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In the present work we have gone a step forward in the understanding of the DNA-cisplatin interaction, investigating the role of the ionic strength on the complexes formation. To achieve this task, we use optical tweezers to perform force spectroscopy on the DNA-cisplatin complexes, determining their mechanical parameters as a function of the drug concentration in the sample for three different buffers. From such measurements, we determine the binding parameters and study their behavior as a function of the ionic strength. The equilibrium binding constant decreases with the counterion concentration ([Na]) and can be used to estimate the effective net charge of cisplatin in solution. The cooperativity degree of the binding reaction, on the other hand, increases with the ionic strength, as a result of the different conformational changes induced by the drug on the double-helix when binding under different buffer conditions. Such results can be used to modulate the drug binding to DNA, by appropriately setting the ionic strength of the surrounding buffer. The conclusions drawn provide significant new insights on the complex cooperative interactions between the DNA molecule and the class of platinum-based compounds, much used in chemotherapies.

A single-beam time-resolved Z-scan method is introduced to characterize the nonlinear refraction of slow (millisecond) response absorbers with cw radiation. Owing to the elimination of parasitic linear effects, the technique is able to measure induced phase distortions as small as λ/104. We demonstrate this method on several materials using low power Ar+ and He-Ne lasers.

Here we report a new study performed at single molecule level on the interaction of the antineoplastic drug Carboplatin and the DNA molecule - the main target of the drug inside cells in cancer chemotherapies. By using optical tweezers, we measure how the mechanical properties of the DNA-Carboplatin complexes changes as a function of the drug concentration in the sample, for two different ionic strengths ([Na] = 150 mM and [Na] = 1 mM). From these measurements, the binding mechanism and the physicochemical (binding) parameters of the interaction were inferred and directly compared to those obtained for the precursor drug Cisplatin under equivalent conditions. As the main conclusion, we show that Carboplatin binds preferentially forming covalent monoadducts in contrast to Cisplatin, which is hydrolyzed easier and presents a higher efficiency in forming covalent diadducts along the double-helix. In addition, we explicitly show that Carboplatin is much less sensitive to ionic strength changes when compared to Cisplatin. These findings provide new insights on the interactions of platinum-based compounds with the DNA molecule, being important to improve the current treatments and in the development of new antineoplastic agents.

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We investigate the behavior of the Z-scan technique in the case where the phase of the electric field departs from a Gaussian due to the saturation of the optical nonlinearity. The usual Gaussian decomposition theoretical approach cannot describe experimental results obtained with well-characterized chromium-doped saturable absorbers: ruby and alexandrite. This aim can be accomplished by extending the theory based on the Hankel transformation of the electric field through the inclusion of the phase saturation. As in the case of Kerr media, the nonlinear refractive index can be obtained from the measurement of the transmittance difference between peak and valley.

The new triticale cultivars caught the industries attention due to excellent nutritional composition. The rare literature regarding hydration process intensification, coupled with the lack of research regarding the hydration of triticale, motivated this research. This study aimed to evaluate the hydration process intensification of two cultivars triticale. The isothermal operation was done at temperature range of 20–40°C and compared to process intensification using amplitude of 10°C and half‐cycle of 15 min, at an average temperature of 30°C. In parallel to hydration process, the fit of the Peleg model to the experimental data was evaluated and the morphology of the starch granules was observed using SEM images. The hydration temperature did not affect the starch grains morphology. The hydration kinetic was obtained applying the Peleg model, which exhibited a good fit for both operations. The model parameters values (K1 and K2) indicated that the periodic hydration process exhibits a greater water absorption rate and a final higher moisture for both cultivars. The periodic operation reduced the energy consumption of hydration process in approximately 50%, this reduction proves that this operation with temperature modulation is a process strategy highly promising for grains hydration process intensification. Practical Applications Triticale is a hybrid grain that has been drawing attention from various industrial sectors for application in the production of malt, packages, various foods, and ethanol. Thus, an understanding of the hydration kinetics of triticale that has not yet been described in the literature, together with the morphology of the starch grains, is of supreme importance. In view of this, the present work presents the water absorption of triticale when submitted to periodic operation by means of temperature modulation, with the aim of intensifying the hydration process as compared to the conventional operation, in addition to observing any potential morphological alterations in the starch grains. These results assist in the monitoring and control of industrial and academic processes, providing a better understanding of the hydration mechanisms and the morphology of the starch granules of the triticale for a possible inclusion of this cereal in new applications and product development.