Model-facilitated cooperative behavior in regressed schizophrenics.
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Cooperative Behavior↗
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COOPERATIVE BEHAVIOR IN A MIXED-MOTIVE GAME.
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Adolescent↗
Cooperative behavior in dyads as a function of reinforcement parameters.
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Cooperative Behavior↗
Deciding to defect: the effects of video-game violence on cooperative behavior.
This experiment examined the effect of video-game violence on cooperative decision making. Participants (N= 48) were randomly assigned to play either a violent or a nonviolent version of the video game Doom in dyads. Following the video-game task, participants were separated and given an opportunity to choose to cooperate with their partner for mutual gain, withdraw from the interaction, or exploit their partner for their own benefit. Participants in the violent condition were significantly more likely to choose to exploit their partners than participants in the nonviolent condition. These findings suggest that playing violent video games may undermine prosocial motivation and promote exploitive behavior in social interactions.
Cooperative Behavior↗
EFFECTS OF PUNISHMENT ON A COOPERATIVE BEHAVIOR IN CHILDREN.
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Black People↗
Cooperative behavior of K+ channels in the tonoplast of Chara corallina.
Spontaneous cooperatively of K+ channels is studied in excised patches of Chara corallina tonoplasts. Bar histograms (dwell time versus number of open channels) are constructed from the time series of current by means of the higher-order Hinkley detector (R. Schultze and S. Draber. 1993. J. Membr. Biol. 132:41-52). A statistical test, based on these bar histograms, shows that the channels are not independent. Further analysis reveals that the channels are cooperatively changing their open probability, which leads to the idea of cooperative mode shifting.
Biophysical Phenomena↗
The group engagement model: procedural justice, social identity, and cooperative behavior.
The group engagement model expands the insights of the group-value model of procedural justice and the relational model of authority into an explanation for why procedural justice shapes cooperation in groups, organizations, and societies. It hypothesizes that procedures are important because they shape people's social identity within groups, and social identity in turn influences attitudes, values, and behaviors. The model further hypothesizes that resource judgments exercise their influence indirectly by shaping social identity. This social identity mediation hypothesis explains why people focus on procedural justice, and in particular on procedural elements related to the quality of their interpersonal treatment, because those elements carry the most social identity-relevant information. In this article, we review several key insights of the group engagement model, relate these insights to important trends in psychological research on justice, and discuss implications of the model for the future of procedural justice research.
Anger↗
Second to fourth digit ratio and cooperative behavior.
A low second to fourth digit ratio (2D:4D) has been related to high testosterone levels and to markers of high status. In a social dilemma context status can be obtained either by acting egoistically (i.e. not contributing one's share) or by acting altruistically (i.e. contributing more than one's fair share). We therefore predicted that a low 2D:4D would be associated with high levels of egoism and altruism and low levels of common cooperativeness (i.e. contributing exactly one's fair share). We found the exact opposite: participants with a low 2D:4D were more likely to act cooperatively and less likely to act altruistically and egoistically. These findings suggest that: (1) there might be a high and a low testosterone strategy to gain status and (2) the high testosterone strategy is characterized by a preference for normative behavior.
Adolescent↗
Effect of glycerol on glucokinase activity: loss of cooperative behavior with respect to glucose.
Glucose phosphorylation catalyzed by rat liver glucokinase measured at saturating concentrations of MgATP2- shows a cooperative response with respect to glucose in the concentration range 0.25-5 mM with a Hill coefficient of 1.6. In this range of glucose concentrations, the degree of cooperativity was dependent on the presence of glycerol in the assay mixture, and it decreased progressively and disappeared completely as the glycerol concentration reached about 20% (v/v) glycerol. If attention was confined to concentrations above 5 mM, no cooperativity could be detected either in the absence or in the presence of glycerol. The limiting velocity of the glucokinase reaction (measured at saturating concentrations of glucose and MgATP2-), and the half-saturation concentration for glucose and MgATP2- were all decreased by about 50-60% as the glycerol concentration was raised from zero to 30% (v/v). The presence of glycerol had no effect on the qualitative inhibition patterns of MgADP2-, glucose 6-phosphate, or N-acetylglucosamine, and only slight effects on the quantitative half-saturation values and inhibition constants. All of these effects caused by glycerol were fully reversible by decreasing the concentration of glycerol by dilution. Simulation studies based on the "mnemonical" model of glucokinase action proposed earlier [A. C. Storer and A. Cornish-Bowden (1977) Biochem. J. 165, 61-69] show that the effects of glycerol on glucokinase-catalyzed glucose phosphorylation can simply be explained assuming the glycerol favors the existence of the conformation of the enzyme with a higher affinity for glucose and thus supports the model.
Adenosine Triphosphate↗
The interhexameric contacts in the four-hexameric hemocyanin from the tarantula Eurypelma californicum. A tentative mechanism for cooperative behavior.
