Browsing by Author "Neves-Petersen, Maria Teresa"
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- Multifunctional magnetic iron oxide nanoparticles: diverse synthetic approaches, surface modifications, cytotoxicity towards biomedical and industrial applicationsPublication . Natarajan, Subramanian; Harini, Kannan; Gajula, Gnana P; Sarmento, Bruno; Neves-Petersen, Maria Teresa; Thiagarajan, ViruthachalamMagnetic iron oxide nanoparticles (MIONPs) play a major role in the emerging fields of nanotechnology to facilitate rapid advancements in biomedical and industrial platforms. The superparamagnetic properties of MIONPs and their environment friendly synthetic methods with well-defined particle size have become indispensable to obtain their full potential in a variety of applications ranging from cellular to diverse areas of biomedical science. Thus, the broadened scope and need for MIONPs in their demanding fields of applications required to be highlighted for a comprehensive understanding of their state-of-the-art. Many synthetic methods, however, do not entirely abolish their undesired cytotoxic effects caused by free radical production and high iron dosage. In addition, the agglomeration of MIONPs has also been a major problem. To alleviate these issues, suitable surface modification strategies adaptive to MIONPs has been suggested not only for the effective cytotoxicity control but also to minimize their agglomeration. The surface modification using inorganic and organic polymeric materials would represent an efficient strategy to utilize the diagnostic and therapeutic potentials of MIONPs in various human diseases including cancer. This review article elaborates the structural and magnetic properties of MIONPs, specifically magnetite, maghemite and hematite, followed by the important synthetic methods that can be exploited for biomedical approaches. The in vivo cytotoxic effects and the possible surface modifications employed to eliminate the cytotoxicity thereby enhancing the nanoparticle efficacy are also critically discussed. The roles and applications of surface modified MIONPs in medical and industrial platforms have been described for the benefits of global well-being.
- Photophysics and photochemistry of horseradish peroxidase A2 upon ultraviolet illuminationPublication . Neves-Petersen, Maria Teresa; Klitgaard, Soren; Leitao Carvalho, Ana Sofia; Petersen, Steffen B.; de Barros, Maria Raquel Aires; Melo, EduardoDetailed analysis of the effects of ultraviolet (UV) and blue light illumination of horseradish peroxidase A2, a heme-containing enzyme that reduces H2O2 to oxidize organic and inorganic compounds, is presented. The effects of increasing illumination time on the protein's enzymatic activity, Reinheitzahl value,. fluorescence emission,. fluorescence lifetime distribution,. fluorescence mean lifetime, and heme absorption are reported. UV illumination leads to an exponential decay of the enzyme activity followed by changes in heme group absorption. Longer UV illumination time leads to lower T-m values as well as helical content loss. Prolonged UV illumination and heme irradiation at 403 nm has a pronounced effect on the. fluorescence quantum yield correlated with changes in the prosthetic group pocket, leading to a pronounced decrease in the heme's Soret absorbance band. Analysis of the picosecond-resolved. fluorescence emission of horseradish peroxidase A2 with streak camera shows that UV illumination induces an exponential change in the preexponential factors distribution associated to the protein's. fluorescence lifetimes, leading to an exponential increase of the mean. fluorescence lifetime. Illumination of aromatic residues and of the heme group leads to changes indicative of heme leaving the molecule and/or that photoinduced chemical changes occur in the heme moiety. Our studies bring new insight into light-induced reactions in proteins. We show how streak camera technology can be of outstanding value to follow such ultrafast processes and how streak camera data can be correlated with protein structural changes.