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Study of Tryptophan Lifetime Fluorescence Following Low-Density Lipoprotein Modification

Volume 67, Number 4 (April 2013) Page 379-384

LETÍCIA BONFANTE SICCHIERI, ANDREA MOREIRA MONTEIRO, RICARDO ELGUL SAMAD, AMANDO SIUITI ITO, ANTONIO MARTINS FIGUEIREDO NETO, NILSON DIAS VIEIRA JR, MAGNUS GIDLUND, and LILIA CORONATO COURROL*


In this paper we report the effects of the irradiation of low-density lipoprotein (LDL) by ultra-short laser pulses to obtain in vitro alterations mimicking proatherogenic modifications occurring in vivo in LDL. The modifications by metallic ions (copper and iron) and ultra-short laser pulses were studied by fluorescence steady state and time-resolved lifetime measurements. The results demonstrate that the modifications caused by ultra-short laser pulses and by iron affect the tryptophan residues of apolipoprotein B-100 (Apo-B), slightly decreasing fluorescent lifetimes, with almost no modifications in pre-exponential factors, indicating preservation of structural properties around the fluorophore. On the other hand, oxidation by copper strongly affects the Apo-B protein associated with LDL. We describe a fast, inexpensive, and nondestructive fluorescence-based method that is readily accessible to provide the LDL particle characterization.



Index Headings: Low-density lipoprotein (LDL); Time-resolved fluorescence; Tryptophan; Ultra-short pulsed laser.