Biomedical subjects

Huijun Xin

Publications and source records attributed to Huijun Xin.

3 recordsLinked to original sources

PubMed2005

Examining the proteins of functional retinal lipofuscin using proteomic analysis as a guide for understanding its origin.

PURPOSE: To elucidate the origins of biologically active retinal lipofuscin (RLF) by examining its protein composition. METHODS: Total protein and total lipid were extracted and quantified. Proteins in this lipoprotein granule were identified by limited-scale proteomic analysis using both two-dimensional (2D) gel electrophoresis and SDS-PAGE coupled with MALDI-QqToF MSMS and automated LCMSMS, respectively. RESULTS: RLF granules were 44% protein and 50% lipid. Proteomic analyses identified 41 constituent proteins. Hydrophobic proteins and several proteins specific to photoreceptors, including rhodopsin, that have not previously been reported, were identified. Extensive protein modification, especially oxidative damage, was observed. CONCLUSIONS: Proteins identified support the model that RLF accumulates in RPE cells as a result of the buildup of undigested material from the phagocytosis of photoreceptor outer segments. Perhaps oxidative damage renders some of these proteins indigestible and thus leads to the accumulation of RLF granules.

Adult↗

PubMed2003

DNA-templated nanotube localization.

Carbon nanotubes are nanometer-scale materials with important properties, but their use in nanofabrication will require further development of methods for controlled positioning at well-defined locations on surfaces. We have devised an approach for specifically localizing single-walled carbon nanotubes (SWNTs) onto 1-pyrenemethylamine (PMA)-decorated lambda-DNA molecules aligned on Si surfaces. PMA is used as a bridging compound because its amine group is attracted electrostatically to the negatively charged phosphate backbone of DNA, while the pyrenyl group in PMA interacts with SWNT surfaces through pi-stacking forces. From a total of 60 atomic force microscopy images obtained on three different substrates, we determined that 63% of SWNTs observed on the surfaces were anchored along DNA, and these nanotubes covered approximately 5% of the total DNA length. DNA-templated nanopositioning offers intriguing possibilities for the bottom-up assembly of materials at the nanometer scale.

Bacteriophage lambda↗

PubMed2002

Simultaneous detection of CpG methylation and single nucleotide polymorphism by denaturing high performance liquid chromatography.

We report here a novel method to simultaneously detect CpG methylation and single nucleotide polymorphisms (SNPs) using denaturing high performance liquid chromatography (DHPLC). PCR products of bisulfite-modified CpG islands were separated using DHPLC. BstUI digestion and DNA sequencing were used in confirmation studies. Consistent with the BstUI digestion assay, the 294 bp PCR product of the modified hMLH1 promoter showed different retention times between the methylated cell lines (RKO and Cla, 6.7 min) and the unmethylated cell lines (PACM82 and MGC803, 6.2 min). No hMLH1 methylation was observed in 13 primary gastric carcinomas and their matched normal tissues. One hMLH1 SNP was detected in gastric cancer patients, in both cancer and normal tissues. DNA sequencing revealed that the SNP is a G-->A variation at -93 nt of the hMLH1 promoter. A two-peak chromatogram was also obtained in the 605 bp PCR product of the Cox-2 promoter of the AGS, HEK293 and MKN45 cell lines by DHPLC. Another peak corresponding to methylated CpG islands was observed on the chromatogram of the Cox-2-methylated AGS cell line after bisulfite treatment. In conclusion, methylation in homoallelic and heteroallelic CpG islands could be detected rapidly and reliably by bisulfite-DHPLC. A SNP in the target sequence could also be detected at the same time.

Adaptor Proteins, Signal Transducing↗