Synechococcus sp. PCC 7002 CpcB lyase null mutations alter phycocyanin chromophore function and, consequently, affect the redistribution of excitation energy via the light state transition /

Phycobilisomes are the major light harvesting complexes for cyanobacteria and phycocyanin is the primary phycobiliprotein of the phycobilisome rod. The phycocyanobilin lyases responsible for chromophorylating the phycocyanin p subunit (CpcB) have been recently identified in the cyanobacterium Synechococcus sp. PCC 7002. Surprisingly, mutants missing the CpcB lyases were nevertheless capable of producing pigmented phycocyanin. 10K absorbance measurements revealed that the energy states of the p phycocyanin chromophores were only subtly shifted; however, 77K steady state fluorescence emission spectroscopy showed excitation energy transfer involving the targeted chromophores to be highly disrupted. Such evidence suggests that phycobilin orientation within the binding domain is specifically modified. We hypothesized that alternate, less specific lyases are able to act on the p binding sites. A phycocyanin linker-polypeptide deficient mutant was similarly characterized. The light state transition, a short term adaptation of the photosynthetic light harvesting apparatus resulting in the redistribution of excitation energy among the photo systems, was shown to be dominated by the reallocation of phycocyanin-absorbed excitation energy. Treatment with a high M phosphate buffer effectively prevented the redistribution of both chlorophyll a- and phycobilisome- absorbed excitation energy, suggesting that the two effects are not strictly independent. The mutant strains required a larger redistribution of excitation energy between light states, perhaps to compensate for their loss in phycobilisome antenna function.

Can a Manipulated Mind Alter Matter? : The Effects of Verbal Feedback on Self-Efficacy, Exercise Intention, and Exercise Behaviour among Low-Active College-Aged Women

Self-efficacy (SE), a person’s confidence in the ability to perform a task, is an important predictor of the adoption and maintenance of physical activity. The present study examined the effects of SE manipulated through verbal persuasion on exercise intentions and behaviour during a 4-week follow-up period and investigated the role of social physique anxiety (SPA) as a moderator. Female college infrequent exercisers (n = 66) were randomly assigned into one of three groups (high-efficacy [HE], low-efficacy [LE], or control) and asked to complete several questionnaires at baseline. The HE and LE groups were provided with positive and negative exercise adherence feedback, respectively. The HE group reported higher SE from pre- to post-feedback. Both the HE and LE groups reported increases in exercise behaviour at the 4-week follow-up. Pre- to post-feedback changes in SE, exercise intention, and exercise behaviour did not depend on level of SPA reported.