Effects of artepillin C on model membranes displaying liquid immiscibility

It has been hypothesized that the therapeutic effects of artepillin C, a natural compound derived from Brazilian green propolis, are likely related to its partition in the lipid bilayer component of biological membranes. To test this hypothesis, we investigated the effects of the major compound of green propolis, artepillin C, on model membranes (small and giant unilamelar vesicles) composed of ternary lipid mixtures containing cholesterol, which display liquid-ordered (lo) and liquid-disordered (ld) phase coexistence. Specifically, we explored potential changes in relevant membrane parameters upon addition of artepillin C presenting both neutral and deprotonated states by means of small angle X-ray scattering (SAXS), differential scanning calorimetry (DSC), and confocal and multiphoton excitation fluorescence microscopy. Thermotropic analysis obtained from DSC experiments indicated a loss in the lipid cooperativity of lo phase at equilibrium conditions, while at similar conditions spontaneous formation of unilamellar vesicles from SAXS experiments showed that deprotonated artepillin C preferentially located at the surface of the membrane. Time-resolved experiments using fluorescence microscopy showed that at doses above 100 µM, artepillin C in its neutral state interacted with both liquid-ordered and liquid-disordered phases, inducing curvature stress and promoting dehydration at the membrane interface.

Physical inactivity and anthropometric measures in schoolchildren from Paranavaí, Paraná, Brazil / Inatividade física e medidas antropométricas em escolares de Paranavaí, Paraná, Brasil

OBJECTIVE: To investigate the association between physical inactivity and anthropometric measures in schoolchildren from Paranavaí-Parana, Brazil. METHODS: Cross-sectional survey, carried out in July and August 2013. Sample of 566 students (287 boys and 279 girls) from 6th to 9th grade, aged 10 to 14 years, from public and private schools of Paranavaí - PR, Southern Brazil. The variables analyzed were: time of weekly physical activity through a questionnaire (physical inactivity <300 minutes/week), body mass index (BMI) and waist circumference (WC). In the statistical analysis, the U Mann-Whitney and Student's t tests were used for comparison between genders. To identify factors associated with insufficient levels of physical activity, univariate and multivariate logistic regression analysis was applied and expressed in Odds ratio (OR) and 95% confidence interval (95%CI). RESULTS: There was an association between physical inactivity and anthropometric measurements for BMI (p<0.001) and WC (p<0.001), with a prevalence rate of 56.1% and 52.7% of inactive adolescents, respectively. In the multivariate analysis, there was significant association of physical inactivity and overweight (OR 1.8, 95%CI: 1.1-3.0) and with increased waist circumference (OR 2.8, 95%CI: 1.4-3.8). CONCLUSIONS: Inadequate levels of physical activity is a determining factor for overweight and abdominal adiposity. Accordingly, preventive measures should be taken, especially in schools, emphasizing the importance of exercise for body composition control and weight reduction. .

OBJETIVO: Investigar a associação entre a inatividade física e medidas antropométricas em escolares de Paranavaí, Paraná, Brasil. MÉTODOS: Pesquisa com delineamento transversal, feita em julho e agosto de 2013. Amostra composta por 566 escolares (287 meninos e 278 meninas), de 10 a 14 anos, do 6° ao 9° ano da rede pública e privada de Paranavaí (PR). As variáveis analisadas foram: tempo de atividade física semanal, por meio de questionário (inatividade física: < 300 min/semanal), índice de massa corporal (IMC) e circunferência de cintura (CC). Na análise estatística foram usados os testes U de Mann-Whitney e t de Student para comparar os sexos. Para verificar os fatores associados ao nível insuficiente de atividade física aplicou-se o modelo de regressão logística binária univariada e multivariada, expressa em odds ratio (OR), e intervalo de confiança de 95% (IC95%). RESULTADOS: Houve associação entre inatividade física e as medidas antropométricas para IMC (p<0,001) e CC (p<0,001), com prevalências de 56,1% e 52,7% de inativos, respectivamente. Na análise multivariada, foram observadas associações significativas de inatividade física nos alunos que apresentaram excesso de peso (OR 1,8; IC95%: 1,1-3,0) e circunferência de cintura aumentada (OR 2,2; IC95%: 1,4-3,8). CONCLUSÕES: Nível inadequado de atividade física é fator determinante no excesso de peso e na adiposidade abdominal. Nesse sentido, medidas preventivas devem ser tomadas, principalmente nas escolas, e enfatizar-se a importância do exercício físico no controle da composição corporal e redução do pesoe. .

