scholarly journals Effect of Tricarboxylic Acids on the Formation of Hydrogels with Melem or Melamine: Morphological, Structural and Rheological Investigations

Gels ◽  
2022 ◽  
Vol 8 (1) ◽  
pp. 51
Author(s):  
Pradip Kumar Sukul ◽  
Puspendu Das ◽  
Gopal Lal Dhakar ◽  
Lalmohan Das ◽  
Sudip Malik
Keyword(s):  
Carboxylic Acid ◽  
Optical Microscopy ◽  
Aqueous Medium ◽  
Viscoelastic Properties ◽  
Tricarboxylic Acid ◽  
Size Selectivity ◽  
Component Systems ◽  
Two Component ◽  
Two Component Systems ◽  
Aggregation Behaviors

Herein, aggregation behaviors of melem or melamine in the presence of three symmetric carboxylic acids (1,3,5-tris(4-carboxyphenyl)benzene (TPCA), 1,3,5-benzene-tri-carboxylic acid (BTA) and 1,3,5-cyclohexane-tri-carboxylic acid (CHTA)) have been performed to check the influence of acid on the formation of aggregated structures which have been investigated by optical microscopy, FESEM, FTIR, XRD and viscoelastic properties have been explored with rheological studies. Interestingly, melem, that has limited solubility in aqueous medium, forms aggregation that leads to the formation of hydrogels with TPCA. More significantly, hydrogel is formed here by matching the size selectivity. Melem forms hydrogel with only large tricarboxylic acid, whereas melamine produces hydrogel with any kind of its counterpart from small to large tricarboxylic acid derivatives. Present investigations and results provide the strategy of design of organic self-assembled materials having two component systems.

Diffusive layering during film growth in two-component systems with limited mutual solubility

2000 ◽  
Author(s):  
Grigory V. Merkulov ◽  
Valentin M. Ievlev ◽  
Evgeny V. Shvedov ◽  
Vadim P. Ampilogov
Keyword(s):  
Film Growth ◽  
Mutual Solubility ◽  
Component Systems ◽  
Two Component ◽  
Two Component Systems

scholarly journals Regulation of virulence and β-lactamase gene expression in Staphylococcus aureus isolates: cooperation of two-component systems in bloodstream superbugs

2021 ◽  
Vol 21 (1) ◽  
Author(s):  
Sanaz Dehbashi ◽  
Hamed Tahmasebi ◽  
Behrouz Zeyni ◽  
Mohammad Reza Arabestani
Keyword(s):  
Staphylococcus Aureus ◽  
Real Time ◽  
Real Time Pcr ◽  
Quantitative Real Time Pcr ◽  
Gene Expressions ◽  
Resistance Development ◽  
Component Systems ◽  
Two Component ◽  
Two Component Systems ◽  
Lactamase Gene

Abstract Background Methicillin-resistant Staphylococcus aureus (MRSA)-bloodstream infections (BSI) are predominantly seen in the hospital or healthcare-associated host. Nevertheless, the interactions of virulence factor (VFs) regulators and β-lactam resistance in MRSA-BSI are unclear. This study aims to characterize the molecular relationship of two-component systems of VFs and the expression of the β-lactamase gene in MRSA-BSI isolates. In this study, 639 samples were collected from BSI and identified by phenotypic methods. We performed extensive molecular characterization, including SCCmec type, agr type, VFs gene profiles determinations, and MLST on isolates. Also, a quantitative real-time PCR (q-RT PCR) assay was developed for identifying the gene expressions. Results Ninety-one (91) S. aureus and 61 MRSA (67.0%) strains were detected in BSI samples. The presence of VFs and SCCmec genes in MRSA isolates were as follows: tst (31.4%), etA (18.0%), etB (8.19%), lukS-PVL (31.4%), lukF-PV (18.0%), lukE-lukD (16.3%), edin (3.2%), hla (16.3%), hlb (18.0%), hld (14.7%), hlg (22.9%), SCCmecI (16.3%), SCCmecII (22.9%), SCCmecIII (36.0%), SCCmecIV (21.3%), and SCCmecV (16.3%). Quantitative real-time PCR showed overexpression of mecRI and mecI in the toxigenic isolates. Moreover, RNAIII and sarA genes were the highest expressions of MRSA strains. The multi-locus sequence typing data confirmed a high prevalence of CC5, CC8, and CC30. However, ST30, ST22, and ST5 were the most prevalent in the resistant and toxigenic strains. Conclusion We demonstrated that although regulation of β-lactamase gene expressions is a significant contributor to resistance development, two-component systems also influence antibiotic resistance development in MRSA-BSI isolates. This indicates that resistant strains might have pathogenic potential. We also confirmed that some MLST types are more successful colonizers with a potential for MRSA-BSI.

