Streaming Emergency Department Patients to Primary Care Services: Developing a Consensus in North East London

Report of local research on emergency care decision

Changes in an Enzyme Ensemble During Catalysis Observed by High Resolution XFEL Crystallography

Enzymes populate ensembles of structures with intrinsically different catalytic proficiencies that are difficult to experimentally characterize. We use time-resolved mix-and-inject serial crystallography (MISC) at an X-ray free electron laser (XFEL) to observe catalysis in a designed mutant (G150T) isocyanide hydratase (ICH) enzyme that enhances sampling of important minor conformations. The active site exists in a mixture of conformations and formation of the thioimidate catalytic intermediate selects for catalytically competent substates. A prior proposal for active site cysteine charge-coupled conformational changes in ICH is validated by determining structures of the enzyme over a range of pH values. A combination of large molecular dynamics simulations of the enzyme in crystallo and timeresolved electron density maps shows that ionization of the general acid Asp17 during catalysis causes additional conformational changes that propagate across the dimer interface, connecting the two active sites. These ionization-linked changes in the ICH conformational ensemble permit water to enter the active site in a location that is poised for intermediate hydrolysis. ICH exhibits a tight coupling between ionization of active site residues and catalysis-activated protein motions, exemplifying a mechanism of electrostatic control of enzyme dynamics

VALTIVE1: Validation of Tie2 as a response biomarker for VEGF inhibitors In Ovarian Cancer

Background Studies in ovarian cancer (OC) show that the addition of anti-angiogenic VEGFi, such as bevacizumab, to cytotoxic chemotherapy improves Progression Free Survival (PFS) and, in some cases, Overall Survival (OS). Notwithstanding the beneficial effects of VEGFi for OC patients, informative biomarkers could help optimise their use and improve patient selection. We have carried out biomarker studies in ovarian and gastrointestinal cancer trials, in which patients were treated with cytotoxic agents and bevacizumab. Plasma samples were analysed to determine changes in Tie2 concentration during treatment. We have shown that a reduction of at least 25% in plasma Tie2 concentrations on-treatment over 9 weeks predicts a significant PFS benefit from bevacizumab, whereas an immediate increase in Tie2 of over 10% after treatment starts denotes resistance to bevacizumab and hence lack of benefit. In patients who do achieve a bevacizumab response, an increase in plasma Tie2 that is at least 40% above the nadir concentration signifies the onset of resistance. The VALTIVE1 study aims to optimise the frequency and number of plasma samples for a better definition of Tie2 “vascular response” and to evaluate acceptability of a future randomised discontinuation study to evaluate Tie2 as a predictive biomarker, thus completing the CRUK biomarker roadmap. Method VALTIVE1 is a multi-centre, single arm, non-interventional biomarker study, which will enrol 176 adult patients, who are receiving first line platinum-based chemotherapy and bevacizumab for high risk ovarian cancer, from 15 UK centres. VALTIVE1 participants will provide blood samples before and during treatment with bevacizumab and upon disease progression. Cross-sectional imaging of pelvis and abdomen will be performed and reported according to RECIST v.1.1 during treatment until disease progression, death, or withdrawal of consent, whichever occurs first. The primary endpoint is assessment of PFS difference between Tie2-defined vascular responders and Tie2 defined vascular non-responders. Results N/A Conclusion The results of VALTIVE1 will underpin the design of a subsequent randomised study, VALTIVE2, in which OC patients receiving bevacizumab will be randomly allocated to the conventional 12 months of VEGFi therapy or Tie2-guided bevacizumab therapy. Impact statement Validation of plasma Tie2 for clinical decision making around the use of VEGF inhibitors in the NH

Progresso genético no melhoramento da aveia-branca no Sul do Brasil Genetic progress in oat breeding in Southern Brazil

As cultivares de aveia-branca (Avena sativa L.) cultivadas no sul do Brasil até princípios da década de 80 eram provenientes do Uruguai e da Argentina, apresentando problemas de adaptação ao ambiente de cultivo. A partir dos anos 70, programas de melhoramento começaram a produzir suas próprias populações segregantes, possibilitando o lançamento em escala comercial de cerca de 35 cultivares. Com o objetivo de estimar o progresso genético nos programas de melhoramento de aveia-branca do sul do Brasil, foi realizado um experimento envolvendo 15 cultivares lançadas em diferentes épocas, em dois locais, com quatro diferentes condições de manejo. Os resultados obtidos indicaram progresso genético linear para os caracteres ciclo vegetativo, rendimento de grãos, peso de grão e peso do hectolitro; a inexistência de efeitos quadráticos significativos sugeriram a possibilidade de ganhos posteriores a partir da seleção de novos genótipos. Os programas de melhoramento genético de aveia-branca do sul do Brasil, embora ainda não tenham atingido o patamar máximo, têm sido eficientes em produzir novas cultivares com maiores rendimento e qualidade de grãos e com caracteres agronômicos superiores.<br>The oat (Avena sativa L.) cultivars cultivated in Southern Brazil up to the beginning of the 80's were introduced from Uruguay and Argentina. They presented adaptation problems to the new environment. Starting from the 70's, oat breeding programs began to produce their own segregant populations. These programs already released 35 cultivars. Aiming to estimate the genetic progress in oat breeding programs from southern Brazil, an experiment with 15 cultivars released in different times was conducted in two locations using four different cultural practices. The results indicated linear genetic progress for days to flowering, grain yield, grain weight and test weight. The non significance of quadratic effects suggested the possibility of additional gains through selection of new genotypes. The oat breeding programs in southern Brazil have been efficient in producing new cultivars with higher grain yield, good grain quality, and with superior agronomic traits. However, a maximum breeding plateau was not reached for this species

Changes in an Enzyme Ensemble During Catalysis Observed by High Resolution XFEL Crystallography

Enzymes populate ensembles of structures with intrinsically different catalytic proficiencies that are difficult to experimentally characterize. We use time-resolved mix-and-inject serial crystallography (MISC) at an X-ray free electron laser (XFEL) to observe catalysis in a designed mutant (G150T) isocyanide hydratase (ICH) enzyme that enhances sampling of important minor conformations. The active site exists in a mixture of conformations and formation of the thioimidate catalytic intermediate selects for catalytically competent substates. A prior proposal for active site cysteine charge-coupled conformational changes in ICH is validated by determining structures of the enzyme over a range of pH values. A combination of large molecular dynamics simulations of the enzyme in crystallo and time-resolved electron density maps shows that ionization of the general acid Asp17 during catalysis causes additional conformational changes that propagate across the dimer interface, connecting the two active sites. These ionization-linked changes in the ICH conformational ensemble permit water to enter the active site in a location that is poised for intermediate hydrolysis. ICH exhibits a tight coupling between ionization of active site residues and catalysis-activated protein motions, exemplifying a mechanism of electrostatic control of enzyme dynamics