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Biomedical subjects

X Liang

Publications and source records attributed to X Liang.

260 records · Page 15Linked to original sources
PubMedDate not supplied

Protein tyrosine phosphatase SHP-1 specifically recognizes C-terminal residues of its substrates via helix alpha0.

The catalytic domain of protein tyrosine phosphatase SHP-1 possesses distinct substrate specificity. It recognizes the P-3 to P-5 residues of its substrates via the beta5-loop-beta6 region. To study the substrate specificity further, we determined the structure of the catalytic domain of SHP-1 (C455S) complexed with a less-favorable-substrate peptide originated from SIRPalpha. The complex has disordered N-terminal peptide structure and reduced interactions between the N-terminal peptide and the beta5-loop-beta6 region. This could be the basis for the lower affinity of peptide pY(427) for the catalytic domain of SHP-1. In addition, by comparing the SHP-1/less-favorable peptide complex structure with the SHP-1/substrate complex structures, we identified a novel substrate-recognition site in the catalytic domain of SHP-1. This site was formed by helix alpha0 and the alpha5-loop-alpha6 motif of SHP-1, and specifically bound residues at the P + 4 and further C-terminal positions of peptide substrates.

Binding Sites↗
PubMedDate not supplied

Cloacal dysgenesis sequence: observations in four patients including three fetuses of second trimester gestation.

Cloacal dysgenesis is a rare malformation sequence. We studied cloacal dysgenesis in four fetuses, including three at 18-22 weeks of gestation. All four fetuses showed a smooth perineum with absence of anal, urethral, and/or vaginal openings. The urinary bladder was dilated in 3 cases. The labia majora and minora were absent in the two female fetuses; the scrotum and penis were absent in one male fetus and hypoplastic in the second. The kidneys were either absent (1 case), dysplastic (1 case), or hydronephrotic (1 case). Normal kidneys were seen in a fetus of 20-22 weeks gestation in whom the urinary obstruction was alleviated by a vesicocolonic fistula. This fetus did not have pulmonary hypoplasia. Severe renal anomaly and pulmonary hypoplasia are the limiting factors for the survival of infants born with cloacal dysgenesis. The unique observation of normal kidneys and lungs in one of our fetuses, despite anhydramnios, suggests that the effect of oligohydramnios on lung development may be limited early in gestation, at least up to 20-22 weeks. It may also indirectly support the theory that there are factors other than oligohydramnios that interfere with early lung development, such as reduced production of a pulmonary growth factor by the kidney or reduced proline production by malformed kidneys, that may cause decreased collagen formation and result in hypoplastic lung mesenchyme.

Abnormalities, Multiple↗
PubMedDate not supplied

Prediction of soil organic partition coefficients by a soil leaching column chromatographic method.

The soil organic partition coefficient (Koc) is one of the most important parameters to depict the transfer and fate of a chemical in the soil-water system. Predicting Koc by using a chromatographic technique has been developing into a convenient and low-cost method. In this paper, a soil leaching column chromatograpy (SLCC) method employing the soil column packed with reference soil GSE 17201 (obtained from Bayer Landwirtschaftszentrum, Monheim, Germany) and methanol-water eluents was developed to predict the Koc of hydrophobic organic chemicals (HOCs), over a log Koc range of 4.8 orders of magnitude, from their capacity factors. The capacity factor with water as an eluent (k'w) could be obtained by linearly extrapolating capacity factors in methanol-water eluents (k'w) with various volume fractions of methanol (symbol in text). The important effects of solute activity coefficients in water on k'w and Koc were illustrated. Hence, the correlation between log Koc and log k'w (and log k') exists in the soil. The correlation coefficient (r) of the log Koc vs. log k'w correlation for 58 apolar and polar compounds could reach 0.987, while the correlation coefficients of the log Koc -log k' correlations were no less than 0.968, with (symbol in text)ranging from 0 to 0.50. The smaller the (symbol in text), the higher the r. Therefore, it is recommended that the eluent of smaller (symbol in text), such as water, be used for accurately estimating Koc. Correspondingly, the r value of the log Koc -log k'w correlation on a reversed-phase Hypersil ODS (Thermo Hypersil, Kleinostheim, Germany) column was less than 0.940 for the same solutes. The SLCC method could provide a more reliable route to predict Koc indirectly from a correlation with k'w than the reversed-phase liquid chromatographic (RPLC) one.

Chromatography, Liquid↗