The acidostat method previously developed for performing explicit-solvent molecular dynamics simulations at constant pH (J. Chem. Phys. 2001, 114, 9706) is applied to polyfunctional compounds, namely ...1,4-diaminobutane and a decalysine peptide. The titration behavior of 1,4-diaminobutane is investigated by performing a series of simulations at different pH, using the acidostat method. The method accounts at least to some extent for site−site coupling and reproduces the experimental pK a values of the compound within half a pK unit, although the simulations reveal insufficient sampling of the protonation-state variables. In a second step, the ability of the acidostat method to account for correlations between the solution pH and the structure and dynamics of a biomolecule is tested by studying the pH-dependent stability of an α-helical decalysine peptide. To this end, four 32-ns constant-pH simulations at different pH values are performed. The results are compared to those of standard molecular dynamics simulations of a fully protonated or a fully deprotonated peptide, and to experimental data on (comparatively longer) polylysine peptides. In agreement with experiment, the peptide predominantly remains in an α-helical conformation under high-pH conditions, but becomes disordered under low-pH conditions. The helix−coil transition pH for the peptide is found to be between 9.5 and 10.3, in good agreement with the experimental value for polylysine (10.3). The constant-pH simulations also evidence a correlation between the protonation of specific lysine side chains and the local loss of backbone hydrogen bonds and partial peptide unfolding, both effects occurring predominantly in the C-terminal region of the peptide.
A method is introduced for performing reagent selection for chemical library design based on topological (2D) pharmacophore fingerprints. Optimal reagent selection is achieved by optimizing the ...Shannon entropy of the 2D pharmacophore distribution for the reagent set. The method, termed ProSAR, is therefore expected to enumerate compounds that could serve as a good starting point for deriving a structure activity relationship (SAR) in combinatorial library design. This methodology is exemplified by library design examples where the active compounds were already known. The results show that most of the pharmacophores on the substituents for the active compounds are covered by the designed library. This strategy is further expanded to include product property profiles for aqueous solubility, hERG risk assessment etc. in the optimization process so that the reagent pharmacophore diversity and the product property profile are optimized simultaneously via a genetic algorithm. This strategy is applied to a two‐dimensional library design example and compared with libraries designed by a diversity based strategy which minimizes the average ensemble Tanimoto similarity. Our results show that by using the PSAR methodology, libraries can be designed with simultaneously good pharmacophore coverage and product property profile
Electronic distribution of laboratory test results to primary health care centres, via the EDIFACT standard, is presented. Results in the MEDRPT message format are transmitted with the message ...handling system X.400. A communication server with EDI software and X.400 message handling software is connected to a laboratory information system and via modem to primary health care centres. Results are, directly after approval automatically transferred to the physician's medical record system. This new service from the laboratory helps to get fast and reliable reports to the physician at a lower cost.
The WNT16 locus is a major determinant of cortical bone thickness and nonvertebral fracture risk in humans. The disability, mortality and costs caused by osteoporosis-induced nonvertebral fractures ...are enormous. We demonstrate here that Wnt16-deficient mice develop spontaneous fractures as a result of low cortical thickness and high cortical porosity. In contrast, trabecular bone volume is not altered in these mice. Mechanistic studies revealed that WNT16 is osteoblast derived and inhibits human and mouse osteoclastogenesis both directly by acting on osteoclast progenitors and indirectly by increasing expression of osteoprotegerin (Opg) in osteoblasts. The signaling pathway activated by WNT16 in osteoclast progenitors is noncanonical, whereas the pathway activated in osteoblasts is both canonical and noncanonical. Conditional Wnt16 inactivation revealed that osteoblast-lineage cells are the principal source of WNT16, and its targeted deletion in osteoblasts increases fracture susceptibility. Thus, osteoblast-derived WNT16 is a previously unreported key regulator of osteoclastogenesis and fracture susceptibility. These findings open new avenues for the specific prevention or treatment of nonvertebral fractures, a substantial unmet medical need.
Wingless-type MMTV integration site family (WNT)16 is a key regulator of bone mass with high expression in cortical bone, andWnt16−/−
mice have reduced cortical bone mass. AsWnt16expression is ...enhanced by estradiol treatment, we hypothesized that the bone-sparing effect of estrogen in females isWNT16-dependent. This hypothesis was tested in mechanistic studies using two genetically modified mouse models with either constantly high osteoblasticWnt16expression or noWnt16expression. We developed a mouse model with osteoblast-specificWnt16overexpression (Obl-Wnt16). These mice had several-fold elevatedWnt16expression in both trabecular and cortical bone compared with wild type (WT) mice.Obl-Wnt16mice displayed increased total body bone mineral density (BMD), surprisingly caused mainly by a substantial increase in trabecular bone mass, resulting in improved bone strength of vertebrae L₃. Ovariectomy (ovx) reduced the total body BMD and the trabecular bone mass to the same degree inObl-Wnt16mice and WT mice, suggesting that the bone-sparing effect of estrogen is WNT16-independent. However, these bone parameters were similar in ovxObl-Wnt16mice and sham operated WT mice. The role of WNT16 for the bone-sparing effect of estrogen was also evaluated inWnt16−/−
mice. Treatment with estradiol increased the trabecular and cortical bone mass to a similar extent in bothWnt16−/−
and WT mice. In conclusion, the bone-sparing effects of estrogen and WNT16 are independent of each other. Furthermore, loss of endogenous WNT16 results specifically in cortical bone loss, whereas overexpression of WNT16 surprisingly increases mainly trabecular bone mass. WNT16-targeted therapies might be useful for treatment of postmenopausal trabecular bone loss.
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