463-79-6Relevant articles and documents
Carbonic anhydrase activity of dinuclear CuII complexes with patellamide model ligands
Comba, Peter,Gahan, Lawrence R.,Hanson, Graeme R.,Maeder, Marcel,Westphal, Michael
, p. 3144 - 3152 (2014)
The dicopper(ii) complexes of six pseudo-octapeptides, synthetic analogues of ascidiacyclamide and the patellamides, found in ascidians of the Pacific and Indian Oceans, are shown to be efficient carbonic anhydrase model complexes with kcat up to 7.3 × 103 s-1 (uncatalyzed: 3.7 × 10-2 s-1; enzyme-catalyzed: 2 × 10 5-1.4 × 106 s-1) and a turnover number (TON) of at least 1700, limited only by the experimental conditions used. So far, no copper-based natural carbonic anhydrases are known, no faster model systems have been described and the biological role of the patellamide macrocycles is so far unknown. The observed CO2 hydration rates depend on the configuration of the isopropyl side chains of the pseudo-octapeptide scaffold, and the naturally observed R*,S*, R*,S* geometry is shown to lead to more efficient catalysts than the S*,S*,S*,S* isomers. The catalytic efficiency also depends on the heterocyclic donor groups of the pseudo-octapeptides. Interestingly, the dicopper(ii) complex of the ligand with four imidazole groups is a more efficient catalyst than that of the close analogue of ascidiacyclamide with two thiazole and two oxazoline rings. The experimental observations indicate that the nucleophilic attack of a CuII- coordinated hydroxide at the CO2 carbon center is rate determining, i.e. formation of the catalyst-CO2 adduct and release of carbonate/bicarbonate are relatively fast processes.
Matrix isolation studies of carbonic acid - The vapor phase above the β-polymorph
Bernard, Jürgen,Huber, Roland G.,Liedl, Klaus R.,Grothe, Hinrich,Loerting, Thomas
, p. 7732 - 7737 (2013)
Twenty years ago two different polymorphs of carbonic acid, α- and β-H2CO3, were isolated as thin, crystalline films. They were characterized by infrared and, of late, by Raman spectroscopy. Determination of the crystal structure of these two polymorphs, using cryopowder and thin film X-ray diffraction techniques, has failed so far. Recently, we succeeded in sublimating α-H2CO3 and trapping the vapor phase in a noble gas matrix, which was analyzed by infrared spectroscopy. In the same way we have now investigated the β-polymorph. Unlike α-H2CO3, β-H2CO3 was regarded to decompose upon sublimation. Still, we have succeeded in isolation of undecomposed carbonic acid in the matrix and recondensation after removal of the matrix here. This possibility of sublimation and recondensation cycles of β-H2CO3 adds a new aspect to the chemistry of carbonic acid in astrophysical environments, especially because there is a direct way of β-H2CO3 formation in space, but none for α-H2CO3. Assignments of the FTIR spectra of the isolated molecules unambiguously reveal two different carbonic acid monomer conformers (C2v and Cs). In contrast to the earlier study on α-H2CO3, we do not find evidence for centrosymmetric (C2h) carbonic acid dimers here. This suggests that two monomers are entropically favored at the sublimation temperature of 250 K for β-H2CO3, whereas they are not at the sublimation temperature of 210 K for α-H2CO3.
