No abstract

Where applicable, text in italics describes the underlying philosophy of the requirements in that section. These philosophic statements are not program requirements and are therefore not citable. Note: Review Committees may further specify only where indicated by "The Review Committee may/must further specify."

Trimethylamine N-oxide (TMAO) and urea are two important osmolytes with their main significance to the biophysical field being in how they uniquely interact with proteins. Urea is a strong protein destabilizing agent, whereas TMAO is known to counteract urea's deleterious effects. The exact mechanisms by which TMAO stabilizes and urea destabilizes folded proteins continue to be debated in the literature. Although recent evidence has suggested that urea binds directly to amino acid side chains to make protein folding less thermodynamically favored, it has also been suggested that urea acts indirectly to denature proteins by destabilizing the surrounding hydrogen bonding water networks. Here, we elucidate the molecular level mechanism of TMAO's unique ability to counteract urea's destabilizing nature by comparing Raman spectroscopic frequency shifts to the results of electronic structure calculations of microsolvated molecular clusters. Experimental and computational data suggest that the addition of TMAO into an aqueous solution of urea induces blue shifts in urea's H-N-H symmetric bending modes, which is evidence for direct interactions between the two cosolvents.

No abstract

Objectives: To identify a group of ballistic tibia fractures, report the outcomes of these fractures, and compare them with both closed and open tibia fractures sustained by blunt mechanisms. We hypothesized that ballistic tibia fractures and blunt open fractures would have similar outcomes. Design: Retrospective cohort study. Setting: A single Level-1 trauma center. Patients/Participants: Adult patients presenting with ballistic (44), blunt closed (179), or blunt open (179) tibia fractures. Intervention: Intramedullary stabilization of tibia fracture. Main Outcomes: Unplanned reoperation, soft tissue reconstruction, nonunion, compartment syndrome, and fracture-related infection. Results: Compared with the blunt closed group, the ballistic fracture group required more operations (P < 0.01), had a higher occurrence of soft tissue reconstruction (P < 0.01), and higher incidence of compartment syndrome (P = 0.02). Ballistic and blunt closed groups did not significantly differ in rates of unplanned reoperation (P = 0.67), nonunion (11.4% vs. 4.5%, P = 0.08), or deep infection (9.1% vs. 5.6%, P = 0.49). In comparison to the blunt open group, the ballistic group required a similar number of operations (P = 0.12), had similar rates of unplanned reoperation (P = 0.10), soft tissue reconstruction (P = 0.56), nonunion (11.4% vs. 17.9%, P = 0.49), and fracture-related infection (9.1% vs. 10.1%, P = 1.0) but a higher incidence of compartment syndrome (15.9% vs. 5.0%, P = 0.02). Conclusions: Ballistic tibia fractures require more surgeries and have higher rates of soft tissue reconstruction than blunt closed fractures and seem to have outcomes similar to lower severity open fractures. We found a significantly higher rate of compartment syndrome in ballistic tibia fractures than both open and closed blunt fractures. When treating ballistic tibia fractures, surgeons should maintain a high level of suspicion for the development of compartment syndrome and counsel patients that ballistic tibia fractures seem to behave like an intermediate category between closed and open fractures sustained through blunt mechanisms. Level of Evidence: Prognostic Level III. See Instructions for Authors for a complete description of levels of evidence.