Communication In Complex Research Articles

Solvent and electrolyte effects in enhancing the identification of intramolecular electronic communication in a multi redox-active diruthenium tetraferrocenoate complex, a triple-sandwiched dicadmium phthalocyanine and a ruthenocene-containing β-diketone

Enhanced electrochemical resolution of anodic processes is possible in the presence of [N( n Bu) 4][B(C 6F 5) 4], 1, as supporting electrolyte over that obtained in the presence of [N( n Bu) 4][PF 6]. By changing the anion of the supporting electrolyte to a salt having [B(C 6F 5) 4] −, anions, electrochemical processes of especially cationic analytes can benefit. Thus, the redox chemistry of 0.5 mmol dm −3 solutions of [Ru 2(μ-FcCOO) 4·(CH 3CH 2OH) 2][PF 6], 2, Fc = ferrocenyl, in CH 2Cl 2/[N( n Bu) 4][B(C 6F 5) 4] were found to involve four well-resolved ferrocenyl-based electrochemical reversible redox processes as well as reduction of Ru III–Ru II. At 1.0 mmol dm −3 concentrations of 2, or in the presence of [N( n Bu) 4][PF 6], the four ferrocenyl processes coalesced into only two waves as a result of (Fc +)⋯( PF 6 - ) ion paring. Seventeen of the possible 18 one-electron transfer processes of the biscadmium trisphthalocyaninato complex [Cd 2{Pc(C 6H 13) 8} 3], 3, could be observed in THF/[N( n Bu) 4][B(C 6F 5) 4], but the electrochemical window of CH 2Cl 2/[N( n Bu) 4][B(C 6F 5) 4] only allowed detection of 15 of these processes. Although reduction processes were unaffected, THF solvation leading to species such as ( 3 n +)(THF) x with 1 ⩽ n ⩽ 4 and x ⩾ 1 as well as ion pair formation of the type ( 3 n +)⋯( PF 6 - ) prevented good resolution of oxidation processes. The CH 2Cl 2/[N( n Bu) 4][B(C 6F 5) 4] system also allowed detection of reversible one-electron transfer ferrocenyl (Fc/Fc +) and ruthenocenyl-based (Rc/Rc +) processes for both enol and keto isomers of the β-diketone FcCOCH 2CORc, 4, Rc = ruthenocenyl. In CH 3CN/[N( n Bu) 4][PF 6], the ruthenocenyl moiety was oxidised to a Ru IV species.

Evolution from DNA to RNA recognition by the bI3 LAGLIDADG maturase

LAGLIDADG endonucleases bind across adjacent major grooves via a saddle-shaped surface and catalyze DNA cleavage. Some LAGLIDADG proteins, called maturases, facilitate splicing by group I introns, raising the issue of how a DNA-binding protein and an RNA have evolved to function together. In this report, crystallographic analysis shows that the global architecture of the bI3 maturase is unchanged from its DNA-binding homologs; in contrast, the endonuclease active site, dispensable for splicing facilitation, is efficiently compromised by a lysine residue replacing essential catalytic groups. Biochemical experiments show that the maturase binds a peripheral RNA domain 50 A from the splicing active site, exemplifying long-distance structural communication in a ribonucleoprotein complex. The bI3 maturase nucleic acid recognition saddle interacts at the RNA minor groove; thus, evolution from DNA to RNA function has been mediated by a switch from major to minor groove interaction.

Switching of the Electronic Communication between Two {Ru(trpy)(bpy)} (trpy = 2,2‘:6‘,2‘ ‘-Terpyridine and bpy = 2,2‘-Bipyridine) Centers by Protonation on the Bridging Dimercaptothiadiazolato Ligand

A stable Ru(II)/Ru(III) mixed-valence state was observed in acetonitrile for the ruthenium binuclear complex bridged by dimercaptothiadiazolate (DeltaE(1/2) = 220 mV for Ru(2)(II,II)/Ru(2)(II,III) and Ru(2)(II,III)/Ru(2)(III,III) processes; K(com) = 5.3 x 10(3)). Upon protonation of the bridging ligand by the addition of equimolar p-toluenesulfonic acid, however, the mixed-valence state diminished (DeltaE(1/2) = 0 mV). The bridging ligand operates as a proton-induced switch of the electronic communication in the dimeric complex.

