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Microstructure characterization and mechanistic insight into polyether polyols and their associated polyurethanes. MASS SPECTROMETRY REVIEWS 2023. [PMID: 37533397 DOI: 10.1002/mas.21862] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Received: 03/23/2023] [Revised: 06/24/2023] [Accepted: 06/28/2023] [Indexed: 08/04/2023]
Abstract
This article reviews the analytical tool chest used for characterizing alkoxylates and their associated copolymer mixtures. Specific emphasis will be placed upon the use of mass spectrometry-based techniques as rapid characterization tools for optimizing reaction processes in an industrial R&D setting. An initial tutorial will cover the use of matrix-assisted laser desorption/ionization-mass spectrometry and tandem mass spectrometry fragmentation for detailed component analysis (e.g., polyol and isocyanate) of a model polyurethane-based foam. Next, this critical feedback information will be used with the guidance of mass spectrometry to initiate the development of a new, more efficient, tris(pentafluorophenyl)borane (FAB) catalyst-based alkoxylation process for generating the next generation of glycerin-initiated poly(propylene oxide)-co-poly(ethylene oxide) copolymers. Examples will be provided for each step in the FAB-based optimization process that were required to generate the final product. Following this example, two-dimensional liquid chromatography, supercritical fluid chromatography, and ion mobility separations, along with their coupling to mass spectrometry, will be reviewed for their efficiency in characterizing and quantitating the components within these complex polyether polyol mixtures.
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A method for the preparation and characterization of single molecular weight urethane oligomers: A preliminary ion mobility and mass spectrometry study. POLYMER 2022. [DOI: 10.1016/j.polymer.2022.125582] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
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3
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Preparation and characterization of discrete mass polyether-based polyurethane oligomers. POLYMER 2022. [DOI: 10.1016/j.polymer.2022.125069] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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Mass spectrometry and ion mobility study of poly(ethylene glycol)-based polyurethane oligomers. RAPID COMMUNICATIONS IN MASS SPECTROMETRY : RCM 2020; 34 Suppl 2:e8662. [PMID: 31731326 DOI: 10.1002/rcm.8662] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/03/2019] [Revised: 11/07/2019] [Accepted: 11/13/2019] [Indexed: 06/10/2023]
Abstract
RATIONALE Commercial-grade polymer synthesis is performed via melt polymerization, which leads to polydispersion. The work reported herein provides a synthetic strategy to produce mono-dispersive polyurethane oligomers and an analytical strategy to distinguish these oligomers, providing chemists with the tools necessary to synthesize and identify specific polymer structures that exhibit a desired property. METHODS Three isomeric poly(ethylene glycol)-polyurethane (PEG-PUR) oligomers were synthesized and analyzed via flow-injection ion mobility mass spectrometry (IM-MS). Each polymer oligomer was injected and run independently via flow injection at 100 μL•min-1 and analyzed in positive ion mode on a drift tube quadrupole time-of-flight (QTOF) instrument. Mobility measurements were determined using a single-field approach. For tandem mass spectrometry (MS/MS) experiments, the sodium-adducted singly charged precursor ion was isolated in the quadrupole and subjected to a range of collision energies. RESULTS In MS experiments, both +1 and +2 sodium-adducted species were observed for each oligomer at m/z 837.4 and 430.2, respectively. When isolated and fragmented via MS/MS, the +1 precursor yielded distinct product ions for each of the three isomeric oligomers. Fragmentation generally occurred at urethane linkages via 1,3- and 1,5-H shift mechanisms. IM was also used to distinguish the three isomers, with greater IM separation observed for the +2 versus the +1 species. CONCLUSIONS Mono-disperse PEG-PUR oligomers were synthesized and analyzed. Although the polymeric oligomers analyzed in this study are quite small and structurally simple, this work serves as a model system for the synthesis and structural characterization of larger, more complex block copolymers.
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Abstract
This review covers the applications of mass spectrometry (MS) and its hyphenated techniques to characterize polyurethane (PU) synthetic polymers and their respective hard and soft segments. PUs are commonly composed of hard segments including methylene bisphenyl diisocyanate (MDI) and toluene diisocyanate (TDI), and soft segments including polyester and polyether polyols. This literature review highlights MS techniques such as electrospray ionization (ESI), matrix assisted laser/desorption ionization (MALDI), ion mobility-mass spectrometry (IM-MS), and computational methods that have been used for the characterization of this polymer system. Here we review specific case studies where MS techniques have elucidated unique features pertaining to the makeup and structural integrity of complex PU materials and PU precursors.
