Publications by authors named "Constantin-Daniel Negut"

2 Publications

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A New Setup for Real-Time Investigations of Optical Fiber Sensors Subjected to Gamma-Rays: Case Study on Long Period Gratings.

Sensors (Basel) 2020 Jul 24;20(15). Epub 2020 Jul 24.

Department of Engineering, University of Naples "Parthenope", Centro Direzionale Isola C4, 80143 Naples, Italy.

In this work, we present a new setup for real-time investigations of optical fibers and optical fiber sensors while being subjected to gamma-rays. The investigation of the radiation effects on novel or well-assessed sensing devices has attracted a lot of interest, however, the facilities required to do this (when available) are barely accessible to the device to be characterized. In order to reduce the limitations of these types of experiments and ensure a highly controlled environment, we implemented a configuration that permits the on-line testing of optical components inside a Co-60 gamma chamber research irradiator. To show the advantages of this new approach, we present a case study that compares an arc-induced optical fiber long period grating (LPG) irradiated in a gamma chamber with the same type of grating irradiated with gamma-rays from a Co-60 industrial irradiator. In order to better understand the effects of radiation on such components and their behavior in radiation environments, we focus on the homogeneity of the radiation field and parameter customizability as well as the high reproducibility of the experiments.
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http://dx.doi.org/10.3390/s20154129DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7436142PMC
July 2020

Synthesis and Structural Investigation of New Bio-Relevant Complexes of Lanthanides with 5-Hydroxyflavone: DNA Binding and Protein Interaction Studies.

Molecules 2016 Dec 16;21(12). Epub 2016 Dec 16.

Department of General and Inorganic Chemistry, Faculty of Pharmacy, "Carol Davila" University of Medicine and Pharmacy, 6 Traian Vuia Str., 020956 Bucharest, Romania.

In the present work, we attempted to develop new metal coordination complexes of the natural flavonoid 5-hydroxyflavone with Sm(III), Eu(III), Gd(III), Tb(III). The resultant hydroxo complexes have been characterized by a variety of spectroscopic techniques, including fluorescence, FT-IR, UV-Vis, EPR and mass spectral studies. The general chemical formula of the complexes is [Ln(CH₉O₃)₃(OH)₂(H₂O)]·H₂O, where Ln is the lanthanide cation and x = 0 for Sm(III), x = 1 for Eu(III), Gd(III), Tb(III) and = 0 for Sm(III), Gd(III), Tb(III), = 1 for Eu(III), respectively. The proposed structures of the complexes were optimized by DFT calculations. Theoretical calculations and experimental determinations sustain the proposed structures of the hydroxo complexes, with two molecules of 5-hydroxyflavone acting as monoanionic bidentate chelate ligands. The interaction of the complexes with calf thymus DNA has been explored by fluorescence titration and UV-Vis absorption binding studies, and revealed that the synthesized complexes interact with DNA with binding constants (K) ~ 10⁴. Human serum albumin (HSA) and transferrin (Tf) binding studies have also been performed by fluorescence titration techniques (fluorescence quenching studies, synchronous fluorescence spectra). The apparent association constants (K) and thermodynamic parameters have been calculated from the fluorescence quenching experiment at 299 K, 308 K, and 318 K. The quenching curves indicate that the complexes bind to HSA with smaller affinity than the ligand, but to Tf with higher binding affinities than the ligand.
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http://dx.doi.org/10.3390/molecules21121737DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6273368PMC
December 2016