Current Considerations in the Diagnosis and Treatment of Circadian Rhythm Sleep-Wake Disorders in Children.

Circadian Rhythm Sleep-Wake Disorders (CRSWDs) are important sleep disorders whose unifying feature is a mismatch between the preferred or required times for sleep and wakefulness and the endogenous circadian drives for these. Their etiology, presentation, and treatment can be different in pediatric patients as compared to adults. Evaluation of these disorders must be performed while viewed through the lens of a patient's comorbid conditions. Newer methods of assessment promise to provide greater diagnostic clarity and critical insights into how circadian physiology affects overall health and disease states. Effective clinical management of CRSWDs is multimodal, requiring an integrated approach across disciplines. Therapeutic success depends upon appropriately timed nonpharmacologic and pharmacologic interventions. A better understanding of the genetic predispositions for and causes of CRSWDs has led to novel clinical opportunities for diagnosis and improved therapeutics.

Bioproduction and characterization of a pH responsive self-assembling peptide.

Peptide P(11)-4 (QQRFEWEFEQQ) was designed to self-assemble to form beta-sheets and nematic gels in the pH range 5-7 at concentrations > or =12.6 mM in water. This self-assembly is reversibly controlled by adjusting the pH of the solvent. It can also self-assemble into gels in biological media. This together with its biocompatibility and biodegradability make P(11)-4 an attractive building block for the fabrication of nanoscale materials with uses in, for example, tissue engineering. A limitation to large-scale production of such peptides is the high cost of solid phase chemical synthesis. We describe expression of peptide P(11)-4 in the bacterium Escherichia coli from constructs carrying tandem repeats of the peptide coding sequence. The vector pET31b+ was used to express P(11)-4 repeats fused to the ketosteroid isomerase protein which accumulates in easily recoverable inclusion bodies. Importantly, the use of auto-induction growth medium to enhance cell density and protein expression levels resulted in recovery of 2.5 g fusion protein/L culture in both shake flask and batch fermentation. Whole cell detergent lysis allowed recovery of inclusion bodies largely composed of the fusion protein. Cyanogen bromide cleavage followed by reverse phase HPLC allowed purification of the recombinant peptide with a C-terminal homoserine lactone (rP(11)-4(hsl)). This recombinant peptide formed pH dependent hydrogels, displayed beta-structure measured by circular dichroism and fibril formation observed by transmission electron microscopy.