Factors Controlling the Redox Potential of ZnCe6 in an Engineered Bacterioferritin Photochemical ‘Reaction Centre’

Photosystem II (PSII) of photosynthesis has the unique ability to photochemically oxidize water. Recently an engineered bacterioferritin photochemical ‘reaction centre’ (BFR-RC) using a zinc chlorin pigment (ZnCe₆) in place of its native heme has been shown to photo-oxidize bound manganese ions through a tyrosine residue, thus mimicking two of the key reactions on the electron donor side of PSII. To understand the mechanism of tyrosine oxidation in BFR-RCs, and explore the possibility of water oxidation in such a system we have built an atomic-level model of the BFR-RC using ONIOM methodology. We studied the influence of axial ligands and carboxyl groups on the oxidation potential of ZnCe₆ using DFT theory, and finally calculated the shift of the redox potential of ZnCe₆ in the BFR-RC protein using the multi-conformational molecular mechanics–Poisson-Boltzmann approach. According to our calculations, the redox potential for the first oxidation of ZnCe₆ in the BRF-RC protein is only 0.57 V, too low to oxidize tyrosine. We suggest that the observed tyrosine oxidation in BRF-RC could be driven by the ZnCe₆ di-cation. In order to increase the efficiency of tyrosine oxidation, and ultimately oxidize water, the first potential of ZnCe₆ would have to attain a value in excess of 0.8 V. We discuss the possibilities for modifying the BFR-RC to achieve this goal.     

The influence of antidiabetic medications on the development and progression of prostate cancer

BackgroundThe development of prostate tumors has been linked to co-morbid diabetes mellitus (DM) in several studies, potentially through the stimulation of insulin-like growth factor receptor (IGFR). This study evaluates the effect of anti-diabetic medication use on the development of high grade tumors and time to tumor progression compared to non-diabetics.MethodsThis retrospective, nested case control study identified patients with prostate cancer (PCa) from the Kentucky Medicaid Database. Cases were diagnosed with PCa and DM and using at least one of the following antidiabetic medications; sulfonylureas, insulin, metformin or TZDs. Cases were further stratified on their insulin exposure resulting from therapy. Controls were those with PCa without DM or any anti-diabetic medications.ResultsThe use of metformin or TZDs trended toward decreased odds of high-grade tumors and decreased risk of progression, while sulfonylureas and high-dose insulin tended toward an increased odds of high-grade tumors and increase the risk of progression compared to non-diabetics.ConclusionsFuture studies should be conducted to further evaluate the effects of anti-diabetic medications on tumor grade and time to prostate cancer progression.     

Diversity within cyanobacterial mat communities in variable salinity meltwater ponds of McMurdo Ice Shelf, Antarctica

This study investigated the diversity of cyanobacterial mat communities of three meltwater ponds--Fresh, Orange and Salt Ponds, south of Bratina Island, McMurdo Ice Shelf, Antarctica. A combined morphological and genetic approach using clone libraries was used to investigate the influence of salinity on cyanobacterial diversity within these ecosystems without prior cultivation or isolation of cyanobacteria. We were able to identify 22 phylotypes belonging to Phormidium sp., Oscillatoria sp. and Lyngbya sp. In addition, we identified Antarctic Nostoc sp., Nodularia sp. and Anabaena sp. from the clone libraries. Fresh (17 phylotypes) and Orange (nine phylotypes) Ponds showed a similar diversity in contrast to that of the hypersaline Salt Pond (five phylotypes), where the diversity within cyanobacterial mats was reduced. Using the comparison of identified phylotypes with existing Antarctic sequence data, it was possible to gain further insight into the different levels of distribution of phylotypes identified in the investigated cyanobacterial mat communities of McMurdo Ice Shelf.     

Structural-functional role of chloride in photosystem II

Chloride binding in photosystem II (PSII) is essential for photosynthetic water oxidation. However, the functional roles of chloride and possible binding sites, during oxygen evolution, remain controversial. This paper examines the functions of chloride based on its binding site revealed in the X-ray crystal structure of PSII at 1.9 ? resolution. We find that chloride depletion induces formation of a salt bridge between D2-K317 and D1-D61 that could suppress the transfer of protons to the lumen.     

