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Partition System (partition + system)
Selected AbstractsHuman skin permeation and partition: General linear free-energy relationship analysesJOURNAL OF PHARMACEUTICAL SCIENCES, Issue 6 2004Michael H. Abraham Abstract Literature values of the permeability coefficient for permeation of human skin from water have been adjusted for ionization in water and adjusted for temperature. The obtained values of log Kp for 119 solutes at 37°C have been correlated with Abraham descriptors to yield an equation with R2,=,0.832 and SD,=,0.46 log units. Three separate test sets of 60 compounds had log Kp predicted with an SD of 0.48 log units. The main factors that influence log Kp are solute hydrogen bond basicity that lowers the permeability coefficient and solute volume that increases the permeability coefficient. Human skin,water partition coefficients, as log Ksc, have been collected for 45 compounds and yield an equation with R2,=,0.926 and SD,=,0.22 log units. We have compared the log Kp equation to equations for various other processes, but have found no process that appears to be similar to that for skin permeation. The nearest process to skin,water partition is the isobutanol,water partition system. An equation for lateral diffusion in the stratum corneum is shown to be reasonably close to various diffusion-related processes. © 2004 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 93:1508,1523, 2004 [source] Partition operon expression in the linear plasmid prophage N15 is controlled by both Sop proteins and protelomeraseMOLECULAR MICROBIOLOGY, Issue 2 2003Boris D. Dorokhov Summary The temperate coliphage N15, unlike most low copy-number prokaryotic replicons, is maintained as a linear DNA molecule with covalently closed ends. Accurate partitioning of the plasmid prophage is assured by a close homologue of the sop locus of the F plasmid. However, the region upstream of the N15 sopAB genes contains multiple putative promoters, in contrast to F sop whose expression is driven by one negatively autoregulated promoter. In addition, the centromere of N15 is represented by four inverted repeats located at widely separated sites within the region essential for replication and control of lytic functions. We have analysed expression of N15 sop genes. We find that transcription of N15 sop is driven by two major promoters. The first, P1, is similar in sequence and function to the F sop promoter; it is repressed by Sop proteins. The second promoter, P2, is upstream of P1 and is several times stronger. It is insensitive to regulation by Sop proteins but is tightly repressed by protelomerase, the N15 enzyme that completes prophage replication by generating hairpin telomeres. These results establish a regulatory link between the partition system and other processes of N15 maintenance. [source] Application of a PEG/salt aqueous two-phase partition system for the recovery of monoclonal antibodies from unclarified transgenic tobacco extractBIOTECHNOLOGY JOURNAL, Issue 9 2009Dimitris Platis Abstract Aqueous two-phase partition systems (ATPS) have been widely used for the separation of a large variety of biomolecules. In the present report, the application of a polyethylene glycol/phosphate (PEG/phosphate) ATPS for the separation of anti-HIV monoclonal antibodies 2G12 (mAb 2G12) and 4E10 (mAb 4E10) from unclarified transgenic tobacco crude extract was investigated. Optimal conditions that favor opposite phase partitioning of plant debris/mAb as well as high recovery and purification were found to be 13.1% w/w (PEG 1500), 12.5% w/w (phosphate) at pH 5 with a phase ratio of 1.3 and 8.25% w/w unclarified tobacco extract load. Under these conditions, mAb 2G12 and mAb 4E10 were partitioned at the bottom phosphate phase with 85 and 84% yield and 2.4- and 2.1-fold purification, respectively. The proposed ATPS was successfully integrated in an affinity-based purification protocol, using Protein A, yielding antibodies of high purity and yield. In this study, ATPS was shown to be suitable for initial protein recovery and partial purification of mAb from unclarified transgenic tobacco crude extract. [source] | ||||||||||