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排序方式: 共有356条查询结果,搜索用时 15 毫秒
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Scott T. R. Walsh Hong Cheng James W. Bryson Heinrich Roder William F. DeGrado 《Proceedings of the National Academy of Sciences of the United States of America》1999,96(10):5486-5491
Although de novo protein design is an important endeavor with implications for understanding protein folding, until now, structures have been determined for only a few 25- to 30-residue designed miniproteins. Here, the NMR solution structure of a complex 73-residue three-helix bundle protein, alpha3D, is reported. The structure of alpha3D was not based on any natural protein, and yet it shows thermodynamic and spectroscopic properties typical of native proteins. A variety of features contribute to its unique structure, including electrostatics, the packing of a diverse set of hydrophobic side chains, and a loop that incorporates common capping motifs. Thus, it is now possible to design a complex protein with a well defined and predictable three-dimensional structure. 相似文献
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Total radical trapping antioxidant potential (TRAP) and exercise 总被引:1,自引:0,他引:1
Sharpe PC; Duly EB; MacAuley D; McCrum EE; Mulholland C; Stott G; Boreham CA; Kennedy G; Evans AE; Trinick TR 《QJM : monthly journal of the Association of Physicians》1996,89(3):223-228
The relationship between physical activity, physical fitness and total
radical trapping antioxidant potential (TRAP) was examined in the Northern
Ireland Health and Activity Survey. This was a cross-sectional population
study (n = 1600) using a two-stage probability sample of the population.
TRAP was calculated using the sum of the individual serum antioxidant
concentrations (urate, protein thiols, ascorbate, alpha tocopherol and
bilirubin) multiplied by their respective stoichiometric values. Physical
fitness was determined by estimation of VO2max by extrapolation from
submaximal oxygen uptake, and physical activity was recorded by
computer-assisted interview. Mean serum TRAP concentrations were
significantly higher in males (653 +/- 8.2 mumol/l, mean +/- SEM) compared
to females (564 +/- 8.0 mumol/l) (p < 0.0001). Both male and female
smokers had significantly lower TRAP values than non-smokers (males p <
0.0001, females p = 0.02). In females, there was a positive relationship of
TRAP with age (p < 0.001) and body mass index (p < 0.001) but a
negative relationship with physical fitness (p < 0.05). The known
beneficial effects of exercise and activity do not appear to be directly
mediated through increased antioxidant status.
相似文献
36.
An experimental model of chronic myocardial hibernation 总被引:9,自引:0,他引:9
St Louis JD Hughes GC Kypson AP DeGrado TR Donovan CL Coleman RE Yin B Steenbergen C Landolfo KP Lowe JE 《The Annals of thoracic surgery》2000,69(5):1351-1357
BACKGROUND: Hibernating myocardium describes persistently impaired ventricular function at rest caused by reduced coronary blood flow. However, a realistic animal model reproducing this chronic ischemic state does not exist. The purpose of this study was to explore whether chronic low-flow hibernation could be produced in swine. METHODS: Miniswine underwent 90% stenosis of the left circumflex coronary artery. Positron emission tomography and dobutamine stress echocardiography were performed 3 and 30 days (n = 6) or 14 days (n = 4) after occlusion to evaluate myocardial blood flow and viability. Triphenyl tetrazolium chloride assessed percent infarction. Electron microscopy was used to identify cellular changes characteristic of hibernating myocardium. RESULTS: Positron emission tomography (13N-labeled-ammonia) 3 days after occlusion demonstrated a significant reduction in myocardial blood flow in the left circumflex distribution. This reduced flow was accompanied by increased glucose use (18F-fluorodeoxyglucose), which is consistent with hibernating myocardium. Thirty days after occlusion, positron emission tomography demonstrated persistent low flow with increased glucose use in the left circumflex distribution. Dobutamine stress echocardiography 3 days after occlusion demonstrated severe hypocontractility at rest in the left circumflex region. Regional wall motion improved with low-dose dobutamine followed by deterioration at higher doses (biphasic response), findings consistent with hibernating myocardium. The results of dobutamine stress echocardiography were unchanged 30 days after occlusion. Triphenyl tetrazolium chloride staining (n = 6) revealed a mean of 8% +/- 2% infarction of the area-at-risk localized to the endocardial surface. Electron microscopy (n = 4) 14 days after occlusion demonstrated loss of contractile elements and large areas of glycogen accumulation within viable cardiomyocytes, also characteristic of hibernating myocardium. CONCLUSIONS: Chronic low-flow myocardial hibernation can be reproduced in an animal model after partial coronary occlusion. This model may prove useful in the study of the mechanisms underlying hibernating myocardium and the use of therapies designed to improve blood flow to the heart. 相似文献
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健康人通过体内胰岛素的分泌调节,可以保持正常的血糖水平。各种外源性胰岛素制剂在代谢过程上总是尽可能地模拟内源性胰岛素的分泌动力学。理想的外源性基础胰岛素制剂可以模拟健康人的基础胰岛素分泌,以致使用者可以恢复两餐之间和夜间正常生理情况下的血浆胰岛素水平。 相似文献
40.
Fang C Senes A Cristian L DeGrado WF Hochstrasser RM 《Proceedings of the National Academy of Sciences of the United States of America》2006,103(45):16740-16745
The tertiary interactions between amide-I vibrators on the separate helices of transmembrane helix dimers were probed by ultrafast 2D vibrational photon echo spectroscopy. The 2D IR approach proves to be a useful structural method for the study of membrane-bound structures. The 27-residue human erythrocyte protein Glycophorin A transmembrane peptide sequence: KKITLIIFG(79)VMAGVIGTILLISWG(94)IKK was labeled at G(79) and G(94) with (13)C=(16)O or (13)C=(18)O. The isotopomers and their 50:50 mixtures formed helical dimers in SDS micelles whose 2D IR spectra showed components from homodimers when both helices had either (13)C=(16)O or (13)C=(18)O substitution and a heterodimer when one had (13)C=(16)O substitution and the other had (13)C=(18)O substitution. The cross-peaks in the pure heterodimer 2D IR difference spectrum and the splitting of the homodimer peaks in the linear IR spectrum show that the amide-I mode is delocalized across a pair of helices. The excitation exchange coupling in the range 4.3-6.3 cm(-1) arises from through-space interactions between amide units on different helices. The angle between the two Gly(79) amide-I transition dipoles, estimated at 103 degrees from linear IR spectroscopy and 110 degrees from 2D IR spectroscopy, combined with the coupling led to a structural picture of the hydrophobic interface that is remarkably consistent with results from NMR on helix dimers. The helix crossing angle in SDS is estimated at 45 degrees. Two-dimensional IR spectroscopy also sets limits on the range of geometrical parameters for the helix dimers from an analysis of the coupling constant distribution. 相似文献