Title: Recombination study of ions with electrons at temperatures below 300 K Author: Tomáš Kotrík Department: Department of Surface and Plasma Science Supervisor of the doctoral thesis: Prof. RNDr. Juraj Glosík, DrSc. Department of Surface and Plasma Science Abstract: Presented is the study of recombination of ions with electrons performed at low temperatures using the Flowing afterglow with Langmuir probe experimental technique. Studied was the dissociative recombination of H and D ions at temperatures 77 - 300 K. Apart from a two-body also a three-body recombination channel assisted by neutral He atoms was identified and studied. The obtained temperature dependence of the two-body recombination rate coefficient is in a good agreement with findings of other experimental and theoretical works. The dissociative recombination of HCO and DCO ions with electrons was studied in the temperature range 150 - 300 K. The observed temperature dependence of measured recombination rate coefficient for HCO and DCO ions (~T -1.3 and ~T -1.1 , respectively) is in agreement with the majority of previous experimental works and evokes that indirect mechanism governs the recombination process. The electron- assisted collisional-radiative recombination of Ar ions was for the first time studied at temperatures 50 - 300 K. The...

A B S T R A C T Title: Recombination of Ions in Plasma at 50 − 300 K Author: Peter Rubovič Supervisor: Prof. RNDr. Juraj Glosík, DrSc. Abstract: Main part of this doctoral thesis lies in a study of recom- bination of atomic and molecular ions in low temperature plasmatic environment with emphasis on effect of third bodies. Stationary After- glow equipped with Cavity Ring Down Spectrometer and Cryogenic Flowing Afterglow with Langmuir Probe II were used to obtain recom- bination rate coefficients. Electron assisted collisional radiative recom- bination of Ar+ ion was studied in the temperature range of 50−100 K and helium assisted collisional radiative recombination was observed too. Both H+ 3 and its isotopologue D+ 3 were studies in flowing after- glow and spectroscopically in stationary afterglow as well. Binary re- combination rate coefficients and ternary recombination rate coeffi- cients for helium assisted ternary recombination were determined in the temperature range of 50 − 250 K. These coefficients were deter- mined also for pure ortho- and para- nuclear spin configurations of H+ 3 in the temperature range of 80 − 200 K. Keywords: dissociative recombination, collisional radiative recombi- nation, H+ 3 , D+ 3 , Ar+ viii

Otitis media is a quite common disease, especially in children due largely to their underdeveloped Eustachian tubes. One potential factor, thought to be a large contributor to the disease, is an allergic reaction causing congestion and blockage of the Eustachian tube, leaving the middle ear prone to bacterial infection and effusions. The H3 receptor has recently been discovered in the nasal mucosa of humans and rodents and is linked to the immune response. Excess histamine released in an allergic response causes nasal vascular constriction and congestion. By blocking the H3 receptor, the local vasculature may be allowed to dilate, resulting in decongestion. This could play a large role in the treatment of otitis media with effusion. The effectiveness of betahistine dihydrochloride, an H3 receptor blocker, in providing possible relief from middle ear congestion was tested using a rat model. An allergic response was induced in rats followed by one of two betahistine dihydrochloride treatment regimens: drug delivery via transtympanic or intranasal route. Changes in Eustachian tube function were monitored during this process. Four measurements were used to measure the function of the Eustachian tube: passive opening pressure, passive closing pressure, active clearance of negative pressure, and Mucociliary transit time. Lower opening pressure and closing pressure, higher clearance of negative pressure, and shorter Mucociliary transit time were indications of better Eustachian tube function. Regardless of delivery method, no significant results were found among the experimental groups to suggest improved Eustachian tube function after drug treatment. Although the middle dose of betahistine dihydrochloride (50 mg/mL) delivered transtympanically followed the expected response outcome, the trend did not achieve statistical significance. Overall, the results of this study are inconclusive for measuring the beneficial effects of betahistine dihydrochloride on Eustachian tube function. Further investigations are being conducted to measure the magnitude and duration of the effects of allergic responses on Eustachian tube anatomy and physiology.

