bluuebunny/crossref_metadata_2025_split huggingface dataset:
Palladium‐Catalyzed Insertion of α‐Diazoesters into Vinyl Halides To Generate α,β‐Unsaturated γ‐Amino Esters
Authors: Kudirka Romas , Devine Sean K. J. , Adams Christopher S. , Van Vranken David L. 
Published: April 2009

AbstractAs easy as 1, 2, 3: A palladium‐catalyzed three‐component coupling generates α,β‐unsaturated γ‐amino acids in a single step (see scheme). The reaction is believed to involve migration of a vinyl substituent to a highly electrophilic palladium carbene. Unlike previous synthetic approaches, this synthesis provides access to γ‐amino acids with non‐natural side chains.magnified image
Coupling Microdroplet Microreactors with Mass Spectrometry: Reading the Contents of Single Droplets Online
Authors: Fidalgo Luis M. , Whyte Graeme , Ruotolo Brandon T. , Benesch Justin L. P. , Stengel Florian , Abell Chris , Robinson Carol V. , Huck Wilhelm T. S. 
Published: April 2009

AbstractFully integrated: Mass spectrometry has been integrated into a detection scheme for microdroplets that are created within microfluidic channels (see picture, scale bar 200 μm). This technique allows droplets to be identified based on the compounds they contain, and combines fluorescence screening with MS analysis. These experiments indicate how similar approaches can be applied to the ambitious goals of on‐chip protein evolution and chemical synthesis.magnified image
Unusual Interlocking and Interpenetration Lead to Highly Porous and Robust Metal–Organic Frameworks
Authors: Ma Liqing , Lin Wenbin 
Published: April 2009

AbstractStop the breathing: As the organic bridging ligands become more elaborate and large, the resulting MOFs tend to experience significant framework distortion (i.e., breathing) upon solvent removal. Rigidification of MOFs that are built from elongated tetracarboxylate bridging ligands by unusual interlocking and interpenetration leads to highly porous and robust hybrid materials.magnified image
Dual‐Function Probe to Detect Protease Activity for Fluorescence Measurement and 19F MRI
Authors: Mizukami Shin , Takikawa Rika , Sugihara Fuminori , Shirakawa Masahiro , Kikuchi Kazuya 
Published: April 2009

AbstractDynamic duo: Magnetic resonance imaging (MRI) can visualize deep regions of living bodies, whereas fluorescence measurement offers excellent sensitivity. These methods thus offer signal enhancement potential for detecting enzyme activities. A dual‐mode off/on probe to detect caspase‐3 activity by fluorescence and 19F MRI is presented.magnified image
Iridium Catalysis for CH Bond Arylation of Heteroarenes with Iodoarenes
Authors: Join Benoît , Yamamoto Takuya , Itami Kenichiro 
Published: April 2009

AbstractEfficient couplings using equimolar quantities of each coupling partner and multiple CH bond arylation reactions are achieved with an Ir‐based catalytic system for the CH bond arylation of electron‐rich heteroarenes with iodoarenes to construct extended π‐systems. The dramatic ligand effect on reaction efficiency leads to the discovery that Crabtree's catalyst (see scheme) is the optimal catalyst precursor.magnified image
Formal Total Synthesis of Platencin
Authors: Varseev Georgy N. , Maier Martin E. 
Published: April 2009

AbstractThe right bicycle: A concise formal synthesis of platencin was based on an efficient oxygen‐mediated palladium‐catalyzed cycloalkenylation of 1 to form a bicyclo[3.2.1]octane, and a deoxygenative rearrangement of tosylhydrazone 2 to construct the bicyclo[2.2.2]octane 3. The total yield of the core structure 4 of platencin was 17.5 % for 13 steps from a commercially available compound. Ts=p‐toluenesulfonyl, TBS=tert‐butyldimethylsilyl, Piv=pivaloyl.magnified image
Cover Picture: A Phosphorus Analogue of Bis(η4‐cyclobutadiene)iron(0) (Angew. Chem. Int. Ed. 17/2009)
Authors: Wolf Robert , Slootweg J. Chris , Ehlers Andreas W. , Hartl František , de Bruin Bas , Lutz Martin , Spek Anthony L. , Lammertsma Koop 
Published: April 2009

