Publications by authors named "David Soares"

Light-activated fluorescence represents a potent tool for investigating subcellular structures and dynamics, offering enhanced control over the temporal and spatial aspects of the fluorescence signal. While alkyl-substituted tetrazine has previously been reported as a photo-trigger for various fluorophore scaffolds, its limited photochemical efficiency and high activation energy have constrained its widespread application at the biomolecular level. In this study, we demonstrate that a single sulfur atom substitution of tetrazine greatly enhances the photochemical properties of tetrazine conjugates and significantly improves their photocleavage efficiency.

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Mesenchymal-epithelial transition (MET) is essential for tissue and organ development and is thought to contribute to cancer by enabling the establishment of metastatic lesions. Despite its importance in both health and disease, there is a lack of in vitro platforms to study MET and little is known about the regulation of MET by mechanical cues. Here, hyaluronic acid-based hydrogels with dynamic and tunable stiffnesses mimicking that of normal and tumorigenic mammary tissue are synthesized.

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Herein, the origin of interfacial water nanosized channel distributions attached onto Nafion surfaces is investigated. The surface fibrillary hydrophilic and hydrophobic arrangements were observed on AFM images scanned on Nafion surfaces immersed in water. Then, by analyzing the force vs separation curves, it is possible to map arrays of interfacial water channels and their locations.

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A significant improvement in spatial resolution is reported in Nafion surface maps when compared to previous atomic force microscopy images of the Nafion surface scanned in air. The technique ability is to generate maps showing approximately few nanometer (∼2-5 nm) patterns to the long fiber length (>2 μm). Atomic force microscopy force vs separation curve profiles registered in water are used to characterize the surface hydrophobic and hydrophilic domains.

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While there seems to be broad agreement that cluster formation does exist near solid surfaces, its presence at the liquid/vapor interface is controversial. We report experimental studies we have carried out on interfacial water attached on hydrophobic and hydrophilic surfaces. Nanosized steps in the measured force vs distance to the surface curves characterize water cluster profiles.

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Objective: Recent studies indicate that brown adipose tissue, in addition to its role in thermogenesis, has a role in the regulation of whole-body metabolism. Here we characterize the metabolic effects of deleting Rab10, a protein key for insulin stimulation of glucose uptake into white adipocytes, solely from brown adipocytes.

Methods: We used a murine brown adipocyte cell line and stromal vascular fraction-derived in vitro differentiated brown adipocytes to study the role of Rab10 in insulin-stimulated GLUT4 translocation to the plasma membrane and insulin-stimulated glucose uptake.

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A technique to image ion pairs in solution is reported. We investigated structural and dynamic properties of ion-pair distributions deposited on highly oriented pyrolytic graphite (HOPG) surfaces in electrolyte solutions. Atomic force microscopy images of HOPG immersed in NaCl and KCl solutions display regular arrangements on top of the hexagonal carbon rings forming the HOPG atomic structure.

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Excess proton structures in water remain unclear. The motion and nature of excess protons in water were probed using a supported water bridge structure in electric field () with an intensity of ∼10 V/m. The experimental setup generated protons that exhibit a long lifetime.

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A clear molecular description of excess hydrated protons and their local hydrogen bond transport network remains elusive. Here, the hydrogen bond network of excess hydrated protons in water bridges was probed by measuring their Raman spectra and comparing them to the spectra of protons in ice and water. The proton vibrational spectrum and the hydrogen bond network translational and librational spectra were recorded.

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Background: Measurements and models of current flow in the brain during transcranial Direct Current Stimulation (tDCS) indicate stimulation of regions in-between electrodes. Moreover, the folded cortex results in local fluctuations in current flow intensity and direction, and animal studies suggest current flow direction relative to cortical columns determines response to tDCS.

Methods: Here we test this idea by using Transcranial Magnetic Stimulation Motor Evoked Potentials (TMS-MEP) to measure changes in corticospinal excitability following tDCS applied with electrodes aligned orthogonal (across) or parallel to M1 in the central sulcus.

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There are substantial differences across species in the organization and function of the motor pathways. These differences extend to basic electrophysiological properties. Thus, in rat motor cortex, pyramidal cells have long duration action potentials, while in the macaque, some pyramidal neurons exhibit short duration "thin" spikes.

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Glucose-dependent insulinotropic polypeptide (GIP) is an incretin hormone involved in nutrient homeostasis. GIP receptor (GIPR) is constitutively internalized and returned to the plasma membrane, atypical behavior for a G-protein-coupled receptor (GPCR). GIP promotes GIPR downregulation from the plasma membrane by inhibiting recycling without affecting internalization.

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Structures of crystallized deposits formed by the molecular self-assembly of aspartic acid and valine on silicon substrates were imaged by atomic force microscopy. Images of d- and l-aspartic acid crystal surfaces showing extended molecularly flat sheets or regions separated by single molecule thick steps are presented. Distinct orientation surfaces were imaged, which, combined with the single molecule step size, defines the geometry of the crystal.

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Objective: Identify the impact of corrective techniques in the mortality rate trends for cardiovascular disease, ischemic heart diseases, and cerebrovascular diseases, in the City of Manaus, State of Amazonas, Brazil, between 1980 and 2007.

Methods: Data were obtained from the Unified Health System's Information Technology Department and the following steps undertaken: (1) proportional redistribution of death records, but without taking into account age and/or sex; (2) redistribution of ill-defined deaths among those whose cause is known; (3) treatment and reallocation of so-called "junk codes" in cardiology; and (4) correction of underrecordings of deaths by indirect techniques. Records treated in steps 1 and 2, and steps 3 and 4 together, generated base rates, adjusted rates, and adjusted and corrected rates, respectively, which were analyzed according to sex and age cohort; subsequently, they were standardized by the direct method.

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Water at room temperature is not simply a medium for which uniform properties can always be assumed. Water close to solid hydrophobic or hydrophilic surfaces has elasticity, which is measured by monitoring the quartz crystal microbalance (QCM) resonant frequency and resistance. Small additions of salt are shown to modify this elasticity.

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Self-assembled aggregates of amphiphilic surfactant molecules formed on solid surfaces are similar to biological membranes. To understand the formation mechanism of these aggregates, we have studied the formation of self-organized monolayers from low-concentration sodium dodecyl sulfate (SDS) aqueous solutions (concentration below the critical micelle concentration) on gold surfaces. The study has been carried out by using simultaneously quartz crystal microbalance (QCM) and open circuit potential measurements in situ.

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