Baochen Fan - Academia.edu (original) (raw)

Papers by Baochen Fan

Yingyong huaxue, Dec 1, 1990

Journal of Organometallic Chemistry, Oct 1, 1989

Abstract AlCl 3 activated by aluminum powder at 140°C reacts with SmCl 3 in m -xylene to give a n... more Abstract AlCl 3 activated by aluminum powder at 140°C reacts with SmCl 3 in m -xylene to give a new neutral arene complex of samarium, Sm(η 6 - m -(CH 3 ) 2 C 6 H 4 )(AlCl 4 ) 3 ( 1 ). The crystal structure determination shows that 1 crystallizes in the monoclinic space group P 2 1 / n , with a 18.36(5), b 16.37(4), c 20.31(6) A, β 114.11(2)°, V 5567.87 A 3 , Z = 8, R = 0.071. Two independent moieties with slightly different bond parameters occupy each unit cell.

Journal of Organometallic Chemistry, Nov 1, 1989

The @-benzene complexes of ianthanoids Ln($-C,H,)(AlCl,),-C,H, (Ln = La (l), Nd (2), Sm (3)) have... more The @-benzene complexes of ianthanoids Ln($-C,H,)(AlCl,),-C,H, (Ln = La (l), Nd (2), Sm (3)) have been prepared by the reaction of LnCl, with activated AlCI, in benzene. The crystal structures of 2 and 3 have been determined. Complexes 2 and 3 each crystallize ftom benzene in the triclinic space group Pi; with a 9.40(2), b 9,74(3), c 16.61(5) A, a 96.69{2), j3 93.54(3), y 111.63(2)* for 2, and a 9.46(2), b 9.77(3), c l&78(4) A, 1~ 96.00(2), fi 93.7692), y 111,66(2)O for 3. The X-ray diffraction study has revealed that the central atom in Ln($-C~H~}(AlCl~)~-type complexes exerts no distinct influence on the molecular structure. Comparable M-ligand bond lengths reflect the difference in the ionic radii of neodymium and samarium.

Biochemical and Biophysical Research Communications, Apr 1, 2009

Biochemistry, May 30, 1995

Glycogen debranching enzyme contains two catalytic activities (4-a-glucanotransferase and amylo-1... more Glycogen debranching enzyme contains two catalytic activities (4-a-glucanotransferase and amylo-1,6-glucosidase) on its single polypeptide chain, and they are affected differently by the binding of oligosaccharides. Glucose, maltose, and maltotriose are competitive inhibitors of the amylo-1,6glucosidase activity measured by the hydrolysis of a-glucosyl fluoride, whereas saccharides with four or more glucose units are activators of the same activity, showing apparent "uncompetitive" kinetics. This suggests that they do not bind until the a-glucosyl fluoride is bound. In either case the potency of the effect increases with the length of the oligosaccharide chain. On the other hand, all oligosaccharides tested (maltose to maltohexaose, a-cyclodextrin, and P-cyclodextrin) are competitive inhibitors of the transferase activity and also cause a decrease in the intrinsic fluorescence, both functions again increased by chain length, thus indicating that these saccharides do bind to the free enzyme. These interesting results can be reconciled if the extended main chain resulting from the transferase reaction has to be reoriented into a different binding mode in order to position the a-l,6-linked side-chain glucose into the correct position for the glucosidase reaction. Therefore, activating oligosaccharides behave kinetically as if they had not been previously bound. It is concluded that the main chain of the natural limit dextrin substrate has a different mode of binding for the two catalytic reactions in order to position properly first the maltotetraosyl side chain in the transferase catalytic site and then the glucosyl side chain in the glucosidase catalytic site. All activating saccharides, including glycogen, elicit the same maximal glucosidase velocity, 6-fold the unactivated rate, suggesting that all generate the same enzyme conformation. Circular dichroic spectra yielded estimates of the secondary structure, but these were unaffected by any tested saccharide. Glycogen debranching enzyme (amylo-1,6-glucosidase/4a-glucanotransferase, EC 3.2.1.33 and EC 2.4.1.25) removes the 1,6-branch points in the limit dextrin resulting from the action of phosphorylase on glycogen. Its action consists of transferring a maltotriose unit to the "main chain" from the four glucose units attached to this main chain by a-1,6 linkages. This results in an elongated section of a-1,4-linked polymer, leaving a single glucose attached to it via an a-1,6 linkage. The enzyme then cleaves the a-1,6 linkage by which this glucose is attached. The transferase and glucosidase activities are both found on the single large polypeptide chain of this monomeric enzyme (Brown & Brown, 1966; Nelson et al., 1969; Bates et al., 1975), which for the rabbit enzyme has a molecular mass of 177 542 Da as estimated from its cDNA-derived protein sequence (Liu et al., 1993). Nelson and colleagues used reversible inhibitors and a catalytic site-directed irreversible inhibitor to analyze the two catalytic activities and concluded that the enzyme has

