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1.
J Psychiatry Neurosci ; 45(2): 79-87, 2020 03 01.
Artigo em Inglês | MEDLINE | ID: mdl-32096617

RESUMO

Background: Multiple lines of evidence suggest that the onset and course of bipolar disorder is influenced by environmental light conditions. Increased suppression of melatonin by light (supersensitivity) in patients with bipolar disorder has been postulated as an endophenotype by several studies. However, due to methodological shortcomings, the results of these studies remain inconclusive. This study investigated melatonin suppression in euthymic patients with bipolar I disorder using evening blue light specifically targeting the melanopsin system. Methods: Melatonin suppression was assessed in euthymic patients with bipolar I disorder and healthy controls by exposure to monochromatic blue light (λmax = 475 nm; photon density = 1.6 × 1013 photons/cm2/s) for 30 minutes at 2300 h, administered via a ganzfeld dome for highly uniform light exposure. Serum melatonin concentrations were determined from serial blood sampling via radioimmunoassay. All participants received mydriatic eye drops and were genotyped for the PER3 VNTR polymorphism to avoid or adjust for potential confounding. As secondary outcomes, serum melatonin concentrations during dark conditions and after monochromatic red light exposure (λmax = 624 nm; photon density = 1.6 × 1013 photons/cm2/s) were also investigated. Changes in subjective alertness were investigated for all 3 lighting conditions. Results: A total of 90 participants (57 controls, 33 bipolar I disorder) completed the study. Melatonin suppression by monochromatic blue light did not differ between groups (F1,80 = 0.56; p = 0.46). Moreover, there were no differences in melatonin suppression by monochromatic red light (F1,82 = 1.80; p = 0.18) or differences in melatonin concentrations during dark conditions (F1,74 = 1.16; p = 0.29). Healthy controls displayed a stronger increase in subjective alertness during exposure to blue light than patients with bipolar I disorder (t85 = 2.28; p = 0.027). Limitations: Large interindividual differences in melatonin kinetics may have masked a true difference. Conclusion: Despite using a large cohort and highly controlled laboratory conditions, we found no differences in melatonin suppression between euthymic patients with bipolar I disorder and healthy controls. These findings do not support the notion that supersensitivity is a valid endophenotype in bipolar I disorder.


Assuntos
Transtorno Bipolar/sangue , Luz , Melatonina/efeitos da radiação , Adulto , Estudos de Casos e Controles , Endofenótipos , Feminino , Humanos , Masculino , Melatonina/sangue , Pessoa de Meia-Idade , Estimulação Luminosa , Opsinas de Bastonetes
2.
Nervenarzt ; 90(11): 1162-1169, 2019 Nov.
Artigo em Alemão | MEDLINE | ID: mdl-30968196

RESUMO

Vitamin B12 and folic acid deficiencies are particularly frequent conditions in older people. Since these metabolic disorders represent relevant dyscognitive factors, the assessment of vitamin B12 and folic acid levels is essential in the diagnostic approach of cognitive disorders, such as mild cognitive impairment and dementia in an outpatient memory clinic. This article summarizes the relevant diagnostic and therapeutic aspects of vitamin B12 and folic acid deficiencies and their effects on cognition. The literature review is supplemented by a data analysis of a naturalistic cohort of 250 patients from this outpatient memory clinic.


Assuntos
Transtornos Cognitivos , Deficiência de Ácido Fólico/psicologia , Ácido Fólico , Deficiência de Vitamina B 12/psicologia , Vitamina B 12 , Idoso , Idoso de 80 Anos ou mais , Cognição , Transtornos Cognitivos/sangue , Transtornos Cognitivos/diagnóstico , Análise de Dados , Ácido Fólico/sangue , Humanos , Pacientes Ambulatoriais , Universidades , Vitamina B 12/sangue
3.
Psychother Psychosom Med Psychol ; 68(7): 281-289, 2018 Jul.
Artigo em Alemão | MEDLINE | ID: mdl-28838011

