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1.
Amino Acids ; 52(5): 811-821, 2020 May.
Artigo em Inglês | MEDLINE | ID: mdl-32372392

RESUMO

The kinetics of oligopeptides formation in the flow systems glycine-sodium trimetaphosphate-imidazole/N-methylimidazole at thermocyclic regime has been investigated by HPLC and 31P NMR methods in the ranges of temperature from 45 to 90 °C and pH from 8.5 to 11.5. Detailed reaction mechanisms have been proposed and justified by quantum chemical calculations using DFT method at the CAM-B3LYP/TZVP level with accounting solvent effect by the C-PCM model. A new imidazole catalysis mechanism by which imidazole reacts with cyclic N,O-phosphoryl glycine giving N-imidazolyl-O-glycyl phosphate as a key intermediate was proposed and validated. It is emphasized that while in the absence of imidazoles, prebiotic activation of amino acids occurs at the N-terminus, in the presence of imidazoles it shifts to the O-terminus. This means that in the peptide elongation N-imidazolyl-O-aminoacyl phosphates play in prebiotic systems the outstanding role similar to that of aminoacyl adenylates formed at the ATP and aminoacyl-tRNA synthetases presence in biosystems. The new crucial role of imidazoles in prebiotic evolution has been noticed. The systems used and modes of their conversion can be good models for prebiotic peptide syntheses in a flow thermocyclic regime.


Assuntos
Glicina/química , Imidazóis/química , Oligopeptídeos/síntese química , Biossíntese Peptídica , Polifosfatos/química , Catálise , Concentração de Íons de Hidrogênio , Cinética
2.
Orig Life Evol Biosph ; 49(1-2): 1-18, 2019 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-31004318

RESUMO

Syntheses under shock in nitrogen bubbled samples of the water - formamide - bicarbonate - sodium hydroxide system at pH 8.63, 9.46 and 10.44 were performed in the stainless steel preservation capsules. The maximum temperature and pressure in the capsules reached 545 K and 12.5 GPa respectively. Using the LC-MS-MS analysis, the 21 synthesis products have been identified, including amines and polyamines, carboxamide, acetamide and urea derivatives, compounds containing aniline, pyrrolidine, pyrrole, imidazole, as well as alcohol groups. It was found that the Fischer-Tropsch-type syntheses with catalysis on the surface of the stainless steel of the conservation capsule associated with the adsorbed hydrogen cyanide reactions and transamidation processes play the main role in the shock syntheses. Formation reactions of all the above-mentioned compounds have been suggested. It was proposed that hydrogen cyanide, ammonia, isocyanic acid, aminonitrile, aminoacetonitrile, as well as adsorbed species H(a), CH(a), CH2(a), CHOH(a), NH2(a) and H2CNH(a) are especially important for the formation of the products. A reduction reaction of adsorbed bicarbonate with hydrogen to formaldehyde has been first postulated. In the studied system also classical reactions take place - Wöhler's synthesis of urea and Butlerov's synthesis of methenamine. It was suggest that material of meteorites may be an effective catalyst in the Fischer-Tropsch-type syntheses at falling of the iron-nickel meteorites in the water - formamide regions on the early Earth. It was concluded that life could have originated due to the impact of meteorites on alkaline water-formamide lakes located near volcanoes on the early Earth.


Assuntos
Bicarbonatos/química , Evolução Química , Formamidas/química , Origem da Vida , Compostos de Potássio/química , Hidróxido de Sódio/química , Cromatografia Líquida , Planeta Terra , Concentração de Íons de Hidrogênio , Meteoroides , Espectrometria de Massas em Tandem , Água/química
3.
Acta Crystallogr E Crystallogr Commun ; 74(Pt 7): 981-986, 2018 Jul 01.
Artigo em Inglês | MEDLINE | ID: mdl-30002899

RESUMO

Crystals of four new copper(II) complexes have been grown from copper(II) acetate/chloride-1-ethyl-3-methyl-imidazolium acetate/chloride-water systems and characterized by X-ray analysis. The first complex, bis-(1-ethyl-3-methyl-imidazolium) tetra-µ-acetato-bis[chloridocuprate(II)], [Emim]2[Cu2(C2H3O2)4Cl2] (1) (Emim is 1-ethyl-3-methyl-imidazolium, C6H11N2), contains [Cu2(C2H3O2)4Cl2]2- coordination anions with a paddle-wheel structure and ionic liquid cations. Two of the synthesized complexes are one-dimensional polymers, namely catena-poly[1-ethyl-3-methyl-imidazolium [[tetra-µ-acetato-dicuprate(II)]-µ-chlorido] monohydrate], {[Emim][Cu2(C2H3O2)4Cl]·H2O} n (2), and catena-poly[1-ethyl-3-methyl-imidazolium [[tetra-µ-acetato-dicuprate(II)]-µ-acetato]], {[Emim][Cu2(C2H3O2)5]} n (3). In these compounds, the Cu2(C2H3O2)4 units with a paddle-wheel structure are connected to each other through chloride (in 2) or acetate (in 3) anions to form parallel chains, between which cations of ionic liquid are situated. The last compound, bis-(1-ethyl-3-methyl-imidazolium) tetra-µ-acetato-bis[aquacopper(II)] tetra-µ-acetato-bis[acetatocuprate(II)] dihydrate, [Emim]2[Cu2(C2H3O2)4(H2O)2][Cu2(C2H3O2)6]·2H2O (4), contains two different binuclear coordination units (neutral and anionic), connected through hydrogen bonds between water mol-ecules and acetate ions.

