enterococcus faecalis (interspecies) (retrohoming). These results shed light on long-standing questions about intron evolution and propagation, and demonstrate that conjugation is one of the mechanisms by which group II introns are, and probably were, broadly disseminated between widely diverged organisms. [source] Preferred conformations in the solid state of some ,-(p -phenylsulfinyl)- p -substituted acetophenonesACTA CRYSTALLOGRAPHICA SECTION B, Issue 1 2000Paulo R. Olivato Information on the geometrical structures of ,-(p -phenylsulfinyl)- p -substituted acetophenones X,PhC(O)CH2S(O)Ph,Y [X = OMe, Y = H (1); X = NO2, Y = OMe (2); X = OMe, Y = NO2 (3); IUPAC names: (1) 4-methoxyphenyl phenylsulfinylmethyl ketone; (2) 4-nitrophenyl 4-methoxyphenylsulfinylmethyl ketone; (3) 4-methoxyphenyl 4-nitrophenylsulfinylmethyl ketone] have been obtained from X-ray diffraction analyses. A comparison of these results with those previously obtained from X-ray diffraction and ab initio computations of ,-methylsulfinylacetophenone, PhC(O)CH2S(O)Me, indicated that (1) and (2) adopt in the crystal a cis1 conformation and (3) assumes a quasi-gauche geometry. The stabilization of these conformations in the crystal is discussed in terms of the dipole moment coupling, Coulombic and intramolecular charge transfer interactions between the oppositely charged atoms of the C=O and S=O dipoles. The p -substituted benzene ring is quasi -coplanar with the sulfinyl group for (1) and (3), but is quasi -perpendicular for (2). Conjugation and repulsion between the sulfinyl sulfur lone pair and the ,-benzene ring seem to be responsible for the observed geometries. [source] Direct Polymerase Synthesis of Reactive Aldehyde-Functionalized DNA and Its Conjugation and Staining with Hydrazines,ANGEWANDTE CHEMIE, Issue 6 2010Veronika Raindlová In zwei Stufen zu reaktiver Aldehyd-modifizierter DNA: durch Suzuki-Kreuzkupplung halogenierter Nucleosidtriphosphate (dNTPs) mit 4-Formylthiophen-2-boronsäure und Polymerase- vermittelten Einbau der modifizierten Nucleotide in DNA (siehe Schema; PEX=Primerverlängerung, PCR=Polymerasekettenreaktion). Die Bildung von Hydrazonen mit Arylhydrazinen unter wässrigen Bedingungen wurde zum Anfärben der DNA verwendet. [source] Conjugation to nanoparticles can increase antimicrobial activity of lysozymeBIOTECHNOLOGY & BIOENGINEERING, Issue 3 2008Article first published online: 25 APR 200 No abstract is available for this article. [source] Cationic Liposome Conjugation to Recombinant Adenoviral Vector Reduces Viral AntigenicityCANCER SCIENCE, Issue 4 2000Atsushi Natsume Adenoviral (Ad) vectors are commonly used in gene therapy trials because of their efficiency in gene transfer. However, their use is limited by immune responses that reduce transgene expression and decrease the efficacy of repeated vector administration. In this study, we demonstrated that conjugation of Ad vector with our novel cationic liposomes could reduce viral antigenicity in vivo. Mice subcutaneously injected with liposome-conjugated Ad vector showed a 6.5-fold reduction of anti-Ad antibodies with neutralizing activity, compared to those with unconjugated Ad vector. Interestingly, we also found that the conjugated vector is less susceptible to inactivation by neutralizing antibodies in vitro and in vivo. Our results suggest that liposome conjugation reduces viral antigenicity, shields vectors from neutralizing antibody, and may allow repeated Ad vector administration. [source] Influence on antiproliferative activity of structural modification and conjugation of gonadotropin-releasing hormone (GnRH) analoguesCELL PROLIFERATION, Issue 5 2000A. Kálnay Abstract The effect of various GnRH analogues, and their conjugates on proliferation, clonogenicity and cell cycle phase distribution of MCF-7 and Ishikawa human cancer cell lines was studied. GnRH-III, a sea lamprey GnRH analogue reduced cell proliferation by 35% and clonogenicity