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Abstract
Polyurethane (PU) di-block copolymers are one of the most versatile polymeric materials, comprised of hard and soft segments that contribute to PU's broad range of applications. Polybutylene adipate (PBA) is a commonly used soft segment in PU systems. Characterizing the structure of PBA polymers is essential to understanding complex heterogeneity within a PU sample. In this study, ion mobility-mass spectrometry (IM-MS) and tandem mass spectrometry (MS/MS) are used to structurally characterize a PBA standard (Mn = 2250) adducted with a combination of monovalent alkali cations (Li, Na, K, Rb, and Cs). IM-MS profiles show unique trends associated with each cation-adducted PBA sample. Charge state trends: +1, +2, and +3 were extracted for cation-adducted PBA oligomers, and investigated to study gas-phase transitional folding. To quantitatively assess the gas-phase structural similarities and differences, a statistical test (ANOVA) was used to compare PBA oligomer-cation collisional cross sections (CCS). Fragmentation studies (MS/MS) identified the unique behavior of Li and Na for promoting 1,5 H-shift and 1,3 H-shift fragmentation, whereas the PBA precursor preferentially loses the larger K, Rb, and Cs cations as the ion activation energy is increased. The combination of adducted alkali cations, IM-MS, and MS/MS allow for unique structural characterization of this important PBA system.
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Structural Characterization of Methylenedianiline Regioisomers by Ion Mobility-Mass Spectrometry and Tandem Mass Spectrometry. 4. 3-Ring and 4-Ring Isomers. Anal Chem 2018; 90:14453-14461. [PMID: 30479133 DOI: 10.1021/acs.analchem.8b04103] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Matrix-assisted laser desorption/ionization-mass spectrometry (MALDI-MS) is used to characterize methylenedianiline (MDA) 3-ring and 4-ring species. Building on our previous MALDI-MS 2-ring MDA isomer study, here we compare 3-ring and 4-ring electrospray ionization (ESI) and MALDI results. In ESI, 3-ring and 4-ring MDAs each form a single [M + H]+ parent ion. However, in MALDI, each MDA multimer forms three unique precursor ions: [M + H]+, [M•]+, and [M - H]+. In this study, 3-ring and 4-ring MDA precursors are characterized to identify the unique fragment ions formed and their respective fragmentation pathways. In addition to the three possible precursors, the 3-ring and 4-ring species are higher-order oligomer precursors in polyurethane (PUR) production and thus provide additional insight into the polymeric behavior of these PUR hard block precursors. The combination of ion mobility-mass spectrometry (IM - MS) and tandem mass spectrometry (MS/MS) allow the structural characterization of these larger MDA multimers.
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Structural Characterization of Methylenedianiline Regioisomers by Ion Mobility-Mass Spectrometry, Tandem Mass Spectrometry, and Computational Strategies. 3. MALDI Spectra of 2-Ring Isomers. Anal Chem 2017; 89:9900-9910. [PMID: 28803462 DOI: 10.1021/acs.analchem.7b02133] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Characterization of methylenedianiline (MDA) 2-ring isomers (2,2'-, 2,4'-, and 4,4'-MDA) is reported using matrix assisted laser desorption/ionization-mass spectrometry (MALDI-MS), a common technique used for characterizing synthetic polymers. MDA is a precursor to methylene diphenyl diisocyanate (MDI), a hard block component in polyurethane (PUR) synthesis. This work focuses on comparing MALDI results to those of our previous electrospray ionization-mass spectrometry (ESI-MS) studies. In ESI, 2-ring MDA isomers formed single unique [M + H]+ (199 Da) parent ions, whereas in MALDI each isomer shows significant formation of three precursor ions: [M - H]+ = 197 Da, [M•]+ = 198 Da, and [M + H]+ = 199 Da. Structures and schemes are proposed for the MALDI fragment ions associated with each precursor ion. Ion mobility-mass spectrometry (IM-MS), tandem mass spectrometry (MS/MS), and computational methods were all critical in determining the structures for both precursor and fragment ions as well as the fragmentation mechanisms. The present study indicates that the [M - H]+ and [M•]+ ions are formed by the MALDI process, explaining why they were not observed with ESI.