Monte Carlo Simulation of Electronic Excitation Migrationand Trappingin Disordered Two-Component Systems. A Comparison with Analytical Theories

1989 ◽  
Vol 44 (4) ◽  
pp. 257-261 ◽  
Author(s):  
Sławomir Błonski ◽  
Czesław Bojarski
Keyword(s):  
Monte Carlo ◽  
Electronic Excitation ◽  
Two Component System ◽  
Component System ◽  
Steady State Fluorescence ◽  
Donor And Acceptor ◽  
Component Systems ◽  
Two Component ◽  
Two Component Systems ◽  
Viscous Solution

Abstract Monte Carlo simulations of quantum yield and anisotropy of fluorescence in two-component systems have been conducted with various donor and acceptor concentrations and Förster radii ratios RDAO/RDDO. The influence of excitation migration and trapping on the fluorescence of the viscous solution has been considered. The results of the simulations have shown that steady-state fluorescence of a two-component system depends on the RDAO/RDDO ratio as predicted in LAF theory.

Global chromosome topology and the two-component systems in concerted manner regulate transcription in Streptomyces

2021 ◽  
Author(s):  
Martyna Gongerowska-Jac ◽  
Marcin Jan Szafran ◽  
Jakub Mikołajczyk ◽  
Justyna Szymczak ◽  
Magdalena Bartyńska ◽  
...  
Keyword(s):  
Topoisomerase I ◽  
Dna Supercoiling ◽  
Complex Life Cycle ◽  
Two Component System ◽  
Bacterial Gene ◽  
Component System ◽  
Global Regulators ◽  
Component Systems ◽  
Two Component ◽  
Two Component Systems

Bacterial gene expression is controlled at multiple levels, with chromosome supercoiling being one of the most global regulators. Global DNA supercoiling is maintained by the orchestrated action of topoisomerases. In Streptomyces, mycelial soil bacteria with a complex life cycle, topoisomerase I depletion led to elevated chromosome supercoiling, changed expression of significant fraction of genes, delayed growth and blocked sporulation. To identify supercoiling-induced sporulation regulators, we searched for S. coelicolor transposon mutants that were able to restore sporulation despite high chromosome supercoiling. We established that transposon insertion in genes encoding a novel two-component system named SatKR reversed the sporulation blockage resulting from topoisomerase I depletion. Transposition in satKR abolished the transcriptional induction of the genes within the so-called supercoiling-hypersensitive cluster (SHC). Moreover, we found that activated SatR also induced the same set of SHC genes under normal supercoiling conditions. We determined that the expression of genes in this region impacted S. coelicolor growth and sporulation. Interestingly, among the associated products is another two-component system (SitKR), indicating the potential for cascading regulatory effects driven by the SatKR and SitKR two-component systems. Thus, we demonstrated the concerted activity of chromosome supercoiling and a hierarchical two-component signalling system that impacts gene activity governing Streptomyces growth and sporulation.

scholarly journals Multiple Mechanisms of Action for Inhibitors of Histidine Protein Kinases from Bacterial Two-Component Systems

1999 ◽  
Vol 43 (7) ◽  
pp. 1693-1699 ◽  
Author(s):  
Jamese J. Hilliard ◽  
Raul M. Goldschmidt ◽  
Lisa Licata ◽  
Ellen Z. Baum ◽  
Karen Bush
Keyword(s):  
Pathogenic Bacteria ◽  
Response Regulator ◽  
Membrane Integrity ◽  
Bacterial Killing ◽  
Gram Positive Bacteria ◽  
Component Systems ◽  
Two Component ◽  
Two Component Systems ◽  
Bacterial Cell Membrane ◽  
Cellular Incorporation

ABSTRACT Many pathogenic bacteria utilize two-component systems consisting of a histidine protein kinase (HPK) and a response regulator (RR) for signal transduction. During the search for novel inhibitors, several chemical series, including benzoxazines, benzimidazoles, bis-phenols, cyclohexenes, trityls, and salicylanilides, were identified that inhibited the purified HPK-RR pairs KinA-Spo0F and NRII-NRI, with 50% inhibitory concentrations (IC50s) ranging from 1.9 to >500 μM and MICs ranging from 0.5 to >16 μg/ml for gram-positive bacteria. However, additional observations suggested that mechanisms other than HPK inhibition might contribute to antibacterial activity. In the present work, representative compounds from the six different series of inhibitors were analyzed for their effects on membrane integrity and macromolecular synthesis. At 4× MIC, 17 of 24 compounds compromised the integrity of the bacterial cell membrane within 10 min, as measured by uptake of propidium iodide. In this set, compounds with lower IC50s tended to cause greater membrane disruption. Eleven of 12 compounds inhibited cellular incorporation of radiolabeled thymidine and uridine >97% in 5 min and amino acids >80% in 15 min. The HPK inhibitor that allowed >25% precursor incorporation had no measurable MIC (>16 μg/ml). Fifteen of 24 compounds also caused hemolysis of equine erythrocytes. Thus, the antibacterial HPK inhibitors caused a rapid decrease in cellular incorporation of RNA, DNA, and protein precursors, possibly as a result of the concomitant disruption of the cytoplasmic membrane. Bacterial killing by these HPK inhibitors may therefore be due to multiple mechanisms, independent of HPK inhibition.

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