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Asymmetric and Selective Biocatalysis

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ISBN: 9783038978466 9783038978473 Year: Pages: 154 DOI: 10.3390/books978-3-03897-847-3 Language: eng
Publisher: MDPI - Multidisciplinary Digital Publishing Institute
Subject: Science (General) --- Chemistry (General)
Added to DOAB on : 2019-06-26 09:16:44
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This Issue contains one communication, six articles, and two reviews. The communication from Paola Vitale et al. represents a work where whole cells were used as biocatalysts for the reduction of optically active chloroalkyl arylketones followed by a chemical cyclization to give the desired heterocycles. Among the various whole cells screened (baker’s yeast, Kluyveromyces marxianus CBS 6556, Saccharomyces cerevisiae CBS 7336, Lactobacillus reuteri DSM 20016), baker’s yeast provided the best yields and the highest enantiomeric ratios (95:5) in the bioreduction of the above ketones. In this respect, valuable chiral non-racemic functionalized oxygen-containing heterocycles (e.g., (S)-styrene oxide, (S)-2-phenyloxetane, (S)-2-phenyltetrahydrofuran), amenable to be further elaborated on, can be smoothly and successfully generated from their prochiral precursors. Studies about pure biocatalysts with mechanistical studies, application in different reactions, and new immobilization methods for improving their stability were reported in five different articles. The article by Su-Yan Wang et al. describes the cloning, expression, purification, and characterization of an N-acetylglucosamine 2-epimerase from Pedobacter heparinus (PhGn2E). For this, several N-acylated glucosamine derivatives were chemically synthesized and used to test the substrate specificity of the enzyme. The mechanism of the enzyme was studied by hydrogen/deuterium NMR. The study at the anomeric hydroxyl group and C-2 position of the substrate in the reaction mixture confirmed the epimerization reaction via ring-opening/enolate formation. Site-directed mutagenesis was also used to confirm the proposed mechanism of this interesting enzyme. The article by Forest H. Andrews et al. studies two enzymes, benzoylformate decarboxylase (BFDC) and pyruvate decarboxylase (PDC), which catalyze the non-oxidative decarboxylation of 2-keto acids with different specificity. BFDC from Pseudomonas putida exhibited very limited activity with pyruvate, whereas the PDCs from S. cerevisiae or from Zymomonas mobilis showed virtually no activity with benzoylformate (phenylglyoxylate). After studies using saturation mutagenesis, the BFDC T377L/A460Y variant was obtained, with 10,000-fold increase in pyruvate/benzoylformate. The change was attributed to an improvement in the Km value for pyruvate and a decrease in the kcat value for benzoylformate. The characterization of the new catalyst was performed, providing context for the observed changes in the specificity. The article by Xin Wang et al. compares two types of biocatalysts to produce D-lysine L-lysine in a cascade process catalyzed by two enzymes: racemase from microorganisms that racemize L-lysine to give D,L-lysine and decarboxylase that can be in cells, permeabilized cells, and the isolated enzyme. The comparison between the different forms demonstrated that the isolated enzyme showed the higher decarboxylase activity. Under optimal conditions, 750.7 mmol/L D-lysine was finally obtained from 1710 mmol/L L-lysine after 1 h of racemization reaction and 0.5 h of decarboxylation reaction. D-lysine yield could reach 48.8% with enantiomeric excess (ee) of 99%. In the article by Rivero and Palomo, lipase from Candida rugosa (CRL) was highly stabilized at alkaline pH in the presence of PEG, which permitted its immobilization for the first time by multipoint covalent attachment on different aldehyde-activated matrices. Different covalent immobilized preparation of the enzyme was successfully obtained. The thermal and solvent stability was highly increased by this treatment, and the novel catalysts showed high regioselectivity in the deprotection of per-O-acetylated nucleosides. The article by Robson Carlos Alnoch et al. describes the protocol and use of a new generation of tailor-made bifunctional supports activated with alkyl groups that allow the immobilization of proteins through the most hydrophobic region of the protein surface and aldehyde groups that allows the covalent immobilization of the previously adsorbed proteins. These supports were especially used in the case of lipase immobilization. The immobilization of a new metagenomic lipase (LipC12) yielded a biocatalyst 3.5-fold more active and 5000-fold more stable than the soluble enzyme. The PEGylated immobilized lipase showed high regioselectivity, producing high yields of the C-3 monodeacetylated product at pH 5.0 and 4 °C. Hybrid catalysts composed of an enzyme and metallic complex are also treated in this Special Issue. The article by Christian Herrero et al. describes the development of the Mn(TpCPP)-Xln10A artificial metalloenzyme, obtained by non-covalent insertion of Mn(III)-meso-tetrakis(p-carboxyphenyl)porphyrin [Mn(TpCPP), 1-Mn] into xylanase 10A from Streptomyces lividans (Xln10A). The complex was found able to catalyze the selective photo-induced oxidation of organic substrates in the presence of [RuII(bpy)3]2+ as a photosensitizer and [CoIII(NH3)5Cl]2+ as a sacrificial electron acceptor, using water as oxygen atom source. The two published reviews describe different subjects with interest in the fields of biocatalysis and mix metallic-biocatalysis, respectively. The review by Anika Scholtissek et al. describes the state-of-the-art regarding ene-reductases from the old yellow enzyme family (OYEs) to catalyze the asymmetric hydrogenation of activated alkenes to produce chiral products with industrial interest. The dependence of OYEs on pyridine nucleotide coenzyme can be avoided by using nicotinamide coenzyme mimetics. In the review, three main classes of OYEs are described and characterized. The review by Yajie Wang and Huimin Zhao highlights some of the recent examples in the past three years that combine transition metal catalysis with enzymatic catalysis. With recent advances in protein engineering, catalyst synthesis, artificial metalloenzymes, and supramolecular assembly, there is great potential to develop more sophisticated tandem chemoenzymatic processes for the synthesis of structurally complex chemicals. In conclusion, these nine publications give an overview of the possibilities of different catalysts, both traditional biocatalysts and hybrids with metals or organometallic complexes to be used in different processes—particularly in synthetic reactions—under very mild reaction conditions.

