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Biomedical subjects

A Zhang

Publications and source records attributed to A Zhang.

At least 181 records · Page 10Linked to original sources
PubMed1987

Effect of C-banded heterochromatin on centromere separation.

The present study is to determine the effects of centromeric heterochromatin on centromere separation. Amniotic cell cultures in which the centromeric heterochromatin of one chromosome was at least twice as large (qh+) as the heterochromatin (qh) in the homologous chromosome were selected. Fifteen amniotic cell samples with 1qh+, 9qh+ or 16qh+ were studied. The size of the centromeric heterochromatin was directly correlated with the delay in centromere separation. The chromosome with the smaller centromeric heterochromatin tended to show earlier centromere separation than the homologue with the larger heterochromatin. Our results suggest that the quantity of centromeric heterochromatin may influence the genetic control of centromere separation.

Amnion↗
PubMed1986

Investigations of primary and secondary structure of porcine ubiquitin. Its N epsilon-acetylated lysine derivative.

N epsilon-acetylation in vitro of internal lysyl residues of Ub by p-nitro-phenyl acetate at pH 8.0 was performed. The position of acetylation sites are determined. (e.g. Fully acetylated: Lys-6, Lys-11 and Lys-33; partially free internal lysines: Lys-27, Lys-29; Lys-48 and probably Lys-63.) 55 cycles Edman degradation were performed and the first 53 N-terminal residues were identified. Secondary structural studies of ubiquitin have been carried out using the circular dichroism (CD) technique. No changes are noted upon heating to 100 degrees C at neutral pH even in the presence of 8 M urea but in 6 M guanidine-HCl extensive modification results. Ubiquitin with an average of 4.4 of its 7 lysines in the N epsilon-acetyl form shows little deviation from native protein. After reduction with dithiothreitol and subsequent removal of the mercaptan, significant changes in the secondary structure are noted. Circular dichroic measurements of ubiquitin indicated an alpha-helical content of about 10% whereas the secondary structural predictions of Chou and Fasman suggest a level of about 45%.

Acetylation↗
PubMed1982

Complete amino acid sequence of mung bean trypsin inhibitor.

The mung bean trypsin inhibitor has been found to be microheterogeneous at N-terminal region due to the presence of several isomers. After treatment with aminopeptidase M it becomes homogeneous and is suitable for sequence determination. Based on the determination of the structures of two active fragments the complete amino acid sequence of mung bean trypsin inhibitor has been elucidated. It consists of 72 amino acid residues with 7 pairs of disulfide bonds. The results show that this inhibitor belongs to the Bowman-Birk inhibitor family.

Amino Acid Sequence↗