Biomedical subjects

Lixian Dong

Publications and source records attributed to Lixian Dong.

3 recordsLinked to original sources

PubMed2006

Role of the N-terminus in permeability of chicken connexin45.6 gap junctional channels.

Previous studies have shown that gap junctional channels formed from the lens connexins Cx50 (or its chicken orthologue, Cx45.6) and Cx43 exhibit marked differences in transjunctional voltage gating and unitary conductance. In the present study, we used the negatively charged dye, Lucifer Yellow (LY), to examine and compare quantitative differences in dye transfer between pairs of HeLa cells stably transfected with Cx45.6 or Cx43. Our results show that Cx45.6 gap junctional channels are three times less permeable to LY than Cx43 channels. Replacement of the N-terminus of Cx45.6 with the corresponding domain of Cx43 increased LY permeability, reduced the transjunctional voltage (V(j)) gating sensitivity, and reduced the unitary conductance of Cx45.6-43N gap junctional channels. Further experiments, using a series of Alexa probes that had similar net charge but varied in size showed that the Cx45.6-43N had a significantly higher permeability for the two largest Alexa dyes than Cx45.6. These data suggest that the N-terminus plays a critical role in determining many of biophysical properties of Cx45.6 gap junctional channels, including molecular permeability and voltage gating.

Amino Acid Sequence↗

PubMed2006

[Determination of triazines in surface water using solid phase extraction-high performance liquid chromatography].

A method was developed to monitor triazines in surface water using the combination of solid phase extraction (SPE) and high performance liquid chromatography. Four different SPE cartridges were tested for extracting six triazines, including atrazine (A), simazine (S), prometryn (P), desethylatrazine (DEA), 2-hydroxyatrazine (OHA) and desisopropylatrazine (DIA), and finally ENVI-18 was selected as optimal. The method for solid phase extraction was further systematically studied for details. Optimal results of orthogonal design were determined as follows: pH 6, 5 mL methanol as eluting solvent, and no methanol added into water sample before extraction. The detection limits of six triazines were 0.14 microg/L for P, 0.12 microg/L for A, 0.08 microg/L for S, 0.08 microg/L for DEA, 0.10 microg/L for OHA and 0.18 microg/L for DIA. This method was applied for environmental aquatic samples, and the results showed that the concentration of prometryn in a lake was detected as (9.33 +/- 0.27) microg/L, as well as the concentrations of atrazine and prometryn in a river were detected as (5.28 +/- 0.43) microg/L and (7.12 +/- 0.54) microg/L respectively.

English Abstract↗

PubMed2004

Exchange of gating properties between rat cx46 and chicken cx45.6.

Cx46 and Cx50 are coexpressed in lens fiber cells where they form fiber-fiber gap junctions. Recent studies have shown that both proteins play a critical role in maintaining lens transparency. Although both Cx46 and Cx50 (or its chicken ortholog, Cx45.6) show a high degree of sequence homology, they exhibit marked differences in gap junctional channel gating, unitary gap junctional channel conductance, and hemichannel gating. To better understand which regions of the protein are responsible for these functional differences, we have constructed a series of chimeric Cx46-Cx45.6 gap junctional proteins in which a single transmembrane or intracellular domain of Cx45.6 was replaced with the corresponding domain of Cx46, expressed them in Xenopus oocyte pairs or N2A cells, and examined the resulting gap junctional conductances. Our results showed that four out of six of the chimeras induced high levels of gap junctional coupling. Of these chimeras, only Cx45.6-46NT showed significant changes in voltage-dependent gating properties. Exchanging the N-terminus had multiple effects. It slowed the inactivation kinetics of the macroscopic junctional currents so that they resembled those of Cx46, reduced the voltage sensitivity of the steady-state junctional conductance, and decreased the conductance of single gap junctional channels. Additional point mutations identified a uniquely occurring arginine in the N-terminus of Cx46 as the main determinant for the change in voltage-dependent gating.

Animals↗