57-13-6

Real-Time in Vivo Detection of H2O2 Using Hyperpolarized 13C-Thiourea

Wibowo, Arif,Park, Jae Mo,Liu, Shie-Chau,Khosla, Chaitan,Spielman, Daniel M.

, p. 1737 - 1742 (2017)

Reactive oxygen species (ROS) are essential cellular metabolites widely implicated in many diseases including cancer, inflammation, and cardiovascular and neurodegenerative disorders. Yet, ROS signaling remains poorly understood, and their measurements are a challenge due to high reactivity and instability. Here, we report the development of 13C-thiourea as a probe to detect and measure H2O2 dynamics with high sensitivity and spatiotemporal resolution using hyperpolarized 13C magnetic resonance spectroscopic imaging. In particular, we show 13C-thiourea to be highly polarizable and to possess a long spin-lattice relaxation time (T1), which enables real-time monitoring of ROS-mediated transformation. We also demonstrate that 13C-thiourea reacts readily with H2O2 to give chemically distinguishable products in vitro and validate their detection in vivo in a mouse liver. This study suggests that 13C-thiourea is a promising agent for noninvasive detection of H2O2 in vivo. More broadly, our findings outline a viable clinical application for H2O2 detection in patients with a range of diseases.

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Walker,Kay

, p. 489 (1897)

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Ross

, p. 690 (1914)

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Surrey,Nachod

, p. 2336 (1951)

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Evidence for an inhibitory LIM domain in a rat brain agmatinase-like protein

Castro, Victor,Fuentealba, Pablo,Henriquez, Adolfo,Vallejos, Alejandro,Benitez, Jose,Lobos, Marcela,Diaz, Beatriz,Carvajal, Nelson,Uribe, Elena

, p. 107 - 110 (2011)

We recently cloned a rat brain agmatinase-like protein (ALP) whose amino acid sequence greatly differs from other agmatinases and exhibits a LIM-like domain close to its carboxyl terminus. The protein was immunohistochemically detected in the hypothalamic region and hippocampal astrocytes and neurons. We now show that truncated species, lacking the LIM-type domain, retains the dimeric structure of the wild-type protein but exhibits a 10-fold increased kcat, a 3-fold decreased Km value for agmatine and altered intrinsic tryptophan fluorescent properties. As expected for a LIM protein, zinc was detected only in the wild-type ALP (～2 Zn2+/monomer). Our proposal is that the LIM domain functions as an autoinhibitory entity and that inhibition is reversed by interaction of the domain with some yet undefined brain protein.

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Hofmeister

, (1896)

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Wyatt,Kornberg

, p. 454,458 (1952)

Aminoguanidinium hydrolysis effected by a hydroxo-bridged Dicobalt(II) complex as a functional model for arginase and catalyzed by mononuclear Cobalt(II) complexes

He, Chuan,Lippard, Stephen J.

, p. 105 - 113 (1998)

The dinuclear complex [Co2(μ-OH)(μ-XDK)(bpy)2(EtOH)](NO3), where XDK is the dinucleating dicarboxylate ligand m-xylylenediamine bis(Kemp's triacid imide) and bpy = 2,2'-bipyridine, was prepared as a functional model for arginase. The substrate aminoguanidinium nitrate was hydrolyzed to urea in ethanol by the complex but not by free hydroxide ion under the same conditions. The amino group of the substrate binds to cobalt, as demonstrated by W-vis spectroscopic studies. The syntheses of related dinuclear cobalt(II) complexes [Co2(μ-XDK)(NO3)2(CH3OH)2(H2O)], [Co2(μ-Cl)(μ-XDK)(bpy)2(EtOH)2](NO3), and [Co2(μ-XDK)-(py)3(NO3)2] are described. Mononuclear complexes [Co(XDK)(bpy)(H2O)] and [Zn(XDK)(bpy)(H2O)] were also prepared and characterized. The former catalytically hydrolyzes aminoguanidinium nitrate to urea in basic 1:1 methanol/water solutions, whereas the latter does not promote this reaction. Hydrolysis of aminoguanidinium ion is effected by [Co(CH3COO)2] and [Cu(CH3COO)2] in the presence of bpy, but not by [Zn(CH3COO))2], [Ni(CH3COO)2], or [Mn(CH3COO)2] in the presence of bpy in 1:1 methanol/water solution. In all cases, coordination of the amino group of the substrate to the metal center under the reaction conditions may activate the leaving group and orient the guanidinium moiety close to the attacking nucleophile, metal-bound hydroxide ion, to promote the hydrolysis reaction.

