Search results for "binding"
showing 10 items of 3896 documents
Ion traps in nuclear physics—Recent results and achievements
2016
Abstract Ion traps offer a way to determine nuclear binding energies through atomic mass measurements with a high accuracy and they are routinely used to provide isotopically or even isomerically pure beams of short-living ions for post-trap decay spectroscopy experiments. In this review, different ion-trapping techniques and progresses in recent nuclear physics experiments employing low-energy ion traps are discussed. The main focus in this review is on the benefit of recent high accuracy mass measurements to solve some key problems in physics related to nuclear structure, nuclear astrophysics as well as neutrinos. Also, several cases of decay spectroscopy experiments utilizing trap-purifi…
Ion traps in nuclear physics : recent results and achievements
2016
Ion traps offer a way to determine nuclear binding energies through atomic mass measurements with a high accuracy and they are routinely used to provide isotopically or even isomerically pure beams of short-living ions for post-trap decay spectroscopy experiments. In this review, different ion-trapping techniques and progresses in recent nuclear physics experiments employing low-energy ion traps are discussed. The main focus in this review is on the benefit of recent high accuracy mass measurements to solve some key problems in physics related to nuclear structure, nuclear astrophysics as well as neutrinos. Also, several cases of decay spectroscopy experiments utilizing trap-purified ion sa…
Electron–phonon effects on the direct band gap in semiconductors: LCAO calculations
2002
Abstract Using a perturbative treatment of the electron–phonon interaction, we have studied the effect of phonons on the direct band gap of conventional semiconductors. Our calculations are performed in the framework of the tight-binding linear combination of atomic orbitals (LCAO) approach. Within this scheme we have calculated the temperature and isotopic mass dependence of the lowest direct band gap of several semiconductors with diamond and zincblende structure. Our results reproduce the overall trend of available experimental data for the band gap as a function of temperature, as well as give correctly the mass dependence of the band gap on isotopic. A calculation of conduction band in…
Imaging and force transduction in correlative scanning force and confocal fluorescence microscopy
2018
Correlative scanning force and confocal fluorescence microscopy has been used to study individual molecules, nanoparticles and nanoparticle oligomers. By applying a compressive force via the AFM cantilever, spectral blue and red shifts in the range of several meV/GPa have been observed for single dye molecules and semiconductor quantum dots. Moreover, individual Au nanoparticle dimers linked by a chlorophyll binding protein have been imaged in both modes and plasmonic fluorescence enhancement of the chlorophyll emission of up to a factor of 15 has been found.
What monomeric nucleotide binding domains can teach us about dimeric ABC proteins
2020
The classic conceptualization of ATP binding cassette (ABC) transporter function is an ATP-dependent conformational change coupled to transport of a substrate across a biological membrane via the transmembrane domains (TMDs). The binding of two ATP molecules within the transporter's two nucleotide binding domains (NBDs) induces their dimerization. Despite retaining the ability to bind nucleotides, isolated NBDs frequently fail to dimerize. ABC proteins without a TMD, for example ABCE and ABCF, have NBDs tethered via elaborate linkers, further supporting that NBD dimerization does not readily occur for isolated NBDs. Intriguingly, even in full-length transporters, the NBD-dimerized, outward-…
Physicochemical and functional characterization of the polymerization process of the Geodia cydonium lectin
1985
The extracellularly localized, galactose-specific lectin from the sponge Geodia cydonium binds at one class of sites, 40 mol Ca2+/mol lectin with an association constant (Ka) of 0.3 X 10(6)M-1. Stoichiometric calculations reveal that in the extracellular milieu 22 mol Ca2+ (maximum) are complexed per mol lectin. Binding of Ca2+ to the lectin increases its apparent Mr from 44000 to 56000 (electrophoretic determination) or from 36500 to 53500 (high-pressure liquid gel chromatographical determination); the s20, w increases from 4.3 S to 4.5 S if Ca2+ is added to the lectin. In the presence of Ca2+ the lectin undergoes a conformational change perhaps by expanding the carbohydrate side chains wh…
A closer look at the cholesterol sensor
2002
Abstract Transport of the sterol regulatory element-binding protein (SREBP) cleavage-activating protein (SCAP)–SREBP complex from the endoplasmic reticulum (ER) to the Golgi is the central event mediating the cholesterol-feedback process in mammalian cells. A conformational change in SCAP is a crucial step; when cholesterol levels are high, the conformation of SCAP enables the SCAP–SREBP complex to associate with an insulin-induced gene (INSIG) retention protein in the ER. By contrast, when cholesterol levels are low, SCAP switches to a conformation that enables the dissociation of the retention protein and the association of SCAP–SREBP with COP II vesicles.
Decipher the mechanisms of protein conformational changes induced by nucleotide binding through free-energy landscape analysis: ATP binding to Hsp70.
2013
ATP regulates the function of many proteins in the cell by transducing its binding and hydrolysis energies into protein conformational changes by mechanisms which are challenging to identify at the atomic scale. Based on molecular dynamics (MD) simulations, a method is proposed to analyze the structural changes induced by ATP binding to a protein by computing the effective free-energy landscape (FEL) of a subset of its coordinates along its amino-acid sequence. The method is applied to characterize the mechanism by which the binding of ATP to the nucleotide-binding domain (NBD) of Hsp70 propagates a signal to its substrate-binding domain (SBD). Unbiased MD simulations were performed for Hsp…
Interaction ofEscherichia colihemolysin with biological membranes
2001
Escherichia coli hemolysin (HlyA) is a membrane-permeabilizing protein belonging to the family of RTX-toxins. Lytic activity depends on binding of Ca2(+) to the C-terminus of the molecule. The N-terminus of HlyA harbors hydrophobic sequences that are believed to constitute the membrane-inserting domain. In this study, 13 HlyA cysteine-replacement mutants were constructed and labeled with the polarity-sensitive fluorescent probe 6-bromoacetyl-2-dimethylaminonaphthalene (badan). The fluorescence emission of the label was examined in soluble and membrane-bound toxin. Binding effected a major blue shift in the emission of six residues within the N-terminal hydrophobic domain, indicating inserti…
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 …