Carbonic acid: Synthesis by protonation of bicarbonate and FTIR spectroscopic characterization via a new cryogenic technique
Hage, Wolfgang,Hallbrucker, Andreas,Mayer, Erwin
, p. 8427 - 8431 (1993)
Layers of glassy solutions of HCO3- (DCO3-) and of excess HCl (DCl) dissolved in CH3OH (CH3OD) were deposited one by one onto each other at 78 K in the form of droplets, and their reaction has been studied in vacua by FTIR spectroscopy from 78 to 300 K. At ≈120 K, i.e. ≈20 K above the solvents' glass transition temperature of 103 K, a decrease in the solvents' viscosity led to the beginning of the coalescence of the droplets. At ≈=140 to ≈160 K, a further decrease in the solvents' viscosity enabled the reaction Of HCO3- (DCO3-) with H+ (D+) as seen most clearly by the disappearance of the bicarbonate band at ≈1630 cm-1. Simultaneously formation of a band centered at ≈1730 cm-1 (≈1725 cm-1) is observed which is in the frequency region expected for a C=O stretching vibration of H2CO3 (D2CO3). Separation of the reaction product from the solvent was achieved by heating in vacuo up to ≈175 K and pumping off first methanol and excess HCl and then residual water. On further heating to ≈190 K, the reaction product also started to vaporize. We conclude that we have isolated carbonic acid via a novel cryogenic technique and give a preliminary assignment. It is important to note that the reaction can be reversed in an additional step by depositing a layer of KOH in glassy CH3OH onto the isolated carbonic acid. The new cryogenic technique is particularly suitable for studies of short-lived intermediates in the reaction of nonvolatile reactants such as biomolecules. It is possibly best applied to studies of consecutive reactions where a metastable intermediate is formed in the first step in a preliminary equilibrium and the second step is rate determining.
Enzyme-embedded metal-organic framework membranes on polymeric substrates for efficient CO2 capture
Zhang, Yiming,Wang, Huixian,Liu, Jindun,Hou, Jingwei,Zhang, Yatao
, p. 19954 - 19962 (2017)
In this work, carbonic anhydrase (CA) molecules were embedded into metal-organic frameworks (MOFs) via physical absorption and chemical bonds, which could overcome the enzymatic inactivation and the poor separation property of pristine MOF materials. And then, these nanocomposites (enzyme-embedded MOFs) as the crystal seeds were in situ grown on oriented halloysite nanotube layers to develop novel biocatalytic composite membranes. These membranes exhibited optimal separation performance with a CO2/N2 selectivity of 165.5, about 20.9 fold higher than that of the membrane without embedded CA molecules, surpassing the Robeson upper bound (2008). At the same time, the CO2 permeance increased about 3.2 fold (from 7.6 GPU to 24.16 GPU). Importantly, the biocatalytic composite membranes showed good stability and mechanical properties and were easily scalable, which could be extended to industrial applications.
Carbonic acid: From polyamorphism to polymorphism
Winkel, Katrin,Hage, Wolfgang,Loerting, Thomas,Price, Sarah L.,Mayer, Erwin
, p. 13863 - 13871 (2007)
Layers of glassy methanolic (aqueous) solutions of KHCO3 and HCl were deposited sequentially at 78 K on a CsI window, and their reaction on heating in vacuo in steps from 78 to 230 K was followed by Fourier transform infrared (FTIR) spectroscopy. After removal of solvent and excess HCl, IR spectra revealed formation of two distinct states of amorphous carbonic acid (H2CO3), depending on whether KHCO3 and HCl had been dissolved in methanol or in water, and of their phase transition to either crystalline α-or β-H2CO3. The main spectral features in the IR spectra of α- and β-H2CO3 are observable already in those of the two amorphous H2CO3 forms. This indicates that H-bond connectivity or conformational state in the two crystalline phases is on the whole already developed in the two amorphous forms. The amorphous nature of the precursors to the two crystalline polymorphs is confirmed using powder X-ray diffraction. These diffractograms also show that α- and β-amorphous H2CO3 are two distinct structural states. The variety of structural motifs found within a few kJ/mol in a computational search for possible crystal structures provides a plausible rationalization for (a) the observation of more than one amorphous form and (b) the retention of the motif observed in the amorphous form in the corresponding crystalline form. The polyamorphism inferred for carbonic acid from our FTIR spectroscopic and powder X-ray diffraction studies is special since two different crystalline states are linked to two distinct amorphous states. We surmise that the two amorphous states of H2CO3 are connected by a first-order-like phase transition.
