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1.
Phys Chem Chem Phys ; 25(46): 31683-31691, 2023 Nov 29.
Artículo en Inglés | MEDLINE | ID: mdl-37987036

RESUMEN

Accurately predicting partition coefficients log P is crucial for reducing costs and accelerating drug design as it provides valuable information about the bioavailability, pharmacokinetics, and toxicity of different drug candidates. However, the performance of the existing methods is ambiguous, making it unclear whether these methods can be effectively utilized in drug discovery. To assess the performance of these methods, a series of SAMPL challenges have been conducted over the past few years, aiming to enable the development and validation of predictive models. In this study, we present two independent contributions to the SAMPL9 challenge for predicting the toluene/water partition coefficients for 16 molecules. Both submissions, A and B, use the COSMO-RS approach, albeit in slightly different procedures, to compute the transfer free energies from water to toluene of the molecules presented in the challenge, and consequently, their corresponding log P values. Based on the results, COSMO-RS submission A achieves the top position with an R2 value of 0.93 while it ranks second in terms of root-mean-square error (RMSE) with a value of 1.23 log P units. COSMO-RS submission B achieves an R2 value of 0.83 and an RMSE value of 1.48 log P units. Following the challenge, we predict the log P values using a neural network model, which was pre-trained on COSMO-RS data achieving an R2 of 0.92 and RMSE of 1.04 log P units. Compared to previous SAMPL challenges, all contributions displayed large deviations in predicting the toluene/water partition coefficient. These large deviations emphasize that further research is needed to develop accurate and reliable methods for modeling solvent effects on small molecule transfer-free energies.

2.
J Comput Aided Mol Des ; 37(8): 395-405, 2023 08.
Artículo en Inglés | MEDLINE | ID: mdl-37365370

RESUMEN

The SAMPL8 blind prediction challenge, which addresses the acid/base dissociation constants (pKa) and the distribution coefficients (logD), was addressed by the Conductor like Screening Model for Realistic Solvation (COSMO-RS). Using the COSMOtherm implementation of COSMO-RS together with a rigorous conformational sampling, yielded logD predictions with a root mean square deviation (RMSD) of 1.36 log units over all 11 compounds and seven bi-phasic systems of the data set, which was the most accurate of all contest submissions (logD).For the SAMPL8 pKa competition, participants were asked to report the standard state free energies of all microstates, which were then used to calculate the macroscopic pKa. We have used COSMO-RS based linear free energy fit models to calculate the requested energies. The assignment of the calculated and experimental pKa values was made on the basis of the popular transitions, i.e. the transition hat was predicted by the majority of the submissions. With this assignment and a model that covers both, pKa and base pKa, we achieved an RMSD of 3.44 log units (18 pKa values of 14 molecules), which is the second place of the six ranked submissions. By changing to an assignment that is based on the experimental transition curves, the RMSD reduces to 1.65. In addition to the ranked contribution, we submitted two more data sets, one for the standard pKa model and one or the standard base pKa model of COSMOtherm. Using the experiment based assignment with the predictions of the two sets we received a RMSD of 1.42 log units (25 pKa values of 20 molecules). The deviation mainly arises from a single outlier compound, the omission of which leads to an RMSD of 0.89 log units.


Asunto(s)
Agua , Humanos , Termodinámica , Conformación Molecular
3.
J Clin Invest ; 133(10)2023 05 15.
Artículo en Inglés | MEDLINE | ID: mdl-36995772

RESUMEN

Despite advances in acute care, ischemic stroke remains a major cause of long-term disability. Approaches targeting both neuronal and glial responses are needed to enhance recovery and improve long-term outcome. The complement C3a receptor (C3aR) is a regulator of inflammation with roles in neurodevelopment, neural plasticity, and neurodegeneration. Using mice lacking C3aR (C3aR-/-) and mice overexpressing C3a in the brain, we uncovered 2 opposing effects of C3aR signaling on functional recovery after ischemic stroke: inhibition in the acute phase and facilitation in the later phase. Peri-infarct astrocyte reactivity was increased and density of microglia reduced in C3aR-/- mice; C3a overexpression led to the opposite effects. Pharmacological treatment of wild-type mice with intranasal C3a starting 7 days after stroke accelerated recovery of motor function and attenuated astrocyte reactivity without enhancing microgliosis. C3a treatment stimulated global white matter reorganization, increased peri-infarct structural connectivity, and upregulated Igf1 and Thbs4 in the peri-infarct cortex. Thus, C3a treatment from day 7 after stroke exerts positive effects on astrocytes and neuronal connectivity while avoiding the deleterious consequences of C3aR signaling during the acute phase. Intranasal administration of C3aR agonists within a convenient time window holds translational promise to improve outcome after ischemic stroke.


