Hasil untuk "Chemistry"

C. Yap

M. Kuhn

The caret package, short for classification and regression training, contains numerous tools for developing predictive models using the rich set of models available in R. The package focuses on simplifying model training and tuning across a wide variety of modeling techniques. It also includes methods for pre-processing training data, calculating variable importance, and model visualizations. An example from computational chemistry is used to illustrate the functionality on a real data set and to benchmark the benefits of parallel processing with several types of models.

R. Bader

C. Adamo, V. Barone

B. Halliwell, J. Gutteridge

S. Wold, M. Sjöström, L. Eriksson

M. Andreae, P. Merlet

C. Anfinsen

Michael W. Schmidt, K. Baldridge, J. Boatz et al.

J. Bernstein, Raymond E. Davis, L. Shimoni et al.

G. Schatz, K. Kelly, E. Coronado et al.

C. Appelo, D. Postma

W. Saenger

M. Morari, E. Zafiriou

J. Houghton, G. Jenkins, J. J. Ephraums

G. F.

R. Crabtree

Saranya Prashath

Abstract L-arginine (L-Arg) is metabolised in the cell to generate nitric oxide (NO) and citrulline via nitric oxide synthase (NOS). NO is an important cellular signalling molecule that regulates lipid and glucose metabolism. The biological availability of NO is affected by the NOS inhibitor; NG-nitro-L-Arg methyl ester (L-NAME) and the external NO donor; S-nitroso-N-acetyl-D, L-penicillamine (SNAP). Mouse adipocyte 3T3 L1 cells were cultured with 0, 400 and 800 µM L-Arg or control complete DMEM media. The impact of L-NAME (4 mM), and SNAP (100 µM) was also analysed. The cell fitness was similar and the mRNA levels of AMPK was increased and ACC-1 was decreased, whilst the activation of AMPK and ACC-1 was decreased upon the addition of exogenous L-Arg. Transcript and protein levels of AMPK and ACC-1 were regulated by addition of L-NAME and SNAP, however the impact of these targets was related to the concentration of L-Arg added to the cells and the culture time point of analysis. NO in the form of NO2 − in cell culture supernatant was elevated in 400 and 800 µM L-Arg cultures. L-NAME significantly inhibited NO production from adipose cells in a time-dependent manner and subsequently impacted AMPK and ACC expression. Associated with these changes were changed in the concentration of L-Arg, L-Cit and L-Orn in the culture media. Collectively, these results show that excess L-Arg is sensed by the cell which then regulates AMPK and ACC-1 expression in response. The findings could have implications in modulation of signalling pathways for treating obesity and obesity induced diabetic mellitus.

Prem Rajak, Abhratanu Ganguly, Sayantani Nanda

Oxidative stress is a detrimental condition that occurs when there is an imbalance between sub-cellular antioxidants and free radicals. Endogenous antioxidants actively scavenge free radicals and prevent oxidative stress. Pesticides can affect antioxidant activities. However, molecular interactions between the pesticides and endogenous antioxidants are not clear. Hence, objective of the present study is to dissect the intermolecular interactions between the widely-used pesticides (4,4′-dichlorodiphenyldichloroethylene, 4,4′-DDE; imidacloprid, IMD; lambda-cyhalothrin, CYH; malathion, MAL) and major antioxidant enzymes (Glutathione peroxidase-4, Glutathione S-Transferase, Catalase, Glutathione reductase, Superoxide dismutase-1) that might be responsible for altered enzyme activities and induction of oxidative stress. The binding affinity analysis using AutoDock vina and Discovery Studio Visualizer was conducted to unveil the potential intermolecular interactions between the pesticides and antioxidants. In the results, 4,4′-DDE, IMD, CYH, and MAL interacted with the antioxidants through stable hydrogen bonds, carbon-hydrogen bonds, van der Waals, and other hydrophobic interactions. Additionally, considerable binding affinities between the pesticides and enzymes were noted. ADME analyses have also revealed that the majority of pesticides can cross GI, exhibit low to high water solubility, and follow Lipinski's rule. Hence, results of the present study suggest that pesticides can potentially interact with antioxidants to modulate their catalytic activity and induce oxidative stress.

Alexandru Rusu, Octavian Groza, Nicolae Popa et al.

This study evaluates the impact of different territorial contexts on academic mobility within the framework of the Erasmus Programme, using data on Key Action 1 exchanges between 2015 and 2023. Using official EU datasets and a gravity model framework, the research investigates how economic performance, geographical distance, EU membership, AUF (Agence Universitaire de la Francophonie) regional affiliation, and state contiguity shape international academic flows. The research developed two gravity models: one aimed to measure the potential barriers to academic flows through a residuals analysis, and the second integrated territorial delineations as predictors. In both models, the core of the explanatory variable is formed by indicators describing the economic performance of states and the distance between countries. When applied, the models converge in emphasizing that the inclusion of states in different territorial configurations has a strong effect on the structuring of academic flows. This suggests that the Erasmus Programme exhibits trends of overconcentration of flows in a limited number of countries, questioning the need for a more polycentric strategy and a reshaping of the funding mechanisms. Even if the gravity models behave well, given the limited number of predictors, further studies may need to incorporate qualitative indicators for a more comprehensive evaluation of the interactions.