Research and Development

@article{Dimzon2016b,

title = {Characterization of 3-Aminopropyl Oligosilsesquioxane},

author = {Ian Ken D. Dimzon and Tobias Frömel and Thomas P. Knepper},

url = {https://pubs.acs.org/doi/abs/10.1021/acs.analchem.6b00732},

doi = {10.1021/acs.analchem.6b00732},

year  = {2016},

date = {2016-05-03},

journal = {Analytical Chemistry},

volume = {88},

number = {9},

pages = {4894-4902},

abstract = {The synthesis routes in the production of polysilsesquioxanes have largely relied upon in situ formations. This perspective often leads to polymers in which their basic structures including molecular weight and functionality are unknown [Lichtenhan, J. D.; et al. Silsesquioxane-siloxane copolymers from polyhedral silsesquioxanes Macromolecules, 1993, 26, 2141−2142, http://dx.doi.org/10.1021/ma0060a053]. For a better understanding of the polysilsesquioxane properties and applications, there is a need to develop more techniques to enable their chemical characterization. An innovative method was developed to determine the molecular weight distribution (MWD) of an oligosilsesquioxane synthesized in-house from (3-aminopropyl)triethoxysilane. This method, which can be applied to other silsesquioxanes, siloxanes, and similar oligomers and polymers, involved separation using high performance liquid chromatography (HPLC) and detection using mass spectrometry (MS) with electrospray ionization (ESI). The novelty of the method lies on the unique determination of the absolute concentrations of the individual homologues present in the sample formulation. The use of absolute concentrations is necessary in estimating the MWD of the formulation when relative percentage, which is based solely on mass spectral ion intensities, becomes irrelevant due to the disproportionate response factors of the homologues. Determination of absolute concentration requires the use of single-homologue calibration standards. Because of commercial unavailability, these standards were prepared by efficient fractionation of the original formulation.},

keywords = {condensation, ionization, ions, mass spectrometry, silsesquioxanes},

pubstate = {published},

tppubtype = {article}

}

@article{Wang2015,

title = {Pyridoxamine is a substrate of the energy-coupling factor transporter HmpT},

author = {Tingliang Wang and Armando J. de Jesus and Yigong Shi and Hang Yin},

url = {https://www.nature.com/articles/celldisc201514},

doi = {10.1038/celldisc.2015.14},

year  = {2015},

date = {2015-07-14},

journal = {Cell Discovery},

volume = {1},

pages = {15014},

abstract = {Energy-coupling factor (ECF) transporters belong to a novel family of proteins that forms a subset within the ATP-binding cassette (ABC) transporter family. These proteins are responsible for the uptake of micronutrients in bacteria. ECF transporters are composed of four proteins: the A- and A′-components, the T-component and the S-component. One of the ECF transporters, named HmpT, was crystallized in the apo form with all four components. It is currently unknown whether HmpT serves as a transporter for hydroxymethyl pyrimidine or the different forms of vitamin B6 (pyridoxine, pyridoxal or pyridoxamine). Using a combination of molecular dynamics (MD) simulations and mass spectrometry, we have identified pyridoxamine to be the preferred substrate of HmpT. Mass spectra show that the mass of the substrate from the HmpT–substrate complex matches that of pyridoxamine. MD simulations likewise indicate that pyridoxamine interacts most strongly with most of the conserved residues of the S-component (Glu 41, His 84 and Gln 43) compared with the other vitamin B6 forms. Furthermore, the simulations have implied that loops 1 and 5 of the S-component can participate in the gating action for HmpT.},

keywords = {ECF transporters, gating mechanism, HmpT, mass spectrometry, molecular dynamics, S-component},

pubstate = {published},

tppubtype = {article}

}