by 55%. Structural modifications either decreased, or did not alter biological activity. Conjugation of GnRH analogues including MI-1544, MI-1892, and GnRH-III with poly(N-vinylpyrrolidone-co-maleic acid) (P) through a tetrapeptide spacer GFLG(X) substantially increased the inhibitory effect of the GnRH analogues. The conjugate P-X-GnRH-III induced significant accumulation of cells in the G2/M phase; from 8% to 15.6% at 24 h and 9.8% to 15% at 48 h. It was concluded that conjugation of various GnRH analogues substantially enhanced their antiproliferative activity, strongly reduced cell clonogenicity and retarded cell progression through the cell division cycle at the G2/M phase. [source] Shuttling Gold Nanoparticles into Tumoral Cells with an Amphipathic Proline-Rich PeptideCHEMBIOCHEM, Issue 6 2009Sílvia Pujals Abstract Golden bullets: The amphipathic proline-rich cell-penetrating peptide sweet arrow peptide (SAP) is able to transport 12 nm gold nanoparticles efficiently into HeLa cells, as observed by three microscopy techniques: transmission electron microscopy (TEM), confocal laser scanning microscopy (CLSM) and transmission X-ray microscopy (TXM). Multiconjugation to such nanoparticles may provide a convenient method for unifying the key drug properties of high activity, capacity to home onto targets and delivery to therapeutic places of action. Cell-penetrating peptides (CPPs) are a potential tool for intracellular delivery of different kinds of cargoes. Because of their growing use in nanobiomedicine, both for diagnostics and for treatment, metal nanoparticles are an interesting cargo for CPPs. Here, gold nanoparticles (AuNps) and the amphipathic proline-rich peptide SAP have been used. Conjugation of the peptide onto the AuNps was achieved by addition of a cysteine to the SAP sequence for thiol chemisorption on gold, and the attachment was confirmed by visible spectroscopy, dynamic light scattering (DLS), ,-potential (ZP), stability towards ionic strength (as high as 1,M NaCl), X-ray photoelectron spectroscopy (XPS) and high-resolution transmission electron microscopy (HR-TEM) coupled to electron energy loss spectroscopy (EELS). AuNp-C-SAP internalization in HeLa cells was observed by three different microscopy techniques,TEM, confocal laser scanning microscopy (CLSM) and transmission X-ray microscopy (TXM),and all of them have confirmed the effective intracellular delivery of AuNps by SAP. [source] ChemInform Abstract: The Oxime Bond Formation as an Efficient Tool for the Conjugation of Ruthenium Complexes to Oligonucleotides and Peptides.CHEMINFORM, Issue 7 2008Mathilde Villien 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] Tetraamine-Derived Bifunctional Chelators for Technetium-99m Labelling: Synthesis, Bioconjugation and Evaluation as Targeted SPECT Imaging Probes for GRP-Receptor-Positive Tumours,CHEMISTRY - A EUROPEAN JOURNAL, Issue 7 2010Keelara Abiraj Dr. Abstract Owing to its optimal nuclear properties, ready availability, low cost and favourable dosimetry, 99mTc continues to be the ideal radioisotope for medical-imaging applications. Bifunctional chelators based on a tetraamine framework exhibit facile complexation with Tc(V)O2 to form monocationic species with high in vivo stability and significant hydrophilicity, which leads to favourable pharmacokinetics. The synthesis of a series of 1,4,8,11-tetraazaundecane derivatives (01,06) containing different functional groups at the 6-position for the conjugation of biomolecules and subsequent labelling with 99mTc is described herein. The chelator 01 was used as a starting material for the facile synthesis of chelators functionalised with OH (02), N3 (04) and O -succinyl ester (05) groups. A straightforward and easy synthesis of carboxyl-functionalised tetraamine-based chelator 06 was achieved by using inexpensive and commercially available starting materials. Conjugation of 06 to a potent bombesin-antagonist peptide and