Solvent accessibility in interdigitated and micellar phases formed by DPPC/Lyso-PPC mixtures: D2O-ESEEM of chain labeled lipids

Aloi, Erika; Bartucci, Rosa

doi:10.1016/j.chemphyslip.2019.03.005

Cited by 3 publications

(2 citation statements)

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“…Correspondences similar to those for water accessibility are found also for the polarity-dependent values of A zz in the presence and absence of ouabain (39,(42)(43)(44).…”

Section: Eseem Intensities: Water Accessibility In Inhibitor Binding Sitesupporting

confidence: 70%

“…The latter is comparable to D 2 O-ESEEM intensities found for spin labels attached to surface -SH groups on the Na + ,K + -ATPase ( 39 , 40 ) and other proteins ( 41 ). In the membrane, intensities are comparable to those of lipids spin labeled at the n = 6−8 chain position, or 9−10 for the short-linked B8 and C8 ( 9 , 42 , 43 , 44 ), and reflect the limited partitioning of water into the hydrophobic interior. In turn, this is reflected in relative values of the product K [W] between H-bond association constant and free water concentration, which essentially becomes scaled by the water-membrane partition coefficient K P , i.e., K eff = K × K P .…”

Section: Discussionmentioning

confidence: 90%

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Geometry and water accessibility of the inhibitor binding site of Na+-pump: Pulse- and CW-EPR study

Aloi

Guo

Guzzi

et al. 2021

Biophysical Journal

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Spin labels based on cinobufagin, a specific inhibitor of the Na,K-ATPase, have proved valuable tools to characterize the binding site of cardiotonic steroids (CTSs), which also constitutes the extracellular cation pathway. Because existing literature suggests variations in the physiological responses caused by binding of different CTSs, we extended the original set of spin-labeled inhibitors to the more potent bufalin derivatives. Positioning of the spin labels within the Na,K-ATPase site was defined and visualized by molecular docking. Although the original cinobufagin labels exhibited lower affinity, continuouswave electron paramagnetic resonance spectra of spin-labeled bufalins and cinobufagins revealed a high degree of pairwise similarity, implying that these two types of CTS bind in the same way. Further analysis of the spectral lineshapes of bound spin labels was performed with emphasis on their structure (PROXYL vs. TEMPO), as well as length and rigidity of the linkers. For comparable structures, the dynamic flexibility increased in parallel with linker length, with the longest linker placing the spin label at the entrance to the binding site. Temperature-related changes in spectral lineshapes indicate that six-membered nitroxide rings undergo boat-chair transitions, showing that the binding-site cross section can accommodate the accompanying changes in methyl-group orientation. D 2 O-electron spin echo envelope modulation in pulse-electron paramagnetic resonance measurements revealed high water accessibilities and similar polarity profiles for all bound spin labels, implying that the vestibule leading to steroid-binding site and cation-binding sites is relatively wide and water-filled.

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“…Correspondences similar to those for water accessibility are found also for the polarity-dependent values of A zz in the presence and absence of ouabain (39,(42)(43)(44).…”

Section: Eseem Intensities: Water Accessibility In Inhibitor Binding Sitesupporting

confidence: 70%