RESUMO

SUBJECT: Compared to other illicit drugs Methamphetamine (MethA) is used more frequently by women than by men. Assuming the biopsychosocial etiology model, the dependency is based on several factors in which women and men differ significantly. Systematic gender-differentiated knowledge is missing until today. METHOD: Based on a database research (PUBMED) the review examines biological, social and psychological as well as therapeutic aspects in MethA-dependent women. RESULTS: MethA-induced cognitive disturbance appear to have severer manifestations in women than in men. MethA-addicted women's lifestyle is often characterized by active and passive (sexualized) violence. They show an increased risk behavior; i. e. unprotected sexual intercourse with several partners. Their psychological comorbidities seem to be more pronounced and especially affect anxiety disorders and depressive syndromes. CONCLUSION AND CLINICAL RELEVANCE: In women, abuse and dependence of MethA are determined by psychological as well as social factors. However, further research is needed to improve prevention, counseling and therapy.


Assuntos
Transtornos Relacionados ao Uso de Anfetaminas/epidemiologia , Transtornos Relacionados ao Uso de Anfetaminas/terapia , Estimulantes do Sistema Nervoso Central , Metanfetamina , Feminino , Humanos , Masculino , Caracteres Sexuais , Fatores Sociológicos , Mulheres
4.
Biol Psychiatry Glob Open Sci ; 2(1): 28-35, 2022 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-36324599

RESUMO

Background: Bipolar disorder is a severe chronic mental disorder. There is a bidirectional relationship between disease course and circadian phase. Significant circadian phase shifts occur during transitions between episodes, but episodes can also be elicited during euthymia by forced rapid changes in circadian phase. Although an instability of circadian phase has been described in multiple observational reports, no studies quantifying the propensity to phase shift following an experimental standardized stimulus have been published. This study therefore aimed to assess whether patients with bipolar I disorder (BDI) are more prone to phase delay following blue light exposure in the evening than healthy control subjects. Methods: Euthymic participants with BDI confirmed by Structured Clinical Interview for DSM-IV Axis I (n = 32) and healthy control subjects (n = 55) underwent a 3-day phase shift protocol involving exposure to a standardized dose of homogeneous, constant, narrow bandwidth blue light (478 nm, half bandwidth = 18 nm, photon flux = 1.29 × 1015 photons/cm2/s) for 2 hours at 9:00 pm via a ganzfeld dome on day 2. On days 1 and 3, serial serum melatonin assessments during total darkness were performed to determine the dim light melatonin onset. Results: Significant differences in the light-induced phase shift between BDI and healthy control subjects were detected (F 1,82 = 4.110; p = .046), with patients with bipolar disorder exhibiting an enhanced phase delay (η2 = 0.49). There were no significant associations between the magnitude of the phase shift and clinical parameters. Conclusions: Supersensitivity of patients with BDI to light-induced phase delay may contribute to the observed phase instability and vulnerability to forced phase shifts associated with the disorder.

