Characterization of the alkyl ether species of phosphatidylcholine in bovine heart

The molecular types of lecithin in beef heart lipids were investigated by a combination of mild hydrolytic procedures and silicic acid chromatography. The major species of sn-glycero-3-phosphorylcholine (GPC) were found to be: diacyl-GPC (57%), alk-l-enyl, acyl-GPC (39%), alkyl acyl-GPC (3%), and dialkyl-GPC ( less than 1%). No di-alk-l-enyl-GPC or alk-l-enyl alkyl-GPC were detected. The derived monoalkyl-and dialkyl-glycerols were characterized by their infrared spectra and alkyl chain compositions.     

Multi-type Galton-Watson process as a model for proliferating human tumour cell populations derived from stem cells: estimation of stem cell self-renewal probabilities in human ovarian carcinomas

A mathematical model for proliferation of tumour cell populations is developed. The cell population is assumed to be organized in a hierarchy of decreasing proliferative potential and increasing degree of differentiation. Using some elements of the theory of Multi-type Galton-Watson processes, a method is proposed for the estimation of Psr, the probability of self-renewal of tumour stem cells, from the experimental distribution of clonal unit sizes obtained in cell culture studies. Six data sets from patients with advanced adenocarcinoma of the ovary are used to demonstrate the method. Reasonable estimates are obtained, and the theoretical colony size distributions predicted by the model appear to be in good qualitative agreement with the experimental ones, and lend support to a stem cell model of tumour growth. The possible significance of Psr as a prognostic factor is briefly discussed.     

Improved synthesis and purification of Alzheimer's Aβ 1–42 and analogs

Fmoc-amino acid fluorides are highly efficient coupling agents for solution and solid-phase peptide synthesis and this property was used advantageously for the manual solid-phase assembly of the Alzheimer's Aβ 1–42 peptide [Milton et al., In Marshak, D. (Ed.) Techniques in Protein Chemistry, Vol. VIII, Academic Press, Orlando, FL, 1997, pp. 865–873]. Further studies comparing this methodology in the preparation of Aβ 1–42 peptide analogs employing a fully automated continuous-flow peptide synthesizer are reported.     

Polar lipids of non-alkaliphilic Halococci

Until recently, only one species of Halococcus has been recognized, namely, H. morrhuae, but a large number of extremely halophilic non-alkaliphilic cocci have now been isolated from hypersaline habitats in Spain and classified into four phenons (A-D); one of the phenon D strains has been classified as a new species, Halococcus saccharolyticus. Examination of the lipids of H. saccharolyticus and four strains of phenons A-C showed the presence in all of them of C20-C20 and C20-C25 diether molecular species of phosphatidylglycerophosphate (PGP), phosphatidylglycerol (PG) and phosphatidic acid (PA); a monounsaturated isoprenoid C20-C20 (phytanyl-phytenyl) species of PGP; a sulfated diglycosyl diphytanylglycerol (S-DGD) with structure 2,3-diphytanyl-1-(6-HSO3-mannosyl-1-2-glucosyl)-glycerol, which is identical to the S-DGD-1 in Haloferax mediterranei; a phosphoglycolipid (P-TGD) tentatively identified as a phytanyl-phytenyl-(H2PO3-galactosyl-mannosyl-glycosyl)-glyce rol, and two unidentified glycolipids present only in traces. No phosphatidylglycerosulfate (PGS) was detected in any of the strains examined. This pattern of lipids appears to be characteristic of the strains of Halococcus from salterns in Spain, but studies of a larger number and variety of Haloccus are necessary to establish this conclusion with certainty.