Structure and dynamics of reconstituted cuticular waxes of grape berry cuticle (Vitis vinifera L.) |
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Authors: | Casado C; Heredia A |
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Institution: | Departamento de Bioquimica, Facultad de Ciencias, Universidad de Malaga, 29071 Malaga, Espana; Corresponding author e-mail: heredia@uma.es |
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Abstract: | Cuticular waxes from grape berry cuticle of Vitis
vinifera L. have been investigated by X-ray diffraction,
differential scanning calorimetry and gas chromatography. The waxes were
mainly composed of n-alcohols and
n-fatty acids and a considerable amount (about 30%) of
the cyclic terpenoid oleanolic acid. The physical techniques used showed
that the waxes have a high degree of molecular order in spite of the
presence of the cyclic component. Molecular dynamics of the reconstituted
waxes were measured to characterize the transport properties of the
cuticular waxes that form the transport-limiting barrier of plant cuticles.
For this purpose, the diffusion coefficient of labelled cholesterol,
imitating the terpenoic acid, was measured. The value obtained was around
10-21 m2
s-1 indicating a low mobility of the cyclic part of
the reconstituted waxes. Temperature dependence of the diffusion
coefficient was studied in the range of 5-45C. Arrhenius plot analysis yielded a high activation
energy, 196.4 kJ mol-1, of the diffusion process.
This indicates dense molecular packing of reconstituted cuticular
waxes. |
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