Browsing by Author "Chen, E"

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Open Access
Short-lived alpha-helical intermediates in the folding of beta-sheet proteins.
(Biochemistry, 2010-07-06) Chen, E; Everett, ML; Holzknecht, ZE; Holzknecht, RA; Lin, SS; Bowles, DE; Parker, W
Several lines of evidence point strongly toward the importance of highly alpha-helical intermediates in the folding of all globular proteins, regardless of their native structure. However, experimental refolding studies demonstrate no observable alpha-helical intermediate during refolding of some beta-sheet proteins and have dampened enthusiasm for this model of protein folding. In this study, beta-sheet proteins were hypothesized to have potential to form amphiphilic helices at a period of <3.6 residues/turn that matches or exceeds the potential at 3.6 residues/turn. Hypothetically, such potential is the basis for an effective and unidirectional mechanism by which highly alpha-helical intermediates might be rapidly disassembled during folding and potentially accounts for the difficulty in detecting highly alpha-helical intermediates during the folding of some proteins. The presence of this potential was confirmed, indicating that a model entailing ubiquitous formation of alpha-helical intermediates during the folding of globular proteins predicts previously unrecognized features of primary structure. Further, the folding of fatty acid binding protein, a predominantly beta-sheet protein that exhibits no apparent highly alpha-helical intermediate during folding, was dramatically accelerated by 2,2,2-trifluoroethanol, a solvent that stabilizes alpha-helical structure. This observation suggests that formation of an alpha-helix can be a rate-limiting step during folding of a predominantly beta-sheet protein and further supports the role of highly alpha-helical intermediates in the folding of all globular proteins.
Open Access
Treatment of isolated cervical facet fractures: A systematic review
(Journal of Neurosurgery: Spine, 2016-02-01) Kepler, CK; Vaccaro, AR; Chen, E; Patel, AA; Ahn, H; Nassr, A; Shaffrey, CI; Harrop, J; Schroeder, GD; Agarwala, A; Dvorak, MF; Fourney, DR; Wood, KB; Traynelis, VC; Yoon, ST; Fehlings, MG; Aarabi, B
OBJECTIVE: In this clinically based systematic review of cervical facet fractures, the authors' aim was to determine the optimal clinical care for patients with isolated fractures of the cervical facets through a systematic review. METHODS: A systematic review of nonoperative and operative treatment methods of cervical facet fractures was performed. Reduction and stabilization treatments were compared, and analysis of postoperative outcomes was performed. MEDLINE and Scopus databases were used. This work was supported through support received from the Association for Collaborative Spine Research and AOSpine North America. RESULTS: Eleven studies with 368 patients met the inclusion criteria. Forty-six patients had bilateral isolated cervical facet fractures and 322 had unilateral isolated cervical facet fractures. Closed reduction was successful in 56.4% (39 patients) and 63.8% (94 patients) of patients using a halo vest and Gardner-Wells tongs, respectively. Comparatively, open reduction was successful in 94.9% of patients (successful reduction of open to closed reduction OR 12.8 [95% CI 6.1-26.9], p < 0.0001); 183 patients underwent internal fixation, with an 87.2% success rate in maintaining anatomical alignment. When comparing the success of patients who underwent anterior versus posterior procedures, anterior approaches showed a 90.5% rate of maintenance of reduction, compared with a 75.6% rate for the posterior approach (anterior vs posterior OR 3.1 [95% CI 1.0-9.4], p = 0.05). CONCLUSIONS: In comparison with nonoperative treatments, operative treatments provided a more successful outcome in terms of failure of treatment to maintain reduction for patients with cervical facet fractures. Operative treatment appears to provide superior results to the nonoperative treatments assessed.