Nesta tese foi estudado um grupo de 28 compostos não-imidazólicos antagonistas do receptor H3 através de cálculos de orbitais moleculares utilizando os métodos de química quântica Austin Model 1, Hartree-Fock-Roothaan e Teoria do Funcional da Densidade com o objetivo de investigar possíveis relações entre descritores eletrônicos teóricos e as afinidades ligantes experimentais desses compostos (pKi). Observou-se nos resultados obtidos que as energias dos orbitais FERMOs (Frontier Effective-for-Reaction Molecular Orbitals) apresentam melhor correlação com os valores de pKi do que as energias dos orbitais de fronteira HOMO (Highest Occupied Molecular Orbital) e LUMO (Lowest Unoccupied Molecular Orbital). Além disso, verificou-se pelas análises de métodos multivariados PCA (Principal Componente Analysis) e HCA (Hierarchical Cluster Analysis) que um conjunto de quatro descritores foi capaz de separar os compostos em dois grupos distintos, o primeiro que apresenta valores de afinidades ligantes maiores e o segundo com menores valores de pKi. Esta separação foi possível com o uso dos seguintes descritores teóricos: energia do FERMO (εFERMO), carga derivada do potencial eletrostático no átomo de nitrogênio N1, índice de densidade eletrônica no átomo N1 (Σ(FERMO) ci2) e eletrofilicidade (ω\'). Estes descritores foram utilizados, posteriormente, para a construção de três equações de regressão pelo método PLS (Partial Least Squares). O melhor modelo de regressão gerou os seguintes parâmetros estatísticos Q2 = 0,88 e R2 = 0,927, obtidos com um conjunto treino e de validação externa de 23 e 5 moléculas, respectivamente. Logo após a avaliação da equação de regressão, juntamente com os valores dos descritores selecionados e outros não selecionados, foi sugerido que altos valores de energias dos FERMOs e de Σ(FERMO) ci2 em conjunto com baixos valores de eletrofilicidades e cargas extremamente negativas no átomo N1 são parâmetros relevantes para potencializar as afinidades ligantes de outros compostos a serem sintetizados, que apresentem estruturas químicas semelhantes às moléculas estudadas neste trabalho. Além disso, esses compostos podem ser considerados como doadores de elétrons e, logo, há uma grande probabilidade que tais moléculas interajam com o receptor histamínico H3 a partir de um processo de transferência de carga. / In this thesis, molecular orbital calculations were carried out on a set of 28 non-imidazole H3 antihistamine compounds using Austin Moldel 1, Hartree-Fock-Roothaan, and Density Functional Theory methods in order to investigate the possible relationships between electronic descriptors and binding affinity for H3 receptors (pKi). It was observed that the frontier effective-for-reaction molecular orbital (FERMO) energies were better correlated with pKi values than HOMO (Highest Occupied Molecular Orbital) and LUMO (Lowest Unoccupied Molecular Orbital) energy values. Exploratory data analysis through hierarchical cluster (HCA) and principal component analysis (PCA) showed a separation of the compounds into two sets by using four descriptors, one grouping the molecules with high pKi values, the other gathering low pKi value compounds. This separation was obtained with the use of the following descriptors: FERMO energies (εFERMO), charges derived from the electrostatic potential on the nitrogen atom (N1), electronic density indexes for FERMO on the N1 atom (Σ(FERMO) ci2), and electrophilicity (ω\'). These electronic descriptors were used to construct three quantitative structure-activity relationship (QSAR) models through the Partial Least Squares Method (PLS). The best model generated Q2 = 0.88 and R2 = 0.927 values obtained from a training set and external validation of 23 and 5 molecules, respectively. After the analysis of the PLS regression equation, the values for the selected electronic descriptors and other descriptors, it is suggested that high values of FERMO energies and of Σ(FERMO) ci2, together with low values of electrophilicity and pronounced negative charges on N1 appear as desirable properties for the conception of new molecules which might have high binding affinity. Moreover, these molecules can be classified as electron donating compounds and have a great probability of interacting through a charge transfer process with the biological receptor H3.

