Search results for "compounds"
showing 10 items of 3372 documents
Water-Soluble Chlorophyll Protein (WSCP) Stably Binds Two or Four Chlorophylls
2017
Water-soluble chlorophyll proteins (WSCPs) of class IIa from Brassicaceae form tetrameric complexes containing one chlorophyll (Chl) per apoprotein but no carotenoids. The complexes are remarkably stable toward dissociation and protein denaturation even at 100 °C and extreme pH values, and the Chls are partially protected against photooxidation. There are several hypotheses that explain the biological role of WSCPs, one of them proposing that they function as a scavenger of Chls set free upon plant senescence or pathogen attack. The biochemical properties of WSCP described in this paper are consistent with the protein acting as an efficient and flexible Chl scavenger. At limiting Chl concen…
Influence of Feeding and Oviposition by Phytophagous Pentatomids on Photosynthesis of Herbaceous Plants
2010
Abstract Feeding by herbivorous insects may change photosynthetic activity of host plants. We studied how feeding and oviposition by herbivorous stink bugs, Murgantia histrionica and Nezara viridula (Heteroptera: Pentatomidae), affect photosynthetic parameters of Brassica oleracea (savoy cabbage) and Phaseolus vulgaris (French bean). First, we measured photosynthetic gas exchange, chlorophyll fluorescence imaging, and emission of induced volatile organic compounds (VOC) immediately after feeding and during a post-feeding period. Photosynthesis decreased rapidly and substantially in B. oleracea and P. vulgaris infested by feeding bugs. Stomatal conductance did not decrease proportionally wit…
Displacement of phenprocoumon (Marcumar) from albumin by sulfonylurea compounds, suramin, and ioglycamic acid.
1972
The technique of Sephadex gel filtration was employed to characterize the effect of some sulfonylurea compounds, ioglycamic acid, and suramin on the binding of phenprocoumon to bovine serum albumin.
Determination of cholesterol in human milk: an alternative to chromatographic methods
2015
Introduction: human milk (HM) is considered the best option for feeding healthy infants. Cholesterol (CHOL) is important for proper development of the nervous system, and for hormone and vitamin synthesis in growing infants. Breastfeeding and dietary CHOL intake during infancy have been suggested to affect blood lipid levels and the risk of cardiovascular disease in adulthood. Gas chromatography is the technique most widely used to determine CHOL in HM. Chromatographic methods are specific for the determination of CHOL and other sterols present in HM, but are extremely time consuming, and the costs and equipment requirements mean that they are not accessible to all laboratories. Aim: the pr…
A Method to Quantitatively Trap Volatilized Organoselenides for Stable Selenium Isotope Analysis
2011
If volatile organoselenides are to be analyzed for their stable Se isotope composition to elucidate sources and formation processes, organoselenides need to be trapped quantitatively to avoid artificial Se isotope fractionation. We developed an efficient trap of organoselenides to be used in microcosms designed to determine the Se isotope fractionation by microbial transformation of inorganic Se to volatile organoselenides. The recoveries of volatilized dimethyldiselenide (DMDSe) from aqueous standard solutions by activated charcoal and alkaline peroxide solution with subsequent freeze-drying and purification via a cation exchange resin were tested. Microcosm experiments with the Se-methyla…
Influence of ground tire rubber on the transient loading response of a peat biofilter
2010
Abstract The effect of using ground tire rubber (GTR) as an adsorptive material in the removal of a 2:1:1 weight mixture of n-butyl acetate, toluene and m-xylene by using a peat biofilter under different intermittent conditions was investigated. The performance of two identical size biofilters, one packed with fibrous peat alone and the other with a 3:1 (vol) fibrous peat and GTR mixture, was examined for a period of four months. Partition coefficients of both materials were measured. Values of 53, 118 and 402 L kg −1 were determined for n-butyl acetate, toluene and m-xylene in peat, respectively; and values of 40, 609 and 3035 L kg −1 were measured for the same compounds in GTR. Intermitte…
Simultaneous analysis of lysine, Nɛ-carboxymethyllysine and lysinoalanine from proteins
2007
Protein quality was assayed by simultaneous measurement of lysine (Lys), carboxymethyllysine (CML) and lysinoalanine (LAL). GC-FID analysis of N-tert-butyl dimethylsilyl (tBDMSi) derivatives of these amino acids was undertaken. tBDMSi derivates were separated on a CP-SIL 5CB commercially fused silica capillary column (25 m × 0.25 mm i.d., 0.25 μm film thickness) employing a thermal gradient programmed from 200 to 300 °C. The identity of tBDMSi derivatives of Lys, CML and LAL was established by GC–MS while FID detection was employed for quantification. Analytical parameters such as linearity (lysine 350–4200 μM, LAL 3–81 μM, CML 16–172 μM), precision (1–13% variation coefficients), accuracy …
Volatile compounds of flowers and leaves of Sideritis italica (Miller)Greuter et Burdet (Lamiaceae), a plant used as mountain tea
2010
Sideritis italica (Miller) Greuter et Burdet (Lamiaceae), widely used in ethnopharmacological medicine, occurs in Southern Italy and Sicily. The phytochemical composition of the essential oils of S. italica flowers and leaves, harvested in Piano Battaglia (Sicily), was analysed by GC and GC-MS. Of the 51 compounds, 43 in the oil from flowers and 29 in the oil from leaves were identified. Kaur-15-ene (20.0%) was recognised as the main constituent of the oil from flowers, together with beta-cubebene (12.1%), beta-pinene (8.5%), (Z)-nuciferol (6.5%), tricyclene (4.5%) and alpha-bisabolol (4.0%). In the oil from leaves, p-methoxyacetophenone (26.0%) prevailed, as did hexadecanoic acid (21.3%), …
Determination of 2,3,7,8-tetrachlorodibenzo-p-dioxin in goat milk and tissues by glass capillary gas chromatography and medium resolution mass fragme…
1981
Abstract An analytical method has been developed for the study of the elimination of 2,3,7,8-tetrachlodoribenzo-p-dioxin (TCDD) by lactation and its determination in various tissues of goat. The method is based on the alkaline hydrolysis of milk, liver, fat, muscle, blood, faeces and urine samples, extraction with n-hexane, treatment with sulphuric acid-saturated silica gel, chromatographic clean-up on silica gel and alumina micro-columns, and glass capillary gas chromatography—medium resolution mass fragmenography (resolution 2000). 1,2,3,4-Tetrachlorodibenzo-p-dioxin is used as the internal standard, the concentration of TCDD being determined from the calibration curve calculated from the…
Gas chromatographic and mass spectrometric analysis of chlorinated catechols occurring in pulp bleach liquors
1982
Chlorination step (C-step), spent bleach liquor from a kraft pulp mill and the product from the chlorination of guaiacol in aqueous solution have been investigated for their content of chlorinated catechols. After separation the samples were derivatized with diazoethane and analysed by glass capillary gas chromatography with an electron capture detector. The external standard mixture of all ethylated chlorocatechols was used in the measurements. The structures of the compounds identified were confirmed by gas chromatography/mass spectrometry. Eight chlorinated catechols were identified from a sample prepared by chlorination of guaiacol with Cl2 in aqueous solution. However, only four of the…