Asunto(s)
Accidente Cerebrovascular Isquémico , Accidente Cerebrovascular , Ratones , Animales , Complemento C3a/genética , Astrocitos , Accidente Cerebrovascular/tratamiento farmacológico , Accidente Cerebrovascular/genética , Infarto
4.
iScience ; 24(10): 103095, 2021 Oct 22.
Artículo en Inglés | MEDLINE | ID: mdl-34622150

RESUMEN

The gut microbiome has been implicated as a key regulator of brain function in health and disease. But the impact of gut microbiota on functional brain connectivity is unknown. We used resting-state functional magnetic resonance imaging in germ-free and normally colonized mice under naive conditions and after ischemic stroke. We observed a strong, brain-wide increase of functional connectivity in germ-free animals. Graph theoretical analysis revealed significant higher values in germ-free animals, indicating a stronger and denser global network but with less structural organization. Breakdown of network function after stroke equally affected germ-free and colonized mice. Results from histological analyses showed changes in dendritic spine densities, as well as an immature microglial phenotype, indicating impaired microglia-neuron interaction in germ-free mice as potential cause of this phenomenon. These results demonstrate the substantial impact of bacterial colonization on brain-wide function and extend our so far mainly (sub) cellular understanding of the gut-brain axis.

5.
J Chem Phys ; 152(18): 184107, 2020 May 14.
Artículo en Inglés | MEDLINE | ID: mdl-32414256

RESUMEN

TURBOMOLE is a collaborative, multi-national software development project aiming to provide highly efficient and stable computational tools for quantum chemical simulations of molecules, clusters, periodic systems, and solutions. The TURBOMOLE software suite is optimized for widely available, inexpensive, and resource-efficient hardware such as multi-core workstations and small computer clusters. TURBOMOLE specializes in electronic structure methods with outstanding accuracy-cost ratio, such as density functional theory including local hybrids and the random phase approximation (RPA), GW-Bethe-Salpeter methods, second-order Møller-Plesset theory, and explicitly correlated coupled-cluster methods. TURBOMOLE is based on Gaussian basis sets and has been pivotal for the development of many fast and low-scaling algorithms in the past three decades, such as integral-direct methods, fast multipole methods, the resolution-of-the-identity approximation, imaginary frequency integration, Laplace transform, and pair natural orbital methods. This review focuses on recent additions to TURBOMOLE's functionality, including excited-state methods, RPA and Green's function methods, relativistic approaches, high-order molecular properties, solvation effects, and periodic systems. A variety of illustrative applications along with accuracy and timing data are discussed. Moreover, available interfaces to users as well as other software are summarized. TURBOMOLE's current licensing, distribution, and support model are discussed, and an overview of TURBOMOLE's development workflow is provided. Challenges such as communication and outreach, software infrastructure, and funding are highlighted.