La sclérose en plaques est une maladie auto-immune dirigée contre les protéines de la myéline du cerveau. Plusieurs mécanismes physiopathologiques sont impliqués dans la SEP tels que l'inflammation, la démyélinisation et l’atteinte axonale. La SEP est associée à une expression accrue de cytokines et à une activation des rétrovirus endogènes humains (HERVs). Dans les conditions physiologiques, ces unités transcriptionnelles sont maintenues dans un état réprimé par un même mécanisme répresseur dépendant de la chromatine : la tri-méthylation de la lysine 9 de l’histone H3 (H3K9me3), qui crée un site de liaison aux protéines de la famille HP1. Nous avons trouvé qu’à la fois, les gènes de l’immunité et les HERVs nécessitent les protéines hétérochromatiniennes HP1α pour leur répression transcriptionnelle. Nous avons montré que la peptidylarginine déiminase 4, une enzyme qui joue un rôle dans la SEP, affaiblit la liaison de HP1α à la lysine 9 tri-méthylée de l'histone H3 en citrullinant l’arginine 8. Nous avons apporté la preuve que de multiples événements de la réactivation de la transcription chez les patients atteints de la SEP peuvent être expliqués par un défaut du mécanisme unique de répression génique. Nous avons également montré qu'il est possible de renforcer la répression de HP1 à l'aide de petites molécules. Par exemple, l’EGCG, un composé de thé vert, est en mesure de réduire à la fois l’expression des HERVs et des cytokines en augmentant l'activité de l’histone méthyltransférase SUV39H1. Cela conduit à une accumulation de la marque répressive H3K9me3, qui va favoriser la liaison de HP1.Ensemble, ces résultats suggèrent que HP1 est une composante importante de la SEP au niveau de la régulation des cytokines et des HERVs. / Multiple Sclerosis is an autoimmune disease resulting in damage to myelin structures of the brain. Several physiopathological mechanisms are involved in MS including inflammation, demyelination, and axonal damage. MS is associated with increased cytokine expression and activation of human endogenous retroviruses (HERVs). These two types of transcriptional units are kept in check by chromatin-dependent silencing associated with lysine 9 trimethylation of histone H3, and subsequent of HP1 proteins. We find that both the cytokine genes and the HERVs require the heterochromatin protein HP1 for their transcriptional repression. Furthermore, we have shown that the peptidylarginine deiminase 4, an enzyme with a suspected role in MS, weakens the binding of HP1 to tri-methylated histone H3 lysine 9 by citrullinating histone H3 arginine 8. We thereby evidence that multiple events of transcriptional reactivation in MS patients can be explained by deficiency of a single mechanism of gene silencing. We have also shown that it is possible to reinforce HP1 repression by using small molecules. For example, EGCG, a green tea compound, is able to reduce both HERVs and cytokines expression by increasing histone methyltransferase activity SUV39H1. This leads to increased accumulation of H3K9me3 repressive marks and favors binding of HP1. All together, these results suggest that HP1 is an important component of the regulation of cytokine genes and HERVs in MS patients.

Magister Pharmaceuticae - MPharm / The declining efficacy of antimalarial drugs against resistant Plasmodium falciparum strains in several endemic regions has amplified the world’s burden of neglected diseases. This has highlighted the need for alternate strategies for chemotherapy and chemoprophylaxis. Since malaria is prevalent primarily in third world countries, it is critical for novel therapies to be affordable. Previous research has found that some antihistamines possess inherent antimalarial activity and cause a marked reversal of chloroquine resistance in vitro and in vivo. Promising results have been demonstrated when chlorpheniramine was combined with chloroquine to reverse chloroquine resistance in two African studies (Sowunmi et al, 1997; Abok., 1997).Recently, astemizole and its principle human metabolite desmethylastemizole were identified as potent inhibitors of Plasmodium falciparum at sub-micromolar concentrations in both chloroquine sensitive and chloroquine resistant parasites, showing