To probe the potential for enzymatic activity in unevolved amino acid sequence space, we created a combinatorial library of de novo 4-helix bundle proteins. This collection of novel proteins can be considered an ''artificial superfamily'' of helical bundles. The superfamily of 102-residue proteins was designed using binary patterning of polar and nonpolar residues, and expressed in Escherichia coli from a library of synthetic genes. Sequences from the library were screened for a range of biological functions including heme binding and peroxidase, esterase, and lipase activities. Proteins exhibiting these functions were purified and characterized biochemically. The majority of de novo proteins from this superfamily bound the heme cofactor, and a sizable fraction of the proteins showed activity significantly above background for at least one of the tested enzymatic activities. Moreover, several of the designed 4-helix bundles proteins showed activity in all of the assays, thereby demonstrating the functional promiscuity of unevolved proteins. These studies reveal that de novo proteins-which have neither been designed for function, nor subjected to evolutionary pressure (either in vivo or in vitro)-can provide rudimentary activities and serve as a ''feedstock'' for evolution.

Our results suggest that PEEP can be applied safely in patients with acute brain injury as it does not have a clinically significant effect on ICP or CPP. Further prospective studies are required to assess the safety of applying a lung protective ventilation strategy in brain-injured patients with lung injury.

Rationale: Neurocognitive outcome after out-of-hospital cardiac arrest (OHCA) is often poor, even when initial resuscitation succeeds. Lower tidal volumes (VTs) attenuate extrapulmonary organ injury in other disease states and are neuroprotective in preclinical models of critical illness.Objective: To evaluate the association between VT and neurocognitive outcome after OHCA.Methods: We performed a propensity-adjusted analysis of a twocenter retrospective cohort of patients experiencing OHCA who received mechanical ventilation for at least the first 48 hours of hospitalization. VT was calculated as the time-weighted average over the first 48 hours, in milliliters per kilogram of predicted body weight (PBW). The primary endpoint was favorable neurocognitive outcome (cerebral performance category of 1 or 2) at discharge.Measurements and Main Results: Of 256 included patients, 38% received time-weighted average VT greater than 8 ml/kg PBW during the first 48 hours. Lower VT was independently associated with favorable neurocognitive outcome in propensityadjusted analysis (odds ratio, 1.61; 95% confidence interval [CI], 1.13-2.28 per 1-ml/kg PBW decrease in VT; P = 0.008). This finding was robust to several sensitivity analyses. Lower VT also was associated with more ventilator-free days (b = 1.78; 95% CI, 0.39-3.16 per 1-ml/kg PBW decrease; P = 0.012) and shockfree days (b = 1.31; 95% CI, 0.10-2.51; P = 0.034). VT was not associated with hypercapnia (P = 1.00). Although the propensity score incorporated several biologically relevant covariates, only height, weight, and admitting hospital were independent predictors of VT less than or equal to 8 ml/kg PBW.Conclusions: Lower VT after OHCA is independently associated with favorable neurocognitive outcome, more ventilator-free days, and more shock-free days. These findings suggest a role for low-VT ventilation after cardiac arrest.

Increasing systolic blood pressure variability was associated with 30-day mortality and development of renal failure, with surgery phase-specific relationships observed. Further research is required to determine how to prospectively detect blood pressure variability and elucidate opportunities for intervention.