Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Oxidative stress is a process characterized by the antioxidant defense system decrease and/or an excessive reactive species (RS) production. RS are substances capable of attacking proteins, lipids and DNA. The oxidative damage caused to lipids is known as lipid peroxidation, which leads to the increase of malondialdehyde (MDA) levels. Oxidative stress is involved in the pathogenesis of many chronic diseases, including diabetes, cancer, Parkinson s disease and damaged tissue in exposed to chemical agents, such as neurotoxicity, hematotoxicity and nefrotoxicity. It is known that there is a close relation between organic solvents, present in paints, and oxidative stress. Thus, the body has an elaborate antioxidant defense system, the exogenous antioxidants, such as lipid soluble vitamins, and the endogenous system, such as antioxidant enzymes. In this study a method has been validated and optimized for simultaneous quantification of retinol, α-tocopherol, lycopene and β- carotene using high performance liquid chromatography (HPLC-UV/fluorescence). The analytical parameters of validation analyzed were linearity, precision, accuracy, recovery and limits of detection (LOD) and quantification (LOQ). For all the vitamins analyzed, the linear regression coefficients were > 0.99, CV% < 5%;% bias < ± 6% recovery > 92% and the LOD and LOQ values obtained were satisfactory for routine clinical application for all analytes. The validated method was applied to a group of occupationally exposed to paints (n = 45) and a non-exposed group (control group, n = 30). The results indicated that all vitamins, except vitamin E, were significantly lower in the exposed group. Moreover, the possible correlation between endogenous and exogenous antioxidants and lipid damage was evaluated. Quantifications were done to assess endogenous antioxidants, reduced glutathione (GSH) in erythrocytes, the enzymes superoxide dismutase (SOD) and catalase (CAT) in whole blood through spectroscopic methods, and malondialdehyde (MDA) levels in plasma through HPLC-VIS in both study groups, exposed (n=42) and controls (n=28). The biological monitoring was performed by measurement of blood toluene, since in previous studies, it was suggested that this solvent would be the major inducer of lipid peroxidation. Despite the low levels of toluene found, exposed workers presented higher levels of MDA and the antioxidant enzymes (SOD and CAT) activities were significantly elevated when compared with the control group; and this increase was accompanied by depletion of GSH levels. Also, several correlations were observed between MDA and the enzymatic (SOD and CAT) and non-enzymatic antioxidants (GSH), and with lipid-soluble vitamins as well, except vitamin E. Through statistical tests the antioxidants which have a greater influence on the levels of MDA were evaluated. Among the antioxidants tested, GSH and carotenoids (mainly β- carotene) were suggested as main responsible for the reduction of lipid peroxidation. Thus, it can be suggested that high intakes of exogenous antioxidants, such as carotenoids,, tend to decrease lipid damage in occupationally exposed individuals to solvents constituent of paints. / O estresse oxidativo é um processo caracterizado pela diminuição do sistema de defesa antioxidante e/ou por uma produção excessiva de espécies reativas (ERs). As ERs são substâncias capazes de lesar proteínas, lipídios e DNA. Quando os lipídios são atingidos ocorre um processo chamado de peroxidação lipídica que leva ao aumento nos níveis de malondialdeído (MDA). O estresse oxidativo está envolvido com a patogênese de muitas doenças crônicas, como diabetes, câncer, doença de Parkinson e em danos teciduais em expostos a agentes químicos, como neurotoxicidade, hematotoxicidade e nefrotoxicidade. Sabe-se que existe uma estreita relação entre os solventes orgânicos, presentes em tintas, e o estresse oxidativo. Diante disso, o organismo dispõe de um elaborado sistema de defesa antioxidante, os antioxidantes exógenos, como as vitaminas lipossolúveis e o sistema endógeno como enzimas antioxidantes. Dessa forma, nesse estudo foi primeiramente otimizada e validada metodologia para simultânea quantificação de antioxidantes exógenos: retinol, α-tocoferol, licopeno e β-caroteno, utilizando cromatografia líquida de alta eficiência (CLAE-VIS/fluorescência). Os parâmetros analíticos de validação analisados foram linearidade, precisão, exatidão, recuperação e limites de detecção (LD) e quantificação (LQ). Para todas as vitaminas analisadas, os coeficientes de regressão linear foram > 0,99; CV% < 5%; bias% < ± 6%; recuperação > 92% e os valores de LD e LQ obtidos foram satisfatórios para aplicação na rotina clínica. O método