efficacy in vitro and in two mouse models. The promising results observed with these studies warrant a more comprehensive understanding of how antihistamines interact with the malaria parasite. Additionally, analysing the different structural and mechanistic characteristics of antihistamines may lead to the design and development of effective and affordable antimalarial agents or chloroquine resistance modulators.This thesis describes the antimalarial activity of mainly off-patent (generic) antihistamines by comparing the efficacy of a total of 24 antihistamines, representing histamine1, histamine2, and histamine3 receptor antagonists, against chloroquine-sensitive and chloroquine-resistant strains of Plasmodium falciparum. Cyproheptadine, ketotifen, loratadine, desloratadine, 3-(1HImidazol-4-yl) propyldi (p-fluorophenyl) methyl ether hydrochloride and ciproxifan display IC50 values less than 4μg/ml. There was no significant difference in the sensitivity to antihistamines among the chloroquine sensitive and resistant parasites tested. A tricyclic nucleus appears to be an important structural scaffold for antihistamines which exhibit low IC50 values. Synergistic studies indicate that enhancement of the antimalarial effect of chloroquine on P.falciparum was observed with the ethanolamines against the chloroquine sensitive parasites.Cyproheptadine, ketotifen and desloratadine exerted a marked synergistic action with chloroquine against chloroquine sensitive and resistant parasites. Chlorpheniramine exhibited synergism with chloroquine against resistant parasites only.Microscopic studies illustrate the effect of antihistamines on parasite morphology when compared to control. Using immunofluorescence microscopy, it was seen that ketotifen decreases haemoglobin localization while cyproheptadine increases haemoglobin localization in the parasite’s food vacuole. Western blots have confirmed these results, in addition to indicating that chlorpheniramine decreases the haemoglobin content in the parasite. The results confirm that certain antihistamines do indeed cause a reduction in the growth of malaria parasites. Furthermore, the histamine1 and histamine3 receptor antagonists are most active while histamine2 receptor antagonists have no antimalarial activity. Microscopic studies suggest that antihistamines do not exert their antimalarial effect via a single mechanism of action.I wish to express my sincere appreciation to the following people and institutions whose supervision and assistance made the presentation of this thesis possible:My supervisor, Prof. Henry Leng. Thank for always believing in me. Your encouragement, kindness and calm temperament has given me the strength to complete this thesis even when times were tough. Your wisdom and understanding will always be remembered.My co-supervisor, Prof. Pete Smith. I sincerely thank you for allowing me the opportunity to work in your laboratory and for welcoming me into the department. Your kindness and welcoming attitude will forever be appreciated. Thank you for always being patient and understanding.Dr. Uschi Wiehart. Thank you for all the help in the laboratory and always being there for me. I truly value and appreciate your contribution to this thesis. Your friendship has added so much positive energy to my life. Thank you for your wisdom, inspirational advice and unfaltering encouragement Sumaya and Ntokosi, your help, advice and company in tissue culture, are truly appreciated.The UCT, Pharmacology students. Thank for all your assistance.My dearest Pharmaceutical Chemistry colleagues, Jaques Joubert, for your friendship and support and for always listening and Prof. Peter Eagles, your kindness, support and wise advice has given me strength when I needed it most. To my other School of Pharmacy colleagues. Prof. Sarel Malan and team, for your support and motivation.To my family for all your support and wisdom and to my baby brothers; Omar and Uzair for all the joy that you bring to my life.And finally to my dearest husband, Zaheer for all your love and support throughout my studies and for taking me to UCT to culture parasites every weekend

