Planar chromatography of heavy metals on soil as stationary phase with amino acid-containing mobile phases

2008 ◽  
Vol 21 (6) ◽  
pp. 453-460
Author(s):  
Ali Mohammad ◽  
Abdul Moheman ◽  
Seema
Keyword(s):  
Heavy Metals ◽  
Amino Acid ◽  
Stationary Phase ◽  
Planar Chromatography ◽  
Mobile Phases

scholarly journals 6S RNA regulation of relA alters ppGpp levels in early stationary phase

Microbiology ◽  
2010 ◽  
Vol 156 (12) ◽  
pp. 3791-3800 ◽  
Author(s):  
Amy T. Cavanagh ◽  
Pete Chandrangsu ◽  
Karen M. Wassarman
Keyword(s):  
Amino Acid ◽  
Stationary Phase ◽  
Regulation Of Transcription ◽  
Early Stationary Phase ◽  
Rna Regulation ◽  
Global Regulators ◽  
Expression Of Genes ◽  
Non Coding Rna ◽  
6S Rna ◽  
Altered Regulation

6S RNA is a small, non-coding RNA that interacts directly with σ 70-RNA polymerase and regulates transcription at many σ 70-dependent promoters. Here, we demonstrate that 6S RNA regulates transcription of relA, which encodes a ppGpp synthase. The 6S RNA-dependent regulation of relA expression results in increased ppGpp levels during early stationary phase in cells lacking 6S RNA. These changes in ppGpp levels, although modest, are sufficient to result in altered regulation of transcription from σ 70-dependent promoters sensitive to ppGpp, including those promoting expression of genes involved in amino acid biosynthesis and rRNA. These data place 6S RNA as another player in maintaining appropriate gene expression as cells transition into stationary phase. Independent of this ppGpp-mediated 6S RNA-dependent regulation, we also demonstrate that in later stationary phase, 6S RNA continues to downregulate transcription in general, and specifically at a subset of the amino acid promoters, but through a mechanism that is independent of ppGpp and which we hypothesize is through direct regulation. In addition, 6S RNA-dependent regulation of σ S activity is not mediated through observed changes in ppGpp levels. We suggest a role for 6S RNA in modulating transcription of several global regulators directly, including relA, to downregulate expression of key pathways in response to changing environmental conditions.

scholarly journals Normal and reversed phase thin-layer chromatography of new 16, 17-secoestrone derivatives

2003 ◽  
Vol 68 (1) ◽  
pp. 57-64 ◽  
Author(s):  
Marijana Acanski ◽  
Suzana Jovanovic-Santa ◽  
Lidija Jevric
Keyword(s):  
Thin Layer ◽  
Stationary Phase ◽  
Thin Layer Chromatography ◽  
Silica Gel ◽  
Reversed Phase ◽  
Retention Behavior ◽  
Mobile Phases ◽  
Layer Chromatography

The retention behavior and separation ability of a series of new 16,17-secoestrone derivatives has been studied on silica gel, alumina and C-18 silica gel layers with non-aqueous and aqueous-organic mobile phases. The retention behavior and separation ability are discussed in terms of the nature of the solute, eluent and stationary phase.

Supercritical Adsorption

2005 ◽  
Author(s):  
Eldred H. Chimowitz
Keyword(s):  
Stationary Phase ◽  
Critical Point ◽  
Dynamic Models ◽  
Molecular Diffusion ◽  
Plug Flow ◽  
Fluid Phase ◽  
Commercial Application ◽  
Critical Systems ◽  
Mobile Phases ◽  
Column Dynamics

