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Zajc, A, Romao MJ, Turk B, Huber R.  1996.  Crystallographic and fluorescence studies of ligand binding to N-carbamoylsarcosine amidohydrolase from Arthrobacter sp. Journal of Molecular Biology. 263:269-283., Number 2 AbstractWebsite
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Watson, C, Niks D, Hille R, Vieira M, Schoepp-Cothenet B, Marques AT, Romão MJ, Santos-Silva T, Santini JM.  2017.  Electron transfer through arsenite oxidase: Insights into Rieske interaction with cytochrome c. Biochimica et Biophysica Acta (BBA) - Bioenergetics. 1858:865-872., Number 10 AbstractWebsite

Arsenic is a widely distributed environmental toxin whose presence in drinking water poses a threat to >140 million people worldwide. The respiratory enzyme arsenite oxidase from various bacteria catalyses the oxidation of arsenite to arsenate and is being developed as a biosensor for arsenite. The arsenite oxidase from Rhizobium sp. str. NT-26 (a member of the Alphaproteobacteria) is a heterotetramer consisting of a large catalytic subunit (AioA), which contains a molybdenum centre and a 3Fe-4S cluster, and a small subunit (AioB) containing a Rieske 2Fe-2S cluster. Stopped-flow spectroscopy and isothermal titration calorimetry (ITC) have been used to better understand electron transfer through the redox-active centres of the enzyme, which is essential for biosensor development. Results show that oxidation of arsenite at the active site is extremely fast with a rate of >4000s−1 and reduction of the electron acceptor is rate-limiting. An AioB-F108A mutation results in increased activity with the artificial electron acceptor DCPIP and decreased activity with cytochrome c, which in the latter as demonstrated by ITC is not due to an effect on the protein-protein interaction but instead to an effect on electron transfer. These results provide further support that the AioB F108 is important in electron transfer between the Rieske subunit and cytochrome c and its absence in the arsenite oxidases from the Betaproteobacteria may explain the inability of these enzymes to use this electron acceptor.

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Voityuk, AA, Albert K, Kostlmeier S, Nasluzov VA, Neyman KM, Hof P, Huber R, Romao MJ, Rosch N.  1997.  Prediction of alternative structures of the molybdenum site in the xanthine oxidase-related aldehyde oxide reductase. Journal of the American Chemical Society. 119:3159-3160., Number 13 AbstractWebsite
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Voityuk, AA, Albert K, Romao MJ, Huber R, Rosch N.  1998.  Substrate oxidation in the active site of xanthine oxidase and related enzymes. A model density functional study. Inorganic Chemistry. 37:176-180., Number 2 AbstractWebsite
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Vilela-Alves, G, Manuel RR, Viegas A, Carpentier P, Biaso F, Guigliarelli B, Pereira IAC, Romão MJ, Mota C.  2024.  Substrate-dependent oxidative inactivation of a W-dependent formate dehydrogenase involving selenocysteine displacement. bioRxiv. : Cold Spring Harbor Laboratory AbstractWebsite

Metal-dependent formate dehydrogenases are very promising targets for enzyme optimization and design of bio-inspired catalysts for CO2 reduction, towards novel strategies for climate change mitigation. For effective application of these enzymes, the catalytic mechanism must be fully understood, and the molecular determinants clarified. Despite numerous studies, several doubts persist, namely regarding the role played by the possible dissociation of the SeCys ligand from the Mo/W active site. Additionally, the O2 sensitivity of these enzymes must also be understood as it poses an important obstacle for biotechnological applications. Here we present a combined biochemical, spectroscopic, and structural characterization of Desulfovibrio vulgaris FdhAB (DvFdhAB) when exposed to oxygen in the presence of a substrate (formate or CO2). This study reveals that O2 inactivation is promoted by the presence of either substrate and involves forming a new species in the active site, captured in the crystal structures, where the SeCys ligand is displaced from tungsten coordination and replaced by a dioxygen or peroxide molecule. This new form was reproducibly obtained and supports the conclusion that, although W-DvFdhAB can catalyze the oxidation of formate in the presence of oxygen for some minutes, it gets irreversibly inactivated after prolonged O2 exposure in the presence of either substrate. These results reveal that oxidative inactivation does not require reduction of the metal, as widely assumed, as it can also occur in the oxidized state in the presence of CO2.Competing Interest StatementThe authors have declared no competing interest.AORAldehyde Oxido-reductaseDTTDithiothreitolDvDesulfovibrio vulgarisEPRElectron Paramagnetic ResonanceFdhFormate dehydrogenaseHPHigh PressureMGDMolybdopterin Guanine DinucleotidesNDNew dropROSReactive Oxygen SpeciesSODSuperoxide dismutaseTSAThermal Shift Assay

