Oral health related-quality of life before and during the COVID-19 pandemic in patients with non-alcoholic fatty liver disease.

BACKGROUND: Since the beginning of the COVID-19 pandemic, the number of medical appointments and the offer and use of oral health services have decreased sharply with the lockdown period. Restriction to regular dental care can increase the risk of oral diseases, capable of affecting general health and oral health-related quality of life, particularly among medically compromised patients. This study aimed to assess health-related quality of life (HRQoL) and oral health-related quality of life (OHRQoL) of patients with non-alcoholic liver disease (NAFLD) before and during the COVID-19 pandemic. MATERIAL AND METHODS: Prospective cohort of 58 patients with NAFLD followed up from March 2020 (before the pandemic) to December 2021 (during the pandemic). RAND 36-Item Health Survey and Oral Health Impact Profile 14 (OHIP-14) questionnaires were used to assess HRQoL and OHRQoL, respectively, in the two points of time. RESULTS: The scores of all scales HRQoL and of the question about health change in the last year decreased substantially with the advent of the pandemic. Large (>0.50) effect sizes were estimated for the scales Role functioning/physical, Pain, General health, and Energy/fatigue. Patients who had COVID-19 presented better HRQoL and OHIP-14 mean scores than those who did not have the disease. The OHIP-14 total score increased 3.6 points with the advent of the pandemic, representing a large effect size (0.62). Patients presented high probability (84.3%) of increasing OHIP14 score during the pandemic. CONCLUSIONS: The HRQoL and the OHRQoL scores of NAFLD patients decreased substantially with the advent of the pandemic. However, these decreases were not associated with the COVID-19 disease by itself, but probably to other factors related to the deep social changes brought by the social isolation measures to combat the pandemic.

Sitosterol and glucosylceramide cooperative transversal and lateral uneven distribution in plant membranes.

The properties of biomembranes depend on the presence, local structure and relative distribution assumed by the thousands of components it is made of. As for animal cells, plant membranes have been demonstrated to be organized in subdomains with different persistence lengths and times. In plant cells, sitosterol has been demonstrated to confer to phospholipid membranes a more ordered structure while among lipids, glycosphingolipids are claimed to form rafts where they tightly pack with sterols. Glucosylceramides are glycosphingolipids involved in plant signalling and are essential for viability of cells and whole plant. The glucosylceramide-sitosterol structural coupling within PLPC membranes is here investigated by Langmuir films, in silico simulations and neutron reflectometry, unveiling that a strong direct interaction between the two molecules exists and governs their lateral and transversal distribution within membrane leaflets. The understanding of the driving forces governing specific molecules clustering and segregation in subdomains, such as glucosylceramide and sitosterol, have an impact on the mechanical properties of biomembranes and could reflect in the other membrane molecules partitioning and activity.

Amphiphilic azobenzenes: Antibacterial activities and biophysical investigation of their interaction with bacterial membrane lipids.

With the emergence of multi-drug resistant bacteria and hospital-acquired infections, there is an urgent need to develop new antibiotics. Here, we report the synthesis, physico-chemical characterizations, and antimicrobial activity assays of four Azo compounds that differ in their alkyl chain length. The molecular mechanism of their antibacterial activity was investigated by complementary in vitro and in silico biophysical studies. The compounds with alkyl chain lengths of four or six carbons showed a low MIC50 against Escherichia coli and Bacillus subtilis. Our investigations into the mechanism of their action revealed that phosphatidylethanolamine in the bacterial plasma membrane plays an important role in their antibacterial activity.

Socio-demographic characteristics are related to the advanced clinical stage of oral cancer.