Teams of pushdown automata

We introduce team pushdown automata (PDAs) as a theoretical framework capable of modelling various communication and cooperation strategies in complex, distributed systems. Team PDAs are obtained by augmenting distributed PDAs with the notion of team cooperation or, alternatively, by augmenting team automata with pushdown memory. In a team PDA, several PDAs work as a team on the input word placed on a common one-way input tape. At any moment in time one team of PDAs, each with the same symbol on top of its stack, is active: each PDA in the active team replaces the topmost symbol of its stack and changes state, while the current input symbol is read from the input tape by a common reading head. The teams are formed according to the team cooperation strategy of the team PDA and may vary from one moment to the other. Based on the notion of competence, we introduce a variety of team cooperation strategies. If all stacks are empty when the input word has been completely read, then this word is part of the language accepted by the team PDA. Here we focus on the accepting capacity of team PDA. †E-mail: csuhaj@sztaki.hu ‡E-mail: mitrana@funinf.cs.unibuc.ro

Allosteric communication in the tryptophan synthase bienzyme complex: roles of the beta-subunit aspartate 305-arginine 141 salt bridge.

The allosteric interactions that regulate substrate channeling and catalysis in the tryptophan synthase bienzyme complex from Salmonella typhimurium are triggered by covalent reactions at the beta-site and binding of substrate/product to the alpha-site. The transmission of these allosteric signals between the alpha- and beta-catalytic sites is modulated by an ensemble of weak bonding interactions consisting of salt bridges, hydrogen bonds, and van der Waals contacts that switch the subunits between open and closed conformations. Previous work has identified a scaffolding of salt-bridges extending between the alpha- and beta-sites consisting of alphaAsp 56, betaLys 167, and betaAsp 305. This work investigates the involvement of yet another salt bridging interaction involving the betaAsp 305-betaArg 141 pair via comparison of the spectroscopic, catalytic, and allosteric properties of the betaD305A and betaR141A mutants with the behavior of the wild-type enzyme. These mutations were found to give bienzyme complexes with impaired allosteric communication. The betaD305A mutant also exhibits altered beta-site substrate reaction specificity, while the catalytic activity of the betaR141A mutant exhibits impaired beta-site catalytic activity. The >25-fold activation of the alpha-site by alpha-aminoacrylate Schiff base formation at the beta-site found in the Na(+) form of the wild-type enzyme is abolished in the Na(+) forms of both mutants. Replacing Na(+) by NH(4)(+) or Cs(+) restores the betaD305A to a wild-type-like behavior, whereas only partial restoration is achieved with the betaR141A mutant. These studies establish that the betaD305-betaR141 salt bridge plays a crucial role both in the formation of the closed conformation of the beta-site and in the transmission of allosteric signals between the alpha- and beta-sites that switch the alpha-site on and off.

Strategic Partnerships in the Domestic Textile Complex: Exploring Suppliers’ Perspectives

A strategic partnership is an alliance between two or more firms in which resources, capabilities, and core competencies are combined to pursue mutual benefits (Hitt, Ireland, & Hoskisson, 1997). The purpose of this pilot study was to examine strategic partnerships within the domestic textile complex. Qualitative interviews were conducted spring 1999 with seven textile complex executives. A two-page interview instrument was developed for data collection, based on a theoretical framework that incorporated both Thibaut and Kelley’s (1959) social exchange theory and the Lorange and Roos (1992) Partners’ Supply Chain Model. Results showed that a) partnerships did exist in the domestic textile complex; b) costs were both financial (for partnership establishment) and relational (conflict of interest between partners); and c) benefits included sharing of private company information, sharing of financial risk, receiving exclusive access to select goods and services, and reduced time to market. Strategic partnerships will play a key role in the future by strengthening communication and business relationships in the domestic textile complex.

Evidence for mutations that break communication between the Endo and Topo domains in NaeI endonuclease/topoisomerase.

