scholarly journals Gamma Irradiation of Aqueos Solution of L-Aspartic Acid, L-Aspartic Acid in Solid State, and L-Aspartic Acid Adsorbed into Na-Montmorillonite: Its Relevance in Chemistry Prebiotic

2021 ◽  
Vol 8 (2) ◽  
pp. 105-108
Author(s):  
A. Meléndez-López ◽  
M. F. García-Hurtado ◽  
J. Cruz-Castañeda ◽  
A. Negrón-Mendoza ◽  
S. Ramos-Bernal ◽  
...  
Keyword(s):  
Organic Matter ◽  
Amino Acid ◽  
Solid State ◽  
Aspartic Acid ◽  
Prebiotic Chemistry ◽  
High Energy ◽  
Energy Conditions ◽  
Gamma Radiolysis ◽  
The Stability

Aspartic acid is an amino acid present in the modern proteins, however, is considered a primitive amino acid hence its importance in prebiotic chemistry experiments studies. In some works of prebiotic chemistry have been studied the synthesis and the stability of organic matter under high energy sources, and the role of clays has been highlighted due to clays that can affect the reaction mechanisms in the radiolytic processes. The present work is focused on the study of the role of Namontmorillonite in the gamma radiolysis processes of L-aspartic acid. Gamma radiolysis processes were carried out in three different systems a) L-aspartic acid in aqueous solution; b) L-aspartic acid in solid-state; and c) L-aspartic acid adsorbed into Na-montmorillonite. L-aspartic acid was analyzed by high-performance liquid chromatography−electrospray ionization−mass spectrometry (HPLCESI-MS). The results showed that the decomposition of L-aspartic acid considerably decreased in the presence of clay thus highlighting the protector role of clays and favors the stability of organic matter even under the possible high energy conditions of primitive environments. The principal product ofgamma radiolysis of L-aspartic acid was succinic acid produced by deamination reaction. On the other hand, when aspartic acid was irradiated in solid-state the main product was the L-aspartic acid dimer. Both radiolysis products are important for chemical evolution processes for L-aspartic acid in primitive environments.

scholarly journals Effects of Amino Acid Substitutions at Conserved and Acidic Residues within Region 1.1 of Escherichia coli ς70

2000 ◽  
Vol 182 (1) ◽  
pp. 221-224 ◽  
Author(s):  
Christina Wilson Bowers ◽  
Andrea McCracken ◽  
Alicia J. Dombroski
Keyword(s):  
Escherichia Coli ◽  
Amino Acid ◽  
Aspartic Acid ◽  
Transcription Initiation ◽  
Amino Acid Substitutions ◽  
Conserved Residues ◽  
Acidic Residues

ABSTRACT Amino acid substitutions in Escherichia coliς70 were generated and characterized in an analysis of the role of region 1.1 in transcription initiation. Several acidic and conserved residues are tolerant of substitution. However, replacement of aspartic acid 61 with alanine results in inactivity caused by structural and functional thermolability.

scholarly journals Site-directed mutagenesis of class I HLA genes. Role of glycosylation in surface expression and functional recognition.

1987 ◽  
Vol 166 (5) ◽  
pp. 1329-1350 ◽  
Author(s):  
J A Barbosa ◽  
J Santos-Aguado ◽  
S J Mentzer ◽  
J L Strominger ◽  
S J Burakoff ◽  
...  
Keyword(s):  
Amino Acid ◽  
Gene Transfer ◽  
Aspartic Acid ◽  
Human Cell ◽  
Surface Expression ◽  
Carbohydrate Moiety ◽  
Class I ◽  
Directed Mutagenesis ◽  
L Cells