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Novel behavior of the chromatographic separation of linear and cyclic polymers. Anal Bioanal Chem 2015; 408:677-81. [PMID: 26637218 DOI: 10.1007/s00216-015-9198-9] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2015] [Revised: 11/11/2015] [Accepted: 11/16/2015] [Indexed: 10/22/2022]
Abstract
In various polymerization processes, the formation of a wide variety of chains, not only in length but also in chemical composition, broadly complicates comprehensive polymer characterization. In this communication, we compare different stationary and mobile phases for the analysis of complex polymer mixtures via size-exclusion chromatography-mass spectrometry (SEC-MS). To the best of our knowledge, we report novel chromatographic effects for the separation of linear and cyclic oligomers for polyesters (PE) and polyurethanes (PUR). A complete separation for the different structures was achieved for both polymer types with a single-solvent system (acetonitrile, ACN) and without extensive optimization. Additionally, cyclic species were found to show an inverse elution profile compared to their linear counterparts, suggesting distinct physical properties between species.
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Corrigendum to: “Collision induced dissociation study of ester-based polyurethane fragmentation reactions” Anal. Chim. Acta 808 (2014) 199–219. Anal Chim Acta 2015. [DOI: 10.1016/j.aca.2015.08.039] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
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Structural Characterization of Methylenedianiline Regioisomers by Ion Mobility-Mass Spectrometry, Tandem Mass Spectrometry, and Computational Strategies. 2. Electrospray Spectra of 3-Ring and 4-Ring Isomers. Anal Chem 2015; 87:6288-96. [PMID: 25971782 DOI: 10.1021/acs.analchem.5b01084] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Building on results from our previous study of 2-ring methylenedianiline (MDA), a combined mass spectrometry approach utilizing ion mobility-mass spectrometry (IM-MS) and tandem mass spectrometry (MS/MS) coupled with computational methods enables the structural characterization of purified 3-ring and 4-ring MDA regioisomers in this current study. The preferred site of protonation for the 3-ring and 4-ring MDA was determined to be on the amino groups. Additionally, the location of the protonated amine along the MDA multimer was found to influence the gas phase stability of these molecules. Fragmentation mechanisms similar to the 2-ring MDA species were observed for both the 3-ring and 4-ring MDA. The structural characterization of 3-ring and 4-ring MDA isomers using modern MS techniques may aid polyurethane synthesis by the characterization of industrial grade MDA, multimeric MDA species, and methylene diphenyl diisocyanate (MDI) mixtures.
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Structural characterization of methylenedianiline regioisomers by ion mobility-mass spectrometry, tandem mass spectrometry, and computational strategies: I. Electrospray spectra of 2-ring isomers. Anal Chem 2014; 86:4362-70. [PMID: 24678803 PMCID: PMC4014176 DOI: 10.1021/ac5001652] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
![]()
Purified methylenedianiline (MDA)
regioisomers were structurally
characterized and differentiated using tandem mass spectrometry (MS/MS),
ion mobility-mass spectrometry (IM-MS), and IM-MS/MS in conjunction
with computational methods. It was determined that protonation sites
on the isomers can vary depending on the position of amino groups,
and the resulting protonation sites play a role in the gas-phase stability
of the isomer. We also observed differences in the relative distributions
of protonated conformations depending on experimental conditions and
instrumentation, which is consistent with previous studies on aniline
in the gas phase. This work demonstrates the utility of a multifaceted
approach for the study of isobaric species and elucidates why previous
MDA studies may have been unable to detect and/or differentiate certain
isomers. Such analysis may prove useful in the characterization of
larger MDA multimeric species, industrial MDA mixtures, and methylene
diphenyl diisocyanate (MDI) mixtures used in polyurethane synthesis.
