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Cyclodextrins are cage-shaped molecules having the remarkable ability to trap smaller compounds, and have thus led to applications in many disciplines such as medicine to increase the bioavailability of hydrophobic drugs. This historical review summarizes the outstanding contribution of the late Professor Benito Casu to cyclodextrin research and, more generally, to the chemistry and biochemistry of linear and cyclic oligosaccharides, polysaccharides, glycosaminoglycans, and heparin. Professor Casu was the first to elucidate the structure and conformations of cyclodextrins by infrared spectroscopy and proton nuclear magnetic resonance (NMR). In particular, he showed that trapped compounds induced a shift of H peaks in NMR due to the shielding effect of cyclodextrins. He also demonstrated that the d-glucopyranose cyclodextrin units are in the C-1 chair conformation by analyzing α-cyclodextrin by NMR in dimethylsulfoxide-d6.
相似文献Increasing severe and persistent ozone pollution in China has resulted in serious harm to human health in recent years, yet the precise pollution sources are poorly known because there is few knowledge on large-scale extreme ozone episodes. Here, we studied the formation of the historical orange-alert regional ozone episode in eastern China on 6 June, 2021, by combining process analysis, integrated source apportionment modelling, and chemical and meteorological data. Results show that during the pollution episode, 94% of cities in eastern China suffered ozone pollution, and 39% had daily maximum 8-h average ozone concentrations higher than 100 ppb. This is explained by favorable local ozone formation and transports provided by the prevailing northwestern winds in the upper air, and by sinking atmospheric motions favoring the persistence of high surface ozone concentrations. During daytime, local photochemical production induced an ozone increase of 0.3–28.4 ppb h?1 and vertical transport induced an ozone increase of 0.4–56.1 ppb h?1. As a consequence, vertical downward transport of ozone generated in the upper air by photochemical reactions aggravated surface ozone pollution. Surface ozone concentrations include 25.8–53.9% of ozone from local provincial emissions, 0–42.6% of ozone from inter-regional transports from neighboring regions, 4.6–23.1% of ozone from outer-regional transport, and 13.6–52.9% of ozone from boundary conditions in the selected cities. Overall, our findings show that favorable meteorological conditions promoted the chemical productions of ozone on the surface and at high altitudes, thus resulting in this heavy ozone pollution. In addition, regional and vertical downward transports of aloft ozone further aggravated the surface ozone pollution, leading to the large-scale extreme ozone pollution episode.
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