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Articles by Y. Liang
Total Records ( 6 ) for Y. Liang
  M Jiao , Y. L Zhou , H. T Li , D. L Zhang , J Chen and Y. Liang
 

The unfolding and refolding of two multidomain oxidoreductases, bovine liver catalase and flavoprotein bovine milk xanthine oxidase (XO), have been analyzed by fluorescence spectroscopy, circular dichroism, and activity measurements. Two intermediates, a partially folded active dimer disassembled from the native tetramer and a partially folded inactivated monomer, are found to exist in the conformational changes of catalase induced by guanidine hydrochloride (GdnHCl). Similarly, two intermediates, an active, compacted intermediate bound by flavin adenine dinucleotide (FAD) partially and an inactive flexible intermediate with FAD completely dissociated, exist in the conformational changes of XO induced by GdnHCl. The activity regains completely and an enhancement in activity compared with the native catalase or native XO is observed by dilution of catalase or XO incubated with GdnHCl at concentrations not >0.5 or 1.8 M into the refolding buffer, but the yield of reactivation for catalase or XO is zero when the concentration of GdnHCl is >1.5 or 3.0 M. The addition of FAD provides a remarkable protection against the inactivation of XO by GdnHCl under mild denaturing conditions, and the conformational change of XO is irreversible after FAD has been removed in the presence of a strong denaturing agent. These findings provide impetus for exploring the influences of cofactors such as FAD on the structure–function relationship of xanthine oxidoreductases.

  H. T Li , M Jiao , J Chen and Y. Liang
 

The structural integrity of the ubiquitous enzyme copper, zinc superoxide dismutase (SOD1) depends critically on the correct coordination of zinc and copper. We investigate here the roles of the stoichiometric zinc and copper ions in modulating the oxidative refolding of reduced, denatured bovine erythrocyte SOD1 at physiological pH and room temperature. Fluorescence experiment results showed that the oxidative refolding of the demetalated SOD1 (apo-SOD1) is biphasic, and the addition of stoichiometric Zn2+ into the refolding buffer remarkably accelerates both the fast phase and the slow phase of the oxidative refolding, compared with without Zn2+. Aggregation of apo-SOD1 in the presence of stoichiometric Zn2+ is remarkably slower than that in the absence of Zn2+. In contrast, the effects of stoichiometric Cu2+ on both the rates of the oxidative refolding and the aggregation of apo-SOD1 are not remarkable. Experiments of resistance to proteinase K showed that apo-SOD1 forms a conformation with low-level proteinase K resistance during refolding and stoichiometric Cu2+ has no obvious effect on the resistance to proteinase K. In contrast, when the refolding buffer contains stoichiometric zinc, SOD1 forms a compact conformation with high-level proteinase K resistance during refolding. Our data here demonstrated that stoichiometric zinc plays an important role in the oxidative refolding of low micromolar bovine SOD1 by accelerating the oxidative refolding, suppressing the aggregation during refolding, and helping the protein to form a compact conformation with high protease resistance activity.

  P Zhang , J Chen and Y. Liang
 

There is considerable interest in the interactions of ruthenium (Ru)(II) complexes with DNA as well as the biological impact of the interactions. Here, by using isothermal titration calorimetry, viscosity measurement, and circular dichroism, we investigated the interactions of a new Ru(II) complex, [Ru(dmp)2PMIP]2+{dmp = 2,9-dimethyl-1,10-phenanthroline, PMIP = 2-(4-methylphenyl)imidazo[4,5-f]1,10-phenanthroline}, with calf thymus DNA (CT DNA). The Ru(II) polypyridyl complex and CT DNA formed a tight 1:1 complex with a binding constant of exceeding 106 M–1 and with a binding mode of intercalation. Cell viability experiments indicated that the Ru(II) complex showed significant dose-dependent cytotoxicity to human lung tumor cell line A549. Further flow cytometry experiments showed that the cytotoxic Ru(II) complex induced apoptosis of human lung cancer cell line A549. Our data demonstrated that the Ru(II) polypyridyl complex binds to DNA and thereby induces apoptosis in tumor cells, suggesting that anti-tumor activity of the Ru(II) complex could be related to its interaction with DNA.

  F. Xu , Y. Wang , R. S. Ware , L. Ah Tse , D. W. Dunstan , Y. Liang , Z. Wang , X. Hong and N. Owen
  Aims  To investigate the joint influence of physical activity and family history of diabetes on the subsequent risk of developing hyperglycaemia and Type 2 diabetes among Chinese adults.