BACKGROUND: Social determinants may be associated with the onset and progression of the clinical stage of oral cancer. AIM: To evaluate the impact of socio-demographic characteristics on the prevalence of advanced clinical stage of oral cancer. MATERIAL AND METHODS: Information about 51,116 cases of oral cancer, from all Brazilian states, between 2000 and 2012, was obtained from the Cancer Registry Information System. The clinical stage of oral cancer (dependent variable) was classified as initial (stages I and II) or advanced (stages III and IV). The relationship between the clinical stage of oral cancer and the following independent variables was analyzed: sex, age, schooling, marital status, family history of cancer, and origin of referral. Analyses on frequency distribution and multivariate binary logistic regression model were performed (α<0.05). RESULTS: Compared to individuals with no schooling, those who attended elementary to high school (OR=2.461) and college education (OR = 3.050) had a higher prevalence of advanced cases of oral cancer. Individuals without a partner (OR = 14,209) demonstrated a higher prevalence compared to married individuals. Subjects aged 20-44 years (OR = 4.081) and 45-64 years (OR = 14.875) had a higher prevalence compared to those aged 15-19 years. The variables gender, family history of cancer and origin of referral integrated the binary model of logistic regression, but did not present statistical significance. CONCLUSIONS: Socioeconomic factors may be related to the advanced clinical stage of oral cancer.

Quality of life, work ability and oral health among patients with chronic liver diseases.

BACKGROUND: This study aimed to explore the associations between health-related quality of life and work ability with the oral health status of patients with chronic liver disease. MATERIAL AND METHODS: A cross-sectional study included 150 patients with chronic liver disease, consecutively seen at University Hospital, Salvador, Brazil. Oral health was evaluated by the Decayed, Missing, and Filled Teeth (DMFT) index and by the presence of gingivitis and periodontitis. Salivary flow was "reduced" when <1.0 mL/min. Health-related quality of life was evaluated by using the 36-Item Short Form Health Survey questionnaire (SF-36); work ability was evaluated by the Work Ability Index questionnaire. RESULTS: All health-related quality of life indicators were systematically lower among the 99 patients with reduced salivary flow than among the 51 patients with normal salivary flow. Physical Functioning, Role-Physical, and Physical Component Summary scores were strongly correlated (P < 0.005 or less) with the number of Missing Teeth and with DMFT index. Reduced salivary flow was associated (P < 0.05) with poor work ability. Patients with poor or moderate work ability presented higher (P < 0.001) means of the DMFT index than those with good or excellent work ability. CONCLUSIONS: Patients with chronic liver disease who present poor oral health presented low health-related quality of life and poor work ability. These findings reinforce the need of these patients for specialized stomatological care.

Cognitive and anxiety-like impairments accompanied by serotonergic ultrastructural and immunohistochemical alterations in early stages of parkinsonism.

Parkinson's disease (PD) is mostly known as a dopamine deficiency syndrome due the structural and functional changes in striatal projection neurons. However, studies have considered this pathology as a multi-systemic disease in which the neurodegenerative process extends beyond the dopaminergic system. Therefore, the purpose of the present study was to investigate the morphological and immunohistochemical changes associated with behavioral and cognitive alterations in a model of parkinsonism induced by low dose of reserpine. Animals showed anxiety-like behavior and deficits in short-term recognition memory. Besides, Tyrosine Hydroxylase (TH) immunoreactive cells decreased in reserpine (RES) group in CA1 and serotonin (5-HT) immunoreactive cells decreased in RES group in CA1, CA3 and medial prefrontal cortex (mPFC). Moreover, an increase in the area (µm2) of 5 H T labeled ultrastructure (axon terminal) was observed in RES group only in CA1 and mPFC. The evidence of alterations in 5-HT immunoreactive in the premotor phase of model of parkinsonism highlights the importance of looking beyond the nigrostriatal system to elucidate the underling mechanisms and deficits in other neurotransmitters systems. This provides vital information regarding novel interventions for the management of non-motor symptoms. Additionally, the low-dose reserpine treatment has an early effect on axonal ultrastructure. As the axonopathy in PD has been increasingly recognized, the focus on axonal neurobiology is noteworthy for both neuroprotective and restorative therapeutics, and the progressive reserpine rat model can be a useful tool in this search.

Availability of global health opportunities in North American Paediatric Orthopaedic Fellowship Programmes.

