Search results for "Macromolecular Substance"

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…

Exchange of Pigment-Binding Amino Acids in Light-Harvesting Chlorophyll a/b Protein

1999

Four amino acids in the major light-harvesting chlorophyll (Chl) a/b complex (LHCII) that are thought to coordinate Chl molecules have been exchanged with amino acids that presumably cannot bind Chl. Amino acids H68, Q131, Q197, and H212 are positioned in helixes B, C, A, and D, respectively, and, according to the LHCII crystal structure [Kühlbrandt, W., et al. (1994) Nature 367, 614-621], coordinate the Chl molecules named a(5), b(6), a(3), and b(3). Moreover, a double mutant was analyzed carrying exchanges at positions E65 and H68, presumably affecting Chls a(4) and a(5). All mutant proteins could be reconstituted in vitro with pigments, although the thermal stability of the resulting mut…

Horseradish peroxidase-catalyzed oxidation of chlorophyll a with hydrogen peroxide Characterization of the products and mechanism of the reaction

AbstractHorseradish peroxidase was verified to catalyze, without any phenol, the hydrogen peroxide oxidation of chlorophyll a (Chl a), solubilized with Triton X-100. The 132(S) and 132(R) diastereomers of 132-hydroxyChl a were characterized as major oxidation products (ca. 60%) by TLC on sucrose, UV–vis, 1H, and 13C NMR spectra, as well as fast-atom bombardment MS. A minor amount of the 152-methyl, 173-phytyl ester of Mg-unstable chlorin was identified on the basis of its UV–vis spectrum and reactivity with diazomethane, which converted it to the 131,152-dimethyl, 173-phytyl ester of Mg-purpurin 7. The side products (ca. 10%) were suggested to include the 173-phytyl ester of Mg-purpurin 18,…

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…

Localization of the N-terminal Domain in Light-harvesting Chlorophyll a/b Protein by EPR Measurements

2005

The conformational distribution of the N-terminal domain of the major light-harvesting chlorophyll a/b protein (LHCIIb) has been characterized by electron-electron double resonance yielding distances between spin labels placed in various domains of the protein. Distance distributions involving residue 3 near the N terminus turned out to be bimodal, revealing that this domain, which is involved in regulatory functions such as balancing the energy flow through photosystems (PS) I and II, exists in at least two conformational states. Models of the conformational sub-ensembles were generated on the basis of experimental distance restraints from measurements on LHCIIb monomers and then checked f…