Search results for "SUBSTANCES"
showing 10 items of 1122 documents
Effect of EDTA and citrate on the functional activity of the first component of complement, C1, and the C1q subcomponent.
1985
The first component of complement, C1, is a calcium-dependent complex of the three distinct subcomponents, C1q, C1r, and C1s. Earlier observations revealed that treatment of C1 with EDTA led to a loss of hemolytic C1 activity even after recalcification. Therefore, it was of interest to study whether EDTA has an additional effect on C1 and its subcomponents, beside its chelating capacity. The chelating effect of EDTA was compared to that of citrate. It was found that treatment of C1 or C1 with EDTA followed by addition of Ca++ led to a loss of hemolytic activity up to 90%, depending on EDTA concentration. Even pretreatment of EDTA with varying amounts of Ca++ did not prevent the inactivation…
Chemical and catalytical properties of thermal polymers of amino acids (proteinoids)
1974
The significance of thermal polyamino acids (proteinoids) as abiotic predecessors of proteins is reviewed on the basis of new experimental results. Most proteinoids yield only 50% to 80% amino acid upon acid hydrolysis. They contain 40% to 60% less peptide links than typical proteins, whereas their average nitrogen content is like that of proteins. The arrangement of amino acid residues is nonrandom. The degree of nonrandomness is difficult to determine because unusual crosslinks disturb most of the sequencing methods typically applied in protein chemistry. The products obtained in a polymerization experiment are heterogeneous. They can be separated into a limited number of related fraction…
Preferential solvation of poly(methyl methacrylate) and a bisphenol A diglycidyl ether by size-exclusion chromatography
2004
The preferential adsorption coefficient, lambda, of poly(methyl methacrylate), PMMA, in solutions formed by an epoxy resin in tetrahydrofuran (THF), was studied by size-exclusion chromatography (SEC). Only PMMA of lowest molar mass was preferentially solvated by epoxy but at low concentrations of epoxy in the mixture. At higher epoxy content PMMA was preferentially solvated by THF. A simultaneous and competitive solvation between the specific interactions PMMA-epoxy and the self association of epoxy at high concentrations would be the responsible of this inversion point. The more compacted coil of PMMA of higher molecular weights in solution could explain the lack of interaction of these po…
Methods of in vitro toxicology
2002
In vitro methods are common and widely used for screening and ranking chemicals, and have also been taken into account sporadically for risk assessment purposes in the case of food additives. However, the range of food-associated compounds amenable to in vitro toxicology is considered much broader, comprising not only natural ingredients, including those from food preparation, but also compounds formed endogenously after exposure, permissible/authorised chemicals including additives, residues, supplements, chemicals from processing and packaging and contaminants. A major promise of in vitro systems is to obtain mechanism-derived information that is considered pivotal for adequate risk asses…
Proteins of Muscle and the Cytoskeleton
1994
The contractile elements of striated vertebrate skeletal muscle, the myofibrils, contain thin filaments, which are 6 nm in diameter and consist mainly of actin, and thicker myosin filaments with a diameter of 16 nm (Fig. 10.1). During muscle contraction, the filaments undergo a sliding movement relative to each other (sliding filament mechanism). This is brought about by the reversible formation of bridges between the myosin molecules and the actin filaments, which bind, change their conformation and then dissociate (bridge cycle). The required energy is supplied by the hydrolysis of ATP. The sliding distance (step size) per molecule of ATP hydrolysed is controversial; the most recent measu…
High Yield SNAr on 8-Halogenophenyl-BODIPY with Cyclic and Acyclic Polyamines
2014
Selective nucleophilic aromatic substitutions with several polyamines were performed in very good yields on halogeno-phenyl BODIPY derivatives containing an activating nitro group.
ChemInform Abstract: Sweet (Hetero)aromatics: Glycosylated Templated for the Construction of Saccharide Mimetics.
2011
Several general strategies for the construction of mono- and diglycosylated (hetero)aromatics as potential metabolically stable oligosaccharides are described.
The Relationship Between Attachment and Psychopathy: A Study with a Sample of Violent Offenders
2014
This study used a mixed quantitative-qualitative methodology to investigate the relationship between attachment and psychopathy. The Psychopathy Checklist- Revised (PCL-R; Hare 2003) was administered to 139 Italian offenders who were convicted of violent crimes (murder, rape, child sexual abuse, armed robbery, assault causing bodily harm). First, we explored whether the two PCL-R items theoretically denoting devaluation of attachment bonds (promiscuous sexual behavior and many marital relationships) were able to predict PCL-R total, factor and facet scores. Subse- quently, we analyzed the transcripts of the 10 participants who obtained the highest PCL-R scores in the sample, assessing their…
Circular and linear dichroism of aggregates of chlorophyll a and chlorophyll b in 3-methylpentane and paraffin oil.
1996
A circular (CD) and linear dichroism (LD) study of the water adducts of the green plant chlorophylls a (Chl a) and b (Chl b) in hydrocarbon solvents 3-methylpentane and paraffin oil is presented. A strong red shift of the Qy-absorption band from 663 to 746 nm (1678 cm−1) is observed as the water adduct of Chl a is formed. The Chl a-water adduct shows a strong, nonconservative CD signal, which is characterized by a positive peak at 748 nm and two negative peaks at 720 and 771 nm. The maximum CD (AL - AR) is only one order of magnitude smaller than the isotropic absorption maximum. We propose that this exceptionally strong signal is the so-called psi-type CD. The LD spectrum was measured in a…
Pigment Binding, Fluorescence Properties, and Oligomerization Behavior of Lhca5, a Novel Light-harvesting Protein
2005
A new potential light-harvesting protein, named Lhca5, was recently detected in higher plants. Because of the low amount of Lhca5 in thylakoid membranes, the isolation of a native Lhca5 pigment-protein complex has not been achieved to date. Therefore, we used in vitro reconstitution to analyze whether Lhca5 binds pigments and is actually an additional light-harvesting protein. By this approach we could demonstrate that Lhca5 binds pigments in a unique stoichiometry. Analyses of pigment requirements for light-harvesting complex formation by Lhca5 revealed that chlorophyll b is the only indispensable pigment. Fluorescence measurements showed that ligated chlorophylls and carotenoids are arran…