Photocatalytic synthesis of urea from in situ generated ammonia and carbon dioxide

Srinivas, Basavaraju,Kumari, Valluri Durga,Sadanandam, Gullapelli,Hymavathi, Chilumula,Subrahmanyam, MacHiraju,De, Bhudev Ranjan

, p. 233 - 241 (2012)

TiO2 and Fe-titanate (different wt%) supported on zeolite were prepared by sol-gel and solid-state dispersion methods. The photocatalysts prepared were characterized by X-ray diffraction, scanning electron microscopy and ultraviolet (UV)-visible diffuse reflectance spectroscopy techniques. Photocatalytic reduction of nitrate in water and isopropanol/oxalic acid as hole scavengers are investigated in a batch reactor under UV illumination. The yield of urea increased notably when the catalysts were supported on zeolite. The Fe-titanate supported catalyst promotes the charge separation that contributes to an increase in selective formation of urea. The product formation is because of the high adsorption of in situ generated CO2 and NH3 over shape-selective property of the zeolite in the composite photocatalyst. The maximum yield of urea is found to be 18 ppm while 1% isopropanol containing solution over 10 wt% Fe-titanate/HZSM-5 photocatalyst was used.

Sullivan,Kilpatrick

, p. 1815,1820 (1945)

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Clark,Gaddy,Rist

, p. 1092 (1933)

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Oxyhalogen-sulfur chemistry: Kinetics and mechanism of oxidation of formamidine disulfide by acidic bromate

Madhiri, Nicholas,Olojo, Rotimi,Simoyi, Reuben H.

, p. 4149 - 4156 (2003)

The kinetics and mechanism of the oxidation of formamidine disulfide, FDS, a dimer and major metabolite of thiourea, by bromate have been studied in acidic media. In excess bromate conditions the reaction displays an induction period before formation of bromine. The stoichiometry of the reaction is: 7BrO3- + 3[(H2N(HN=)CS-]2 + 9H 2O → 6NH2CONH2 + 6SO4 2- + 7Br- + 12H- (A). In excess oxidant conditions, however, the bromide formed in reaction A reacts with bromate to give bromine and a final stoichiometry of: 14BrO3- + 5[(H2N(HN=)CS-]2 + 8H2O → 10NH 2CONH2 + 10SO42- + 7Br2 + 6H+ (B). The direct reaction of bromine and FDS was also studied and its stoichiometry is: 7Br2 + [(H2N(HN=)CS-] 2 + 10H2O → 2NH2CONH2 + 2SO42- + 14Br- + 18H+ (C). The overall rate of reaction A, as measured by the rate of consumption of FDS, is second order in acid concentrations, indicating the dominance of oxyhalogen kinetics which control the formation of the reactive species HBrO2 and HOBr. The reaction proceeds through an initial cleavage of the S-S bond to give the unstable sulfenic acids which are then rapidly oxidized through the sulfinic and sulfonic acids to give sulfate. The formation of bromine coincides with formation of sulfate because the cleavage of the C-S bond to give sulfate occurs at the sulfonic acid stage only. The mechanism derived is the same as that derived for the bromate-thiourea reaction, suggesting that FDS is an intermediate in the oxidation of thiourea to its oxo-acids as well as to sulfate.

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Palm,Calvin

, p. 2115 (1962)

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Schwander,Cordebard

, (1930)

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Oxyhalogen-Sulfur Chemistry: The Bromate-(Amininoimino)methanesulfinic Acid Reaction in Acidic Medium

Chinake, Cordelia R.,Simoyi, Reuben H.,Jonnalagadda, Sreekantha B.