Vilela-Alves, G, Manuel RR, Oliveira AR, Pereira IC, Romão MJ, Mota C.  2023.  Tracking W-Formate Dehydrogenase Structural Changes During Catalysis and Enzyme Reoxidation. International Journal of Molecular Sciences. 24, Number 1 AbstractWebsite

Metal-dependent formate dehydrogenases (Fdh) catalyze the reversible conversion of CO2 to formate, with unrivalled efficiency and selectivity. However, the key catalytic aspects of these enzymes remain unknown, preventing us from fully benefiting from their capabilities in terms of biotechnological applications. Here, we report a time-resolved characterization by X-ray crystallography of the Desulfovibrio vulgaris Hildenborough SeCys/W-Fdh during formate oxidation. The results allowed us to model five different intermediate structures and to chronologically map the changes occurring during enzyme reduction. Formate molecules were assigned for the first time to populate the catalytic pocket of a Fdh. Finally, the redox reversibility of DvFdhAB in crystals was confirmed by reduction and reoxidation structural studies.

Viegas, A, Bras NF, Cerqueira NMFSA, Fernandes PA, Prates JAM, Fontes CMGA, Bruix M, Romao MJ, Carvalho AL, Ramos MJ, Macedo AL, Cabrita EJ.  2008.  Molecular determinants of ligand specificity in family 11 carbohydrate binding modules - an NMR, X-ray crystallography and computational chemistry approach. Febs Journal. 275:2524-2535., Number 10 AbstractWebsite
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Viegas, A, Sardinha J, Freire F, Duarte DF, Carvalho AL, Fontes CMGA, Romao MJ, Macedo AL, Cabrita EJ.  2013.  Solution structure, dynamics and binding studies of a family 11 carbohydrate-binding module from Clostridium thermocellum (CtCBM11). Biochemical Journal. 451:289-300. AbstractWebsite
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Vidossich, P, Castañeda Moreno LE, Mota C, de Sanctis D, Miscione GP, De Vivo M.  2020.  Functional Implications of Second-Shell Basic Residues for dUTPase DR2231 Enzymatic Specificity, 2020. ACS CatalysisACS Catalysis. 10(23):13825-13833.: American Chemical Society AbstractWebsite

