Navegando por Palavras-chave "polymer"

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    Assessment of the Aggregation Propensity of the beta-amyloid Peptide During the Synthesis and when Free in Solution
    (Bentham Science Publ Ltd, 2013-08-01) Malavolta, Luciana [UNIFESP]; Pinto, Marcelo Rodrigo Silva [UNIFESP]; Nakaie, Clovis Ryuichi [UNIFESP]; Fac Ciencias Med Santa Casa Sao Paulo; Universidade Federal de São Paulo (UNIFESP)
    This work developed an alternative approach targeting the evaluation of the aggregation propensity of the (1-42) beta-amyloid peptide (Alzheimer's disease) and some segments, either attached to a polymer during their synthesis or when free in solution. The solvation behavior of peptide-resins was gauged by measuring the swelling of beads in a microscope and the degree of chain motion through EPR spectra of previously labeled resins with an amino acid-type probe. In terms of comparative solvent dissociation power towards aggregated structures, the findings revealed greater values of peptide-resin swelling, peptide chain mobility and solubility when in strong electron donor dimethylsulfoxide than in strong electron acceptor trifluoroethanol. Otherwise, the weakest chain-chain disruption power was verified for acetonitrile, an internally neutral solvent in terms of Lewis acid/base properties. In complement, fluorescence and light scattering experiments depicted that the 15-35 region plays an essential role in the amyloid peptide fibril formation capacity.
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    Direct electron paramagnetic resonance monitoring of the peptide synthesis coupling reaction in polymeric support
    (Elsevier B.V., 2006-06-14) Nakaie, Clovis R.; Malavolta, Luciana; Schreier, Shirley; Trovatti, Eliane; Marchetto, Reinaldo; Universidade Federal de São Paulo (UNIFESP); Universidade de São Paulo (USP); UNESP
    This work demonstrates, for the first time. a time-resolved electron paramagnetic resonance (EPR) monitoring of a chemical reaction occurring in a polymeric structure. the progress of the coupling of a N-alpha-tert-butyloxycarbonyl-2.2.6.6-tetramethylpiperidine-1-oxyl-4-amino-4-carboxylic acid (Boc-TOAC) spin probe to a model peptide-resin was followed through EPR spectra. Progressive line broadening of EPR peaks was observed, indicative of an increased population of immobilized spin probe molecules attached to the solid support. the time for spectral stabilization of this process coincided with that determined in a previous Coupling study. thereby validating this in situ quantitative monitoring of the reaction. in addition, the influence of polymer swelling degree and solvent viscosity, as well as of the steric hindrance within beads. on the rate of coupling reaction was also addressed. A deeper evaluation of the latter effect was possible by determining unusual polymer parameters such as the average site-site distance and site-concentration within resin beads in each solvent system. (c) 2006 Elsevier B.V. All rights reserved.
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    Importance of the solvation degree of peptide-resin beads for amine groups determination by the picric acid method
    (Sociedade Brasileira de Química, 2000-10-01) Cilli, Eduardo Maffud [UNIFESP]; Jubilut, Guita Nicolaewsky [UNIFESP]; Ribeiro, Suely C. F. [UNIFESP]; Oliveira, Eliandre [UNIFESP]; Nakaie, Clovis Ryuichi [UNIFESP]; Universidade Federal de São Paulo (UNIFESP)
    The classic and important picric acid method used in polymers biochemical and chemical fields of polymers for amine group quantification was chosen in this work as a model for evaluating the influence of the resin bead solvation during an analytical procedure. It was observed that this method, proposed almost three decades ago, failed to quantify amine groups of peptidyl-resin containing aggregating and polar sequence. This was due to inefficient solvation of resin beads when only CH2Cl2 was used for picrate anion binding and subsequent washing steps. It was demonstrated that the use of CH2Cl2/DMF (dimethylformamide) and CH2Cl2/EtOH solutions during these steps allows correct determination of peptidyl-resin amine groups. Besides the importance for the solid phase peptide synthesis methodology itself, these findings also represent the first quantitative demonstration of the relationship between solvation degree and the efficiency of a polymer-supported analytical method.