6.
Front Cell Neurosci ; 14: 86, 2020.
Artículo en Inglés | MEDLINE | ID: mdl-32317940

RESUMEN

Most stroke studies dealing with functional deficits and assessing stem cell therapy produce extensive hemispheric damage and can be seen as a model for severe clinical strokes. However, mild strokes have a better prospect for functional recovery. Recently, anatomic and behavioral changes have been reported for distal occlusion of the middle cerebral artery (MCA), generating a well-circumscribed and small cortical lesion, which can thus be proposed as mild to moderate cortical stroke. Using this cortical stroke model of moderate severity in the nude mouse, we have studied the functional networks with resting-state functional magnetic resonance imaging (fMRI) for 12 weeks following stroke induction. Further, human neural stem cells (hNSCs) were implanted adjacent to the ischemic lesion, and the stable graft vitality was monitored with bioluminescence imaging (BLI). Differentiation of the grafted neural stem cells was analyzed by immunohistochemistry and by patch-clamp electrophysiology. Following stroke induction, we found a pronounced and continuously rising hypersynchronicity of the sensorimotor networks including both hemispheres, in contrast to the severe stroke filament model where profound reduction of the functional connectivity had been reported by us earlier. The vitality of grafted neural stem cells remained stable throughout the whole 12 weeks observation period. In the stem cell treated animals, functional connectivity did not show hypersynchronicity but was globally slightly reduced below baseline at 2 weeks post-stroke, normalizing thereafter completely. Our resting-state fMRI (rsfMRI) studies on cortical stroke reveal for the first time a hypersynchronicity of the functional brain networks. This hypersynchronicity appears as a hallmark of mild cortical strokes, in contrast to severe strokes with striatal involvement where exclusively hyposynchronicity has been reported. The effect of the stem cell graft was an early and persistent normalization of the functional sensorimotor networks across the whole brain. These novel functional results may help interpret future outcome investigations after stroke and demonstrate the highly promising potential of stem cell treatment for functional outcome improvement after stroke.

7.
J Chem Inf Model ; 59(11): 4806-4813, 2019 11 25.
Artículo en Inglés | MEDLINE | ID: mdl-31692342

RESUMEN

The COSMO-RS method is an established method for the prediction of fluid phase properties such as activity coefficients, liquid-liquid equilibria, and free energy of solvation. It is also frequently used in quantum chemistry-based chemical reaction modeling to predict the solvation contribution to the reactions. The COSMOtherm software, which features the currently most advanced implementation of COSMO-RS, is based on quantum chemical COSMO calculations using the BP functional with the def2-TZVPD basis set. As the accuracy of COSMO-RS depends on the accuracy of the underlying quantum chemical (QC) calculation, it is important to validate the currently used level against other common, presumably superior, approaches such as the more recently developed M06-2x hybrid density functional or wave function methods such as MP2. As compared to other applications where the electronic energy is the most important result of the QC calculation, the COSMO-RS method has a much higher dependence on the molecular polarity and thus the electron density distribution. We find that MP2, PBE0, and M06-2x perform slightly worse in fully reparametrized COSMO-RS with respect to the prediction of experimentally measured properties like pKa or logP. Although MP2 was reported to yield better polarities than most DFT functionals for spin unpolarized molecules, this theoretical advantage does not manifest in a practical benefit for the prediction of thermodynamic properties with a refitted COSMO-RS parameter set. Other pure DFT functionals such as PBE or TPSS can be used instead of BP, but again, no practical advantage is expected as they yield extremely similar polarities to the original BP calculations.


Asunto(s)
Hexanos/química , Teoría Cuántica , Bibliotecas de Moléculas Pequeñas/química , Agua/química , Electrones , Modelos Químicos , Modelos Moleculares , Solubilidad , Solventes/química , Termodinámica
8.
Front Aging Neurosci ; 11: 277, 2019.
Artículo en Inglés | MEDLINE | ID: mdl-31680932

RESUMEN

Resting-state functional magnetic resonance imaging (rsfMRI) is increasingly used to unravel the functional neuronal networks in health and disease. In particular, this technique of simultaneously probing the whole brain has found high interest in monitoring brain wide effects of cerebral disease and in evaluating therapeutic strategies. Such studies, applied in preclinical experimental mouse models, often require long-term observations. In particular during regeneration studies, easily several months of continuous monitoring are required to detect functional improvements. These long periods of following the functional deficits during disease evolution as well as the functional recoveries during therapeutic interventions represent a substantial fraction of the life span of the experimental animals. We have therefore aimed to decipher the role of healthy aging alone for changes in functional neuronal networks in mice, from developmental adolescence via adulthood to progressing aging. For this purpose, four different groups of C57Bl6 mice of varying age between 2 and 13 months were studied twice with 4 weeks separation using resting state fMRI at 9.4T. Dedicated data analysis including both Independent Component Analysis (ICA) followed by seed-based connectivity matrix compilation resulted in an inverse U-shape curve of functional connectivity (FC) strength in both the sensorimotor and default mode network (DMN). This inverse U-shape pattern presented a distinct maximum of FC strength at 8-9 months of age, followed by a continuous decrease during later aging phases. At progressed aging at 12-13 months, the reduction of connectivity strength varied between 25% and 70% with most connectivities showing a reduction in strength by approximately 50%. We recommend that these substantial age-dependent changes in FC strength must be considered in future longitudinal studies to discriminate focused disease-based functional deficits and therapy-related functional improvements from underlying independent age effects.

