Partielle Entfaltung von T4‐Lysozym auf einer Quarzoberfläche: Analyse der Strukturänderungen adsorbierter Proteine durch ESR‐Spektroskopie

Abstract:The catalytic asymmetric inverse-electrondemand (IED) [4 + 2] cycloaddition of various salicylaldehyde-derived N-arylimines with electron-rich alkenes in the presence of chiral BINOL-derived phosphoric acid catalysts has been studied with the aim of obtaining optically active 4-aminobenzopyran derivatives. Dienophiles such as 2,3-dihydro-2H-furan, benzyl N-vinylcarbamate and 2-vinylindole have been employed.

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Catalytic Asymmetric Inverse‐Electron‐Demand (IED) [4+2] Cycloaddition of Salicylaldimines: Preparation of Optically Active 4‐Aminobenzopyran Derivatives

Bernardi

Franchini

Fochi

et al. 2010

Adv Synth Catal

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Conformational Changes and Competitive Adsorption between Serum Albumin and Hemoglobin on Bioceramic Substrates

et al. 2017

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Traditional methods to analyze interactions and conformational changes of proteins adsorbed onto biomaterials are limited by the protein's associations with the substrate material and the complexity of the surrounding media. We have used EPR spectroscopy in combination with site-directed spin labeling (SDSL) to investigate single protein and competitive adsorption kinetics of horse hemoglobin (Hgb) and bovine serum albumin (BSA) on a silica-calcium-phosphate bioceramic substrate. Combined continuous wave and pulsed (DEER) EPR techniques were employed to monitor local mobility/flexibility changes within the proteins and tertiary structure dynamics upon adsorption. An alternate labeling technique was introduced to allow for specific quantification of each protein adsorbed to the bioceramic surface. We show that at buffer pH 7.4 and 4.7 the amount of adsorbed hemoglobin was increased by a factor of 4-5 compared with BSA. The tertiary structure of hemoglobin was strongly affected upon adsorption, leading to a dissociation of the tetrameric molecule into monomers or αβ dimers. When the bioceramic substrate was previously functionalized with a layer of BSA, dissociation was reduced by 71 % compared with the untreated surface, indicating a "primer" effect of BSA for better adhesion of the globular hemoglobin.

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Inverse Solvent Effects in Carbocation Carbanion Combination Reactions: The Unique Behavior of Trifluoromethylsulfonyl Stabilized Carbanions

2007

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Second-order rate constants for the reactions of the trifluoromethylsulfonyl substituted benzyl anions 1a-e (CF3SO2CH(-)-C6H4-X) with the benzhydrylium ions 2f-j and structurally related quinone methides 2a-e have been determined by UV-vis spectroscopy. The reactions proceed approximately 10-40 times faster in methanol than in DMSO leading to the unique situation that these carbocation carbanion combinations are faster in protic than in dipolar aprotic media. The pK(a) values of some benzyl trifluoromethylsulfones were determined in methanol (1c-H, 17.1; 1d-H, 16.0; 1e-H, 15.0) and found to be 5 units larger than the corresponding values in DMSO. Rate and equilibrium measurements thus agree that the trifluoromethylsulfonyl substituted benzyl anions 1a-e are more effectively solvated by ion-dipole interactions in DMSO than by hydrogen bonding in methanol. Brønsted correlations show that in DMSO the trifluoromethylsulfonyl substituted carbanions 1 are less nucleophilic than most other types of carbanions of similar basicity, indicating that in DMSO the intrinsic barriers for the reactions of the localized carbanions 1 are higher than those of delocalized carbanions, including nitroalkyl anions. The situation is reversed in methanol, where the reactions of the localized carbanions 1 possess lower intrinsic barriers than those of delocalized carbanions as commonly found for proton-transfer processes. As a consequence, the relative magnitudes of intrinsic barriers are strongly dependent on the solvent.

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Partielle Entfaltung von T4‐Lysozym auf einer Quarzoberfläche: Analyse der Strukturänderungen adsorbierter Proteine durch ESR‐Spektroskopie

Cited by 4 publications

References 45 publications

Catalytic Asymmetric Inverse‐Electron‐Demand (IED) [4+2] Cycloaddition of Salicylaldimines: Preparation of Optically Active 4‐Aminobenzopyran Derivatives

Catalytic Asymmetric Inverse‐Electron‐Demand (IED) [4+2] Cycloaddition of Salicylaldimines: Preparation of Optically Active 4‐Aminobenzopyran Derivatives

Conformational Changes and Competitive Adsorption between Serum Albumin and Hemoglobin on Bioceramic Substrates

Inverse Solvent Effects in Carbocation Carbanion Combination Reactions: The Unique Behavior of Trifluoromethylsulfonyl Stabilized Carbanions

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