Search results for "AMMONIUM"
showing 10 items of 1070 documents
Direct experimental observation of mesoscopic fluorous domains in fluorinated room temperature ionic liquids
2017
Fluorinated room temperature ionic liquids (FRTILs) represent a class of solvent media that are attracting great attention due to their IL-specific properties as well as features stemming from their fluorous nature. Medium-to-long fluorous tails constitute a well-defined apolar moiety in the otherwise polar environment. Similarly to the case of alkyl tails, such chains are expected to result in the formation of self-assembled fluorous domains. So far, however, no direct experimental observation has been made of the existence of such structural heterogeneities on the nm scale. We report here the first experimental evidence of the existence of mesoscopic spatial segregation of fluorinated dom…
An operon for histidine biosynthesis in Streptomyces coelicolor
1973
On the assumption that a cluster of five his genes (eight cistrons) in S. coelicolor corresponds to an operon, a genetic analysis of a constitutive mutant was carried out. This strain has a multi-site mutation localized at the (conventional) right end of the his cluster and is derepressed for at least two enzymes coded by genes of the cluster. The study of suitable heterozygous clones (heteroclones), showed the mutation to be cis-dominant, suggesting that the operator region is affected. Most likely the strain has a deletion connecting the his operon to an adjacent amm (ammonium requirement) operon as demonstrated by its inability to utilize nitrate as nitrogen source and to complement or r…
The Effect of Phosphinothricin (Glufosinate) on Photosynthesis II. The Causes of Inhibition of Photosynthesis
1987
It was shown in the previous study that phosphinothricin (glufosinate) causes an accumulation of ammonia and inhibition of photosynthesis. The extent to which there is a connection between these two processes is now investigated in the present study. First of all. the role of NH3 per se in the impairment of photosynthesis was to be clarified. For this purpose, the inhibition of photosynthesis was investigated in relation to exogenously applied ammonia in chloroplasts, protoplasts and entire leaves. The comparison with the experimental results in leaves in which the ammonia was formed endogenously (by action of phosphinothricin) shows that the ammonia toxicity at least cannot be solely resp…
Extraction of glyphosate by a supported liquid membrane technique.
2000
The possible application of the supported liquid membrane (SLM) technique for the extraction of glyphosate is presented. For the extraction of this compound the SLM system has been applied with utilisation of Aliquat 336 as a cationic carrier incorporated into the membrane phase. The extraction efficiency of glyphosate [N-(phosphonomethyl)glycine] is dependent on the donor phase pH, carrier concentration in the organic phase and NaCl concentration in the acceptor phase. The optimal extraction conditions are: donor phase pH>11, acceptor phase of 2 M NaCl solution and the organic phase composed of 20% (w/w) Aliquot 336 solution in di-hexyl ether. Counter-coupled transport of chloride anions f…
tert-Butoxyl radicals generate mainly 7,8-dihydro-8-oxoguanine in DNA.
2000
Abstract Like hydroxyl radicals, alkoxyl radicals have been implicated in the generation of cellular oxidative DNA damage under physiological conditions; however, their genotoxic potential has not yet been established. We have analyzed the DNA damage induced by a photochemical source of tert- butoxyl radicals, the water soluble peroxy ester [4-( tert -butyldioxycarbonyl)benzyl]triethylammonium chloride (BCBT), using various repair endonucleases as probes. The irradiation (UV 360 ) of BCBT in the presence of bacteriophage PM2 DNA was found to generate a DNA damage profile that consisted mostly of base modifications sensitive to the repair endonuclease Fpg protein. Approximately 90% of the mo…
THE EFFECT OF GADOLINIUM ON THE ESR RESPONSE OF ALANINE AND AMMONIUM TARTRATE EXPOSED TO THERMAL NEUTRONS
2008
Many efforts have been made to develop neutron capture therapy (NCT) for cancer treatment. Among the challenges in using NCT is the characterization of the features of the mixed radiation field and of its components. In this study, we examined the enhancement of the ESR response of pellets of alanine and ammonium tartrate with gadolinium oxide exposed to a thermal neutron beam. In particular, the ESR response of these dosimeters as a function of the gadolinium content inside the dosimeter was analyzed. We found that the addition of gadolinium improves the sensitivity of both alanine and ammonium tartrate. However, the use of gadolinium involves a reduces in or abolishes tissue equivalence b…
Different effectors of dimorphism in Yarrowia lipolytica
2002
Yarrowia lipolytica is an ascomycete with biotechnological potential. In common media, the fungus grows as a mixture of yeast-like and short mycelial cells. The environmental factors that affect dimorphism in the wild-type strain, W29, and its auxotrophic derivative, PO1a, were analyzed. In both strains, pH was the most important factor regulating the dimorphic transition. Mycelium formation was maximal at pH near neutrality and decreased as pH was lowered to become almost null at pH 3. Carbon and nitrogen sources, namely glucose and ammonium, were also important for mycelium formation; and their effect was antagonized by some alternative carbon and nitrogen sources. Citrate was an importan…
Novel cationic polyaspartamide with covalently linked carboxypropyl-trimethyl ammonium chloride as a candidate vector for gene delivery
2006
Abstract The non-viral gene vector properties of a protein-like polymer, the α,β-poly(N-2-hydroxyethyl)- d , l -aspartamide (PHEA) were investigated after its derivatization with 3-(carboxypropyl)trimethyl-ammonium chloride (CPTA) as molecule bearing cationic groups, in order to obtain stable polycations able to condense DNA. PHEA was firstly functionalized with hydrazide pendant groups by reaction with hydrazine monohydrate (HYD), obtaining the polyhydrazide α,β-poly(N-2-hydroxyethyl/carbazate)- d , l -aspartamide (PHEA–HYD). In this paper we reported that polymer functionalization degree can be easily modulated by varying reaction conditions, so allowing us to produce two PHEA derivatives…
Structural Versatility of Anion−π Interactions in Halide Salts with Pentafluorophenyl Substituted Cations
2008
A series of pentafluorophenyl substituted ammonium, iminium, amidinium, and phosphonium halides are presented which show extensive anion-pi interactions. Hereby, the well-known anion-donor-pi-acceptor as well as "eta6" anion-pi-complex type interactions are observed. The latter is supported by fixation of the anion on top of the aromatic system through hydrogen bonding. This arrangement was investigated by theoretical methods showing a highly attractive anion-pi interaction. In addition an eta2-type coordination of the anions to only two C-atoms of the electron-deficient ring system is described.
Comparison of the behaviour of three herbicides in a field experiment under bare soil conditions
2006
Abstract A case-study was design in order to rank three alternative herbicides according to their exposure to surface waters. Herbicide persistence and losses to surface waters were studied in an uncultivated Finnish field (ca. 3500 m2, slope