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Y Q Feng

Publications and source records attributed to Y Q Feng.

27 records · Page 2Linked to original sources
PubMed1991

Chemical exchange in two dimensions in the 1H NMR assignment of cytochrome c.

The important role played by chemical exchange in solving the proton assignment problem for oxidized and reduced horse cytochrome c is described. Some novel approaches for establishing oxidation-reduction exchange correlations in combinations of several two-dimensional spectra were used. Unambiguous chemical exchange correlations were established for 55 NH-C alpha H resonances and all the aromatic and side chain methyl resonances. Consistent although not fully unambiguous main chain proton correlations were observed for 47 of the remaining 49 residues. The many exchange correlations found serve to multiply cross-connect the two extensive, individually self-consistent networks of assignments found for the oxidized and reduced forms, and thus help to confirm both sets of assignments.

Cytochrome c Group↗
PubMed1991

[Hepatic inflammatory pseudotumor. A report of 5 cases].

Hepatic inflammatory pseudotumor (HIP) is rare. To our knowledge, there have only been 27 cases reported since 1953. We studied additional five cases, male, aged 13-56 years, with a history of the disease of 20 days-1 year. Major complains were epigastric pain, fever of unknown causes, and epigastric mass. All five HIPs were solitary and surgically resected with a final diagnosis made pathologically. HIPs mimic the characters of liver cancer on ultrasonography and CT scanning, however, the following several points could be used to establish the diagnosis: patients with a long history of hepatic tumor still in a rather good condition; patients with no cirrhosis and negative AFP test results; tumors that are well encapsulated, etc. Surgical exploration should be attempted in all patients unless in those with poor risks in which steroid therapy may prove useful.

Adolescent↗
PubMed1990

Assignment of paramagnetically shifted resonances in the 1H NMR spectrum of horse ferricytochrome c.

The proton resonances of the heme, the axial ligands, and other hyperfine-shifted resonances in the 1H nuclear magnetic resonance spectrum of horse ferricytochrome c have been investigated by means of one- and two-dimensional nuclear Overhauser and magnetization transfer methods. Conditions for saturation transfer experiments in mixtures of ferro- and ferricytochrome c were optimized for the cross assignment of corresponding resonances in the two oxidation states. New resonance assignments were obtained for the methine protons of both thioether bridges, the beta and gamma meso protons, the propionate six heme substituent, the N pi H of His-18, and the Tyr-67 OH. In addition, several recently reported assignments were confirmed. All of the resolved hyperfine-shifted resonances in the spectrum of ferricytochrome c are now identified. The Fermi contact shifts experienced by the heme and ligand protons are discussed.

Animals↗
PubMed1990

[Inhibition of PHA-stimulated T cell conditioned medium (PHA-TCM) on the growth of human myeloid progenitor cells (CFU-C)].

Cord blood T cells were enriched by nylon wool colomn, and effects of PHA-stimulated T cell supernatant collected from 18 h to 7 days on the proliferation of CFU-c were studied. The results showed that the supernatant collected at 18 h (PHA-TCM) could significantly inhibit the growth of CFU-c and the inhibition was PHA-TCM dose dependent, suggesting there is a CFU-c inhibitory activity in PHA-TCM. Kinetic studies demonstrated that the activity was decreased in the supernatant collected at 48 h and disappeared at 7 days. On the other hand, unstimulated T cell supernatant and PHA alone had no inhibitory effect on CFU-c growth. Indomethacin did not affect the production of the inhibitory activity and no interferon activity could be detected in PHA-TCM. These suggested that the inhibition was mediated by a non-interferon, non-prostaglandin suppressor. Further studies revealed that the suppressor was a protein stable at 56 degrees C and lost in pH 2 and pH 11 for 3 h, its molecular weight was large than 10,000 dolton.

Adult↗
PubMed1989

Proton resonance assignments of horse ferrocytochrome c.

Two-dimensional nuclear magnetic resonance (NMR) spectroscopy was used to assign the proton resonances of horse ferrocytochrome c. Assignments were based on the main chain directed (MCD) and sequential assignment procedures. The fundamental units of the MCD approach, the main-chain NH-C alpha H-C beta H J-coupled subspin systems of each amino acid residue (NAB sets), were defined by analysis of direct and relayed coherence transfer spectra. Recognition of main-chain NOE connectivity patterns specified in the MCD algorithm then allowed NAB sets to be aligned in their proper juxtaposition within secondary structural units. The units of secondary structure were placed within the polypeptide sequence of identification of a small number of side-chain J-coupled spin systems, found by direct recognition in 2D spectra of some J-coupled spin systems and by pairwise comparisons of the J-correlated spectra of six homologous cytochromes c having a small number of known amino acid differences. The placement of a given segment in this way defines the amino acid identity of all its NAB sets. This foreknowledge allowed the vast majority of the side-chain resonances to be discerned in J-correlated spectra. Extensive confirmation of the assignments derives internally from multiple main-chain NOE connectivities and their consistency following temperature-induced changes of the chemical shifts of NOE-correlated protons. The observed patterns of main-chain NOEs provide some structural information and suggest small but potentially significant differences between the solution structure observed by NMR and that defined earlier in crystallographic studies at 2.8-A resolution.

Amino Acid Sequence↗
PubMed1989

[Effect of PHA-T cell conditioned medium (PHA-TCM) on leukemic cells].

Cord blood T cells, purified by nylon wool column, were incubated with PHA for 18 hours, and the supernatant were harvested as PHA-TCM. The results demonstrated that PHA-TCM could significantly inhibit the growth of U937 cells and reduce their 3H-TdR incorporation and spontaneous colony formation. After 3-6 days of treatment with PHA-TCM in culture, part of U937 cells became macrophage-like, latex-phagocytic, and capable of reducing NBT dye. On the contrary, HL-60 cells did not respond to PHA-TCM inhibition, indicating the selective effect of PHA-TCM.

Cell Differentiation↗