9.
Front Neuroinform ; 13: 42, 2019.
Artículo en Inglés | MEDLINE | ID: mdl-31231202

RESUMEN

Magnetic resonance imaging (MRI) is a key technology in multimodal animal studies of brain connectivity and disease pathology. In vivo MRI provides non-invasive, whole brain macroscopic images containing structural and functional information, thereby complementing invasive in vivo high-resolution microscopy and ex vivo molecular techniques. Brain mapping, the correlation of corresponding regions between multiple brains in a standard brain atlas system, is widely used in human MRI. For small animal MRI, however, there is no scientific consensus on pre-processing strategies and atlas-based neuroinformatics. Thus, it remains difficult to compare and validate results from different pre-clinical studies which were processed using custom-made code or individual adjustments of clinical MRI software and without a standard brain reference atlas. Here, we describe AIDAmri, a novel Atlas-based Imaging Data Analysis pipeline to process structural and functional mouse brain data including anatomical MRI, fiber tracking using diffusion tensor imaging (DTI) and functional connectivity analysis using resting-state functional MRI (rs-fMRI). The AIDAmri pipeline includes automated pre-processing steps, such as raw data conversion, skull-stripping and bias-field correction as well as image registration with the Allen Mouse Brain Reference Atlas (ARA). Following a modular structure developed in Python scripting language, the pipeline integrates established and newly developed algorithms. Each processing step was optimized for efficient data processing requiring minimal user-input and user programming skills. The raw data is analyzed and results transferred to the ARA coordinate system in order to allow an efficient and highly-accurate region-based analysis. AIDAmri is intended to fill the gap of a missing open-access and cross-platform toolbox for the most relevant mouse brain MRI sequences thereby facilitating data processing in large cohorts and multi-center studies.

10.
Sci Rep ; 9(1): 6823, 2019 05 02.
Artículo en Inglés | MEDLINE | ID: mdl-31048718

RESUMEN

The stroke model of distal middle cerebral artery occlusion is considered a reliable stroke model with high reproducibility and low mortality rate. Thus, it is preferred for assessments of therapeutic strategies, in particular for neurorepair and regeneration studies. However, present literature has reported only on the lesion behavior and behavioral deficits during the acute and subacute phase of maximally three weeks. We have here aimed to characterize the lesion expansion and consequent, potential tissue displacements using structural magnetic resonance imaging modalities, histology, and behavioral tests, during the chronic time window of 12 weeks following stroke induction. We found a severe cortical thinning resulting in 15% tissue loss of the ipsilateral cortex by 6 weeks. After two weeks, massive hippocampus displacement was found, into the cortical tissue void and, in this process, pushing the corpus callosum to the brain surface showing an almost radial direction towards the surface. These massive chronic morphological changes and rearrangements, not known from other stroke models, have relevant consequences for decision of stem cell graft placement for cerebral regeneration to assure persistent graft vitality during a longitudinal investigation in the chronic phase.