subsequent labelling with 99mTc afforded the radiotracer 99mTc-N4-BB-ANT, with radiolabelling yields of >97,% at a specific activity of 37,GBq,,mol,1. An IC50 value of (3.7±1.3),nM was obtained, which confirmed the high affinity of the conjugate to the gastrin-releasing-peptide receptor (GRPr). Immunofluorescence and calcium mobilisation assays confirmed the strong antagonist properties of the conjugate. In vivo pharmacokinetic studies of 99mTc-N4-BB-ANT showed high and specific uptake in PC3 xenografts and in other GRPr-positive organs. The tumour uptake was (22.5±2.6),% injected activity per gram (%,IA,g,1) at 1,h post injection (p.i.). and increased to (29.9±4.0),%,IA,g,1 at 4,h p.i. The SPECT/computed tomography (CT) images showed high tumour uptake, clear background and negligible radioactivity in the abdomen. The promising preclinical results of 99mTc-N4-BB-ANT warrant its potential candidature for clinical translation. [source] Direct Estimate of the Strength of Conjugation and Hyperconjugation by the Energy Decomposition Analysis MethodCHEMISTRY - A EUROPEAN JOURNAL, Issue 13 2006Israel Fernández Dr. Abstract The intrinsic strength of , interactions in conjugated and hyperconjugated molecules has been calculated using density functional theory by energy decomposition analysis (EDA) of the interaction energy between the conjugating fragments. The results of the EDA of the trans -polyenes H2CCH(HCCH)nCHCH2 (n=1,3) show that the strength of , conjugation for each CC moiety is higher than in trans -1,3-butadiene. The absolute values for the conjugation between SiSi , bonds are around two-thirds of the conjugation between CC bonds but the relative contributions of ,E, to ,Eorb in the all-silicon systems are higher than in the carbon compounds. The , conjugation between CC and CO or CNH bonds in H2CCHC(H)O and H2CCHC(H)NH is comparable to the strength of the conjugation between CC bonds. The , conjugation in H2CCHC(R)O decreases when R=Me, OH, and NH2 while it increases when R=halogen. The hyperconjugation in ethane is around a quarter as strong as the , conjugation in ethyne. Very strong hyperconjugation is found in the central CC bonds in cubylcubane and tetrahedranyltetrahedrane. The hyperconjugation in substituted ethanes X3CCY3 (X,Y=Me, SiH3, F, Cl) is stronger than in the parent compound particularly when X,Y=SiH3 and Cl. The hyperconjugation in donor,acceptor-substituted ethanes may be very strong; the largest ,E, value was calculated for (SiH3)3CCCl3 in which the hyperconjugation is stronger than the conjugation in ethene. The breakdown of the hyperconjugation in X3CCY3 shows that donation of the donor-substituted moiety to the acceptor group is as expected the most important contribution but the reverse interaction is not negligible. The relative strengths of the , interactions between two CC double bonds, one CC double bond and CH3 or CMe3 substituents, and between two CH3 or CMe3 groups, which are separated by one CC single bond, are in a ratio of 4:2:1. Very strong hyperconjugation is found in HCCC(SiH3)3 and HCCCCl3. The extra stabilization of alkenes and alkynes with central multiple bonds over their terminal isomers coming from hyperconjugation is bigger than the total energy difference between the isomeric species. The hyperconjugation in MeC(R)O is half as strong as the conjugation in H2CCHC(R)O and shows the same trend for different substituents R. Bond energies and lengths should not be used as indicators of the strength of hyperconjugation because the effect of , interactions and electrostatic forces may compensate for the hyperconjugative effect. [source] A Flexible Method for the Conjugation of Aminooxy Ligands to Preformed Complexes of Nucleic Acids and LipidsCHEMMEDCHEM, Issue 9 2008James Abstract Attachment of targeted ligands to nonviral DNA or RNA delivery systems is a promising strategy that seeks to overcome the poor target selectivity generally observed in