In this chapter, we discuss adsorption phenomena in supercritical systems, a situation that occurs in many application areas in chemical-process and materials engineering. An example of a commercial application in this area, which has achieved wide acceptance as a tool in analytical chemistry, is supercritical fluid chromatography (SFC). Not only is SFC a powerful technique for chemical analysis, but it also is a useful method for measuring transportive and thermodynamic properties in the near-critical systems. In the next section, we analyze adsorption-column dynamics using simple dynamic models, and describe how data from a chromatographic column can be used to estimate various thermodynamic and transport properties.We then proceed to discuss the effects of proximity to the critical point on adsorption behavior in these systems. The closer the system is to its critical point, the more interesting is its behavior. For very dilute solute systems, like those considered here, the energy balance is often ignored to a first approximation; this leads to a simple set of mass-balance equations defining transport for each species. These equations can be developed to various levels of complexity, depending upon the treatment of the adsorbent (stationary phase). The conceptual view of these phases can span a wide range of possibilities ranging from completely nonporous solids (fused structures) to porous materials with complicated ill-defined pore structures. Given these considerations, it is customary to make the following assumptions in the development of a simple model of adsorber-bed dynamics: . . .1. The stationary and mobile phases are continuous in the direction of the flow, with the fluid phase possessing a flat velocity profile (“plug” flow).. . . . . . 2. The porosity of the stationary phase is considered constant irrespective of pressure and temperature conditions (i.e., it is incompressible). . . . . . .3. The column is considered to be radially homogeneous, leading to a set of equations with one spatially independent variable, representing distance along the column axis. . . . . . . 4. The dispersion term in the model equation represents the combined effects of molecular diffusion and dispersion due to convective stirring in the bed. These effects are combined into an effective phenomenological dispersion coefficient, considered to be constant throughout the column. . . .

scholarly journals A tryptophan C-methyltransferase involved in streptonigrin biosynthesis in Streptomyces flocculus

1984 ◽  
Vol 220 (1) ◽  
pp. 309-313 ◽  
Author(s):  
D L Hartley ◽  
M K Speedie
Keyword(s):  
High Pressure ◽  
Liquid Chromatography ◽  
Amino Acid ◽  
Stationary Phase ◽  
High Pressure Liquid Chromatography ◽  
Absolute Configuration ◽  
Specific Activity ◽  
Shake Culture ◽  
Methyl Group ◽  
The Absolute

A C-methyltransferase that catalyses the transfer of a methyl group from S-adenosylmethionine to C-3 of tryptophan, resulting in beta-methyltryptophan, has been identified in cell-free extracts of streptonigrin-producing Streptomyces flocculus. The absolute configuration of the product was shown to be (2S,3R)-beta-methyltryptophan by high-pressure liquid chromatography and reactivity with D- and L-amino acid oxidases. In shake culture, maximum specific activity occurs after S. flocculus enters stationary phase, but before significant streptonigrin accumulates.

Enantiomeric Separation of (±)-Amino Acid Esters on (−)-Phenylurea Chiral Stationary Phase

1999 ◽  
Vol 63 (1) ◽  
pp. 18-23
Author(s):  
Kwang-Pill Lee ◽  
Hyun-Bong Lee ◽  
Young Cheol Lee ◽  
Seong-Ho Choi ◽  
Jae Jeong Ryoo ◽  
...  
Keyword(s):  
Amino Acid ◽  
Stationary Phase ◽  
Chiral Stationary Phase ◽  
Enantiomeric Separation ◽  
Amino Acid Esters ◽  
Acid Esters

scholarly journals Involvement of FtsE ATPase and FtsX Extracellular Loops 1 and 2 in FtsEX-PcsB Complex Function in Cell Division of Streptococcus pneumoniae D39

mBio ◽  
2013 ◽  
Vol 4 (4) ◽  
Author(s):  
Lok-To Sham ◽  
Katelyn R. Jensen ◽  
Kevin E. Bruce ◽  
Malcolm E. Winkler
Keyword(s):  
Signal Transduction ◽  
Amino Acids ◽  
Cell Division ◽  
Streptococcus Pneumoniae ◽  
Amino Acid ◽  
Stationary Phase ◽  
Coiled Coil ◽  
Extracellular Loop ◽  
Coiled Coil Domain ◽  
Loop Domain