We have investigated the role of the carbohydrate moiety on the HLA-B7 molecule in mAb and CTL recognition using oligonucleotide-directed mutagenesis and gene transfer techniques. A conservative substitution of asparagine to glutamine at amino acid 86 in HLA-B7 was created to abolish the unique glycosylation site present on all HLA molecules. A second mutant B7 molecule was made by substituting asparagine-aspartic acid-threonine for the resident lysine-aspartic acid/lysine tripeptide at amino acids 176-178, thus creating an N-linked glycan at amino acid 176, which is additionally present on all known murine H-2 class I antigens. Upon gene transfer into mouse and human cell recipients, the HLA-B7M176+ mutant and normal HLA-B7 expressed identical levels of surface protein. However, the binding of two mAbs (MB40.2 and MB40.3) thought to recognize different epitopes of the HLA-B7 molecule was completely eliminated. In contrast, the HLA-B7M86- mutant displayed no surface expression (mouse L cells) or minimal surface expression (human RD cells or mouse L cells coexpressing human beta 2 microglobulin [beta 2m]) after indirect immunofluorescence (IIF) and flow cytometric analysis with a panel of 12 HLA-B7 mAb reactive with monomorphic and polymorphic determinants. Immunoprecipitation analysis demonstrated that intracellular denatured mutant protein was present. Tunicamycin treatment did not rescue the expression of HLA-B7M86- antigens to the cell surface; while interferon did induce higher levels of surface expression. Tunicamycin treatment also did not allow binding of the mAbs MB40.2 or MB40.3 to HLA-B7M176+ mutant antigens, suggesting that the carbohydrate moiety itself was not directly involved in the recognition or conformation of these mAb epitopes. Further mutation of the B7M86- molecule to create a glycan moiety at amino acid position 176 (B7M86-/176+) did not rescue normal levels of surface expression. Finally, neither mutation was seen to affect recognition by a panel of 12 allospecific CTL clones. The low expression of HLA-B7M86- on the surface of human cell transfectants was sufficient to achieve lysis, albeit at a reduced efficiency, and lysis could be increased by interferon induction of higher levels of expression. Thus, the carbohydrate moiety on HLA antigens plays a minimal or nonexistent role in recognition by available mAb and allospecific CTL clones.

Role of charged amino acid side chains in the stability and lipid binding ofManduca sexta apolipophorin III

1995 ◽  
Vol 30 (2-3) ◽  
pp. 211-223 ◽  
Author(s):  
Minal Upadhyaya ◽  
Kim Oikawa ◽  
Cyril M. Kay ◽  
Douglas G. Scraba ◽  
Roger Bradley ◽  
...  
Keyword(s):  
Amino Acid ◽  
Lipid Binding ◽  
Side Chains ◽  
Apolipophorin Iii ◽  
Amino Acid Side Chains ◽  
The Stability

Site-directed mutagenesis studies to probe the role of specific residues in the external loop (L3) of OmpF and OmpC porins in susceptibility of Serratia marcescens to antibiotics

2007 ◽  
Vol 53 (6) ◽  
pp. 710-719
Author(s):  
Sanela Begic ◽  
Elizabeth A. Worobec
Keyword(s):  
Amino Acid ◽  
Serratia Marcescens ◽  
Outer Membrane ◽  
Aspartic Acid ◽  
Site Directed Mutagenesis ◽  
Natural Resistance ◽  
Directed Mutagenesis ◽  
External Loop ◽  
Ompc Porin

Serratia marcescens is a nosocomial bacterium with natural resistance to a broad spectrum of antibiotics, making treatment challenging. One factor contributing to this natural antibiotic resistance is reduced outer membrane permeability, controlled in part by OmpF and OmpC porin proteins. To investigate the direct role of these porins in the diffusion of antibiotics across the outer membrane, we have created an ompF–ompC porin-deficient strain of S. marcescens. A considerable similarity between the S. marcescens porins and those from other members of Enterobacteriaceae was detected by sequence alignment, with the exception of a change in a conserved region of the third external loop (L3) of the S. marcescens OmpC protein. Serratia marcescens OmpC has aspartic acid instead of glycine in position 112, methionine instead of aspartic acid in position 114, and glutamine in position 124, while in S. marcescens OmpF this is a glycine at position 124. To investigate the role of amino acid positions 112, 114, and 124 and how the observed changes within OmpC porin may play a part in pore permeability, 2 OmpC sites were altered in the Enterobacteriaceae consensus (D112G and M114D) through site-directed mutagenesis. Also, Q124G in OmpC, G124Q in OmpF, and double mutants of these amino acid residues were constructed. Antibiotic accumulation assays and minimal inhibitory concentrations of the strains harboring the mutated porins were performed, while liposome swelling experiments were performed on purified porins. Our results demonstrate that the amino acid at position 114 is not responsible for either antibiotic size or ionic selection, the amino acid at position 112 is responsible for size selection only, and position 124 is involved in both size and ionic selection.