NaeI is a type IIe endonuclease that interacts with two DNA recognition sequences to cleave DNA. One DNA sequence serves as a substrate and the other serves to activate cleavage. NaeI is divided into two domains whose structures parallel the two functionalities recognized in NaeI, endonuclease and topoisomerase. In this study, we report evidence for mutations that break interdomain functional communication in a NaeI-DNA complex. Deletion of the initial 124 amino acids of the N-terminal domain of NaeI converted NaeI to a monomer, consistent with self-association being mediated by the Endo domain. Deletions within a small region of the C-terminal DNA binding domain of NaeI (amino acids 182-192) altered the recognition by NaeI of sequences flanking the NaeI recognition sequence. Substituting Ala for Arg182 within this region had no apparent effect on DNA binding but greatly reduced the extent of DNA cleavage even though it is not part of the catalytic Endo domain. Substituting Ala for Ile185 reduced the extent of DNA binding about 1000-fold. Substituting Ala for Lys189 altered flanking sequence recognition. Residues 182-192 are away from the Endo domain responsible for cleavage and also face away from the modeled DNA binding faces of the apoprotein crystal structure. We propose that residues 182-192 are part of a web that mediates the flow of information between the NaeI Endo and Topo domains.

Deformation processes in the Britannia Field, UKCS

The intensity and distribution of deformation within cores recovered from 24 Britannia Field wells has been quantified and used to assess the sub-seismic deformation present. Structural logging has been amalgamated with microstructural and petrophysical analysis of fault rocks and the results used to construct models of the fluid flow behaviour of fault zones and to evaluate the correlations between core-scale structures and the larger-scale seismically mapped fault arrays. Deformation within Britannia is controlled primarily by (1) early sediment disruption, dewatering, detachment and folding in semi-lithified sediments and (2) more long-lived clustered arrays of small faults developed within fault damage zones. Fault population analysis illustrates that seismic-based mapping alone does not provide a good platform for accurately predicting the number of sub-seismic faults present. Analysis of the effect of deformation features on fluid communication highlights the importance of small-scale faults in enhancing communication in complex and initially separate sand bodies.

Evidence for breaking domain-domain functional communication in a synthetase-tRNA complex.

We report here evidence for mutations that break domain-domain functional communication in a synthetase-tRNA complex. Each synthetase is roughly divided into two major domains that are paralleled by the two arms of the L-shaped tRNA structure. The active-site-containing domain interacts with the acceptor arm of the tRNA. The second domain frequently interacts with the anticodon-containing arm. By an induced-fit mechanism, contacts with the anticodon can activate formation of a robust transition state at a site over 70 A away. This induced-fit-based activation is thought to occur through domain-domain signaling and is seen by the enhancement of aminoacylation of the anticodon-containing full tRNA versus a substrate based on the acceptor arm alone. Here we describe a rationally designed mutant methionyl-tRNA synthetase containing two point substitutions at sites that potentially link an anticodon-binding motif to the catalytic domain. The double mutation had no effect on interactions with either the isolated acceptor arm or the anticodon stem-loop. In contrast to interactions with the separate pieces, the mutant enzyme was severely impaired for binding the native tRNA and lost much of its ability to enhance the rate of charging of the full tRNA over that of a substrate based on the acceptor arm alone. We propose that these residues are part of a network for facilitating domain-domain communication for formation of an active synthetase-tRNA complex by induced fit.

Evolution of vocal communication in the gray treefrog complex

The evolution of communication requires changes in both signals and the criteria used by receivers to select signals. The question arises: Do changes occur first in signals, first in receivers, or are tight co-evolutionary changes required in both signals and receivers? In the gray treefrog complex, spectral properties of calls are conserved: in both the diploid ancestral species (Hyla chrysoscelis) and in derived, tetraploid lineages (nominally, H. versicolor) there are two spectral peaks: a dominant band centered at about 2.4 kHz, and a secondary band (−8 to −10 dB) at about 1.2 kHz. Whereas females of the ancestral species have a weak preference for calls consisting only of the secondary band to calls having only the dominant band, females of the derived species strongly prefer calls with just the dominant band. Thus, an evolutionary change in preference has preceded any change in the spectral properties of the call. Temporal differences between the species include pulse rate, pulse duration, and pulse shape. Whereas females of the ancestral species use pulse rate alone for call discrimination, females of the derived species base preferences on all three properties, thus suggesting a co-evolutionary change. [Work supported by NSF and NIMH.]

