Implantação da avaliação da dinâmica temporal e espacial de processos neurais na eletroencefalografia

TCC(graduação) - Universidade Federal de Santa Catarina. Centro de Ciências Biológicas. Biologia.Uma das ferramentas para avaliação dos processos neurológicos é a eletroencefalografia (EEG), que apresenta diversas técnicas para o estudo das atividades neuronais, suas intercomunicações e funções. Este trabalho apresenta um método para a utilização de duas técnicas de EEG em conjunto, Potencial Relacionado a Evento (ERP) e Tomografia Eletromagnética de Baixa Resolução (LORETA). A técnica de ERP tem o intuito de identificar, no tempo, atividades relevantes para estudo, enquanto a técnica de LORETA é uma tomografia de baixa resolução, identificando de onde provém o sinal registrado na EEG. Por meio do método proposto, é possível identificar os locais no tempo onde ocorrem as atividades relevantes (com o ERP) e analisar a dinâmica espacial cerebral de forma sequencial durante esse período (com a LORETA).One of the tools for evaluation of neurological processes is electroencephalography (EEG), which presents several techniques for the study of neuronal activities, their intercommunications and functions. This work presents a method for the use of two EEG techniques in conjunction, Event Related Potential (ERP) and Low Resolution Electromagnetic Tomography (LORETA). The ERP technique aims to identify, in time, relevant activities for study, while the LORETA technique is a low resolution tomography, identifying where the EEG signal comes from. By means of the proposed method, it is possible to identify the locations in the time where the relevant activities occur (with the ERP) and to analyze the cerebral spatial dynamics in a sequential way during that period (with LORETA)

Effects of Flexibility in Coarse-Grained Models for Bovine Serum Albumin and Immunoglobulin G

We construct a coarse-grained, structure-based, low-resolution, 6-bead flexible model of bovine serum albumin (BSA, PDB: 4F5S), which is a popular example of a globular protein in biophysical research. The model is obtained via direct Boltzmann inversion using all-atom simulations of a single molecule, and its particular form is selected from a large pool of 6-bead coarse-grained models using two suitable metrics that quantify the agreement in the distribution of collective coordinates between all-atom and coarse-grained Brownian dynamics simulations of solutions in the dilute limit. For immunoglobulin G (IgG), a similar structure-based 12-bead model has been introduced in the literature [Chaudhri et al., J. Phys. Chem. B 116, 8045 (2012)] and is employed here to compare findings for the compact BSA molecule and the more anisotropic IgG molecule. We define several modified coarse-grained models of BSA and IgG, which differ in their internal constraints and thus account for a variation of flexibility. We study denser solutions of the coarse-grained models with purely repulsive molecules (achievable by suitable salt conditions) and address the effect of packing and flexibility on dynamic and static behavior. Translational and rotational self-diffusivity is enhanced for more elastic models. Finally, we discuss a number of effective sphere sizes for the BSA molecule, which can be defined from its static and dynamic properties. Here, it is found that the effective sphere diameters lie between 4.9 and 6.1 nm, corresponding to a relative spread of about ±10% around a mean of 5.5 nm

Self-assembly in patchy proteins: From transient networks to attractive glasses

Dynamic properties of crowded protein solutions are difficult to predict and control. This for example considerably limits our ability to create stable and injectable formulations of proteins or peptides at high concentrations. Another physiologically relevant case is presbyopia, or age-related farsightedness, where the pathological stiffening of the eye lens can be related to a liquid-solid transition of the protein mixtures inside the eye lens cells1. It is thus essential to achieve a quantitative understanding of the link between the molecular structure of the proteins and the interactions between them, and how these interactions influence the stability, dynamics and flow properties of the solutions as a function of their concentration. Here we show how we can use a combination of advanced characterization techniques1-4 such as neutron spin echo, small-angle scattering, 3D cross correlation light scattering and microrheology, combined with state-of-the-art computer simulations to assess and predict interparticle interactions and their impact on the dynamics and flow behavior of crowded protein solutions. We particularly point out the enormous influence of weak attractive interactions known to exist between many globular proteins, and demonstrate the dramatic effect of an interaction potential anisotropy such as attractive patches4 and shape anisotropy on the dynamic properties. [1] G. Foffi, G. Savin, S. Bucciarelli, N. Dorsaz, G. Thurston, A. Stradner, P. Schurtenberger; A Hard Sphere-Like Glass Transition in Eye Lens Alpha Crystallin Solutions ; Proc. Natl. Acad. Sci. U. S. A., 111, 16748-16753 (2014). [2] F. Cardinaux, E. Zaccarelli, A. Stradner, S. Bucciarelli, B. Farago, S. Egelhaaf, F. Sciortino, P. Schurtenberger; Cluster-driven dynamical arrest in concentrated lysozyme solutions J. Phys. Chem. B, 115, 7227 (2011). [3] S. Bucciarelli, L. Casal-Dujat, C. De Michele, F. Sciortino, J. Dhont, J. Bergenholtz, B. Farago, P. Schurtenberger, and A. Stradner; Unusual Dynamics of Concentration Fluctuations in Solutions of Weakly Attractive Globular Proteins ; The Journal of Physical Chemistry Letters, 6, 4470-4474 (2015). [4] S. Bucciarelli, J. S. Myung, B. Farago, S. Das, G. A. Viegenthart, O. Holderer, R. G. Winkler, P. Schurtenberger, G. Gompper, and A. Stradner; Dramatic Influence of Attractions on Short-Time Protein Diffusion under Crowded Conditions ; Science Advances, 2, e1601432 (2016)

