Molecular Weight and Tacticity of Oligoacrylates by Capillary Electrophoresis - Mass Spectrometry

2010 ◽  
Vol 63 (8) ◽  
pp. 1219 ◽  
Author(s):  
Marianne Gaborieau ◽  
Tim J. Causon ◽  
Yohann Guillaneuf ◽  
Emily F. Hilder ◽  
Patrice Castignolles
Keyword(s):  
Capillary Electrophoresis ◽  
Raft Polymerization ◽  
Degree Of Polymerization ◽  
Size Exclusion ◽  
Separation Mechanism ◽  
Ionization Mass ◽  
Polymeric Particles ◽  
Reversible Addition ◽  
Exclusion Chromatography

Oligo(acrylic acid) efficiently stabilizes polymeric particles, especially particles produced by reversible addition–fragmentation chain transfer (RAFT) (as hydrophilic block of an amphiphilic copolymer). Capillary electrophoresis (CE) has a far higher resolution power to separate these oligomers than the commonly used size exclusion chromatography. Coupling CE to electrospray ionization mass spectrometric detection unravels the separation mechanism. CE separates these oligomers, not only according to their degree of polymerization, but also according to their tacticity, in agreement with NMR analysis. Such analysis will provide insight into the role of these oligomers as stabilizers in emulsion polymerization, and into the mechanism of the RAFT polymerization with respect to degree of polymerization and tacticity.

A Novel One-Pot Procedure for the Fast and Efficient Conversion of RAFT Polymers into Hydroxy-Functional Polymers

2009 ◽  
Vol 62 (8) ◽  
pp. 806 ◽  
Author(s):  
Till Gruendling ◽  
Mathias Dietrich ◽  
Christopher Barner-Kowollik
Keyword(s):  
Elevated Temperatures ◽  
Raft Polymerization ◽  
Functional Polymers ◽  
Size Exclusion ◽  
One Pot ◽  
Reversible Addition ◽  
Exclusion Chromatography ◽  
Azo Initiator ◽  
Raft Polymers ◽  
End Group

We report on the successful quantitative transformation of methacrylate and acrylate-type polymers prepared by reversible addition–fragmentation chain transfer (RAFT) polymerization carrying a dithioester-end-group into hydroxy-functional polymers. The simple reaction procedure involves stirring a solution of the dithioester-capped polymer and an azo-initiator in tetrahydrofuran at elevated temperatures (T = 60°C) in the presence of air. This reaction quantitatively yields hydroperoxide functionalities that can be efficiently reduced to hydroxy groups in a one-pot procedure using triphenylphosphine. Size exclusion chromatography–electrospray mass spectrometry was employed to monitor the progress of the reaction. The new backbone-linked hydroxy group provides a versatile anchor for chemical end-group conversions and conjugation reactions with prepared RAFT polymers, which alleviates problems with the rather limited ability of the dithioester-end-group to undergo non-radical transformations.

scholarly journals Synthesis and Study of Thermoresponsive Amphiphilic Copolymers via RAFT Polymerization

Polymers ◽  
2022 ◽  
Vol 14 (2) ◽  
pp. 229
Author(s):  
Marija Kavaliauskaite ◽  
Medeina Steponaviciute ◽  
Justina Kievisaite ◽  
Arturas Katelnikovas ◽  
Vaidas Klimkevicius
Keyword(s):  
Chain Transfer ◽  
Raft Polymerization ◽  
Size Exclusion ◽  
Scattering Method ◽  
Amphiphilic Copolymers ◽  
Dynamic Light Scattering Method ◽  
Reversible Addition ◽  
Exclusion Chromatography ◽  
Kinetics Of ◽  
Glycol Methyl Ether

Synthesis and study of well-defined thermoresponsive amphiphilic copolymers with various compositions were reported. Kinetics of the reversible addition-fragmentation chain transfer (RAFT) (co)polymerization of styrene (St) and oligo(ethylene glycol) methyl ether methacrylate (PEO5MEMA) was studied by size exclusion chromatography (SEC) and 1H NMR spectroscopy, which allows calculating not only (co)polymerization parameters but also gives valuable information on RAFT (co)polymerization kinetics, process control, and chain propagation. Molecular weight Mn and dispersity Đ of the copolymers were determined by SEC with triple detection. The detailed investigation of styrene and PEO5MEMA (co)polymerization showed that both monomers prefer cross-polymerization due to their low reactivity ratios (r1 < 1, r2 < 1); therefore, the distribution of monomeric units across the copolymer chain of p(St-co-PEO5MEMA) with various compositions is almost ideally statistical or azeotropic. The thermoresponsive properties of p(St-co-PEO5MEMA) copolymers in aqueous solutions as a function of different hydrophilic/hydrophobic substituent ratios were evaluated by measuring the changes in hydrodynamic parameters under applied temperature using the dynamic light scattering method (DLS).

scholarly journals Flurbiprofen: A Study of the Behavior of the Scalemate by Chromatography, Sublimation, and NMR