PURPOSE: Orthopaedic residents are increasingly seeking international health electives (IHEs) during training, many of which involve providing paediatric orthopaedic care. However, little is known about the availability of IHEs during orthopaedic fellowship training. Our study sought to assess the global health opportunities available to North American paediatric orthopaedic fellows. METHODS: We conducted an online, REDCap-based survey of paediatric orthopaedic fellowship programme directors (PDs) in the United States and Canada. The survey link was sent by the Pediatric Orthopaedic Society of North America (POSNA) Evidence-Based Medicine Committee to all POSNA-approved paediatric orthopaedic fellowship PDs. Follow-up reminder emails were delivered at set time intervals. RESULTS: The overall response rate was 55% (26/47). Only three of 26 responding programmes (11.5%) offered a structured global health programme but 42.3% of programmes (11/26) reported fellow IHE participation within the last ten years. In all, 91% of PDs reported that fellows were extremely satisfied with their IHE, and 91% agreed that IHEs are valuable for trainees. Perceived barriers to fellow participation in IHEs included lack of funding, lack of established partner sites, lack of interest among fellows and concerns related to time away compromising clinical/call coverage. In all, 65.4% of PDs agree that IHE participation during training plays a major role in shaping fellows' future volunteer activities. CONCLUSION: There are limited global health opportunities among North American paediatric orthopaedic fellowship programmes, with only 11.5% offering a structured global health programme. Greater efforts to establish sustainable funding and international partnerships may increase opportunities for IHEs during paediatric orthopaedic fellowship training. LEVEL OF EVIDENCE: Level II.

Oral Health and Quality of Life in Candidates for Liver Transplantation.

BACKGROUND: There is a gap in the scientific literature about the association between oral health and the health-related quality of life of patients on the liver transplantation waiting list. The aim of this work was to describe aspects of oral health and quality of life of patients on a liver transplantation waiting list. METHODS: This was a cross-sectional study among 116 patients with chronic hepatic disease: 29 on a liver transplantation waiting list (Model for End-Stage Liver Disease score ≥15) and 87 under monitoring in a gastroenterology service in a Brazilian university hospital. Oral health was evaluated according to criteria recommended by the World Health Organization and by the European Association of Dental Public Health. Health-related quality of life was evaluated by means of the 36-Item Short-Form Health Survey (SF-36). RESULTS: Patients on the liver transplantation waiting list presented poorer health-related quality of life than those who were not on the list in the domains physical functioning, role physical, bodily pain, general health perceptions, and social functioning and in the physical component summary. Periodontitis affected 72.4% of the patients on the liver transplantation waiting list, but only 27.6% of the patients not on that list. Reduced salivary flow was associated with poorer mental health component summary in hepatitis C patients. CONCLUSIONS: Patients on the liver transplantation waiting list presented poorer health-related quality of life than those who were not on the list, mainly in the indicators concerning physical health, as well as higher frequencies of decayed teeth and periodontitis. The mental health component summary was associated with reduced salivary flow in hepatitis C patients.

Atrophic Maxilla Reconstruction With Fresh Frozen Allograft Bone, Titanium Mesh, and Platelet-Rich Fibrin: Case Report.

The purpose of this article was to report the clinical and radiographic findings about a case of a man affected by severely atrophic maxilla to demonstrate the clinical proceedings associated with alveolar reconstruction destined for dental implant rehabilitation. The 3-dimensional augmentation of the alveolar ridge with the use of fresh-frozen bone graft, platelet-rich fibrin membrane, and titanium mesh suggests potential benefits to the development of the bone formation physiology. The treatment combination may result in an optimal prognosis and represents an option for reconstruction of bone defects. At 8 months after surgery, no evidence of complications was observed; the clinical examination and computerized tomographic scan revealed bone formation and installed implant stability.

Molecular dynamics study of micelles properties according to their size.

