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At least 847 records · Page 47Linked to original sources
PubMed2001

Na/K-ATPase as an oligomeric ensemble.

Differences in the kinetic behavior and properties of monomeric and oligomeric forms of membrane-bound Na/K-ATPase are analyzed. It is concluded that enzyme molecules within oligomeric complexes are affected by extrinsic signals that result in change of enzyme activity, whereas the individual (protomeric) state is insensitive to these signals. Some of the major factors of such regulation are microviscosity of the lipid environment, reactive oxygen species, and intracellular protein kinases.

Adenosine Triphosphate↗
PubMed2004

Sequential rearrangements of the ensemble activity of putamen neurons in the monkey brain as a correlate of continuous behavior.

Simultaneous recordings were made of the spike activity of groups of 6-7 neurons in the putamen in two monkeys (Macaca nemestrina and Macaca mulatta) during performance of alternative spatial selection. Discriminant analysis was used to evaluate the magnitude of rearrangements in spike activity in groups of neurons during transitions from each step of the behavioral program to the next, along with the degree of differences in reactivity mosaics formed at each step in different versions of task execution. Rearrangements in spike activity were noted at all steps of the program. The dynamics of rearrangements on selection of the right and left feeders were different, leading to the appearance of significant differences in the reactivity mosaics at the decision-taking and reinforcement-receiving steps. The rearrangements preceding voluntary movement of one hand were more marked in the contralateral hemisphere. During performance of movements, the volume of rearrangements could increase, though differences in rearrangements accompanying movements of the right and left hands decreased. On receipt of reinforcement, rearrangements were greater when the animals selected a specified feeder (the left feeder) independently of which hemisphere was recorded.

Action Potentials↗
PubMed2004

Direct access to the cooperative substructure of proteins and the protein ensemble via cold denaturation.

The modern view of protein thermodynamics predicts that proteins undergo cold-induced unfolding. Unfortunately, the properties of proteins and water conspire to prevent the detailed observation of this fundamental process. Here we use protein encapsulation to allow cold denaturation of the protein ubiquitin to be monitored by high-resolution NMR at temperatures approaching -35 degrees C. The cold-induced unfolding of ubiquitin is found to be highly noncooperative, in distinct contrast to the thermal melting of this and other proteins. These results demonstrate the potential of cold denaturation as a means to dissect the cooperative substructures of proteins and to provide a rigorous framework for testing statistical thermodynamic treatments of protein stability, dynamics and function.

Algorithms↗
PubMed2003

A topologically new ruthenium porphyrin-fullerene donor-acceptor ensemble.

A novel ruthenium porphyrin complex bearing an axially coordinated fullerene ligand (RuP-C60), that is, a fulleropyrrolidine that bears a pyridine moiety, was developed as an artificial reaction center mimic. Generally, the new donor acceptor dyad gives rise to rapid intramolecular deactivation of the ruthenium porphyrin triplet excited state, which evolves from instantaneous intersystem crossing. The product of the ruthenium porphyrin excited-state deactivation depends on the solvent polarity. While in non-polar solvents a transduction of triplet excited energy predominates, in medium and strongly polar media, charge-separation leads to the formation of RuP*+ C60*-.

Journal Article↗
PubMed2004

Design and synthesis of multi-component 18 pi annulenic fluorofullerene ensembles suitable for donor-acceptor applications.

A series of trannulene (all-trans annulene) derivatives of [60]fullerene have been prepared by reacting C(60)F(18) with methanetricarboxylate esters that incorporate a range of photoactive functions. All the compounds have the intense emerald-green colour of fullerene trannulenes, characterised by strong bands at ca. 612 and 667 nm. Single crystal X-ray studies show that the packing varies with the nature of the addend, attributable to differing steric effects. UV/vis absorption spectra display transitions of the respective fullerene and addend models, indicating absence of electronic interactions between them in the ground state. These now provide an extensive series for testing photoactive (light-harvesting) properties, with the exceptional properties of having strong visible light absorption. Their exceptional stability is attributed to the 18[small pi] aromatic circuit, inability to undergo nucleophilic substitution without disrupting this circuit, and a curved cage region that is shielded to reagents by the three bulky addends.

Journal Article↗
PubMed1998

Dynamical ensembles in nonequilibrium statistical mechanics and their representations.

The stationary states of driven systems of particles are considered from the point of view of the invariant probability distributions in the phase space which characterize them. The main features of various representations of such distributions are reviewed, and a brief derivation of the one based on orbital measures is given. We mention the limits of the mathematical derivations, and discuss the expected range of applicability beyond such limits. (c) 1998 American Institute of Physics.

Journal Article↗