The impact of different fixation procedures on staining of macromolecules in a microtiter system

Summary The effects of formaldehyde, glutaraldehyde, methanol, Clarke's fixative and microwave irradiation on the quantitative staining of proteins (Naphthol Yellow S) and nucleic acids (Ethyl Green—Pyronin) in a cell culture system have been investigated. Overall, glutaraldehyde rapidly yielded the highest and most consistent levels of staining when compared to all other chemical fixatives. Although microwave irradiation was found to be uneven, 4 min exposure to 700W was found to give higher levels of protein staining than those achieveable with glutaraldehyde. Time-dependent processes were observed with all procedures. In addition, dissociations in the trends of protein and nucleic acid staining were observed. It is suggested that these results domonstrate fixation events that have not previously been resolved from the effects of reagent penetration into tissue blocks.     

Primary structure of a Plasmodium falciparum malaria antigen located at the merozoite surface and within the parasitophorous vacuole

DNA encoding an antigen of 101,000 apparent molecular weight from the human malaria parasite Plasmodium falciparum was cloned and sequenced. Genomic DNA from the Camp strain covering the complete coding region along with cDNA from the FCR3 strain covering 81% of the coding region were obtained. The cloned DNA specified a full-length protein of 743 amino acids which included two tandemly repeated regions, one near the amino terminus containing eight hexapeptide repeats of sequence TVNDEDED, and the second near the carboxyl terminus containing primarily KE and KEE repeats. The latter repeated region is encoded by a 174-base stretch of mRNA containing only a single pyrimidine. Except for a putative leader sequence located at the amino terminus of the protein, the protein is hydrophilic and highly charged with a calculated isoelectric point of 5.6. Sequences from the Camp and FCR3 strains are very close and are also nearly identical to the partial cDNA sequence of the acidic basic repeated antigen (ABRA) protein from the FC27 strain (Stahl, H.D., Bianco, A.E., Crewther, R.F., Anders, R.F., Kyne, A.P., Coppel, R. L., Mitchell, G.F., Kemp, D.J., and Brown, G.V. (1986) Mol. Biol. Med. 3, 351-368). ABRA was previously shown to be located at the merozoite surface and in the parasitophorous vacuole. Because of its location and because it becomes complexed to merozoites when schizonts rupture in the presence of immune serum, ABRA is a candidate component of a malaria vaccine.     

Specific chemical modifications of link protein and their effect on binding to hyaluronate and cartilage proteoglycan

Specific chemical modifications of amino acid residues were performed on purified, native link protein from bovine articular cartilage. The effects of these on link protein's interactions with hyaluronate and bovine articular cartilage proteoglycan were assayed by gel chromatography. Interaction with hyaluronate was significantly perturbed by modification of lysine, arginine, tyrosine and aspartic/glutamic acid residues, but not histidine and tryptophan residues. No free, accessible sulphydryl group was found on native link protein. The requirement for unmodified lysine and arginine residues resembles that of the hyaluronate-binding site of pig laryngeal cartilage proteoglycan (Hardingham, T.E., Ewins, R.J.F. and Muir, H. (1976) Biochem. J. 157, 127-143). In contrast, proteoglycan binding was only significantly perturbed by the loss of arginine residues. This resistance may reflect hydrophobicity of the binding site or masking of the site from chemical modification by link protein self-association. Amidation of carboxyl groups, which destroyed hyaluronate binding but left proteoglycan binding intact, provides a means of generating a monofunctional link protein molecule of potential use in proteoglycan aggregation studies.     

Chromosomal location of TOL plasmid DNA in Pseudomonas putida.

The soil isolate Pseudomonas putida MW1000 can grow on toluene and other hydrocarbons; in this respect it is similar to strains of Pseudomonas which carry the TOL plasmid. By conjugation experiments, the genes conferring these growth abilities have been shown to be located on the bacterial chromosome, linked to vil and catB. A 56-kilobase segment of the bacterial chromosome of MW strains carrying the TOL genes can transpose to the IncP-1 plasmid R18-18. Physical analysis of these TOL R18-18 hybrids has shown that the TOL segment is almost identical to the same region found in the TOL plasmid pWW0.