Arthropod hemocyanins (Hcs) are regular assemblies of 1, 2, 4, 6 or 8 hexameric protein molecules. They transport oxygen and can bind it in a cooperative manner. The hexameric X-ray structures of Panulirus interruptus (spiny lobster) and of Limulus polyphemus (horseshoe crab) subunit II Hc were solved recently by the groups of Hol (Groningen, The Netherlands) and Magnus (Cleveland, U.S.A.). They related cooperativity to a rotational movement of a domain within a subunit and of the two trimers mutually inside the hexamer. In our study a model was derived for the structure and related to the function of the four-hexameric Hc from the tarantula Eurypelma californicum by combining data from electron microscopy and image processing, from the X-ray diffraction studies mentioned earlier and from amino acid sequence studies. Interhexameric contacts were determined at the level of secondary structure elements and in some cases of single amino acids. Loops, undefined in the X-ray structures of the hexamers, were often involved in these contacts. In one case the contact was formed between four parallel alpha-helices, two from each hexamer. Based on these findings a mechanism is proposed for the transmission of cooperativity between the hexamers, in which the concept of "helical friction" plays a key role.
Amino Acid Sequence↗
Cooperative behavior in the thiol oxidation of rabbit muscle glycogen phosphorylase in cysteamine/cystamine redox buffers.
Glycogen phosphorylase a and b are irreversibly inactivated by oxidation with the disulfide cystamine. The mechanism is complex and involves oxidation of at least two classes of sulfhydryl groups. The oxidation of one or more of the first class of 4 +/- 1 sulfhydryl groups is reversible, but the equilibrium constant for the oxidation is so unfavorable (1 X 10(-4)) that the micromolar concentrations of cysteamine released stoichiometrically with enzyme oxidation are sufficient to prevent complete oxidation even in the presence of 100 mM cystamine. The rapid phase of inactivation of phosphorylase b, which is first order in cystamine (k = 2.9 +/- 0.3 M-1 min-1), is followed by the oxidation of 5 +/- 1 groups in an irreversible process that is second order in cystamine concentration (k = 3.9 +/- M-2 min-1). Similar behavior is observed for phosphorylase a, although the behavior is complicated by association/dissociation equilibrium. The second-order dependence of the rate of irreversible inactivation on cystamine concentration is interpreted in terms of a "cooperative" model in which a rapidly reversible thermodynamically unfavorable equilibrium oxidation of one or more sulfhydryl groups must precede the irreversible oxidation of one or more additional sulfhydryl groups. The thiol/disulfide oxidation equilibrium constant for the initial reversible reaction is estimated to be at least 10(4) less favorable than that for the reversible oxidation of phosphofructokinase.
Adenosine Monophosphate↗
Cooperative behavior of molecular motors.
Both experimental evidence and theoretical models for collective effects in the working mechanism of molecular motors are reviewed at three different levels, namely: (i) interaction between the two heads of double-headed motors, particularly in processive motors like kinesin, myosin V and myosin VI, (ii) cooperative regulation of muscle thin filaments by accessory proteins and the Ca2+ level, and (iii) collective dynamic effects stemming from the mechanical coupling of molecular motors within macroscopic structures such as muscle thick filaments or axonemes. We aim to bridge the gap between structural information at the molecular level and physiological data with accompanying specific models on the one hand, and general stochastic physical models for the action of molecular motors on the other hand. An underlying assumption is that while, ultimately, the function of molecular motors will be explainable by a quantitative description of specific intramolecular dynamics and intermolecular interactions, for some coarse grained larger scale dynamic features it will be sufficient and illuminating to construct physical models that are simplified to the bare essentials.
Animals↗
Cooperative behavior of Escherichia coli cell-division protein FtsZ assembly involves the preferential cyclization of long single-stranded fibrils.
A mechanism of noncooperative (isodesmic) assembly coupled with preferential cyclization of long polymers is proposed to explain the previously posed question of how a single-stranded filament of the bacterial cell-division protein FtsZ can assemble in an apparently cooperative manner. This proposal is based on results of GTP-mediated assembly of FtsZ from Escherichia coli that was studied under physiologically relevant steady-state solution conditions by a combination of methods including measurement of sedimentation velocity, atomic force and electron microscopy, and precipitation assays. Sedimentation-velocity experiments carried out at multiple protein concentrations reveal an essentially bimodal distribution of slowly sedimenting species and a relatively narrow distribution of rapidly sedimenting species that appears only above an apparent "critical concentration" of protein. In a precipitation assay, the amount of protein that pellets, which correlates with the fraction of rapidly sedimenting species observed in sedimentation-velocity experiments, increases linearly with the total concentration of protein in excess of the critical concentration. Sedimentation coefficients of the rapidly sedimenting fraction are qualitatively consistent with the presence of single-stranded cyclic oligomers with a size range of approximately 50-150 protomers, similar to polymeric single-stranded rings observed in atomic force and electron micrographs. The proposed model is in accord with the results obtained from our experimental observations.
Centrifugation↗
Determination of ligand binding constants for the iron-molybdenum cofactor of nitrogenase: monomers, multimers, and cooperative behavior.