systemic delivery applications. Several methods have been developed for the conjugation of ligands to lipids or polymers, however, direct conjugation of ligands onto lipid, or polymer,nucleic acid complexes is not as straightforward. Here, we examine an oximation approach to directly label a lipoplex formulation. Specifically, we report the synthesis of a cationic diketo lipid DMDK, and its use as a convenient ligation tool for attachment of aminooxy-functionalized reagents after its complexation with DNA. We demonstrate the feasibility of direct lipoplex labeling by attaching an aminooxy-functionalized fluorescent probe onto pre-formed plasmid DNA,DMDK lipoplexes (luciferase, GFP). The results reveal that DMDK protects DNA from degradation on exposure to either DNase or human cerebral spinal fluid, and that simple mixing of DMDK lipoplexes with the aminooxy probe labels the complexes without sacrificing transfection efficiency. The biocompatibility and selectivity of this method, as well as the ease of bioconjugation, make this labeling approach ideal for biological applications. [source] An HPLC/mass spectrometry platform for the development of multimodality contrast agents and targeted therapeutics: prostate-specific membrane antigen small molecule derivativesCONTRAST MEDIA & MOLECULAR IMAGING, Issue 5 2006Valerie Humblet Abstract The production of disease-targeted agents requires the covalent conjugation of a targeting molecule with a contrast agent or therapeutic, followed by purification of the product to homogeneity. Typical targeting molecules, such as small molecules and peptides, often have high charge-to-mass ratios and/or hydrophobicity. Contrast agents and therapeutics themselves are also diverse, and include lanthanide chelates for MRI, 99mTc chelates for SPECT, 90Y chelates for radiotherapy, 18F derivatives for PET, and heptamethine indocyanines for near-infrared fluorescent optical imaging. We have constructed a general-purpose HPLC/mass spectrometry platform capable of purifying virtually any targeted agent for any modality. The analytical sub-system is composed of a single dual-head pump that directs mobile phase to either a hot cell for the purification of radioactive agents or to an ES-TOF MS for the purification of nonradioactive agents. Nonradioactive agents are also monitored during purification by ELSD, absorbance and fluorescence. The preparative sub-system is composed of columns and procedures that permit rapid scaling from the analytical system. To demonstrate the platform's utility, we describe the preparation of five small molecule derivatives specific for prostate-specific membrane antigen (PSMA): a gadolinium derivative for MRI, indium, rhenium and technetium derivatives for SPECT, and an yttrium derivative for radiotherapy. All five compounds are derived from a highly anionic targeting ligand engineered to have a single nucleophile for N -hydroxysuccinimide-based conjugation. We also describe optimized column/mobile phase combinations and mass spectrometry settings for each class of agent, and discuss strategies for purifying molecules with extreme charge and/or hydrophobicity. Taken together, our study should expedite the development of disease-targeted, multimodality diagnostic and therapeutic agents. Copyright © 2006 John Wiley & Sons, Ltd. [source] XSUMO-1 is required for normal mesoderm induction and axis elongation during early Xenopus developmentDEVELOPMENTAL DYNAMICS, Issue 10 2007Akira Yukita Abstract The small ubiquitin-related modifier (SUMO) is a member of the ubiquitin-like protein family, and SUMO conjugation (SUMOylation) resembles ubiquitination. Despite many SUMOylation target proteins being reported, the role of this system in vertebrate development remains unclear. We inhibited the function of Xenopus SUMO-1 (XSUMO-1) using a morpholino antisense oligo against XSUMO-1 (XSUMO-1-MO) to clarify the role of SUMOylation. XSUMO-1-MO inhibited normal