Nucleotide-processing enzymes are key players in biological processes. They often operate through high substrate specificity for catalysis. How such specificity is achieved is unclear. Here, we dealt with this question by investigating all-α dimeric deoxyuridine triphosphate nucleotidohydrolases (dUTPases). Typically, these dUTPases hydrolyze either dUTP or deoxyuridine diphosphate (dUDP) substrates. However, the dUTPase enzyme DR2231 from Deinococcus radiodurans selectively hydrolyzes dUTP only, and not dUDP. By means of extended classical molecular dynamics simulations and quantum chemical calculations, we show that DR2231 achieves this specificity for dUTP via second-shell basic residues that, together with the two catalytic magnesium ions, contribute to properly orienting the γ-phosphate of dUTP in a prereactive state. This allows a nucleophilic water to be correctly placed and activated in order to perform substrate hydrolysis. We show that this enzymatic mechanism is not viable when dUDP is bound to DR2231. Importantly, in several other dUTPases capable of hydrolyzing either dUTP or dUDP, we detected that active site second-shell basic residues are more in number, anchoring the β-phosphate of the nucleotide substrate too, in contrast to what is observed in DR2231. Thus, strategically located basic second-shell residues mediate precise reactant positioning at the catalytic site, determining substrate specificity in dUTPases and possibly in other structurally similar nucleotide-processing metalloenzymes.Nucleotide-processing enzymes are key players in biological processes. They often operate through high substrate specificity for catalysis. How such specificity is achieved is unclear. Here, we dealt with this question by investigating all-α dimeric deoxyuridine triphosphate nucleotidohydrolases (dUTPases). Typically, these dUTPases hydrolyze either dUTP or deoxyuridine diphosphate (dUDP) substrates. However, the dUTPase enzyme DR2231 from Deinococcus radiodurans selectively hydrolyzes dUTP only, and not dUDP. By means of extended classical molecular dynamics simulations and quantum chemical calculations, we show that DR2231 achieves this specificity for dUTP via second-shell basic residues that, together with the two catalytic magnesium ions, contribute to properly orienting the γ-phosphate of dUTP in a prereactive state. This allows a nucleophilic water to be correctly placed and activated in order to perform substrate hydrolysis. We show that this enzymatic mechanism is not viable when dUDP is bound to DR2231. Importantly, in several other dUTPases capable of hydrolyzing either dUTP or dUDP, we detected that active site second-shell basic residues are more in number, anchoring the β-phosphate of the nucleotide substrate too, in contrast to what is observed in DR2231. Thus, strategically located basic second-shell residues mediate precise reactant positioning at the catalytic site, determining substrate specificity in dUTPases and possibly in other structurally similar nucleotide-processing metalloenzymes.

Vidinha, P, Lourenco NMT, Pinheiro C, Bras AR, Carvalho T, Santos-Silva T, Mukhopadhyay A, Romao MJ, Parola J, Dionisio M, Cabral JMS, Afonso CAM, Barreiros S.  2008.  Ion jelly: a tailor-made conducting material for smart electrochemical devices. Chemical Communications. :5842-5844., Number 44 AbstractWebsite
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Viciosa, MT, Correia NT, Salmeron Sanchez M, Carvalho AL, Romao MJ, Gomez Ribelles JL, Dionisio M.  2009.  Real-Time Monitoring of Molecular Dynamics of Ethylene Glycol Dimethacrylate Glass Former. Journal of Physical Chemistry B. 113:14209-14217., Number 43 AbstractWebsite
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Verma, AK, Goyal A, Freire F, Bule P, Venditto I, Bras JLA, Santos H, Cardoso V, Bonifacio C, Thompson A, Romao MJ, Prates JAM, Ferreira LMA, Fontes CMGA, Najmudin S.  2013.  Overexpression, crystallization and preliminary X-ray crystallographic analysis of glucuronoxylan xylanohydrolase (Xyn30A) from Clostridium thermocellum. Acta Crystallographica Section F-Structural Biology and Crystallization Communications. 69:1440-1442. AbstractWebsite
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Varela, PF, Romero A, Sanz L, Romao MJ, Topfer-Petersen E, Calvete JJ.  1997.  The 2.4 angstrom resolution crystal structure of boar seminal plasma PSP-I/PSP-II: a zona pellucida-binding glycoprotein heterodimer of the spermadhesin family built by a CUB domain architecture. Journal of Molecular Biology. 274:635-649., Number 4 AbstractWebsite
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Trovão, F, Correia VG, Lourenço FM, Ribeiro DO, Carvalho AL, Palma AS, Pinheiro BA.  2023.  The structure of a Bacteroides thetaiotamicron carbohydrate-binding module provides new insight into the recognition of complex pectic polysaccharides by the human microbiome, 2023. :100084. AbstractWebsite