Hairy Polyp of the Supratonsillar Fossa Causing Intermittent Airway Obstruction

Introduction Dermoids frequently called "hairy polyps" and their nature have not been completely clarified. Objectives To discuss the unusual presentation, symptoms, incidence, histology, and perioperative management of hairy polyps in the light of a case and current literature. Resumed Report A 3-year-old boy presented with intermittent respiratory distress since birth. Oropharyngeal examination revealed a nasopharyngeal mass originating from the supratonsillar fossa. The mass was so mobile that it moved between the oropharynx and the nasopharynx during swallowing. The radiologic and pathologic examinations confirmed the mass as a hairy polyp. Conclusion In a pediatric age group with airway obstruction, hairy polyps of the oropharyngeal region must also be included in the differential diagnosis. .

MAPS: An interactive web server for membrane annotation of transmembrane protein structures.

The exact positioning of the membrane in transmembrane (TM) proteins plays important functional roles. Yet, the structures of TM proteins in protein data bank (pdb) have no information about the explicit position of the membrane. Using a simple hydrophobic lipid-protein mismatch energy function and a flexible lipid/water boundary, the position of lipid bilayer for representative TM proteins in pdb have been annotated. A web server called MAPS (Membrane Annotation of Protein Structures; available at: http://www.boseinst.ernet.in/gautam/maps) has been set up that allows the user to interactively analyze membrane-protein orientations of any uploaded pdb structure with user-defined membrane flexibility parameters.

The effect of hydrostatic pressure on membrane-bound proteins

Many cellular proteins are bound to the surfaces of membranes and participate in various cell signaling responses. Interactions between this group of proteins are in part controlled by the membrane surface to which the proteins are bound. This review focuses on the effects of pressure on membrane-associated proteins. Initially, the effect of pressure on membrane surfaces and how pressure may perturb the membrane binding of proteins is discussed. Next, the effect of pressure on the activity and lateral association of proteins is considered. We then discuss how pressure can be used to gain insight into these types of proteins.

A new membrane probing steroidal spin label: synthesis and applications.

The applicability of a new steroidal spin label, 3-oxo-androstan-17 beta-yl-(2",2",6",6"-tetramethyl-N-oxyl) piperidyl butan-1',4'-dioate, in studying the phase transition properties of model membrane L-alpha-dipalmitoyl phosphatidyl choline (DPPC) in the presence and absence of drugs has been explored. Its synthesis and characterization has been described herein. Besides, the localization of this spin label in lipid liposomes has been studied using electron spin resonance (ESR), differential scanning calorimetry (DSC) and 1H and 31P NMR spectroscopic techniques. The label has also been used to study the permeability of epinephrine into membrane. The results show that the spin label has a good potential as a spin probe in the study of biomembranes.

Insight into the environment of tryptophan in a hydrophobic model peptide upon aggregation and interaction with lipid vesicles: a steady state and time resolved fluorescence study.

Fluorescence spectroscopy is extensively used to monitor binding of peptides to lipid vesicles as well as orientation in the lipid bilayer. In steady-state fluorescence, the emission characteristics of intrinsic and extrinsic fluorophores, which are sensitive to environment are monitored. Life time measurements should yield useful information about the location and flexibility of fluorophores, as these factors have a significant effect on the life times. However, studies on protein structure and dynamics indicate that interpretation of life-time data is complicated (Beechem. J.M. and Brand, L. (1985) Annu. Rev. Biochem. 54, 43-71). Hence, simple well-defined systems should help in interpretation of life time data, especially in lipid-peptide interactions. In order to examine how fluorescence characteristics of tryptophan and anthroyl group would reflect molecular details of peptide aggregation and lipid-peptide interaction, studies have been carried out on a model hydrophobic peptide and its fatty acylated derivative. Steady-state fluorescence measurements suggest that: (1) the fatty acyl chain attached to an amino acid associates with the peptide chain in aqueous environment. (2) In the lipid bilayer, the acyl chain is oriented perpendicular to the lipid bilayer surface with the peptide chain at an angle to it. Analysis of the fluorescence decay of tryptophan indicates the predominance of a very short life-time component (<1ns) in aqueous environment and lipid-vesicles. Since the preexponentials were not negative, it is unlikely that this is due to extensive deactivation process. We attribute the observation of the low life time component to predominance of one rotamer around (C alpha-C beta)bond of tryptophan in aqueous and lipid environments. Our investigations suggest that fluorescence life time data need to be complemented with steady state measurements to get an insight into details of lipid-peptide interaction.

