Role of the aminopyridine ring in thiamin-catalyzed reactions. II. Proton NMR evidence for high barriers to amino group rotation in 4-aminopyrimidines, including thiamin, at low pH in water

1982 ◽  
Vol 47 (14) ◽  
pp. 2748-2753 ◽  
Author(s):  
Frank Jordan
Keyword(s):  
Proton Nmr ◽  
Low Ph ◽  
Amino Group ◽  
Group Rotation ◽  
Catalyzed Reactions

scholarly journals Role of Anions in Low pH-induced Translocation of Diphtheria Toxin

1989 ◽  
Vol 264 (19) ◽  
pp. 11367-11372 ◽  
Author(s):  
J Ø Moskaug ◽  
K Sandvig ◽  
S Olsnes
Keyword(s):  
Diphtheria Toxin ◽  
Low Ph

scholarly journals Acid tolerance in early colonizers of oral biofilms

2021 ◽  
Vol 21 (1) ◽  
Author(s):  
Gabriella Boisen ◽  
Julia R. Davies ◽  
Jessica Neilands
Keyword(s):  
Acid Tolerance ◽  
Low Ph ◽  
Salivary Proteins ◽  
Confocal Scanning Laser Microscopy ◽  
Planktonic Cells ◽  
Tolerance Development ◽  
Salivary Pellicle ◽  
Oral Biofilms ◽  
Acid Tolerant

Abstract Background In caries, low pH drives selection and enrichment of acidogenic and aciduric bacteria in oral biofilms, and development of acid tolerance in early colonizers is thought to play a key role in this shift. Since previous studies have focussed on planktonic cells, the effect of biofilm growth as well as the role of a salivary pellicle on this process is largely unknown. We explored acid tolerance and acid tolerance response (ATR) induction in biofilm cells of both clinical and laboratory strains of three oral streptococcal species (Streptococcus gordonii, Streptococcus oralis and Streptococcus mutans) as well as two oral species of Actinomyces (A. naeslundii and A. odontolyticus) and examined the role of salivary proteins in acid tolerance development. Methods Biofilms were formed on surfaces in Ibidi® mini flow cells with or without a coating of salivary proteins and acid tolerance assessed by exposing them to a challenge known to kill non-acid tolerant cells (pH 3.5 for 30 min) followed by staining with LIVE/DEAD BacLight and confocal scanning laser microscopy. The ability to induce an ATR was assessed by exposing the biofilms to an adaptation pH (pH 5.5) for 2 hours prior to the low pH challenge. Results Biofilm formation significantly increased acid tolerance in all the clinical streptococcal strains (P < 0.05) whereas the laboratory strains varied in their response. In biofilms, S. oralis was much more acid tolerant than S. gordonii or S. mutans. A. naeslundii showed a significant increase in acid tolerance in biofilms compared to planktonic cells (P < 0.001) which was not seen for A. odontolyticus. All strains except S. oralis induced an ATR after pre-exposure to pH 5.5 (P < 0.05). The presence of a salivary pellicle enhanced both acid tolerance development and ATR induction in S. gordonii biofilms (P < 0.05) but did not affect the other bacteria to the same extent. Conclusions These findings suggest that factors such as surface contact, the presence of a salivary pellicle and sensing of environmental pH can contribute to the development of high levels of acid tolerance amongst early colonizers in oral biofilms which may be important in the initiation of caries.

Molecular Basis for Nucleotide-binding Specificity: Role of the Exocyclic Amino Group “N2” in Recognition by a Guanylyl-ribonuclease

2006 ◽  
Vol 355 (1) ◽  
pp. 72-84 ◽  
Author(s):  
Greta L. Schrift ◽  
Travis T. Waldron ◽  
Mitchell A. Timmons ◽  
S. Ramaswamy ◽  
William R. Kearney ◽  
...  
Keyword(s):  
Molecular Basis ◽  
Binding Specificity ◽  
Nucleotide Binding ◽  
Amino Group

scholarly journals The Role of Histidine Residues in Low-pH-Mediated Viral Membrane Fusion

Structure ◽  
2006 ◽  
Vol 14 (10) ◽  
pp. 1481-1487 ◽  
Author(s):  
Thorsten Kampmann ◽  
Daniela S. Mueller ◽  
Alan E. Mark ◽  
Paul R. Young ◽  
Bostjan Kobe
Keyword(s):  
Membrane Fusion ◽  
Low Ph ◽  
Viral Membrane ◽  
Histidine Residues ◽  
Viral Membrane Fusion

The stability of onoratoite, Sb8O11Cl2, in the supergene environment

2014 ◽  
Vol 78 (7) ◽  
pp. 1671-1675 ◽  
Author(s):  
Adam J. Roper ◽  
Peter Leverett ◽  
Timothy D. Murphy ◽  
Peter A. Williams
Keyword(s):  
Significant Influence ◽  
Secondary Phase ◽  
Low Ph ◽  
Stable Phase ◽  
Supergene Zone ◽  
A Value ◽  
Solubility Studies ◽  
The Stability ◽  
Very High

AbstractSynthesis and solubility studies of onoratoite have been undertaken to determine the role of this rare secondary phase in the immobilization of Sb and the conditions responsible for its formation in the supergene zone. Solubility studies were undertaken at 298.15 K. A value of ΔGfθ (Sb8O11Cl2, s, 298.15 K) = –2576 ±12 kJ mol–1 was derived. Calculations involving sénarmontite, Sb2O3, klebelsbergite, Sb4O4SO4(OH)2 and schafarzikite, FeSb2O4, show that onoratoite is a thermodynamically stable phase only at negligible activities of SO42–(aq) and low activities of Fe2+(aq), at low pH and very high activities of Cl–(aq). This explains why onoratoite is such a rare secondary phase and why it cannot exert any significant influence on the dispersion of Sb in the supergene environment.

scholarly journals Filament formation by metabolic enzymes is a specific adaptation to an advanced state of cellular starvation

2014 ◽  
Author(s):  
Ivana Petrovska ◽  
Elisabeth Nüske ◽  
Matthias C Munder ◽  
Gayathrie Kulasegaran ◽  
Liliana Malinovska ◽  
...  
Keyword(s):  
Metabolic Enzymes ◽  
Low Ph ◽  
General Mechanism ◽  
Filament Formation ◽  
Ph Change ◽  
Cooperative Process ◽  
A Cell ◽  
Enzymatic Inactivation ◽  
Physical Organization

One of the key questions in biology is how the metabolism of a cell responds to changes in the environment. In budding yeast, starvation causes a drop in intracellular pH, but the functional role of this pH change is not well understood. Here, we show that the enzyme glutamine synthetase (Gln1) forms filaments at low pH and that filament formation leads to enzymatic inactivation. Filament formation by Gln1 is a highly cooperative process, strongly dependent on macromolecular crowding, and involves back-to-back stacking of cylindrical homo-decamers into filaments that associate laterally to form higher order fibrils. Other metabolic enzymes also assemble into filaments at low pH. Hence, we propose that filament formation is a general mechanism to inactivate and store key metabolic enzymes during a state of advanced cellular starvation. These findings have broad implications for understanding the interplay between nutritional stress, the metabolism and the physical organization of a cell.

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