Asunto(s)
Isquemia Encefálica/patología , Corteza Cerebral/irrigación sanguínea , Corteza Cerebral/patología , Animales , Conducta Animal , Isquemia Encefálica/diagnóstico por imagen , Corteza Cerebral/diagnóstico por imagen , Modelos Animales de Enfermedad , Hipocampo/diagnóstico por imagen , Hipocampo/metabolismo , Hipocampo/patología , Inmunohistoquímica , Imagen por Resonancia Magnética , Ratones , Ratones Desnudos , Corteza Sensoriomotora/diagnóstico por imagen , Corteza Sensoriomotora/metabolismo , Corteza Sensoriomotora/patología
11.
Front Neurol ; 10: 335, 2019.
Artículo en Inglés | MEDLINE | ID: mdl-31024429

RESUMEN

Stem cell treatment after stroke has demonstrated substantial outcome improvement. However, monitoring of stem cell fate in vivo is still challenging and not routinely performed, yet important to quantify the role of the implanted stem cells on lesion improvement; in several studies even mortality of the graft has been reported. Resting state functional magnetic resonance imaging (rs-fMRI) is a highly sensitive imaging modality to monitor the brain-wide functional network alterations of many brain diseases in vivo. We monitor for 3 months the functional connectivity changes after intracortical stem cell engraftment in large, cortico-striatal (n = 9), and in small, striatal (n = 6) ischemic lesions in the mouse brain with non-invasive rs-fMRI on a 9.4T preclinical MRi scanner with GE-EPI sequence. Graft vitality is continuously recorded by bioluminescence imaging (BLI) roughly every 2 weeks after implantation of 300 k neural stem cells. In cortico-striatal lesions, the lesion extension induces graft vitality loss, in consequence leading to a parallel decrease of functional connectivity strength after a few weeks. In small, striatal lesions, the graft vitality is preserved for the whole observation period and the functional connectivity is stabilized at values as in the pre-stroke situation. But even here, at the end of the observation period of 3 months, the functional connectivity strength is found to decrease despite preserved graft vitality. We conclude that quantitative graft viability is a necessary but not sufficient criterion for functional neuronal network stabilization after stroke. Future studies with even longer time periods after stroke induction will need to identify additional players which have negative influence on the functional brain networks.

12.
J Comput Chem ; 39(21): 1648-1655, 2018 08 05.
Artículo en Inglés | MEDLINE | ID: mdl-29756357

RESUMEN

A cavity construction algorithm based on the triangulation of an iso-surface is introduced as a new standard for dielectric continuum solvation calculations with the Conductor-like Screening Model COSMO. It overcomes deficiencies which have become apparent for the original COSMO standard cavity, especially in concave regions of the molecular shaped cavity. The new standard, called FINE Cavity, is described in this article with several application examples. The earlier COSMO cavity construction algorithms are described for comparison. © 2018 Wiley Periodicals, Inc.

13.
J Neurosci ; 38(7): 1648-1661, 2018 02 14.
Artículo en Inglés | MEDLINE | ID: mdl-29321138

RESUMEN

Past investigations on stem cell-mediated recovery after stroke have limited their focus on the extent and morphological development of the ischemic lesion itself over time or on the integration capacity of the stem cell graft ex vivo However, an assessment of the long-term functional and structural improvement in vivo is essential to reliably quantify the regenerative capacity of cell implantation after stroke. We induced ischemic stroke in nude mice and implanted human neural stem cells (H9 derived) into the ipsilateral cortex in the acute phase. Functional and structural connectivity changes of the sensorimotor network were noninvasively monitored using magnetic resonance imaging for 3 months after stem cell implantation. A sharp decrease of the functional sensorimotor network extended even to the contralateral hemisphere, persisting for the whole 12 weeks of observation. In mice with stem cell implantation, functional networks were stabilized early on, pointing to a paracrine effect as an early supportive mechanism of the graft. This stabilization required the persistent vitality of the stem cells, monitored by bioluminescence imaging. Thus, we also observed deterioration of the early network stabilization upon vitality loss of the graft after a few weeks. Structural connectivity analysis showed fiber-density increases between the cortex and white matter regions occurring predominantly on the ischemic hemisphere. These fiber-density changes were nearly the same for both study groups. This motivated us to hypothesize that the stem cells can influence, via early paracrine effect, the functional networks, while observed structural changes are mainly stimulated by the ischemic event.SIGNIFICANCE STATEMENT In recent years, research on strokes has made a shift away from a focus on immediate ischemic effects and towards an emphasis on the long-range effects of the lesion on the whole brain. Outcome improvements in stem cell therapies also require the understanding of their influence on the whole-brain networks. Here, we have longitudinally and noninvasively monitored the structural and functional network alterations in the mouse model of focal cerebral ischemia. Structural changes of fiber-density increases are stimulated in the endogenous tissue without further modulation by the stem cells, while functional networks are stabilized by the stem cells via a paracrine effect. These results will help decipher the underlying networks of brain plasticity in response to cerebral lesions and offer clues to unravelling the mystery of how stem cells mediate regeneration.


