Papers by Chrys Wesdemiotis
Journal of the American Chemical Society, Nov 8, 2017
Synthesis of giant unimolecular dendrimers is challenging due, in part, to difficulties encounter... more Synthesis of giant unimolecular dendrimers is challenging due, in part, to difficulties encountered at higher generations, in both convergent and divergent protocols because of the multistep construction/purification process. Herein, we report a hybrid synthetic procedure in which the core is constructed last. This quantitative assembly generated a metallodendrimer that is supercharged (120+), large (11.3 nm diameter), and its core was previously established. The series of complexes has been unequivocally characterized by NMR, ESI-IM-MS, and TEM techniques.
Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy, 2001
Chromatographia, May 12, 2016
or cyclic), and MS analysis using electrospray ionization (ESI) unveiled the hydrophilic block si... more or cyclic), and MS analysis using electrospray ionization (ESI) unveiled the hydrophilic block sizes and the overall copolymer composition. LC-IM-MS effects separation by polarity in the LC step and by shape in the IM step prior to mass-sensitive detection. Such 3-dimensional approach is particularly suitable for the molecular characterization of complex amphiphilic copolymer blends and for the differentiation of similar samples from different sources or different batches.
ACS Macro Letters, 2018
The surface of a blend of 6 kDa polystyrene and 6 kDa polystyrene functionalized with hydroxymeth... more The surface of a blend of 6 kDa polystyrene and 6 kDa polystyrene functionalized with hydroxymethyl ends not only is depleted of the higher energy end groups but also is depleted of any segments belonging to the functionalized chains. This is demonstrated using the emerging technique of surface layer matrix-assisted laser desorption ionization time-of-flight mass spectrometry (SL-MALDI-ToF-MS), which detects entire chains that have any repeat unit at the outer surface, and requires no labeling. Detecting entire chains provides information about the relationship of chain functionalization to surface segregation behavior of entire chains. That the surface is depleted of interior segments of functionalized chains as well as of the ends is remarkable, since the functionality at the single chain end involves less than 0.5 wt % of the functionalized polymer chain.
International Journal of Mass Spectrometry, 2018
Mass spectrometry (MS) is an essential analytical tool for the characterization of the structure ... more Mass spectrometry (MS) is an essential analytical tool for the characterization of the structure of biological macromolecules, including protein-protein and protein-ligand complexes. One-dimensional MS separates gas-phase analyte ions based on their mass to charge ratio (m/z); however, to obtain more detailed structural information, tandem MS (MS/MS), which involves isolation and subsequent fragmentation of a precursor ion, is required. In this thesis, electrospray ionization multistage tandem mass spectrometry (ESI-MS n) was employed to examine the non-covalent complexes between poly(styrene sulfonate) (PSS) and poly-L-lysine (PLL). During single-stage ion activation, the PLL peptide chain mainly underwent backbone cleavages without disruption of the noncovalent interaction which could only be broken via sequential application of electron transfer dissociation (ETD) and collisionally activated dissociation (CAD), indicating strong binding interactions between the two polyelectrolyte chains. Such binding properties make PSS a potential "non-covalent (supramolecular) label" for determining the surface accessibility of basic residues on a peptide or protein. To probe this premise, noncovalent complexes of substance P and PSS were characterized by ESI-MS n using different ion activation methods. Both MS 2 and MS 3 experiments on the substance P + PSS complex resulted in the formation of bn (on CAD) or cn (on ETD) fragments attached non-covalently to the intact PSS chain. All peptide fragments containing the intact PSS chain included Arg1, Lys3, and Gln5, pointing out that these residues, which are located near the Nterminus, are most likely involved in the noncovalent interaction with PSS. In contrast, iv Gln6 was excluded from this fragment series, attesting a much weaker interaction with PSS due to lesser accessibility. The strong tendency of PSS to bind peptides noncovalently at sites that can be elucidated by MS n demonstrates a proof-of-concept for the capacity of this approach to unveil higher order structure in proteins. v ACKNOWLEDGEMENTS I would like to first express my deepest gratitude to my advisor, Dr. Chrys Wesdemiotis for his excellent guidance, valuable suggestions and kindness during the process of my M.S. studies at the University of Akron. His knowledge in chemistry and mass spectrometry directed me towards the right path to achieve my goals during these two years. I would also like to thank him for his help and suggestions regarding my future studies. I would like to thank my committee member Dr. Toshikazu Miyoshi for taking his time to read my thesis and giving me great advice and feedback. He is such a nice person that I do not hesitate to ask for help whenever I have difficulties. I am also grateful for the Department of Polymer Science at The University of Akron. Thanks for holding such an excellent program to support me to do research in such a great environment. The faculty and staff here are all so kind to make me feel at home.
