Thin-layer peptide mapping with sequencing at the nanomole level

The use of fluorescamine as a detection reagent in protein microcharacterization

With recent advances in protein microchemistry, compatible methods for the preparation and quantitation of proteins and peptides are required. Fluorescamine, a reagent which reacts with primary amino groups has been used successfully to detect amino acids, peptides, and proteins in various micromethods. This article discusses these methods which include (1) amino acid analysis of protein and peptide hydrolysates with postcolumn fluorescamine derivatization; (2) purification and characterization of proteins and peptides by reversed-phase HPLC with postcolumn fluorescamine derivatization; (3) purification of peptides by two-dimensional chromatography and electrophoresis on thin-layer cellulose with fluorescamine staining; and (4) electroblotting of protein bands from SDS-PAGE to glass fiber filters and polyvinylidene difluoride (PVDF) membranes with fluorescamine staining. In addition, this article also compares a postcolumn fluorescamine detection system with a UV detection system in the applications of amino acid analysis and reversed-phase HPLC protein/peptide analysis.

Naturally occurring methylation inhibitor: DNA hypomethylation and hemoglobin synthesis in human K562 cells

A naturally occurring methylation inhibitor isolated from rabbit liver and named methinin inhibits a number of methyltransferases. Methinin is a low-molecular-weight compound (1,400) that has an active amine group. This compound inhibits the DNA methyltransferase of human erythroleukemia cells (K562) in vitro. When the K562 cells were grown in medium containing methinin, fetal hemoglobin was produced. Small but detectable amounts of adult hemoglobin were also produced. Methinin was not toxic to these cells. The overall rate of genomic DNA methylation was reduced by 60% in cells grown in medium containing methinin. Southern blots of genomic DNA from methinin-treated cells and untreated cells hybridized to a 32P-labeled globin gene probe showed that one site in the globin gene region was hypomethylated. Methinin is a naturally occurring compound which inhibits DNA methylation both in vitro and in vivo.

Naturally occurring methylation inhibitor: DNA hypomethylation and hemoglobin synthesis in human K562 cells

A naturally occurring methylation inhibitor isolated from rabbit liver and named methinin inhibits a number of methyltransferases. Methinin is a low-molecular-weight compound (1,400) that has an active amine group. This compound inhibits the DNA methyltransferase of human erythroleukemia cells (K562) in vitro. When the K562 cells were grown in medium containing methinin, fetal hemoglobin was produced. Small but detectable amounts of adult hemoglobin were also produced. Methinin was not toxic to these cells. The overall rate of genomic DNA methylation was reduced by 60% in cells grown in medium containing methinin. Southern blots of genomic DNA from methinin-treated cells and untreated cells hybridized to a 32P-labeled globin gene probe showed that one site in the globin gene region was hypomethylated. Methinin is a naturally occurring compound which inhibits DNA methylation both in vitro and in vivo.

Larval salivary gland secretion proteins in Drosophila. Identification and characterization of the Sgs-5 structural gene

The 90BC locus on the polytene chromosomal map of Drosophila melanogaster contains the structural gene for a third-instar, salivary gland-specific, polyadenylated RNA (the group V RNA). This also belongs to the intermolt puff set whose dispersed and co-ordinately regulated members are (1) transcriptionally active in the salivary gland during the third-instar developmental stage and (2) comprise (at least in part) the structural genes for a set of salivary gland secretion proteins. Previous developmental studies of the group V intermolt gene (located cytogenetically within the 90B3-8 interval) suggest that it controls the expression of a salivary gland secretion protein. By analyzing different D. melanogaster laboratory stocks for variation in group V gene expression, we have been able to correlate the presence of the group V RNA with the salivary gland secretion protein P4. In vitro translation experiments show that the salivary gland messenger RNA population derived from a stock that fails to synthesize the group V RNA does not direct the synthesis of a polypeptide similar in molecular weight to protein P4. In addition, cloned genomic DNA segments complementary to the group V RNA are capable of arresting the in vitro translation of this protein. Comparative two-dimensional fractionation of cysteine-labeled, protease-generated peptides shows that (1) the in vitro translation product arrested by group V gene DNA is biochemically very similar to or identical with the salivary gland secretion protein P4, and (2) protein P4 is equivalent to the salivary gland secretion protein previously designated SGS-5. Since designations of the latter type have been employed in naming the genetic loci that represent the structural genes for the salivary gland secretion protein gene set, the group V gene (previous designation) represents the SGS-5 structural gene and its appropriate genetic designation should now be Sgs-5.