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    Novel Copoly(Styrene-Divinylbenzene)-Resins with Different Phenylmethylamine Groups for Use in Peptide Synthesis Method
    (Bentham Science Publ Ltd, 2015-01-01) Souza, Sinval Estevam Gregorio de [UNIFESP]; Malavolta, Luciana [UNIFESP]; Cilli, Eduardo Maffud [UNIFESP]; Schreier, Shirley [UNIFESP]; Jubilut, Guita Nicolaewsky [UNIFESP]; Nakaie, Clovis Ryuichi [UNIFESP]; Universidade Federal de São Paulo (UNIFESP); Santa Casa Sao Paulo Sch Med Sci; Unesp; Universidade de São Paulo (USP)
    Differently than the 4-methylbenzhydrylamine-resin (MBHAR) which contains a methyl group coupled to the phenylmethylamine-functionalized copoly(styrene-divinilbenzene) structure, alternative resins containing the electron-donating 4-tert-butyl-(BUBHAR) or the electron-withdrawing 2-chloro-(ClBHAR) and 2,4-chloro-(diClBHAR) groups were developed as potential supports for carboxamide peptide synthesis. Initially, a time-course investigation of HF cleavage reaction (0 degrees C) with these resins bearing the vasoconstrictor angiotensin II (AngII, DRVYIHPF) or its Gly(8)-AngII analogue revealed that the peptide-BUBHAR linkage is much more labile than those with ClBHAR or diClBHAR. HF cleavage times of near 2 h or longer than 24 h were needed for complete removal of peptide chains from these two classes of resin, respectively. By including MBHAR and benzhydrylamine-resins (BHAR) in this comparative study, the decreasing order of acid stability of the peptidyl-resin linkage was diClBHAR > ClBHAR > BHAR > MBHAR similar to BUBHAR. The same stability order was observed for the HCl/ propionic acid hydrolysis reaction (130 degrees C) with the Phe-or Gly-resins. These findings thus suggest that ClBHAR and diClBHAR are not appropriate for use in peptide synthesis. Nevertheless, these supports could still be tested as stationary phases for affinity chromatography. When placed into more apolar solvents, the beads of all of these resins exhibited a greater swelling (as measured by a microscope) or higher mobility of the polymer matrix (as measured with EPR experiments using spin-labeled beads). Moreover, under the latter approach, BUBHAR displayed a comparatively higher solvation degree than did MBHAR (in DCM, DMF and NMP), with slightly higher peptide synthesis yields as well.
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    Peptide dissociation in solution or bound to a polymer: comparative solvent effect
    (Elsevier B.V., 2004-10-11) Malavolta, L.; Nakaie, C. R.; Universidade Federal de São Paulo (UNIFESP)
    Dissociation of peptide when in solution or attached to a polymer was investigated. Magnified solvation of peptide-resins occurred in solvent with similar polarity. Conversely the solubilization of peptides was not usually directly related to the medium polarity. the greater the difference between acidity and basicity of solvent and its potential to form van der Waals interaction, the stronger its solubilization strength. Solvents with similar electrophilicity and nucleophilicity usually did not solvate aggregated peptide-resins nor dissolve peptides. the peptide solubilization in water-containing mixed solvents depended on combination of acidity/basicity of both components. Some criteria for choosing suitable solvents for peptide-resin solvation or peptide solubilization could be advanced. (C) 2004 Elsevier B.V. All rights reserved.
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    Polystyrene-type resin used for peptide synthesis: application for anion-exchange and affinity chromatography
    (Elsevier B.V., 2005-03-25) Carvalho, RSH; Ianzer, D. A.; Malavolta, L.; Rodrigues, M. M.; Cilli, E. M.; Nakaie, C. R.; Universidade Federal de São Paulo (UNIFESP); UNESP
    This paper deals with an unusual application for a copolymer of styrene-1 % divinylbenzene bearing high amount of aminomethyl groups for anion-exchange and affinity chromatography. the so-called aminomethyl resin (AMR), to date only employed for peptide synthesis, swelled appreciably in water and was used successfully to purify negatively charged peptides. By correlating swelling degree of beads with pH of the media, it was possible to estimate that the AMR amino group pK(a) is approximately 5.5. in addition, the synthesized acetyl-(NANP)(3)-AMR succeeded in the affinity interaction with large antibody molecules related to malaria transmission and raised previously against this dodecapeptide sequence. (C) 2004 Elsevier B.V. All rights reserved.