Nesta tese foi estudado um grupo de 28 compostos não-imidazólicos antagonistas do receptor H3 através de cálculos de orbitais moleculares utilizando os métodos de química quântica Austin Model 1, Hartree-Fock-Roothaan e Teoria do Funcional da Densidade com o objetivo de investigar possíveis relações entre descritores eletrônicos teóricos e as afinidades ligantes experimentais desses compostos (pKi). Observou-se nos resultados obtidos que as energias dos orbitais FERMOs (Frontier Effective-for-Reaction Molecular Orbitals) apresentam melhor correlação com os valores de pKi do que as energias dos orbitais de fronteira HOMO (Highest Occupied Molecular Orbital) e LUMO (Lowest Unoccupied Molecular Orbital). Além disso, verificou-se pelas análises de métodos multivariados PCA (Principal Componente Analysis) e HCA (Hierarchical Cluster Analysis) que um conjunto de quatro descritores foi capaz de separar os compostos em dois grupos distintos, o primeiro que apresenta valores de afinidades ligantes maiores e o segundo com menores valores de pKi. Esta separação foi possível com o uso dos seguintes descritores teóricos: energia do FERMO (εFERMO), carga derivada do potencial eletrostático no átomo de nitrogênio N1, índice de densidade eletrônica no átomo N1 (Σ(FERMO) ci2) e eletrofilicidade (ω\'). Estes descritores foram utilizados, posteriormente, para a construção de três equações de regressão pelo método PLS (Partial Least Squares). O melhor modelo de regressão gerou os seguintes parâmetros estatísticos Q2 = 0,88 e R2 = 0,927, obtidos com um conjunto treino e de validação externa de 23 e 5 moléculas, respectivamente. Logo após a avaliação da equação de regressão, juntamente com os valores dos descritores selecionados e outros não selecionados, foi sugerido que altos valores de energias dos FERMOs e de Σ(FERMO) ci2 em conjunto com baixos valores de eletrofilicidades e cargas extremamente negativas no átomo N1 são parâmetros relevantes para potencializar as afinidades ligantes de outros compostos a serem sintetizados, que apresentem estruturas químicas semelhantes às moléculas estudadas neste trabalho. Além disso, esses compostos podem ser considerados como doadores de elétrons e, logo, há uma grande probabilidade que tais moléculas interajam com o receptor histamínico H3 a partir de um processo de transferência de carga. / In this thesis, molecular orbital calculations were carried out on a set of 28 non-imidazole H3 antihistamine compounds using Austin Moldel 1, Hartree-Fock-Roothaan, and Density Functional Theory methods in order to investigate the possible relationships between electronic descriptors and binding affinity for H3 receptors (pKi). It was observed that the frontier effective-for-reaction molecular orbital (FERMO) energies were better correlated with pKi values than HOMO (Highest Occupied Molecular Orbital) and LUMO (Lowest Unoccupied Molecular Orbital) energy values. Exploratory data analysis through hierarchical cluster (HCA) and principal component analysis (PCA) showed a separation of the compounds into two sets by using four descriptors, one grouping the molecules with high pKi values, the other gathering low pKi value compounds. This separation was obtained with the use of the following descriptors: FERMO energies (εFERMO), charges derived from the electrostatic potential on the nitrogen atom (N1), electronic density indexes for FERMO on the N1 atom (Σ(FERMO) ci2), and electrophilicity (ω\'). These electronic descriptors were used to construct three quantitative structure-activity relationship (QSAR) models through the Partial Least Squares Method (PLS). The best model generated Q2 = 0.88 and R2 = 0.927 values obtained from a training set and external validation of 23 and 5 molecules, respectively. After the analysis of the PLS regression equation, the values for the selected electronic descriptors and other descriptors, it is suggested that high values of FERMO energies and of Σ(FERMO) ci2, together with low values of electrophilicity and pronounced negative charges on N1 appear as desirable properties for the conception of new molecules which might have high binding affinity. Moreover, these molecules can be classified as electron donating compounds and have a great probability of interacting through a charge transfer process with the biological receptor H3.