Asunto(s)
Isquemia Encefálica/terapia , Encéfalo , Movimiento , Red Nerviosa/fisiopatología , Células-Madre Neurales/trasplante , Sensación , Trasplante de Células Madre/métodos , Animales , Isquemia Encefálica/fisiopatología , Isquemia Encefálica/psicología , Lateralidad Funcional , Infarto de la Arteria Cerebral Media/patología , Infarto de la Arteria Cerebral Media/fisiopatología , Infarto de la Arteria Cerebral Media/terapia , Imagen por Resonancia Magnética , Masculino , Ratones , Ratones Desnudos , Fibras Nerviosas , Recuperación de la Función , Accidente Cerebrovascular/terapia , Resultado del Tratamiento , Sustancia Blanca/fisiopatología
14.
Nat Commun ; 8: 14162, 2017 01 19.
Artículo en Inglés | MEDLINE | ID: mdl-28102196

RESUMEN

While transplantation represents a key tool for assessing in vivo functionality of neural stem cells and their suitability for neural repair, little is known about the integration of grafted neurons into the host brain circuitry. Rabies virus-based retrograde tracing has developed into a powerful approach for visualizing synaptically connected neurons. Here, we combine this technique with light sheet fluorescence microscopy (LSFM) to visualize transplanted cells and connected host neurons in whole-mouse brain preparations. Combined with co-registration of high-precision three-dimensional magnetic resonance imaging (3D MRI) reference data sets, this approach enables precise anatomical allocation of the host input neurons. Our data show that the same neural donor cell population grafted into different brain regions receives highly orthotopic input. These findings indicate that transplant connectivity is largely dictated by the circuitry of the target region and depict rabies-based transsynaptic tracing and LSFM as efficient tools for comprehensive assessment of host-donor cell innervation.


Asunto(s)
Mapeo Encefálico , Células-Madre Neurales/fisiología , Neuronas/trasplante , Animales , Encéfalo , Diferenciación Celular/fisiología , Vectores Genéticos , Humanos , Interneuronas , Imagen por Resonancia Magnética/métodos , Ratones , Microscopía Fluorescente/métodos , Neuronas/fisiología , Virus de la Rabia/fisiología
15.
Neurobiol Dis ; 99: 47-57, 2017 Mar.
Artículo en Inglés | MEDLINE | ID: mdl-28007584

RESUMEN

Stroke is a leading cause of death and disability worldwide with no treatment for the chronic phase available. Interestingly, an endogenous repair program comprising inflammation and neurogenesis is known to modulate stroke outcome. Several studies have shown that neurogenesis decreases with age but the therapeutic importance of endogenous neurogenesis for recovery from cerebral diseases has been indicated as its ablation leads to stroke aggravation and worsened outcome. A detailed characterization of the neurogenic response after stroke related to ageing would help to develop novel and targeted therapies. In an innovative approach, we used the DCX-Luc mouse, a transgenic model expressing luciferase in doublecortin-positive neuroblasts, to monitor the neurogenic response following middle cerebral artery occlusion over three weeks in three age groups (2, 6, 12months) by optical imaging while the stroke lesion was monitored by quantitative MRI. The individual longitudinal and noninvasive time profiles provided exclusive insight into age-dependent decrease in basal neurogenesis and neurogenic upregulation in response to stroke which are not accessible by conventional BrdU-based measures of cell proliferation. For cortico-striatal strokes the maximal upregulation occurred at 4days post stroke followed by a continuous decrease to basal levels by three weeks post stroke. Older animals effectively compensated for reduced basal neurogenesis by an enhanced sensitivity to the cerebral lesion, resulting in upregulated neurogenesis levels approaching those measured in young mice. In middle aged and older mice, but not in the youngest ones, additional upregulation of neurogenesis was observed in the contralateral healthy hemisphere. This further substantiates the increased propensity of older brains to respond to lesion situation. Our results clearly support the therapeutic relevance of endogenous neurogenesis for stroke recovery and particularly in older brains.