AbstractA rare phosphorus analogue of the elusive complex bis(η4‐cyclobutadiene)iron(0) is reported by K. Lammertsma et al. in their Communication on page 3104 ff. The background of the cover picture shows John Montagu (1718–1792), 4th Earl of Sandwich and 1st Lord of the Admiralty, who certainly would not have dreamt that an important class of organometallic compounds, sandwich complexes, would bear his name one day. The synthesis of [Fe(P2C2tBu2)2] shows that sandwich complexes are still topical objects of research.magnified image
Opinion mining and relationship discovery using CopeOpi opinion analysis system
Authors: Ku Lun‐Wei , Ho Hsiu‐Wei , Chen Hsin‐Hsi 
Published: April 2009

AbstractWe present CopeOpi, an opinion‐analysis system, which extracts from the Web opinions about specific targets, summarizes the polarity and strength of these opinions, and tracks opinion variations over time. Objects that yield similar opinion tendencies over a certain time period may be correlated due to the latent causal events. CopeOpi discovers relationships among objects based on their opinion‐tracking plots and collocations. Event bursts are detected from the tracking plots, and the strength of opinion relationships is determined by the coverage of these plots. To evaluate opinion mining, we use the NTCIR corpus annotated with opinion information at sentence and document levels. CopeOpi achieves sentence‐ and document‐level f‐measures of 62% and 74%. For relationship discovery, we collected 1.3M economics‐related documents from 93 Web sources over 22 months, and analyzed collocation‐based, opinion‐based, and hybrid models. We consider as correlated company pairs that demonstrate similar stock‐price variations, and selected these as the gold standard for evaluation. Results show that opinion‐based and collocation‐based models complement each other, and that integrated models perform the best. The top 25, 50, and 100 pairs discovered achieve precision rates of 1, 0.92, and 0.79, respectively.
On the Relative Preference of Enamine/Iminium Pathways in an Organocatalytic Michael Addition Reaction
Authors: Patil Mahendra P. , Sunoj Raghavan B. 
Published: April 2009

AbstractThe right path: The mechanism of organocatalyzed Michael addition between propanal and methyl vinyl ketone is investigated using the density functional and ab intio methods. The kinetic preference for the formation of key intermediates is established in an effort to identify the competing pathways associated with the reaction. The effect of co‐catalyst/protic solvent on the energetics of the reaction is also studiedmagnified imageThe mechanism of the organocatalyzed Michael addition between propanal and methyl vinyl ketone is investigated using the density functional and ab intio methods. Different modes of substrate activation offered by a secondary amine (pyrrolidine) organocatalyst are reported. The electrophilic activation of enone (P‐I) through the formation of an iminium ion, and nucleophilic activation of propanal (P‐II) in the form of enamine have been examined by identifying the corresponding transition states. The kinetic preference for the formation of key intermediates is established in an effort to identify the competing pathways associated with the title reaction. A comparison of barriers associated with different pathways as well as intermediate formation allows us to provide a suitable mechanistic rationale for Michael addition reactions catalyzed by a secondary amine. The overall barriers for the CC bond formation pathways involving enol or iminium intermediates are identified as higher than the enamine pathway. Additionally, the generation of iminium is found to be less favored as compared to enamine formation. The effect of co‐catalyst/protic solvent on the energetics of the overall reaction is also studied using the cluster continuum approach. Significant reduction in the activation energies for each step of the reaction is predicted for the solvent‐assisted models. The co‐catalyst assisted addition of propanal–enamine to methyl vinyl ketone is identified as the most preferred pathway (P‐IV) for the Michael addition reaction. The results are in concurrence with the available experimental reports on the rate acceleration by the use of a co‐catalyst in this reaction.
Functional role of Coenzyme Q in the energy coupling of NADH‐CoQ oxidoreductase (Complex I): Stabilization of the semiquinone state with the application of inside‐positive membrane potential to proteoliposomes
Authors: Ohnishi Tomoko , Ohnishi S. Tsuyoshi , Shinzawa‐Ito Kyoko , Yoshikawa Shinya 
Published: April 2009

