Acetate Ions (acetate + ion)

Distribution by Scientific Domains
Distribution within Chemistry


Selected Abstracts


A novel thermostable hemoglobin from the actinobacterium Thermobifida fusca

FEBS JOURNAL, Issue 16 2005
Alessandra Bonamore
The gene coding for a hemoglobin-like protein (Tf-trHb) has been identified in the thermophilic actinobacterium Thermobifida fusca and cloned in Escherichia coli for overexpression. The crystal structure of the ferric, acetate-bound derivative, was obtained at 2.48 Å resolution. The three-dimensional structure of Tf-trHb is similar to structures reported for the truncated hemoglobins from Mycobacterium tuberculosis and Bacillus subtilis in its central domain. The complete lack of diffraction patterns relative to the N- and C-terminal segments indicates that these are unstructured polypeptides chains, consistent with their facile cleavage in solution. The absence of internal cavities and the presence of two water molecules between the bound acetate ion and the protein surface suggest that the mode of ligand entry is similar to that of typical hemoglobins. The protein is characterized by higher thermostability than the similar mesophilic truncated hemoglobin from B. subtilis, as demonstrated by far-UV CD melting experiments on the cyano-met derivatives. The ligand-binding properties of Tf-trHb, analyzed in stopped flow experiments, demonstrate that Tf-trHb is capable of efficient O2 binding and release between 55 and 60 °C, the optimal growth temperature for Thermobifida fusca. [source]


Free-radical 4-nitrophenylation of thieno[2,3- b]pyridine.

JOURNAL OF HETEROCYCLIC CHEMISTRY, Issue 6 2001
Part 3: Consideration of mechanistic, selectivity factors involved in the substitution process
A 1:1 geometrically oriented encounter complex between thieno[2,3-b]pyridine (1) and 4-nitrophenyldia-zoacetate (2) is proposed to account for the dominant formation (ca. 64%) of the 2-isomer in the mixture of 4-nitrophenyl-l isomers obtained previously. A mechanism involving one-electron transfer from 1 to 2 plus fragmentation of 2· into 4-nitrophenyl free radical, N2, and acetate ion is invoked. Formation of other isomers is discussed. It is noted that there is a close correlation between orientational rules plus mechanisms of reaction for numerous free-radical substitutions (SR) with SN reactions of alkyllithiums on furan, thiophene, N -alkylpyrroles, pyridine, and their condensed aromatic molecules, including 1, as substrates. Also isomeric selectivities for SE, SN, and SR substitutions into 1 were shown to be qualitatively consistent with one another. While SE reactions occur largely at position 3 and then at 2, SN and SR reactions occur either at 2 or 6. Selectivity for positions 4 or 5 is small or zero. [source]


Rv0802c from Mycobacterium tuberculosis: the first structure of a succinyltransferase with the GNAT fold

ACTA CRYSTALLOGRAPHICA SECTION F (ELECTRONIC), Issue 11 2008
Matthew W. Vetting
Gene rv0802c from Mycobacterium tuberculosis encodes a 218-amino-acid protein and is annotated as a hypothetical protein with homology to GCN5-related N -acetyltransferases. The structure of Rv0802c was determined in an unliganded form to 2.0,Å resolution utilizing single-wavelength anomalous dispersion from a samarium soak that resulted in a single bound Sm3+:citrate2 complex. The structure confirms that Rv0802c exhibits the GCN5-related N -acetyltransferase fold and revealed a tetramer composed of a dimer of dimers with approximate 222 symmetry. In addition, a bound acetate ion indicated that Rv0802c may utilize a unique acyl donor for the family. The subsequent determination of the structure of Rv0802c in complex with succinyl-CoA to 2.3,Å resolution suggests that Rv0802c is the first known GCN5-related N -acetyltransferase family member to utilize succinyl-CoA as a substrate. [source]


In Situ Synthesis of Trisubstituted Methanol Ligands and Their Potential as One-Pot Generators of Cubane-like Metal Complexes

