Search results for "Quaternary"
showing 10 items of 411 documents
The Allosteric Effector l-Lactate Induces a Conformational Change of 2×6-meric Lobster Hemocyanin in the Oxy State as Revealed by Small Angle X-ray S…
2001
Abstract Hemocyanins are multisubunit respiratory proteins found in many invertebrates. They bind oxygen highly cooperatively. However, not much is known about the structural basis of this behavior. We studied the influence of the physiological allosteric effectorl-lactate on the oxygenated quaternary structure of the 2×6-meric hemocyanin from the lobster Homarus americanus employing small angle x-ray scattering (SAXS). The presence of 20 mm l-lactate resulted in different scattering curves compared with those obtained in the absence of l-lactate. The distance distribution functionsp(r) indicated a more compact molecule in presence ofl-lactate, which is also reflected in a reduction of the …
Small-angle neutron scattering reveals an oxygen-dependent conformational change of the immunogen keyhole limpet hemocyanin type 1 (KLH1).
2001
The respiratory protein of the keyhole limpet, Megathura crenulata, the hemocyanin (KLH), commonly used as an immunogen, binds oxygen cooperatively, which implies the existence of different conformations. For the first time, two different conformations of KLH1 were detected upon oxygenation, a deoxy and an oxy state, using small-angle neutron scattering. Rearrangements in the quaternary structure of KLH1 were predicted from the different radii of gyration and the shifts of the minima and maxima in the scattering curves. Upon oxygenation, KLH1 becomes smaller and more compact. Model reconstruction of KLH1 indicates a hollow cylinder with two rings located close to both ends, which move sligh…
Ecological implications of Cousinia Cass. (Asteraceae) persistence through the last two glacial–interglacial cycles in the continental Middle East fo…
2012
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Quaternary structure and molecular model of a 4x6mer arthropod hemocyanin in oxygenated and deoxygenated states by 3D cryo-electron microscopy
2007
Extended abstract of a paper presented at MC 2007, 33rd DGE Conference in Saarbrücken, Germany, September 2 – September 7, 2007
Quaternary transition pathway in sol–gel encapsulated haemoglobin tracked by NIR and UV spectral relaxations
2008
→T structural transition of haemoglobin (hb), the protein responsible for oxygen (o) transport in the red blood cells of vertebrates, is the hall mark example. This transition, which regu lates o2 uptake in the lungs and o2 release in the tissues, is a switch in the quaternary structure of the protein from a low-affinity state (T) to a high-affinity state (R), two well-characterised structures. The struc tural pathway connecting the end states of this transition remains unclear, however, although recently several experimental 1 or
On the generation and degradation of emerged coral reef terrace sequences: First cosmogenic 36Cl analysis at Cape Laundi, Sumba Island (Indonesia)
2021
(IF 4.45: Q1); International audience; The emerged coral reef terrace sequence at Cape Laundi, on the north coast of Sumba Island (Indonesia), with at least 18 successive strandlines, remains poorly dated in spite of numerous previous data. The age discrepancies within these coral reef terraces (CRTs) were previously explained by their polycyclic nature, triggered by marine erosion and reoccupation of old coral colonies by new ones. This study aims at highlighting these processes, as well as the continental denudation that participates in the partial stripping of the thin superficial coral reef layer overlying the pre-existing surface, exhuming older coral colonies. For this purpose, we use…
A microanalytical method for ammonium and short-chain primary aliphatic amines using precolumn derivatization and capillary liquid chromatography.
2007
Abstract A new microscale method is presented for the determination of ammonium and primary short-chain aliphatic amines (methylamine, ethylamine, propylamine, n -butylamine and n -pentylamine) in water. The assay uses precolumn derivatization with the reagent o -phthaldialdehyde (OPA) in combination with the thiol N -acetyl- l -cysteine (NAC), and capillary liquid chromatography with UV detection at 330 nm. The described method is very simple and rapid as no preconcentration of the analytes is necessary, and the volume of sample required is only 0.1 mL. Under the proposed conditions good linearity has been obtained up to a concentration of the analytes of 10.0 mg L −1 , the limits of detec…
Pulsed EPR determination of water accessibility to spin-labeled amino acid residues in LHCIIb.
2009
Membrane proteins reside in a structured environment in which some of their residues are accessible to water, some are in contact with alkyl chains of lipid molecules, and some are buried in the protein. Water accessibility of residues may change during folding or function-related structural dynamics. Several techniques based on the combination of pulsed electron paramagnetic resonance (EPR) with site-directed spin labeling can be used to quantify such water accessibility. Accessibility parameters for different residues in major plant light-harvesting complex IIb are determined by electron spin echo envelope modulation spectroscopy in the presence of deuterated water, deuterium contrast in …
The biological activity of bacteriophage DNA, prepared by the cationic detergent dilution technique
1975
Abstract The preparation of phage lambda DNA infecting E. coli K 12 with cationic detergent is described. This DNA infects E. coli spheroblasts with the same efficiency as DNA prepared by phenol methods.
Identification problems of arid environments in the Neogene–Quaternary mammal record of Spain
2006
Abstract In this work, we investigate if broadly used methodologies are adequate to detect periods of aridity based on the Spanish fossil record and try to infer which of them were more or less severe. Thus, we present a qualitative statistical approach to two popular palaeoecological methodologies: ecological diversity and cenograms. Discriminant models, derived from modern localities of known biome, determined the probable biomes of Neogene–Quaternary fossil assemblages. Principal component analyses (PCA) provided additional inference on their ordination within an aridity gradient. While models work adequately with modern faunas, the analyses of the palaeocommunities showed that their eco…