Equilibrium titrations in N-methylformamide (NMF) of G-25 gel filtered (ox)-state FeMo cofactor [FeMoco(ox)] from Azotobacter vinelandii nitrogenase were carried out using sodium ethanethiolate and followed using UV/Vis absorption spectroscopy. For Fe-Moco(ox), a non-linear least squares (NLLSQ) fit to the data indicated a strong equilibrium thiolate-binding step with Keq = 1.3+/-0.2x10(6) M(-1). With 245 molar excess imidazole, cooperative binding of three ethanethiolates was observed. The best NLLSQ fit gave Keq=2.0+/-0.1x10(5) M(-2) and a Hill coefficient n=2.0+/-0.3. A Scatchard plot of these data was concave upward, indicating positive cooperativity. The fit to previously published data involving benzenethiol titration of the one-electron reduced (semi-reduced) cofactor, FeMoco(sr), as followed by EPR required a model that included both a sub-stoichiometric ratio of thiol to FeMoco(sr) and about five cooperative ligand binding sites. These constraints were met by modeling FeMoco(sr) as an aggregate, with fewer thiol binding sites than FeMoco(sr) units. The best fit model was that of FeMoco(sr) as a dodecamer with five cooperative benzenethiol binding sites, yielding a thiol binding constant of 3.32+/-0.09x10(4) M(-4.8) and a Hill coefficient n=4.8+/-0.6. The results of all the other published ligand titrations of FeMoco(sr) were similarly analyzed successfully in terms of equilibrium models that include both cooperative ligand binding and dimer-level aggregation. A possible structural model for FeMoco aggregation in NMF solution is proposed.
Cyanides↗
Hysteresis and cooperative behavior of a latent plant polyphenoloxidase.
Appearance of a lag period dependent on pH in the expression of the catecholase activity of a polyphenoloxidase extracted in a latent state from Airen grape (Vitis vinifera L.) berries, is revealed, suggesting the hysteretic nature of the enzyme. The lag time was independent of enzyme concentration, indicating that slow pH-induced conformational changes in the protein must occur during assay. Results obtained by varying substrate concentration show that the system presents hyperbolic or cooperative kinetics depending on the pH of the assay.
Journal Article↗
The cooperative behavior of yeast D-glyceraldehyde-3-phosphate. Dehydrogenase as studied by the formation of the fluorescent NAD derivative.
The ultraviolet irradiation of the yeast D-glyceraldehyde-3-phosphate dehydrogenase carboxymethylated at the active site Cys residues, as with the rabbit muscle enzyme, led to the formation of a fluorescent NAD derivative with an emission maximum at 410 nm. Similar results were obtained with the enzyme selectively carboxymethylated at only 2 of its 4 active site Cys residues. The binding of NAD+ to both the carboxymethylated enzymes is non-cooperative or only weakly negatively cooperative when determined by NAD+ quenching of the intrinsic protein fluorescence. However, determinations of the amount of fluorescent NAD derivative formed under different NAD+ concentrations show that both the carboxymethylated enzymes appeared to bind NAD+ with positive cooperativity as in the case of the binding of NAD+ to the native apoenzyme. This seems to suggest that the spatial positioning of the nicotinamide moiety at the active site of the irradiated enzyme resembles more closely that of the nicotinamide ring in the native holoenzyme as compared to the carboxymethylated enzymes.
Allosteric Regulation↗
Independent and cooperative behavior of Thy1 and CD3:TcR T cell signalling pathways.
Normal resting spleen T lymphocytes from mice were stimulated in vitro by monoclonal antibodies (mAbs) against either Thy 1 or CD3:TcR surface protein molecules. Although both mAbs were mitogenic, anti-Thy 1 activation generated 5 times more IL2 secretion than anti-CD3 activation under similar conditions. Production of IL3-like activity was comparable for both Thy1 and CD3-mediated activation. In addition, non-mitogenic doses of anti-CD3 and anti-Thy1 (0.16 micrograms/ml and 0.0125% ascites, respectively) mAbs induced T cell activation when provided together. These results indicate that Thy1 signalling cooperates with the CD3:TcR pathway to activate T cells. However, the Thy1 pathway is also regulated independently since IL2 production is larger when stimulated by anti-Thy1 than anti-CD3 mAbs.
Animals↗
Cooperative behavior of smooth muscle myosin.
Phosphorylation of smooth muscle myosin is thought to be a prerequisite for the activation of Mg2+-ATPase activity by actin. However, this idea is not accepted universally and other possible roles have been suggested either as alternative regulatory mechanisms or as mechanisms acting in addition to myosin phosphorylation. To clarify the situation we studied the effects of myosin phosphorylation on actin-activated ATPase activity by using a defined system where each of the component proteins was purified. Data were collected between 4 and 10 min after the addition of ATP. It was found that phosphorylation alone was sufficient to activate the Mg2+-ATPase activity although the relationship between phosphorylation and ATPase activity was not linear. Phosphorylation of approximately half of the available sites caused relatively little activation (to about 10% of the final ATPase activity), whereas the phosphorylation of the remaining sites elicited a marked activation of ATPase activity. These results raise the possibility that cooperative interactions occur between the two myosin heads. Evidence is also presented to suggest that the pathway of phosphorylation might be sequential, rather than random, again implying cooperativity between the myosin heads.
Actins↗