Dehydroalanine (Dha) residues are attractive noncanonical amino acids that occur naturally in ribosomally synthesised and post-translationally modified peptides (RiPPs). Dha residues are attractive targets for selective late-stage modification of these complex biomolecules. In this work, we show the selective photocatalytic modification of dehydroalanine residues in the antimicrobial peptide nisin and in the proteins small ubiquitin-like modifier (SUMO) and superfolder green fluorescent protein (sfGFP). For this purpose, a new water-soluble iridium(III) photoredox catalyst was used. The design and synthesis of this new photocatalyst, [Ir(dF(CF3)ppy)2(dNMe3bpy)]Cl3, is presented. In contrast to commonly used iridium photocatalysts, this complex is highly water soluble and allows peptides and proteins to be modified in water and aqueous solvents under physiologically relevant conditions, with short reaction times and with low reagent and catalyst loadings. This work suggests that photoredox catalysis using this newly designed catalyst is a promising strategy to modify dehydroalanine-containing natural products and thus could have great potential for novel bioconjugation strategies. 相似文献
We consider the Vlasov‐Poisson system in a cosmological setting as studied in [18] and prove nonlinear stability of homogeneous
solutions against small, spatially periodic perturbations in the L∞‐norm of the spatial mass density. This result is connected with the question of how large scale structures such as galaxies
have evolved out of the homogeneous state of the early universe.
(Accepted June 28, 1996) 相似文献
This paper presents a methodology for multiscale coupling between the morphology and texture of a microstructure as has been characterised experimentally, and the results of mechanical strain field analysis. This methodology is based on a coupling between experimental characterisation of the microstructure, in situ and/or ex situ mechanical tests, local strain field measurements performed at the grain scale, and finite element simulations. First, with orientation imaging microscopy, a map of the microstructure is generated that can be meshed. Then, finite element calculations are carried out on this mesh, using a constitutive law which takes into account the crystallographic orientation of each grain, as has been determined by the orientation imaging itself. These numerical results are then compared to the experimental strain field as obtained by digital image correlation at the scale of the grains. 相似文献
Abstract By means of high pressure differential thermal analysis we measured the pressure/temperature phase diagrams of several nematic compounds with different molecular structures. Using pressures up to about 500 M Pa we found strongly nonlinear clearing curves. This behaviour is interpreted as changes from ‘weak’ intermolecular potentials to ‘hard’ potentials, or using thermodynarmic arguments, strong pressure dependence of the volume discontinuity at the clearing transitions. 相似文献
In order to deliver reliable results for a multitude of different scenarios, e.g. emergency preparedness, environmental monitoring, nuclear decommissioning and waste management, there is a constant process of method development in the field of radioanalytical chemistry. This work presents the results of a method comparison exercise aimed at quantifying 90Sr and 239,240Pu in environmental soil samples, with the intention of evaluating the performance and applicability of different methods. From the methods examined in this work, recommendations are given in order to find a radioanalytical measurement procedure, for 90Sr and 239,240Pu analysis, which is fit-for-purpose for a particular scenario.