Role of MAPK/ERK in Neurotrophin-4 Potentiation of Necrotic Neuronal Death

Neurotrophic factors have been proposed for the treatment of a variety of neurological diseases. However, to this point they have failed in clinical trials. One potential problem is that while neurotrophic factors attenuate apoptosis, they have the potential to enhance necrosis. In this study we show that neurotrophin-4 (NT-4) attenuated apoptotic neuronal death while potentiating necrotic neuronal death in cortical cultures. The protective effects of NT-4 were not blocked by the mitogen-activated protein kinase kinase (MEK) inhibitors PD098059 or U0126, while the injury potentiation by NT-4 was blocked by these inhibitors. NT-4 stimulated the phosphorylation of ERK1/2 and this phosphorylation was attenuated by U0126 and PD098059. The results indicate a disassociation between the pathway by which NT-4 potentiates necrosis, and that by which it attenuates apoptosis, and suggest that addition of a MEK inhibitor may enhance the beneficial effects of NT-4 in treating complex injuries such as occur in vivo.     

A calcaneus attributable to the primitive late eocene anthropoid Proteopithecus sylviae: Phenetic affinities and phylogenetic implications

A well‐preserved calcaneus referrable to Proteopithecus sylviae from the late Eocene Quarry L‐41 in the Fayum Depression, Egypt, provides new evidence relevant to this taxon's uncertain phylogenetic position. We assess morphological affinities of the new specimen using three‐dimensional geometric morphometric analyses with a comparative sample of primate calcanei representing major extinct and extant radiations (n = 58 genera, 106 specimens). Our analyses reveal that the calcaneal morphology of Proteopithecus is most similar to that of the younger Fayum parapithecid Apidium. Principal components analysis places Apidium and Proteopithecus in an intermediate position between primitive euprimates and crown anthropoids, based primarily on landmark configurations corresponding to moderate distal elongation, a more distal position of the peroneal tubercle, and a relatively “unflexed” calcaneal body. Proteopithecus and Apidium are similar to cercopithecoids and some omomyiforms in having an ectal facet that is more tightly curved, along with a larger degree of proximal calcaneal elongation, whereas other Fayum anthropoids, platyrrhines and adapiforms have a more open facet with less proximal elongation. The similarity to cercopithecoids is most plausibly interpreted as convergence given the less tightly curved ectal facets of stem catarrhines. The primary similarities between Proteopithecus and platyrrhines are mainly in the moderate distal elongation and the more distal position of the peroneal tubercle, both of which are not unique to these groups. Proteopithecus and Apidium exhibit derived anthropoid features, but also a suite of primitive retentions. The calcaneal morphology of Proteopithecus is consistent with our cladistic analysis, which places proteopithecids as a sister group of Parapithecoidea. Am J Phys Anthropol 151:372–397, 2013.© 2013 Wiley Periodicals, Inc.     

Enveloped virus inactivation using neutral arginine solutions and applications in therapeutic protein purification processes

For the manufacturing of recombinant protein therapeutics produced from mammalian cell culture, demonstrating the capacity of the purification process to effectively clear infectious viruses is a regulatory requirement. At least two process steps, using different mechanisms of virus removal and/or inactivation, should be validated in support of the regulatory approval process. For example, exposure of the product stream to low pH, detergents or solvent/detergent combinations is commonly incorporated in protein purification processes for the inactivation of lipid‐enveloped viruses. However, some proteins have limited stability at low pH or in the presence of the detergents, and alternative techniques for achieving the inactivation of enveloped viruses would be beneficial. We present here an alternative and novel approach for the rapid inactivation of enveloped viruses using pH‐neutral buffer solutions containing arginine. The implementation of this approach in a monoclonal antibody or Fc‐fusion protein purification process is described and illustrated with several different therapeutic proteins. The use of the neutral pH arginine solution was able to effectively inactivate two enveloped model viruses, with no measurable effect on the product quality of the investigated proteins. Thus, the use of pH‐neutral arginine containing buffer solutions provides an alternative means of virus inactivation where other forms of virus inactivation, such as low pH and/or solvent/detergent treatments are not possible or undesirable due to protein stability limitations. © 2013 American Institute of Chemical Engineers Biotechnol. Prog., 30:108–112, 2014