Australasian biotechnology最新文献

Peptide libraries are relatively new sources of enormous numbers of unique compounds, fodder for the mill of drug discovery programs. Their enormous diversity derives from vast numbers of combinations of a small number of monomers (Geysen et al., 1986). For example, a complete hexapeptide library synthesized from just 10 monomers (amino acids) has one million unique compounds in it. In principle, other types of combinatorial libraries can have equally vast numbers of members; for example, the monomers can be N-acyl glycines, giving rise to the so-called "peptoids" (Simon et al., 1992); or the monomers could be monosaccharides or nucleotides.

The application of crossflow microfiltration (CFMF) to processing cell suspensions was proposed in the 1970s. The intervening years have seen the scaling up of the technology to commercial operation and have been a period of intense research interest in the physics of the process. Flaschel et al. (1983) noted that the recovery of biomass (by ultrafiltration) appeared still to be in the phase of development. Later reviews particularly commented on the proprietary nature of much of the useful information required to assess the feasibility of CFMF (Hanisch, 1986; Brown & Kavanagh, 1987), but while the need for further publication of some information is still being stressed (e.g. Heath and Belfort, 1992), detailed reports from biotechnology companies of lab-, pilot- and full-scale applications are now appearing in the literature (Bailey et al., 1990, Sheehan et al, 1990; van Reis et al., 1991). The objective of this review is to describe the major factors influencing CFMF of cell suspensions with particular reference to the recent literature.

The world-wide project to map the human genome contains great promise for identifying the genetic determinants of disease and the development of gene therapies. However, at the same time it creates extensive possibilities for breaches of human rights, for the development of social policies of a eugenic kind and for the invasion of privacy and the use of genetic information for other than medical purposes. This article provides a broad overview of the possibilities.

The effects of medium composition, temperature and tryptophan concentration on the growth and expression of a recombinant E. coli producing human tumour necrosis factor-beta (TNF-beta) were examined in shake flask cultures. We found that lower cultivation temperatures of 25 degrees C and 30 degrees C gave the best yield of soluble TNF-beta. A higher expression of total TNF-beta was obtained in defined medium. Fed-batch fermentations further confirmed that a lower mu was critical to obtaining high TNF-beta expression. This was shown to be due to the dilution effect at high mu, which affected the cell plasmid content. We found that we were unable to repress TNF-beta expression with tryptophan and TNF-beta was expressed in non-induced cultures. This has been attributed to the nature of the constructed clone, which is a low aporepressor producer, but carried a high copy number plasmid with a mutated rom gene. A rapid and improved method for the purification of TNF-beta has also been developed. The method utilised sequential steps of polyethyleneimine (PEI) and ammonium sulphate precipitation to remove most of the extraneous proteins and nucleic acids from the cell extracts. This was followed by DEAE chromatography. This procedure was found to be highly efficient and was used to purify large quantities of TNF-beta. Compared to an earlier protocol which did not include the PEI step, yields were higher and processing time was much shorter.