Performance characteristics of Mammalian Cell Culture process operating continuously with protein-free medium

In this communication we briefly describe a continuous industrial process for the production of Tissue Plasminogen Activator (tPA), operating with a standard, basal medium (DME/F12). Process data of two culture runs has been chosen to present a performance profile over a production period of more than 3 mo. Developmental aspects of glucose utilization (as a process parameter) are briefly discussed.     

Perchlorophenalenyl radical.

We report the preparation and solid-state characterization of the perchlorophenalenyl radical (1). The radical is initially obtained as a yellow-green solid by reduction of the perchlorophenalenium salt (12(+)). This solid sublimes in a sealed tube to give black shiny hexagonal crystals of the perchlorophenalenyl radical (1). The structure consists of 1-dimensional stacks of the monomeric radical. The peri-chlorine atoms force the phenalenyl system to be strongly nonplanar leading to a large separation between adjacent molecules within the stacks (3.78 A), and the molecules adopt two distinct stacking motifs (quasisuperimposed and rotated by 60 degrees with respect to neighbors). Because of the packing frustration in the lattice and the large intermolecular spacing, the solid shows Curie paramagnetism in the temperature range 100-400 K, before antiferromagnetic coupling sets in at low temperatures. Due to the narrow bandwidth that results from the isolation of the individual molecules, the solid is a Mott-Hubbard insulator, with a room-temperature conductivity of rho(RT) = 10(-10) S/cm.     

Two separate gene clusters encode the biosynthetic pathway for the meroterpenoids austinol and dehydroaustinol in Aspergillus nidulans

Meroterpenoids are a class of fungal natural products that are produced from polyketide and terpenoid precursors. An understanding of meroterpenoid biosynthesis at the genetic level should facilitate engineering of second-generation molecules and increasing production of first-generation compounds. The filamentous fungus Aspergillus nidulans has previously been found to produce two meroterpenoids, austinol and dehydroaustinol. Using targeted deletions that we created, we have determined that, surprisingly, two separate gene clusters are required for meroterpenoid biosynthesis. One is a cluster of four genes including a polyketide synthase gene, ausA. The second is a cluster of 10 additional genes including a prenyltransferase gene, ausN, located on a separate chromosome. Chemical analysis of mutant extracts enabled us to isolate 3,5-dimethylorsellinic acid and 10 additional meroterpenoids that are either intermediates or shunt products from the biosynthetic pathway. Six of them were identified as novel meroterpenoids in this study. Our data, in aggregate, allow us to propose a complete biosynthetic pathway for the A. nidulans meroterpenoids.     

Hysteretic spin crossover between a bisdithiazolyl radical and its hypervalent σ-dimer

The bisdithiazolyl radical 1a is dimorphic, existing in two distinct molecular and crystal modifications. The α-phase crystallizes in the tetragonal space group P4?2(1)m and consists of π-stacked radicals, tightly clustered about 4? points and running parallel to c. The β-phase belongs to the monoclinic space group P2(1)/c and, at ambient temperature and pressure, is composed of π-stacked dimers in which the radicals are linked laterally by hypervalent four-center six-electron S···S-S···S σ-bonds. Variable-temperature magnetic susceptibility χ measurements confirm that α-1a behaves as a Curie-Weiss paramagnet; the low-temperature variations in χ can be modeled in terms of a 1D Heisenberg chain of weakly coupled AFM S = (1)/(2) centers. The dimeric phase β-1a is essentially diamagnetic up to 380 K. Above this temperature there is a sharp hysteretic (T↑= 380 K, T↓ = 375 K) increase in χ and χT. Powder X-ray diffraction analysis of β-1a at 393 K has established that the phase transition corresponds to a dimer-to-radical conversion in which the hypervalent S···S-S···S σ-bond is cleaved. Variable-temperature and -pressure conductivity measurements indicate that α-1a behaves as a Mott insulator, but the ambient-temperature conductivity σ(RT) increases from near 10(-7) S cm(-1) at 0.5 GPa to near 10(-4) S cm(-1) at 5 GPa. The value of σ(RT) for β-1a (near 10(-4) S cm(-1) at 0.5 GPa) initially decreases with pressure as the phase change takes place, but beyond 1.5 GPa this trend reverses, and σ(RT) increases in a manner which parallels the behavior of α-1a. These changes in conductivity of β-1a are interpreted in terms of a pressure-induced dimer-to-radical phase change. High-pressure, ambient-temperature powder diffraction analysis of β-1a confirms such a transition between 0.65 and 0.98 GPa and establishes that the structural change involves rupture of the dimer in a manner akin to that observed at high temperature and ambient pressure. The response of the S···S-S···S σ-bond in β-1a to heat and pressure is compared to that of related dimers possessing S···Se-Se···S σ-bonds.