, p. 545 - 550 (1994)

The reaction between (amnoimino)methanesulfinic acid, HO2SC(NH)NH2(AIMSA), and bromate has been studied in acidic medium.In excess AIMSA the stoichiometry of the reaction is 2BrO3- + 3AIMSA + 3H2O -> 3SO42- + 3CO(NH2)2 + 2Br- + 6H+, and in excess bromate the stoichiometry is 4BrO3- + 5AIMSA + 3H2O -> 5SO42- + 5CO(NH2)2 + 2Br2 + 6H+.Br2 is produced only when BrO3- is in stoichiometric excess over AIMSA.It is produced from the reaction of the product, Br-, with excess BrO3- after all the AIMSA has been consumed.The reaction has an initial induction period followed by formation of bromine.Although AIMSA is oxidized to SO42-, no SO42- formation is observed until Br2 production commences.The reaction is autocatalyzed by bromide.The reactive oxidizing species in solution are HOBr and Br2.Bromide enhances their formation from bromate.A simple eight-reaction mechanism is used to describe the reaction.The reaction commences through a direct reaction between BrO3- and AIMSA: BrO3+ + HO2SC(NH)NH2 + H+ -> HBrO2 + HO3SC(NH)NH2 with k = 2.5E-2M-2s-1.The rate-determining step is the standard BrO3- - Br- reaction which forms the reactive species HOBr:BrO3- + Br- + 2H+ -> HBrO2 + HOBr.A computer simulation analysis of the proposed mechanism gave good fit to the data.

Spectroscopic study of photo and thermal destruction of riboflavin

Astanov, Salikh,Sharipov, Mirzo Z.,Fayzullaev, Askar R.,Kurtaliev, Eldar N.,Nizomov, Negmat

, p. 133 - 138 (2014)

Influence of temperature and light irradiation on the spectroscopic properties of aqueous solutions of riboflavin was studied using linear dichroism method, absorption and fluorescence spectroscopy. It was established that in a wide temperature range 290-423 K there is a decline of absorbance and fluorescence ability, which is explained by thermodestruction of riboflavin. It is shown that the proportion of molecules, which have undergone degradation, are in the range of 4-28%, and depends on the concentration and quantity of temperature effects. Introduction of hydrochloric and sulfuric acids, as well as different metal ions leads to an increase in the photostability of riboflavin solutions by 2-2.5 times. The observed phenomena are explained by the formation protonation form of riboflavin and a complex between the metal ions and oxygen atoms of the carbonyl group of riboflavin, respectively.

Cattaway, F. D.

, p. 170 (1912)

Formation of adenine from CH3COONH4/NH 4HCO3-the probable prebiotic route for adenine

Singh, Palwinder,Singh, Amrinder

, p. 2525 - 2527 (2013)

Adenine was formed when an aqueous solution of CH3COONH 4/NH4HCO3 was subjected to mass spectrometer/refluxed for 72 h/heated in a closed vessel for a long time. Since these salts are sources of CO2 and NH3 and H2O is available from the reaction medium, adenine might get formed by the combination of CO2, H2O and NH3. The occurrence of this reaction in the gas phase as well as in the aqueous phase points towards the possibility of similar reactions during the primitive earth conditions.

Decomposition of Thiourea Dioxide under Aerobic and Anaerobic Conditions in an Aqueous Alkaline Solution

Egorova, E. V.,Nikitin, K. S.,Polenov, Yu. V.

, p. 2038 - 2041 (2020)

Abstract: The kinetics and mechanism of the decomposition of thiourea dioxide in an aqueous alkaline solution under aerobic and anaerobic conditions are established. It is discovered that along with the decomposition of thiourea dioxide molecules with C–S bond cleavage and the subsequent formation of sulfoxyl acid anions, there is a reversible stage of the formation of thiourea and peroxide anions. The rate constants of the indicated stages are determined via mathematical modeling using the experimental data.

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Franz,Applegath

, p. 3304 (1961)

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Inoue et al.

, p. 1339,1344 (1972)

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Jaffe

, p. 398 (1890)

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Degradation of 2-ketoarginine by guanidinobutyrase in arginine aminotransferase pathway of Brevibacterium helvolum.

Yorifuji,Kaneoke,Okazaki,Shimizu

, p. 512 - 513 (1995)

Guanidinobutyrase (EC 3.5.3.7) involved in the arginine oxygenase pathway of Brevibacterium helvolum IFO 12073 was found to catalyze also the hydrolysis of 2-ketoarginine (2-keto-5-guanidinovalerate) to 2-ketoornithine (2-keto-5-aminovalerate) and urea, the second step of the arginine aminotransferase pathway. No other enzyme that degraded 2-ketoarginine was found in cells grown on L-arginine. The enzyme hydrolyzed 2-ketoarginine with a relative rate of about 0.7% of that toward 4-guanidinobutyrate. The Km for 2-ketoarginine was 33 mM.