4.
J Comput Chem ; 39(14): 821-826, 2018 05 30.
Artigo em Inglês | MEDLINE | ID: mdl-29283453

RESUMO

Hydration of the copper(II) bis-complexes with glycine, serine, lysine, and aspartic acid was studied by DFT and MD simulation methods. The distances between copper(II) and water molecules in the 1st and 2nd coordination shells, the average number of water molecules and their mean residence times in the hydration shells were calculated. Good agreement was observed between the values obtained and those found by DFT and NMR relaxation methods. Influence of the functional groups of the ligands and the cis-trans isomerism of the complexes on the structural and dynamical parameters of the hydration shells was displayed and explained. Analysis of the MD trajectories reveals the competition for a copper(II) axial position between water molecules or water molecules and the functional chain groups of the ligands and confirms the suggestion on the pentacoordination of copper(II) in such complexes. MD simulations show that only one axial position of Cu(II) is basically occupied at each time step while in average the coordination number more than 5 is observed. © 2017 Wiley Periodicals, Inc.


Assuntos
Aminoácidos/química , Cobre/química , Compostos Organometálicos/química , Água/química , Teoria da Densidade Funcional , Simulação de Dinâmica Molecular , Estereoisomerismo
5.
Inorg Chem ; 54(20): 9777-84, 2015 Oct 19.
Artigo em Inglês | MEDLINE | ID: mdl-26440723

RESUMO

EPR, NMR relaxation methods, and DFT calculations were jointly used to investigate the structural and dynamical characteristics of solvation shells of copper(II) complexes with iminodiacetic acid, glycylglycine, and glycyglycylglycine in comparison with the copper(II) bis-glycinate studied previously. A strong trans influence of deprotonated peptide nitrogen was revealed in EPR spectra parameters of copper(II) complexes with oligopeptides. With models of the experimental NMRD data and literature X-ray structural information, it was suggested that only one water molecule coordinates in axial position of copper(II) complexes with glycine and di- and triglycine (Cu(Gly)2, Cu(GGH(-1)), and Cu(GGGH(-2))(-)), and the copper ion in these complexes is pentacoordinated, while in the iminodiacetate complex, Cu(IDA), both apical positions can be occupied by solute molecules. The obtained structural results were confirmed by DFT calculations of structures of studied compounds using different functionals and basis sets. It was shown that the donor ability of equatorial ligands and trans influence have an effect on the characteristics of the axial water bond. With increasing donor strength of equatorial ligands, pentacoordination of copper(II) complexes in water solutions becomes more preferable.

6.
Phys Chem Chem Phys ; 16(20): 9411-21, 2014 May 28.
Artigo em Inglês | MEDLINE | ID: mdl-24722622

RESUMO

Structural features and dynamical behaviour of the copper(ii) bis-complexes with glycine, d-alanine, d-valine, l-serine, l-aspartic acid, l-glutamic acid, l-lysine, l-proline, and sarcosine were studied by combined EPR and NMR relaxation methods. The cis and trans isomers were unambiguously assigned and characterized by EPR data. It was found that addition of a salt background has an influence on the cis-trans isomer equilibrium in favour of the formation of the cis isomer. By comparison of NMRD, DFT computations, and structural data it was shown that only one water molecule is coordinated in the axial position of these complexes. The increased exchange rates of this molecule found for Cu(l-Asp)2(2-), Cu(l-Glu)2(2-), Cu(l-LysH)2(2+), and Cu(l-Pro)2 were attributed to its pushing out by side chain groups of the ligands. By simulation of NMRD profiles an increase of lifetimes of the copper(ii) 2nd coordination sphere water molecules was revealed in the presence of additional carboxylic, alcoholic, or ammonium groups of the ligands, as well as the pyrrolidine ring of proline. The very short lifetimes of the 2nd coordination sphere water molecules (4-13 ps at 298 K) were explained in terms of the Frank-Wen structural model by the existence of cavities which draw in quickly enough water molecules from the 2nd coordination sphere.


