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1.
Rev Neurol (Paris) ; 179(8): 914-922, 2023 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-37019741

RESUMO

Treatment strategies in chronic inflammatory demyelinating polyradiculoneuropathy (CIDP) must be adapted on a case-to-case basis. Validated and reproducible tools for monitoring treatment response are required at diagnosis, when initiating treatment and throughout follow-up. A task force of French neurologists, experts in neuromuscular disease reference centers, was assembled to provide expert advice on the management of typical CIDP with intravenous immunoglobulins (Ig), and to harmonize treatment practices in public and private hospitals. The task force also referred to the practical experience of treating CIDP with Ig at the diagnostic, induction and follow-up stages, including the assessment and management of Ig dependence, and following the recommendations of the French health agency.


Assuntos
Polirradiculoneuropatia Desmielinizante Inflamatória Crônica , Humanos , Polirradiculoneuropatia Desmielinizante Inflamatória Crônica/diagnóstico , Polirradiculoneuropatia Desmielinizante Inflamatória Crônica/terapia , Prova Pericial , Imunoglobulinas Intravenosas/uso terapêutico , França/epidemiologia
2.
Commun Biol ; 5(1): 998, 2022 09 21.
Artigo em Inglês | MEDLINE | ID: mdl-36130990

RESUMO

The reasons why some animals have developed larger brains has long been a subject of debate. Yet, it remains unclear which selective pressures may favour the encephalization and how it may act during evolution at different taxonomic scales. Here we studied the patterns and tempo of brain evolution within the order Carnivora and present large-scale comparative analysis of the effect of ecological, environmental, social, and physiological variables on relative brain size in a sample of 174 extant carnivoran species. We found a complex pattern of brain size change between carnivoran families with differences in both the rate and diversity of encephalization. Our findings suggest that during carnivorans' evolution, a trade-off have occurred between the cognitive advantages of acquiring a relatively large brain allowing to adapt to specific environments, and the metabolic costs of the brain which may constitute a disadvantage when facing the need to colonize new environments.


Assuntos
Carnívoros , Fósseis , Animais , Evolução Biológica , Encéfalo/fisiologia , Tamanho do Órgão
5.
Rev Med Interne ; 42(2): 110-119, 2021 Feb.
Artigo em Francês | MEDLINE | ID: mdl-33172708

RESUMO

Fabry disease is the second most frequent lysosomal storage disorder. It is a X-linked genetic disease secondary to alpha-galactosidase A enzyme deficiency. This is a progressive and systemic disease that affects both males and females. Classical symptoms and organ involvements are acral pain crisis, cornea verticillata, hypertrophic cardiomyopathy, stroke and chronic kidney disease with proteinuria. Nevertheless, organ damages can be missing or pauci-symptomatic and other common symptoms are poorly recognised, such as gastrointestinal or ear involvement. In classical Fabry disease, symptoms first appear during childhood or teenage in males, but later in females. Patients may have non-classical or late-onset Fabry disease with delayed manifestations or with single-organ involvement. Recognition of Fabry disease is important because treatments are available, but it may be challenging. Diagnosis is easy in males, with dosage of alpha-galactosidase A enzyme activity into leukocytes, but more difficult in females who can express normal residual activity. Other plasmatic biomarkers, such as lyso-globotriaosylceramide (lyso-Gb3), are interesting in females, but need to be associated with GLA gene analysis. In this review, we aimed at summarize the main clinical manifestations of Fabry disease and propose a practical algorithm to know how to diagnose this complex disease.


Assuntos
Doença de Fabry , Acidente Vascular Cerebral , Adolescente , Biomarcadores , Progressão da Doença , Doença de Fabry/complicações , Doença de Fabry/diagnóstico , Doença de Fabry/epidemiologia , Feminino , Humanos , Masculino , alfa-Galactosidase/genética
6.
Rev Med Interne ; 41(3): 180-188, 2020 Mar.
Artigo em Francês | MEDLINE | ID: mdl-31959364

RESUMO

Mucopolysaccharidosis are lysosomal storage diseases, secondary to the accumulation of mucopolysaccharides. Type 1 mucopolysaccharidosis is the most common form and affects between 0.69 and 1.66 newborns per 100,000. The severity of mucopolysaccharidosis is variable with lethal forms in utero and attenuated forms diagnosed in adults. The most common symptoms are short stature, facial dysmorphism, chronic articular pains that can mimic chronic inflammatory rheumatism, axial and peripheral bone involvement, hepatosplenomegaly and an early carpal tunnel. Depending on the type of mucopolysaccharidosis, corneal, cerebral or cardiac involvements are possible. Screening is based on the analysis of urinary glycosaminoglycans. The deficient enzyme assay and the gene analysis confirm the diagnosis. Mucopolysaccharidosis recognition is important for patient management and family screening. In addition, specific enzyme replacement therapy exists for certain types of mucopolysaccharidosis. Role of clinician is important to evoke and diagnose mucopolysaccharidosis.


