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Conformation of 60-residue peptide fragment from N-terminal of porcine kidney fructose 1,6-bisphosphatase

Science China(Life Sciences) 1997年第3期40卷 251-256页

作者：杨伟文赵辅昆许根俊 Shanghai Institute of Biochemistry Chinese Academy of Sciences Shanghai 200031 China State Key Laboratory of Macromolecules Beijing 100101 China

Limited digestion of fructose 1,6-bisphosphatase with subtilisin produces an S-peptide with an about 60-residue peptide fragment that is non-covalently associated with the enzyme. The 60-residue peptide fragment con-sists of the most part of allosteric site for AMP binding. It could be separated from S-protein by gel filtration with a Sephadex G-75 column equilibrated with 9% formic acid. According to X-ray diffraction results the S-peptide consists of two α-helices without β-strand and the α-helix content is about 60% in the 60-residue-peptide fragment. When the enzyme is subjected to limited proteolysis with subtilisin, the secondary structure of the enzyme does not show a de-tectable change in CD spectrum. The CD spectra of the isolated S-peptide were measured under different concentra-tions. In the absence of GuHCl, S-peptide had 30% a-helix and 38.5% turn-like structure but had no β-strand, sug-gesting that the N-terminal 60-residue fragment, which is synthesized initially by ribosome, would form a conforma-tion spontaneously similar to that of the isolated 60-residue-peptide, i.e. about 30% a-helix and 30% turn-like struc-ture. As the elongation of the peptide chain of the enzyme proceeds, the newly synthesized segment or the final entire enzyme, in turn, affects the conformation of prior peptide segment and adjusts its conformation to the final native state. The content of a-helix did not increase as perturbing the conformation of S-peptide by adding ethanol, cyclohex-ane or a small amount of SDS. On the contrary, the ordered structure was slightly decreased, indicating that the dif-ference of conformations of S-peptide in the isolated form and in the associated protein was not an artifact produced by isolation process.

关键词： fructose 1 6-bisphosphatase allosteric site secondary structure the folding of newly synthesized peptide conformation adjustment.

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Modified conceptual model for predicting the tendency of alluvial channel adjustment.induced by human activities

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Chinese Science Bulletin 2001年第S1期46卷 51-57页

作者： XU JiongxinInstitute of Geographical Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing 100101, China (e-mail: xujxin?***) Institute of Geographical Sciences and Natural Resources Research Chinese Academy of Sciences Beijing China

After a discussion about some limitations of Schumm’s conceptual model for prediction of river metamorphosis, this study introduces the channel boundary material as an independent variable, and thereby establishes a conceptual model that can be used to predict the direction of channel adjustment.induced by human activities. This model has been tested by data from natural rivers and a laboratory model river, and can be used to explain the complex behavior of channel adjustment.after reservoir construction.

关键词： human influence on channels channel boundary condi- tions feedback in channel system prediction of channel adjustment.

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Determination of global mean sea surface WHU2000 using multi-satellite altimetric data

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Chinese Science Bulletin 2002年第19期47卷 1664-1668页

作者： Jiang, WP Li, JC Wang, ZG Wuhan Univ Sch Geodesy & Geophys Wuhan 430079 Peoples R China

In this study, the overall editing criteria for altimetric data are considered and the geophysical correction models is improved. The datum for various altimetric data is also unified and the method of a full-combined crossover adjustment.for different altimetric tracks is used to improve the radial orbits of Geosat, ERS-1 and ERS-2 data. In addition, the method for determining mean sea surface (MSS) by using multi-altimetric data is developed. The data used to compute WHU2000 MSS include 7-year Topex/Poseidon data (cycles 11-249), 2-year Geosat ERM data (cycles 1-44), 5-year ERS2 data (cycles 1-52) and all ERS-1 168-day data. The WHU2000 MSS is determined with a grid resolution of 2’×2’ within the ± 82° latitude and its precision is better than 0.05 m. Comparing WHU 2000MSS with 3.75’×3.75’ CLS_SHOM98.2 MSS, 3’×3’ GFZ MSS95A and 3.75’×3.75’ OSU MSS95, as external checks, the corresponding standard deviation (STD) of their differences is 0.090 m, 0.211 m and 0.079 m respectively.

关键词： altimetry mean sea surface crossover adjustment.

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