Coordination Chemistry of Silicon

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ISBN: 9783038976387 Year: Pages: 225 DOI: 10.3390/books978-3-03897-639-4 Language: eng
Publisher: MDPI - Multidisciplinary Digital Publishing Institute
Subject: Science (General) --- Chemistry (General) --- Inorganic Chemistry
Added to DOAB on : 2019-03-08 11:42:05
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The chemistry of silicon has always been a field of major concern due to its proximity to carbon on the periodic table. From the molecular chemist's viewpoint, one of the most interesting differences between carbon and silicon is their divergent coordination behavior. In fact, silicon is prone to form hyper-coordinate organosilicon complexes, and, as conveyed by reports in the literature, highly sophisticated ligand systems are required to furnish low-coordinate organosilicon complexes. Tremendous progress in experimental, as well as computational, techniques has granted synthetic access to a broad range of coordination numbers for silicon, and the scientific endeavor, which was ongoing for decades, was rewarded with landmark discoveries in the field of organosilicon chemistry. Molecular congeners of silicon(0), as well as silicon oxides, were unveiled, and the prominent group 14 metalloid proved its applicability in homogenous catalysis as a supportive ligand or even as a center of catalytic activity. This book focuses on the most recent advances in the coordination chemistry of silicon with transition metals as well as main group elements, including the stabilization of low-valent silicon species through the coordination of electron donor ligands. Therefore, this book is associated with the development of novel synthetic methodologies, structural elucidations, bonding analysis, and also possible applications in catalysis or chemical transformations using related organosilicon compounds.

Keywords

silanetriols --- disiloxane tetrols --- silsesquioxanes --- condensation --- molecular cage --- platinum --- primary silane --- hydrido complex --- oxidative addition --- ligand-exchange reaction --- X-ray crystallography --- Si–Cl activation --- germylene --- digermene --- digermacyclobutadiene --- palladium --- cluster --- cyclic organopolysilane --- template --- bridging silylene ligand --- isocyanide --- hydrogen bonds --- silicon --- 2-silylpyrrolidines --- stereochemistry --- X-ray crystallography --- Baird’s rule --- computational chemistry --- excited state aromaticity --- Photostability --- dye-sensitized solar cell --- disilanylene polymer --- photoreaction --- surface modification --- TiO2 --- silylene --- germylene --- N-heterocyclic carbene --- oxidative addition --- siloxanes --- host-guest chemistry --- supramolecular chemistry --- main group coordination chemistry --- hydrogen bonding --- adsorption --- bond activation --- bonding analysis --- density functional theory --- distorted coordination --- molecular orbital analysis --- silicon surfaces --- disilene --- functionalization --- ?-electron systems --- silicon --- N-heterocyclic carbenes --- bromosilylenes --- silyliumylidenes --- dehydrobromination --- silicon cluster --- siliconoid --- nanoparticle --- computation --- silicon --- N-heterocyclic carbenes --- silyliumylidenes --- small molecule activation --- mechanistic insights --- organosilicon --- reductant --- N-Heterocyclic tetrylene --- salt-free --- germanium --- germanethione --- germathioacid chloride --- N-heterocyclic carbines --- ?-chloro-?-hydrooligosilane --- titanium --- ruthenium --- dehydrogenative alkoxylation --- cluster --- isomerization --- silicon --- siliconoid --- subvalent compounds --- AIM --- DFT --- intermetallic bond --- 29Si NMR spectroscopy --- X-ray diffraction

