Search results for "aqueous solution"
showing 10 items of 1610 documents
Self-assembling of poly(aspartic acid) with bovine serum albumin in aqueous solutions
2016
Abstract Macromolecular co-assemblies built up in aqueous solutions, by using a linear polypeptide, poly(aspartic acid) (PAS), and a globular protein, bovine serum albumin (BSA), have been studied. The main interest was to identify the optimum conditions for an interpenetrated complex formation in order to design materials suitable for biomedical applications, such as drug delivery systems. BSA surface possesses several amino- and carboxylic groups available for covalent modification, and/or bioactive substances attachment. In the present study, mixtures between PAS and BSA were investigated at 37 °C in dilute aqueous solution by viscometry, dynamic light scattering and zeta potential deter…
QM/MM calculations of kinetic isotope effects in the chorismate mutase active site.
2003
Kinetic isotope effects have been computed for the Claisen rearrangement of chorismate to prephenate in aqueous solution and in the active site of chorismate mutase from B. subtilus. These included primary 13C and 18O and secondary 3H effects for substitutions at the bond-making and bond-breaking positions. The initial structures of the putative stationary points on the potential energy surface, required for the calculations of isotope effects using the CAMVIB/CAMISO programs, have been selected from hybrid QM/MM molecular dynamical simulations using the DYNAMO program. Refinement of the reactant complex and transition-state structures has been carried out by means of AM1/CHARMM24/TIP3P cal…
Computational study on hydrolysis of cefotaxime in gas phase and in aqueous solution
2012
We are presenting a theoretical study of the hydrolysis of a β-lactam antibiotic in gas phase and in aqueous solution by means of hybrid quantum mechanics/molecular mechanics potentials. After exploring the potential energy surfaces at semiempirical and density functional theory (DFT) level, potentials of mean force have been computed for the reaction in solution with hybrid PM3/TIP3P calculations and corrections with the B3LYP and M06-2X functionals. Inclusion of the full molecule of the antibiotic, Cefotaxime, in the gas phase molecular model has been demonstrated to be crucial since its carboxylate group can activate a nucleophilic water molecule. Moreover, the flexibility of the substra…
Magnesium Exchanged Zirconium Metal−Organic Frameworks with Improved Detoxification Properties of Nerve Agents
2019
UiO-66, MOF-808 and NU-1000 metal-organic frameworks exhibit a differentiated reactivity toward [Mg(OMe)2(MeOH)2]4 related to their pore accessibility. Microporous UiO-66 remains unchanged while mesoporous MOF-808 and hierarchical micro/mesoporous NU-1000 materials yield doped systems containing exposed MgZr5O2(OH)6 clusters in the mesoporous cavities. This modification is responsible for a remarkable enhancement of the catalytic activity toward the hydrolytic degradation of P-F and P-S bonds of toxic nerve agents, at room temperature, in unbuffered aqueous solutions.
Synthetically persistent, self assembled [V(IV)2V(V)4] polyoxovanadates: facile synthesis, structure and magnetic analysis.
2011
Slow diffusion in a H-tube at room temperature of a methanolic solution of [VO(acac)(2)] (Hacac = acetylacetone) and 1,10-phenanthroline (phen) or 2,2'-bipyridine (bipy) into an aqueous solution of sodium pyrophosphate (Na(4)P(2)O(7)) resulted in the serendipitous formation of X-ray quality crystals of mixed-valent, hexameric oxovanadates of general formula [V(6)O(12)(OCH(3))(4)(L)(4)]·solv [L = 1,10-phenanthroline (phen) for 1· 2CH(3)OH · 4H(2)O (1a), and 2,2'-bipyridine (bipy) for 2· 4H(2)O (2a)]. These were characterized by single-crystal X-ray diffraction, IR, elemental and thermogravimetric analysis (TGA). A facile, rationalized synthetic route for the isolation of 1a and 2a could be e…
Mass spectrometric studies on small open-chain piperazine-containing ligands and their transition metal complexes
2001
Electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry was used to characterize the complexes formed between open-chain piperazine-containing ligands and transition metal salts (Cobalt, Copper, Zinc, and Cadmium as chlorides, nitrates, and acetates). Only single-charged complexes were observed, formed of one ligand (L) and mainly one metal ion (M). Since the net charge of the complexes was one, a counterion (X) was attached to some of the complexes, with formation of [L + M + X]+ complexes, and a proton was lost from others, as in [L − H + M]+ complexes. In most cases the composition of the complexes was more dependent on the ligand than the metal salt. Collisio…
Cyclometalated Au(III) Complexes for Cysteine Arylation in Zinc Finger Protein Domains: Towards Controlled Reductive Elimination
2019
With the aim of exploiting the use of organometallic species for the efficient modification of proteins through C-atom transfer, the gold-mediated cysteine arylation through a reductive elimination process occurring from the reaction of cyclometalated AuIII C^N complexes with a zinc finger peptide (Cys2His2 type) is here reported. Among the four selected AuIII cyclometalated compounds, the [Au(CCON)Cl2] complex featuring the 2-benzoylpyridine (CCON) scaffold was identified as the most prone to reductive elimination and Cys arylation in buffered aqueous solution (pH 7.4) at 37 °C by high-resolution LC electrospray ionization mass spectrometry. DFT and quantum mechanics/molecular mechanics (Q…
Solubility of the assemblage albite+K-feldspar+andalusite+quartz in supercritical aqueous chloride solutions at 650 °C and 2 kbar
2003
Abstract The solubility of the high grade pelite assemblage albite+K-feldspar+andalusite+quartz at 650 °C and 2 kbar was determined in aqueous solutions over a total chloride range of 0.01–3 mCltot using rapid-quench hydrothermal technique. The concentration of Na, K, Si, and Al was determined in the fluid phase after quench. The K/Na ratio was determined by approaching the equilibrium from below and above. It is 0.34 at low chloride concentrations and decreases slightly to 0.31 with increasing total chloride. Silica and aluminum concentrations were determined only from undersaturation. The silica solubility is found to be independent of chloride concentration and is ∼0.13 molal. Aluminum i…
Volumes and heat capacities of anionic-nonionic surfactant mixtures
1995
Density, heat capacity and surface tension measurements of sodium decylsulfate (NaDeS)-dodecyldimethylamine oxide (DDAO)-water mixtures were carried out as functions of the surfactants total molality mt at fixed stoichiometric mixture compositions XNaDeS. From the surface tension data, the critical micelle concentration of NaDeS-DDAO mixtures as a function of XNaDeS were obtained. From density and heat capacity data, the apparent molar volume VΦ,2 and heat capacity CΦ,2 of NaDeS-DDAO mixtures in water were calculated, respectively. At a given mole fraction, VΦ,2 and CΦ,2 monotonically increases and decreases, respectively, with increasing mt. However, anomalies were observed at XNaDeS=0.1 a…
Experimental study on the solubility of the “model”-pelite mineral assemblage albite + K-feldspar + andalusite + quartz in supercritical chloride-ric…
2001
A total of 34 solubility experiments using the “model”-pelite mineral assemblage microcline + low albite + andalusite + quartz were performed at 600°C and 0.2 GPa over a total chloride range of 0.03–2.9 molal. The concentrations of sodium, potassium, aluminum, and silica were measured and the results are compared with four different thermodynamic datasets. The K/Na ratio was approached from below and above for the thermodynamically buffered mineral assemblage microcline + low albite + andalusite + quartz. Tight brackets were obtained for experiments performed in up to 1 molal chloride concentration. From 0.03 to ∼1 molal chloride concentration, a constant K/Na ratio of 0.33 was obtained. At…