The genetically well-known strain Streptomyces coelicolor A3(2) produces the pH indicator (red/blue) antibiotic actinorhodin, but not all the ''blue pigment'' produced by this strain is actinorhodin. When the organism was subjected to various nutrient limitations (ammonium, nitrate, phosphate, or trace elements), and also during growth cessation caused by a relatively low medium pH, blue pigment production was initiated but the pigment and its location varied. At pH 4.5 to 5.5, significant formation of actinorhodin occurred and was located exclusively intracellularly. At pH 6.0 to 7.5 a different blue pigment was produced intracellularly as well as extracellularly. It was purified and identified as ␥-actinorhodin (the lactone form of actinorhodin). Analysis of act mutants of S. coelicolor A3(2) confirmed that both pigments are derived from the act biosynthetic pathway. Mutants with lesions in actII-ORF2, actII-ORF3, or actVA-ORF1, previously implicated or suggested to be involved in actinorhodin export, were impaired in production of ␥-actinorhodin, suggesting that synthesis of ␥-actinorhodin from actinorhodin is coupled to its export from the cell. However, effects on the level of actinorhodin production were also found in some mutants.

Synthetic routes to alternating copolymers consisting of oligosilylene blocks and oligothiophene blocks (Tz; x = 1, 2, 3, 4, or 6 rings) are presented. Solubility requirements for obtaining acceptable molecular weights and, eventually, for film formation are met by the introduction of butyl groups replacing methyls on the silicon atoms and by employing Ts blocks carrying two octyl substituents. Additionally, substituted oligothiophenes are synthesized as an aid in the interpretation of NMR, absorption, and fluorescence spectra. Regarding the electronic configuration of the oligothiophene blocks, NMR spectra show clear differences between plain oligothiophenes, end-substituted oligothiophenes, and polymers, indicative of n-a interactions with the oligosilylene blocks and possible through-conjugation to adjacent blocks in polymers. Red shifts in optical spectra show a parallel trend across the various compounds based on the same oligothiophene unit, related to the stabilization of photoexcited states on the oligothiophene by the oligosilylene substituents. These effects are strong in Tz-based compounds and reduced for longer T,. The main feature of the spectra is the decrease of the transition energies with the size of the oligothiophene blocks in the polymers. Since this effect is also found in fluorescence, it enables one to adjust the luminescence wavelength by choosing the proper block length ("chemical tuning"). Fluorescence quantum efficiencies in solution are found to be remarkably high in polymers based on Tz blocks. Spin-coated films of Tz-based (or Ts-based) polymers show evidence of Tq (Ts) impurity blocks that act as an exciton trap.

The combination of wide‐ and narrow‐band‐gap polymers in a block copolymer can provide a means of increasing the luminescence efficiency of the materials. This occurs because the excitons that are formed are trapped within specific units in the polymer chains and therefore cannot migrate to quenching sites caused by the presence of dopants. Color‐tunability is also possible through adjusting the band gaps of the components. Devices based on silanylene'thiophene lock copolymers are reproted.

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