The self-assembly behavior of a diphenylalanine amphiphile blocked at the Cterminus with a 9-fluorenylmethyl ester and stabilized at the N-terminus with a trifluoroacetate (TFA) anion, TFA•FF-OFm, has been examined. At low peptide concentration (0.5 mg/mL), long amyloid-like fibrils, which come from the fusion of two or more helical ribbons and/or thinner fibrils, organized in bundles or as individual entities are detected. Microbeam synchrotron radiation infrared spectroscopy have shown that TFA•FF-OFm molecules in amyloid-like fibrils arrange forming antiparallel -sheets. Alteration of the experimental conditions to prioritize the thermodynamic contribution with respect to the kinetic one in the self-assembly process inhibits the organization of amyloid-like structures in favor of the formation of conventional fibrous structures. On the basis of experimental observations, a structural model where the individual antiparallel -sheets are oriented in parallel has been proposed for TFA•FF-OFm amyloid-like fibrils.
The thermomechanical response of Omp2a, a representative porin used for the fabrication of smart biomimetic nanomembranes, has been characterized using microcantilever technology and compared with standard proteins. For this purpose, thermally induced transitions involving the conversion of stable trimers to bigger aggregates, local reorganizations based on the strengthening or weakening of intermolecular interactions, and protein denaturation have been detected by the microcantilever resonance frequency and deflection as a function of the temperature. Measurements have been carried out on arrays of 8-microcantilevers functionalized with proteins (Omp2a, lysozyme and bovine serum albumin). To interpret the measured nanofeatures, the response of proteins to temperature has been also examined using other characterization techniques, including real time wide angle X-ray diffraction. Results not only demonstrate the complex behavior of porins, which exhibit multiple local thermal transitions before undergoing denaturation at temperatures higher than 105 °C, but also suggest a posttreatment to control the orientation of immobilized Omp2a molecules in functionalized biomimetic nanomembranes and, thus, increase their efficacy in ion transport.
The use of broadly neutralizing antibodies against human immunodeficiency virus type 1 (HIV-1) has been shown to be a promising therapeutic modality in the prevention of HIV infection. Understanding the b12–gp120 binding mechanism under physiological conditions may assist the development of more broadly effective antibodies. In this work, the main conformations and interactions between the receptor-binding domain (RBD) of spike glycoprotein gp120 of HIV-1 and the IgG1-b12 mAb are studied. Accelerated molecular dynamics (aMD) and ab initio hybrid molecular dynamics have been combined to determine the most persistent interactions between the most populated conformations of the antibody–antigen complex under physiological conditions. The results show the most persistent receptor-binding mapping in the conformations of the antibody–antigen interface in solution. The binding-free-energy decomposition reveals a small enhancement in the contribution played by the CDR-H3 region to the b12–gp120 interface compared to the crystal structure.
A key factor for improving the sensitivity and performance of immunosensors based on mechanical-plasmonic methods is the orientation of the antibody proteins immobilized on the inorganic surface. Although experimental techniques fail to determine surface phenomena at the molecular level, modern simulations open the possibility of improving our understanding of protein-surface interactions. In this work, Replica Exchange Molecular Dynamics (REMD) simulations have been used to model the IgG1 protein tethered on amorphous silica surface considering a united-atom model and a relatively large system (2500 nm 2 surface). Additional Molecular Dynamics (MD) simulations have been conducted to derive an atomistic model for the amorphous silica surface using the cristobalite crystal structure as starting point and to examine the structure of the free IgG1 antibody in solution for comparison when immobilized. Analyses of the trajectories obtained for the tethered IgG1, which was sampled considering 32 different temperatures, have been used to define the geometry of the protein with respect to the inorganic surface. The tilt angle of the protein with respect to the surface plane increases with the temperature, the most populated value being 24º, and 66º and 87º at the lowest (250 K), room (298 K) and highest (380 K) temperature. This variation indicates that the importance of proteinsurface interactions decreases with increasing temperature. The influence of the surface on the structure of the antibody is very significant in the constant region, which is directly involved in the tethering process, while it is relatively unimportant for the antigen-binding fragments, which are farthest from the surface. These results are expected to contribute to the development of improved mechanical-plasmonic sensor microarrays in the near future.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.