Searching for new TNF-alpha analogs having potential application in cancer therapy.

Two new TNF-alpha analogs were prepared and tested for their anti-tumor activity on fibrosarcoma SA-1 tumor model in vivo. In analog LK-801 two histidines (His107His108) were introduced into the surface loop thus enabling efficient purification by metal-affinity chromatography. This analog showed less side effects and can serve as a lead compound to look for other useful mutations. Another analog LK-802 was designed by introduction of additional pair of mutations (Cys95Cys148) into LK-801 in order to prepare disulfide linked TNF trimers. Cytotoxicity on mouse cell line L929 was comparable to TNF-alpha, but effect on tumor growth was quite reduced. Pharmacokinetic study revealed that serum levels of LK-802 were quite low in comparison to native TNF-alpha. This at least partially explains why anti-tumor activity of LK-802 is reduced and also illustrates the problems in designing the analogs with desired in vivo biological properties.

Purification of human tumour necrosis factor by membrane chromatography.

The recombinant human tumour necrosis factor alpha from an extract of Escherichia coli was enriched to homogeneity according to specific activity and sodium dodecyl sulphate-polyacrylamide gel electrophoresis by purification using anion-exchange HPLC and hydrophobic interaction HPLC. Parallel experiments with the same separation methods, but carried out with membrane chromatography on compact discs, gave similar results in terms of yield and purity of the product. The active form of the protein is a trimer. The second isolation step, hydrophobic interaction chromatography, causes dissociation of the trimer into monomers and a partial loss of the biological activity of the protein. The phenomenon occurs on both the column and the disc. This in turn indicates strongly that the dissociation of the protein is a consequence of interaction between the samples and the hydrophobic ligand, and is not caused by non-specific interaction with the matrix.

Mathematical modeling of growth and alkaloid production in Claviceps purpurea batch fermentation.

An new systematic approach for describing Claviceps purpurea growth and ergot alkaloid production during batch fermentation is presented. The model is based on microbial life, as the main characteristic for microbial development during fermentation process. The aging process of the microorganism is represented by life function, defined in microbial life space. The life space is defined as a measure in which the observer follows the development of a biosystem through physiological and morphological changes of a microorganism. As a consequence of such approach the relativistic theory is recognized. To validate the model developed, a test on growth and alkaloid synthesis data from an industrial batch fermentation was performed.

Activation of ergot alkaloid biosynthesis in prototrophic isolates by Claviceps purpurea protoplast fusion.

Intraspecific protoplast fusions were carried out with active ergocornine-ergokryptine and inactive ergocristine Claviceps purpurea strains and vice versa. The isolated prototrophic strains from both types of crossings produced all three alkaloid types, showing that biosynthesis of distinct alkaloid was activated in an inactive partner strain. The prototrophic isolates were stable on minimal medium but they segregated by subculturing on complete medium. In comparison with the original partner strains, differences in morphological and cytological characteristics were also established.

Metabolic changes in a conidia-induced Claviceps paspali strain during submerged fermentation.

Chemical changes in the mycelium of the conidial Claviceps paspali mutant strain, isolated after gamma irradiation, were followed during the course of submerged fermentation and compared with the mycelial parent strain; both strains are capable of producing simple lysergic acid derivatives. The syntheses of lipids, carbohydrates, phosphates, nucleic acids, proteins, and alkaloids, as well as nutrient uptake, were determined. It was found that conidiation induced by mutagenic treatment was accompanied by a set of changes in the metabolic pattern. In the conidial mutant, the primary and secondary metabolic activities were repressed and the protein to nonprotein compound ratio of the cells was changed in favour of protein compounds.

Developmental studies of Claviceps paspali seed cultures for the submerged production of lysergic acid derivatives.

Metabolic pattern of mycelial Claviceps paspali seed cultures during the submerged cultivation was established. By comparing it with conidial and mycelial Claviceps purpurea strains it was found that the biosynthesis of RNA, DNA, and proteins followed a similar course in all Claviceps strains, so the fall of RNA content in mycelium may be considered a general biochemical indicator for optimally developed inoculum. But, two different patterns of carbohydrate and lipid metabolism were observed one for conidial and one for mycelial strains.