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Articles by Y Han
Total Records ( 3 ) for Y Han
  C Peng , W Chen , Y Han , T Sanders , G Chew , J Liu , E Hawrot , C Chi and C. Wang

As part of continuing studies of the identification of gene organization and cloning of novel -conotoxins, the first 4/4-conotoxin identified in a vermivorous Conus species, designated Qc1.2, was originally obtained by cDNA and genomic DNA cloning from Conus quercinus collected in the South China Sea. The predicted mature toxin of Qc1.2 contains 14 amino acid residues with two disulfide bonds (I-III, II-IV connectivity) in a native globular configuration. The mature peptide of Qc1.2 is supposed to contain an N-terminal post-translationally processed pyroglutamate residue and a free carboxyl C-terminus. This peptide was chemically synthesized and refolded for further characterization of its functional properties. The synthetic Qc1.2 has two interconvertible conformations in aqueous solution, which may be due to the cis-trans isomerization of the two successive Pro residues in its first Cys loop. Using the Xenopus oocyte heterologous expression system, Qc1.2 was shown to selectively inhibit both rat neuronal 3β2 and 3β4 subtypes of nicotinic acetylcholine receptors with low potency. A block of ~63% and 37% of the ACh-evoked currents was observed, respectively, and the toxin dissociated rapidly from the receptors. Compared with other characterized -conotoxin members, the unusual structural features in Qc1.2 that confer to its receptor recognition profile are addressed.

  X Liu , Y Han , D Yuen and B. Ma

Motivation: The bottom-up tandem mass spectrometry (MS/MS) is regularly used in proteomics nowadays for identifying proteins from a sequence database. De novo sequencing software is also available for sequencing novel peptides with relatively short sequence lengths. However, automated sequencing of novel proteins from MS/MS remains a challenging problem.

Results: Very often, although the target protein is novel, it has a homologous protein included in a known database. When this happens, we propose a novel algorithm and automated software tool, named Champs, for sequencing the complete protein from MS/MS data of a few enzymatic digestions of the purified protein. Validation with two standard proteins showed that our automated method yields >99% sequence coverage and 100% sequence accuracy on these two proteins. Our method is useful to sequence novel proteins or ‘re-sequence’ a protein that has mutations comparing with the database protein sequence.

  Y Han , J. D Chen , Z. M Liu , Y Zhou , J. H Xia , X. L Du and M. W. Jin

Cardiac c-kit+ cells are generally believed to be the major population of stem/progenitor cells in the heart and can be used as a cell source for cardiomyoplasty; however, the cellular electrophysiological properties are not understood in this type of cells. The present study was designed to investigate functional ion channels in undifferentiated mouse cardiac c-kit+ cells using approaches of whole cell patch voltage clamp, RT-PCR, and cell proliferation assay. It was found that three types of ionic currents were present in mouse cardiac c-kit+ cells, including a delayed rectifier K+ current (IKDR) inhibited by 4-aminopyridine (4-AP), an inward rectifier K+ current (IKir) decreased by Ba2+, and a volume-sensitive chloride current (ICl.vol) inhibited by 5-nitro-1-(3-phenylpropylamino) benzoic acid (NPPB). RT-PCR revealed that the corresponding ion channel genes, Kv1.1, Kv1.2, and Kv1.6 (for IKDR), Kir.1.1, Kir2.1, and Kir2.2 (likely responsible for IKir), and Clcn3 (for ICl.vol), were significant in mouse cardiac c-kit+ cells. The inhibition of ICl.vol with NPPB and niflumic acid, but not IKDR with 4-AP and tetraethylammonium, reduced cell proliferation and accumulated the cell progression at G0/G1 phase in mouse cardiac c-kit+ cells. Our results demonstrate that three types of functional ion channel currents (i.e., IKDR, IKir, and ICl.vol) are present in mouse cardiac c-kit+ cells, and ICl.vol participates in regulating cell proliferation.

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