5.
World J Psychiatry ; 12(7): 944-957, 2022 Jul 19.
Artigo em Inglês | MEDLINE | ID: mdl-36051595

RESUMO

BACKGROUND: The rising number of people using methamphetamine leads to an increasing need for treatment options for this patient group. Evidence-based research on the efficacy of treatment programs for methamphetamine users is limited. Due to specific characteristics of methamphetamine users, the question arises whether established treatment methods for individuals using other substances can be effective for the treatment of methamphetamine dependence as well. We hypothesize that there are significant differences between the two groups that may affect the effectiveness of treatment and worsen the prognosis of treatment outcomes for methamphetamine users compared to consumers of other substances. AIM: To investigate potential differences in cognitive functioning and psychopathology between methamphetamine users and other substance users and possible correlations with treatment outcomes. METHODS: A total of 110 subjects were recruited for an observational, longitudinal study from a German inpatient addiction treatment center: 55 patients with methamphetamine dependence and 55 patients with dependence of other substances ("OS group"). Both groups were examined at beginning (baseline) and end of treatment (after 6 mo) with regard to treatment retention, craving, cognitive functioning, psychosocial resources, personality traits, depression, and other psychiatric symptoms. Instruments used were Raven's IQ test, Mannheimer craving scale, cognitrone cognitive test battery, NEO personality factors inventory, Hamilton depression scale, Becks depression inventory, and a symptom checklist. The statistical methods used were χ 2-test, t-test and multiple mixed ANOVAs. RESULTS: A total drop-out rate of 40% (methamphetamine-group: 36.4%; OS-group: 43.6%) was observed without significant differences between groups. At baseline, methamphetamine-group subjects significantly differed from OS-group individuals in terms of a lower intelligence quotient, fewer years of education, slower working speed, and decreased working accuracy, as well as less cannabinoid and cocaine use. Methamphetamine-group subjects further showed a significantly lower score of conscientiousness, depressive, and psychiatric symptoms than subjects from the OS-group. In both groups, a reduction of craving and depressive symptoms and an improvement of working speed and working accuracy was noted after treatment. CONCLUSION: There are differences between methamphetamine users and users of other drugs, but not with regard to the effectiveness of treatment in this inpatient setting. There are differences in cognitive function and psychopathology between methamphetamine and other drugs users. The existing treatment options seem to be an effective approach in treating methamphetamine dependence.

6.
Geburtshilfe Frauenheilkd ; 81(12): 1354-1361, 2021 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-34899048

RESUMO

Introduction First trimester screening for preeclampsia (PE) is based on the combined risks model. Recent trials demonstrate that variations in multiple of the medians (MoMs) of the screening markers influence the performance of the algorithm in different populations. The aim of this study is to compare the performance of the algorithm in two cohorts with different prevention strategies. Material and Methods All first trimester screening tests performed between January 2014 and April 2020 were included. Up to June 2017 pregnancies with a risk > 1 : 200 for early-onset PE (eoPE) were considered at risk and received 100 mg of aspirin (strategy A). From July 2017 onwards, pregnancies with a risk > 1 : 100 for preterm PE (pPE) received 150 mg of aspirin (strategy B). We compared the screen positive rates (SPR) and incidence of PE between the two screening approaches. Statistical analysis were performed with Graphpad 8.0. Results 3552 pregnancies were included; 1577 pregnancies were screened according to strategy A, 1975 pregnancies according to strategy B. The screen positive rate (SPR) for strategy A and B was 8.9 and 16.9% respectively (p < 0.0001) while the incidence of PE was 1.41 and 1.84% respectively (p = ns). Conclusion With a SPR of less than 10% we achieved a remarkably low rate of PE in our population, no further reduction in PE could be achieved by an increase in the SPR and LDA-prescription during the second screening period. The cut-off to define a pregnancy at risk for PE should be tailored to keep the SPR below 10% to avoid unnecessary treatment with aspirin.

7.
Psychiatry Res ; 281: 112599, 2019 11.
Artigo em Inglês | MEDLINE | ID: mdl-31629302

RESUMO

A continuously rising consumption of methamphetamine (MA) has been suggested to be associated with increasing cognitive dysfunction. The objective of this study was to investigate associations between cognitive functions and gender, drug using patterns and treatment-attending profiles of recently abstinent MA users over the course of six months abstinence. Data were collected from 108 participants in two inpatient rehabilitation centers. The mean duration of MA use was 11.5 years. Interviews and cognitive tests (cognitrone, Stroop, TMT, nback) were performed right after the withdrawal and again after approx. six months of abstinence. Comparisons and explorative analyses between the groups (gender, primary MA/ multidrug users, early dropouts/ completers) regarding cognitive variables were performed. At baseline a significant decline in general neuropsychological functioning and attention/concentration after ongoing years of consumption were found. After a period of six months abstinence, cognitive performances remained stable or improved significantly for cognitrone percentile and cognitive flexibility. Normal cognitive functions were measured in former MA users after acute withdrawal which remained stable and partly improved in those patients who refrained from substance abuse over six months. Continued long-term MA intake was the only identified indicator of poorer cognitive performance. These results point towards a regain of cognitive performance in patients abstinent from MA.