AbstractCoenzyme Q10 (which is also designated as CoQ10, ubiquinone‐10, UQ10, CoQ, UQ or simply as Q) plays an important role in energy metabolism. For NADH‐Q oxidoreductase (complex I), Ohnishi and Salerno proposed a hypothesis that the proton pump is operated by the redox‐driven conformational change of a Q‐binding protein, and that the bound form of semiquinone (SQ) serves as its gate [FEBS Letters 579 (2005) 45–55]. This was based on the following experimental results: (i) EPR signals of the fast‐relaxing SQ anion (designated as Q) are observable only in the presence of the proton electrochemical potential (Δμ); (ii) iron‐sulfur cluster N2 and Q are directly spin‐coupled; and (iii) their center‐to‐center distance was calculated as 12Å, but Q is only 5Å deeper than N2 perpendicularly to the membrane. After the priming reduction of Q to Nf, the proton pump operates only in the steps between the semiquinone anion (Q) and fully reduced quinone (QH2). Thus, by cycling twice for one NADH molecule, the pump transports 4H+ per 2e−.This hypothesis predicts the following phenomena: (a) Coupled with the piericidin A sensitive NADH‐DBQ or Q1 reductase reaction, Δμ would be established; (b) Δμ would enhance the SQ EPR signals; and (c) the dissipation of Δμ with the addition of an uncoupler would increase the rate of NADH oxidation and decrease the SQ signals.We reconstituted bovine heart complex I, which was prepared at Yoshikawa's laboratory, into proteoliposomes. Using this system, we succeeded in demonstrating that all of these phenomena actually took place. We believe that these results strongly support our hypothesis.
Function of a bound ubiquinone in Escherichia coli quinoprotein glucose dehydrogenase
Authors: Mustafa Golam , Ishikawa Yoshinori , Kobayashi Kazuo , Migita Catharina T. , Tagawa Seiichi , Yamada Mamoru 
Published: April 2009

AbstractMembrane‐bound glucose dehydrogenase (mGDH) is a single integral protein in the respiratory chain in Escherichia coli which oxidizes D‐glucose and feeds electrons to ubiquinol oxidase via bulk ubiquinone (UQ). mGDH contains a bound UQ, CoQ8, for its intramolecular electron transfer in addition to pyrroloquinoline quinone (PQQ) as a coenzyme. Pulse radiolysis analysis revealed that the bound UQ exists very close to PQQ at a distance of 11–13 Å. Studies on mGDH mutants with substitutions for amino acid residues around PQQ showed that Asp‐466 and Lys‐493, which are crucial for catalytic activity, interact with bound UQ. Based on these findings, we propose that the bound UQ is involved in the catalytic reaction in addition to the intramolecular electron transfer in mGDH.
Effect of CoQ homologues on reactive oxygen generation by mitochondria
Authors: Imada Isuke , Sato Eisuke F. , Kira Yukimi , Inoue Masayasu 
Published: April 2009

AbstractEffect of CoQ compounds (Qs) on reactive oxygen (ROS) generation by mitochondrial complex I was studied using rat liver mitochondria and chemiluminescence probe L012. Kinetic analysis revealed that short chain Qs, such as Q2 and idebenone enhanced ROS generation by mitochondrial NADH oxidase system by a succinate‐inhibitable mechanism. Lipid peroxidation in mitochondrial membranes induced by NADH and iron was inhibited by short chain Qs. The inhibitory activity was enhanced by co‐oxidation of succinate as determined by chemiluminescence method and by electron spin resonance spectroscopy. These results suggested that the reduced form of short chain Qs inhibited mitochondrial ROS generation and lipid peroxidation.
Comparison between the free‐radical‐scavenging activities with vitamin E and ubiquinol in biological systems based on their reaction rates: A research account
Authors: Mukai Kazuo , Tokunaga Aiko , Itoh Shingo , Kanesaki Yu , Ouchi Aya , Ohara Keishi , Nagaoka Shin‐ichi , Abe Kouichi 
Published: April 2009