axis formation in embryos and elongation of activin-treated animal caps. The expression of several mesoderm markers was reduced by XSUMO-1-MO. We measured activin-like activity by using a reporter construct containing a multimer of activin-responsive elements from the Goosecoid promoter, [DE(6x)Luc]. This assay showed that XSUMO-1-MO directly inhibited activin/nodal signaling. Furthermore, XSUMO-1-MO inhibited ectopic axis formation induced by XSmad2, and XSmad2/4 mRNA could not rescue the axis elongation defect induced by XSUMO-1-MO. These results suggested that XSUMO-1 is required for normal axis elongation, at least partly mediating activin/nodal signaling. Developmental Dynamics 236:2757,2766, 2007. © 2007 Wiley-Liss, Inc. [source] Cytotoxicity of doxorubicin-loaded Con A-liposomesDRUG DEVELOPMENT RESEARCH, Issue 5 2006Hercília Maria Lins Rolim Santos Abstract The present study investigated the potential of Concanavalin A lectin (Con A) conjugated to liposomes (Con A-liposomes) for targeting doxorubicin (DOX) to cells. The physicochemical properties and the cytotoxicity of DOX-loaded Con A-liposomes were evaluated. DOX-loaded Con A-liposomes were prepared by incubation of DOX-loaded liposomes with a Con A-SATA derivative. Lectin biological activity was monitored before and after conjugation by a hemagglutinating assay. The cytotoxicity of DOX-loaded Con A-liposomes was evaluated in terms of the inhibition of NCI-H299 and HEp-2 cell proliferation using the MTT method. The affinity of lectinized liposomes with these cells was thus assessed by evaluating the cytotoxic effect of the DOX released into cells. Stable DOX-loaded Con A-liposomes were obtained and their high affinity for cells was corroborated. The encapsulation of DOX into Con A-liposomes produced an inhibition of roughly 70% of Hep-2 cell proliferation and 50% of cell inhibition was verified on HCI-H292. DOX in solution was able to inhibit only 20% of cell proliferation for both cell lines. Unloaded Con A-liposomes were not cytotoxic. The encapsulation of DOX into Con A-liposomes improves drug penetration into cells, thereby enhancing its cytotoxicity, especially in Hep-2 cells. Drug Dev. Res. 67:430,437, 2006. © 2006 Wiley-Liss, Inc. [source] Prediction of polymorphic N -acetylation of new drug candidates by correlation with human NAT1 and NAT2DRUG DEVELOPMENT RESEARCH, Issue 1 2002Katalin Jemnitz Abstract Due to interindividual variation in N -acetyltransferase 2 (NAT2) activity, pharmaceutical companies face the problem of polymorphic metabolism in drugs that are metabolized mainly or exclusively by this enzyme. An in vitro method has been developed to predict in vivo polymorphic N -acetylation at an early stage of drug development. Two new type 5H-2,3-benzodiazepine derivatives, Nerisopam (NER) with anxiolytic activity and GYKI47261 with antiepileptic activity, are metabolized mainly by N -acetylation in the rat and human. The selectivity of human N -acetyltransferases (NAT1,2) to form the acetylated metabolites has been investigated by correlation analysis. Twelve human liver samples were characterized for NAT1 and NAT2 phenotype based on their enzyme activity toward two selective NAT1 (p -aminobenzoic acid, PABA; p -aminosalicylic acid, PAS) and two selective NAT2 (sulfamethazine, SMZ; procainamide, PROC) substrates. Significant correlation was found between enzyme activities NAT1PABA/NAT1PAS and NAT2SMZ/NAT2PROC, respectively, and no correlation was observed comparing enzyme activities toward NAT1PABA/NAT2PROC. Enzyme activities using NER and GYKI 47261 as substrates were compared to activities obtained with NAT1 and NAT2 selective substrates, and the correlation coefficients were calculated. Good correlation was established between the rates of acetylation of the two drugs and that of the NAT2 selective substrate (NER/NAT2SMZ, r2=0.91, GYKI 47261/NAT2SMZ, r2=0.91). In contrast, no correlation was found between the rate