Banca de QUALIFICAÇÃO: ANTONIO MORAIS NETO

Uma banca de QUALIFICAÇÃO de MESTRADO foi cadastrada pelo programa.
DISCENTE : ANTONIO MORAIS NETO
DATA : 06/11/2023
HORA: 14:30
LOCAL: https://conferenciaweb.rnp.br/sala/monica-52
TÍTULO:

NATURE OF THE INTERACTION OF ADENINE-5-HALOURACIL PAIRS WITH SILVER NANOPARTICLES: A THEORETICAL-EXPERIMENTAL APPROACH

PÁGINAS: 20
RESUMO:

In recent years, the halogenated 5-substituted uracil derivatives (5-fluoro-, 5-chloro, and
5-bromouracil) have drawn attention due to their pharmacological properties, and their
importance as biomarkers and, recently, also as water pollutants. From an analytical point
of view, these species are expected to be at very low levels in biological and
environmental samples, and the development of methodologies for their determination is
a central goal in research. Raman technique and its special effect, Surface Enhanced
Raman Scattering (SERS), is a very suitable approach for detecting and quantifying this
kind of compound, mainly because most DNA and RNA derivatives are good light
scatterers, yielding rich-information spectra. In practice, enhancing the Raman signal
requires a nanostructured noble metal surface with the species of interest attached to it,
and to maximize the effect, a deeper comprehension of the nature of the analyte-metal
surface interaction is desirable. The structural information SERS spectra provide can be
reinforced by theoretical approaches, such as the Density Functional Theory (DFT)
calculations. In the first part of this work, the 5-halouracils attached to silver nanoparticles
(AgNPs) were studied experimentally and theoretically. From the results, those moieties
showing higher band enhancement were identified. Also, the observed patterns in the
spectroscopic behavior showed a trend related to the electronegativity at the halogenated
bonds suggesting their direct influence in enhancing C=C and C=O stretching modes. The
5-bromouracil showed a higher affinity for the silver surface, suggesting a stronger effect
of electronegativity and halogen atom size. In the following stages, their ability to form
base pairs with adenine through hydrogen bonding will be studied as a strategy to improve
the detectability through SERS. This is based on the well-known high affinity of adenine
towards metal nanoparticles, which would favor the orientation of the 5-halouracils, to
lower the limit of detection. To accomplish this, an optimization based on the Design of
Experiments methodology is being developed, to improve the reproducibility of SERS
spectra. Here, a fractional factorial design was first run, and the more significant variables
identified were the volume of 5-halouracil and sodium chloride (aggregating agent).
Then, through a central composite rotatable design (DCCR), the optimal ranges for
validation were the lowest volumes for 5-FU (3.43 μL), 5-ClU (20 μL), and the higher
volume value for 5-BrU (200 μL). For NaCl, the optimized volume was 60, 20, and 100
μL for 5-FU, 5-ClU, and 5-BrU respectively.

MEMBROS DA BANCA:
Presidente - Interno ao Programa - 3047441 - MONICA BENICIA MAMIAN LOPEZ
Membro Titular - Examinador(a) Interno ao Programa - 149.405.258-05 - KATHIA MARIA HONORIO - USP
Membro Titular - Examinador(a) Externo à Instituição - MARIANA RAMOS DE ALMEIDA - UFMG
Membro Suplente - Examinador(a) Interno ao Programa - 3008569 - BRUNO GUZZO DA SILVA
Membro Suplente - Examinador(a) Externo à Instituição - DIEGO PEREIRA DOS SANTOS - UNICAMP