validado foi aplicado em um grupo de expostos ocupacionalmente a tintas (n=45) e um grupo de não expostos (controle, n=30). Os resultados indicaram que todas as vitaminas, exceto a vitamina E, foram significativamente menores no grupo exposto. Além disso, avaliou-se o possível efeito protetivo de antioxidantes exógenos e endógenos sobre o dano lipídico. Foram realizadas as dosagens dos antioxidantes endógenos, glutationa reduzida (GSH) em eritrócitos, das enzimas superóxido dismutase (SOD) e catalase (CAT) em sangue total por métodos espectrofotométricos e os níveis de malondialdeído (MDA) em plasma por CLAE-VIS nos dois grupos de estudo, expostos (n=42) e controles (n=28). A monitorização biológica foi realizada através da dosagem de tolueno sanguíneo, uma vez que, em trabalhos prévios, foi sugerido que este solvente seria o principal indutor de peroxidação lipídica. Apesar dos baixos níveis de tolueno sanguíneo encontrados, os trabalhadores expostos apresentaram níveis de MDA e atividade das enzimas antioxidantes (SOD e CAT) significativamente elevados, quando comparados com o grupo controle e esse aumento foi acompanhado de depleção nos níveis de GSH. Ainda, foram observadas várias correlações entre os níveis de MDA e os antioxidantes endógenos enzimáticos (SOD e CAT) e não enzimático (GSH) e ainda com as vitaminas lipossolúveis, exceto vitamina E. Através de testes estatísticos foram avaliados quais antioxidantes teriam uma maior influência nos níveis de MDA. Dentre os antioxidantes analisados, a GSH e os carotenóides (principalmente o β- caroteno) foram sugeridos como principais responsáveis pela redução da peroxidação lipídica. Com isso, pode-se sugerir que aumento nos níveis de carotenóides, via dieta, tendem a diminuir o dano lipídico em indivíduos ocupacionalmente expostos a solventes constituintes de tintas.

Made available in DSpace on 2016-06-02T19:22:53Z (GMT). No. of bitstreams: 1 3145.pdf: 4807955 bytes, checksum: e7ba1c165199af2b5606877c0fadf24b (MD5) Previous issue date: 2010-03-12 / Universidade Federal de Sao Carlos / The aim of the present study was to investigate the effects of resistance training on skeletal muscle lipid content, liver lipid content, heart lipid content, fat depots and lipid profile in ovariectomized rats. Wistar adult female rats were grouped into: sedentary (Sed-intact); ovariectomized sedentary (Sed-Ovx); strength trained (ChronicEx-intact) and ovariectomized strength trained (ChronicEx-Ovx) (n= 10 per group). A 12-week strength training period that consisted in climbing a 1.1-m vertical ladder with weights attached to rats tail was used. The sessions were performed once every 3 days with 4-9 climbs and 8-12 dynamic movements per climb. Ovariectomy increased liver lipid content, fat depots, heart and muscle lipid content. There was an increase in atherogenic index and negative change in lipid profile due to ovariectomy. Resistance training decreased lipid content in liver, soleus, tibialis anterior, fat depots (mesenteric and retroperitoneal) and lipid profile, independently of ovarian hormone status. These results indicate the potential benefits of resistance training as an alternative strategy to control the effects of ovariectomy on fat depot, lipid profile, and tissue lipid content. / O objetivo do estudo foi investigar os efeitos do treinamento de força sobre o conteúdo lipídico no músculo esquelético, fígado, coração, depósitos de gorduras e perfil lipídico em ratas ovariectomizadas. Ratas fêmeas adultas foram divididas em quarto grupos: Sedentário (Sed-Intacto); Sedentário ovariectomizado (Sed-Ovx); Treinado intacto (CrônicoEx-Intacto); Treinado ovariectomizado (CrônicoEx-Ovx) (n = 10 por grupo). Foi realizado um período de 12 semanas de treinamento de força que consistia em subidas de uma escada vertical de 1,1 metros, com peso atado no rabo. As sessões foram realizadas uma vez a cada três dias com 4- 9 subidas e 8-12 movimentos por subida. Foram analisados os conteúdos de lipídios no músculo esquelético, fígado, coração, depósitos de gorduras (urogenital, mesentérico e retroperitoneal) e perfil lipídico. Ovariectomia aumentou o conteúdo lipídico no fígado, músculos esqueléticos, coração e depósitos de gordura. Foi observado um aumento no índice aterogênico e mudanças negativas no perfil lipídico devido à ovariectomia. O treinamento de força diminuiu o conteúdo de lipídio hepático, nos músculos esqueléticos sóleo, tibial anterior, depósitos de gordura (mesentérico e retroperitoneal) e perfil lipídico independente do estado hormonal ovariano. Esses resultados indicam os benefícios potenciais do treinamento de força com uma estratégia alternativa para controlar os efeitos da ovariectomia sobre os depósitos de gordura, perfil lipídico e conteúdo tecidual de lipídio.