of conjugation of the drugs and that of NAT1 selective substrate (NER/NAT1PABA, r2=0.022, GYKI 47261/NAT1PABA, r2=0.0004), suggesting polymorphic in vivo metabolism, since both drugs are acetylated preferably by NAT2. According to our results, correlation analysis based on in vitro acetylation activity may be used to predict in vivo polymorphic metabolism. Drug Dev. Res. 56:17,22, 2002. © 2002 Wiley-Liss, Inc. [source] Progress of Untreated Massive Cardiac Echinococcosis,Echocardiographic Follow-UpECHOCARDIOGRAPHY, Issue 9 2006Serdar Soydinc M.D. A 56-year-old man was admitted with chest pain and dyspnea. Echocardiographic evaluation revealed a giant cystic cardiac mass with multiple loculations at interventricular septum extended to inferoposterior region protruding inside the cavity. The patient refused surgical therapy. His complaints persisted without significant changes after 5 months. Second echocardiographic evaluation revealed conjugation of previous multiple cyst to gigantic intramyocardial cyst and minimal pericardial effusion. We intend to illustrate herein an unusual echocardiographic appearance and progress of an untreated massive "cardiac echinococcosis." If cardiac hydatid cyst is left untreated it may transform to large cavity with a high risk of rupture. [source] Adsorptive Stripping Voltammetric Detection of Tea Polyphenols at Multiwalled Carbon Nanotubes-Chitosan Composite ElectrodeELECTROANALYSIS, Issue 6 2009Deyin Guo Abstract This study reports the catalytic oxidation and detection of tea polyphenols (TPs) at glassy-carbon electrode modified with multiwalled carbon nanotubes-chitosan (MWCNTs-CS) film. The adsorption of TPs at the surface of the MWCNTs through ,,, conjugation prevents the aggregation of nanotubes and induces a stable MWCNTs suspension in water over 30 days. Based on the adsorptive accumulation of polyphenols at MWCNTs, TPs is sensitively and selectively detected by adsorptive stripping voltammetry. The accumulation conditions and pH effect on the adsorptive stripping detection were examined. The linear range was found to be 100 to 1000,mg L,1 with a detection limit of 10,mg L,1 (S/N=3) for 2.5,min accumulation. Additionally, the MWCNTs-CS electrode is easily renewed by applying positive potential to remove the adsorbed TPs. This method was successfully applied to determine TPs in commercially available teas with satisfied result compared with that of conventional spectrometric analysis. [source] Capillary electrophoresis of liposomes functionalized for protein bindingELECTROPHORESIS, Issue 20 2006Gerhard Bilek Abstract CE enabled assessing the attachment of hexa-histidine-tagged proteins to functionalized phospholipid liposomes. The liposomes were made of 1-palmitoyl-2-oleoyl- sn -glycero-3-phosphocholine, phosphatidyl-ethanolamine, cholesterol and distearoyl-glycero-3-phosphoethanolamine- N -methoxy(polyethylene glycol) in a molar ratio of 29:26:40:5. The unilamellar vesicles, which had an average diameter of 170,nm, were labelled by inclusion of FITC-dextran for fluorescence detection. CE was carried out in poly(vinyl alcohol) (PVA)-coated capillaries at 25°C with a BGE consisting of Tris-HCl (50,mM, pH,8.0). For conjugation of the liposomes with the proteins (soluble synthetic receptor fragments with molecular mass of 60 and 70,kDa, respectively), Ni2+ was implanted into the vesicle surface by an anchor lipid containing a nitrilotriacetate acid (NTA) group as complexation agent for the metal ions. The difference in surface charge enabled the separation of the different species of interest by CE: plain vesicles, vesicles functionalised with Ni-NTA, vesicle,protein complexes and the species formed upon removal of the Ni-ions by complexation with EDTA. Loss of the Ni-ions resulted in the release of the proteins and the reappearance of the plain Ni-free NTA-liposome species in the electropherograms. [source] | |||||||||||||||||||||||||||||||||||||||||||