Special Issue Dedicated to Late Professor Takuo Okuda. Tannins and Related Polyphenols Revisited: Chemistry, Biochemistry and Biological Activities

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ISBN: 9783038978343 / 9783038978350 Year: Pages: 316 DOI: 10.3390/books978-3-03897-835-0 Language: eng
Publisher: MDPI - Multidisciplinary Digital Publishing Institute
Subject: Medicine (General)
Added to DOAB on : 2019-06-26 10:09:00
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Antioxidative polyphenols represented by tannins and flavonoids are rich in numerous food sources and traditional natural medicines and currently attracting increased attention in health care and food industries because of their multiple biological activities that are favorable to human health. Commemorating the outstanding achievements on tannins by Dr. Takuo Okuda on the occasion of his passing away in December 2016, his colleagues, friends, and worldwide experts of polyphenol research have contributed 18 papers on their recent study to the Special Issue of Molecules. This book is its reprinted form. This covers reviews of structural features, historical usages, and biological activities of unique class of ellagitannins and condensed tannins, and original articles on the most up-to-date findings on the anticancer effect of green tea catechins, the antivirus effect of tannins comparing with the clinically used drugs, the analytical method of ellagitannins using quantitative NMR, the chemical structures of Hydrangea-blue complex (pigment) and condensed tannins in Ephedra sinica and purple prairie clover, and the relationship of condensed tannins in legumes and grape-marc with methane production in the in vitro ruminant system, and others. This book will be useful to natural product chemists and also to researchers in pharmaceutical and/or food industry.

Keywords

Dittrichia viscosa --- antifungal activities --- Candida spp. --- Malassezia spp. --- Microsporum canis --- Aspergillus fumigates --- Ephedra sinica --- proanthocyanidin --- oligomer --- thiolysis --- phloroglucinolysis --- TDDFT --- ECD --- neuraminidase --- inhibition --- tannins --- oseltamivir carboxylate --- zanamivir --- crystal structure --- molecular interactions --- oenothein B --- ellagitannin --- macrocyclic oligomer --- Onagraceae --- Myrtaceae --- Lythraceae --- antioxidants --- antitumor effect --- immunomodulatory effect --- anti-inflammation --- tannin composition --- purple prairie clover --- conservation method --- protein precipitation --- Escherichia coli --- Cynanchum wilfordii --- phenolic glycoside --- 2-O-?-laminaribiosyl-4-hydroxyacetophenone --- cynandione A --- thin layer chromatography --- Cynanchum auriculatum --- Acacia mearnsii bark --- wattle tannin --- proanthocyanidins --- biological activities --- tannins --- vegetable tanning --- European historic leathers --- colorimetric tests --- spectroscopy --- UV-Vis --- FTIR --- triple-negative breast cancer --- fatty acid synthase --- FASN inhibition --- polyphenolic FASN inhibitors --- (?)-epigallocatechin 3-gallate --- synthetic analogues --- apoptosis --- anticancer activity --- 1H-NMR --- quantitative NMR --- ellagitannin --- Geranium thunbergii --- geraniin --- Aluminum ion --- blue color development --- 5-O-caffeoylquinic acid --- 3-O-glucosyldelphinidin --- Hydrangea macrophylla --- ESI-mass --- metal complex --- Coreopsis lanceolata L. --- chalcone --- flavanone --- flavonol --- aurone --- Horner–Wadsworth–Emmons reaction --- condensed tannin --- bioactivity --- methanogenesis --- grape marc --- fatty acids --- in vitro batch fermentation --- neuroprotection --- PC12 --- NGF --- differentiation --- amyloid-? peptide --- taxanes --- hormesis --- polyphenol --- bamboo leaf extract --- overlay method --- ellagitannin --- structure --- revision --- (?)-epigallocatechin gallate --- immune checkpoint --- interferon-? --- epidermal growth factor --- lung tumor --- proanthocyanidins --- condensed tannins --- thiolysis --- NMR spectroscopy --- ultrahigh-resolution negative mode MALDI-TOF mass spectrometry --- antioxidant --- ORAC assay --- Acacia --- forage legume --- Trapa taiwanensis Nakai --- hydrolysable tannin --- stability --- gallotannin --- ellagitannin

