The temperature-induced beta-hairpin stabilities of selected mutations of the Trpzip1 peptide, SWTWEGNKWTWK (WWWW), have been investigated by electronic circular dichroism (CD), Raman, and FT-IR spectroscopies. The tryptophan (Trp) residues in the original Trpzip1 sequence were systematically substituted with tyrosine (Tyr) in different positions to test the impact of Trp interactions on the beta-hairpin structure and stability. The CD intensity at approximately 228 nm, which arises from Trp-Trp interactions (tertiary structure), and the amide I' IR absorbance at approximately 1635 cm(-1) (secondary structure) have been measured over a range of temperatures to investigate the impact of Tyr substitution on beta-hairpin thermal stability in Trpzip peptides. Mutation from Trp to Tyr in the Trpzip1 sequence reduces the extent of beta-hairpin structure and monotonically decreases the beta-hairpin stability of Trpzip1 mutant peptides with an increasing number of Tyr substitutions. Substituted Trpzip peptides with just one pair of Trp-Trp interactions close to either the terminal residues (WYYW) or the turn (YWWY) have similar stabilities. Comparison of conformational transitions monitored by CD and IR reveals them to have multistate behavior in which the temperature-induced disruption of the Trp-Trp interaction (tertiary structure) occurs at a lower temperature than the unfolding of the secondary structure.

Harvesting solar light to boost commercially important organic synthesis still remains a challenge. Coupling of conventional noble metal catalysts with plasmonic oxide materials which exhibit intense plasmon absorption in the visible light region is a promising option for efficient solar energy utilization in catalysis. Herein, we for the first time demonstrate that plasmonic hydrogen molybdenum bronze coupled with Pt nanoparticles (Pt/H MoO) shows a high catalytic performance in the deoxygenation of sulfoxides with 1 atm of H at room temperature, with dramatic activity enhancement under visible light irradiation relative to dark conditions. The plasmonic molybdenum oxide hybrids with strong plasmon resonance peaks pinning at around 556 nm are obtained via a facile H-spillover process. Pt/H MoO hybrid provides excellent selectivity for the deoxygenation of various sulfoxides as well as pyridine N-oxides, in which drastically improved catalytic efficiencies are obtained under the irradiation of visible light. Comprehensive analyses reveal that oxygen vacancies massively introduced via a H-spillover process are the main active sites, and the reversible redox property of Mo atoms and strong plasmonic absorption play key roles in this reaction. The catalytic system works under extremely mild conditions and can boost the reaction by the assistance of visible light, offering an ultimately greener protocol to produce sulfides from sulfoxides. Our findings may open up a new strategy for designing plasmon-based catalytic systems that can harness visible light efficiently.

The varying states of water confined in the nano-domain structures of typical room temperature ionic liquids (ILs) were investigated by 1H NMR and by measurements of self-diffusion coefficients while systematically varying the IL cations and anions. The NMR peaks for water in BF4-based ILs were clearly split, indicating the presence of two discrete states of confined water (H2O and HOD). Proton and/or deuterium exchange rate among the water molecules was very slowly in the water-pocket. Notably, no significant changes were observed in the chemical shifts of the ILs. Self-diffusion coefficient results showed that water molecules exhibit a similar degree of mobility, although their diffusion rate is one order of magnitude faster than that of the IL cations and anions. These findings provide information on a completely new type of confinement, that of liquid water in soft matter.