AbstractDetailed kinetic studies have been performed for the reaction of aroxyl (ArO•) radical with vitamin E (α‐, β‐, γ‐, δ‐tocopherol, TocH), ubiquinol‐10, and related antioxidants in micellar solution, using a stopped‐flow spectrophotometer. The second‐order reaction rates (κs) obtained increased in the order of hydroquinone<tocol< δ‐TocH<ubiquinol‐0< γ‐TocH∼ β‐TocH<ubiquinol‐10< α‐TocH at pH 4 ∼ 8. The antioxidants which have lower oxidation potentials (Eρ ) showed higher reactivities. The reaction rates obtained in micellar solution were pH dependent because of the dissociation of OH groups in the antioxidants. For instance, by comparing the κs values with the mole fraction of each molecular form of ubiquinol‐10, the reaction rate κs1 (1.21×105 M−1 s−1 ) for undissociated form, κs2 (1.04 × 106 M−1 s−1 ) for monoanion and κs3 (0 M−1 s−1 ) for dianion, and the pKa1 and pKa2 values (11.4 and 12.7) were determined. It was found that the relative ratio of κs values (100:21:20:2.9) of α‐, β‐, γ‐, δ‐tocopherols in micellar dispersion has good correlation with the relative biological activities for rat fetal resorption, rat haemolysis, and chicken muscle dystrophy. The relative antioxidant activities of α‐tocopherol and ubiquinol‐10 have been discussed on the basis of the products of the κs values and their concentrations in serum and several tissues (heart, muscle, liver, kidney, and brain).
NADPH‐dependent coenzyme Q reductase is the main enzyme responsible for the reduction of non‐mitochondrial CoQ in cells
Authors: Takahashi Takayuki , Okuno Masaaki , Okamoto Tadashi , Kishi Takeo 
Published: April 2009

AbstractWe purified an NADPH‐dependent coenzyme Q reductase (NADPH‐CoQ reductase) in rat liver cytosol and compared its enzymatic properties with those of the other CoQ10 reductases such as NADPH: quinone acceptor oxidoreductase 1 (NQO1), lipoamide dehydrogenase, thioredoxine reductase and glutathione reductase. NADPH‐CoQ reductase was the only enzyme that preferred NADPH to NADH as an electron donor and was also different from the other CoQ10 reductases in the sensitivities to its inhibitors and stimulators. Especially, Zn2+ was the most powerful inhibitor for NADPH‐CoQ reductase, but CoQ10 reduction by the other CoQ10 reductases could not be inhibited by Zn2+. Furthermore, the reduction of the CoQ9 incorporated into HeLa cells was also inhibited by Zn2+ in the presence of pyrithione, a zinc ionophore. Moreover, NQO1 gene silencing in HeLa cells by transfection of a small interfering RNA resulted in lowering of both the NQO1 protein level and the NQO1 activity by about 75%. However, this transfection did not affect the NADPH‐CoQ reductase activity and the reduction of CoQ9 incorporated into the cells. These results suggest that the NADPH‐CoQ reductase located in cytosol may be the main enzyme responsible for the reduction of non‐mitochondrial CoQ in cells.
High production of sulfide in coenzyme Q deficient fission yeast
Authors: Zhang Mei , Wakitani Shusoh , Hayashi Kazuhiro , Miki Risa , Kawamukai Makoto 
Published: April 2009