Breastfeeding and Human Lactation

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ISBN: 9783038979302 / 9783038979319 Year: Pages: 450 DOI: 10.3390/books978-3-03897-931-9 Language: eng
Publisher: MDPI - Multidisciplinary Digital Publishing Institute
Subject: Science (General) --- Biology --- Nutrition and Food Sciences
Added to DOAB on : 2019-06-26 08:44:06
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Human lactation has evolved to produce a milk composition that is uniquely-designed for the human infant. Not only does human milk optimize infant growth and development, it also provides protection from infection and disease. More recently, the importance of human milk and breastfeeding in the programming of infant health has risen to the fore. Anchoring of infant feeding in the developmental origins of health and disease has led to a resurgence of research focused in this area. Milk composition is highly variable both between and within mothers. Indeed the distinct maternal human milk signature, including its own microbiome, is influenced by environmental factors, such as diet, health, body composition and geographic residence. An understanding of these changes will lead to unravelling the adaptation of milk to the environment and its impact on the infant. In terms of the promotion of breastfeeding, health economics and epidemiology is instrumental in shaping public health policy and identifying barriers to breastfeeding. Further, basic research is imperative in order to design evidence-based interventions to improve both breastfeeding duration and women’s breastfeeding experience.

Keywords

human milk --- breastfed infants --- body composition --- anthropometrics --- milk intake --- bioelectrical impedance spectroscopy --- ultrasound skinfolds --- maternal factors --- infant --- feeding --- preterm --- premature --- bottle --- human milk --- breastfeeding --- nipple shield --- infant feeding --- choline --- phosphocholine --- glycerophosphocholine --- lactation --- human milk --- infants --- adequate intake --- dietary recommendations --- Canada --- Cambodia --- breast milk --- galactogogues --- mothers of preterm infants --- breastfeeding --- attitudes --- knowledge --- midwifery --- formula supplementation --- justification of supplementation --- maternal wellbeing --- maternal distress --- post-partum distress --- breastfeeding support --- paternal role --- partner support --- infant --- Ireland --- passive immunity --- antibodies --- lactation --- peptidomics --- prematurity --- proteolysis --- breast milk --- preterm infant --- enteral nutrition --- lipids --- omega-3 fatty acids --- omega-6 fatty acids --- Docosahexaenoic acid --- Arachidonic acid --- long-chain polyunsaturated fatty acids --- pregnancy --- breast milk --- lactation --- maternal diet --- n-6 and n-3 polyunsaturated fatty acid --- docosahexaenoic acid --- zinc deficiency --- plasma zinc --- lactating women --- zinc supplementation --- Quito --- Ecuador --- Andean region --- GDM --- lactation --- thyroid --- triiodothyronine --- thyroxine --- thyroid antibodies --- breastfeeding --- knowledge --- practice --- barriers --- social support --- professional support --- raw breast milk --- cytomegalovirus --- milk-acquired infections --- preterm infant --- adipokines --- adiponectin --- leptin --- breastfeeding --- infant --- body composition --- bioelectrical impedance spectroscopy --- ultrasound skinfolds --- human milk --- lactation --- human lactation --- expressing --- milk synthesis --- fat synthesis --- human milk --- milk metabolites --- lactation --- milk metabolomics --- human milk --- breastfeeding --- lactation --- lipids --- lipidomics --- mass spectrometry --- chromatography --- NMR spectroscopy --- human milk --- sex-specificity --- infant growth --- early life nutrition --- postnatal outcomes --- breastfeeding --- breast milk --- human milk --- colostrum --- IgA --- HGF --- TGF-? --- growth factors --- geographical location --- human milk --- potassium --- sodium --- ICP-OES --- ion selective electrode --- lactoferrin --- human milk --- infection --- immunity --- antisecretory factor --- human milk --- breast milk --- breastfeeding --- inflammation --- lactoferrin --- candida --- human milk --- milk cells --- immune cells --- antimicrobial proteins --- human milk --- breastfeeding --- ethnicity --- composition --- diet --- responsive feeding --- breastfeeding --- breastmilk --- babywearing --- co-sleeping --- mother–infant interaction --- feeding cues --- maternal responsiveness --- mother–infant physical contact --- proximal care --- fatty acids --- long-chain polyunsaturated fatty acids --- endocannabinoids --- infant health --- breast milk --- casein --- whey --- protein --- breastfeeding --- infant --- body composition --- bioelectrical impedance spectroscopy --- ultrasound skinfolds --- human milk --- calculated daily intakes --- lactation --- human milk --- metabolites --- microbiome --- mode of delivery --- caesarean section --- proton nuclear magnetic resonance --- breastfeeding --- human milk composition --- body composition --- maternal diet --- infant growth --- appetite regulation --- N-acylethanolamines --- OEA --- SEA --- PEA --- breastfeeding --- human milk composition --- obesity --- Breastfeeding --- human lactation --- lactation --- human milk --- breast milk --- milk composition

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