A computer‐mediated communication system (CMCS) was used to explore the effects of de‐individuation on group polarization. Reicher (1984) argued that de‐individuating members of a group should increase the salience of group identity and hence normative behaviour, while de‐individuating subjects treated as individuals should have the reverse effect. We extended this idea to the group polarization paradigm and in addition independently manipulated group salience and de‐individuation, which were confounded factors in Reicher's study. It was reasoned that the visual anonymity created by isolating discussants in separate rooms would be de‐individuating compared to seating them together in the same room. At the same time either the subject's group or individual identity was made salient. A computer‐mediated communication system provided text‐based communication for discussants in all four conditions. Assuming that group polarization reflects conformity to a group norm (Turner, Hogg, Oakes, Reicher & Wetherell, 1987), we predicted an interaction between the de‐individuation and group salience factors, such that greatest polarization in the direction of a pre‐established group norm would be obtained in the de‐individuated—group condition and least in the de‐individuated—individual condition. This prediction was confirmed. Explanations of the findings in terms of Reicher's earlier study and in terms of self‐attention processes are considered within the general framework of social identity theory. Finally, the relevance of this research to the realm of human communication via computer networks is evaluated.

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The Social Identity Model of Deindividuation Effects (SIDE) proposes that depersonalization of self and others is responsible for the effects of visual anonymity on group behavior. The authors investigated these mediating processes by assessing the effects of group-based self-categorization and stereotyping of others on group attraction within visually anonymous or video-identifiable groups communicating via computer. Structural equation modeling showed that visual anonymity increased group-based self-categorization, which directly increased attraction to the group and indirectly increased group attraction by enhancing group-based stereotyping of others.Visual anonymity had no effect on self-categorization in terms of a wider social category (nationality). Predictions derived from alternative perspectives that visual anonymity decreases group attraction by increasing impersonal task focus or by attenuating evaluation concerns were not supported.

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Platelets sequester angiogenesis regulatory proteins which suggests an avenue for developing biomarkers to monitor disease. We describe a comparison of angiogenesis regulatory proteins found in platelets of colorectal cancer patients and normal controls. Platelet and plasma content of vascular endothelial growth factor (VEGF), basic fibroblast growth factor (bFGF), platelet derived growth factor (PDGF), platelet factor 4 (PF4), thrombospondin-1 (TSP-1) and endostatin in 35 patients with colon cancer were compared with 84 age-matched healthy controls using ELISAs. We standardized the platelet preparation procedure, introduced process controls and normalized the respective protein levels to platelet numbers using an actin ELISA. Statistically significant differences were found in the median levels of VEGF, PF4 and PDGF in platelets of patients with cancer compared to healthy individuals. Platelet concentrations in cancer patients versus controls were: VEGF 1.3 versus 0.6 pg/10(6), PF4 18.5 versus 9.4 ng/10(6), and PDGF 34.1 versus 21.0 pg/10(6). Multivariable logistic regression analysis indicated that PDGF, PF4 and VEGF were independent predictors of colorectal carcinoma and as a set provided statistically significant discrimination (area under the curve = 0.893, P < .0001). No significant differences were detected for bFGF, endostatin, or TSP-1. Reference Change Value analysis determined that the differences seen were not clinically significant. Plasma levels yielded no correlations.

The formation of group norms in computer-mediated communication (CMC) was examined among students who used e-mail as part of a course. A network analysis of group structures revealed that (a) content and form of communication is normative, group norms defining communication patterns within groups, (b) conformity to group norms increases over time, (c) communication outside the group is governed by different social norms. Results show that norms prescribing a particular use of technology are socially constructed over time at the level of locally defined groups and also show that the influence of these norms is limited to the boundaries of the group. It is concluded that the process of social construction is restrained by social identities that become salient over the course of interaction via CMC. These findings complement experimental evidence that stresses the importance of normative influence in CMC.T he once popular idea that communication technology has certain fixed effects on human interaction (technological determinism) increasingly is being challenged by research showing the diverse effects of these media. Many theories now emphasize the reciprocal influence of technology and the social context in shaping the ways in which

Hydrogen exchange (HX) rates and midpoint potentials (E m ) of variants of cytochromes c from Pseudomonas aeruginosa (Pa cyt c 551 ) and Hydrogenobacter thermophilus (Ht cyt c 552 ) have been characterized toward developing an understanding of the impact of properties of the Cys-X-X-CysHis pentapeptide c-heme attachment motif (CXXCH) on heme redox potential. Despite structural conservation of the CXXCH motif, Ht cyt c 552 exhibits low protection from HX for amide protons within this motif relative to Pa cyt c 551 . Site-directed mutants have been prepared to determine the structural basis for and functional implications of these variations in HX behavior. The double mutant Ht-M13V/K22M displays suppressed HX within the CXXCH motif as well as decreased E m (by 81 mV), whereas the corresponding double mutant of Pa cyt c 551 (V13M/M22K) exhibits enhanced HX within the CXXCH pentapeptide and a modest increase in E m (by 30 mV). The changes in E m correlate with changes in axial His chemical shifts in the ferric proteins reflecting extent of histidinate character. Thus the mobility of the CXXCH pentapeptide is found to impact the His-Fe(III) interaction and therefore heme redox potential.Electron transfer reactions involving iron-protoporphyrin IX (heme) are central to fundamental biological processes such as respiration, redox catalysis, sensing, and signaling (1-5). A key parameter determining energetics and kinetics of electron transfer is the redox potential (1), thus, much emphasis has been placed on understanding the role of protein structure in tuning heme redox potential. Two fundamental features known to have a substantial influence on heme redox potentials are the nature of the ligands coordinated to the metal and the burial of the heme in the hydrophobic protein core. Nature alters the electron donating properties of the coordinating ligands through choice of ligands (6), modulating metal-ligand bond strength (6-12), varying coordination geometry (5), and hydrogen bonding to ligands (13)(14)(15). The encapsulation of the heme within a protein's interior also is significant for determining potential, as the hydrophobic environment favors the ferrous state over the ferric (7,8,10,16,17). Although there have been many studies of the effects of static polypeptide structure on heme-ligand interactions and on heme burial, the role of protein mobility has received less attention. Protein motions may indeed be important as they could influence metal-ligand interactions (15,18,19) and solvent exposure. † This work supported by National Institutes of Health Grant GM63170 (K.L.B.), a Fellowship from the Alfred P. Sloan Foundation (K.L.B.), and National Science Foundation Grant MCB-0546323 (S.J.E.).*To whom correspondence should be addressed: Department of Chemistry, University of Rochester, Rochester, NY 14627-0216. Telephone: (585) Here, we investigate the effects of structural fluctuations of the c-heme motif of cytochrome c (cyt c 1 ) on redox potential. The c-type heme is characterized by its covalen...

Two studies examined intergroup discussions via computer-mediated communication systems. It was hypothesized that depersonalization, in comparison with individuated interaction, would increase the tendency for intergroup differentiation in attitudes and stereotypes. In Study 1, 24 groups communicated internationally over the Internet in a longitudinal design. Interacting groups, based in 2 different countries, were individuated versus partially unidentifiable, and thus depersonalized. Results indicate that depersonalized groups diverge, or bipolarize, when compared with individuated groups.A follow-up study demonstrated that under depersonalized conditions, individual differences are less salient, whereas group memberships are more salient. In addition, stereotypes were more salient in depersonalized conditions. Results support predictions derived from the social identity model of deindividuation effects.