Effect of polysaccharide capsule of the microalgae Staurastrum iversenii var. americanum on diffusion of charged and uncharged molecules, using EPR technique

Effect of polysaccharide capsule of the microalgae Staurastrum iversenii var. americanum on diffusion of charged and uncharged molecules, using EPR technique

Author Freire-Nordi, Cristina Souza Autor UNIFESP Google Scholar
Vieira, Armando A. H. Google Scholar
Nakaie, Clovis Ryuichi Autor UNIFESP Google Scholar
Nascimento, Otaciro R. Google Scholar
Institution Universidade de São Paulo (USP)
Universidade Federal de São Carlos Departamento de Botânica
Universidade Federal de São Paulo (UNIFESP)
Abstract The existence of a mucilaginous envelope, sheath or capsule is usual in many desmids, but few data concerning its function are available. Previous studies of the transport function and permeation of molecules through the algae capsules were done using the algae Spondylosium panduriforme and Nephrocytium lunatum, the Electron Paramagnetic Resonance (EPR) technique, and different spin labels. The results suggested that the capsule functions as a selective diffusion medium. In the present work charged and uncharged molecules (spin labels group A) and Staurastrum iversenii var. americanum (Desmids),whose alga presents a great mucilaginous capsule, were used. Charged nitroxide molecules similar to amino acids (spin labels group B) were also used allowing a better understanding of the electrostatic effect in the permeation process across the capsule. The role of the cell capsule in the solute diffusion was evaluated by determining the capsulated and decapsulated cell permeation times. The permeation times for all spin labels tested in the cells lacking capsules were always shorter than those containing this physical barrier. The decay times of spin labels group A observed for S. iversenii were compared to other studied algae. The results regarding the diffusion of charged spin labels group B suggested that the interaction of cell capsule occurs more strongly with negatively charged molecules than with positively charged ones. The results obtained in this work with spin labels group A confirm that the capsule is an essential structure for the cell, and that due to the polar interactions with the spin labels, it plays an important role in the selection of small molecules. Several parameters, mainly those of electrostatic nature, seem to control the permeation across the algal capsules of spin labels group B, showing that structures which are similar to amino acids could diffuse across the interior of the algal cell.
Keywords EPR
Algae capsules
Language English
Sponsor Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)
Date 2006-03-01
Published in Brazilian Journal of Physics. Sociedade Brasileira de Física, v. 36, n. 1a, p. 75-82, 2006.
ISSN 0103-9733 (Sherpa/Romeo, impact factor)
Publisher Sociedade Brasileira de Física
Extent 75-82
Origin http://dx.doi.org/10.1590/S0103-97332006000100013
Access rights Open access Open Access
Type Article
Web of Science ID WOS:000236325500014
SciELO ID S0103-97332006000100013 (statistics in SciELO)
URI http://repositorio.unifesp.br/handle/11600/2945

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