Assuntos
Transtornos Relacionados ao Uso de Anfetaminas/psicologia , Transtornos Cognitivos/psicologia , Cognição/fisiologia , Metanfetamina/efeitos adversos , Síndrome de Abstinência a Substâncias/psicologia , Adolescente , Adulto , Transtornos Relacionados ao Uso de Anfetaminas/diagnóstico , Transtornos Relacionados ao Uso de Anfetaminas/epidemiologia , Transtornos Cognitivos/diagnóstico , Transtornos Cognitivos/epidemiologia , Estudos de Coortes , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Testes Neuropsicológicos , Síndrome de Abstinência a Substâncias/diagnóstico , Síndrome de Abstinência a Substâncias/epidemiologia , Fatores de Tempo , Adulto Jovem
8.
Nucleic Acids Res ; 34(Database issue): D678-83, 2006 Jan 01.
Artigo em Inglês | MEDLINE | ID: mdl-16381957

RESUMO

Although tremendous effort has been put into synthetic libraries, most drugs on the market are still natural compounds or derivatives thereof. There are encyclopaedias of natural compounds, but the availability of these compounds is often unclear and catalogues from numerous suppliers have to be checked. To overcome these problems we have compiled a database of approximately 50,000 natural compounds from different suppliers. To enable efficient identification of the desired compounds, we have implemented substructure searches with typical templates. Starting points for in silico screenings are about 2500 well-known and classified natural compounds from a compendium that we have added. Possible medical applications can be ascertained via automatic searches for similar drugs in a free conformational drug database containing WHO indications. Furthermore, we have computed about three million conformers, which are deployed to account for the flexibilities of the compounds when the 3D superposition algorithm that we have developed is used. The SuperNatural Database is publicly available at http://bioinformatics.charite.de/supernatural. Viewing requires the free Chime-plugin from MDL (Chime) or Java2 Runtime Environment (MView), which is also necessary for using Marvin application for chemical drawing.


Assuntos
Bases de Dados Factuais , Preparações Farmacêuticas/química , Anti-Infecciosos/química , Anti-Infecciosos/uso terapêutico , Ensaios Clínicos como Assunto , Tratamento Farmacológico , Internet , Interface Usuário-Computador
9.
Life Sci ; 80(24-25): 2361-4, 2007 May 30.
Artigo em Inglês | MEDLINE | ID: mdl-17286990

RESUMO

Peripheral blood cells express the complete non-neuronal cholinergic system. For example synthesis of acetylcholine and nicotinic as well muscarinic receptors have been demonstrated in leucocytes isolated from human peripheral blood. In the present experiments mononuclear cells and granulocytes were isolated from the peripheral blood to investigate content and synthesis of acetylcholine as well as phenotypic functions like respiratory burst, phagocytosis and migration. Mononuclear cells (T-cells and monocytes) contained 0.36 pmol/10(6) cells acetylcholine, whereas acetylcholine content in granulocytes was 100-fold lower. Acetylcholine synthesis amounted to 23.2+/-4.7 nmol/mg protein/h and 2.90+/-0.84 in CD15+ (granulocytes) and CD3+ cells (T-lymphocytes), respectively. Neither atropine (blockade of muscarinic receptors) nor tubocurarine (blockade of nicotinic receptors) exerted an effect on the respiratory burst. Tubocurarine (30 muM), alone or in combination with atropine (1 microM), reduced phagocytosis in granulocytes by 13% and 19%, respectively (p<0.05). Spontaneous transwell migration of granulocytes was doubled by tubocurarine combined with atropine (p>0.05). Also alpha-bungarotoxin (10 microg/ml) enhanced spontaneous granulocyte migration, but hexamethonium (300 microM) was without effect. The present experiments demonstrate a cholinergic modulation of immune functions in peripheral leucocytes under in vitro conditions, i.e. in the absence of a neuronal innervation. Blockade of nicotine receptors (alpha1 muscular subtype) facilitates spontaneous migration of granulocytes.