AbstractWe have constructed coenzyme Q deficient fission yeast strains by deletion of ten different genes, all of which are absolutely required for the CoQ10 biosynthesis. We found that sulfide was highly accumulated in all fission yeast CoQ10 deficient mutants. In fission yeast sulfide is required for the synthesis of cysteine and homocysteine which are catalyzed by cysteine synthase (Cys1a) and homocysteine synthase (Met17), respectively. To better understand the relation between sulfide metabolism and coenzyme Q, we expressed cys1a, met17 and hmt2, which encodes sulfide‐quinone oxidoreductase, in CoQ10 deficient mutants and other mutants, and measured the level of sulfide. Although expression of cys1a and met17 lowered sulfide production in CoQ10 deficient mutants, hmt2 did not lower the level of sulfide, because Hmt2 requires coenzyme Q for its function. In contrast, expression of hmt2 lowered sulfide production in cys1a and met17 mutants. These and other results indicate that coenzyme Q is important for sulfide oxidation through sulfide‐quinone oxidoreductase to detoxify excess sulfide in fission yeast.
Stimulation of coenzyme Q synthesis
Authors: Bentinger Magnus , Tekle Michael , Brismar Kerstin , Chojnacki Tadeusz , Swiezewska Ewa , Dallner Gustav 
Published: April 2009

AbstractUptake of dietary coenzyme Q (CoQ) into organs is limited but there are some exceptions such as adrenal glands and ovaries. Under deficient conditions an optimal solution could be stimulation of the endogenous synthesis. In rodent exercise, cold exposure and a few substances elevate the CoQ levels to some extent. Investigations of the nuclear receptors PPARα, RXRα and LXRα&β did not answer the question which nuclear receptor regulates CoQ biosynthesis and at present we cannot design a ligand for upregulation of the synthesis. Upon ultraviolet irradiation of CoQ a number of products are formed which influence the synthesis of the mevalonate pathway lipids. Among them epoxidated derivatives were identified. Upon chemical epoxidation of a series of polyisoprenoids it was found that none of the tested poly‐cis polyisoprenols had any effect but some of the all‐trans polyisoprenols stimulated CoQ synthesis and in some cases also inhibited cholesterol biosynthesis. Tocotrienol epoxides were proved to be very efficient, those having one epoxide in the side chain doubled or trebled the CoQ synthesis while those with two epoxides additionally also inhibited cholesterol synthesis by 50–90%. The elevation of CoQ synthesis was elicited by increased mRNA levels for biosynthetic enzymes while the inhibition point in the cholesterol synthesis was localized to oxidosqualene cyclase.
Human CoQ10 deficiencies
Authors: Quinzii C. M. , López L. C. , Naini A. , DiMauro S. , Hirano M. 
Published: April 2009

AbstractCoenzyme Q10 (CoQ10 or ubiquinone) is a lipid‐soluble component of virtually all cell membranes and has multiple metabolic functions. A major function of CoQ10 is to transport electrons from complexes I and II to complex III in the respiratory chain which resides in the mitochondrial inner membrane. Deficiencies of CoQ10 (MIM 607426) have been associated with four major clinical phenotypes: 1) encephalomyopathy characterized by a triad of recurrent myoglobinuria, brain involvement, and ragged‐red fibers; 2) infantile multisystemic disease typically with prominent nephropathy and encephalopathy; 3) cerebellar ataxia with marked cerebellar atrophy; and 4) pure myopathy. Primary CoQ10 deficiencies due to mutations in ubiquinone biosynthetic genes (COQ2, PDSS1, PDSS2, and ADCK3 [CABC1]) have been identified in patients with the infantile multisystemic and cerebellar ataxic phenotypes. In contrast, secondary CoQ10 deficiencies, due to mutations in genes not directly related to ubiquinone biosynthesis (APTX, ETFDH, and BRAF), have been identified in patients with cerebellar ataxia, pure myopathy, and cardiofaciocutaneous syndrome. In many patients with CoQ10 deficiencies, the causative molecular genetic defects remain unknown; therefore, it is likely that mutations in additional genes will be identified as causes of CoQ10 deficiencies.
Positive inotropic effect of coenzyme Q10, omega‐3 fatty acids and propionyl‐L‐carnitine on papillary muscle force‐frequency responses of BIO TO‐2 cardiomyopathic Syrian hamsters
Authors: Vargiu Romina , Littarru Gian Paolo , Faa Gavino , Mancinelli Rino 
Published: April 2009

