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Trigger factor, a ribosome-associated chaperone and peptidyl-prolyl cis-trans isomerase (PPIase), is essential for the secretion and maturation of the cysteine protease of the pathogenic gram-positive bacterium Streptococcus pyogenes. In the absence of trigger factor, the nascent protease polypeptide is not targeted to the secretory pathway. Some partial-function mutations restore targeting. However, the secreted protease does not efficiently mature into an enzymatically active form, suggesting that trigger factor has an additional role in protease biogenesis. Here, we show that, while not required for targeting, the PPIase activity of trigger factor is essential for maturation of the protease following its secretion from the bacterial cell. Site-specific mutations introduced into ropA, the gene which encodes trigger factor in S. pyogenes, produced mutant proteins deficient in PPIase activity. When these mutant alleles were used to replace the wild-type gene on the streptococcal chromosome, analysis of protease biogenesis revealed that, although the protease was secreted normally, it did not efficiently mature to an active form. Furthermore, mutation of a single proline residue in the protease prodomain suppressed the requirement for PPIase activity, suggesting that this residue is the target of trigger factor. These data support a model in which trigger factor-mediated prolyl isomerization influences the conformation of the prodomain, which in turn directs the protease into one of several alternative folding pathways.

Solar light was used to examine the photochemical phase in the synthesis of vitamin D3 in an aqueous solution of poly(sodium styrenesulfonate-co-2-vinylnaphthalene) (PSSS-VN), to introduce the use of photoenzymes as microphotoreactors. Solar energy was applied to initiate useful and specific syntheses of organic compounds in water solution. The pendant naphthalene chromophores in the copolymer photosensitized the photoisomerization of 7-dehydrocholesterol to previtamin D3 through singlet-singlet energy transfer. The triplet-sensitized isomerization of tachysterol to previtamin caused the absence of tachysterol, an important side product developed during photoisomerization in organic solution. The high regional concentration of tachysterol near the energy donors enhances the efficacy of triplet-triplet energy transfer from activated polymeric naphthalene chromophores to tachysterol.

The influence on the spectroscopic and isomerization behavior of compounds in the presence of substituents on the azobenzenes phenyl rings is examined. The evaluation of the branching ratio for isomerization and the rate of trans isomer recovery is discussed.

Investigations about the photoisomerization of naphthopyran derivatives revealed that the light intensity influences the photodecoloration quantum yield of a naphthopyran derivative 1, and that the yellow napthopyran 1 isomerized to a colorless bicyclohexene, isomer 2, through an unstable intermediate, a two-photon mechanism. Upon irradiation with 334-nm light, the bicyclohexene isomer reverted to the original naphthopyran. Bleaching is almost nonexistent when the light intensity is poor, even after continued irradiation, but with high intensity light, the yellow color vanishes instantly.

Studies prove that the kinetics of substrate association to the biomaterial can be photoregulated by examining the photoregulated kinetics of association of a spiropyran-altered conconavalin A (Con A) to monosaccharide monolayers integrated on gold electrodes. The disturbance of the protein binding region in configuration 2b, by electrostatic interaction and the steric disruption of the protein backbone, causes the associated photoactivated mechanism. The photocontrolled binding kinetics of the substrate are caused by the photoisomerization of spiropyran units covalently connected to Con A.