The kinetic aspects of the exchange mechanism and of the ongoing structural modification with interfacial residence time for ribonuclease A adsorbed on hydrophilic surfaces are investigated. This is done by means of radiolabeling and FTIR−ATR techniques. An important decrease of the protein exchange ability and increase of the irreversibly bound protein fraction with adsorption time is found. These observations are compared with a decrease of the relative content of β-sheet and an increase in turns and unordered structures in the adsorbed protein layer. Both the exchange process and the structural modifications vary with comparable characteristic times, on the order of 20 h for the exchange process on the TiO2 surface and 10−15 h for the structural modifications on the germanium one. These data suggest that the decrease in the protein exchange ability results from important structural changes following adsorption, which corresponds to a decrease of the ordered structure of the protein.

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This research presents the alkali treatment effect on three types of agricultural residues: sweet clover (SCS), buckwheat (BS), and rapeseed straws (RS). The aim of the study was to find the optimal treatment conditions for each straw type, and to assess the potential of sweet clover straw as reinforcement for polymer composites in comparison to buckwheat and rapeseed. The straws were ground and treated for 15, 30, and 60 min using NaOH at concentrations of 2, 5, and 10%. To investigate the treatment results on the SCS, BS, and RS fibers, Fourier transform infrared spectroscopy, scanning electron microscopy, optical microscope, X-ray diffraction, and thermogravimetric analysis were used. Results indicate that the optimal room-temperature alkaline-treatment conditions of SCS fibers were the same as those for RS treated with 2% NaOH solution for 30 min. These conditions were milder in comparison to those used for the treatment of BS: 60 min in a 5% NaOH solution. During the treatment, noncellulosic substances were largely removed, and the aspect ratio of the fibers was increased, and the destruction temperature, crystallinity, and morphology were also affected. Consequently, SCS has promising potential for use in polymer composites.