We describe an unprecedented reaction between peptide selenoesters and peptide dimers bearing N-terminal selenocystine that proceeds in aqueous buffer to afford native amide bonds without the use of additives. The selenocystine-selenoester ligations are complete in minutes, even at sterically hindered junctions, and can be used in concert with one-pot deselenization chemistry. Various pathways for the transformation are proposed and probed through a combination of experimental and computational studies. Our new reaction manifold is also showcased in the total synthesis of two proteins.
Stable emission in glass Lead halide perovskites can exhibit bright, narrow band photoluminescence but have stability issues related to formation of inactive phases and the loss of lead ions. Hou et al . show that the black, photoactive phase of cesium lead iodide can be stabilized by forming a composite with a glassy phase of a metal-organic framework through liquid-phase sintering. The photoluminescence is at least two orders of magnitude greater than that of the pure perovskite. The glass stabilizes the perovskite under high laser excitation, and about 80% of the photoluminescence was maintained after 10,000 hours of water immersion. —PDS
We have formulated the W2X and W3X-L protocols as cost-effective alternatives to W2 and W3/W4, respectively, and to supplement our previously developed set of W1X and W3X procedures. The W2X procedure provides an accurate approximation to the all-electron scalar-relativistic CCSD(T)/CBS energy, with a mean absolute deviation (MAD) of 0.6 kJ mol(-1) from benchmark energies provided by the CCSD(T) component in the W4 protocol. Such a performance is comparable to that of W2w (0.5 kJ mol(-1)) but comes at a significantly lower cost. Comparison of computational requirements shows that W2X should be applicable to systems that can be treated by the W1w method. Thus, W2X provides an accurate means for the treatment of medium-sized systems such as naphthalene. For the calculation of post-CCSD(T) effects, we propose a slight modification to the method used in our previously devised W3X procedure. Our new W3-type protocol (W3X-L) combines this new post-CCSD(T) treatment with our new W2X procedure. It has an MAD from benchmark values of 0.8 kJ mol(-1) for the W4-11 set, which is comparable to that for the computationally more demanding W3.2 method (0.6 kJ mol(-1)). However, the use of the even relatively modest post-CCSD(T) calculations in W3X-L still represents a computational bottleneck, and this currently restricts its application to systems up to the size of benzene with our current computing resources.
G4(MP2)-6X is developed as a composite procedure with a cost comparable to that of G4(MP2) but performance approaching that of G4. The new procedure is a variant of G4(MP2) that employs BMK/6-31+G(2df,p) geometries and has six additional scaling factors for the correlation energy components. The scaling factors and HLC parameters are optimized using the new E2 set of 526 energies, representing thermochemical properties, reaction energies and barriers, and weak interactions. G4(MP2)-6X achieves a mean absolute deviation (MAD) from benchmark values of 3.64 kJ mol(-1) for the E2 set, compared with 4.42 kJ mol(-1) for G4(MP2). For the E0 set of 148 energies, G4(MP2)-6X gives an MAD of 3.43 kJ mol(-1), compared with 3.22 kJ mol(-1) for G4 and 4.03 kJ mol(-1) for G4(MP2). The new G4(MP2)-6X procedure thus uses extra parametrization to provide a G4-type performance without incurring G4-type computational costs.
The synthesis of four novel crystalline zeolitic imidazolate framework (ZIF) structures using a mixed-ligand approach is reported. The inclusion of both imidazolate and halogenated benzimidazolate-derived linkers leads to glass-forming behavior by all four structures. Melting temperatures are observed to depend on both electronic and steric effects. Solid-state NMR and terahertz (THz)/Far-IR demonstrate the presence of a Zn-F bond for fluorinated ZIF glasses. In situ THz/Far-IR spectroscopic techniques reveal the dynamic structural properties of crystal, glass and liquid phases of the halogenated ZIFs, linking the melting behavior of ZIFs to the propensity of the ZnN4 tetrahedra to undergo thermally-induced deformation. The inclusion of halogenated ligands within MOFglasses improves their gas uptake properties.
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.