CHEMISTRY - A EUROPEAN JOURNAL, Issue 27 2006
Brendan F. Abrahams Dr.
Abstract Two different one pot routes to a variety of metal cubane compounds are reported; one route is based on an in situ benzilic acid type rearrangement and the other involves in situ nucleophilic attack at a ketone. Diketosuccinic acid in basic solution in the presence of certain divalent metal ions undergoes a benzilic acid type rearrangement to generate the carbon oxyanion, C(CO2,)3O,, which serves as a cubane-forming bridging ligand in a series of octanuclear complexes of composition [M8{C(CO2)3O}4](H2O)12 (M=Mg, Mn, Fe, Co, Ni, Zn). At the heart of each of these highly symmetrical aggregates is an M4O4 cubane core, each oxygen component of which is provided by the alkoxo centre of a C(CO2,)3O, ligand. Reaction of 2,2,-pyridil, (2-C5H4N)COCO(2-C5H4N), and calcium nitrate in basic alcoholic solution, which proceeds by a similar benzilic acid type rearrangement, gives the cubane compounds, [Ca4L4(NO3)4] in which L=(2-C5H4N)2C(COOR)O, (R=Me or Et). Nucleophilic attack by bisulfite ion at the carbonyl carbon atom of 2,2,-dipyridyl ketone in the presence of certain divalent metals generates the electrically neutral complexes, [{(C5H4N)2SO3C(OH)}2M] (M=Mn, Fe, Co, Ni, Zn and Cd). Cubane-like complexes [M4{(C5H4N)2SO3C(O)}4] (M=Zn, Mn) can be obtained directly from 2,2,-dipyridyl ketone in one-pot reaction systems (sealed tube, 120,°C) if a base as weak as acetate ion is present to deprotonate the OH group of the initial [(C5H4N)2SO3C(OH)], bisulfite addition compound; the [(C5H4N)2SO3C(O)]2, ligand in this case plays the same cubane-forming role as the ligands C(COO,)3O, and (2-C5H4N)2C(COOR)O, above. When excess sodium sulfite is used in similar one-pot reaction mixtures, the monoanionic complexes, [M3Na{(C5H4N)2SO3C(O)}4], (M=Zn, Mn, Co) with an M3NaO4 cubane core, are formed directly from 2,2,-dipyridyl ketone. [source]


Highly Symmetrical Tetranuclear Cluster Complexes Supported by p - tert -Butylsulfonylcalix[4]arene as a Cluster-Forming Ligand

EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 9 2006
Takashi Kajiwara
Abstract Square-planar tetranuclear clusters [M4(L)(AcO)4(,4 -OH)], (M = MnII, CoII, and NiII) are synthesized using tetra-anionic p - tert -butylsulfonylcalix[4]arene (L4,) as a cluster-forming ligand. Three complexes are crystallographically isostructural, being crystallized in the triclinic crystal system with space group P. The calix[4]arene acts as a tetrakis fac -tridentate ligand through four phenoxo and four sulfonyl oxygen atoms to form square arrangement of four metal ions, which are further bridged by four chelating acetate ions and one hydroxo ion in a ,4 manner to complete the hexacoordination of each metal center. Although the whole molecule of each complex is crystallographically independent, the molecule is highly symmetrical with a pseudo-four-fold axis lying on the ,4 -OH, group. The tetranuclear clusters are stable enough to maintain the core structures even in highly dilute solution (,10 ,M), which was confirmed by mass spectroscopic study, however, bridging acetates were easily exchanged by other carboxylate chelates to form derivatives such as [M4(L)(BzO)4(OH)],. Metal,metal interactions were investigated by means of magnetic susceptibility, and it was revealed that both ferro- and antiferromagnetic interactions occur in the NiII complex depending on the bridging angles of Ni,O,Ni. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006) [source]


Preparation of Arylphosphonates by Palladium(0)-Catalyzed Cross-Coupling in the Presence of Acetate Additives: Synthetic and Mechanistic Studies

ADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 18 2009
Marcin Kalek
Abstract An efficient protocol for the synthesis of arylphosphonate diesters via a palladium-catalyzed cross-coupling of H-phosphonate diesters with aryl electrophiles, promoted by acetate ions, was developed. A significant shortening of the cross-coupling time in the presence of the added acetate ions was achieved for bidentate and monodentate supporting ligands, and for different aryl electrophiles (iodo, bromo and triflate derivatives). The reaction conditions were optimized in terms of amount of the catalyst, supporting ligands, and source of the acetate ion used. Various arylphosphonates, including those of potential biological significance, were synthesized using this newly developed protocol. Some mechanistic aspects of the investigated reactions are also discussed. [source]


Textural profiling and statistical optimization of crosslinked calcium-alginate-pectinate-cellulose acetophthalate gelisphere matrices

JOURNAL OF PHARMACEUTICAL SCIENCES, Issue 12 2002
Viness Pillay
Abstract A 25 factorial design was employed to statistically evaluate the textural properties of a crosslinked calcium-alginate-pectinate-cellulose acetophthalate gelisphere system. In accordance with the factorial matrix, gelispheres were formulated by titrating a combination polymeric solution comprised of sodium alginate, pectin and/or cellulose acetophthalate into an inducer solution (crosslinking agent) consisting of calcium and/or acetate ions. A Texture Analyzer was used to profile the gelisphere matrices for their resilience in the unhydrated and hydrated states, the fracture energy involved in matrix rupture, and the matrix hardness achieved with different levels of crosslinking. Significantly different textural properties were found among the crosslinked formulations. In particular, the unhydrated matrix resilience was selected as a parameter for optimization of the gelisphere formulation because of its large impact on drug release modulation, matrix integrity, and sensitivity to the crosslinking process. Resilience increased with increasing polymer concentration, irrespective of the polymer combination. Furthermore, resilience was not significantly influenced by the concentration of the crosslinking agents, but rather by the application of a higher polymer concentration in the crosslinking reaction; again irrespective of the polymer combination. In addition to the use of a factorial design, artificial neural modeling was employed to predict the textural properties based on the factorial matrix as a statistically suitable data source. Neural networks appeared to be a strong competitor of factorial regression for the prediction of textural data. © 2002 Wiley-Liss, Inc. and the American Pharmaceutical Association J Pharm Sci 91:2559,2570, 2002 [source]


Gelling of Alumina Suspensions Using Alginic Acid Salt and Hydroxyaluminum Diacetate

JOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 11 2002
Andre R. Studart
This paper proposes a novel direct casting method of alumina suspensions using alginic acid salt and the coagulation agent hydroxyaluminum diacetate (HADA). These two compounds allowed the consolidation of alumina suspensions through a simultaneous time-delayed physical and chemical gelation process. The physical gel was formed by the gradual release of aluminum and acetate ions from the HADA in water, while the chemical gel originated from the cross-linking of alginate molecules by the polyvalent aluminum ions. Wet alumina green bodies displayed enhanced mechanical properties with the addition of minimal contents of organic material (<0.1 wt%). [source]


A novel three-dimensional coordination polymer: poly[di-,3 -acetato-di-,2 -acetato-di-,3 -hydroxido-octa-,3 -triazolato-heptamanganese(II)]

ACTA CRYSTALLOGRAPHICA SECTION C, Issue 1 2008
Zhe-Hui Weng
The title compound, [Mn7(C2H2N3)8(C2H3O2)4(OH)2]n, is composed of centrosymmetric heptanuclear building units with the central Mn atom on an inversion center. In the building block, three MnII ions are held together by one ,3 -hydroxide group, two ,2 -triazolate (trz) ligands and two ,2 -acetate groups, forming an Mn3 cluster. Two Mn3 clusters are bridged by an Mn atom via two ,2 -trz ligands and two ,2 -O atoms from two acetate ions to construct a heptanuclear building block. The heptanuclear building units, lying parallel to each other along the b direction, form one-dimensional ladder-like chains and are further interlinked, resulting in a three-dimensional framework through Mn,Ntrz bonds. [source]