Xiao-hong Zheng | Search PubMed

PubMed2006

Current rectification by asymmetric molecules: an ab initio study.

Current rectification effect in an asymmetric molecule HCOO-C6H4-(CH2)n sandwiched between two aluminum electrodes has been studied using an ab initio nonequilibrium Green's function method. The conductance of the system decreases exponentially with the increasing number n of CH2. The phenomenon of current rectification is observed such that a very small current appears at negative bias and a sharp negative differential resistance at a critical positive bias when n>or=2. The rectification effect arises from the asymmetric structure of the molecule and the molecule-electrode couplings. A significant rectification ratio of approximately 38 can be achieved when n=5.

Journal Article↗

PubMed2004

Molecular cloning and characterization of a Rac1 homologue cDNA from Trichomonas vaginalis.

OBJECTIVE: To clone and characterize a Rac1 homologue from Trichomonas vaginalis for studying cell cycle of the organism. METHODS: A cDNA library derived from T. vaginalis mRNA was constructed into lambda TriplEx2 phage vector. An expression sequence tag program was launched. Sequences of cDNA clones were analyzed using NCBI BLAST algorithms, and ClustalW and Treeview programs. RESULTS: A cDNA clone with a length of 714 base pairs was isolated. The sequence analysis showed that the cDNA clone has an open reading frame with 600 bp. The deduced amino acid sequence from the open reading frame contains 200 residuals and is most homologous to Rac1 subfamily of Rho GTPases with >60% identity. The conserved sequence elements of Rho GTPases, such as GTP-binding sites, GTPase-activating protein (GAP) interaction motifs, GTP-dissociation inhibitors (GDI) interaction motifs, guanine nucleotide exchange factor (GEF) interaction elements, etc, were detected in the amino acid sequence. The phylogenetic analysis showed that the cDNA clone is grouped in the Rac subfamily and is more closely related to Rac1 proteins of protozoa. CONCLUSION: The cDNA clone isolated belongs to Rac subfamily of Rho GTPases and is probably a Rac1 protein of T. vaginalis.

Amino Acid Sequence↗