TheBacteroides thetaiotaomicronhas developed a consortium of enzymes capable of overcoming steric constraints and degrading, in a sequential manner, the complex rhamnogalacturonan II (RG-II) polysaccharide. BT0996 protein acts in the initial stages of the RGII depolymerisation, where its two catalytic modules remove the terminal monosaccharides from RG-II side chains A and B. BT0996 is modular and has three putative carbohydrate-binding modules (CBMs) for which the roles in the RG-II degradation are unknown. Here, we present the characterisation of themoduleat the C-terminal domain, which we designated BT0996C. The high-resolution structure obtained by X-ray crystallography reveals that the protein displays a typical β-sandwich fold with structural similarity to CBMs assigned to families 6 and 35. The distinctive features are: 1) the presence of several charged residues at the BT0996-C surface creating a large, broad positive lysine-rich patch that encompasses the putative binding site; and 2) the absence of the highly conserved binding-site signatures observed in CBMs from families 6 and 35, such as region A tryptophan and region C asparagine. These findings hint at a binding mode of BT0996-C not yet observed in its homologues. In line with this, carbohydrate microarrays and microscale thermophoresis show the ability of BT0996-C to bind α1-4-linked polygalacturonic acid, and that electrostatic interactions are essential for the recognition of the anionic polysaccharide. The results support the hypothesis that BT0996-C may have evolved to potentiate the action of BT0996 catalytic modules on the complex structure of RG-II by binding to the polygalacturonic acid backbone sequence.

Trincao, J, Silva MS, Barata L, Bonifacio C, Carvalho S, Tomas AM, Ferreira AEN, Cordeiro C, Freire AP, Romao MJ.  2006.  Purification, crystallization and preliminary X-ray diffraction analysis of the glyoxalase II from Leishmania infantum. Acta Crystallographica Section F-Structural Biology and Crystallization Communications. 62:805-807. AbstractWebsite
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Thoenes, U, Flores OL, Neves A, Devreese B, Van Beeumen JJ, Huber R, Romao MJ, Legall J, Moura JJG, Rodriguespousada C.  1994.  MOLECULAR-CLONING AND SEQUENCE-ANALYSIS OF THE GENE OF THE MOLYBDENUM-CONTAINING ALDEHYDE OXIDOREDUCTASE OF DESULFOVIBRIO-GIGAS - THE DEDUCED AMINO-ACID-SEQUENCE SHOWS SIMILARITY TO XANTHINE DEHYDROGENASE. European Journal of Biochemistry. 220:901-910., Number 3 AbstractWebsite
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Thapper, A, Boer DR, Brondino CD, Moura JJG, Romao MJ.  2007.  Correlating EPR and X-ray structural analysis of arsenite-inhibited forms of aldehyde oxidoreductase. Journal of Biological Inorganic Chemistry. 12:353-366., Number 3 AbstractWebsite
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Terao, M, Romão MJ, Leimkühler S, Bolis M, Fratelli M, Coelho C, Santos-Silva T, Garattini E.  2016.  Structure and function of mammalian aldehyde oxidases. Archives of Toxicology. 90:753–780., Number 4 AbstractWebsite

Mammalian aldehyde oxidases (AOXs; EC1.2.3.1) are a group of conserved proteins belonging to the family of molybdo-flavoenzymes along with the structurally related xanthine dehydrogenase enzyme. AOXs are characterized by broad substrate specificity, oxidizing not only aromatic and aliphatic aldehydes into the corresponding carboxylic acids, but also hydroxylating a series of heteroaromatic rings. The number of AOX isoenzymes expressed in different vertebrate species is variable. The two extremes are represented by humans, which express a single enzyme (AOX1) in many organs and mice or rats which are characterized by tissue-specific expression of four isoforms (AOX1, AOX2, AOX3, and AOX4). In vertebrates each AOX isoenzyme is the product of a distinct gene consisting of 35 highly conserved exons. The extant species-specific complement of AOX isoenzymes is the result of a complex evolutionary process consisting of a first phase characterized by a series of asynchronous gene duplications and a second phase where the pseudogenization and gene deletion events prevail. In the last few years remarkable advances in the elucidation of the structural characteristics and the catalytic mechanisms of mammalian AOXs have been made thanks to the successful crystallization of human AOX1 and mouse AOX3. Much less is known about the physiological function and physiological substrates of human AOX1 and other mammalian AOX isoenzymes, although the importance of these proteins in xenobiotic metabolism is fairly well established and their relevance in drug development is increasing. This review article provides an overview and a discussion of the current knowledge on mammalian AOX.

