The Eyes Have It: Sex and Sexual Orientation Differences in Pupil Dilation Patterns

Recent research suggests profound sex and sexual orientation differences in sexual response. These results, however, are based on measures of genital arousal, which have potential limitations such as volunteer bias and differential measures for the sexes. The present study introduces a measure less affected by these limitations. We assessed the pupil dilation of 325 men and women of various sexual orientations to male and female erotic stimuli. Results supported hypotheses. In general, self-reported sexual orientation corresponded with pupil dilation to men and women. Among men, substantial dilation to both sexes was most common in bisexual-identified men. In contrast, among women, substantial dilation to both sexes was most common in heterosexual-identified women. Possible reasons for these differences are discussed. Because the measure of pupil dilation is less invasive than previous measures of sexual response, it allows for studying diverse age and cultural populations, usually not included in sexuality research

Crystal Structure of PrgI-SipD: Insight into a Secretion Competent State of the Type Three Secretion System Needle Tip and its Interaction with Host Ligands

Many infectious Gram-negative bacteria, including Salmonella typhimurium, require a Type Three Secretion System (T3SS) to translocate virulence factors into host cells. The T3SS consists of a membrane protein complex and an extracellular needle together that form a continuous channel. Regulated secretion of virulence factors requires the presence of SipD at the T3SS needle tip in S. typhimurium. Here we report three-dimensional structures of individual SipD, SipD in fusion with the needle subunit PrgI, and of SipD:PrgI in complex with the bile salt, deoxycholate. Assembly of the complex involves major conformational changes in both SipD and PrgI. This rearrangement is mediated via a π bulge in the central SipD helix and is stabilized by conserved amino acids that may allow for specificity in the assembly and composition of the tip proteins. Five copies each of the needle subunit PrgI and SipD form the T3SS needle tip complex. Using surface plasmon resonance spectroscopy and crystal structure analysis we found that the T3SS needle tip complex binds deoxycholate with micromolar affinity via a cleft formed at the SipD:PrgI interface. In the structure-based three-dimensional model of the T3SS needle tip, the bound deoxycholate faces the host membrane. Recently, binding of SipD with bile salts present in the gut was shown to impede bacterial infection. Binding of bile salts to the SipD:PrgI interface in this particular arrangement may thus inhibit the T3SS function. The structures presented in this study provide insight into the open state of the T3SS needle tip. Our findings present the atomic details of the T3SS arrangement occurring at the pathogen-host interface

A Political Economy of Positions in Climate Change Negotiations: Economic, Structural, Domestic, and Strategic Explanations

After the disappointing outcome of the Copenhagen climate summit, it still remains to be explained why the participating states chose irreconcilable negotiation positions that reflected very diverse domestic interests in spite of a publicly displayed wish for cooperation. While environmental studies have intensely investigated national climate policies and their determinants over the last few decades, little attention has been paid to the bargaining positions the same governments assume in climate negotiations. We argue that their bargaining positions reflect structural, economic, and domestic factors, but less so strategic factors. A country’s vulnerability to climate change, its power and its democratic status are among the best predictors of its choice of negotiation position; its international interconnectedness, on the other hand, does not seem to have an influence. By comparing two negotiation issues – reducing emissions and financing climate mitigation – we can show that democracies choose rather different negotiation positions. When it comes to compensation mechanisms, democracies do not commit to substantial emission reduction targets due to pressure from industry at home. They are, however, more prepared than other states to pay for projects that help to reduce emissions. By understanding the choice of negotiation positions we can thus explain why the more or less cooperative bargaining positions adopted by states led to a breakdown of the Copenhagen negotiations. We investigated this question using a novel dataset on the UNFCCC negotiations, in which the positions of all participating governments were collected by hand-coding protocols from the negotiations as well as expert interviews with negotiators