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    Solvation of polymers as model for solvent effect investigation: proposition of a novel polarity scale
    (Elsevier B.V., 2002-05-27) Malavolta, L.; Oliveira, E.; Cilli, E. M.; Nakaie, C. R.; Universidade Federal de São Paulo (UNIFESP); Univ Barcelona
    A precise understanding of the polymer solvation effect has been considered crucial to many modem methods, but its dependence on the polarity of the medium is still not entirely established. To more thoroughly address this issue, the swelling degrees of polymers with a great variety of structures. taken as solute-models. were measured and correlated with the polarity of ca. 30 solvent systems. Relevant for any resin-supported methods, a characteristic solvation behavior of each class of polymeric material was detected. Moreover by interpreting the relationship between the large set of solute-solvent interaction data and the most solvent properties known so far, the sum of solvent electron acceptor (AN) and donor (DN) numbers, at a 1:1 proportion was suggested as an alternative and more accurate empirical solvent polarity scale. (C) 2002 Elsevier B.V. All rights reserved.
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    Use of commercial anion-exchange resins as solid support for peptide synthesis and affinity chromatography
    (Elsevier B.V., 2003-07-01) Nakaie, C. R.; Lanzer, D. A.; Malavolta, L.; Cilli, E. M.; Rodrigues, M. M.; Universidade Federal de São Paulo (UNIFESP); Univ Estadual Paulista
    This report demonstrates that due to the presence of residual reactive sites in their matrices, classical diethylaminoethyl-attaching commercial anion-exchanger resins such as DEAE-MacroPrep and DEAE-Sephadex A50 supports can be used for peptide synthesis. Moreover, due to the high stability of the peptide-resin bond in the final cleavage treatments, desired peptidyl-resins free of side-chain protecting groups, which enables them to be further used as solid support for affinity chromatography, can be obtained. To demonstrate this potentiality, a fragment corresponding to the antigenic and immunodominant epitope of sporozoites of the Plasmodium falciparum malaria parasite was synthesized in these traditional resins and antibody molecules generated against the peptide sequence were successfully retained in these peptidyl supports. Due to the maintenance of their original anion-exchange capacities, the present findings open the unique possibility of applying, simultaneously, dual anion-exchange and affinity procedures for purification of a variety of macromolecules. (C) 2003 Elsevier Science (USA). All rights reserved.
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    Use of the same polymer for synthesis and purification of peptides
    (Sociedade Brasileira de Química, 2005-04-01) Silva, Elias Horacio da [UNIFESP]; Etchegaray, Augusto [UNIFESP]; Carvalho, Regina S. H. [UNIFESP]; Jubilut, Guita Nicolaewsky [UNIFESP]; Miranda, Antonio [UNIFESP]; Nakaie, Clovis Ryuichi [UNIFESP]; Universidade Federal de São Paulo (UNIFESP)
    This work reveals an uncommon but valuable biotechnological approach regarding the use of a same polymer (benzhydrylamine-resin, BHAR) for synthesis and anion exchange purification of peptides. Initially, the octapeptide DRVYIHPF-NH2 was synthesized in 1% and 3% cross-linked BHAR, attaching 2.5 mmol g-1 ammonium groups. Due certainly to its less rigid polymeric backbone, higher synthesis yield (about 80%) was achieved with the former resin. Next, the negatively charged peptides DEVYEHPF-NH2 and DEVYEDPF-NH2 (-1 and -3 in neutral pH, respectively), both synthesized in 1% BHAR were submitted to chromatographic separation test in this same type of resin (1% and 3%). Following comparative results of peptide synthesis and swelling data of resin beads obtained by microscopy, an improved separation of both peptides occurred with 1% BHAR batch. These findings demonstrated that BHAR applied so far for peptide synthesis, when containing high amount of positively charged ammonium groups, can be also used alternatively as a solid support for chromatographic purification of this type of biological molecule.