Terao, M, Garattini E, Romão MJ, Leimkühler S.  2020.  Evolution, expression, and substrate specificities of aldehyde oxidase enzymes in eukaryotes, 2020. Journal of Biological ChemistryJournal of Biological Chemistry. 295(16):5377-5389.: Elsevier AbstractWebsite

Aldehyde oxidases (AOXs) are a small group of enzymes belonging to the larger family of molybdo-flavoenzymes, along with the well-characterized xanthine oxidoreductase. The two major types of reactions that are catalyzed by AOXs are the hydroxylation of heterocycles and the oxidation of aldehydes to their corresponding carboxylic acids. Different animal species have different complements of AOX genes. The two extremes are represented in humans and rodents; whereas the human genome contains a single active gene (AOX1), those of rodents, such as mice, are endowed with four genes (Aox1-4), clustering on the same chromosome, each encoding a functionally distinct AOX enzyme. It still remains enigmatic why some species have numerous AOX enzymes, whereas others harbor only one functional enzyme. At present, little is known about the physiological relevance of AOX enzymes in humans and their additional forms in other mammals. These enzymes are expressed in the liver and play an important role in the metabolisms of drugs and other xenobiotics. In this review, we discuss the expression, tissue-specific roles, and substrate specificities of the different mammalian AOX enzymes and highlight insights into their physiological roles.Aldehyde oxidases (AOXs) are a small group of enzymes belonging to the larger family of molybdo-flavoenzymes, along with the well-characterized xanthine oxidoreductase. The two major types of reactions that are catalyzed by AOXs are the hydroxylation of heterocycles and the oxidation of aldehydes to their corresponding carboxylic acids. Different animal species have different complements of AOX genes. The two extremes are represented in humans and rodents; whereas the human genome contains a single active gene (AOX1), those of rodents, such as mice, are endowed with four genes (Aox1-4), clustering on the same chromosome, each encoding a functionally distinct AOX enzyme. It still remains enigmatic why some species have numerous AOX enzymes, whereas others harbor only one functional enzyme. At present, little is known about the physiological relevance of AOX enzymes in humans and their additional forms in other mammals. These enzymes are expressed in the liver and play an important role in the metabolisms of drugs and other xenobiotics. In this review, we discuss the expression, tissue-specific roles, and substrate specificities of the different mammalian AOX enzymes and highlight insights into their physiological roles.

Teixeira, S, Dias JM, Carvalho AL, Bourenkov G, Bartunik H, Almendra MJ, Moura I, Moura JJG, Romao MJ.  1999.  Crystallographic studies on a tungsten-containning formate dehydrogenase from Desulfovibrio gigas. Journal of Inorganic Biochemistry. 74:89-89., Number 1-4 AbstractWebsite
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Silva, JM, Cerofolini L, Carvalho AL, Ravera E, Fragai M, Parigi G, Macedo AL, Geraldes CFGC, Luchinat C.  2023.  Elucidating the concentration-dependent effects of thiocyanate binding to carbonic anhydrase, 2023. 244:112222. AbstractWebsite

Many proteins naturally carry metal centers, with a large share of them being in the active sites of several enzymes. Paramagnetic effects are a powerful source of structural information and, therefore, if the native metal is paramagnetic, or it can be functionally substituted with a paramagnetic one, paramagnetic effects can be used to study the metal sites, as well as the overall structure of the protein. One notable example is cobalt(II) substitution for zinc(II) in carbonic anhydrase. In this manuscript we investigate the effects of sodium thiocyanate on the chemical environment of the metal ion of the human carbonic anhydrase II. The electron paramagnetic resonance (EPR) titration of the cobalt(II) protein with thiocyanate shows that the EPR spectrum changes from A-type to C-type on passing from 1:1 to 1:1000-fold ligand excess. This indicates the occurrence of a change in the electronic structure, which may reflect a sizable change in the metal coordination environment in turn caused by a modification of the frozen solvent glass. However, paramagnetic nuclear magnetic resonance (NMR) data indicate that the metal coordination cage remains unperturbed even in 1:1000-fold ligand excess. This result proves that the C-type EPR spectrum observed at large ligand concentration should be ascribed to the low temperature at which EPR measurements are performed, which impacts on the structure of the protein when it is destabilized by a high concentration of a chaotropic agent.