Viscosity and Diffusion: Crowding and Salt Effects in Protein Solutions

We report on a joint experimental-theoretical study of collective diffusion in, and static shear viscosity of solutions of bovine serum albumin (BSA) proteins, focusing on the dependence on protein and salt concentration. Data obtained from dynamic light scattering and rheometric measurements are compared to theoretical calculations based on an analytically treatable spheroid model of BSA with isotropic screened Coulomb plus hard-sphere interactions. The only input to the dynamics calculations is the static structure factor obtained from a consistent theoretical fit to a concentration series of small-angle X-ray scattering (SAXS) data. This fit is based on an integral equation scheme that combines high accuracy with low computational cost. All experimentally probed dynamic and static properties are reproduced theoretically with an at least semi-quantitative accuracy. For lower protein concentration and low salinity, both theory and experiment show a maximum in the reduced viscosity, caused by the electrostatic repulsion of proteins. The validity range of a generalized Stokes-Einstein (GSE) relation connecting viscosity, collective diffusion coefficient, and osmotic compressibility, proposed by Kholodenko and Douglas [PRE 51, 1081 (1995)] is examined. Significant violation of the GSE relation is found, both in experimental data and in theoretical models, in semi-dilute systems at physiological salinity, and under low-salt conditions for arbitrary protein concentrations

Protein cluster formation in aqueous solution in the presence of multivalent metal ions -a light scattering study

The formation of protein clusters as precursors for crystallization and phase separation is of fundamental and practical interest in protein science. Using multivalent ions, the strengths of both long-range Coulomb repulsion and short-range attraction can be tuned in protein solutions, representing a wellcontrolled model system to study static and dynamic properties of clustering during the transition from a charge-stabilized to an aggregate regime. Here, we study compressibility, diffusion, and size of solutes by means of static (SLS) and dynamic light scattering (DLS) in solutions of bovine serum albumin (BSA) and YCl 3 . For this and comparable systems, an increasing screening and ultimately inversion of the protein surface charge induce a rich phase behavior including reentrant condensation, liquid-liquid phase separation and crystallization, which puts the cluster formation in the context of precursor formation and nucleation of liquid and crystalline phases. We find that, approaching the turbid aggregate regime with increasing salt concentration c s , the diffusion coefficients decrease and the scattered intensity increases by orders of magnitude, evidencing increasing correlation lengths likely associated with clustering. The combination of static and dynamic observations suggests the formation of BSA clusters with a size on the order of 100 nm. The global thermodynamic state seems to be stable over at least several hours. Surprisingly, results on collective diffusion and inverse compressibility from different protein concentrations can be rescaled into master curves as a function of c s /c*, where c* is the critical salt concentration of the transition to the turbid aggregate regime

On the identification of folium by SERS: from crude extracts to illuminated codices

The ancient purple dye known as folium is still a mystery for both scientists and art historians. Today, it is commonly assumed that folium was produced from the fruits of Chrozophora tinctoria (L.) A. Juss., a plant belonging to the Euphorbiaceae family, and efforts have been mainly devoted to highlight the analytical features of the dyes extracted from this plant, whereas detection in ancient manuscripts has been mainly based on poorly selective, non-invasive analytical techniques. As a consequence, the possibility that the actual source for the dye could have been so far misunderstood cannot be excluded. Surface-enhanced Raman spectroscopy (SERS), a highly selective and sensitive analytical technique, has been used here to characterize both extracts from C.\u2009tinctoria and a microsample taken from a medieval manuscript. The behaviour of the dyes as SERS probes has been investigated in order to set up an accurate and selective procedure for the identification of the dye in ancient artworks. By unambiguously detecting the dye by SERS in the microsample of the medieval manuscript, we also demonstrated that the purple dye mentioned in ancient treatises is definitely linked with the aqueous extract from purple fruits of C.\u2009tinctoria

