Mapping Site-Specific Changes that Affect Stability of the NTerminal Domain of Calmodulin

Biophysical tools have been invaluable in formulating therapeutic proteins. These tools characterize protein stability rapidly in a variety of solution conditions, but in general, the techniques lack the ability to discern site-specific information to probe how solution environment acts to stabilize or destabilize the protein. NMR spectroscopy can provide site-specific information about subtle structural changes of a protein under different conditions, enabling one to assess the mechanism of protein stabilization. In this study, NMR was employed to detect structural perturbations at individual residues as a result of altering pH and ionic strength. The N-terminal domain of calmodulin (N-CaM) was used as a model system, and the 1H-15N heteronuclear single quantum coherence (HSQC) experiment was used to investigate effects of pH and ionic strength on individual residues. NMR analysis revealed that different solution conditions affect individual residues differently, even when the amino acid sequence and structure are highly similar. This study shows that addition of NMR to the formulation toolbox has the ability to extend understanding of the relationship between site-specific changes and overall protein stability

A Multicenter Trial of Two Dexamethasone Regimens in Ventilator-Dependent Premature Infants

Many neonatologists treat premature infants who cannot be weaned from ventilator support with dexamethasone to improve pulmonary compliance and facilitate extubation. 1 – 4 Overall, however, these apparent short-term benefits of dexamethasone therapy are not reflected in a substantial decrease in the duration of oxygen therapy, the length of hospital stay, or later pulmonary morbidity. 4 – 8 In addition, some treated infants may have glucose intolerance and hypertension while receiving dexamethasone. 1 , 2 , 4 Treating ventilator-dependent premature infants shortly after birth with dexamethasone may mitigate acute lung injury and reduce the incidence of chronic lung disease. 9 – 13 However, the risks of starting dexamethasone at . .