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- Cremer, Dieter, 1944, et al.
(author)
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The ozone-acetylene reaction: Concerted or non-concerted reaction mechanism? A quantum chemical investigation
- 2001
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In: Chemical Physics Letters. - 0009-2614. ; 347, s. 268-276
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Journal article (peer-reviewed)abstract
- The ozone-acetylene reaction is found to proceed via an intermediate van der Waals complex (rather than a biradical), which is the precursor for a concerted symmetry-allowed [4+2] cycloaddition reaction leading to 1,2,3-trioxolene. CCSD(T)/6-311G+(2d,2p) and CCSD(T)/CBS (complete basis set) calculations predict the ozone-acetylene van der Waals complex to be stable by 2.2 kcalmol -1 , the calculated activation enthalpy for the cycloaddition reaction is 9.6 kcalmol -1 and the reaction enthalpy -55.5 kcalmol -1 . Calculated kinetic data for the overall reaction (k=0.8lmol -1 s -1 , A=1.71×10 6 lmol -1 s -1 , E a =8.6kcalmol -1 ) suggest that there is a need for refined kinetic measurements. © 2001 Elsevier Science B.V.
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- Tidemand Johansen, Nicolai, et al.
(author)
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Mg2+-dependent conformational equilibria in CorA and an integrated view on transport regulation
- 2022
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In: eLIFE. - 2050-084X. ; 11
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Journal article (peer-reviewed)abstract
- The CorA family of proteins regulates the homeostasis of divalent metal ions in many bacteria, archaea, and eukaryotic mitochondria, making it an important target in the investigation of the mechanisms of transport and its functional regulation. Although numerous structures of open and closed channels are now available for the CorA family, the mechanism of the transport regulation remains elusive. Here, we investigated the conformational distribution and associated dynamic behaviour of the pentameric Mg2+ channel CorA at room temperature using small-angle neutron scattering (SANS) in combination with molecular dynamics (MD) simulations and solid-state nuclear magnetic resonance spectroscopy (NMR). We find that neither the Mg2+-bound closed structure nor the Mg2+-free open forms are sufficient to explain the average conformation of CorA. Our data support the presence of conformational equilibria between multiple states, and we further find a variation in the behaviour of the backbone dynamics with and without Mg2+. We propose that CorA must be in a dynamic equilibrium between different non-conducting states, both symmetric and asymmetric, regardless of bound Mg2+ but that conducting states become more populated in Mg2+-free conditions. These properties are regulated by backbone dynamics and are key to understanding the functional regulation of CorA.
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