Information exchange in policy networks is usually attributed to preference similarity, influence reputation, social trust and institutional actor roles. We suggest that political opportunity structures and transaction costs play another crucial role and estimate a rich statistical network model on tie formation in the German toxic chemicals policy domain. The results indicate that the effect of preference similarity is absorbed by institutional, relational and social opportunity structures. Political actors choose contacts that minimize transaction costs while maximizing outreach and information. We also find that different types of information exchange operate in complementary, but not necessarily congruent, ways. Keywords: Policy Networks, ERGM, Information Exchange, Transaction Cost Theory, Interest GroupsThe policy network approach assumes that policy-making is affected by a variety of organized governmental and non-governmental actors (Adam and Kriesi 2007), who maintain relations like information or resource exchange, influence attribution, or common group membership. Policy networks are usually supported by "polycentric" institutional arrangements (Ostrom 2010) facilitating collaboration and information exchange in a long-term pespective as a kind of "2 nd order economization" (Williamson 2000). The question how policy networks operate has provoked a substantial number of policy network studies over the course of the last 30 years. Some of the more recent analyses have tried to assess the reasons why political actors establish contacts to some actors but not to others.

Pathogen reduction technology-treated PLTs remained comparable to untreated units throughout 7 days of storage. Mitochondria-based oxidative respiration appeared up-regulated after the riboflavin-based PRT. Compared to the psoralen-based PRT, this resulted in significantly better ATP maintenance and in vitro function during the last storage period (d7, d8).

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PRT treatment using M increased both anoxidative glycolytic flux and oxidative phosphorylation. The I-based technique was associated with an impaired mitochondria-based respiration. During terminal storage, this resulted in significantly lower maintenance of ATP and cell viability. The impact of these findings for storage prolongation or clinical use must await further evaluation.