The enzyme 3-Hydroxy-3- Methylglutaryl Coenzyme A Reductase catalyzes the rate limiting step of hepatic cholesterol biosynthesis and is unique among the enzymes in the early part of the pathway in that it is membrane bound. This gives rise to potential regulation of the enzyme through interactions with the endoplasmic reticulum membrane. A purification procedure has been developed which consistently produces enzyme of high specific activity. In order to fully characterize the interactions between HMG-CoA reductase and the lipids in its immediate environment, HMG-CoA reductase was purified to homogeneity and shown to be a protein-lipid complex.

O cultivo de Caiman yacare demanda grandes gastos com alimentação, deste modo, é necessário formular dietas mais baratas e mais eficientes para a engorda destes animais. Uma possibilidade de redução nos custos é o acréscimo de lipídeos de origem vegetal. Neste trabalho, analisou-se o processo de absorção de óleo de soja pelo intestino de Caiman yacare para avaliar possíveis alterações patológicas pelo uso deste óleo na mucosa intestinal de um animal carnívoro. A absorção de óleo de soja ocorreu massiçamente pelo intestino delgado, gerando esteatose intestinal temporária e formando quilomícrons pequenas, que foram transportadas pelo sistema linfático. Outros parâmetros que indicam ausência de patologias na mucosa intestinal, como alteração na proliferação celular, lesão tecidual, recrutamento de granulócitos, formação de heterófilos tóxicos e degranulação de mastócitos, não foram alterados, indicando o potencial uso de óleo de soja na dieta de Caiman yacare. / Cultivation of Caiman yacare demands large financial expenditures on food, so it is desirable to reduce costs by formulating cheaper and more efficient feedings. The soybean oil addition in the diet is an opportunity to reduce spending, but very little is known about the effects of vegetable-origin oils in this carnivore species health. Here we describe the process of soybean oil absorption by the intestine of Cayman yacare in order to evaluate possible intestinal pathologies caused by the soybean oil. Soybean oil absorption occurred massively across the intestine, caused temporary intestinal steatosis and produced small-sized chylomicrons that were carried away from the intestine by the lymphatics. Some mucosal integrity parameters analyzed such as enterocyte proliferation, epithelial damage, granulocyte recruitment, toxic heterophil formation and mast cell degranulation were not altered, suggesting soybean oil may potentially be used in Caiman yacare feedings.

O presente trabalho teve o objetivo de desenvolver uma formulação tópica contendo os filtros solares benzofenona-3 e avobenzona microencapsulados em associação com filtro solar não encapsulado octocrileno e nanoparticulas lipídicas sólidas contendo rutina (formulação completa) e avaliar a eficácia fotoquimiopreventiva dessa formulação usando biópsias de pele humana e pele reconstruída in vitro. Microparticulas lipídicas sólidas contendo grandes quantidades de filtros solares, benzofenona-3 e avobenzona foram obtidas pela técnica do spray congealing com propriedades adequadas para aplicação tópica. Além disso, o processo de microencapsulação foi capaz de diminuir a penetração de benzofenona-3 na pele, aumentar a estabilidade da avobenzona frente à radiação ultravioleta A e a capacidade fotoprotetora desses filtros microencapsulados em formulações tópicas quando expostos a radiação ultravioleta. Nanopartículas lipídicas sólidas contendo o flavonóide rutina foram produzidas pelo processo de homogeneização a alta pressão e suas condições foram otimizadas pelo método da desejabilidade rendendo nanopartículas lipídicas sólidas com tamanho médio de 74,22 ±2,77 nm, índice de polispersividade de 0,161±0,03 e eficiência de encapsulação de 98,90 ±0,25 %. Em adição, as nanopartículas mostraram serem capazes de proteger a viabilidade celular de fibroblastos de ratos L929 irradiados com radiação ultravioleta A e B. Para a eficácia fotoquimiopreventiva a formulação completa foi capaz de evitar/diminuir a formação de células apoptóticas, caspase-3, dímeros de ciclobutanodipirimidina, metaloproteinases e peroxidação lipídica em pele humana e pele reconstruída expostos a UVB. O processo tecnológico de microencapsulação e nanoencapsulação dos ativos avaliados mostrou ser eficaz, não comprometendo as propriedades de fotoproteção dos filtros solares e rutina, apresentando resultados similares ou melhores do que as formulações contendo os ativos na forma livre. Portanto, o desenvolvimento de formulações contendo ativos microencapsulados e nanoencapsulados é uma alternativa interessante para o emprego em produtos comerciais para proteção solar, por diminuir as características indesejáveis