Fluorescence probing of structural and functional changes of proteins induced by ultrafiltration

Both case studies clearly demonstrate that the mechanisms that regulate the structural changes of the permeated proteins depend on the operational and physicochemical conditions and on the protein–membrane system under study. Consequently, the structural/functional alterations induced on the proteins during ultrafiltration may be minimized by a suitable adjustment of the operational and environmental conditions. Moreover, the results obtained showed that the conclusions taken for one specific protein can not be generalized to other proteins. In addition, the fluorescence techniques used proved to be sensitive and non-invasive methods which, when used complementarily, constitute a powerful tool for monitoring structural alterations induced by ultrafiltration processes and to infer about alterations of enzymatic activity. Acknowledgments The authors acknowledge Carla Rodrigues and Dr. Alexander Fedorov for their technical support in the inductively coupled plasma (ICP) and time resolved fluorescence measurements. Additionally, the authors would like to acknowledge Prof. Gaspar Martinho and to Prof. António Maçanita for the access to the TRSPC equipment and to the spectrofluorometer for the fluorescence anisotropy measurements. Carla A. M. Portugal acknowledges Fundação para a Ciência e a Tecnologia, Portugal, for the PhD scholarship PRAXISXXI/BD/19817/99.