Yoon-Joo Ko

Hollow and microporous catalysts bearing Cr(III)–F porphyrins for room temperature CO2 fixation to cyclic carbonates

Hollow and microporous metal free/Cr-porphyrin networks were prepared via the Sonogashira coupling of metal-free or Cr-tetra(4-ethynylphenyl) porphyrins and 1,4-diiodobenzene on the surface of silica templates followed by silica etching. Zinc was introduced into a hollow and microporous metal free porphyrin network (H–MPN) through post-synthetic modification to form a H–MZnPN. Hollow and microporous Cr(III)–F porphyrin networks (H–MCrPNs) showed the best catalytic activities in room temperature CO2 fixation with epoxides to cyclic carbonates. In addition, the H–MCrPN could be reused at least for five runs, maintaining the original catalytic activity. The good performance of the H–MCrPN is attributed to its microporosity, the shortened diffusion pathways for substrates due to the hollow structure, and the efficient Lewis acidic activity of Cr(III)–F moieties.

Hollow structural effect of microporous organocatalytic polymers with pyrrolidines: dramatic enhancement of catalytic performance

Hollow and microporous organic polymers bearing pyrrolidines (H-MOP-P) were prepared by template synthesis and post-synthetic modification. H-MOP-P showed enhanced organocatalytic performance, compared to nonhollow microporous catalysts.

Carbon Isotopomer Analysis with Non-Unifom Sampling HSQC NMR for Cell Extract and Live Cell Metabolomics Studies

Isotopomer analysis using either 13C NMR or LC/GC-MS has been an invaluable tool for studying metabolic activities in a variety of systems. Traditional challenges are, however, that 13C-detected NMR is insensitive despite its high resolution, and that MS-based techniques cannot easily differentiate positional isotopomers. In addition, current 13C NMR or LC/GC-MS has limitations in detecting metabolites in living cells. Here, we describe a non-uniform sampling-based 2D heteronuclear single quantum coherence (NUS HSQC) approach to measure metabolic isotopomers in both cell lysates and living cells. The method provides a high resolution that can resolve multiplet structures in the 13C dimension while retaining the sensitivity of the 1H-indirect detection. The approach was tested in L1210 mouse leukemia cells labeled with 13C acetate by measuring NUS HSQC with 25% sampling density. The results gave a variety of metabolic information such as (1) higher usage of acetate in acetylation pathway than aspartate synthesis, (2) TCA cycle efficiency changes upon the inhibition of mitochondrial oxidative phosphorylation by pharmacological agents, and (3) position-dependent isotopomer patterns in fatty acids in living cells. In addition, we were able to detect fatty acids along with other hydrophilic molecules in one sample of live cells without extraction. Overall, the high sensitivity and resolution along with the application to live cells should make the NUS HSQC approach attractive in studying carbon flux information in metabolic studies.

Facile synthesis of 2-O-iodoacetyl protected glycosyl iodides: useful precursors of 1-->2-linked 1,2-trans-glycosides.

The preparation and utilization of novel iodide glycosyl donors, 2-O-iodoacetyl-glycopyranosyl iodides, is described. The mechanism for the reaction of iodine with carbohydrate cyclic ketene acetal was investigated through low-temperature NMR experiments. 2-O-Iodoacetyl-glycopyranosyl iodides can serve as effective glycosyl donors giving 2-O-iodoacetyl 1,2-trans-glycosides in high yields and excellent stereoselectivities. The 2-O-iodoacetyl group was removed selectively with thiourea to afford 2-hydroxy 1,2-trans-glycosides in high yield without affecting other protecting groups and anomeric configurations.

Adhesive organic network films with a holey microstructure: useful platforms for the engineering of flexible energy devices

Pure silica zeolite (Silicalite-1) bricks with a 2D morphology were assembled on a slide glass and used as templates for the preparation of microstructured organic network films (MONFs) with a hollow space and holes by the Sonogashira coupling of tetrakis(4-ethynylphenyl)methane and 1,4-diiodobenzene and silica etching. The MONFs were adhesive to polyethylene terephthalate (PET) films due to their unique structural effects. Cu was loaded on the MONF/PET by electroless deposition. The Cu/MONF/PET showed excellent retention of conductivities in repeated severe bending.

Observation of acetyl phosphate formation in mammalian mitochondria using real-time in-organelle NMR metabolomics

Significance We introduce an in-organelle live NMR metabolomics approach that allows for real-time metabolic monitoring of live human mitochondria. The approach also features more than an order of magnitude higher sensitivity and much less overlap than conventional methods. The real-time monitoring capability identified acetyl phosphate in human mitochondria and showed its biphasic kinetic profile typical of a reaction intermediate. The method also allowed for estimation of pyruvate dehydrogenase enzyme activity in live mitochondria according to p53 status, independent of competing cytosolic metabolism. Our approach should be very useful in studies on mitochondrial-specific contributions to cancer metabolism, and can be straightforwardly extended to studies on other diseases with altered mitochondrial metabolism. Recent studies point out the link between altered mitochondrial metabolism and cancer, and detailed understanding of mitochondrial metabolism requires real-time detection of its metabolites. Employing heteronuclear 2D NMR spectroscopy and 13C3-pyruvate, we propose in-organelle metabolomics that allows for the monitoring of mitochondrial metabolic changes in real time. The approach identified acetyl phosphate from human mitochondria, whose production has been largely neglected in eukaryotic metabolism since its first description about 70 years ago in bacteria. The kinetic profile of acetyl phosphate formation was biphasic, and its transient nature suggested its role as a metabolic intermediate. The method also allowed for the estimation of pyruvate dehydrogenase (PDH) enzyme activity through monitoring of the acetyl-CoA formation, independent of competing cytosolic metabolism. The results confirmed the positive regulation of mitochondrial PDH activity by p53, a well-known tumor suppressor. Our approach can easily be applied to other organelle-specific metabolic studies.