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Collision induced dissociation study of ester-based polyurethane fragmentation reactions. Anal Chim Acta 2014; 808:199-219. [DOI: 10.1016/j.aca.2013.09.035] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2013] [Revised: 09/06/2013] [Accepted: 09/18/2013] [Indexed: 10/26/2022]
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Matrix-assisted laser desorption/ionization-time-of-flight/time-of-flight collision-induced dissociation study of poly(p-phenylenediamine terephthalamide) fragmentation reactions. Anal Chim Acta 2013; 808:124-43. [PMID: 24370099 DOI: 10.1016/j.aca.2013.09.007] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2013] [Revised: 09/02/2013] [Accepted: 09/05/2013] [Indexed: 10/26/2022]
Abstract
MALDI-TOF/TOF collision-induced dissociation (CID) experiments are reported on model poly(p-phenylenediamine terephthalamide) (PPD-T) polymers, revealing a variety of synthesis reaction products. Diamine-terminated oligomers were the major product of synthesis using excess amine, and di-carboxylic acid oligomers were the major product for excess acid. Structures of major reaction products were confirmed by CID fragmentation studies, along with detailed studies of MS/MS decomposition pathways. Apparent fracture of the phenylcarbonyl bond was the major fragmentation pathway (independent of end groups), resulting from initial NHCO bond cleavage with subsequent CO loss. Hydrogen-transfer reactions play an important role in fragmentation, involving both cross-chain abstraction of NH hydrogen and long-range H-transfer. End-group and main-chain modifications produce fingerprint CID fragmentation patterns that can be used to identify end groups and branching patterns; the structure of an unanticipated synthesis product was established using CID. The effect of synthesis conditions on polymer composition was studied using the analysis of variance, specifically, the amine-to-acid ratio used and post-synthesis addition of CaO. Of particular interest is oligomer end-group modification by the solvent (N-methyl pyrrolidone) induced by addition of CaO.
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Abstract
The current study aims to investigate species-related differences in the in-vitro hepatic metabolism of tacroliums using liver microsomes obtained from rat, hamster, guinea pig, rabbit, pig, dog, baboon and humans. Tacrolimus metabolism was characterized using high-performance liquid chromatography- ultraviolet light (HPLC-UV) and two soft ionization mass spectrometric techniques; matrix-assisted lasers desorption/ionization (MALDI) and time-of-flight-secondary ion mass spectrometry (TOF-SIMS). The extent of tacrolimus metabolism, when normalized to the cytochrome P-450 content, was in the order: rat < hamster < rabbit < pig < guinea pig < dog < human < baboon. Tacrolimus metabolism exhibited significant qualitative and quantitative differences between the animal species tested. Desmethyl- (MI-MIII), didesmethyl- (MIV-MVI), monohydroxy- (MVII), dihydroxy- (MVIII), epoxide- (MIX), dihydrodiol- (MX), monodesmethyl and monohydroxy- (MXI-MXIII), and didesmethyl and monohydroxy- (MXIV-MXVI) tacroliums metabolites were identified in the species tested. MI-MX were identified in all the species tested; MXI-MXVI were identified in all species except rat, rabbit and guinea pig; and MXIV-MXVI were identified only in baboon. The current investigation was unable to detect any phase II metabolites due to the limitations of the test system used. The analytical methods were not able to differentiate optical and positional isomers of metabolites due to the nature of the analytical tools used, therefore groups of metabolites were identified based on their molecular weights and available information. From the current in-vitro metabolism studies, the pattern of tacroliums metabolism in baboons closely resembled that in humans and thus it is ideal for studying tacroliums metabolism-related work of clinical relevance.