como penetração e instabilidade, melhorando as propriedades fotoprotetoras e evitando a necessidade de desenvolver novos compostos com propriedades fotoprotetoras. / This study aimed the pharmaceutical development of a topical formulation containing an association of microencapsulated sunscreens benzophenone-3 and avobenzone, free sunscreen octocrylene and rutin flavonol solid lipid nanoparticles (complete formulation). This formulation was assessed for photochemoprotective ability using human skin obtained surgically and reconstructed human skin. Solid lipid microparticles containing large amounts of sunscreens benzophenone-3 and avobenzone were obtained by the spray congealing technique under conditions that allowed the manufacture of microparticles with suitable properties for topical application. The microencapsulation conditions were also able to reduce the penetration of benzophenone-3 through the skin, enhanced the stability of avobenzone against the ultraviolet radiation (UVR) and increased the photoprotective ability of both filters in topical formulations exposed to UVR. Solid lipid nanoparticles containing rutin were produced by the high pressure homogenization process whose conditions were optimized using the desirability method, yielding nanoparticles with size of 74.22 ± 2.77 nm, polispersivity index of 0.161 ± 0.03 and encapsulation efficiency of 98.90 ± 0.25%. In addition, the nanoparticles were able to avoid the death of L929 mice fibroblasts exposed to UVR A and B. For the photochemopreventive ability studies, the complete formulation was able to reduce/avoid the induction of apoptotic cells, caspase-3, CPDs, metalloproteinases and lipid peroxides in human skin obtained surgically and reconstructed human skin in vitro exposed to UVB.Thus, the micro and nanoencapsulation solved some intrinsic problems related to sunscreens and rutin without, however, compromising their photohemoprotective ability, since the results showed similar or better efficacy when compared to the formulations containing actives in free form. Therefore, the development of formulations containing microencapsulated and nanoencapsulated compounds is an interesting alternative for employment in commercial products for sun protection by decreasing the undesirable characteristics, such as penetration and instability, improving the photoprotective properties and avoiding the need to develop new compounds with photoprotective characteristics.

Ayant une structure particulière avec une tête hydrophile et une queue hydrophobe, des molécules amphiphile ont de nombreuses applications importantes, comme par exemple, la fabrication des détergents, la protection et la fonctionnalisation de surfaces, etc. Des agrégats de diverses formes, micelles, véhicules, membranes etc., peuvent se former à partir des amphiphiles. La complexité de ces agrégats moléculaires rend l’étude théorique de ce type de systèmes extrêmement difficile. Jusqu’à présent, notre connaissance sur l’interaction entre des nanoparticules et des agrégats des amphiphiles reste encore incomplète. A l’aide de certaines méthodes de simulations moléculaire et une approche théorique, nous avons entrepris une série d’études pour mieux comprendre les questions fondamentales suivantes :1. Comment la présence de nanoparticules, notamment la courbure de ses surfaces, affecte l’agrégation de molécules amphiphile ?2. Comment une bicouche de lipide, une forme d’agrégat particulier des amphiphile, peut induire l’assemblage auto-organisé de nanoparticules hydrophobes ?3. Est-ce que la présence des nanoparticules peut provoquer des transitions morphologiques d’un nanotube membranaire ? / Amphiphile molecules, endowed with a particular structure containing a hydrophilic head and a hydrophobic tail, have many important applications, e.g., fabrication of detergents, surface coating or surface functionalization, etc. Molecular aggregates of various forms, micelles, vehicle, membranes, etc. can be formed from amphiphile molecules. The complexity of these molecular aggregates involving a large number of atoms make the theoretical study of these system very challenging. Up to now, our understanding of the interaction between nanoparticles and aggregates of amphiphiles remains quite incomplete. Using a variety of molecular simulation methods and some theoretical approaches (Helfrich theory and perturbation theory), we have studied the following issues in the present thesis: 1. How the presence of nanoparticles, especially due to their highly curved surfaces, affects the aggregation of the amphiphiles? 2. How a lipid bilayer, a particular amphiphile aggregate, induces the self-assembly of hydrophobic nanoparticles.3. How the morphology transition of a membrane nanotube can be induced by nanoparticles?

