3 research outputs found
How Accurate Is the Egg-Box Model in Describing the Binding of Calcium to Polygalacturonate? A Molecular Dynamics Simulation Study
We performed molecular dynamics (MD)
simulations of octameric
galacturonate,
GalA8, chains in the presence of Ca2+ in a ratio
of R = [Ca2+]/[GalA] = 0.25 in order to
determine to which extent the popular âegg-box modelâ
(EBM) is able to describe the association between Ca2+ cations
and polygalacturonate (polyGalA) chains. To this aim, we slightly
revised the empirical parameters for the interaction between Ca2+ and the carboxylate oxygen atoms of GalA units so as to
reproduce the experimental Ca2+âGalA association
constant. We also defined an ad hoc order parameter, referred to as
the egg-box score (EBS), that quantifies any deviation of the local
coordination geometry of calcium cations with respect to an âidealâ
EBM coordination geometry. The results reveal that the local coordination
geometry of Ca2+ cations bound to polyGalA chains differs
from that of the EBM. Moreover, polyGalA chains exhibit significant
conformational disorder, and the cross-link angles formed between
polyGalA chain axes are broadly distributed. Overall, the present
study suggests that the EBM fails to describe accurately the association
modes between calcium and polyGalA chains at a molar ratio R of 0.25
How Accurate Is the Egg-Box Model in Describing the Binding of Calcium to Polygalacturonate? A Molecular Dynamics Simulation Study
We performed molecular dynamics (MD)
simulations of octameric
galacturonate,
GalA8, chains in the presence of Ca2+ in a ratio
of R = [Ca2+]/[GalA] = 0.25 in order to
determine to which extent the popular âegg-box modelâ
(EBM) is able to describe the association between Ca2+ cations
and polygalacturonate (polyGalA) chains. To this aim, we slightly
revised the empirical parameters for the interaction between Ca2+ and the carboxylate oxygen atoms of GalA units so as to
reproduce the experimental Ca2+âGalA association
constant. We also defined an ad hoc order parameter, referred to as
the egg-box score (EBS), that quantifies any deviation of the local
coordination geometry of calcium cations with respect to an âidealâ
EBM coordination geometry. The results reveal that the local coordination
geometry of Ca2+ cations bound to polyGalA chains differs
from that of the EBM. Moreover, polyGalA chains exhibit significant
conformational disorder, and the cross-link angles formed between
polyGalA chain axes are broadly distributed. Overall, the present
study suggests that the EBM fails to describe accurately the association
modes between calcium and polyGalA chains at a molar ratio R of 0.25
Thermal Denaturation of Pea Globulins (<i>Pisum sativum</i> L.)îžMolecular Interactions Leading to Heat-Induced Protein Aggregation
The heat-induced denaturation and aggregation of mixed
pea globulins
(8%, w/w) were investigated using differential scanning calorimetry
(DSC), SDS-PAGE, and size-exclusion chromatography (SEC-HPLC). DSC
data showed that the pea proteins denaturation temperature (<i>T</i><sub>d</sub>) was heating-rate dependent. The <i>T</i><sub>d</sub> value decreased by about 4 °C by lowering the heating
rate from 10 to 5 °C/min. The SDS-PAGE analysis revealed that
protein denaturation upon heating at 90 °C was mainly governed
by noncovalent interaction. The SEC-HPLC measurements indicated that
low-denatured legumin (â350â410 kDa) and vicilin/convicilin
(â170 kDa) globulins were heat-denatured and most of their
subunits reassociated into high-molecular weight, soluble aggregates
(>700 kDa). The addition of <i>N</i>-ethylmaleimide slightly
modified the aggregation route of pea globulins. However, partially
insoluble macroaggregates were produced in the presence of dithiothreitol,
reflecting the stabilizing effect of disulfide bonds within legumin
subunits