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Synthesis of Complementary Host- and Guest-Functionalized Polymeric Building Blocks and Their Self-Assembling Behavior. Macromolecules 2009. [DOI: 10.1021/ma901248m] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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Py-GC/MS and MALDI-TOF/TOF CID Study of Poly(phenyl sulfone) Fragmentation Reactions. Macromolecules 2009. [DOI: 10.1021/ma900815g] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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Supramacromolecular self-assembly: Chain extension, star and block polymers via pseudorotaxane formation from well-defined end-functionalized polymers. ACTA ACUST UNITED AC 2009. [DOI: 10.1002/pola.23435] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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Characterization of Branching in Aramid Polymers Studied by MALDI−Ion Mobility/Mass Spectrometry. Macromolecules 2008. [DOI: 10.1021/ma8019464] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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Franz Hillenkamp and Jasna Peter-Katalinic (Eds.): MALDI MS. A practical guide to instrumentation, methods and applications. Anal Bioanal Chem 2008. [DOI: 10.1007/s00216-008-2090-0] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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MALDI-TOF/TOF CID study of 4-alkyl-substituted polystyrene fragmentation reactions. Anal Bioanal Chem 2008; 392:609-26. [DOI: 10.1007/s00216-008-2139-0] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2008] [Revised: 04/07/2008] [Accepted: 04/14/2008] [Indexed: 10/22/2022]
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Synthesis and characterization of a pegylated derivative of 3-(1,2,3,6-tetrahydro-pyridin-4yl)-1H-indole (IDT199): a high affinity SERT ligand for conjugation to quantum dots. Bioorg Med Chem Lett 2007; 17:5656-60. [PMID: 17766114 DOI: 10.1016/j.bmcl.2007.07.061] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2007] [Revised: 07/18/2007] [Accepted: 07/19/2007] [Indexed: 11/16/2022]
Abstract
Quantum dots consisting of a cadmium selenide core encapsulated in a shell of cadmium doped zinc sulfide have the potential to revolutionize fluorescent imaging of live cell cultures. In order to utilize these fluorescent probes it is necessary to functionalize them with biologically active ligands. In this paper we report the design and synthesis of a ligand that has a high affinity for the serotonin transporter (SERT) that may be conjugated to quantum dots.
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Abstract
Electrospray ionization time-of-flight mass spectrometry (ESI-TOF MS) and gel permeation chromatography (GPC) were used to study the synthesis of a series of tiopronin monolayer-protected gold nanoclusters (MPCs) and to monitor their postsynthesis peptide ligand place-exchange reactions. All mass spectra identified the presence of cyclic gold(I)-thiolates with a strong preference for tetrameric species. During the synthesis of pre-monolayer-protected nanoclusters (pre-MPCs), esterified gold(I)-thiolate tetramers were initially observed in minor abundance (with respect to disulfide bridged tiopronin species) before dramatically increasing in abundance and precipitating from solution. After conversion of pre-MPCs to MPCs, ESI-TOF mass spectra demonstrated an overall predominance of tetrameric species with conversion from ester-terminated end groups to carboxyl-terminated end groups. Further modifications were performed through postsynthesis ligand place-exchange reactions to validate the existence of the tetramers. This work suggests that monolayer protection is accomplished by cyclized gold(I)-thiolate tetramers on the gold core surface, and/or that gold(I)-thiolates are a basic building block within the nanoparticles.
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Thin Layer Chromatography-Laser Mass Spectrometry (TLC-LMS) of Triphenylmethane Dyes: Initial Results. ANAL LETT 2006. [DOI: 10.1080/00032718508066150] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
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Universal polyethylene glycol linkers for attaching receptor ligands to quantum dots. Bioorg Med Chem Lett 2006; 16:6262-6. [PMID: 17000112 DOI: 10.1016/j.bmcl.2006.09.031] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2006] [Revised: 09/02/2006] [Accepted: 09/07/2006] [Indexed: 11/27/2022]
Abstract
Biologically active small molecule derivatives that can be conjugated to quantum dots have the promise of revolutionizing fluorescent imaging in biology. In order to achieve this several technical hurdles have to be surmounted, one of which is non-specific adsorption of quantum dots to cell membranes. Pegylating quantum dots has been shown to eliminate non-specific binding. Consequently it is necessary to develop a universal synthetic methodology to attach small molecule ligands to polyethylene glycol. These pegylated small molecules may then be conjugated to the surfaces of quantum dots. Ideally this universal strategy should be adaptable and be applicable to PEG chains of varying lengths. This paper describes the development of one such methodology and the synthesis of a pegylated derivative of the known 5HT(2) agonist 1-(2-aminopropyl)-2,5-dimethoxy benzene. This compound was tested and found to be an agonist for the 5HT(2A) and 5HT(2C) receptor having EC(50) values of 250 and 50 nM, respectively.
