ABSTRACT
The reactivity of two fluorescent derivatization reagents, 2-diphenyl-1,3-indandione-1-hydrazone (DIH) and 2-aminooxy-N-[3-(5-dimethylamino-naphtalene-1-sulfonamino)-propyl]-acetamide (dansylacetamidooxyamine, DNSAOA), was studied towards selected atmospheric carbonyl compounds. The results were compared to those obtained using the 2,4-dinitrophenylhydrazine (2,4-DNPH) UV-vis reagent, a standard well-established technique used to detect atmospheric carbonyl compounds. The experimental rate constant were integrated into a data-processing model developed in the laboratory to simulate the trapping efficiencies of a mist chamber device as a function of temperature, reagent and solvent type among others. The results showed that in an aqueous solution, DNSAOA exhibits a higher reactivity towards carbonyl compounds without the addition of an acidic catalyst than 2,4-DNPH. It was observed that DNSAOA can trap efficiently water-soluble gaseous compounds (for example formaldehyde). However, because of a high initial contamination of the reagent caused by the synthesis procedure used in this work, DNSAOA cannot be used in high concentrations. As a result, very low trapping efficiencies of less reactive water-insoluble gaseous compounds (acetone) using DNSAOA are observed. However, the use of an organic solvent such as acetonitrile improved the trapping efficiencies of the carbonyl compounds. In this case, using DIH as the derivatization reagent (DNSAOA is not soluble in acetonitrile), trapping efficiencies greater than 95% were obtained, similar to 2,4-DNPH. Moreover, fluorescence associated with DIH derivatives (detection limits 3.33 x 10(-8)M and 1.72x10(-8)M for formaldehyde and acetone, respectively) is further advantage of this method for the determination of carbonyl compounds in complex matrix compared to the classical UV-vis detection method (detection limits 3.20 x 10(-8)M and 2.9 x 10(-8)M for formaldehyde and acetone, respectively).
ABSTRACT
The colonization of land by eukaryotes probably was facilitated by a partnership (symbiosis) between a photosynthesizing organism (phototroph) and a fungus. However, the time when colonization occurred remains speculative. The first fossil land plants and fungi appeared 480 to 460 million years ago (Ma), whereas molecular clock estimates suggest an earlier colonization of land, about 600 Ma. Our protein sequence analyses indicate that green algae and major lineages of fungi were present 1000 Ma and that land plants appeared by 700 Ma, possibly affecting Earth's atmosphere, climate, and evolution of animals in the Precambrian.
Subject(s)
Biological Evolution , Chlorophyta , Fungal Proteins/chemistry , Fungi , Chlorophyta/genetics , Chlorophyta/growth & development , Databases, Factual , Ecosystem , Fossils , Fungal Proteins/genetics , Fungi/chemistry , Fungi/genetics , Fungi/growth & development , Phylogeny , Plants/genetics , Rhodophyta/genetics , Rhodophyta/growth & development , Sequence Alignment , Sequence Analysis, Protein , Symbiosis , TimeABSTRACT
A literature survey of carbohydrate sonochemistry is presented. The basic physical principles are discussed qualitatively before the main applications are reviewed. Along with other non-classical activation methods developed in accordance with 'Green Chemistry' requirements, ultrasonic irradiation offers important potential for the conversion of biomass raw materials such as polymeric carbohydrates to useful lower weight molecules. A number of reactions involving mono- or disaccharides, considered as a renewable source of fine chemicals, can also be performed with ultrasonic activation. This is the case for glycosylation, acetalization, oxidation, C-D, C-heteroatom, and C-C bond formations, which are improved in terms of reaction rates and yields and, in some instances, in their chemo-, regio- and stereoselectivities. The equipment available is briefly described, and practical considerations are given.
Subject(s)
Carbohydrates/chemistry , Chemistry, Organic/methods , Sonication , Biopolymers/chemistry , Carbon/chemistry , Cellulose/chemistry , Deuterium/chemistry , Dextrans/chemistry , Disaccharides/chemistry , Glycosylation , Hydrolysis , Lactose/chemistry , Oxidation-Reduction , Polysaccharides/chemistry , Reactive Oxygen Species , Sonication/instrumentation , Starch/chemistry , Stress, Mechanical , Sucrose/chemistry , TemperatureABSTRACT
Binding of aminocyclitol antibiotics to intestinal and kidney brush border membranes has been studied in vitro by means of vesicular preparations. The binding is rapid, reversible, specific, saturable and has a high affinity. To both tissues, gentamicin and sisomicin bind to a single binding site or receptor. These antibiotics demonstrate increased binding under conditions of increasing pH. Membrane binding disappears when the vesicle proteins are denatured with TCA. A significant reduction in aminocyclitol binding after treatment of vesicles with papain indicates that a portion of the binding receptor protein is exposed to the outer surface of the brush border membrane. The accumulated evidence suggests that the nature of the binding mechanism is not a simple electrostatic interaction between the antibiotic's charged amino groups and the polyanions of the membrane. Alternatively, a specific membrane structure is required for binding whose characteristics reflect a drug-receptor interaction. Receptor binding is characterized as being saturable, reversible, and specific; all of which have been demonstrated for aminocyclitols and brush border membranes.