ABSTRACT The FtsEX protein complex has recently been proposed to play a major role in coordinating peptidoglycan (PG) remodeling by hydrolases with the division of bacterial cells. According to this model, cytoplasmic FtsE ATPase interacts with the FtsZ divisome and FtsX integral membrane protein and powers allosteric activation of an extracellular hydrolase interacting with FtsX. In the major human respiratory pathogen Streptococcus pneumoniae (pneumococcus), a large extracellular-loop domain of FtsX (ECL1FtsX) is thought to interact with the coiled-coil domain of the PcsB protein, which likely functions as a PG amidase or endopeptidase required for normal cell division. This paper provides evidence for two key tenets of this model. First, we show that FtsE protein is essential, that depletion of FtsE phenocopies cell defects caused by depletion of FtsX or PcsB, and that changes of conserved amino acids in the FtsE ATPase active site are not tolerated. Second, we show that temperature-sensitive (Ts) pcsB mutations resulting in amino acid changes in the PcsB coiled-coil domain (CCPcsB) are suppressed by ftsX mutations resulting in amino acid changes in the distal part of ECL1FtsX or in a second, small extracellular-loop domain (ECL2FtsX). Some FtsX suppressors are allele specific for changes in CCPcsB, and no FtsX suppressors were found for amino acid changes in the catalytic PcsB CHAP domain (CHAPPcsB). These results strongly support roles for both ECL1FtsX and ECL2FtsX in signal transduction to the coiled-coil domain of PcsB. Finally, we found that pcsB CC(Ts) mutants (Ts mutants carrying mutations in the region of pcsB corresponding to the coiled-coil domain) unexpectedly exhibit delayed stationary-phase autolysis at a permissive growth temperature. IMPORTANCE Little is known about how FtsX interacts with cognate PG hydrolases in any bacterium, besides that ECL1FtsX domains somehow interact with coiled-coil domains. This work used powerful genetic approaches to implicate a specific region of pneumococcal ECL1FtsX and the small ECL2FtsX in the interaction with CCPcsB. These findings identify amino acids important for in vivo signal transduction between FtsX and PcsB for the first time. This paper also supports the central hypothesis that signal transduction between pneumococcal FtsX and PcsB is linked to ATP hydrolysis by essential FtsE, which couples PG hydrolysis to cell division. The classical genetic approaches used here can be applied to dissect interactions of other integral membrane proteins involved in PG biosynthesis. Finally, delayed autolysis of the pcsB CC(Ts) mutants suggests that the FtsEX-PcsB PG hydrolase may generate a signal in the PG necessary for activation of the major LytA autolysin as pneumococcal cells enter stationary phase.

Metabolite and transcriptome analysis of Campylobacter jejuni in vitro growth reveals a stationary-phase physiological switch

Microbiology ◽  
2009 ◽  
Vol 155 (1) ◽  
pp. 80-94 ◽  
Author(s):  
John A. Wright ◽  
Andrew J. Grant ◽  
Douglas Hurd ◽  
Marcus Harrison ◽  
Edward J. Guccione ◽  
...  
Keyword(s):  
Amino Acid ◽  
Stationary Phase ◽  
Campylobacter Jejuni ◽  
Growth Cycle ◽  
Video Tracking ◽  
Acetate Excretion ◽  
Food Borne ◽  
Amino Acid Utilization ◽  
Switch Mechanism

Campylobacter jejuni is a prevalent cause of food-borne diarrhoeal illness in humans. Understanding of the physiological and metabolic capabilities of the organism is limited. We report a detailed analysis of the C. jejuni growth cycle in batch culture. Combined transcriptomic, phenotypic and metabolic analysis demonstrates a highly dynamic ‘stationary phase’, characterized by a peak in motility, numerous gene expression changes and substrate switching, despite transcript changes that indicate a metabolic downshift upon the onset of stationary phase. Video tracking of bacterial motility identifies peak activity during stationary phase. Amino acid analysis of culture supernatants shows a preferential order of amino acid utilization. Proton NMR (1H-NMR) highlights an acetate switch mechanism whereby bacteria change from acetate excretion to acetate uptake, most probably in response to depletion of other substrates. Acetate production requires pta (Cj0688) and ackA (Cj0689), although the acs homologue (Cj1537c) is not required. Insertion mutants in Cj0688 and Cj0689 maintain viability less well during the stationary and decline phases of the growth cycle than wild-type C. jejuni, suggesting that these genes, and the acetate pathway, are important for survival.

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