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Synthesis and Mass Spectral Characterization of Poly(amic methyl ester) Oligomers. Macromolecules 2006. [DOI: 10.1021/ma0521295] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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Syntheses and Model Complexation Studies of Well-Defined Crown Terminated Polymers. Macromolecules 2005. [DOI: 10.1021/ma047811y] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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Polyamide Pseudorotaxanes, Rotaxanes, and Catenanes Based on Bis(5-carboxy-1,3-phenylene)-(3x+2)-crown-x Ethers. Macromolecules 2004. [DOI: 10.1021/ma049218m] [Citation(s) in RCA: 64] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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45
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Preparation of Pt-Re/Vulcan carbon nanocomposites using a single-source molecular precursor and relative performance as a direct methanol fuel cell electrooxidation catalyst. JOURNAL OF NANOSCIENCE AND NANOTECHNOLOGY 2004; 4:809-816. [PMID: 15570964 DOI: 10.1166/jnn.2004.085] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
Pt-Re/Vulcan carbon powder nanocomposites have been prepared with total metal loadings of 18 wt.% and 40 wt.% using a new non-cluster (1:1)-PtRe bimetallic precursor as the source of metal. Pt-Re nanoparticles having an average diameter of ca. 6 nm and atomic stoichiometry near 1:1 are formed. TEM, on-particle HR-EDS, and powder XRD data are consistent with the formation of Pt-Re alloy nanoparticles having a hexagonal unit cell with cell constants of a = 2.77 A and c = 4.47 A. A nanocomposite prepared at higher total metal loading under more rigorous thermal treatment also contains Pt-Re alloy nanoparticles having a fcc unit cell structure (a = 3.95 A). The precise dependence of Pt-Re nanocrystal structure on the thermal history of the nanocomposite specimen has not been investigated in detail. While these Pt-Re/carbon nanocomposites are active as anode catalysts in operating direct methanol fuel cells, the measured performance is less than that of commercial Pt-Ru/carbon catalysts and has marginal practical importance.
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Characterization of Polyimides by Combining Mass Spectrometry and Selective Chemical Reaction. Macromolecules 2004. [DOI: 10.1021/ma030555p] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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47
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Quantitative Characterization of a Polystyrene/Poly(α-methylstyrene) Blend by MALDI Mass Spectrometry and Size-Exclusion Chromatography. Anal Chem 2003; 75:3744-50. [PMID: 14572039 DOI: 10.1021/ac020593r] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The use of coupled size-exclusion chromatography and MALDI mass spectrometry for quantitative measurement of the composition of technical polymer blends at the molecular level is described. The method is illustrated with a model binary blend consisting of polystyrene and poly(alpha-methylstyrene), both polymers having similar molecular weights and polydispersities. The proposed MALDI data treatment allows determination of the chemical composition of the blend, the molecular weights of the constituents, and the distributions of the homopolymers.
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Matrix-assisted laser desorption/ionization mass spectrometry of discrete mass poly(butylene glutarate) oligomers. Anal Chem 2003; 75:3092-100. [PMID: 12964756 DOI: 10.1021/ac030061q] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The mass dependency of matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS) response has been studied using equimolar mixtures of synthetic discrete mass poly(butylene glutarate) (PBG) oligomers of known structure having degrees of polymerization of 8, 16, 32, and 64. Mass discrimination observed was attributed to choice of matrix and detector saturation caused by higher laser intensity and inclusion of matrix ions in the MALDI spectra. Optimization of sample preparation and instrumental parameters provided uniform response over the mass ranged spanned by these four oligomers. The oligomer mixture was shown to serve as a model of more complex polymer distributions in the mass range 780-6000 Da, and application of the discrete mass oligomers as internal and calibration standards was demonstrated. Inclusion of PBG discrete mass oligomers as an internal standard in a quasi-equimolar mixture with polydispersed poly(butylene adipate) (PBA) indicated that some diminution of response occurred during the analysis of this mixture of materials. Reasons for differences in the corrected molecular weight averages of the polydispersed PBA obtained from measurements using MALDI and GPC were studied using individual discrete mass oligomers as calibration standards for GPC. The data indicated that differences in hydrodynamic volumes of PBG oligomers and PEG standards at similar masses resulted in an overestimation by GPC of the molecular weight averages of the PBA distribution.
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