Swiveling-domain mechanism for enzymatic phosphotransfer between remote reaction sites.

The crystal structure of pyruvate phosphate dikinase, a histidyl multiphosphotransfer enzyme that synthesizes adenosine triphosphate, reveals a three-domain molecule in which the phosphohistidine domain is flanked by the nucleotide and the phosphoenolpyruvate/pyruvate domains, with the two substrate binding sites approximately 45 angstroms apart. The modes of substrate binding have been deduced by analogy to D-Ala-D-Ala ligase and to pyruvate kinase. Coupling between the two remote active sites is facilitated by two conformational states of the phosphohistidine domain. While the crystal structure represents the state of interaction with the nucleotide, the second state is achieved by swiveling around two flexible peptide linkers. This dramatic conformational transition brings the phosphocarrier residue in close proximity to phosphoenolpyruvate/pyruvate. The swiveling-domain paradigm provides an effective mechanism for communication in complex multidomain/multiactive site proteins.

Analysing communication in complex distributed decision-making.

This paper analyses emergency tasks within the theoretical framework of dynamic environment management with distributed decision-making (DDM). Models of task and work organization are used to analyse verbal exchanges in order to infer collective strategies. A cross-analysis method serves to analyse communication from the standpoint of both semantics and structure of the exchanges. The findings of two empirical comparative studies show that invariants vs differences in the organization and the semantics of exchanges are associated with invariants vs differences in parameters of the situations themselves (initial state and final result of actions). Efficient strategies were linked with well-structured flow of communication and roles distribution.

Collaborative Decision Making in Dynamic Systems

Operators of power plants, management decision makers and military commanders are often faced with collaborating and coordinating decision making efforts with other people while simultaneously interacting with computer-based control or information systems. We view such activities as collaborative decision making and consider the communication and coordination involved in those tasks to be the essence of team performance. The purpose of this paper is to outline the important factors in collaborative decision making and identify the important issues relevant to communication and coordination in complex, dynamic systems. A model of collaborative decision making in dynamic systems will be described that relies on three important elements: decision making; communication; and the user interface.

Maturation of the rat cumulus‐oocyte complex: Structure and function

The cumulus cells that surround the mammalian oocyte become dispersed following the preovulatory surge of the pituitary gonadotropin, luteinizing hormone (LH). We have examined cumulus-oocyte complexes of PMSG-primed immature rats before and at 1, 2, 3, 4, 6, and 8 hr after injection of human chorionic gonadotropin (hCG), which acts on the rat ovary like the pituitary gonadotropin. Associations between projections of the cumulus cells and the oocyte were analyzed in thin sections. We observed that some cumulus projections were greatly enlarged where they associate with the oocyte. These enlarged regions were filled with numerous small vesicles. Gap junctions between cumulus cell projections and the oocytes were small. We quantitated the number and size of gap junctions between cumulus cells. The number of small gap junctions (less than 1 microM) between cumulus cells did not change significantly over the 8-hr period after hCG administration. Larger gap junctions, however, showed a general downward trend beginning after the third hour post hCG. Light microscopic observations of plastic sections revealed that dispersion of the cumulus oophorus is not observed until after 4 hr post-hCG, but between 4 and 8 hr after gonadotropin administration the cumulus becomes markedly dispersed. In the majority of the oocytes in these complexes the germinal vesicle (GV) displayed some irregularity in shape at 2 hr post-hCG, although absence of the GV was not observed until later. Our observations suggest a new means of communication in the cumulus-oocyte complex by the vesicle-filled enlargements of the cumulus cell projections at the oocyte surface. They further indicate that the decrease in metabolic coupling observed in rat cumulus-oocyte complexes soon after exposure to LH is not associated with a change in number and size of the gap junctions between the cumulus cells. We suggest that it is either the disruption of the gap junctions at the region of contact of the cumulus cell projections with the oocyte surface or the operation of a gating mechanism that blocks the junctional channels without affecting their morphological appearance that is responsible for uncoupling of the oocyte from the cumulus cells.