Assuntos
Mucopolissacaridoses/diagnóstico , Adulto , Artrite Reumatoide/diagnóstico , Diagnóstico Diferencial , Terapia de Reposição de Enzimas , Feminino , Testes Genéticos , Humanos , Recém-Nascido , Mucopolissacaridoses/epidemiologia , Mucopolissacaridoses/terapia , Gravidez , Cuidado Pré-Natal , Prognóstico
7.
Rev Med Interne ; 41(2): 98-105, 2020 Feb.
Artigo em Francês | MEDLINE | ID: mdl-31898997

RESUMO

In France, clinical research involving human beings is regulated by the Jardé's law since November 2016. The law distinguishes interventional and non-interventional studies. Both need to be authorized by a Persons Protection Committee. Studies performed on medical data collected during standard clinical care are not considered as studies involving human beings. Medical data are personal data. French Data Protection Authority National has an important role, guarantying the respect of regulation on personal data. We summarize in this article the different types of studies and the role of regulatory authorities.


Assuntos
Pesquisa Biomédica/legislação & jurisprudência , Regulamentação Governamental , Segurança Computacional/legislação & jurisprudência , França , Humanos , Prontuários Médicos/legislação & jurisprudência , Prontuários Médicos/normas , Direitos do Paciente/legislação & jurisprudência
8.
Rev Med Interne ; 40(8): 517-522, 2019 Aug.
Artigo em Francês | MEDLINE | ID: mdl-30981561

RESUMO

Classification criteria for systemic sclerosis evolved over the last three decades, allowing an earlier classification. In the late 2000s, the EULAR Scleroderma Trials and Research Group validated very early and early systemic sclerosis criteria. Raynaud phenomenon, anti-nuclear antibody positivity and the puffy fingers are "Red flags" that must lead to refer the patient to a specialist and benefit from a capillaroscopy and the specific autoantibodies. At the stage of very early systemic sclerosis, pulmonary, cardiac and digestive involvements may be present and must be screened. Herein, we detail very early and early systemic sclerosis criteria, as well as the predictive factors of evolution towards a systemic sclerosis.


Assuntos
Escleroderma Sistêmico/classificação , Escleroderma Sistêmico/diagnóstico , Anticorpos Antinucleares/sangue , Autoanticorpos/sangue , Árvores de Decisões , Progressão da Doença , Diagnóstico Precoce , Humanos
10.
Eur J Neurol ; 25(12): 1439-1445, 2018 12.
Artigo em Inglês | MEDLINE | ID: mdl-29996003

RESUMO

BACKGROUND AND PURPOSE: Mitoxantrone (MITOX) has been used to treat patients with aggressive multiple sclerosis (MS) for decades. We aimed to describe the effectiveness and adverse events over 10 years post-MITOX in patients with relapsing and progressive MS from an exhaustive real-life database. METHODS: Data from patients who received MITOX before 1 January 2006 were collected from the MS Lorraine registry. Expanded Disability Status Scale (EDSS) scores and annual relapse rates (ARRs) year by year during follow-up and the year prior to MITOX were compared. Time to the first relapse and a 1-point increase in EDSS score were used in Cox multivariate models to find associations with potential predictive factors. RESULTS: A total of 411 patients were included. The ARR for the 155 relapsing patients had decreased from 2.0 (SD 1.20) the year before treatment to 0.3 (SD 0.31) by year 10 (P < 0.0001). The EDSS score increased from 2.8 (SD 1.44) to 4.8 (SD 1.90) by year 10 (P < 0.0001). A high ARR at MITOX initiation was associated with a longer time to a 1-point increase in EDSS score (hazard ratio, 0.81; 95% confidence interval, 0.67-0.99; P = 0.04). The EDSS score in 256 progressive patients increased from 5.0 (SD 1.33) to 6.5 (SD 1.26) by year 10 (P < 0.0001). We identified four cases of acute myeloid leukemias. CONCLUSIONS: Patients with the most active forms of MS are the most likely to benefit from MITOX in the long term.