Surfactants are molecules able to spontaneously self-assemble to form aggregates with well-defined properties, such as spherical micelles, planar bilayers, cylindrical micelles or vesicles. Micelles have notably several applications in many domains, such as drug delivery or membrane protein solubilization. In this context, the study of micelle formation in relation with the structural and physico-chemical properties of surfactants is of great interest to better control their use in the different application fields. In this work, we use the MD approach developed by Yoshii et al. and extend it to surfactants with different structures. We aim to systematically investigate different micellar properties as a function of the aggregates size by a molecular dynamics approach, to get an insight into the micellar organization and to collect some relevant descriptors about micelle formation. For this, we perform short MD simulations of preformed micelles of various sizes and analyze three parameters for each micelle size, namely the eccentricity of the micelles, the hydrophobic/hydrophilic surface ratio and the hydrophobic tails hydration. If these parameters are known descriptors of micelles, they were not yet studied in this way by MD. We show that eccentricity, used as "validator" parameter, exhibits minimal values when the aggregate size is close to the experimental aggregation number for surfactants that are known to form spherical micelles. This hence indicates that our methodology gives consistent results. The evolution of the two descriptors follows another scheme, with a sharp increase and decrease, respectively, followed by a leveling-off. The aggregate sizes at which this stabilization starts to occur are close to the respective aggregation number of each surfactant. In our approach, we validate the use of these descriptors to follow micelle formation by MD, from "simple" surfactants to more complex structures, like lipopeptides. Our calculations also suggest that some peculiar behavior, like that of TPC, can be highlighted by our approach. In the context of peptidic surfactants, our methodology could further help to improve computer simulations combined to molecular thermodynamic models to predict micellar properties of those more complex amphiphilic molecules.

Proteinograma sérico de éguas com placentite ascendente e seus respectivos neonatos: dados preliminares / Serum protein concentrationin mares with ascending placentitis and their newborns: preliminary data

Este estudo teve por objetivo estabelecer o proteinograma sérico em éguas com placentite induzida e em seus respectivos neonatos. Foram coletadas amostras de sangue das éguas em oito momentos diferentes e dos potros em quatro momentos. Para obtenção da concentração das frações proteicas, utilizou-se eletroforese em gel de acrilaminada contendo dodecil sulfato de sódio (SDS-PAGE). No método utilizado, foram observadas 23 bandas proteicas, cujos pesos moleculares variaram de 16KDa a 245KDa, sendo possível a identificação das seguintes frações: 175KDa, 102KDa, 83KDa, 63KDa, 50KDa, 41KDa, 39KDa e 28KDa. De todas as bandas proteicas encontradas, somente as de 39KDa e 41KDa apresentaram alteração na cinética nos momentos avaliados. De acordo com a solução marcadora, pode-se sugerir que essas proteínas seriam alfa1-glicoproteína ácida (39KDa) e haptoglobina (41KDa). A concentração de imunoglobulinas nos potros apresentou aumento significativo a partir das 12 horas de nascimento. Não está elucidado se estes níveis refletem a persistência do processo inflamatório placentário ou se são alterações fisiológicas do periparto. Não foram observadas alterações na cinética das proteínas nos potros nas primeiras 48 horas.(AU)

The aim of this paper was to identify the serum acute phase protein concentration in mares with induced placentitis and their neonates. Blood samples were collected from the mares in 8 different moments, and from the foals, in 4 moments. To obtain the concentration of protein fractions acrilaminada gel electrophoresis in sodium dodecyl sulfate (SDS-PAGE) was used. In the used method 23 protein bands whose molecular weights ranged from 16kDa to 245kDa were observed, it is possible to identify the following fractions: 175kDa, 102kDa, 83kDa, 63kDa, 50kDa, 41kDa, 39kDa and 28kDa. Of all the protein bands found only the 39KDa and 41KDa have changes in the kinetics in the evaluated times. According to the marker solution, we would suggest that these proteins are alfa1-acid glycoprotein (39kDa) and haptoglobin (41kDa). The concentration of immunoglobulins in foals increased significantly from 12 hours of birth.(AU)

Effects of simvastatin/ezetimibe on microparticles, endothelial progenitor cells and platelet aggregation in subjects with coronary heart disease under antiplatelet therapy

