Effects of COVID-19 Restriction Policies on Urban Heat Islands in Some European Cities: Berlin, London, Paris, Madrid, and Frankfurt.

The present study investigates the effects of policies restricting human activities during the COVID-19 epidemic on the characteristics of Night Land Surface Temperature (NLST) and Night Urban Heat Islands (NUHI) in five major European cities. In fact, the focus of this study was to explore the role of anthropogenic factors in the formation and intensity of NUHI. The effect of such factors was uncontrollable before the COVID-19 outbreak on the global scale and in a real non-laboratory environment. In this study, two indices, the concentration of Nitrogen dioxide (NO2) and Nighttime Lights (NL), were used as indicators of the number of anthropogenic activities. The data were collected before the COVID-19 outbreak and after its prevalence in 2019-2020. A Paired samples t-test and a Pearson correlation were used to examine the differences or significant relationships between the variables and indicators studied throughout the two periods. The results of the study confirmed a direct and significant relationship between NO2 and NL indices and the NUHI and NLST variables; however, using strict restrictions during the COVID-19 pandemic, the NO2 and NL indices decreased seriously, leading to significant changes in the characteristics of the NUHI and NLST in the five cities. This study has some implications for urban planners and politicians, e.g., the environmental impacts of changing the nature and level of anthropogenic activities can greatly affect the pattern and intensity of the Urban Heat Islands (UHIs) (as a serious environmental challenge).

Atypical muscarinic allosteric modulation: cooperativity between modulators and their atypical binding topology in muscarinic M2 and M2/M5 chimeric receptors.

The binding and function of muscarinic acetylcholine receptors can be modulated allosterically. Some allosteric muscarinic ligands are "atypical", having steep concentration-effect curves and not interacting competitively with "typical" allosteric modulators. For atypical agents, a second allosteric site has been proposed. Different approaches have been used to gain further insight into the interaction with M2 receptors of two atypical agents, tacrine and the bispyridinium compound 4,4'-bis-[(2,6-dichloro-benzyloxy-imino)-methyl]-1,1'-propane-1,3-diyl-bispyridinium dibromide (Duo3). Interaction studies, using radioligand binding assays and the allosteric ligands obidoxime, Mg2+, and the new tool hexamethonium to antagonize the allosteric actions of the atypical ligands, showed different modes of interaction for tacrine and Duo3 at M2 receptors. A negatively cooperative interaction was observed between hexamethonium and tacrine (but not Duo3). A tacrine dimer that exhibited increased allosteric potency relative to tacrine but behaved like a typical allosteric modulator was competitively inhibited by hexamethonium. M2/M5-receptor mutants revealed a dependence of tacrine and Duo3 affinity on different receptor epitopes. This was confirmed by docking simulations using a three-dimensional model of the M2 receptor. These showed that the allosteric site could accommodate two molecules of tacrine simultaneously but only one molecule of Duo3, which binds in different mode from typical allosteric agents. Therefore, the atypical actions of tacrine and Duo3 involve different modes of receptor interaction, but their sites of attachment seem to be the "common" allosteric binding domain at the entrance to the orthosteric ligand binding pocket of the M2-receptor. Additional complex behavior may be rationalized by allosteric interactions transmitted within a receptor dimer.