A Highly Conserved Poc1 Protein Characterized in Embryos of the Hydrozoan Clytia hemisphaerica: Localization and Functional Studies

Poc1 (Protein of Centriole 1) proteins are highly conserved WD40 domain-containing centriole components, well characterized in the alga Chlamydomonas, the ciliated protazoan Tetrahymena, the insect Drosophila and in vertebrate cells including Xenopus and zebrafish embryos. Functions and localizations related to the centriole and ciliary axoneme have been demonstrated for Poc1 in a range of species. The vertebrate Poc1 protein has also been reported to show an additional association with mitochondria, including enrichment in the specialized “germ plasm” region of Xenopus oocytes. We have identified and characterized a highly conserved Poc1 protein in the cnidarian Clytia hemisphaerica. Clytia Poc1 mRNA was found to be strongly expressed in eggs and early embryos, showing a punctate perinuclear localization in young oocytes. Fluorescence-tagged Poc1 proteins expressed in developing embryos showed strong localization to centrioles, including basal bodies. Anti-human Poc1 antibodies decorated mitochondria in Clytia, as reported in human cells, but failed to recognise endogenous or fluorescent-tagged Clytia Poc1. Injection of specific morpholino oligonucleotides into Clytia eggs prior to fertilization to repress Poc1 mRNA translation interfered with cell division from the blastula stage, likely corresponding to when neosynthesis normally takes over from maternally supplied protein. Cell cycle lengthening and arrest were observed, phenotypes consistent with an impaired centriolar biogenesis or function. The specificity of the defects could be demonstrated by injection of synthetic Poc1 mRNA, which restored normal development. We conclude that in Clytia embryos, Poc1 has an essentially centriolar localization and function

ApoE and ApoE Nascent-Like HDL Particles at Model Cellular Membranes: Effect of Protein Isoform and Membrane Composition.

Apolipoprotein E (ApoE), an important mediator of lipid transportation in plasma and the nervous system, plays a large role in diseases such as atherosclerosis and Alzheimer's. The major allele variants ApoE3 and ApoE4 differ only by one amino acid. However, this difference has major consequences for the physiological behaviour of each variant. In this paper, we follow (i) the initial interaction of lipid-free ApoE variants with model membranes as a function of lipid saturation, (ii) the formation of reconstituted High-Density Lipoprotein-like particles (rHDL) and their structural characterisation, and (iii) the rHDL ability to exchange lipids with model membranes made of saturated lipids in the presence and absence of cholesterol [1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) or 1-palmitoyl-2-oleoyl-glycero-3-phosphocholine (POPC) with and without 20 mol% cholesterol]. Our neutron reflection results demonstrate that the protein variants interact differently with the model membranes, adopting different protein conformations. Moreover, the ApoE3 structure at the model membrane is sensitive to the level of lipid unsaturation. Small-angle neutron scattering shows that the ApoE containing lipid particles form elliptical disc-like structures, similar in shape but larger than nascent or discoidal HDL based on Apolipoprotein A1 (ApoA1). Neutron reflection shows that ApoE-rHDL do not remove cholesterol but rather exchange saturated lipids, as occurs in the brain. In contrast, ApoA1-containing particles remove and exchange lipids to a greater extent as occurs elsewhere in the body

Metabolic rate limits the effect of sperm competition on mammalian spermatogenesis.

Sperm competition leads to increased sperm production in many taxa. This response may result from increases in testes size, changes in testicular architecture or changes in the kinetics of spermatogenesis, but the impact of each one of these processes on sperm production has not been studied in an integrated manner. Furthermore, such response may be limited in species with low mass-specific metabolic rate (MSMR), i.e., large-bodied species, because they cannot process energy and resources efficiently enough both at the organismic and cellular levels. Here we compare 99 mammalian species and show that higher levels of sperm competition correlated with a) higher proportions of seminiferous tubules, b) shorter seminiferous epithelium cycle lengths (SECL) which reduce the time required to produce sperm, and c) higher efficiencies of Sertoli cells (involved in sperm maturation). These responses to sperm competition, in turn, result in higher daily sperm production, more sperm stored in the epididymides, and more sperm in the ejaculate. However, the two processes that require processing resources at faster rates (SECL and efficiency of Sertoli cells) only respond to sperm competition in species with high MSMR. Thus, increases in sperm production with intense sperm competition occur via a complex network of mechanisms, but some are constrained by MSMR