Assuntos
Aminoácidos/química , Cobre/química , Compostos Organometálicos/química , Espectroscopia de Ressonância de Spin Eletrônica , Espectroscopia de Ressonância Magnética , Soluções
7.
Dalton Trans ; 43(2): 799-805, 2014 Jan 14.
Artigo em Inglês | MEDLINE | ID: mdl-24154681

RESUMO

Ionic liquid (1-ethyl-3-methylimidazolium acetate, [C2C1im][AcO])-copper(ii) diacetate monohydrate-water-air (O2) systems have been investigated by (13)C NMR, EPR, spectrophotometry, HPLC, and synthetic chemistry methods at different temperatures. The C-H bond activation of [C2C1im](+) with the formation of the unusual dication 1,1'-diethyl-3,3'-dimethyl-2,2'-biimidazolium ([(C2C1im)2](2+)) at 50 °C and 1-ethyl-3-methyl-1H-imidazol-2(3H)-one (C2C1imO) at 50-85 °C was revealed. Two new complexes with the above compounds, [(C2C1im)2][Cu(AcO)4] and Cu2(AcO)4(C2C1imO)2, were isolated from the systems and characterized by X-ray structural analysis. Catalytic cycles with the participation of copper(ii) acetate and dioxygen and the production of [(C2C1im)2](2+) and C2C1imO have been proposed. The catalysis presumably includes the formation of the Cu(II)(O2)Cu(II) active centre with µ-η(2):η(2)-peroxide bridging in analogy with tyrosinase and catechol oxidase activity.


Assuntos
Acetatos/química , Ar , Cobre/química , Imidazóis/química , Oxigênio/química , Água/química , Carbono/química , Hidrogênio/química , Modelos Moleculares , Conformação Molecular , Oxirredução , Temperatura
8.
Dalton Trans ; 41(4): 1216-28, 2012 Jan 28.
Artigo em Inglês | MEDLINE | ID: mdl-22120906

RESUMO

The formation of copper(II) complexes with L- and DL-histidine (HisH) has been studied by means of pH-potentiometry and spectrophotometry over a wide range of pH (2-14), ligand-to-metal ratio (1 : 1-15 : 1), and temperature (15-55 °C) in aqueous solutions with 1.0 mol dm(-3) KNO(3) as background. Formation constants and spectral characteristics of 13 complex types were found. Fine stereoselective effects have been detected with preferential coordination of two ligands with identical configuration in Cu(His)(HisH)(+) and opposite configuration in Cu(His)(2). The stereoselective effect for Cu(His)(HisH)(+) is explained by hydrogen bond formation between the carboxyl and imidazolyl groups of neighboring ligands at cis-arrangement of amino groups (3N(eq)-form). The opposite sign of stereoselective effect for Cu(His)(2) is derived from favourable axial coordination of the imidazole group in meso-form with cis-structure (3N(eq)N(ax)-form). A significant tetrahedral distortion was revealed for the first time in the prevalent cis-isomer of the Cu(L-His)(2) 4N(eq)-form. These findings were confirmed by EPR data and DFT computations at the B3LYP/TZVP level. The prevalence of cis-isomers for these complexes has been assigned to the rather strong trans effect of the amino groups. The structures of other detected complexes are briefly discussed on the basis of spectroscopic data. Chemical exchange reactions in the copper(II)-L/DL-hishidine systems have been investigated by the NMR relaxation of water protons. A unique proton exchange reaction with short-term proton dissociation from the coordinated imidazolyl group catalyzed by hydroxide ion was characterised for the first time. The discovered enantioselective effects in the ligand exchange reactions between Cu(His)(2) and HisH or His(-) species were attributed to the associative substitution mechanism.


Assuntos
Cobre/química , Histidina/química , Compostos Organometálicos/química , Concentração de Íons de Hidrogênio , Ligantes , Modelos Moleculares , Conformação Molecular , Compostos Organometálicos/síntese química , Análise Espectral , Estereoisomerismo , Especificidade por Substrato , Temperatura , Água/química
9.
J Inorg Biochem ; 99(6): 1335-46, 2005 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-15917088

RESUMO

Formation constants and structures of copper(II) complexes with oxidized glutathione (L) have been determined by computer modelling of spectrophotometric and NMR relaxation measurements data over a wide range of pH (1-13) and metal and ligand concentrations in aqueous KNO(3) (1M) at 298K. Among 11 found complexes, four forms were characterized for the first time. Based on a comparison of thermodynamic, relaxation, and optical and EPR spectroscopy parameters the structural conclusions were made. In particular, the CuLH(2) and CuLH(-) complexes both contain two isomers which are similar to mono- and bis-aminoacid copper(II) complexes. In the Cu(2)L and Cu(3)L(2)(2-) species one of the copper atoms is bound only with the carboxylate or carbonyl groups and the others are coordinated similarly to aminoacid chelates. Along with the last, in Cu(2)LH(-2)(2-) two bridging OH(-) groups in one isomer or two chelate rings including deprotonated peptide nitrogen and glycinyl carboxylate oxygen in another are also present. In Cu(3)L(2)H(-4)(6-) the mixed variant of coordination between CuL(2-) (CuN(2)O(2)) and Cu(2)LH(-4)(4-)(CuN(3)O) is realized. The structures of polynuclear complexes have been optimized in density functional theory computations. Rate constants of ligand exchange reactions of Cu(LH)(2)(4-) and CuL(2)(6-) with participation of the LH(3-) and L(4-) forms were determined for the first time. Factors determining rates of these processes have been revealed and their proceeding by associative substitution mechanism shown.

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