Assuntos
Mitoxantrona/uso terapêutico , Esclerose Múltipla Crônica Progressiva/tratamento farmacológico , Esclerose Múltipla Recidivante-Remitente/tratamento farmacológico , Inibidores da Topoisomerase II/uso terapêutico , Adulto , Estudos de Coortes , Feminino , Seguimentos , Humanos , Masculino , Pessoa de Meia-Idade , Recidiva , Suspensão de Tratamento
11.
Rev Neurol (Paris) ; 174(6): 378-390, 2018 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-29673575

RESUMO

The diagnosis of multiple sclerosis (MS) and other demyelinating diseases of the central nervous system is challenging, and although the currently available biological and imaging tools offer considerable support to physicians, these tools often fail to provide a simple and final answer at the time of a first event. Thus, sets of diagnostic criteria have been published and tested on patient cohorts, and are now used in clinical trials and in daily clinical practice. These criteria have evolved over time to take into account physicians' and patients' needs, along with emerging paraclinical tests. The different presentations of MS have given rise to the use of a common classification system to identify patient profiles and adapt care protocols accordingly. This article reviews the various classifications of the forms and diagnostic criteria of MS and related syndromes, including neuromyelitis optica (NMO)/NMO spectrum disorders (NMOSDs), acute disseminated (demyelinating) encephalomyelitis (ADEM) and chronic lymphocytic inflammation with pontine perivascular enhancement responsive to steroids (CLIPPERS). Also discussed is their validity in the light of the currently available literature.


Assuntos
Doenças do Sistema Nervoso Central/classificação , Doenças do Sistema Nervoso Central/diagnóstico , Doenças Desmielinizantes/classificação , Doenças Desmielinizantes/diagnóstico , Encefalomielite Aguda Disseminada/diagnóstico , Humanos , Inflamação/classificação , Inflamação/diagnóstico , Esclerose Múltipla/diagnóstico , Neuromielite Óptica/diagnóstico , Síndrome
14.
Rev Med Interne ; 36(4): 237-42, 2015 Apr.
Artigo em Francês | MEDLINE | ID: mdl-25554401

RESUMO

PURPOSE: Cryofibrinogenemia is an unknown disorder and studies dedicated to it are limited. The aim of our study was to report on the incidence, clinical manifestations and associated diseases in patients with isolated cryofibrinogenemia. METHODS: This is a retrospective single-center study. Patients included in this study had a positive and isolated detection of cryofibrinogen between January 1st, 2011 and December 31st, 2012. Identification was possible through the database of the laboratory of immunology. RESULTS: Two hundred and eighty-one consecutive orders of cryofibrinogenemia were identified. Seventy-three patients had a positive detection of cryofibrinogenemia. Among them, 12 had an isolated cryofibrinogenemia and sixty-one patients (84%) had concomitant cryofibrinogenemia and cryoglobulinemia. The mean age was 59±19years. Seven patients were female (58%). Cutaneous manifestations were present in half case. Peripheral nerve involvement was present in 5 cases (42%) and rheumatic manifestations in 4 patients (33%). A thrombotic event was reported in 7 patients (58%). Renal impairment was present in 7 patients. The median cryofibrinogen concentration was 254±304mg/L. Five patients had a secondary cryofibrinogenemia. The most often prescribed treatment was corticosteroids. CONCLUSION: Cryofibrinogenemia is an unknown disorder. Testing for cryoglobulinemia is more frequent than for cryofibrinogenemia whereas clinical manifestations are similar. Detection of cryofibrinogen is positive in most of the cases, with an important prevalence of thrombotic events in this population. This study confirms the importance of conducting prospective studies on cryofibrinogenemia.


Assuntos
Crioglobulinemia , Crioglobulinemia/diagnóstico , Feminino , França , Hospitais Universitários , Humanos , Incidência , Masculino , Pessoa de Meia-Idade , Estudos Retrospectivos
15.
Cell Death Differ ; 21(1): 92-9, 2014 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-24037090

