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Studies on the interaction sites of peptide toxins and ion channels typically involve site-directed mutations in toxins. However, natural mutant toxins exist among them, offering insights into how the evolutionary process has conserved crucial sequences for activities and molecular target selection. In this study, we present a comparative investigation using electrophysiological approaches and computational analysis between two alpha toxins from evolutionarily close scorpion species of the genus Tityus, namely, Tst3 and Ts3 from T. stigmurus and T. serrulatus, respectively. These toxins exhibit three natural substitutions near the C-terminal region, which is directly involved in the interaction between alpha toxins and Nav channels. Additionally, we characterized the activity of the Tst3 toxin on Nav1.1-Nav1.7 channels. The three natural changes between the toxins did not alter sensitivity to Nav1.4, maintaining similar intensities regarding their ability to alter opening probabilities, delay fast inactivation, and induce persistent currents. Computational analysis demonstrated a preference for the down conformation of VSD4 and a shift in the conformational equilibrium towards this state. This illustrates that the sequence of these toxins retained the necessary information, even with alterations in the interaction site region. Through electrophysiological and computational analyses, screening of the Tst3 toxin on sodium isoform revealed its classification as a classic α-NaTx with a broad spectrum of activity. It effectively delays fast inactivation across all tested isoforms. Structural analysis of molecular energetics at the interface of the VSD4-Tst3 complex further confirmed this effect. [ABSTRACT FROM AUTHOR]

The article discusses the long-term growth potential of Brazil that is said to be generating interest among property investors as of July 2012. Topics covered include how to navigate the debt markets in the country, Brazil's large cities that are said to be generally underserved in the upper-tier segments, and entry barriers, development constraints, and challenges for investors.

• The estimation of clay content may assists specific management in large areas. • Simple linear regression, power model, and artificial neural network were used. • Magnetic susceptibility can be used to estimate the soil clay content. • Modeling by nonlinear models increases the estimation accuracy. • Depending on clay content, the model's choice is essential to obtain high accuracy. The application of pedotransfer functions for soil attribute estimation has economic and environmental advantages. However, the appropriate choice of models is essential to obtain high accuracy. The aim was of this study was to evaluate the magnetic susceptibility (χ) potential to estimate soil clay content and to compare the estimation accuracy using linear (simple linear regression, SLR) and nonlinear models (power model, PM, and artificial neural networks, ANNs). An area of approximately 870 ha, cultivated with sugarcane in southeastern Brazil, was delimited and georeferenced for the collection of soil samples. Soil samples were collected every 2.5 ha (0.00–0.25 m), resulting in 372 points. A transect was directed in the area, and another 132 soil samples were collected at regular intervals of 30 m in the same layer. The samples were sent to the laboratory, and χ values were obtained for all points. Pedotransfer functions were developed to estimate the soil clay content using the χ values. The models were calibrated with the 372 points collected from the regular mesh of the 870-ha area, using the 132 points of the transect for validation. Regardless of the type of model applied to the pedotransfer functions, χ proved highly accurate for estimating soil clay content. However, the ANNs and PM increased the estimation accuracy, attenuated the error, and increased the estimation precision for soil samples with clay content below 200 g kg−1. [ABSTRACT FROM AUTHOR]

Ts17 was purified from the venom of the scorpion Tityus serrulatus , the most dangerous scorpion species in Brazil. The activity on Na v 1.1-Na v 1.7 channels was electrophysiologically characterized by patch-clamp technique. Ts17 amino acid sequence indicated high similarity to alpha-scorpion toxins; however, it presented beta-toxin activity, altering the kinetics of the Na+-channels. The most affected subtypes during activation (with and without prepulse) and inactivation phases were Na v 1.2 and Na v 1.5, respectively. For recovery from inactivation, the most affected voltage-gated sodium channel was Na v 1.5. Circular dichroism spectra showed that Ts17 presents mainly β-sheet and unordered structures at all analyzed pHs, and the maximum value of α-helix was found at pH 4.0 (13.3 %). Based on the results, Ts17 might be used as a template to develop a new cardiac drug. Key contribution Purification of Ts17 from Tityus serrulatus , electrophysiological characterization of Ts17 on voltage-gated sodium channel subtypes, β-toxin classification. [Display omitted] • Peptide isolated from Tityus serrulatus venom and characterized by patch-clamp. • Na v 1.5 was the subtype most affected by the toxin in recovery from inactivation. • Ts17 is a β-scorpion toxin with a structure related to α-scorpion toxins. • α and β-NaScTxs groups have high conservation of the tridimensional structure. • Ts17 is a peptide that might be used as a template to develop a new cardiac drug. [ABSTRACT FROM AUTHOR]