Gender muscle recovery during isokinetic exercise.

The purpose of this study was to examine the effect of two between set rest intervals (RI) on isokinetic knee extension peak torque (PT) produced by sedentary women and men. Seventeen young women (27.18 ± 4.05 yrs) and 16 young men (26.75 ± 4.73 yrs) performed 3 sets of 10 unilateral isokinetic knee extension at 60° and 180°/s. The RI between sets was 60 and 120 s, counterbalanced across 2 testing days. Statistical evaluation of the data was performed using a 3-way mixed factor ANOVA (gender x rest interval x sets). Males and females exhibited decreases (p<0.05) in PT with 120 s RI at 60°/s. There was no significant decline in PT in the female group during both RI at 180°/s. Men showed a significant decrease in PT only with 60 s RI. Young women and men require more than 120 s of RI to recover full PT at 60°/s. However, full quadriceps's muscle strength recovery can be attained with a 60 and 120 s at 180°/s in women, but in men only with a 120 s at the same velocity.

The hydrophobic nature of GroEL-substrate binding.

The molecular chaperone GroEl from Escherichia coli is a member of the highly conserved Hsp60 family of proteins that facilitates protein folding. A central question regarding the mechanism of GroEL-assisted refolding of proteins concerns its broad substrate specificity. The nature of GroEL-polypeptide chain interaction was investigated by isothermal titration calorimetry using proteins that maintain a non-native conformation in neutral buffer solutions. A single molecule of an unfolded variant of subtilisin BPN' binds non-cooperatively to GroEL with micromolar affinity and a positive enthalpy change. Additional calorimetric titrations of this chain with GroEL show that the positive enthalpy change decreases with increasing temperature between 6 and 25 degrees C, yielding a delta CP of -0.85 kcal mol-1 degree-1. alpha-Casein similarly binds to GroEL with micromolar affinity and a positive enthalpy change in the range of 15-20 degrees C, yielding a delta CP of -0.44 kcal mol-1 degree-1. The negative heat capacity change provides strong evidence for the role of hydrophobic interactions as the driving force for the association of these substrates with the GroEL chaperonin.