A chemoenzymatic route to chiral siloxanes

An approach employing two enzymes—toluene dioxygenase and immobilized lipase B from Candida antarctica (N435)—was explored as a potential biocatalytic method for the coupling of chiral diols with siloxane species. Analysis of reaction mixtures using1H NMR spectroscopy suggested that up to 66% consumption of the siloxane starting materials had occurred. Oligomeric species were observed and chiral products from the coupling of a cyclic diol with a siloxane molecule were isolated and characterized by MALDI-ToF MS and GPC. Immobilized lipases from Rhizomucor miehei and Thermomyces lanuginosus were also explored as potential catalysts for the coupling reactions, however, their use only returned starting material

Knee movement patterns of injured and uninjured adolescent basketball players when landing from a jump: A case-control study

BACKGROUND: A common knee injury mechanism sustained during basketball is landing badly from a jump. Landing is a complex task and requires good coordination, dynamic muscle control and flexibility. For adolescents whose coordination and motor control has not fully matured, landing badly from a jump can present a significant risk for injury. There is currently limited biomechanical information regarding the lower limb kinetics of adolescents when jumping, specifically regarding jump kinematics comparing injured with uninjured adolescents. This study reports on an investigation of biomechanical differences in landing patterns of uninjured and injured adolescent basketball players. METHODS: A matched case-control study design was employed. Twenty-two basketball players aged 14–16 years participated in the study: eleven previously knee-injured and eleven uninjured players matched with cases for age, gender, weight, height and years of play, and playing for the same club. Six high-speed, three-dimensional Vicon 370 cameras (120 Hz), Vicon biomechanical software and SAS Version 8 software were employed to analyse landing patterns when subjects performed a "jump shot". Linear correlations determined functional relationships between the biomechanical performance of lower limb joints, and paired t-tests determined differences between the normalised peak biomechanical parameters. RESULTS: The average peak vertical ground reaction forces between the cases and controls were similar. The average peak ground reaction forces between the cases and controls were moderately correlated (r = -0.47). The control (uninjured) players had significantly greater hip and knee flexion angles and significantly greater eccentric activity on landing than the uninjured cases (p < 0.01). CONCLUSION: The findings of the study indicate that players with a history of knee injuries had biomechanically compromised landing techniques when compared with uninjured players matched for gender, age and club. Descriptions (norms) of expected levels of knee control, proprioceptive acuity and eccentric strength relative to landing from a jump, at different ages and physical developmental stages, would assist clinicians and coaches to identify players with inappropriate knee performance comparable to their age or developmental stage

Synthesis of polyesters containing disiloxane subunits: Structural characterization, kinetics, and an examination of the thermal tolerance of Novozym-435

This paper reports the Novozym-435 mediated polymerization of disiloxane-containing polyester monomers under solvent-free conditions. The thermal tolerance of the immobilized enzyme was examined by conducting polymerization cycles over a temperature range of 35-150 °C. Increasing the temperature up to 100 °C afforded an increase in the apparent second order rate constant. Residual activity was measured using the production of octyl palmitate. The enzyme was shown to retain on average greater than 90% of its residual activity regardless of the polymerization temperature. This prompted a study of the long term thermal tolerance of the biocatalyst in which it was determined that over ten reaction cycles there was a significant decrease in the initial polymerization rate, but no change in the degree of monomer conversion after 24 h. The disiloxane containing polyesters were characterized using nuclear magnetic resonance spectroscopy and Fourier-transform infrared spectroscopy. Differential scanning calorimetry was used to determine the thermal properties of the disiloxane-containing polyesters. © 2012 Elsevier B.V. All rights reserved