Assuntos
Acetilcolina/metabolismo , Granulócitos/efeitos dos fármacos , Leucócitos Mononucleares/efeitos dos fármacos , Leucócitos Mononucleares/metabolismo , Antagonistas Muscarínicos/farmacologia , Antagonistas Nicotínicos/farmacologia , Acetilcolina/farmacologia , Atropina/farmacologia , Bungarotoxinas/farmacologia , Movimento Celular/efeitos dos fármacos , Cromatografia Líquida de Alta Pressão , Relação Dose-Resposta a Droga , Granulócitos/citologia , Granulócitos/metabolismo , Hexametônio/farmacologia , Humanos , Leucócitos Mononucleares/citologia , Neurônios/metabolismo , Fagocitose/efeitos dos fármacos , Explosão Respiratória/efeitos dos fármacos , Tubocurarina/farmacologia
10.
Environ Toxicol Chem ; 25(9): 2381-7, 2006 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-16986793

RESUMO

Cyanobacterial toxins have adverse effects on both terrestrial and aquatic plants. Microcystins are cyclic heptapeptides and an important group of cyanotoxins. When lake water contaminated with cyanobacterial blooms is used for spray irrigation, these toxins can come in contact with agricultural plants. During the exposure to these toxins, reactive oxygen species can form. These reactive oxygen species have a strong reactivity and are able to interact with other cellular compounds (lipids, protein, and DNA). Plants have antioxidative systems that will limit the negative effects caused by reactive oxygen species. These systems consist of enzymes, such as superoxide dismutase, catalase, and ascorbate peroxidase, and nonenzymatic substances, such as reduced glutathione or vitamins. The aim of the present study was to investigate the effects of cyanobacterial toxins (microcystins and anatoxin-a) and cyanobacterial cell-free crude extract on alfalfa (Medicago sativa) seedlings. Inhibition of germination and root growth was observed with toxin concentrations of 5.0 microg/L. Also, oxidative damage, such as lipid peroxidation, was detected after the exposure of alfalfa seedlings to the toxin. Reactive oxygen detoxifying enzymes were elevated, showing a marked response in alfalfa to oxidative stress caused by the exposure to cyanobacterial metabolites that might influence the growth and development of these plants negatively.


Assuntos
Toxinas Bacterianas/farmacologia , Cianobactérias/metabolismo , Germinação/efeitos dos fármacos , Toxinas Marinhas/farmacologia , Medicago sativa/efeitos dos fármacos , Peptídeos Cíclicos/farmacologia , Toxinas Bacterianas/metabolismo , Toxinas de Cianobactérias , Herbicidas/farmacologia , Toxinas Marinhas/metabolismo , Medicago sativa/crescimento & desenvolvimento , Microcistinas , Estresse Oxidativo , Paraquat/farmacologia , Peptídeos Cíclicos/metabolismo , Sementes/efeitos dos fármacos , Sementes/crescimento & desenvolvimento , Tropanos
11.
Life Sci ; 91(21-22): 1119-21, 2012 Nov 27.
Artigo em Inglês | MEDLINE | ID: mdl-22525378