Symmetry ◽  
2021 ◽  
Vol 13 (4) ◽  
pp. 543
Author(s):  
Magdalena Kwiatkowska ◽  
Alicja Wzorek ◽  
Anna Kolbus ◽  
Mariusz Urbaniak ◽  
Jianlin Han ◽  
...  
Keyword(s):  
Relaxation Time ◽  
Preparative Thin Layer Chromatography ◽  
Transverse Relaxation Time ◽  
Size Exclusion ◽  
Test Case ◽  
Ionization Mass ◽  
Chiral Drugs ◽  
Good Test ◽  
Exclusion Chromatography ◽  
Medium Pressure Liquid Chromatography

2-(2-Fluoro-4-biphenyl) propionic acid (flurbiprofen), from the phenylalkanoic acid family of nonsteroidal anti-inflammatory drugs (NSAID’s), is currently on the pharmaceutical market as a racemate. This racemic compound was tested for its propensity to undergo the self-disproportionation of enantiomers (SDE) phenomenon by various forms of chromatography (SDEvC), such as routine gravity-driven column chromatography, medium-pressure liquid chromatography (MPLC), preparative thin-layer chromatography (PTLC), and size-exclusion chromatography (SEC), as well as by sublimation (SDEvS). Furthermore, examination by nuclear magnetic resonance (NMR) in various solvents found that flurbiprofen exhibited the phenomenon of self-induced diastereomeric anisochronism (SIDA). By measurement of the diffusion coefficient (D), the longitudinal relaxation time (T1), and the transverse relaxation time (T2) using NMR, as well as by electrospray ionization-mass spectrometry (ESI-MS) examinations, the preferred intermolecular association was found to be solvent dependent, e.g., heterochiral association was preferred in toluene, while homochiral association was preferred in more polar solvents. This study also attempted, unsuccessfully, to correlate the NMR measurements of flurbiprofen with chromatographic outcomes for the rationalization and prediction of chromatographic results based on NMR measurements. Because the intermolecular hydrogen bonding of the acid groups in flurbiprofen overwhelmingly predominates over other intermolecular interactions, flurbiprofen seemed to represent a good test case for this idea. The behavior of scalemic samples of flurbiprofen is important, as, although it is currently dispensed as a racemate, clinical applications of the R enantiomer have been investigated. SDEvC and SDEvS both have ramifications for the preparation, handling, and storage of enantioenriched flurbiprofen, and this concern applies to other chiral drugs as well.

scholarly journals Antibacterial Peptides Produced by Alcalase from Cowpea Seed Proteins

Antibiotics ◽  
2021 ◽  
Vol 10 (7) ◽  
pp. 870
Author(s):  
Ali Osman ◽  
Gamal Enan ◽  
Abdul-Raouf Al-Mohammadi ◽  
Seham Abdel-Shafi ◽  
Samar Abdel-Hameid ◽  
...  
Keyword(s):  
Size Exclusion Chromatography ◽  
Seed Proteins ◽  
Negative Ions ◽  
Size Exclusion ◽  
Ionization Mass ◽  
Bacterial Cells ◽  
Antibacterial Efficiency ◽  
Exclusion Chromatography ◽  
Molecular Masses ◽  
Cowpea Seed

Cowpea seed protein hydrolysates (CPH) were output from cowpea seeds applying alcalase® from Bacillus licheniformis. CPH with an elevated level of hydrolysis was fractionated by size exclusion chromatography (SEC). Both CPH and SEC-portions showed to contain antimicrobial peptides (AMPs) as they inhibited both Gram-positive bacteria, such as Listeria monocytogenes LMG10470 (L. monocytogenes), Listeria innocua. LMG11387 (L. innocua), Staphylococcus aureus ATCC25923 (S.aureus), and Streptococcus pyogenes ATCC19615 (St.pyogenes), and Gram-negative bacteria, such as Klebsiella pnemoniae ATCC43816 (K. pnemoniae), Pseudomonas aeroginosa ATCC26853 (P. aeroginosa), Escherichia coli ATCC25468) (E.coli) and Salmonella typhimurium ATCC14028 (S. typhimurium).The data exhibited that both CPH and size exclusion chromatography-fraction 1 (SEC-F1) showed high antibacterial efficiency versus almost all the assessed bacteria. The MIC of the AMPs within SEC-F1 and CPHs were (25 µg/mL) against P. aeruginosa, E.coli and St. pyogenes. However, higher MICsof approximately 100–150 µg/mL showed for both CPHs and SEC-F1 against both S. aureus and L. innocua; it was 50 µg/mL of CPH against S.aureus. The Electro-spray-ionization-mass-spectrometry (ESI-MS) of fraction (1) revealed 10 dipeptides with a molecular masses arranged from 184 Da to 364 Da and one Penta peptide with a molecular mass of approximately 659 Da inthe case of positive ions. While the negative ions showed 4 dipeptides with the molecular masses that arranged from 330 Da to 373 Da. Transmission electron microscope (TEM) demonstrated that the SEC-F1 induced changes in the bacterial cells affected. Thus, the results suggested that the hydrolysis of cowpea seed proteins by Alcalase is an uncomplicated appliance to intensify its antibacterial efficiency.

