Macromolecular dimensions and mechanical properties of monolayer films of Sonorean mesquite gum.
Mesquite gum sourced from Prosopis velutina trees and gum arabic (Acacia spp.) were characterized using light scattering and Langmuir isotherms. Both gum materials were fractionated by hydrophobic interaction chromatography, yielding four fractions for both gums: FI, FIIa, FIIb and FIII in mesquite gum and FI, FII, FIIIa and FIIIb in gum arabic. In mesquite gum, the obtained fractions had different protein content (7.18-38.60 wt.-%) and macromolecular dimensions (M approximately 3.89 x 10(5)-8.06 x 10(5) g.mol(-1), RG approximately 48.83-71.11 nm, RH approximately 9.61-24.06 nm) and architecture given by the structure factor (RG/RH ratio approximately 2.96-5.27). The mechanical properties of Langmuir monolayers at the air-water interface were very different on each gum and their fractions. For mesquite gum, the most active species at the interface were those comprised in Fractions IIa and IIb and III, while Fraction I the pi/A isotherm lied below that of the whole gum. In gum arabic only Fraction III developed greater surface pressure at the same surface per milligram of material than whole gum. This is rationalized in terms of structural differences in both materials. Mesquite gum tertiary structure seems to fit best with an elongated polydisperse macrocoil in agreement with the "twisted hairy rope" proposal for arabinogalactan proteoglycans.
Laboratory of Biopolymers, Centro de Investigación en Alimentación y Desarrollo, A.C. (C.I.A.D., A.C.) P.O. Box 1735 Hermosillo, Sonora, 83000, Mexico.
Yolanda L
YL
López-Franco
Miguel A
MA
Valdez
Javier
J
Hernández
Ana M
AM
Calderón de la Barca
Marguerite
M
Rinaudo
Francisco M
FM
Goycoolea
D002241:Carbohydrates / Q000737:chemistry; D002845:Chromatography; D005685:Galactans / Q000737:chemistry; D006170:Gum Arabic / Q000737:chemistry*; D008027:Light; D015233:Models, Statistical; D012542:Scattering, Radiation; D013314:Stress, Mechanical; D013696:Temperature; D013997:Time Factors; D014466:Ultraviolet Rays
D002241:Carbohydrates; D005685:Galactans; D006170:Gum Arabic; C005653:arabinogalactan