It is not known whether the addition of ezetimibe to statins adds cardiovascular protection beyond the expected changes in lipid levels. Subjects with coronary heart disease were treated with four consecutive 1-week courses of therapy (T) and evaluations. The courses were: T1, 100 mg aspirin alone; T2, 100 mg aspirin and 40 mg simvastatin/10 mg ezetimibe; T3, 40 mg simvastatin/10 mg ezetimibe, and 75 mg clopidogrel (300 mg initial loading dose); T4, 75 mg clopidogrel alone. Platelet aggregation was examined in whole blood. Endothelial microparticles (CD51), platelet microparticles (CD42/CD31), and endothelial progenitor cells (CD34/CD133; CDKDR/CD133, or CD34/KDR) were quantified by flow cytometry. Endothelial function was examined by flow-mediated dilation. Comparisons between therapies revealed differences in lipids (T2 and T3<T1 and T4 for total cholesterol, LDL-C, and triglycerides; P<0.002 for all), as well as for endothelial function (T2>T1 and T4, P=0.001). Decreased platelet aggregation was observed after aspirin (arachidonic acid, T1<T3 and T4, P=0.034) and clopidogrel (adenosine, T3 and T4<T1 and T2, P<0.0001) therapy. Simvastatin/ezetimibe diphosphate did not change platelet aggregation, the amount of circulating endothelial and platelet microparticles, or endothelial progenitor cells. Cardiovascular protection following therapy with simvastatin/ezetimibe seems restricted to lipid changes and improvement of endothelial function not affecting the release of microparticles, mobilization of endothelial progenitor cells or decreased platelet aggregation.

Effects of simvastatin/ezetimibe on microparticles, endothelial progenitor cells and platelet aggregation in subjects with coronary heart disease under antiplatelet therapy.

It is not known whether the addition of ezetimibe to statins adds cardiovascular protection beyond the expected changes in lipid levels. Subjects with coronary heart disease were treated with four consecutive 1-week courses of therapy (T) and evaluations. The courses were: T1, 100 mg aspirin alone; T2, 100 mg aspirin and 40 mg simvastatin/10 mg ezetimibe; T3, 40 mg simvastatin/10 mg ezetimibe, and 75 mg clopidogrel (300 mg initial loading dose); T4, 75 mg clopidogrel alone. Platelet aggregation was examined in whole blood. Endothelial microparticles (CD51), platelet microparticles (CD42/CD31), and endothelial progenitor cells (CD34/CD133; CDKDR/CD133, or CD34/KDR) were quantified by flow cytometry. Endothelial function was examined by flow-mediated dilation. Comparisons between therapies revealed differences in lipids (T2 and T3T1 and T4, P=0.001). Decreased platelet aggregation was observed after aspirin (arachidonic acid, T1

Resposta clínica e metabólica de potros neonatos em relação aos achados histopatológicos da placenta na égua / Clinical and metabolic response of neonatal foals related to histopathology finds in mare placenta

Avaliaram-se as respostas clínica e metabólica de potros neonatos em relação aos achados histopatológicos da placenta na égua. Foram avaliados dois grupos de éguas da raça Puro Sangue Inglês - um grupo-problema (n=25) e um grupo-controle (n=25), de acordo com os achados da placenta. O exame dos potros constou de avaliação clínica geral, hematologia e bioquímica sérica. O exame histopatológico da placenta apresentou resultado compatível com a apresentação clínica do potro, sendo que a presença de lesões inflamatórias resultou na produção de potros debilitados. A presença de lesões degenerativas não comprometeu o estado clínico do neonato, mas pode ser responsável pela manifestação de distúrbios subclínicos, evidenciados pelo aumento das taxas de AST e GGT. A ureia pareceu ser um indicador de dano renal decorrente de insuficiência placentária em potros neonatos.

The placenta represents the major communication between the mare and the fetus during the gestational period, and this suggests that any disturbance in the placenta can be an indicator of gestational damage with risk to the fetus. The aim of this paper was to evaluate the clinical and metabolic responses of the newborn foals related with the findings from the histopathological examination of the placenta. This study was conducted in a farm located in Bagé-RS, Brazil, where were evaluated two groups of Throughbred mares for this case-control study: One Problem Group (N=25) and the Control Group (n=25), based on the placental findings. The foal's evaluation was based on general clinical examination, hematology and serum biochemistry. Results from the placenta histopathological exams were compatible with clinical presentation of the foals, with the presence of inflammatory lesions resulting in the production of debilitated foals. The presence of degenerative lesions in the placenta does not compromise the clinical features of the newborn, but they can be responsible for the manifestation of sub-clinical disturbances, evidenced by increased levels of AST and GGT. Urea seems to be an indicator of renal damage due to placental insufficiency in neonatal foals.