scholarly journals Phospho-N-Acetyl-Muramyl-Pentapeptide Translocase from Escherichia coli: Catalytic Role of Conserved Aspartic Acid Residues

2004 ◽  
Vol 186 (6) ◽  
pp. 1747-1757 ◽  
Author(s):  
Adrian J. Lloyd ◽  
Philip E. Brandish ◽  
Andrea M. Gilbey ◽  
Timothy D. H. Bugg
Keyword(s):  
Escherichia Coli ◽  
Amino Acid ◽  
Aspartic Acid ◽  
Catalytic Mechanism ◽  
Partial Purification ◽  
Sequence Alignments ◽  
Structural Environment ◽  
Essential Enzyme ◽  
Covalent Intermediate

ABSTRACT Phospho-N-acetyl-muramyl-pentapeptide translocase (translocase 1) catalyzes the first of a sequence of lipid-linked steps that ultimately assemble the peptidoglycan layer of the bacterial cell wall. This essential enzyme is the target of several natural product antibiotics and has recently been the focus of antimicrobial drug discovery programs. The catalytic mechanism of translocase 1 is believed to proceed via a covalent intermediate formed between phospho-N-acetyl-muramyl-pentapeptide and a nucleophilic amino acid residue. Amino acid sequence alignments of the translocase 1 family and members of the related transmembrane phosphosugar transferase superfamily revealed only three conserved residues that possess nucleophilic side chains: the aspartic acid residues D115, D116, and D267. Here we report the expression and partial purification of Escherichia coli translocase 1 as a C-terminal hexahistidine (C-His6) fusion protein. Three enzymes with the site-directed mutations D115N, D116N, and D267N were constructed, expressed, and purified as C-His6 fusions. Enzymatic analysis established that all three mutations eliminated translocase 1 activity, and this finding verified the essential role of these residues. By analogy with the structural environment of the double aspartate motif found in prenyl transferases, we propose a model whereby D115 and D116 chelate a magnesium ion that coordinates with the pyrophosphate bridge of the UDP-N-acetyl-muramyl-pentapeptide substrate and in which D267 therefore fulfills the role of the translocase 1 active-site nucleophile.

scholarly journals Challenges and prospects of the role of solid electrolytes in the revitalization of lithium metal batteries

2016 ◽  
Vol 4 (44) ◽  
pp. 17251-17259 ◽  
Author(s):  
Alberto Varzi ◽  
Rinaldo Raccichini ◽  
Stefano Passerini ◽  
Bruno Scrosati
Keyword(s):  
Solid State ◽  
Solid Electrolytes ◽  
High Energy ◽  
Lithium Metal ◽  
Lithium Metal Batteries ◽  
Solid State Electrolytes

Solid-state electrolytes for high energy lithium metal batteries are reviewed and critically discussed.

The role of pulsed electric fields treatment in enhancing the stability of amino acid - sugar complexes:- interactions between L-Phenylalanine and β-Cyclodextrin

2016 ◽  
Vol 51 (9) ◽  
pp. 1988-1996 ◽  
Author(s):  
Zhi-Hong Zhang ◽  
Lang-Hong Wang ◽  
Xin-An Zeng ◽  
Charles S. Brennan ◽  
Margaret Brennan ◽  
...  
Keyword(s):  
Amino Acid ◽  
Electric Fields ◽  
Pulsed Electric Fields ◽  
The Stability
Sign in / Sign up

Export Citation Format

Share Document