RESUMO

AIMS: Circulating leucocytes express muscarinic (m) and nicotinic (n) receptors and synthesize acetylcholine (ACh) regulating various cell functions. Leucocytes from patients with cystic fibrosis contain less ACh; therefore it was tested whether the regulation of cellular functions like migration differed from healthy volunteers. MAIN METHODS: Peripheral blood (10-20 ml) was used, leucocytes were isolated by Ficoll® gradient and the commercial MIGRATEST® combined with flow cytometric analysis was applied (pore size 3 µm). KEY FINDINGS: In the absence of test substances 4900±1800 (n=10) leucocytes migrated within a time period of 2 h. In the presence of tubocurarine (TC, 30 µM) the cell number increased to 7500±2700 [n=10] corresponding to an increase of 162±20% (mean of individual experiments; p<0.02). Atropine (1 µM) was not effective (120±17%, n=7). Simultaneous application of atropine and TC produced a slightly higher effect than TC alone (185±23%; n=8); a 10-fold increase of TC and atropine resulted to a somewhat stronger effect (248±39%; n=8). When migration time was reduced to 30 min or the chemoattractant fMLP (0.05 µM) present neither atropine nor TC affected migration. Granulocytes isolated from patients with cystic fibrosis did not respond (2h migration) to 30 µM TC (control: 5180±1400 cells [n=10]; TC: 5800±1400 [n=10]). Also in the presence of atropine (1 µM) and TC (30 µM) a significant effect was not detected (5800±1300 [n=10]). SIGNIFICANCE: Auto-paracrine acetylcholine limits the migration of unstimulated peripheral granulocytes. This effect is impaired in cystic fibrosis most likely because of a reduced endogenous cholinergic tone.


Assuntos
Antagonistas Colinérgicos/farmacologia , Fibrose Cística/metabolismo , Fibrose Cística/patologia , Granulócitos/patologia , Receptores Muscarínicos/metabolismo , Receptores Nicotínicos/metabolismo , Adolescente , Adulto , Ensaios de Migração de Leucócitos , Movimento Celular/efeitos dos fármacos , Criança , Feminino , Granulócitos/citologia , Granulócitos/efeitos dos fármacos , Granulócitos/metabolismo , Humanos , Masculino , Adulto Jovem
12.
Planta ; 226(5): 1231-41, 2007 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-17598126

RESUMO

Arabidopsis thaliana and Cuscuta spec. represent a compatible host-parasite combination. Cuscuta produces a haustorium that penetrates the host tissue. In early stages of development the searching hyphae on the tip of the haustorial cone are connected to the host tissue by interspecific plasmodesmata. Ten days after infection, translocation of the fluorescent dyes, Texas Red (TR) and 5,6-carboxyfluorescein (CF), demonstrates the existence of a continuous connection between xylem and phloem of the host and parasite. Cuscuta becomes the dominant sink in this host-parasite system. Transgenic Arabidopsis plants expressing genes encoding the green fluorescent protein (GFP; 27 kDa) or a GFP-ubiquitin fusion (36 kDa), respectively, under the companion cell (CC)-specific AtSUC2 promoter were used to monitor the transfer of these proteins from the host sieve elements to those of Cuscuta. Although GFP is transferred unimpedly to the parasite, the GFP-ubiquitin fusion could not be detected in Cuscuta. A translocation of the GFP-ubiquitin fusion protein was found to be restricted to the phloem of the host, although a functional symplastic pathway exists between the host and parasite, as demonstrated by the transport of CF. These results indicate a peripheral size exclusion limit (SEL) between 27 and 36 kDa for the symplastic connections between host and Cuscuta sieve elements. Forty-six accessions of A. thaliana covering the entire range of its genetic diversity, as well as Arabidopsis halleri, were found to be susceptible towards Cuscuta reflexa.


Assuntos
Arabidopsis/parasitologia , Cuscuta/fisiologia , Microscopia Confocal , Microscopia Eletrônica de Transmissão , Microscopia de Fluorescência , Plantas Geneticamente Modificadas
13.
J Exp Bot ; 57(4): 911-21, 2006.
Artigo em Inglês | MEDLINE | ID: mdl-16467411

