BRUNO, O. M.

FALVO, M.

GUIMARÃES, F. E. G.

MILORI, D. M. B. P.

MOUNIER, S.

OHANA, N.

TADINI, A.

VILLAS BOAS, P. R.

English

Repository Open Access to Scientific Information from Embrapa

CONTROL ID: 2559618CONTACT (NAME ONLY): Debora MiloriAbstract Details  PRESENTATION TYPE: No PreferenceCURRENT SYMPOSIUM: PM3: Science-Enabled Advances in Materials- and Manufacturing-TechnologiesKEYWORDS: Properties/Radiation/luminescence, Composition & Microstructure/Bulk Techniques/spectroscopy,Performance/Functionality/optical. Abstract  TITLE: Fractal behavior of Humic Substances evaluated by Confocal laser scanning microscopy (CLSM) andFluorescence Lifetime ImagingAUTHORS (FIRST NAME, LAST NAME): Debora M Bastos Pereira Milori1, Stephane   Mounier2, Paulino  RibeiroVillas-Boas1, Amanda  Tadini1, 3, Nayre  Ohana1, 3, Mauricio   Falvo4, Odemir  Martinez  Bruno4, FranciscoEduardo Gontijo Guimaraes4INSTITUTIONS (ALL): 1. Embrapa Instrumentation, Sao Carlos, Brazil.2. University of Toulon, Toulon, France.3. Sao Carlos Institute of Chemistry , University of Sao Paulo, Sao Carlos, Brazil.4. Sao Carlos Institute  of Physics, University of Sao Paulo, Sao Carlos, Brazil.ABSTRACT BODY: Abstract Body: Humic substances (HS) are major components of the natural organic matter (NOM) in soil and water.Particularly, HS affect the chemistry, cycling and bioavailability of chemical elements in soil. Regarding their structure,they are complex and heterogeneous mixtures of polydispersed materials formed by biochemical and chemicalreactions during the decay and transformation of plant and microbial remains (a process called humification). Plantlignin and its transformation products, as well as polysaccharides, proteins, lipids, nucleic acids, etc., are importantcomponents taking part in this process. HS are highly chemically reactive, yet recalcitrant with respect tobiodegradation. Humic substances can interact with several nutrients and toxic metals, which can be more available toorganisms or actually sequestered so as to reduce their toxicity or beneficial value. The mechanisms of many of theseinteractions are unclear. That is a result of our lack of knowledge of the structural components of humic substances. Inaddition, HS are efficient fluorescent materials and can be divided into three main fractions: humic acids (HA), fulvicacids (FA) and humin. Fulvic acids are soluble in water at all pH; HA are insoluble at low pH and Humin is insoluble atall pH values. Fractal theory has been considered an alternative tool to explain the conformation of molecularaggregates. The presence of fractal models indicates that the system may be decomposed in parts, each part being acopy of the whole. In the present work, a drop of different HS materials was dried on a glass surface and itssuspended molecules were deposited in a typical dendritic-like fashion during the evaporation process. Confocal laserscanning microscopy (CLSM), equipped with spectral analysis, Fluorescence Lifetime Imaging (FLIM) and two-photon(2P) excitation, was employed to quantify the formation of dendritic deposits in real time and to access a new varietyof HS fluorescence states related to structural changes and molecular aggregation. Image methodologies weredeveloped to enhance the viewing of fractal patterns, and observe variations in HS concentration and organizationalong the area of the original drop, with features that cannot be perceived in a usual image analysis. The fluorescencespectral shape and position correlate well to HS concentration, to the HA or FA fraction and to the fractal morphology.The fluorescence decay time became longer with the decrease HS aggregates along the dendritic structures, whichcorresponds to HS emission and decay time features in a less concentrated environment. These results suggest thatHS arrangement in such fractal structures is based on a well-organized environment that ensures different level ofinteraction between the molecules. In addition, the variety of HS fluorescence states accessed by two-photonexcitation can allow an even broader optical characterization of soil materials and their fractal properties.

Fractal behavior of humic substances evaluated by confocal laser scanning microscopy (CLSM) and fluorescence lifetime imaging.

http://www.alice.cnptia.embrapa.br/bitstream/doc/1079903/1/PFractalbehaviorofhumic....pdf

Fractal behavior of humic substances evaluated by confocal laser scanning microscopy (CLSM) and fluorescence lifetime imaging.

Abstract

Similar works

Full text

Available Versions

Repository Open Access to Scientific Information from Embrapa