scholarly journals Metagenomic Profiling of Fecal-Derived Bacterial Membrane Vesicles in Crohn’s Disease Patients

Cells ◽  
2021 ◽  
Vol 10 (10) ◽  
pp. 2795
Author(s):  
Nader Kameli ◽  
Heike E. F. Becker ◽  
Tessa Welbers ◽  
Daisy M. A. E. Jonkers ◽  
John Penders ◽  
...  
Keyword(s):  
Crohn’S Disease ◽  
Crohn's Disease ◽  
Membrane Vesicles ◽  
Amplicon Sequencing ◽  
Size Exclusion ◽  
Bacterial Membrane ◽  
Microbial Composition ◽  
Fecal Samples ◽  
Exclusion Chromatography

Background: In the past, many studies suggested a crucial role for dysbiosis of the gut microbiota in the etiology of Crohn’s disease (CD). However, despite being important players in host–bacteria interaction, the role of bacterial membrane vesicles (MV) has been largely overlooked in the pathogenesis of CD. In this study, we addressed the composition of the bacterial and MV composition in fecal samples of CD patients and compared this to the composition in healthy individuals. Methods: Fecal samples from six healthy subjects (HC) in addition to twelve CD patients (six active, six remission) were analyzed in this study. Fecal bacterial membrane vesicles (fMVs) were isolated by a combination of ultrafiltration and size exclusion chromatography. DNA was obtained from the fMV fraction, the pellet of dissolved feces as bacterial DNA (bDNA), or directly from feces as fecal DNA (fDNA). The fMVs were characterized by nanoparticle tracking analysis and cryo-electron microscopy. Amplicon sequencing of 16s rRNA V4 hypervariable gene regions was conducted to assess microbial composition of all fractions. Results: Beta-diversity analysis showed that the microbial community structure of the fMVs was significantly different from the microbial profiles of the fDNA and bDNA. However, no differences were observed in microbial composition between fDNA and bDNA. The microbial richness of fMVs was significantly decreased in CD patients compared to HC, and even lower in active patients. Profiling of fDNA and bDNA demonstrated that Firmicutes was the most dominant phylum in these fractions, while in fMVs Bacteroidetes was dominant. In fMV, several families and genera belonging to Firmicutes and Proteobacteria were significantly altered in CD patients when compared to HC. Conclusion: The microbial alterations of MVs in CD patients particularly in Firmicutes and Proteobacteria suggest a possible role of MVs in host-microbe symbiosis and induction or progression of inflammation in CD pathogenesis. Yet, the exact role for these fMV in the pathogenesis of the disease needs to be elucidated in future studies.

scholarly journals The Two ADF-H Domains of Twinfilin Play Functionally Distinct Roles in Interactions with Actin Monomers

2002 ◽  
Vol 13 (11) ◽  
pp. 3811-3821 ◽  
Author(s):  
Pauli J. Ojala ◽  
Ville O. Paavilainen ◽  
Maria K. Vartiainen ◽  
Roman Tuma ◽  
Alan G. Weeds ◽  
...  
Keyword(s):  
Binding Site ◽  
Binding Activity ◽  
Size Exclusion ◽  
Actin Dynamics ◽  
Actin Binding ◽  
Actin Monomer ◽  
Wild Type ◽  
Native Page ◽  
Exclusion Chromatography

Twinfilin is a ubiquitous and abundant actin monomer–binding protein that is composed of two ADF-H domains. To elucidate the role of twinfilin in actin dynamics, we examined the interactions of mouse twinfilin and its isolated ADF-H domains with G-actin. Wild-type twinfilin binds ADP-G-actin with higher affinity (K D = 0.05 μM) than ATP-G-actin (K D = 0.47 μM) under physiological ionic conditions and forms a relatively stable (k off = 1.8 s−1) complex with ADP-G-actin. Data from native PAGE and size exclusion chromatography coupled with light scattering suggest that twinfilin competes with ADF/cofilin for the high-affinity binding site on actin monomers, although at higher concentrations, twinfilin, cofilin, and actin may also form a ternary complex. By systematic deletion analysis, we show that the actin-binding activity is located entirely in the two ADF-H domains of twinfilin. Individually, these domains compete for the same binding site on actin, but the C-terminal ADF-H domain, which has >10-fold higher affinity for ADP-G-actin, is almost entirely responsible for the ability of twinfilin to increase the amount of monomeric actin in cosedimentation assays. Isolated ADF-H domains associate with ADP-G-actin with rapid second-order kinetics, whereas the association of wild-type twinfilin with G-actin exhibits kinetics consistent with a two-step binding process. These data suggest that the association with an actin monomer induces a first-order conformational change within the twinfilin molecule. On the basis of these results, we propose a kinetic model for the role of twinfilin in actin dynamics and its possible function in cells.

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