Electron coupling through a beta strand has been investigated by measurement of the intramolecular electron-transfer (ET) rates in ruthenium-modified derivatives of the beta barrel blue copper protein Pseudomonas aeruginosa azurin. Surface histidines, introduced on the methionine-121 beta strand by mutagenesis, were modified with a Ru(2,2'-bipyridine)2(imidazole)2+ complex. The Cu+ to Ru3+ rate constants yielded a distance-decay constant of 1.1 per angstrom, a value close to the distance-decay constant of 1.0 per angstrom predicted for electron tunneling through an idealized beta strand. Activationless ET rate constants in combination with a tunneling-pathway analysis of the structures of azurin and cytochrome c confirm that there is a generally efficient network for coupling the internal (native) redox center to the surface of both proteins.

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Social networking sites (SNSs) have become increasingly common in recent years, and their use has become integrated into the daily lives of millions of people across the world. Attracting new users and retaining existing ones are critical to the success of SNS providers. This study applies the push‐pull‐mooring model of the migration theory to improve our understanding of factors that influence the switching behavior of SNS users. Following the migration theory, this study empirically examines the three categories of antecedents for SNS switching intention: push (i.e., dissatisfaction and regret), pull (i.e., alternative attractiveness), and mooring (i.e., switching costs) factors. The results show that the three categories of factors had varying degrees of effects on switching intention. Additionally, the strong moderation effects of both pull and mooring factors help answer the question why switching does not necessarily occur when push factors are in effect. Managerial implications are provided.

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Purpose -The focus in this study is a model that predicts continuance intention of online multiplayer games. In this integrated model, the social cognitive theory (SCT) lays out the foundation of two types of pre-use (pre-play) expectations, the flow theory captures the affective feeling with the game as a moderator for the effect from the two pre-use expectations, and subjective norm together with its associated antecedents cover a wide spectrum of social influences. Design/methodology/approach -A questionnaire was designed and pre-tested before distributing to target respondents. The reliability and validity of the instrument both met the commonly accepted guidelines. The integrated model was assessed first by examining its measurement model and then the structural model. Findings -The integration of cognitive, affective and social influence in this model explains a larger amount of variance compared to the competing models and existing studies. Originality/value -Unlike a popular trend that studies predictors of online games from either cognitive or affect angle, the work looks at both together to study how their joint effect is related to continuance intention. This marks an important improvement as cognitive expectations derived from SCT captures the pre-use experience that may be influenced or swayed by sources including those that are inflated or incorrect. By studying flow as a moderator in conjunction with other sources of influence, the authors are able to further the understanding of how the pre-use expectations may be shaped by one's own experience.

The rates of Ru(His33)cytochrome c electron-transfer (ET) reactions have been measured over a driving-force range of 0.59 to 1.89 eV. The driving-force dependence of Fe2+ → Ru3+ ET in RuL2(im)(His33)cyt c [L = 2,2‘-bipyridine (bpy), 4,4‘,5,5‘-tetramethyl-2,2‘-bipyridine (4,4‘,5,5‘-(CH3)4-bpy), 4,4‘-dimethyl-2,2‘-bipyridine (4,4‘-(CH3)2-bpy), 4,4‘-bis(N-ethylcarbamoyl)-2,2‘-bipyridine (4,4‘-(CONH(C2H5))2-bpy), 1,10-phenanthroline (phen); im = imidazole] is well described by semiclassical ET theory with k max = 2.7 × 106 s-1 (HAB = 0.095 cm-1) and λ = 0.74 eV. As predicted by theory, the rate of an exergonic (−ΔG° = 1.3 eV) heme reduction reaction, *Ru2+(bpy)2(im)(His) → Fe3+, falls in the inverted region (k = 2.0 × 105 s-1). In contrast, the rates of three highly exergonic heme reductions, *Ru2+(phen)2(CN)(His) → Fe3+ (2.0 × 105 s-1; 1.40 eV), Ru+(4,4‘-(CONH(C2H5))2-bpy)2(im)(His) → Fe3+ (2.3 × 105 s-1; 1.44 eV), and Ru+(phen)2(CN)(His) → Fe3+ (4.5 × 105 s-1; 1.89 eV), are much higher than expected for reactions directly to ground-state products. Agreement with theory is greatly improved by assuming that an electronically excited ferroheme (Fe2+ → *Fe2+; ∼ 1.05 eV) is the initial product in each of these reactions.

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