La lipase pancréatique apparentée de type 2 du cobaye (GPLRP2) hydrolyse une grande variété de substrats lipidiques. Elle montre cependant une sélectivité selon l’organisation supramoléculaire du substrat et la présence de surfactants comme les sels biliaires (NaTDC). Nous avons utilisé la spectroscopie infrarouge (FTIR) pour étudier les interactions entres les phospholipides (DPPC), les surfactants et la GPLRP2 dans des conditions expérimentales proches de celles du tractus digestif. Pour étudier l’étape d’adsorption indépendamment de l’hydrolyse, un variant inactif de GPLRP2 (S152G) a été produit. Diverses dispersions aqueuses de phospholipides ont été préparées : des vésicules multilamellaires (MLV), unilamellaires (LUV) et des micelles mixtes DPPC-surfactant. GPLRP2 hydrolyse le DPPC présent dans des micelles mixtes DPPC-NaTDC mais n’a aucune activité sur le DPPC en phase lamellaire ou présent dans des micelles DPPC-Triton X100. L’analyse par FTIR de l’interaction de GPLRP2 S152G avec le système DPPC-NaTDC montre des changements importants dans le désordre conformationnel et la mobilité des chaînes acyles, la déshydratation de l’interface, l’orientation des têtes polaires et leurs liaisons hydrogène. Aucun effet n’est observé avec les MLV, les LUV ou le système DPPC-Triton X100. Il y a ainsi une reconnaissance spécifique du DPPC dans les micelles mixtes avec les sels biliaires, en accord avec l’activité enzymatique de GPLRP2. Les changements du spectre IR pendant l’hydrolyse du DPPC par la GPLRP2 ont été suivis. Certaines caractéristiques attribuées à la formation de produits de lipolyse peuvent être utilisées pour une étude quantitative de la lipolyse par FTIR. / Guinea pig pancreatic lipase-related protein type 2 (GPLRP2) hydrolyzes a large set of lipid substrates, but displays however some selectivity depending on the supramolecular structure of substrate and the presence of surfactants like bile salts (NaTDC). We used Fourier transform infrared (FTIR) spectroscopy to study the interactions between phospholipids (DPPC), surfactants and GPLRP2 under conditions close to those of the GI tract. To study the adsorption step independently from hydrolysis, a GPLRP2 inactive variant (S152G) was produced. Various phospholipid dispersions were prepared: multilamellar (MLV) and large unilamellar vesicles (LUV) and mixed micelles with surfactants. GPLRP2 was found to hydrolyze DPPC present in mixed DPPC-NaTDC micelles but was inactive on DPPC vesicles and DPPC-Triton X100 micelles. FTIR analysis of GPLRP2 S152G interaction with the DPPC-NaTDC system showed a decrease in the conformational disorder and mobility of the acyl chains, a dehydratation of the interface, and changes in the orientation and H-bonding of DPPC polar head-groups. These effects were not observed with MLV, LUV and DPPC-Triton X100 micelles, thus indicating a specific recognition of DPPC in mixed phospholipid-bile salt micelles, in agreement with phospholipase activity measurements. Changes in the IR spectra during DPPC hydrolysis by GPLRP2 were monitored. Specific spectral features were associated to the production of lipolysis products and could be used for quantifying phospholipid lipolysis by FTIR.