RESUMO

Clinical oncology heavily relies on the use of radiotherapy, which often leads to merely transient responses that are followed by local or distant relapse. The molecular mechanisms explaining radioresistance are largely elusive. Here, we identified a dual role of autophagy in the response of cancer cells to ionizing radiation. On one hand, we observed that the depletion of essential autophagy-relevant gene products, such as ATG5 and Beclin 1, increased the sensitivity of human or mouse cancer cell lines to irradiation, both in vitro (where autophagy inhibition increased radiation-induced cell death and decreased clonogenic survival) and in vivo, after transplantation of the cell lines into immunodeficient mice (where autophagy inhibition potentiated the tumour growth-inhibitory effect of radiotherapy). On the other hand, when tumour proficient or deficient for autophagy were implanted in immunocompetent mice, it turned out that defective autophagy reduced the efficacy of radiotherapy. Indeed, radiotherapy elicited an anti-cancer immune response that was dependent on autophagy-induced ATP release from stressed or dying tumour cells and was characterized by dense lymphocyte infiltration of the tumour bed. Intratumoural injection of an ecto-ATPase inhibitor restored the immune infiltration of autophagy-deficient tumours post radiotherapy and improved the growth-inhibitory effect of ionizing irradiation. Altogether, our results reveal that beyond its cytoprotective function, autophagy confers immunogenic properties to tumours, hence amplifying the efficacy of radiotherapy in an immunocompetent context. This has far-reaching implications for the development of pharmacological radiosensitizers.


Assuntos
Proteínas Reguladoras de Apoptose/metabolismo , Autofagia/efeitos da radiação , Raios gama , Proteínas de Membrana/metabolismo , Proteínas Associadas aos Microtúbulos/metabolismo , Animais , Proteínas Reguladoras de Apoptose/antagonistas & inibidores , Proteínas Reguladoras de Apoptose/genética , Proteína 5 Relacionada à Autofagia , Proteína Beclina-1 , Linfócitos T CD8-Positivos/imunologia , Linfócitos T CD8-Positivos/metabolismo , Linhagem Celular Tumoral , Humanos , Proteínas de Membrana/antagonistas & inibidores , Proteínas de Membrana/genética , Camundongos , Camundongos Endogâmicos BALB C , Camundongos Nus , Proteínas Associadas aos Microtúbulos/antagonistas & inibidores , Proteínas Associadas aos Microtúbulos/genética , Neoplasias/metabolismo , Neoplasias/patologia , Neoplasias/radioterapia , Interferência de RNA , RNA Interferente Pequeno/metabolismo , Transplante Heterólogo
16.
Cell Death Differ ; 21(1): 59-68, 2014 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-23787997

RESUMO

The exposure of calreticulin (CRT) on the surface of stressed and dying cancer cells facilitates their uptake by dendritic cells and the subsequent presentation of tumor-associated antigens to T lymphocytes, hence stimulating an anticancer immune response. The chemotherapeutic agent mitoxantrone (MTX) can stimulate the peripheral relocation of CRT in both human and yeast cells, suggesting that the CRT exposure pathway is phylogenetically conserved. Here, we show that pheromones can act as physiological inducers of CRT exposure in yeast cells, thereby facilitating the formation of mating conjugates, and that a large-spectrum inhibitor of G protein-coupled receptors (which resemble the yeast pheromone receptor) prevents CRT exposure in human cancer cells exposed to MTX. An RNA interference screen as well as transcriptome analyses revealed that chemokines, in particular human CXCL8 (best known as interleukin-8) and its mouse ortholog Cxcl2, are involved in the immunogenic translocation of CRT to the outer leaflet of the plasma membrane. MTX stimulated the production of CXCL8 by human cancer cells in vitro and that of Cxcl2 by murine tumors in vivo. The knockdown of CXCL8/Cxcl2 receptors (CXCR1/Cxcr1 and Cxcr2) reduced MTX-induced CRT exposure in both human and murine cancer cells, as well as the capacity of the latter-on exposure to MTX-to elicit an anticancer immune response in vivo. Conversely, the addition of exogenous Cxcl2 increased the immunogenicity of dying cells in a CRT-dependent manner. Altogether, these results identify autocrine and paracrine chemokine signaling circuitries that modulate CRT exposure and the immunogenicity of cell death.


