Basis set superposition error (BSSE) is a significant contributor to errors in quantum-based energy functions, especially for large chemical systems with many molecular contacts such as folded proteins and protein-ligand complexes. While the counterpoise method has become a standard procedure for correcting intermolecular BSSE, most current approaches to correcting intramolecular BSSE are simply fragment-based analogues of the counterpoise method which require many (two times the number of fragments) additional quantum calculations in their application. We propose that magnitudes of both forms of BSSE can be quickly estimated by dividing a system into interacting fragments, estimating each fragment's contribution to the overall BSSE with a simple statistical model, and then propagating these errors throughout the entire system. Such a method requires no additional quantum calculations, but rather only an analysis of the system's interacting fragments. The method is described herein and is applied to a protein-ligand system, a small helical protein, and a set of native and decoy protein folds. 相似文献
Abstract The reaction of the primary silylphosphanes and -arsanes 1 with [LiAlH4] leads. under evolution of H2 and depending on the solvent, to the different unusual clusters 2 and 3. Compound 2 has a rhombododecahedral skeleton. Surprisingly, the same reaction of the starting materials in DME instead of Et2O as solvent hrnishes the triple ion pair 3. 相似文献
Cell viability studies of HT29 colon cancer cells treated with the CO-releasing compound [Mn(CO)(3)(tpm)]PF(6) revealed a significant photoinduced cytotoxicity comparable to that of established agent 5-fluorouracil (5-FU), while controls kept in the dark were unaffected at up to 100 microM. 相似文献
Two novel peroxo titanium complexes, Li(2)(NH(4))(4)[Ti(2)(O(2))(2)(cit)(Hcit)](2).5H(2)O and Zn(NH(4))(4)[Ti(4)(O(2))(4)(Hcit)(2)(cit)(2)].12H(2)O (cit = citrate), show encouraging results in the photochemical oxidation of 2-propanol. 相似文献
Herein we briefly review theoretical contributions that have increased our understanding of the structure and function of metallo-beta-lactamases and ureases. Both are bimetallic metalloenzymes, with the former containing two zinc ions and the latter containing two nickel ions. We describe the use of several different methodologies, including quantum chemical calculations, molecular dynamic simulations, as well as mixed QM/MM approaches and how they have impacted our understanding of the structure and function of metallo-beta-lactamases and ureases. 相似文献
The title compounds are enantioselectively synthesized in just two preparative steps, making use of the Ugi-four-component reaction with an amino acid as chiral component, followed by a gold-catalyzed hydroamination. 相似文献
Like penguins on ice , buckybowl molecules move closer together when cooled on a copper surface (see model of a corannulene molecule adsorbed on Cu(111)). Upon heating, the molecules spread out into the original crystal phase again. The lower density at room temperature can be explained by the increase in entropy owing to the excitation of bowl vibrations at the surface.