RESUMO
Quantum mechanics/molecular mechanics (QM/MM) simulations offer an efficient way to model reactions occurring in complex environments. This study introduces a specialized set of charge and Lennard-Jones parameters tailored for electrostatically embedded QM/MM calculations, aiming to accurately model both adsorption processes and catalytic reactions in zirconium-based metal-organic frameworks (Zr-MOFs). To validate our approach, we compare adsorption energies derived from QM/MM simulations against experimental results and Monte Carlo simulation outcomes. The developed parameters showcase the ability of QM/MM simulations to represent long-range electrostatic and van der Waals interactions faithfully. This capability is evidenced by the prediction of adsorption energies with a low root mean square error of 1.1 kcal mol-1 across a wide range of adsorbates. The practical applicability of our QM/MM model is further illustrated through the study of glucose isomerization and epimerization reactions catalyzed by two structurally distinct Zr-MOF catalysts, UiO-66 and MOF-808. Our QM/MM calculations closely align with experimental activation energies. Importantly, the parameter set introduced here is compatible with the widely used universal force field (UFF). Moreover, we thoroughly explore how the size of the cluster model and the choice of density functional theory (DFT) methodologies influence the simulation outcomes. This work provides an accurate and computationally efficient framework for modeling complex catalytic reactions within Zr-MOFs, contributing valuable insights into their mechanistic behaviors and facilitating further advancements in this dynamic area of research.
RESUMO
A possible synergistic effect between penile venous surgery and oral sildenafil was inadvertently found in treating patients with erectile dysfunction in our clinic. We therefore sought to elucidate the possible synergic effect between venous surgery and sildenafil through studying patients who were non-responders preoperatively. From July 1998 to July 2003, 128 patients were diagnosed with veno-occlusive dysfunction. Subsequently, 65 of them underwent penile venous surgery and were assigned to the surgical treatment group. The remaining 63 men were assigned to the control group, and were subject to a simple re-exposure of oral sildenafil. All patients were evaluated with the international index of erectile function (IIEF-5) scoring. Sildenafil (12.5-100 mg) was prescribed postoperatively to all surgical patients as venous surgery alone was unsatisfactory and similarly, 100 mg preparation was prescribed for patients in the control group. The IIEF-5 scoring in the control group changed from a preoperative mean IIEF-5 score of 9.4 +/- 3.9 to 10.7 +/- 3.5 postoperatively. In surgical patients, however, the mean preoperative IIEF-5 score of 9.2 +/- 5.0, which increased to 15.1 +/- 5.0 (p < 0.001) postoperatively, further increased to 20.1 +/- 5.4 (p < 0.0001) after the addition of sildenafil. Although there was no significant difference between the two groups characteristics, there was a statistically significant difference between treatment results (p < 0.001). Overall, 61 men (93.8%) reported a positive response to sildenafil after venous stripping surgery. In contrast, only eight patients (12.7%) felt a beneficial response in the control group (p < 0.001). Forty-one of 65 patients had scores of > or =22, and 19 of these had a score of 25. No response was found in three (4.6%), and a decrease of 7 was seen in one (1.5%). In summary, patients in whom sildenafil was not effective preoperatively can become excellent responders after careful penile venous surgery. It appears that together, oral sildenafil and penile venous surgery may provide an encouraging solution to impotent patients with veno-occlusive dysfunction who are non-responders to sildenafil.
