-
Meyers Chan posted an update 1 week, 2 days ago
During integration into materials, the inactivation of enzymes as a result of their interaction with nanometer size denaturing “hotspots” on surfaces represents a critical challenge. This challenge, which has received far less attention than improving the long-term stability of enzymes, may be overcome by limiting the exploration of surfaces by enzymes. One way this may be accomplished is through increasing the rate constant of the surface ligation reaction and thus the probability of immobilization with reactive surface sites (i.e., ligation efficiency). Here, the connection between ligation reaction efficiency and the retention of enzyme structure and activity was investigated by leveraging the extremely fast reaction of strained trans-cyclooctene (sTCOs) and tetrazines (Tet). Remarkably, upon immobilization via Tet-sTCO chemistry, carbonic anhydrase (CA) retained 77% of its solution-phase activity, while immobilization via less efficient reaction chemistries, such as thiol-maleimide and azide-dibenzocyclooctyne, led to activity retention of only 46% and 27%, respectively. Dynamic single-molecule fluorescence tracking methods further revealed that longer surface search distances prior to immobilization (>0.5 μm) dramatically increased the probability of CA unfolding. Notably, the CA distance to immobilization was significantly reduced through the use of Tet-sTCO chemistry, which correlated with the increased retention of structure and activity of immobilized CA compared to the use of slower ligation chemistries. These findings provide an unprecedented insight into the role of ligation reaction efficiency in mediating the exploration of denaturing hotspots on surfaces by enzymes, which, in turn, may have major ramifications in the creation of functional biohybrid materials.Sites isolation of active metals centers, systematically studied in homogeneous systems, has been an alternative to develop low metal consuming, highly active next generation catalysts in heterogeneous condition. Because of the high porosity and facile synthetic procedures, MOF-based catalysts are excellent candidates for heterogenization of well-defined homogeneous catalysts. Herein, we report the direct Pd coordination on the azobenzene linker within a MOF catalyst through a postsynthetic modification method for a Suzuki-Miyaura coupling reaction. The immobilized cyclopalladated complexes in MOFs were analyzed by a series of characterization techniques including XPS, PXRD, and deuterium NMR (2H NMR) spectroscopy. The heterogeneous nature of the catalyst as well as its stability were demonstrated though “hot filtration” and recycling experiments. Furthermore, we demonstrate that the MOF packed column promoted the reaction between phenyl boronic acid and bromobenzene under microflow conditions with a 85% yield continuously for 12 h. This work sheds light on the potential of site-isolated MOF catalysts in efficient, recyclable and continuous flow systems for industrial application.Interfaces govern thermal transport in a variety of nanostructured systems such as FinFETs, interconnects, and vias. Thermal boundary resistances, however, critically depend on the choice of materials, nanomanufacturing processes and conditions, and the planarity of interfaces. In this work, we study the interfacial thermal transport between a nonreactive metal (Pt) and a dielectric by engineering two differing bonding characters (i) the mechanical adhesion/van der Waals bonding offered by the physical vapor deposition (PVD) and (ii) the chemical bonding generated by plasma-enhanced atomic layer deposition (PEALD). We introduce 40-cycle (∼2 nm thick), nearly continuous PEALD Pt films between 98 nm PVD Pt and dielectric materials (8.0 nm TiO2/Si and 11.0 nm Al2O3/Si) treated with either O2 or O2 + H2 plasma to modulate their bonding strengths. By correlating the treatments through thermal transport measurements using time-domain thermoreflectance (TDTR), we find that the thermal boundary resistances are consistently reduced with the same increased treatment complexity that has been demonstrated in the literature to enhance mechanical adhesion. For samples on TiO2 (Al2O3), reductions in thermal resistance are at least 4% (10%) compared to those with no PEALD Pt at all, but could be as large as 34% (42%) given measurement uncertainties that could be improved with thinner nucleation layers. We suspect the O2 plasma generates stronger covalent bonds to the substrate, while the H2 plasma strips the PEALD Pt of contaminants such as carbon that gives rise to a less thermally resistive heat conduction pathway.Chemicals may cause adverse effects on human health through binding to peroxisome proliferator-activated receptor γ (PPARγ). Hence, binding affinity is useful for evaluating chemicals with potential endocrine-disrupting effects. Quantitative structure-activity relationship (QSAR) regression models with defined applicability domains (ADs) are important to enable efficient screening of chemicals with PPARγ binding activity. However, lack of large data sets hindered the development of QSAR models. In this study, based on PPARγ binding affinity data sets curated from various sources, 30 QSAR models were developed using molecular fingerprints, two-dimensional descriptors, and five machine learning algorithms. Structure-activity landscapes (SALs) of the training compounds were described by network-like similarity graphs (NSGs). Based on the NSGs, local discontinuity scores were calculated and found to be positively correlated with the cross-validation absolute prediction errors of the models using the different training sets, descriptors, and algorithms. Moreover, innovative ADs were defined based on pairwise similarities between compounds and were found to outperform some conventional ADs. learn more The curated data sets and developed regression models could be useful for evaluating PPARγ-involved adverse effects of chemicals. The SAL analysis and the innovative ADs could facilitate understanding of prediction results from QSAR models.With the rapid improvement of perovskite solar cells (PSCs), long-life operational stability has become a major requirement for their commercialization. In this work, we devised a pristine cesium-formamidinium-methylammonium (termed as CsFAMA) triple-cation-based perovskite precursor solution into the ionic liquid (IL)-assisted MAPbI3 nanoparticles (NPs) through a seeded growth approach in which the host IL-assisted MAPbI3 NPs remarkably promote high-quality perovskite films with large single-crystal domains, enhancing the device performance and stability. The power conversion efficiency (PCE) of the MAPbI3 NP-seeded growth of MAPbI3 NPs/CsFAMA-based PSCs is as high as 19.44%, which is superior to those of MAPbI3 NPs and pristine CsFAMA films as the photoactive layer (9.52 and 17.33%, respectively). The long-term light-soaking and moisture stability of IL-aided MAPbI3 NPs/CsFAMA-based devices (non-encapsulated) remain above 90 and 80%, respectively, of their initial output after 2 h of light illumination (1 sun) and 6000 h storage at ambient with a relative humidity range of 30-40%.