RESUMO

During the development of the haustorium, searching hyphae of the parasite and the host parenchyma cells are connected by plasmodesmata. Using transgenic tobacco plants expressing a GFP-labelled movement protein of the tobacco mosaic virus, it was demonstrated that the interspecific plasmodesmata are open. The transfer of substances in the phloem from host to the parasite is not selective. After simultaneous application of (3)H-sucrose and (14)C-labelled phloem-mobile amino acids, phytohormones, and xenobiotica to the host, corresponding percentages of the translocated compounds are found in the parasite. An open continuity between the host phloem and the Cuscuta phloem via the haustorium was demonstrated in CLSM pictures after application of the phloem-mobile fluorescent probes, carboxyfluorescein (CF) and hydroxypyrene trisulphonic acid (HPTS), to the host. Using a Cuscuta bridge (14)C-sucrose and the virus PVY(N) were transferred from one host plant to the another. The results of translocation experiments with labelled compounds, phloem-mobile dyes and the virus should be considered as unequivocal evidence for a symplastic transfer of phloem solutes between Cuscuta species and their compatible hosts.


Assuntos
Cuscuta/metabolismo , Interações Hospedeiro-Parasita/fisiologia , Pelargonium/metabolismo , Pelargonium/parasitologia , Aminoácidos/metabolismo , Transporte Biológico , Radioisótopos de Carbono , Cuscuta/citologia , Cuscuta/fisiologia , Corantes Fluorescentes/metabolismo , Modelos Biológicos , Pelargonium/citologia , Reguladores de Crescimento de Plantas/metabolismo , Plasmodesmos/fisiologia , Sacarose/metabolismo , Nicotiana/citologia , Nicotiana/parasitologia , Vicia faba/anatomia & histologia , Vicia faba/parasitologia , Xenobióticos/metabolismo
14.
J Chem Phys ; 124(21): 214306, 2006 Jun 07.
Artigo em Inglês | MEDLINE | ID: mdl-16774406

RESUMO

An analytical anharmonic six-dimensional three-sheeted potential energy surface for the ground and first excited states of the ammonia cation has been developed which is tailored to model the ultrafast photoinduced dynamics. Selected ab initio cuts, obtained by multireference configuration interaction calculations, have been used to determine the parameters of a diabatic representation for this Jahn-Teller and pseudo-Jahn-Teller system. The model includes higher-order coupling terms both for the Jahn-Teller and for the pseudo-Jahn-Teller matrix elements. The relaxation to the ground state is possible via dynamical pseudo-Jahn-Teller couplings involving the asymmetric bending and stretching coordinates. The photoelectron spectrum of NH3 and the internal conversion dynamics of NH3+ have been determined by wave packet propagation calculations employing the multiconfigurational time-dependent Hartree method. Three different time scales are found in the dynamics calculations for the second absorption band. The ultrafast Jahn-Teller dynamics of the two excited states occurs on a 5 fs time scale. The major part of the internal conversion to the ground state takes place within a short time scale of 20 fs. This fast internal conversion is, however, incomplete and the remaining excited state population does not decay completely even within 100 fs.

15.
J Phys Chem A ; 110(17): 5613-9, 2006 May 04.
Artigo em Inglês | MEDLINE | ID: mdl-16640354

RESUMO

The microsolvation of the CH(3)OH(2) hypervalent radical in methanol clusters has been investigated by density functional theory. It is shown that the CH(3)OH(2) radical spontaneously decomposes within methanol clusters into protonated methanol and a localized solvated electron cloud. The geometric and electronic structures of these clusters as well as their vibrational frequencies have been characterized. Resonance Raman intensities, associated with the s --> p transition of the unpaired electron, have been estimated for CH(3)OH(2)M(n) (M = CH(3)OH, n = 1-3) clusters. It is shown that with increasing cluster size the simulated spectra converge toward the resonance Raman spectrum of the solvated electron in methanol measured recently by Tauber and Mathies (J. Am. Chem. Soc. 2004, 126, 3414). The results suggest that CH(3)OH(2)M(n) clusters are useful finite-size model systems for the computational investigation of the spectroscopic properties of the solvated electron in liquid methanol.


Assuntos
Simulação por Computador , Elétrons , Metanol/química , Modelos Químicos , Análise Espectral Raman/métodos , Padrões de Referência , Sensibilidade e Especificidade , Solubilidade , Análise Espectral Raman/normas
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