International Journal of Mass Spectrometry, 2017
Electrospray ionization multistage mass spectrometry (ESI-MS n) was employed for the structural c... more Electrospray ionization multistage mass spectrometry (ESI-MS n) was employed for the structural characterization of poly(N-isopropylacrylamide) (pNIPAM) compounds, a widely used class of thermoresponsive materials. Experiments were performed on singly and doubly sodiated pNIPAMs terminated with thiopropionic acid or thiopropyl triethoxysilane substituents, using collisionally activated dissociation (CAD) and electron transfer dissociation (ETD) techniques. Single stages of CAD or ETD only caused small neutral losses diagnostic of the side chains and end groups. A more thorough structural characterization of the pNIPAMs was possible by applying a sequential stage of CAD on fragments generated by ETD, as no surviving chargereduced precursor was present in the ETD spectra. The ETD fragments were selected such that they preserved differentiation of the two chain ends and contained features that led to random backbone cleavages. ETD fragments with an unpaired electron or with a particularly stable charge site fulfilled this requirement, giving rise to backbone fragments that made it possible to characterize the chain connectivity in addition to the end group and side chain structures. Whether a radical ion or an ion with a well stabilized charge site is used to obtain structurally diagnostic fragments by ETD-CAD depends on the end groups, the functional group being reduced in the ETD step and the structure of the ETD fragment chosen for consecutive CAD.
Analytica chimica acta, Jan 3, 2018
Conjugation of poly(ethylene glycol) (PEG) to protein drugs (PEGylation) is increasingly utilized... more Conjugation of poly(ethylene glycol) (PEG) to protein drugs (PEGylation) is increasingly utilized in the biotherapeutics field because it improves significantly the drugs' circulatory half-life, solubility, and shelf-life. The activity of a PEGylated drug depends on the number, size, and location of the attached PEG chain(s). This study introduces a 2D separation approach, including reversed-phase ultra-performance liquid chromatography (RP-UPLC) and ion mobility mass spectrometry (IM-MS), in order to determine the structural properties of the conjugates, as demonstrated for a PEGylated insulin sample that was prepared by random amine PEGylation. The UPLC dimension allowed separation based on polarity. Electrospray ionization (ESI) of the eluates followed by in-source dissociation (ISD) truncated the PEG chains and created insulin fragments that provided site-specific information based on whether they contained a marker at the potential conjugation sites. Separation of the latte...
Journal of Inorganic and Organometallic Polymers and Materials, 2016
A novel, tetrakisterpyridinyl-substituted porphyrin underwent self-assembly to form a three-dimen... more A novel, tetrakisterpyridinyl-substituted porphyrin underwent self-assembly to form a three-dimensional, belt-shaped metallomacrocycle, which was characterized by 1D and 2D NMR and electrospray ionization traveling wave ion mobility mass spectrometry.
Analytical Chemistry, 2004
... Jagtap and Ambre published an overview of the literature regarding the application of MALDI M... more ... Jagtap and Ambre published an overview of the literature regarding the application of MALDI MS to polymer characterization (2). In another review of MALDI MS as applied to polymers, Montaudo et al. ... Chem. 2004, 76, 3417−3428. Jagtap, RN; Ambre, AH Bull. Mater. Sci. ...
The Analyst
LC-MS/MS enables the separation and relative quantitation of cyclic and tadpole architectures of ... more LC-MS/MS enables the separation and relative quantitation of cyclic and tadpole architectures of poly(glycidyl phenyl ether)s synthesized via ring-opening zwitterionic polymerization (ZREP).
European Journal of Mass Spectrometry, 2015
Electron transfer dissociation (ETD) studies have been performed on a peptide and a synthetic pol... more Electron transfer dissociation (ETD) studies have been performed on a peptide and a synthetic polysaccharide doubly charged by different cationization agents. The ETD of protonated-sodiated bombesin gave rise to contiguous series of abundant c-and z-type ions that identified the complete sequence. ETD of the doubly protonated peptide produced a different fragment distribution, which also allowed for complete sequence coverage, but the relative intensities of some sequence ions were very small. Collisionally activated dissociation (CAD) of either precursor rendered limited sequence information. ETD of the sodiated-ammoniated pentamer of a starch-derived linear polysaccharide caused extensive fragmentation through cross-ring cleavages that revealed the possible position of a hydroxyethyl substituent on the saccharide ring. In contrast, ETD of the di-sodiated pentasaccharide did not produce a structure-revealing fragmentation pattern. On the other hand, CAD resulted in efficient glycosidic bond cleavages, either directly (from the sodiated-ammoniated precursor) or via multi-stage fragmentation (from the di-sodiated precursor), which indicated that hydroxyethylation occurs randomly at any saccharide repeat unit along the chain. Overall, the use of different cationizing agents complements the information available by using identical charge sites and opens or enhances ETD pathways that unveil valuable sequence or positional information.