Assuntos
Calreticulina/metabolismo , Interleucina-8/metabolismo , Proteínas de Saccharomyces cerevisiae/metabolismo , Animais , Antineoplásicos/uso terapêutico , Antineoplásicos/toxicidade , Apoptose/efeitos dos fármacos , Linhagem Celular Tumoral , Quimiocina CXCL2/metabolismo , Células Dendríticas/imunologia , Células Dendríticas/metabolismo , Células HCT116 , Células HeLa , Humanos , Interleucina-8/antagonistas & inibidores , Interleucina-8/genética , Camundongos , Camundongos Endogâmicos BALB C , Camundongos Endogâmicos C57BL , Mitoxantrona/uso terapêutico , Mitoxantrona/toxicidade , Neoplasias/tratamento farmacológico , Neoplasias/metabolismo , Neoplasias/patologia , Receptores de Interleucina-8A/antagonistas & inibidores , Receptores de Interleucina-8A/genética , Receptores de Interleucina-8A/metabolismo , Receptores de Interleucina-8B/antagonistas & inibidores , Receptores de Interleucina-8B/genética , Receptores de Interleucina-8B/metabolismo , Saccharomyces cerevisiae/classificação , Saccharomyces cerevisiae/metabolismo , Transdução de Sinais , Transcriptoma/efeitos dos fármacos
17.
Cell Death Differ ; 21(1): 79-91, 2014 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-23852373

RESUMO

The immunogenic demise of cancer cells can be induced by various chemotherapeutics, such as anthracyclines and oxaliplatin, and provokes an immune response against tumor-associated antigens. Thus, immunogenic cell death (ICD)-inducing antineoplastic agents stimulate a tumor-specific immune response that determines the long-term success of therapy. The release of ATP from dying cells constitutes one of the three major hallmarks of ICD and occurs independently of the two others, namely, the pre-apoptotic exposure of calreticulin on the cell surface and the postmortem release of high-mobility group box 1 (HMBG1) into the extracellular space. Pre-mortem autophagy is known to be required for the ICD-associated secretion of ATP, implying that autophagy-deficient cancer cells fail to elicit therapy-relevant immune responses in vivo. However, the precise molecular mechanisms whereby ATP is actively secreted in the course of ICD remain elusive. Using a combination of pharmacological screens, silencing experiments and techniques to monitor the subcellular localization of ATP, we show here that, in response to ICD inducers, ATP redistributes from lysosomes to autolysosomes and is secreted by a mechanism that requires the lysosomal protein LAMP1, which translocates to the plasma membrane in a strictly caspase-dependent manner. The secretion of ATP additionally involves the caspase-dependent activation of Rho-associated, coiled-coil containing protein kinase 1 (ROCK1)-mediated, myosin II-dependent cellular blebbing, as well as the opening of pannexin 1 (PANX1) channels, which is also triggered by caspases. Of note, although autophagy and LAMP1 fail to influence PANX1 channel opening, PANX1 is required for the ICD-associated translocation of LAMP1 to the plasma membrane. Altogether, these findings suggest that caspase- and PANX1-dependent lysosomal exocytosis has an essential role in ATP release as triggered by immunogenic chemotherapy.


Assuntos
Trifosfato de Adenosina/metabolismo , Antineoplásicos/toxicidade , Morte Celular/efeitos dos fármacos , Animais , Proteína 5 Relacionada à Autofagia , Morte Celular/imunologia , Linhagem Celular Tumoral , Membrana Celular/metabolismo , Conexinas/antagonistas & inibidores , Conexinas/genética , Conexinas/metabolismo , Proteínas de Ligação a DNA/antagonistas & inibidores , Proteínas de Ligação a DNA/genética , Proteínas de Ligação a DNA/metabolismo , Proteína HMGB1/metabolismo , Humanos , Proteína 1 de Membrana Associada ao Lisossomo/antagonistas & inibidores , Proteína 1 de Membrana Associada ao Lisossomo/genética , Proteína 1 de Membrana Associada ao Lisossomo/metabolismo , Lisossomos/metabolismo , Camundongos , Proteínas Associadas aos Microtúbulos/antagonistas & inibidores , Proteínas Associadas aos Microtúbulos/genética , Proteínas Associadas aos Microtúbulos/metabolismo , Miosina Tipo II/metabolismo , Proteínas do Tecido Nervoso/antagonistas & inibidores , Proteínas do Tecido Nervoso/genética , Proteínas do Tecido Nervoso/metabolismo , Interferência de RNA , RNA Interferente Pequeno/metabolismo , Proteínas de Ligação a RNA/antagonistas & inibidores , Proteínas de Ligação a RNA/genética , Proteínas de Ligação a RNA/metabolismo , Quinases Associadas a rho/antagonistas & inibidores , Quinases Associadas a rho/genética , Quinases Associadas a rho/metabolismo
18.
Rev Med Interne ; 34(3): 171-3, 2013 Mar.
Artigo em Francês | MEDLINE | ID: mdl-23218067

RESUMO

INTRODUCTION: Thymomas, benign or malignant, may be associated with autoimmune diseases. They are classically associated with myasthenia gravis, neuromyotonia, or pure red cell aplasia. CASE REPORT: We here report, to the best of our knowledge, the first description of an association between thymoma and Reynolds syndrome (systemic sclerosis associated with primary biliary cirrhosis) in an 80-year-old woman. CONCLUSION: The suspected pathogenesis of this association could be a thymus escape of auto-reactive T lymphocytes and the consecutive development of an auto-immune disorder.


