Uridine-derived ribose fuels glucose-restricted pancreatic cancer.

Pancreatic ductal adenocarcinoma (PDA) is a lethal disease notoriously resistant to therapy1,2. This is mediated in part by a complex tumour microenvironment3, low vascularity4, and metabolic aberrations5,6. Although altered metabolism drives tumour progression, the spectrum of metabolites used as nutrients by PDA remains largely unknown. Here we identified uridine as a fuel for PDA in glucose-deprived conditions by assessing how more than 175 metabolites impacted metabolic activity in 21 pancreatic cell lines under nutrient restriction. Uridine utilization strongly correlated with the expression of uridine phosphorylase 1 (UPP1), which we demonstrate liberates uridine-derived ribose to fuel central carbon metabolism and thereby support redox balance, survival and proliferation in glucose-restricted PDA cells. In PDA, UPP1 is regulated by KRAS-MAPK signalling and is augmented by nutrient restriction. Consistently, tumours expressed high UPP1 compared with non-tumoural tissues, and UPP1 expression correlated with poor survival in cohorts of patients with PDA. Uridine is available in the tumour microenvironment, and we demonstrated that uridine-derived ribose is actively catabolized in tumours. Finally, UPP1 deletion restricted the ability of PDA cells to use uridine and blunted tumour growth in immunocompetent mouse models. Our data identify uridine utilization as an important compensatory metabolic process in nutrient-deprived PDA cells, suggesting a novel metabolic axis for PDA therapy

Review of the Palaearctic species of Ismaridae Thomson, 1858 (Hymenoptera: Diaprioidea)

This is an open access article, available to all readers online, published under a Creative Commons BY-NC-ND license: https://creativecommons.org/licenses/by-nc-nd/3.0/. The attached file is the published version of the article

Polymeric dibromomaleimides as extremely efficient disulfide bridging bioconjugation and pegylation agents

A series of dibromomaleimides have been shown to be very efficacious at insertion into peptidic disulfide bonds. This conjugation proceeds with a stoichiometric balance of reagents in buffered solutions in less than 15 min to give discrete products while maintaining the disulfide bridge and thus peptide conformation. The insertion is initiated by disulfide reduction using a water-soluble phosphine, tris(2-carboxyethyl)phosphine (TCEP) which allows for subsequent substitution of the two maleimide bromides by the generated thiols. Reaction of salmon calcitonin (sCT) with 2,3-dibromomaleimide (1.1 excess) in the presence of TCEP (1.1 equiv) in aqueous solution at pH 6.2 gives complete production of a single conjugate which requires no workup. A linear methoxy poly(ethylene glycol) (PEG) was functionalized via a Mitsunobu reaction and used for the successful site-specific and rapid pegylation of sCT. This reaction occurs in 15 min with a small stoichiometry excess of the pegylating agent to give insertion at the disulfide with HPLC showing a single product and MALDI-ToF confirming conjugation. Attempts to use the group in a functional ATRP polymerization initiator led to polymerization inhibition. Thus, in order to prepare a range of functional polymers an indirect route was chosen via both azide and aniline functional initiators which were converted to 2,3-dibromomaleimides via appropriate reactions. For example, the azide functional polymer was reacted via a Huisgen CuAAC click reaction to an alkyne functional 2,3-dibromomaleimide. This new reagent allowed for the synthesis of conjugates of sCT with comb polymers derived from PEG methacrylic monomers which in addition gave appropriate cloud points. This reaction represents a highly efficient polymer conjugation method which circumvents problems of purification which normally arise from having to use large excesses of the conjugate. In addition, the tertiary structure of the peptide is efficiently maintained

Sequential phosphine-catalyzed, nucleophilic thiol ene/radical-mediated thiol-yne reactions and the facile orthogonal synthesis of polyfunctional materials

The first example of highly efficient sequential thiol-ene/thiol-yne reactions conducted in an orthogonal manner is presented and its broad application in the synthesis of polyfunctional materials demonstrated. The anionic chain mechanism of the phosphine-mediated thiol-ene reaction is highlighted, as is the radical-mediated thiol-yne reaction. Kinetic data for a model reaction are presented, followed by a discussion of the synthesis of a range of materials with diverse functionality, including an example of potential biomedical significance. © 2009 American Chemical Society

Reversible switching between nonquenched and quenched states in nanoscale linear arrays of plant light-harvesting antenna complexes

A simple and robust nanolithographic method that allows sub-100 nm chemical patterning on a range of oxide surfaces was developed in order to fabricate nanoarrays of plant light-harvesting LHCII complexes. The site-specific immobilization and the preserved functionality of the LHCII complexes were confirmed by fluorescence emission spectroscopy. Nanopatterned LHCII trimers could be reversibly switched between fluorescent and quenched states by controlling the detergent concentration in the imaging buffer. A 3-fold quenching of the average fluorescence intensity was accompanied by a decrease in the average (amplitude-weighted) fluorescence lifetime from approximately 2.24 ns to approximately 0.4 ns, attributed to the intrinsic ability of LHCII to switch between fluorescent and quenched states upon changes in its conformational state. The nanopatterning methodology was extended by immobilizing a second protein, the enhanced green fluorescent protein (EGFP), onto LHCII-free areas of the chemically patterned surfaces. This very simple surface chemistry, which allows simultaneous selective immobilization and therefore sorting of the two types of protein molecules on the surface, is a key underpinning step toward the integration of LHCII into switchable biohybrid antenna constructs