Asunto(s)
Envejecimiento/fisiología , Isquemia Encefálica/fisiopatología , Corteza Cerebral/fisiopatología , Cuerpo Estriado/fisiopatología , Neurogénesis/fisiología , Accidente Cerebrovascular/fisiopatología , Envejecimiento/patología , Animales , Isquemia Encefálica/diagnóstico por imagen , Isquemia Encefálica/patología , Corteza Cerebral/diagnóstico por imagen , Corteza Cerebral/patología , Cuerpo Estriado/diagnóstico por imagen , Cuerpo Estriado/patología , Modelos Animales de Enfermedad , Progresión de la Enfermedad , Proteína Doblecortina , Lateralidad Funcional , Inmunohistoquímica , Estudios Longitudinales , Imagen por Resonancia Magnética , Masculino , Ratones Endogámicos C57BL , Ratones Transgénicos , Imagen Óptica , Accidente Cerebrovascular/diagnóstico por imagen , Accidente Cerebrovascular/patología
16.
J Phys Chem A ; 119(21): 5439-45, 2015 May 28.
Artículo en Inglés | MEDLINE | ID: mdl-25635509

RESUMEN

The concept of dielectric continuum models has turned out to be very fruitful for the qualitative description of solvation effects in quantum chemical calculations, although from a theoretical perspective its basis is questionable, at least if applied to polar solvents, because the electrostatic nearest neighbor interactions in polar solvents are much too strong to be described by macroscopic dielectric continuum theory. On the basis of this insight, the Conductorlike Screening Model for Realistic Solvation (COSMO-RS) had been developed, which gives a thermodynamically consistent, quantitative description of solvation effects in polar and nonpolar solvents, even in mixtures and at variable temperature, starting from quantum chemical calculations of solute and solvent molecules embedded in a virtual conductor (COSMO). Though COSMO-RS usually only requires quantum chemical calculations in the conductor and thus does not allow for studying of the concrete solvent influence on the solute electron density, the direct COSMO-RS (DCOSMO-RS) has been introduced, which uses the σ-potential, i.e., a solvent specific response function provided by COSMO-RS, as a replacement of the conductor or dielectric response employed in continuum solvation models. In this article we describe the current status of DCOSMO-RS and demonstrate the performance of the DCOSMO-RS approach for the prediction of free energies of solvation.

17.
Neuroimage ; 84: 35-44, 2014 Jan 01.
Artículo en Inglés | MEDLINE | ID: mdl-23994458

RESUMEN

Longitudinal studies on brain pathology and assessment of therapeutic strategies rely on a fully mature adult brain to exclude confounds of cerebral developmental changes. Thus, knowledge about onset of adulthood is indispensable for discrimination of developmental phase and adulthood. We have performed a high-resolution longitudinal MRI study at 11.7T of male Wistar rats between 21days and six months of age, characterizing cerebral volume changes and tissue-specific myelination as a function of age. Cortical thickness reaches final value at 1month, while volume increases of cortex, striatum and whole brain end only after two months. Myelin accretion is pronounced until the end of the third postnatal month. After this time, continuing myelination increases in cortex are still seen on histological analysis but are no longer reliably detectable with diffusion-weighted MRI due to parallel tissue restructuring processes. In conclusion, cerebral development continues over the first three months of age. This is of relevance for future studies on brain disease models which should not start before the end of month 3 to exclude serious confounds of continuing tissue development.