Assuntos
Cirrose Hepática Biliar/diagnóstico , Escleroderma Sistêmico/diagnóstico , Timoma/diagnóstico , Neoplasias do Timo/diagnóstico , Idoso de 80 Anos ou mais , Feminino , Humanos , Síndrome de Sjogren/diagnóstico , Síndrome
19.
Phys Rev E Stat Nonlin Soft Matter Phys ; 87: 0327011-327014, 2013 Mar 04.
Artigo em Inglês | MEDLINE | ID: mdl-24976798

RESUMO

Radiopharmaceuticals emitting Auger electrons are often injected into patients undergoing cancer treatment with targeted radionuclide therapy (TRT). In this type of radiotherapy, the radiation source is radial and most of the emitted primary particles are low-energy electrons (LEEs) having kinetic energies distributed mostly from zero to a few hundred electron volts with very short ranges in biological media. These LEEs generate a high density of energy deposits and clustered damage, thus offering a relative biological effectiveness comparable to that of alpha particles. In this paper, we present a simple model and corresponding measurements to assess the energy deposited near the site of the radiopharmaceuticals in TRT. As an example, a calculation is performed for the decay of a single 125I radionuclide surrounded by a 1-nm-radius spherical shell of cytosine molecules using the energy spectrum of LEEs emitted by 125I along with their stopping cross sections between 0 and 18 eV. The dose absorbed by the cytosine shell, which occupies a volume of 4 nm3, is extremely high. It amounts to 79 kGy per decay of which 3%, 39%, and 58% is attributed to vibrational excitations, electronic excitations, and ionization processes, respectively.

20.
J Chem Phys ; 137(11): 115103, 2012 Sep 21.
Artigo em Inglês | MEDLINE | ID: mdl-22998289

RESUMO

The absolute cross sections (CSs) for vibrational excitations of cytosine by electron impact between 0.5 and 18 eV were measured by electron-energy loss (EEL) spectroscopy of the molecule deposited at monolayer coverage on an inert Ar substrate. The vibrational energies compare to those that have been reported from IR spectroscopy of cytosine isolated in Ar matrix, IR and Raman spectra of polycrystalline cytosine, and ab initio calculation. The CSs for the various H bending modes at 142 and 160 meV are both rising from their energy threshold up to 1.7 and 2.1 × 10(-17) cm(2) at about 4 eV, respectively, and then decrease moderately while maintaining some intensity at 18 eV. The latter trend is displayed as well for the CS assigned to the NH(2) scissor along with bending of all H at 179 meV. This overall behavior in electron-molecule collision is attributed to direct processes such as the dipole, quadrupole, and polarization contributions, etc. of the interaction of the incident electron with a molecule. The CSs for the ring deformation at 61 meV, the ring deformation with N-H symmetric wag at 77 meV, and the ring deformations with symmetric bending of all H at 119 meV exhibit common enhancement maxima at 1.5, 3.5, and 5.5 eV followed by a broad hump at about 12 eV, which are superimposed on the contribution due to the direct processes. At 3.5 eV, the CS values for the 61-, 77-, and 119-meV modes reach 4.0, 3.0, and 4.5 × 10(-17) cm(2), respectively. The CS for the C-C and C-O stretches at 202 meV, which dominates in the intermediate EEL region, rises sharply until 1.5 eV, reaches its maximum of 5.7 × 10(-17) cm(2) at 3.5 eV and then decreases toward 18 eV. The present vibrational enhancements, correspond to the features found around 1.5 and 4.5 eV in electron transmission spectroscopy (ETS) and those lying within 1.5-2.1 eV, 5.2-6.8 eV, and 9.5-10.9 eV range in dissociative electron attachment (DEA) experiments with cytosine in gas phase. While the ETS features are ascribed to shape resonances associated with the electron occupation of the second and third antibonding π-orbitals of the molecule in its ground state, the correspondence with DEA features suggests the existence of common precursor anion states decaying with certain probabilities into the vibrationally excited ground state.


Assuntos
Citosina/química , Elétrons , Espectroscopia de Perda de Energia de Elétrons , Vibração
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