Davis, T. L.,Blanchard, K. C.

, p. 1806 - 1810 (1929)

Datta, R. L.,Choudhury, J. K.

, p. 2736 - 2740 (1916)

Catalytic Urea Synthesis from Ammonium Carbamate Using a Copper(II) Complex: A Combined Experimental and Theoretical Study

Dennis, Donovan,Ekmekci, Merve B.,Hanson, Danielle S.,Paripati, Amay,Wang, Yigui,Washburn, Erik,Xiao, Dequan,Zhou, Meng,Zhou, Xinrui

, p. 5573 - 5589 (2021/05/06)

The synthesis of urea fertilizer is currently the largest CO2 conversion process by volume in the industry. In this process, ammonium carbamate is an intermediate en route to urea formation. We determined that the tetraammineaquacopper(II) sulfate complex, [Cu(NH3)4(OH2)]SO4, catalyzed the formation of urea from ammonium carbamate in an aqueous solution. A urea yield of up to 18 ± 6% was obtained at 120 °C after 15 h and in a high-pressure metal reactor. No significant urea formed without the catalyst. The urea product was characterized by Fourier transform infrared (FT-IR), powder X-ray diffraction (PXRD), and quantitative 1H{13C} NMR analyses. The [Cu(NH3)4(OH2)]SO4 catalyst was then recovered at the end of the reaction in a 29% recovery yield, as verified by FT-IR, PXRD, and quantitative UV-vis spectroscopy. A precipitation method using CO2 was developed to recover and reuse 66 ± 3% of Cu(II). The catalysis mechanism was investigated by the density functional theory at the B3LYP/6-31G*? level with an SMD continuum solvent model. We determined that the [Cu(NH3)4]2+ complex is likely an effective catalyst structure. The study of the catalysis mechanism suggests that the coordinated carbamate with [Cu(NH3)4]2+ is likely the starting point of the catalyzed reaction, and carbamic acid can be involved as a transient intermediate that facilitates the removal of an OH group. Our work has paved the way for the rational design of catalysts for urea synthesis from the greenhouse gas CO2.

KV3 MODULATORS

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Page/Page column 49-50, (2021/08/14)

A compound of formula (I) and related aspects.

Catalytic hydration of cyanamides with phosphinous acid-based ruthenium(ii) and osmium(ii) complexes: scope and mechanistic insights

álvarez, Daniel,Cadierno, Victorio,Crochet, Pascale,González-Fernández, Rebeca,López, Ramón,Menéndez, M. Isabel

, p. 4084 - 4098 (2020/07/09)

The synthesis of a large variety of ureas R1R2NC(O)NH2 (R1 and R2 = alkyl, aryl or H; 26 examples) was successfully accomplished by hydration of the corresponding cyanamides R1R2NCN using the phosphinous acid-based complexes [MCl2(η6-p-cymene)(PMe2OH)] (M = Ru (1), Os (2)) as catalysts. The reactions proceeded cleanly under mild conditions (40-70 °C), in the absence of any additive, employing low metal loadings (1 molpercent) and water as the sole solvent. In almost all the cases, the osmium complex 2 featured a superior reactivity in comparison to that of its ruthenium counterpart 1. In addition, for both catalysts, the reaction rates observed for the hydration of the cyanamide substrates were remarkably faster than those involving classical aliphatic and aromatic nitriles. Computational studies allowed us to rationalize all these trends. Thus, the calculations indicated that the presence of a nitrogen atom directly linked to the CN bond depopulates electronically the nitrile carbon by inductive effect when coordinated to the metal center, thus favouring the intramolecular nucleophilic attack of the OH group of the phosphinous acid ligand to this carbon. On the other hand, the higher reactivity of Os vs. Ru seems to be related with the lower ring strain on the incipient metallacycle that starts to form in the transition state associated with this key step in the catalytic cycle. Indirect experimental evidence of the generation of the metallacyclic intermediates was obtained by studying the reactivity of [RuCl2(η6-p-cymene)(PMe2OH)] (1) towards dimethylcyanamide in methanol and ethanol. The reactions afforded compounds [RuCl(η6-p-cymene)(PMe2OR)(NCNMe2)][SbF6] (R = Me (5a), Et (5b)), resulting from the alcoholysis of the metallacycle, which could be characterized by single-crystal X-ray diffraction. This journal is