Interaction of hexadecylbetainate chloride with biological relevant lipids.

The present work investigates the interaction of hexadecylbetainate chloride (C(16)BC), a glycine betaine-based ester with palmitoyl-oleoyl-phosphatidylcholine (POPC), sphingomyelin (SM), and cholesterol (CHOL), three biological relevant lipids present in the outer leaflet of the mammalian plasma membrane. The binding affinity and the mixing behavior between the lipids and C(16)BC are discussed based on experimental (isothermal titration calorimetry (ITC) and Langmuir film balance) and molecular modeling studies. The results show that the interaction between C(16)BC and each lipid is thermodynamically favorable and does not affect the integrity of the lipid vesicles. The primary adsorption of C(16)BC into the lipid film is mainly governed by a hydrophobic effect. Once C(16)BC is inserted in the lipid film, the polar component of the interaction energy between C(16)BC and the lipid becomes predominant. Presence of CHOL increases the affinity of C(16)BC for membrane. This result can be explained by the optimal matching between C(16)BC and CHOL within the film rather by a change of membrane fluidity due to the presence of CHOL. The interaction between C(16)BC and SM is also favorable and gives rise to highly stable monolayers probably due to hydrogen bonds between their hydrophilic groups. The interaction of C(16)BC with POPC is less favorable but does not destabilize the mixed monolayer from a thermodynamic point of view. Interestingly, for all the monolayers investigated, the exclusion surface pressures are above the presumed lateral pressure of the plasma membranes suggesting that C(16)BC would be able to penetrate into mammalian plasma membranes in vivo. These results may serve as a useful basis in understanding the interaction of C(16)BC with real membranes.

Oral health profile of cirrhotic patients awaiting liver transplantation in the Brazilian Northeast.

BACKGROUND: Infections are a frequent cause of morbidity and mortality among postoperative liver transplant (OLT) patients and a leading cause of decompensated chronic liver disease (CLD) among patients awaiting the procedure. Oral lesions that are frequently observed in subjects with CLD may represent foci for systemic infections before and after OLT. AIMS: To evaluate the oral health profile of patients with CLD awaiting OLT. METHODS: One hundred thirty one patients including 100 males of overall mean age 49.5 ± 10.8 years with CLD were listed for OLT and examined for oral health status according to a established protocol. RESULTS: One hundred thirty (99%) patients were partially edentulous; 66 (51%) had chewing difficulties; and 63 (48%) experienced reduced salivary flow. With respect to periodontal disease and oral infections, 68 (25%) had periodontitis, 63 (48%) had periapical lesion, 64 (49%) had abscesses, and 59 (45%) had root fragments. Loss of follow-up was observed in 21 subjects. Among the 110 other patients, 63 (57%) underwent dental treatments with complications in only two cases. Interestingly, mortality was significantly lower among treated (31%) versus nontreated patient (79%; P<.001). CONCLUSIONS: Poor oral health status observed in most CLD patients may represent a source of systemic infections before and after OLT. Treatment of such lesions was feasible in the majority of the patients and seemed to be associated with a reduction in mortality.

Osteodistrofia fibrosa em equinos criados em pastagem de Panicum maximum cultivar Aruana: relato de casos / Fibrous osteodystrophy in horses raised on Aruana (Panicum maximum) pasture: case reports

Relata-se a ocorrência de osteodistrofia fibrosa em 38 equinos criados em pastagens de Panicum maximum cultivar Aruana, da raça Mangalarga Marchador, provenientes de uma propriedade localizada no estado do Paraná. No exame clínico geral, observou-se aumento bilateral e simétrico dos ossos da face e, também, aumento de volume na porção distal do rádio. A análise radiológica das áreas afetadas demonstrou redução da densidade óssea, e, na bioquímica sanguínea, 24 (63 por cento) animais apresentaram níveis de fósforo elevados. O exame bromatológico revelou níveis elevados de oxalato na pastagem de Aruana. Conclui-se que a ingestão de Aruana, forragem com altos níveis de oxalato, foi responsável pelo aparecimento de lesões de osteodistrofia fibrosa em equinos.

