RESUMO
The lack of dispersion in the B3LYP functional has been proposed to be the main origin of big errors in quantum chemical modeling of a few enzymes and transition metal complexes. In this work, the essential dispersion effects that affect quantum chemical modeling are investigated. With binuclear zinc isoaspartyl dipeptidase (IAD) as an example, dispersion is included in the modeling of enzymatic reactions by two different procedures, i.e., (i) geometry optimizations followed by single-point calculations of dispersion (approach I) and (ii) the inclusion of dispersion throughout geometry optimization and energy evaluation (approach II). Based on a 169-atom chemical model, the calculations show a qualitative consistency between approaches I and II in energetics and most key geometries, demonstrating that both approaches are available with the latter preferential since both geometry and energy are dispersion-corrected in approach II. When a smaller model without Arg233 (147 atoms) was used, an inconsistency was observed, indicating that the missing dispersion interactions are essentially responsible for determining equilibrium geometries. Other technical issues and mechanistic characteristics of IAD are also discussed, in particular with respect to the effects of Arg233.
RESUMO
BACKGROUND AND OBJECTIVE: Bone marrow mesenchymal stem cells (MSCs) are of particular interest due their potential clinical use in tissue engineering. MSCs could secret soluble factor(s) upon stimulation. This study was to evaluate the influence of human bone marrow MSCs on proliferation of chronic myeloid leukemia cells, and assess the secretion of cytokines in the supernatant induced by MSCs. METHODS: Bone marrow MSCs extracted from healthy donors were cultured in DMEM-LG. The surface markers on the third passage MSCs were detected by flow cytometry. MSCs were co-cultured with chronic myeloid leukemia mononuclear cells (CML-MNCs) at various ratios. Cell proliferation was measured by flow cytometry. The interferon (IFN)-alpha level in the supernatant was analyzed by ELISA assay. RESULTS: The primary and passaged MSCs mostly appeared fibroblast-like and showed strong capacity of growth and reproduction. The membrane marker CD44 was positive and CD45 was negative on the surface of MSCs. Co-culture of MSCs with CML-MNC significantly inhibited the proliferation of CML-MNC. The IFN-alpha level in the supernatant of cell culture was significantly higher in the co-culture groups than in the CML-MNC control group (p < 0.001). Secretion of IFN-alpha was elevated with the increase of the MSC concentration and co-culture duration. CONCLUSION: Co-culture of MSCs with CML could secrete a substantial amount of IFN-alpha, thus to inhibit the proliferation of CML cells.