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Fig. 12. Breaking of the S-S bridge of the P0 protein. The effect of heat and mercap-
toethanol (5% v/v) on P0 protein in SDS-15%PAGE. Signifies the MW standards. P0 indi-
cates the P0 protein eluted from the Cu2+-IMAC column. B stands for prestained
SDS-PAGE Standards, Low Range (Bio-Rad, Hercules, Ca, USA). From top: phosphory-
lase B, bovine serum albumin, ovalbumin, carbonic anhydrase, soybean tyrosine inhibitor
and lysozyme. The rationale for including prestained proteins was to check the influence of
mercaptoethanol, heat, and prestaining on their electrophoretic behavior. The prestaining of
proteins evidently inhibits electrophoretic migration of protein and abolishes staining with
the Coomassie Brilliant Blue R-250. +ME, mercaptoethanol (5% v/v), was included to
reduce the SDS sample buffer, HEAT — before electrophoresis samples were heated at
95°C, for 10 minutes. The MW of P0 increases approximately 3 kDa when mercaptoethanol
is included in the SDS reducing buffer. Heating promotes excessive aggregation of myelin
proteins (<>); they do not enter the 15% polyacrylamide gel. As the molecular weight of
P0 solubilized in neutral detergents is similar to the MW of protein in the presence of mer-
captoethanol, we conclude that neutral detergents may oxidize P0 as well. SDS seems to
prevent the oxidizing of P0. Purified P0 seems to be folded and most likely resembles the
native conformation in the myelin membrane. This is the most suitable state when crystal-
lizing P0. (Reproduced with permission from Neurochem Res , 24 (6), (1999) 723-732.)
(Van Gunsteren et al ., 1996; Van Gunsteren, Karplus, 1980). The rule is
that the molecule (or model) is energetically more stable when its energy
of interaction is at a lower level. The P0_Ex_A model (Fig. 10(A)) is ener-
getically the most stable because its energy is equal to
4730.677 kJ/mol
(kilojoule per mol), the lowest of all the compared models (Fig. 11). Any
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