La modification de l'activité neuronale peut engendrer des altérations dans des circuits neuronaux. L'activation des récepteurs couplés aux protéines G (RCPG) peux participer à des mécanismes à la base du développement de maladies comme l'addiction à la cocaïne. La consommation de cocaïne conduit à une augmentation de neurotransmetteurs tels que la dopamine, l'histamine et le glutamate qui activent des RCPG dans le cerveau. La signalisation des RCPG peut se faire au travers de monomères, d'homo- ou d'hétéromères de RCPG ainsi que par des interactions protéine - protéine, permettant entre autre une régulation croisée. Nous montrons que les récepteurs de la dopamine 1 (D1R) et de l'histamine 3 (H3R) induisent une signalisation croisée dans le striatum de rat vraisemblablement par la formation d'hétérodimères. Une administration chronique de cocaïne modifie la signalisation de ces récepteurs tant que la signalisation croisée des D1R et H3R. Les H3R et les récepteurs métabotropes du glutamate 1/5 (mGlu1/5R) sont fortement exprimés dans l'hippocampe et le striatum. Des expériences de comportement suggèrent que ces récepteurs seraient susceptibles de coordonner leurs signalisations par une régulation croisée. Nos expériences d'électrophysiologie, de mesure de Ca++ intracellulaire et de transduction du signal montrent effectivement une régulation croisée des récepteurs H3R et mGlu1/5R dans le cerveau de rat. De plus, nous montrons que la consommation chronique de cocaïne affecte la signalisation des H3R et mGlu1/5R de manière différente de son impacte sur leur signalisation croisée. Nos résultats démontrent l'existence d'une régulation croisée de certains RCPG dans le cerveau de rat. De plus, la consommation chronique de la cocaïne affecte différemment la signalisation induite par l'activation d'un récepteur et l'induction d'une signalisation croisée. / Alterations of neuronal activity, mediated by G-protein coupled receptors (GPCRs), can modulate neuronal circuits and are thought to be important in the development and expression of diseases as cocaine addiction. GPCR activity is regulated by various mechanisms, including protein-protein interactions in the membrane, permitting these receptors to crosstalk and form homo-and heteromers. Cocaine blocks monoamine reuptake leading to increased synaptic presence of various neurotransmitters including dopamine, histamine and glutamate in the brain. First we describe that dopamine D1 receptors (D1R) and histamine H3 receptors (H3R) crosstalk in the rodent brain. Chronic cocaine self-administration altered the crosstalk between D1R and H3R in the striatum, a brain structure involved in habit learning and motor control. The altered signaling was observed in both individual receptor signaling and by D1R-H3R crosstalk signaling. Both histamine H¬3R and metabotropic glutamate 1/5 receptors (mGlu1/5R) are highly expressed in the hippocampus and the striatum of rodents and they are involved in behaviors regulated by these structures. We describe that H3R and mGlu1/5R crosstalk in pyramidal neurons of the hippocampus and in the striatum of rats. In addition, we found that signaling through H3R and mGlu1/5R were differently affected by chronic cocaine self-administration than the apparent crosstalk between the receptors. These results show evidence of GPCR interactions in adult rodent brain and reveal that chronic cocaine self-administration differently affected crosstalk and single receptor mediated signaling.

5 Abstract Neuroblastoma is one of the most common cancer diseases diagnosed in children. This rapidly growing solid tumor is usually formed by hypoxic areas which arise as a consequence of inefficient and disorganized neovascularization. The cells stressed by hypoxia triggers transcription of many genes necessary for their survival, and conversely stop the production of proteins which are not necessarily needed for the survival in these severe conditions. The adaptation of cells to hypoxic conditions may appear due to the epigenetic regulation of metabolism associated with chromatin remodeling which involves the DNA methylation and also the posttranslational modifications of histones. Among the most important of these, there is the acetylation of lysine residues of histones associated with the DNA strands loosening, facilitated binding of transcription factors and the activation of gene expression. Thus, the first part of this study is concerned with changes in the acetylation of histones H3 and H4 of human neuroblastoma cell lines UKF-NB-3, UKF-NB-4, SH-SY5Y and SK-N-AS, cultured in parallel under standard culture conditions and in the absence of oxygen (hypoxia, 1% O2) for 24 hours, which are studied by Western blot analysis. Thereupon, the activity of histone deacetylases and histonacetyltransferases,...