AbstractThe inability of heart muscle to generate ventricular pressure to adequately propel blood through the cardiovascular system is a primary defect associated with congestive heart failure (CHF).Force‐frequency relationship (FFR) is one of the main cardiac defects associated with congestive heart failure. Thus FFR is a convenient methodological tool for evaluating the severity of muscle contractile dysfunction and the effectiveness of therapeutic agents. Papillary muscle isolated from BIO TO‐2 cardiomyopathic Syrian hamsters (CMSHs), show a depressed FFR and represents an animal model of human idiopathic dilated cardiomyopathy. In the present study we investigated the effect of CoQ10, omega‐3 fatty acids, propionyl‐L‐carnitine (PLC) and a combination of these 3 agents (formulation HS12607) on FFR in 8 month old BIO TO‐2 CMSHs. Papillary muscles isolated from the anesthetized animals were placed in an incubation bath and attached to an isometric force transducer. A digital computer with an analog/digital interface allowed control of both muscle developed force and electrical stimulus parameters. Force‐frequency response was evaluated, at Lmax, with increasing frequencies: 0.06, 0.12, 0.25, 0.5, 1, 2 and 4 Hz. HS12607‐treatment produced a positive inotropic effect resulting in a significant enhancement (p < 0.05) of the peak force at the highest frequencies (1–4 Hz). In the range of frequency of 1–4 Hz also CoQ10 and omega‐3 significantly(p < 0.05) attenuated the fractional decline in developed force. The significant improvement (p < 0.05) of the timing parameter peak rate of tension rise (+T') and peak rate of tension fall (−T') indicating a faster rate of muscle contraction and relaxation respectively, found in CoQ10, omega‐3 and PLC‐treated CMSHs, may be due to the positive effects of these substances on sarcoplasmic reticulum functions. These findings suggest that naturally occurring CoQ10, omega‐3 and PLC, particularly when administered together in a coformulation, might be a valid adjuvant to conventional therapy in dilated cardiomyopathy especially when considering that they are natural substances, devoid of side effects.
Coenzyme Q10 (CoQ10) in isolated diastolic heart failure in hypertrophic cardiomyopathy (HCM)
Authors: Adarsh K. , Kaur H. , Mohan V. 
Published: April 2009

AbstractIt is well known that by improving mitochondrial bioenergetics, Coenzyme Q10 improves the systolic function in heart failure. The aim of this study was to see whether it benefits the diastolic dysfunction in hypertrophic cardiomyopathy (HCM) cases since diastolic relaxation also requires energy like the systole. 200 mg/day of CoQ10 was added to the conventional treatment in 46 patients with HCM diagnosed clinically and by echocardiography and by excluding cases of long standing hypertension. A comparable group of 41 age/sex matched cases received only conventional therapy. There was a significant improvement in the parameters like NYHA class ≥ 1, in quality of life (QOL) on 6 minutes walk test, in diastolic dysfunction by ≥1 parameter and in MR ≥ 1 grade. Post treatment echocardiogram showed significant reduction in left ventricular outflow tract ( LVOT) gradient ≥15 mm Hg in obstructive cases (12 out of 46) in the treatment group. The mean interventricular septal thickness (IVS) showed a 22.4% reduction (p < 0.005). The mean posterior wall thickness showed a 23.1% reduction (p < 0.005). No patient in the treatment Group had ventricular tachycardia (VT) whereas 4 cases in the control group had VT. In both groups 1 patient was lost due to sudden cardiac death (SCD).