Methods  A prospective community-based cohort study was conducted among adults aged 35 years and older during 2004-2007 in Nanjing, China. Four communities (three urban and one rural) were randomly selected from 11 urban districts and two rural counties. Hyperglycaemia and Type 2 diabetes were defined using World Health Organization criteria based on fasting blood glucose concentration and physicians' diagnosis, respectively. Physical activity, parental diabetes history, and other important covariates were assessed at baseline and in the third-year follow-up survey.

Results  At study conclusion data were collected from 3031 participants (follow-up rate 81.3%). The 3-year cumulative incidence of hyperglycaemia and Type 2 diabetes was 6.2% and 2.4%, respectively. After adjustment for potential confounding variables, compared with those with positive family history and insufficient physical activity, the adjusted relative risk ratio (95% CI) of developing hyperglycaemia was 0.19 (0.02, 1.51) for participants with sufficient physical activity and a positive family history; 0.55 (0.31, 0.97) for participants with insufficient physical activity and a negative family history; and 0.36 (0.19, 0.70) for participants with sufficient physical activity but a negative family history. Participants who had a negative family history and insufficient physical activity were also less likely to develop Type 2 diabetes (RRR = 0.28; 0.14, 0.54), and participants with a negative family history and sufficient physical activity were the least likely to develop Type 2 diabetes (0.23; 0.10, 0.56).

Conclusions  Sufficient physical activity and negative family history of diabetes may jointly reduce the risk of developing hyperglycaemia and Type 2 diabetes in Chinese adults.

  Y. Liu , Y.-M. Yang , J. Zhu , H.-Q. Tan , Y. Liang and J.-D. Li
  Aims  To assess the prognostic impact of HbA1c and blood glucose level in patients with acute ST-segment elevation myocardial infarction and without diabetes. The relationship between HbA1c and acute hyperglycaemia was also explored.

Methods and results  We evaluated 4793 ST-segment elevation myocardial infarction patients with baseline HbA1c and three glucose measurements in the first 24 h. First, patients were stratified into quintiles by HbA1c and mean/admission glucose level. A total of 373 deaths (7.8%) occurred at 7 days, and 486 deaths (10.1%) occurred at 30 days. There were no significant differences in 7- and 30-day mortality, and major adverse cardiovascular event rates across HbA1c quintiles (< 34.4 mmol/mol (5.3% ), 34.4 to < 37.7 mmol/mol (5.6%), 37.7 to < 41.0 mmol/mol (5.9% ), 41.0 to < 47.5 mmol/mol (6.5%), and ≥ 47.5 mmol/mol; P for trend > 0.05). The risks of mortality and major adverse cardiovascular events were significantly increased in patients with higher glucose quintiles and lower quintile compared with the middle quintile after multivariable adjustment (P < 0.001). Patients were then reclassified into four groups according to mean/admission glucose and HbA1c levels. The group with elevated glucose and non-elevated HbA1c was associated with the highest mortality and major adverse cardiovascular event risk (P < 0.001).

Conclusions  Unlike acute hyperglycaemia, an elevated HbA1c level was not a risk factor for short-term outcomes in ST-segment elevation myocardial infarction patients without diabetes. Patients with acute hyperglycaemia and non-elevated HbA1c were associated with the worst prognosis. That suggests chronic glycaemic control/HbA1c level may help to recognize stress-induced hyperglycaemia and identify high-risk patients.

  Y. Liang , H. T. Gollany , R. W. Rickman , S. L. Albrecht , R. F. Follett , W. W. Wilhelm , J. M. Novak and C. L. Douglas
  Management of soil organic matter (SOM) is important for soil productivity and responsible utilization of crop residues for additional uses. CQESTR, pronounced "sequester," a contraction of "C sequestration" (meaning C storage), is a C balance model that relates organic residue additions, crop management, and soil tillage to SOM accretion or loss. Our objective was to simulate SOM changes in agricultural soils under a range of climate and management systems using the CQESTR model. Four long-term experiments (Champaign, IL, >100 yr; Columbia, MO, >100 yr; Lincoln, NE, 20 yr; Sidney, NE, 20 yr) in the United States under various crop rotations, tillage practices, organic amendments, and crop residue removal treatments were selected for their documented history of the long-term effects of management practice on SOM dynamics. CQESTR successfully simulated a substantial decline in SOM with 50 yr of crop residue removal under various rotations at Columbia and Champaign. The increase in SOM following addition of manure was simulated well; however, the model underestimated SOM for a fertilized treatment at Columbia. Predicted and observed values from the four sites were significantly related (r2 = 0.94, n = 113, P < 0.001), with slope not significantly different from 1. Given the high correlation of simulated and observed SOM changes, CQESTR can be used as a reliable tool to predict SOM changes from management practices and offers the potential for estimating soil C storage required for C credits. It can also be an important tool to estimate the impacts of crop residue removal for bioenergy production on SOM level and soil production capacity.
 
 
 
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