Os camarões do gênero Atya Leach, 1816 são os maiores camarões da família Atyidae, sendo que as 13 espécies reconhecidas estão distribuídas em rios e riachos das regiões tropicais e subtropicais da América (vertentes atlântica e pacífica) e oeste da África. O primeiro relato de uma Atya ocorreu no séc. XVII e, desde então, novas espécies foram descritas e descrições prévias revisadas, produzindo um histórico de instabilidade e reclassificações. Embora ao longo do séc. XX revisões taxonômicas tenham estabilizado a sistemática do gênero, a variabilidade morfológica e distribuição geográfica trans-ístmica da espécie A. innocous gerou questionamentos. Além disso, mais recentemente trabalhos de filogenia molecular da família Atyidae que incluíram representantes de Atya suscitaram questões em relação à sistemática do gênero (possível não monofilia) e de algumas espécies como A. gabonensis, A. margaritacea e A. scabra. Visto que o uso de marcadores moleculares nunca foi empregado para a delimitação das espécies de Atya e que seu uso de forma complementar à morfologia poderia aperfeiçoar a sistemática do gênero, o objetivo do presente estudo foi avaliar por meio de dados moleculares as hipóteses taxonômicas das espécies A. gabonensis, A. innocous, A. margaritacea e A. scabra. Sequências dos genes mitocondriais 16S e Citocromo Oxidase I e gene nuclear Histona 3 foram geradas por meio de protocolos de extração e sequenciamento de DNA a partir do tecido de espécimes obtidos em empréstimos/doações. Potenciais espécies evidenciadas pelas análises de similaridade nucleotídicas (distâncias genéticas), compartilhamento de caracteres em um contexto evolutivo (reconstruções filogenéticas), Automatic Barcode Gap Discovery, Poisson Tree Processes e Generalized Mixed Yule Coalescence foram confrontadas com as hipóteses taxonômicas específicas atuais. A avaliação sistemática com dados moleculares aqui realizada, adicionalmente às informações morfológicas existentes na literatura sustentaram A. gabonensis como uma espécie de distribuição anfi-atlântica, mas não corroborou a hipótese de A. innocous como uma espécie trans-ístmica. Assim, o uso do nome A. innocous para as populações do Mar do Caribe e A. tenella para aquelas restritas ao Pacífico é sugerido. A espécie A. margaritacea, distribuída ao longo da costa pacífica da América foi considerada uma espécie válida e distinta de A. scabra, amplamente distribuída na vertente atlântica da América do Sul, África e Mar do Caribe. Contudo, é discutida a possibilidade de uma espécie críptica restrita no Golfo do México existir. Adicionalmente, o conhecimento existente e pertinente para futuros estudos de sistemática e taxonomia sobre os camarões do gênero Atya foram sumarizados e são apresentados. / The genus Atya Leach, 1816 shrimps are the largest of the Atyidae family, and the 13 acknowledge species are geographically distributed in rivers and stream in the tropical and subtropical regions of America (Atlantic and Pacific drainages) and West Africa. The first registry of an Atya was in the XVII century and since then new species were described and previous description revised in an eventful taxonomic historic. Although throughout the XX century taxonomic revisions stabilized the genus systematics, the morphological variability and the trans-isthmic geographic distribution of A. innocous caused questioning. Moreover, molecular phylogenetic studies that included Atya representatives raised doubt on the genus systematics (possibly non-monophyletism) and some species A. gabonensis A. margaritacea and A. scabra hypothesis. As molecular markers have never been used concerning Atya species delimitation complementary to the morphology and it could improve the genus systematics, the goal of this study was to evaluate with molecular markers the taxonomic hypothesis of the species A. gabonensis, A. innocous, A. margaritacea e A. scabra. Sequences of the mitochondrial genes 16S and Cytochrome Oxidase I and nuclear gene Histone 3 were generated by means of DNA extraction and sequence protocols from specimens obtained in loans/donations. Putative species evidenced by the analysis of nucleotide similarity (genetic distances), character sharing (phylogenetic reconstitutions), Automatic Barcode Gap Discovery, Poisson Tree Processes and Generalized Mixed Yule Coalescence were compared to the prevailing taxonomic hypothesis. The systematic evaluation with the molecular data of this study, in addition with the morphological information in the literature sustain A. gabonensis as an amphi-atlantic distributed species, but do not corroborated A. innocous hypothesis as an trans-isthmian species. In this sense, the use of A. innocous stricto sensu for the Caribbeans Sea populations and A. tenella to that restricted to the pacific drainage of America is suggested. Atya margaritacea, distributed along the pacific drainage of America, is considered a valid species distinct from A. scabra, widespread distributed in the Atlantic drainage of America and Africa, besides Caribbean Sea. However, the possibility of a cryptic species in the Gulf of Mexico population is discussed. Aditionally, the relevant knowledge to future systematic and taxonomy studies about the shrimps of the genus Atya were summarized and are shown.