Fibrous osteodystrophy occurrence is reported in 38 Mangalarga Marchador horses raised on Aruana (Panicum maximum) pasture from a breeding farm in Paraná state. Clinical examination showed bilateral and symmetric increase in bones of face and an increase of volume at the radius distal portion. The radiologic analysis revealed bone density reduction in affected areas. Blood biochemist demonstrated high phosphorus levels in 24 animals (63 percent). Analysis of the pasture was performed and high levels of oxalate were found in the Aruana samples. It was concluded that the ingestion of Aruana, a pasture with high oxalate levels, was responsible for the appearing of fibrous osteodystrophy lesions in horses.

Study of the specific lipid binding properties of Abeta 11-22 fragment at endosomal pH.

Increasing evidence implicates interactions between Abeta peptide and lipids in the development of Alzheimer's disease. More generally, Abeta peptide interactions with membranes seem to depend on the composition of the lipid bilayer and the structural features of the peptide. One key parameter should be pH, since one site of intracellular Abeta peptide production and/or accumulation is likely to be endosomes. This intracellular endosomal accumulation was suggested to contribute to disease progression. In this paper, we report a study on the 11-22 amphiphilic domain of Abeta in interaction with model membrane; this region contains most of the charged residues of the N-terminal domain of Abeta. We show that the peptide charge, and more precisely the protonation state of histidines 13 and/or 14, is important for the interaction with lipids. Hence, it is only at endosomal pH that a conformational change of the peptide is observed in the presence of negatively charged lipid vesicles, that is, when both lipid headgroups and histidines can interact through electrostatic interactions. Specific interactions of the fragment with phosphatidylserine and to a lesser extent with phosphatidylcholine, but not phosphatidylethanolamine, are further evidenced by the Langmuir monolayer technique. From our results, we suggest that the protonation state of His residues could have a role in the pathogenic surface interaction of the whole Abeta peptide with membranes.

The "Tilted Peptide Theory" links membrane insertion properties and fusogenicity of viral fusion peptides.

Class I fusion glycoproteins of viruses are involved in the fusion between viral envelope and cell membrane. A region located in the N-terminal domain of these glycoproteins, called the fusion peptide, is essential for fusion. Fusion peptides are able to induce by themselves in vitro membrane fusion. In this paper, we review the properties of those peptides related to their fusogenicity, in particular the correlation existing between their ability to insert obliquely in membranes and fusogenicity. This relation notably allows predicting successfully the minimal region of some fusion peptides sufficient to induce significant in vitro fusion. The notion of obliquity and fusogenicity is discussed in terms of the existing proposed mechanisms for viral fusion.

Study of Thermomyces lanuginosa lipase in the presence of tributyrylglycerol and water.

The Thermomyces lanuginosa lipase has been extensively studied in industrial and biotechnological research because of its potential for triacylglycerol transformation. This protein is known to catalyze both hydrolysis at high water contents and transesterification in quasi-anhydrous conditions. Here, we investigated the Thermomyces lanuginosa lipase structure in solution in the presence of a tributyrin aggregate using 30 ns molecular-dynamics simulations. The water content of the active-site groove was modified between the runs to focus on the protein-water molecule interactions and their implications for protein structure and protein-lipid interactions. The simulations confirmed the high plasticity of the lid fragment and showed that lipid molecules also bind to a secondary pocket beside the lid. Together, these results strongly suggest that the lid plays a role in the anchoring of the protein to the aggregate. The simulations also revealed the existence of a polar channel that connects the active-site groove to the outside solvent. At the inner extremity of this channel, a tyrosine makes hydrogen bonds with residues interacting with the catalytic triad. This system could function as a pipe (polar channel) controlled by a valve (the tyrosine) that could regulate the water content of the active site.