Inhibition properties of new amino acids for prevention of hydrate formation in carbon dioxide-water system: Experimental and modeling investigations
Roosta, Hadi,Dashti, Ali,Mazloumi, S. Hossein,Varaminian, Farshad
, p. 656 - 663 (2016)
In the present work, the effect of new structures of amino acids is studied for prevention of hydrate formation in the carbon dioxide-water system. These amino acids consist of L-proline (as amino acid with nonpolar side chain), L-serine and L-glutamine (
Comprehensive study of the hydration and dehydration reactions of carbon dioxide in aqueous solution
Wang, Xiaoguang,Conway, William,Burns, Robert,McCann, Nichola,Maeder, Marcel
, p. 1734 - 1740 (2010)
The reversible interactions of dissolved CO2 with H2O and OH- to form H2CO3 and HCO3- in aqueous solution have been investigated using spectrophotometric stopped-flow measurements. The progress of the reactions
Mechanism of phenol degradation processes induced by direct-current atmospheric-pressure discharge in air
Bobkova,Sungurova,Rybkin
, p. 198 - 200 (2013)
The phenol degradation kinetics and the buildup kinetics of the products hydroxyphenols, nitrophenols, carboxylic acids, and formaldehyde in electrolytic-cathode direct-current discharge have been studied, as well as the formation of nitric acid. On the basis of the results, a scheme of the processes has been proposed; calculations according to this scheme describe well the experimental data on the degradation kinetics of phenol and the formation/decay kinetics of its transformation products.
Temperature- and pressure-dependent stopped-flow kinetic studies of jack bean urease. Implications for the catalytic mechanism
Krajewska, Barbara,Van Eldik, Rudi,Brindell, Ma?gorzata
, p. 1123 - 1134 (2012)
Urease, a Ni-containing metalloenzyme, features an activity that has profound medical and agricultural implications. The mechanism of this activity, however, has not been as yet thoroughly established. Accordingly, to improve its understanding, in this study we analyzed the steady-state kinetic parameters of the enzyme (jack bean), KM and kcat, measured at different temperatures and pressures. Such an analysis is useful as it provides information on the molecular nature of the intermediate and transition states of the catalytic reaction. We measured the parameters in a noninteracting buffer using a stopped-flow technique in the temperature range 15-35 °C and in the pressure range 5-132 MPa, the pressure-dependent measurements being the first of their kind performed for urease. While temperature enhanced the activity of urease, pressure inhibited the enzyme; the inhibition was biphasic. Analyzing KM provided the characteristics of the formation of the ES complex, and analyzing kcat, the characteristics of the activation of ES. From the temperature-dependent measurements, the energetic parameters were derived, i.e. thermodynamic ΔHo and ΔSo for ES formation, and kinetic ΔH≠ and ΔS≠ for ES activation, while from the pressuredependent measurements, the binding ΔVb and activation ΔV6cat ≠volumes were determined. The thermodynamic and activation parameters obtained are discussed in terms of the current proposals for the mechanism of the urease reaction, and they are found to support the mechanism proposed by Benini et al. (Structure 7:205-216; 1999), in which the Ni-Ni bridging hydroxide-not the terminal hydroxide-is the nucleophile in the catalytic reaction. SBIC 2012.
Influence of Ammonium Acetate Concentration on Receptor-Ligand Binding Affinities Measured by Native Nano ESI-MS: A Systematic Study
Gavriilidou, Agni F. M.,Gülbakan, Basri,Zenobi, Renato
, p. 10378 - 10384 (2015)
Native electrospray ionization (ESI) mass spectrometry (MS) is a powerful technique for analyzing biomolecules in their native state. However, ESI-MS is incompatible with nonvolatile solution additives. Therefore, biomolecules have to be electrosprayed from a solution that differs from their purification or storage buffer, often aqueous ammonium acetate (AmAc). In this study, the effect of the ionic strength on the dissociation constants of six different noncovalent complexes, that cover interactions present in many biological systems, was investigated. Complexes were electrosprayed from 10 mM, 50 mM, 100 mM, 300 mM, and 500 mM aqueous AmAc. For all systems, it was shown that the binding affinity is significantly influenced by the ionic strength of the solution. The determined dissociation constant (Kd) was affected more than 50% when increasing the AmAc concentration. The results are interpreted in terms of altered ionic interactions induced by the solution. This work emphasizes the modulating effect of the ions on noncovalent interactions and the importance of carefully choosing the AmAc concentration for quantifying the receptor-ligand binding strengths.