Regulation of oocyte maturation. The role of cAMP.

We suggest that cAMP is a key molecule in regulation of oocyte maturation. In the small follicle, tonic levels of cAMP are continuously transferred to the oocytes to maintain meiotic arrest. In the preovulatory follicle, in response to LH, cAMP levels are elevated. These increased concentrations of the nucleotide affect the cumulus cells and interrupt communication in the cumulus-oocyte complex. Under these conditions the flow of cAMP to the oocyte declines, inhibition is relieved, and meiosis is resumed.

Regulation of oocyte maturation: communication in the rat cumulus-oocyte complex

This study was undertaken to analyse the time relationships between breakdown of communication in the cumulus-oocyte complex and reinitiation of meiosis in the oocyte. In addition the possibility was examined that under conditions of established communication, cAMP is transferred from the cumulus cells to the oocyte. Coupling in the cumulus-oocyte complex and maturation of the oocyte were examined, both in vitro in follicles exposed to LH and in vivo following injection of the hormone to immature, pregnant mare's serum gonadotrophin-primed rats. Transfer analysis was performed by determination of cAMP content in cumulus-enclosed as compared to cumulus-free oocytes incubated with forskolin. It was discovered that after 1 h of culture in the presence of LH, coupling in the cumulus-oocyte complexes had decreased to 45% of its initial level, while only 10% of the oocytes had resumed meiosis by this time. The decrease in coupling in cumulus-oocyte complexes in vivo was 20% by 2 h after administration of the hormone, with all the oocytes being immature at this time. Cyclic AMP determinations revealed that cumulus-enclosed oocytes contained concentrations of cAMP three-fold higher than cumulus-free oocytes incubated under similar conditions. This study demonstrates that, in the rat, (i) a decrease in coupling precedes reinitiation of meiosis and (ii) in the presence of established communication, cAMP is transferred from the cumulus cells to the oocyte. These findings suggest that a decrease in communication can serve as the signal for oocyte maturation, possibly by preventing transfer of cAMP from the cumulus cells to the oocyte.

Barriers to Communication in Complex 1 Pharmaceutical Organizations

AbstractThis essay examines the most common and most serious barriers to effective communication in complex organizations, using the questionnaire responses of fifty-one ACP members as a basis for adapting the analysis to pharmaceutical organizations. It suggests that the most frequent breakdowns experienced by ACP members involve formal communication and defensiveness, particularly in supervisoi-subordinate interactions and proposes steps that individual employees can take to minimize the communication breakdowns they face.

Modulation of cell-to-cell communication in the cumulus-oocyte complex and the regulation of oocyte maturation by LH

Prior to ovulation, cell-to-cell communication between the oocyte and the cells of the cumulus oophorus is terminated ( N. B. Gilula, M. L. Epstein, and W. H. Beers, 1978, J. Cell Biol. 78, 58–75; R. M. Moor, M. W. Smith, and R. M. C. Dawson, 1980, Exp. Cell Res. 126, 15–29). In this paper we report that LH, Bt 2-cAMP, and the cyclic nucleotide phosphodiesterase inhibitor, 3-isobutyl-1-methylxanthine, are all capable of interrupting communication in vitro in rat follicle-enclosed cumulus-oocyte complexes. Moreover, the breakdown of communication appears to be closely correlated with the ability of hyaluronidase to disperse the cumulus cell mass. This observation allows simple screening of the effects of various agents on cumulus-oocyte communication. The in vitro system employed in this study has also been used to investigate the relationship between communication and oocyte maturation. The findings presented indicate that the interruption of communication between the cumulus and the oocyte leads to relief of meiotic arrest, and are consistent with the possibility that cAMP, transmitted from the cumulus to the oocyte, may be the inhibitor of oocyte maturation in vivo.