Molecular dynamics simulation of hydrated phospholipid bilayers.

Understanding of microscopic behaviour of biological membrane is crucial for designing of molecules to control transport properties of the membranes. Phospholipid-water forms a good model system to study ligand induced structural and dynamical changes in membrane. The review has its main focus on molecular dynamics (MD) simulation of phospholipid bilayers. A brief summary of the current status of structure of phospholipid membranes based on different physico-chemical measurements is given. We discuss here mainly results of MD simulations in the recent years on hydrated phospholipid bilayers and their interaction with ligands. Simulation parameters as: choice of initial system, force fields, protocols for simulation are compared. Main results on: order parameter, head group and chain conformation, water penetration profile, chain tilts, pair-correlation function between atoms of lipid and water, diffusion of ions and ligands are discussed. The review gives application and limitation of MD method for studying lipid water system.

Gramicidin channels--a solvable membrane "protein" folding problem.

The linear gramicidins are peptide antibiotics that form cation-selective channels in lipid bilayers. Gramicidin channels have very well-defined functional characteristics, and the structure of membrane-spanning gramicidin A channels is known at atomic resolution. These features make the gramicidins well suited to study how the amino acid sequence encodes the structure and function of a membrane-spanning channel. We show how one can use electrophysiological measurements to obtain structural information about conducting channels and to quantify the conformational preferences of sequence-substituted gramicidin mutants.

Acylation of proteins: recent advances.

The biochemistry and cell biology of covalent attachment of the fatty acids palmitic and myristic to proteins has been the subject of extensive investigations during the past fifteen years. While the site of attachment of fatty acids and the primary structure of proteins around the acylation site have been extensively documented, the exact role of the fatty acids have only been speculated upon. Since fatty acids would prefer to be associated with the lipid bilayer of membranes, it has been assumed that the role of the fatty acid is to provide a stable membrane anchor. This review discusses recent reports in the area of fatty acylation which suggests roles for the fatty acid other than that of a stable membrane anchor.

Molecular and physicochemical aspects of local anesthetic-membrane interaction

Local anesthesia is achieved by the binding of anesthetic molecules to the sodium channel, a membrane protein responsible for the transport of the extracellular sodium to the cytosol. Local anesthetics (LA) bind to the sodium channel inhibiting sodium transport and, as a consequence, the action potential responsible for the nervous impulse. Most LA are relatively hydrophobic ionizable amines that undergo partitioning into lipid. Both activity and toxicity correlate positively with LA hydrophobicity. Effects of LA on the structural and dynamical properties of the membranes lipid region may be responsible for some of the toxic effects caused by these molecules. The present review focuses on research done on the interaction between both the charged and uncharged forms of LA and lipid systems - bilayers and micelles. LA have been found to alter phospholipid gel to liquid crystal phase transition temperature (Tc), to affect bilayer permeability, to influence molecular packing, and to inhibit the bilayer to hexagonal phase transition. Anesthetics in micellized form disrupt bilayers giving rise to lipid-LA mixed micelle-like aggregates. The question of LA location in the bilayer is also addressed. Special emphasis is placed on work focusing on the quantitative analysis of drug binding, as well as on the effects of binding on physicochemical properties of the LA, such as extent of ionization (pK shifts) and rates of chemical reactions. The understanding of these phenomena has contributed to the development of less toxic liposomal formulations capable of prolonging the duration of anesthesia.