Animals rely on lipids as a major fuel for endurance exercise because they pack more joules per gram than any other fuel. However, in contrast to mammals, information on how the mobilization of lipids from endogenous stores is managed to meet the needs of energy metabolism in swimming fish is sparse. Information on in vivo rates of lipid mobilization in swimming fish has been limited to relatively low exercise intensities and has only been investigated in a single species. Therefore, the goal of my thesis was to address this paucity of information by quantifying lipolytic rate in rainbow trout during graded exercise and fatty acid mobilization in Atlantic salmon during prolonged endurance exercise. In the first part of my work, I hypothesized that like mammals, rainbow trout stimulate lipolysis above resting levels to a peak with increasing work intensity, but subsequently lower its rate at high intensities when ATP production from carbohydrates becomes dominant. To test this hypothesis, I measured the rate of appearance of glycerol (Ra glycerol) in the blood (resulting from the breakdown of triacylglycerol (TAG)) of trout at rest (control) and during graded exercise from rest to Ucrit. Results showed that Ra glycerol in trout averaged 1.24 ± 0.10 µmol kg -1 min-1 and that this rate was unaffected by exercise of any intensity. These experiments revealed that rainbow trout do not modulate lipolysis during exercise. Furthermore, I calculated that baseline lipolytic rate was much higher in trout than in mammals and that this rate is in constant excess of the requirements of energy metabolism. My second investigation focused on measuring fatty acid mobilization in Atlantic salmon. To date, the majority of studies on energy metabolism in salmonids have used rainbow trout as the ubiquitous model for salmonids. I postulated that domesticated rainbow trout may be far less impressive athletes than their wild anadromous form and other salmonids. In this regard, I proposed that studying energy metabolism in Atlantic salmon (even those from aquaculture) may help to deepen our understanding of the physiology of true long-distance migrant fish. To study the effects of prolonged endurance exercise on the mobilization of fatty acids from endogenous stores in these fish, I monitored the rate of appearance of fatty acids (Ra NEFA calculated from Ra Palmitate) in the blood during 72 hours of sustained swimming. I found that contrary to what has been previously described in rainbow trout, Ra Palmitate (and by proxy, Ra NEFA) is reduced by approximately 64% (from 0.75 ± 0.12 µmol kg-1min-1 to 0.27 ± 0.06 µmol kg-1min-1 and from 19.3 ± 7.8 µmol kg-1min-1 to 6.9 ± 2.0 µmol kg-1min-1 for Ra Palmitate and Ra NEFA, respectively) during prolonged endurance exercise in Atlantic salmon. However, like in trout, even this reduced rate of fatty acid mobilization exceeds the requirements of energy metabolism at rest and during swimming. While further experiments will be necessary, I speculated that this reduction in Ra NEFA may be caused by a partial inhibition of lipolysis to reduce the energetic cost of TAG:FA cycling and optimize fuel budgets during prolonged endurance exercise. This thesis provides the first in vivo measurements of lipolysis during graded exercise in salmonids and the first in vivo measurements of fatty acid mobilization in Atlantic salmon. From the results mentioned above, I concluded that salmonids mobilize lipids in constant excess of the requirements for energy metabolism, possibly to allow for rapid reorganization of membrane phospholipids in response to changing environmental conditions. However, more anadromous and migratory phenotypes may rely on a tighter control of lipolysis to minimize the costs of substrate cycling and conserve energy on limited fuel stores.

No description available.

Pentameric ligand-gated ion channels (pLGICs) are membrane-embedded receptors found extensively in pre- and post-synaptic membranes throughout the nervous system where they play an important role in neurotransmission. The function of the prototypic pLGIC, the nicotinic acetylcholine receptor (nAChR) is highly sensitive to changes in its lipid environment, while other pLGICs display varying lipid sensitivities. This thesis presents a multidisciplinary investigation into the features of the transmembrane domain (TMD) that determine the unique functional and physical traits of different pLGICs. Using two prokaryotic homologues of the nAChR, ELIC and GLIC, as models, I focus on the outermost, lipid-exposed α-helix, M4, which, despite being distant from the primary allosteric pathway coupling agonist binding to channel gating, exercises significant control over channel function. Here, I present evidence that M4 acts as a lipid sensor, detecting changes in the surrounding lipids and transmitting these changes to the channel pore via contacts with the adjacent TMD α-helices, M1 and M3, and/or with structures in the extracellular domain. Using ELIC and GLIC chimeras, I first show that the TMD is the main driver of pLGIC thermal stability. I then demonstrate that the M4 α-helices in each channel play different roles in channel maturation and function, which suggests a divergent evolutionary path. Following this, I show that the M4 C-terminus is essential to both maturation and function in GLIC, while in ELIC its role is less defined, again showcasing possible evolutionary differences. Building on these findings, I examined the role of aromatic residues at the M4 – M1/M3 interface, and found that they predictably determine the interactions between M4 and M1/M3. Notably, the addition of aromatic residues to enhance M4-M1/M3 interactions in ELIC promotes channel function, while the elimination of aromatic residues at the M4-M1/M3 interface in GLIC is detrimental to channel function. Furthermore, I show that these same aromatics alter the strength of pLGIC lipid sensing and the sensitivity to certain disease-causing mutations, both indicating that aromatic residues are key players in channel function, stability and modulation. Finally, I and my collaborators identified and characterized a novel desensitization-linked lipid binding site in ELIC. Extensive mutagenesis studies coupled with biophysical measurements allowed us to develop a model describing how lipid binding influences the rates of ELIC desensitization to shape the agonist-induced response.