Synthesis and Structural Characterization of a Terminal Hydroxide Containing Alumoxane via Hydrolysis of Aluminum Hydrides

2004 ◽  
Vol 43 (4) ◽  
pp. 1217-1219 ◽  
Author(s):  
Ying Peng ◽  
Guangcai Bai ◽  
Hongjun Fan ◽  
Denis Vidovic ◽  
Herbert W. Roesky ◽  
...  
Keyword(s):  
Structural Characterization ◽  
Aluminum Hydrides ◽  
Hydrolysis Of

scholarly journals Characterization of O-Acetylation of N-Acetylglucosamine

2011 ◽  
Vol 286 (27) ◽  
pp. 23950-23958 ◽  
Author(s):  
Elvis Bernard ◽  
Thomas Rolain ◽  
Pascal Courtin ◽  
Alain Guillot ◽  
Philippe Langella ◽  
...  
Keyword(s):  
Cell Wall ◽  
Structural Characterization ◽  
Bacterial Species ◽  
Muramic Acid ◽  
Gram Positive Bacteria ◽  
Mutant Strains ◽  
Encoding Genes ◽  
Hydrolysis Of ◽  
Cell Wall Hydrolysis

Peptidoglycan (PG) N-acetyl muramic acid (MurNAc) O-acetylation is widely spread in Gram-positive bacteria and is generally associated with resistance against lysozyme and endogenous autolysins. We report here the presence of O-acetylation on N-acetylglucosamine (GlcNAc) in Lactobacillus plantarum PG. This modification of glycan strands was never described in bacteria. Fine structural characterization of acetylated muropeptides released from L. plantarum PG demonstrated that both MurNAc and GlcNAc are O-acetylated in this species. These two PG post-modifications rely on two dedicated O-acetyltransferase encoding genes, named oatA and oatB, respectively. By analyzing the resistance to cell wall hydrolysis of mutant strains, we showed that GlcNAc O-acetylation inhibits N-acetylglucosaminidase Acm2, the major L. plantarum autolysin. In this bacterial species, inactivation of oatA, encoding MurNAc O-acetyltransferase, resulted in marked sensitivity to lysozyme. Moreover, MurNAc over-O-acetylation was shown to activate autolysis through the putative N-acetylmuramoyl-l-alanine amidase LytH enzyme. Our data indicate that in L. plantarum, two different O-acetyltransferases play original and antagonistic roles in the modulation of the activity of endogenous autolysins.

Controlled hydrolysis of aryltellurium trichlorides using 2-pyrrolidinones: isolation and structural characterization of monomeric aryltellurium(IV) monohydroxides

RSC Advances ◽  
2011 ◽  
Vol 1 (5) ◽  
pp. 808 ◽  
Author(s):  
Shafalika Misra ◽  
Ashok K. S. Chauhan ◽  
Ramesh C. Srivastava ◽  
Andrew Duthie ◽  
R. J. Butcher
Keyword(s):  
Structural Characterization ◽  
Hydrolysis Of ◽  
Controlled Hydrolysis

Hydrolysis of tri-tert-butylaluminum: the first structural characterization of alkylalumoxanes [(R2Al)2O]n and (RAlO)n

1993 ◽  
Vol 115 (12) ◽  
pp. 4971-4984 ◽  
Author(s):  
Mark R. Mason ◽  
Janna M. Smith ◽  
Simon G. Bott ◽  
Andrew R. Barron
Keyword(s):  
Structural Characterization ◽  
Hydrolysis Of

Structural Characterization of Gels Prepared from Co-Hydrolysis of Tetraethoxysilane and Dimethyldiethoxysilane.

1992 ◽  
Vol 271 ◽  
Author(s):  
Florence Babonneau ◽  
Laurence Bois ◽  
Jacques Livage
Keyword(s):  
Structural Characterization ◽  
Silica Gels ◽  
Condensation Process ◽  
Modified Silica ◽  
Polymeric Gels ◽  
Organically Modified ◽  
Organically Modified Silica ◽  
Hydrolysis Of ◽  
Modified Silica Gels

ABSTRACTThis work is part of a more general study on the structural characterization of organically modified silica gels that are usually prepared from tetrafunctional, trifunctional and difunctional alkoxides. The systems that were investigated in this paper are gels prepared from co-hydrolysis of dimethyldiethoxysilane (DEDMS) and tetraethoxysilane (TEOS). The condensation process was followed by 29Si and 17O liquid NMR and shows clearly evidence for co-condensation reactions. Gels with various DEDMS/TEOS ratios were studied by 29Si and 1H MAS-NMR. The results are clearly correlated to the change in physical properties of the materials, from flexible polymeric gels at high DEDMS content to crosslinked brittle networks at low DEDMS content.

Molecular Structure Of Metal Alkoxide Precursors

1990 ◽  
Vol 180 ◽  
Author(s):  
C. Sanchez ◽  
P. Toledano ◽  
F. Ribot
Keyword(s):  
Molecular Structure ◽  
Structural Characterization ◽  
Metal Alkoxide ◽  
Condensation Reactions ◽  
Structure Of Metal ◽  
Basic Understanding ◽  
Mechanisms Of Formation ◽  
Hydrolysis Of ◽  
Alkoxide Precursors

ABSTRACTOxo-alkoxides and allied derivatives are the organic counter part of polyanions and polycations. Most of them do not lead to further polymerization and are therefore dead endswhich are grnerally not directly involved in the formation of macromolecular oxide networks. However their well defined structure make them good models for the basic understanding of the first steps of hydrolysis- condensation reactions. The structural characterization of a new metal oxo species Ce6(μ3-O)4(μ3-OH)4(acac)12 obtained via the hydrolysis of acetylacetone modified cerium isopropoxide is presented. Possible mechanisms of formation of this compound as well as for some other titanium Ti6(μ2-O)2(μ3-O)2(μ2-OAc)4(μ2-OPri)6(OPri)6 and niobium Nb8O10(OEt)20 based oxo-alkoxides will be discussed.

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