Biotransformation of polyunsaturated fatty acids to bioactive hepoxilins and trioxilins by microbial enzymes

Hepoxilins (HXs) and trioxilins (TrXs) are involved in physiological processes such as inflammation, insulin secretion and pain perception in human. They are metabolites of polyunsaturated fatty acids (PUFAs), including arachidonic acid, eicosapentaenoic acid and docosahexaenoic acid, formed by 12-lipoxygenase (LOX) and epoxide hydrolase (EH) expressed by mammalian cells. Here, we identify ten types of HXs and TrXs, produced by the prokaryote Myxococcus xanthus, of which six types are new, namely, HXB5, HXD3, HXE3, TrXB5, TrXD3 and TrXE3. We succeed in the biotransformation of PUFAs into eight types of HXs (>35% conversion) and TrXs (>10% conversion) by expressing M. xanthus 12-LOX or 11-LOX with or without EH in Escherichia coli. We determine 11-hydroxy-eicosatetraenoic acid, HXB3, HXB4, HXD3, TrXB3 and TrXD3 as potential peroxisome proliferator-activated receptor-γ partial agonists. These findings may facilitate physiological studies and drug development based on lipid mediators.Hepoxilins (HXs) and trioxilins (TrXs) are lipid metabolites with roles in inflammation and insulin secretion. Here, the authors discover a prokaryotic source of HXs and TrXs, identify the biosynthetic enzymes and heterologously express HXs and TrXs in E. coli.

Microporous Porphyrin Networks Mimicking a Velvet Worm Surface and Their Enhanced Sensitivities toward Hydrogen Chloride and Ammonia

This work shows that the functions of microporous organic network materials can be enhanced through engineering of the material structure. Mimicking the surface structure of velvet worms, we prepared the aligned 1D structure (rod) of microporous porphyrin networks by the Sonogashira coupling of tetrakis(4-ethynylphenyl)porphyrin with 1,4-diiodobenzene in an anodic aluminum oxide plate. The length of the 1D structure was controlled in the range of 1-5 μm. The velvet worm surface-like microporous porphyrin networks (Velvet-MPNs) showed higher sensitivities to hydrogen chloride and ammonia gases by up to ∼14 and 4.6 times, respectively, compared with a control MPN material without rods.

Thin Coating of Microporous Organic Network Makes a Big Difference: Sustainability Issue of Ni Electrodes on the PET Textile for Flexible Lithium-Ion Batteries

Poly(ethylene terephthalate) fibers (PET-Fs) were coated with microporous organic networks (MONs) by the Sonogashira coupling of tetra(4-ethynylphenyl)methane with 1,4-diiodobenzene. Ni was deposited on the PET-F@MON via electroless deposition. Interestingly, although Ni on the PET-F showed a sharp decrease in conductivity in repeated bending tests, the PET-F@MON@Ni showed excellent retention of conductivity. We suggest that thin MON layers play roles of an efficient binder for Ni attachment to fibers and a structural buffer for the relaxation of bending strain. The positive effect of MON was supported by scanning electron microscopy studies of the PET-F@Ni or PET-F@MON@Ni retrieved after 2000 bending numbers. Although Ni on the PET-F showed severe detachment after bending tests, PET-F@MON@Ni retained the original morphologies. The pouch cells of lithium-ion batteries fabricated using PET-F@MON@Ni as the current collectors showed excellent performance against bending.

Application of a Smartphone Metabolomics Platform to the Authentication of Schisandra sinensis

INTRODUCTION Herbal medicines have been used for a long time all around the world. Since the quality of herbal preparations depends on the source of herbal materials, there has been a strong need to develop methods to correctly identify the origin of materials. OBJECTIVE To develop a smartphone metabolomics platform as a simpler and low-cost alternative for the identification of herbal material source. METHODOLOGY Schisandra sinensis extracts from Korea and China were prepared. The visible spectra of all samples were measured by a smartphone spectrometer platform. This platform included all the necessary measures built-in for the metabolomics research: data acquisition, processing, chemometric analysis and visualisation of the results. The result of the smartphone metabolomics platform was compared to that of NMR-based metabolomics, suggesting the feasibility of smartphone platform in metabolomics research. RESULTS The smartphone metabolomics platform gave similar results to the NMR method, showing good separation between Korean and Chinese materials and correct predictability for all test samples. CONCLUSION With its accuracy and advantages of affordability, user-friendliness, and portability, the smartphone metabolomics platform could be applied to the authentication of other medicinal plants. Copyright