Huynhsommer0719

To account for the charge transfer and covalent character in bonding between P and Bi centers, the electronic structures of [P(C6H4-o-CH2SCH3)3BiCln](3-n)+ (n = 0-3) model species have been investigated computationally. MK-0752 On the basis of this survey a synthetic target compound with a dative P→Bi bond has been selected. Consecutively, the highly reactive bismuth cage [P(C6H4-o-CH2SCH3)3Bi]3+ has been accessed experimentally and characterized. Importantly, our experiments (single-crystal X-ray diffraction and solid-state NMR spectroscopy) and computations (NBO and AIM analysis) reveal that the P···Bi bonding in this trication can be described as a dative bond. Here we have shown that our accordion-like molecular framework allows for tuning of the interaction between P and Bi centers.Limited knowledge is currently available on the biochemical basis for the development of dark-cutting beef. The objective of this research was to determine the metabolite profile and mitochondrial content differences between normal-pH and dark-cutting beef. A gas chromatography-mass spectrometer-based nontargeted metabolomic approach indicated downregulation of glycolytic metabolites, including glucose-1- and 6-phosphate and upregulation of tricarboxylic substrates such as malic and fumaric acids occurred in dark-cutting beef when compared to normal-pH beef. Neurotransmitters such as 4-aminobutyric acid and succinate semialdehyde were upregulated in dark-cutting beef than normal-pH beef. Immunohistochemistry indicated a more oxidative fiber type in dark-cutting beef than normal-pH beef. In support, the mitochondrial protein and DNA content were greater in dark-cutting beef. This increased mitochondrial content, in part, could influence oxygen consumption and myoglobin oxygenation/appearance of dark-cutting beef. The current results demonstrate that the more tricarboxylic metabolites and mitochondrial content in dark-cutting beef impact muscle pH and color.Filter-based thermal desorption (F-TD) techniques, such as the filter inlet for gases and aerosols (FIGAERO), are widely employed to investigate the molecular composition and physicochemical properties of secondary organic aerosol (SOA). Here, we introduce an enhanced capability of F-TD through combination of a customized F-TD inlet with chemical ionization mass spectrometry (CIMS) and ultra-performance liquid chromatography/ electrospray ionization mass spectrometry (UPLC/ESI-MS). The utility of F-TD/CIMS + UPLC/ESI-MS is demonstrated by application to α-pinene ozonolysis SOA, for which increased filter aerosol mass loading is shown to slow the evaporation rates of deposited compounds. Evidence for oligomer decomposition producing multi-mode F-TD/CIMS thermograms is provided by measurement of the mass fraction remaining (MFR) of monomeric and dimeric α-pinene oxidation products on the filter via UPLC/ESI-MS. In-situ evaporation of aerosol particles suggests that α-pinene-derived hydroperoxides are thermally labile; thus, analysis of particle-phase (hydro)peroxides via F-TD may not be appropriate. A synthesized pinene-derived dimer ester (C20H32O5) is found to be thermally stable up to 200 °C, whereas particle-phase dimers (C19H30O5) are observed to form during F-TD analysis via thermally induced condensation of synthesized pinene-derived alcohols and diacids. The complementary F-TD/CIMS + UPLC/ESI-MS method offers previously inaccessible insight into the molecular composition and thermal desorption behavior of SOA that both clarifies and expands on analysis via traditional F-TD techniques.In search of new ligand motifs for photoactive iron(II) complexes with long-lived MLCT states, a series of six complexes with tridentate amine-functionalized bis-n-heterocyclic carbene (NHC)-pyridine ligands is presented. In the homoleptic complexes imidazole-, methylimidazole-, or benzimidazole-2-ylidene, NHC donors are employed in combination with pyridine, functionalized in the 4-position by dimethylamine or dibenzylamine. The effects of these different functionalities on the electronic structure of the complexes are examined through detailed ground state characterization by NMR, single crystal X-ray diffraction, as well as electrochemical and spectroscopic methods. The net influence of these different functionalities on orbital-orbital and electrostatic ligand-iron interactions is investigated thoroughly by density functional theory, and changes in the excited state behavior and lifetimes are finally examined by ultrafast optical spectroscopy. Great deviations of the initially expected effects by substitution in 4-position on the photochemical properties are observed, together with a significantly increased π-acceptor interaction strength in the benzimidazole-2-ylidene functionalized complexes.Therapeutic proteins are an indispensable class of drugs and often therapeutics of last resort. They are sensitive to oxidation, which is of critical concern, because it can affect drug safety and efficacy. Protein oxidation, with methionine and tryptophan as the most susceptible moieties, is mainly monitored by HPLC-MS techniques. However, since several oxidation products display the same mass difference, their identification by MS is often ambiguous. Therefore, an alternative analytical method able to unambiguously identify and, ideally, also quantify oxidation species in proteins is highly desired. Here, we present an NMR-based approach to monitor oxidation in full-length proteins under denaturing conditions, as demonstrated on two biotherapeutic monoclonal antibodies (mAbs). We show that methionine sulfoxide, methionine sulfone, N-formylkynurenine, kynurenine, oxindolylalanine, hydroxypyrroloindole, and 5-hydroxytryptophan result in characteristic chemical shift correlations suited for their identification and quantification. We identified the five most abundant oxidation products in forced degradation studies of two full-length therapeutic mAbs and can also unambiguously distinguish oxindolylalanine from 5-hydroxytryptophan, which are undistinguishable by MS due to the same mass shift. Quantification of the abundant methionine sulfoxide by NMR and MS gave highly comparable values. These results underline the suitability of NMR spectroscopy for the identification and quantification of critical quality attributes of biotherapeutics.