Asunto(s)
Envejecimiento/patología , Corteza Cerebral/anatomía & histología , Cuerpo Estriado/anatomía & histología , Fibras Nerviosas Mielínicas/ultraestructura , Envejecimiento/fisiología , Animales , Corteza Cerebral/fisiología , Cuerpo Estriado/fisiología , Imagen de Difusión Tensora , Masculino , Fibras Nerviosas Mielínicas/fisiología , Tamaño de los Órganos , Ratas , Ratas Wistar
18.
J Comput Aided Mol Des ; 26(5): 669-73, 2012 May.
Artículo en Inglés | MEDLINE | ID: mdl-22581451

RESUMEN

The COSMO-RS method has been used for the prediction of free energies of hydration on the dataset of 36 chlorinated ethanes, biphenyls and dioxins considered in the SAMPL3 challenge. Straight application of the latest version of the COSMOtherm software yields an overall predictive accuracy of 1.05 kcal/mol (RMSE). The predictions for the chlorinated ethanes and dioxins are much better with 0.40 and 0.49 kcal/mol RMSE, respectively. The predictions for the chlorinated biphenyls show a systematic shift of approximately 1 kcal/mol, but the large RMSE of 1.59 kcal/mol mainly arises from two exceptional outliers. Possible reasons for this observation are discussed.


Asunto(s)
Hidrocarburos Clorados/química , Modelos Moleculares , Termodinámica , Simulación por Computador , Entropía , Ligandos , Teoría Cuántica , Programas Informáticos , Solventes/química , Agua/química
19.
J Comput Chem ; 33(8): 881-6, 2012 Mar 30.
Artículo en Inglés | MEDLINE | ID: mdl-22278903

RESUMEN

We present thermocalc, a Perl module to perform the automated calculation of atomization energies and heats of formation for lists of molecules. The methods used are based on density functional theory and second-order perturbation theory to ensure that data sets of medium sized to large molecules can be run at reasonable throughput rates. The quantum chemical calculations are performed using the program package TURBOMOLE in a three-step protocol. In a first step, a pre-optimization of the structure and a zero-point energy calculation are performed. As second step, a geometry optimization is being carried out, and the last step is a single point energy calculation. The level of theory used in the different steps can be modified by the user to allow for customized protocols. The performance of example protocols is investigated on different test sets of molecules. In the course of this work, a simple, but efficient one-parameter correction term based on the shared electron numbers has been developed, which reduces the error of calculated heats of formation significantly.

20.
J Chem Theory Comput ; 8(11): 4189-203, 2012 Nov 13.
Artículo en Inglés | MEDLINE | ID: mdl-26605584

RESUMEN

A recently proposed quantum-chemical protocol for the description of the character of organic mixed-valence (MV) compounds, close from both sides to the localized/delocalized borderline, is evaluated and extended for a series of dinitroaryl radical anions 1-6. A combination of global hybrid functionals with exact-exchange admixtures of 35% (BLYP35) or 42% (BMK) with appropriate solvent modeling allows an essentially quantitative treatment of, for example, structural symmetry-breaking in Robin/Day class II systems, thermal electron transfer (ET) barriers, and intervalence charge-transfer (IV-CT) excitation energies, while covering also the delocalized class III cases. Global hybrid functionals with lower exact-exchange admixtures (e.g., B3LYP, M05, or M06) provide a too delocalized description, while functionals with higher exact-exchange admixtures (M05-2X, M06-2X) provide a too localized one. The B2PLYP double hybrid gives reasonable structures but far too small barriers in class II cases. The CAM-B3LYP range hybrid gives somewhat too high ET barriers and IV-CT energies, while the range hybrids ωB97X and LC-BLYP clearly exhibit too much exact exchange. Continuum solvent models describe the situation well in most aprotic solvents studied. The transition of 1,4-dinitrobenzene anion 1 from a class III behavior in aprotic solvents to a class II behavior in alcohols is not recovered by continuum solvent models. In contrast, it is treated faithfully by the novel direct conductor-like screening model for real solvents (D-COSMO-RS). The D-COSMO-RS approach, the TURBOMOLE implementation of which is reported, also describes accurately the increased ET barriers of class II systems 2 and 3 in alcohols as compared to aprotic solvents and can distinguish at least qualitatively between different aprotic solvents with identical or similar dielectric constants. The dominant role of the solvent environment for the ET character of these MV radical anions is emphasized, as in contrast to some previous computational suggestions essentially all of the present systems have delocalized class III character in the gas phase. The present approach allows accurate estimates from the gas phase to aprotic and protic solvent environments, without the need for explicit ab initio molecular dynamics simulations, and without artificial constraints.

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