Seixas, JD, Mukhopadhyay A, Santos-Silva T, Otterbein LE, Gallo DJ, Rodrigues SS, Guerreiro BH, Goncalves AML, Penacho N, Marques AR, Coelho AC, Reis PM, Romao MJ, Romao CC.  2013.  Characterization of a versatile organometallic pro-drug (CORM) for experimental CO based therapeutics. Dalton Transactions. 42:5985-5998., Number 17 AbstractWebsite
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Seixas, JD, Santos MFA, Mukhopadhyay A, Coelho AC, Reis PM, Veiros LF, Marques AR, Penacho N, Goncalves AML, Romao MJ, Bernardes GJL, Santos-Silva T, Romao CC.  2015.  A contribution to the rational design of Ru(CO)(3)Cl2L complexes for in vivo delivery of CO. Dalton Transactions. 44:5058-5075., Number 11 AbstractWebsite

A few ruthenium based metal carbonyl complexes, e.g. CORM-2 and CORM-3, have therapeutic activity attributed to their ability to deliver CO to biological targets. In this work, a series of related complexes with the formula [Ru(CO)(3)Cl2L] (L = DMSO (3), L-H3CSO(CH2)(2)CH(NH2)CO2H) (6a); D,L-H3CSO(CH2)(2)CH-(NH2)CO2H (6b); 3-NC5H4(CH2)(2)SO3.Na (7); 4-NC5H4(CH2)(2)SO3Na (8); PTA (9); DAPTA (10); H3CS-(CH2)(2)CH(OH) CO2H (11); CNCMe2CO2Me (12); CNCMeEtCO2Me (13); CN(c-C3H4)CO2Et) (14)) were designed, synthesized and studied. The effects of L on their stability, CO release profile, cytotoxicity and anti-inflammatory properties are described. The stability in aqueous solution depends on the nature of L as shown using HPLC and LC-MS studies. The isocyanide derivatives are the least stable complexes, and the S-bound methionine oxide derivative is the more stable one. The complexes do not release CO gas to the headspace, but release CO2 instead. X-ray diffraction of crystals of the model protein Hen Egg White Lysozyme soaked with 6b (4UWN) and 8 (4UWV) shows the addition of Ru-II(CO)(H2O)(4) at the His15 binding site. Soakings with 7 (4UWU) produced the metallacarboxylate [Ru(COOH)(CO)(H2O)(3)](+) bound to the His15 site. The aqueous chemistry of these complexes is governed by the water-gas shift reaction initiated with the nucleophilic attack of HO- on coordinated CO. DFT calculations show this addition to be essentially barrierless. The complexes have low cytotoxicity and low hemolytic indices. Following i.v. administration of CORM-3, the in vivo bio-distribution of CO differs from that obtained with CO inhalation or with heme oxygenase stimulation. A mechanism for CO transport and delivery from these complexes is proposed.

Santos-Silva, T, Dias JM, Dolla A, Durand M-C, Goncalves LL, Lampreia J, Moura I, Romao MJ.  2007.  Crystal structure of the 16 heme cytochrome from Desulfovibrio gigas: A glycosylated protein in a sulphate-reducing bacterium. Journal of Molecular Biology. 370:659-673., Number 4 AbstractWebsite
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Santos-Silva, T, Mukhopadhyay A, Seixas JD, Bernardes GJL, Romao CC, Romao MJ.  2011.  Towards Improved Therapeutic CORMs: Understanding the Reactivity of CORM-3 with Proteins. Current Medicinal Chemistry. 18:3361-3366., Number 22 AbstractWebsite
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