66 research outputs found

    Photon Harvesting Molecules: Ionization Potential from Quantum Chemical Calculations of Phytoplanktonic Pigments for MALDI-MS Analysis

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    El Potencial de Ionización (PI) de especies químicas es de vital importancia en técnicas de química analítica como Matrix-Assisted Laser Desorption/ Ionization (MALDI). Específicamente, el cálculo de PI es usado rutinariamente en MALDI con matrices de Transferencia Electrónica (TE) para la selección de la matriz adecuada para una familia de especies químicas. En este estudio se usaron metodologías computacionales basadas en la mecánica cuántica para determinar teóricamente los PIs de un grupo de pigmentos fotosensibles provenientes del fitoplancton y así poder realizar de forma más acertadael proceso de selección de matrices MALDI. Los PIs fueron determinados usando el teorema de Koopmans a través de Optimizaciones Geométricas y cálculos de Single Point Energy (SPE) con nivel de teoría Hartree-Fock de capa cerrada (RHF). Las estructuras de 24 pigmentos fueron optimizadas y sus PIs fueron determinados. Los valores de PIs calculados están muy cercanos a los reportes experimentales de la literatura, con un porcentaje de error absoluto aproximado de 3,7% y con cambios estructurales relacionados con las propiedades químicas de los pigmentos y IPs. A partir de nuestros resultados se sugiere que algunas matrices MALDI ET tales como la DCTB (PI = 8,5 eV) y CNPV-OCH3 (PI = 8,3 eV), podrían ser las más adecuadas para ser usadas con esta familia de compuestos.  The Ionization Potential (IP) of chemical species is of paramount importance for the Matrix Assisted Laser Desorption/Ionization (MALDI) analyticaltechnique. Specifically, IPs are used in MALDI MS Electron Transfer (ET) as a parameter to select the matrix for a given family of chemical species. We useda quantum chemical methodology to computationally determine IPs for a set of photosensible phytoplanktonic pigments. These calculations could be used as a guide for MALDI matrix selection. IPs were determined using Koopman’s Theorem, via Geometry Optimization and Single Point Energy within the Restricted Closed-Shell Hartree-Fock (RHF) technique. Structures of a twenty-four set of pigments were geometrically optimized, and their IPsdetermined. Calculated IP’s are in close agreement to reported experimental IPs within an average 3.7% absolute error. Structural features of the chemical species studied have a closed relationship with their chemical properties and IP’s. Our results suggest that ET-MALDI matrices such as DCTB (IP = 8.5 eV) and CNPV-OCH3 (IP = 8.3 eV) could be more suitable to analyze these types of chemical species

    Electron-transfer MALDI MS methodology for microalgae/phytoplankton pigments analysis

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    The method describes pigment analysis from microalgae/phytoplankton extracts using electron-transfer Matrix-Assisted Laser Desorption Ionization Mass Spectrometry (ET MALDI MS). Current microalgae/phytoplankton pigment analysis requires resource- and time-intensive chromatographic methods due to the broad polarity range of the target analytes. On the other hand, traditional MALDI MS chlorophyll analysis, using proton-transfer matrices such as 2,5-dihydroxybenzoic acid (DHB) or α-cyano-4-hydroxycinnamic acid (CHCA), results in central metal loss and phytol–ester cleavage. ET MALDI MS is an alternative for the rapid screening and detection of pigments in microalgae extracts. • MALDI matrices with ionization energies above 8.0 eV guarantee electron-transfer processes from photosynthetic and photoprotective pigments whose ionization energies lay below 7.5 eV. • ET MALDI MS pigment analysis agrees with data gathered from conventional chromatographic techniques (HPLC) and optical microscopy for pigment extracts from C. vulgaris cultures and freshwater phytoplankton samples. • The ET MALDI MS method allows fast and reliable detection of pigments in microalgae cultures and freshwater phytoplankton samples
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