Journal of The American Society for Mass Spectrometry, 2012
Accounts of Chemical Research, 1994
Analytica chimica acta, Aug 17, 2016
This review covers the application of mass spectrometry (MS) and its hyphenated techniques to syn... more This review covers the application of mass spectrometry (MS) and its hyphenated techniques to synthetic polymers of varying architectural complexities. The synthetic polymers are discussed as according to their architectural complexity from linear homopolymers and copolymers to stars, dendrimers, cyclic copolymers and other polymers. MS and tandem MS (MS/MS) has been extensively used for the analysis of synthetic polymers. However, the increase in structural or architectural complexity can result in analytical challenges that MS or MS/MS cannot overcome alone. Hyphenation to MS with different chromatographic techniques (2D × LC, SEC, HPLC etc.), utilization of other ionization methods (APCI, DESI etc.) and various mass analyzers (FT-ICR, quadrupole, time-of-flight, ion trap etc.) are applied to overcome these challenges and achieve more detailed structural characterizations of complex polymeric systems. In addition, computational methods (software: MassChrom2D, COCONUT, 2D maps etc....
Journal of the American Chemical Society, 2014
A terpyridine-based, concentration-dependent, facile self-assembly process is reported, resulting... more A terpyridine-based, concentration-dependent, facile self-assembly process is reported, resulting in two three-dimensional metallosupramolecular architectures, a bis-rhombus and a tetrahedron, which are formed using a two-dimensional, planar, tris-terpyridine ligand. The interconversion between these two structures is concentration-dependent: at a concentration higher than 12 mg mL(-1), only a bis-rhombus, composed of eight ligands and 12 Cd(2+) ions, is formed; whereas a self-assembled tetrahedron, composed of four ligands and six Cd(2+) ions, appears upon sufficient dilution of the tris-terpyridine-metal solution. At concentrations less than 0.5 mg mL(-1), only the tetrahedron possessing an S4 symmetry axis is detected; upon attempted isolation, it quantitatively reverts to the bis-rhombus. This observation opens an unexpected door to unusual chemical pathways under high dilution conditions.
Macromolecules, 2006
... M. Russell, ‡ ‖ Yongsin Kim, ‡ Charles M. Kausch, ‡ Thomas H. Connors, ‡ Robert E. Medsker, ‡... more ... M. Russell, ‡ ‖ Yongsin Kim, ‡ Charles M. Kausch, ‡ Thomas H. Connors, ‡ Robert E. Medsker, ‡ # and Richard R. Thomas* ‡. Department of Chemistry, The University of Akron, Akron, Ohio 44325, and OMNOVA Solutions Inc., 2990 Gilchrist Road, Akron, Ohio 44305-4418. ...
Angewandte Chemie, 2014
A novel terpyridine-based architecture that mimics a first-generation Sierpiński triangle has bee... more A novel terpyridine-based architecture that mimics a first-generation Sierpiński triangle has been synthesized by multicomponent assembly and features tpy-Cd(II)-tpy connectivity (tpy=terpyridine). The key terpyridine ligands were synthesized by the Suzuki cross-coupling reaction. Mixing two different terpyridine-based ligands and Cd(II) in a precise stoichiometric ratio (1:1:3) produced the desired fractal architecture in near-quantitative yield. Characterization was accomplished by NMR spectroscopy, mass spectrometry, and transmission electron microscopy.
Polymer Chemistry, 2014
This supporting information contains a) the 1 H NMR and ESI spectra of synthesized compounds (Br-... more This supporting information contains a) the 1 H NMR and ESI spectra of synthesized compounds (Br-NMe 3 , Br-NBu 3 , RAFT-NMe 3 , RAFT-NBu 3); b) the pseudo-first order kinetic curve of bulk styrene polymerization with RAFT-NMe 3 and RAFT-NBu 3 ; c) the kinetic data of bulk styrene polymerization with RAFT-NEt 3 at 65 °C; d) the 1 H NMR data of PBA and PDMAEA.
Analytical and Bioanalytical Chemistry, 2008
The unimolecular degradation of alkali-metal cationized polyacrylates with the repeat unit CH(2)C... more The unimolecular degradation of alkali-metal cationized polyacrylates with the repeat unit CH(2)CH(COOR) and a variety of ester pendants has been examined by tandem mass spectrometry. The fragmentation patterns resulting from collisionally activated dissociation depend sensitively on the size of the ester alkyl substituent (R). With small alkyl groups, as in poly(methyl acrylate), lithiated or sodiated oligomers (M) decompose via free-radical chemistry, initiated by random homolytic C-C bond cleavages along the polymer chain. The radical ions formed this way dissociate further by backbiting rearrangements and beta scissions to yield a distribution of terminal fragments with one of the original end groups and internal fragments with 2-3 repeat units. If the ester alkyl group bears three or more carbon atoms, cleavages within the ester moieties become the predominant decomposition channel. This distinct reactivity is observed if R = t-butyl, n-butyl, or the mesogenic group (CH(2))(11)-O-C(6)H(4)-C(6)H(4)-CN. The [M+alkali metal](+) ions of the latter polyacrylates dissociate largely by charge-remote 1,5-H rearrangements that convert COOR to COOH groups by expulsion of 1-alkenes. The acid groups may displace an alcohol unit from a neighboring ester pendant to form a cyclic anhydride, unless hindered by steric effects. Using atom transfer radical polymerization, hyperbranched polyacrylates were prepared carrying ester groups both within and between the branches. Unique alkenes and alcohols are cleaved from ester groups at the branching points, enabling determination of the branching architecture.
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Papers by Chrys Wesdemiotis