Structures and Biosynthesis of Caryoynencins, Unstable Bacterial Polyynes from Pseudomonas protegens Recombinant Expressing the cayG Gene.

Bacteria in certain genera can produce "bacterial polyynes" that contain a conjugated C≡C bond starting from a terminal alkyne. Protegenin A is a derivative of octadecanoic acid that contains an ene-tetrayne moiety. It was discovered in Pseudomonas protegens Cab57 and exhibits strong antioomycete and moderate antifungal activity. By introducing cayG, a cytochrome P450 gene from Burkholderia caryophylli, into P. protegens Cab57, protegenin A was converted into more complex polyynes, caryoynencins A-E. A purification method that minimized the degradation and isomerization of caryoynencins was established. For the first time, as far as we know, the 1H and 13C{1H} NMR signals of caryoynencins were completely assigned by analyzing the NMR data of the isolated compounds and protegenin A enriched with [1-13C]- or [2-13C]-acetate. Through the structural analysis of caryoynencins D/E and bioconversion experiments, we observed that CayG constructs the allyl alcohol moiety of caryoynencins A-C through sequential hydroxylation, dehydration, and hydroxylation. The recombinant strain exhibited a stronger antioomycete activity compared to the wild-type strain. This paper proposes a stable purification and structural determination method for various bacterial polyynes, and P. protegens Cab57 holds promise as an engineering host for the production of biologically active polyynes.

Dressed-photon-phonon (DPP)-assisted visible- and infrared-light water splitting.

A dressed-phonon-phonon (DPP) assisted photocatalyst reaction was carried out to increase the visible light responsibility, where the photon energy of the radiation, which ranged from visible to infrared light is less than band gap energy of the photocatalyst (ZnO, 3.3 eV). The dependence of the photocurrent on excitation power indicated that two-step excitation occurred in DPP-assisted process. A cathodoluminescence measurement also supported the conclusion that the visible- and infrared-light excitation originated from DPP excitation, not from defect states in the ZnO nanorod photocatalyst.

Site-selective deposition of gold nanoparticles using non-adiabatic reaction induced by optical near-fields.

In this paper, we report on site-selective deposition of metal nanoparticles using a non-adiabatic photochemical reaction. Photoreduction of gold was performed in a silica gel membrane containing tetrachloroaurate (AuCl(4)( - )) ions, using ZnO nanorods as the sources of optical near-field light, resulting in deposition of gold nanoparticles with an average diameter of 17.7 nm. The distribution of distances between the gold nanoparticles and nanorod traces revealed that the gold nanoparticles were deposited adjacent to the ZnO nanorods, reflecting the attenuation of the optical near-fields in the vicinity of the ZnO nanorods. We found that the emission wavelength from the ZnO nanorods was longer than the absorption edge wavelength of the tetrachloroaurate. Additionally, from the intensity distribution obtained by a finite-difference time-domain method, the gold deposited around the ZnO nanorods was found to be due to a non-adiabatic photochemical reaction.