Journal of Biological Chemistry, Jul 1, 1998

Cytokine-inducible nitric-oxide (NO) synthase (iNOS) contains an oxygenase domain that binds heme... more Cytokine-inducible nitric-oxide (NO) synthase (iNOS) contains an oxygenase domain that binds heme, tetrahydrobiopterin, and L-arginine, and a reductase domain that binds FAD, FMN, calmodulin, and NADPH. Dimerization of two oxygenase domains allows electrons to transfer from the flavins to the heme irons, which enables O 2 binding and NO synthesis from L-arginine. In an iNOS heterodimer comprised of one full-length subunit and an oxygenase domain partner, the single reductase domain transfers electrons to only one of two hemes (

Biochemistry, Oct 1, 1997

The resonance Raman spectra of the carbon monoxide (CO) derivatives of nitric oxide synthases (NO... more The resonance Raman spectra of the carbon monoxide (CO) derivatives of nitric oxide synthases (NOSs), in which CO coordinates to the heme at the site occupied by oxygen under physiological conditions, are very sensitive to the presence of substrates and inhibitors. Significant differences in the modes associated with the bound CO are now found to depend on the isoenzyme. In the presence of L-arginine, the physiological substrate, the frequencies of the Fe-Co stretching mode and the C-O stretching mode in nNOS, the brain enzyme, are detected at 503 and 1929 cm-1, respectively; whereas in iNOS, the inducible enzyme from macrophage, the modes are detected at 512 and 1906 cm-1, respectively. The frequencies in eNOS, the endothelial isozyme, are similar to those of iNOS. These results indicate that nNOS has a much more open substrate-binding pocket than iNOS and eNOS. A theoretical simulation based on the interaction between the CO and a positively charged guanidino group on the arginine indicates that the polar environment of the CO differs markedly between the isozymes. This may be accounted for either by an arginine-CO distance that is as much as 1 A greater in nNOS than in iNOS and eNOS or by a substantial shielding of the charge on the arginine in nNOS as compared to the other isozymes. This is the first reported detection of a structural difference of the substrate binding sites between the isozymes and serves as an initial step in a rational drug design for NOS.

Protein Engineering, 1997

Industrial & Engineering Chemistry, 1958

Fire Safety Science, 2005

The external explosions may occur in an explosion venting and give a potential risk. However, the... more The external explosions may occur in an explosion venting and give a potential risk. However, the basic dynamic process of external explosions during the venting to ambient air is yet not well understood. In this paper, a series of vented explosion tests in high failure pressure has been conducted in a cylindrical venting vessel. It has been demonstrated clearly from the pressure-time histories and the shadowgraphs of the external flow field that under some suitable venting conditions there exist two peak pressures in the external flow field, one is generated from the membrane rupture and the other is induced by the external explosion due to the violent combustion of the vented combustible gas. The effects on the flow patterns outside the venting vessel under different failure pressures, vent areas (blockage ratio) and chemical equivalent ratios are also discussed in the term of the experimental results. Moreover, the venting process was simulated numerically by using SIMPLE schemes in colocated grid, based on the k-ε turbulent model and 'eddy dissipation combustion model'. The calculated results are in good agreement with the measured results. The dominant mechanisms of the occurrence of the external explosion during the venting processes have been elucidated based on measured and calculated results.

Nature Structural & Molecular Biology, 1997

Journal of Organometallic Chemistry, 1989

Journal of Biological Chemistry, 1998

Combustion Theory and Modelling, 2007

A reduced in situ adaptive tabulation (RISAT) method, which was originally proposed by Pope (Comb... more A reduced in situ adaptive tabulation (RISAT) method, which was originally proposed by Pope (Combustion Theory and Modelling, 1997, 1, 41–36), is developed for the applications of multidimensional transient reactive flow computations. The RISAT method, which based on the storage/retrieval operation processes of data, employs the constant approximation of chemical reactions and the dynamic deletion of a data table to limit the table size during the computations. It is incorporated in the computations of two-dimensional detonation of CH4/O2 premixed gas induced by shock waves focusing to enhance the computational performance of combustion chemistry. The effects of query tolerance and table size on the computational efficiency are examined. A maximum chemical speedup factor of 17.88 can be obtained by using the RISAT, without losing the computational accuracy. It is concluded from the computational results that the RISAT method is strongly dependent on the table size, tolerance and physics of transient reactive flow problems.

Biochemistry, 1995

Biochemistry, 1998

Resonance Raman spectra of the R 1 1 isoform of bovine lung soluble guanylate cyclase expressed f... more Resonance Raman spectra of the R 1 1 isoform of bovine lung soluble guanylate cyclase expressed from baculovirus have been measured. The spectra show that the ferric heme is five-coordinate high spin whereas the ferrous heme in the absence of added exogenous ligands is a mixture of sixcoordinate low spin and five-coordinate high spin. In the Fe-CO-derivative, the correlation between the Fe-CO frequency (497 cm-1) and the CO frequency (1959 cm-1) demonstrates that the proximal ligand in our preparation is histidine. The Fe-NO stretching frequency (found at 520 cm-1) and other spectral features of the ferrous Fe-NO-bound sGC are similar to those reported by Deinum et al. (1) and Yu et al. (2). These data indicate that although large preparation-dependent differences in the occupancy of the distal pocket exist, all the preparations have the same proximal histidine ligation and share the same mechanism of activation by NO.