Mechanism of enhancement in absorbance of vibrational bands of adsorbates at a metal mesh with subwavelength hole arrays

We have investigated the mechanism of enhanced absorption intensities of vibrational bands of adsorbates on copper meshes with subwavelength holes by measuring and simulating temporal profiles of infrared pulses transmitted through the meshes. As reported previously [Williams et al., J. Phys. Chem. B, 2003, 107, 11871], the absorption intensities of CH stretching bands of alkanethiolate adsorbed on the mesh increase substantially with decreasing hole size. The enhancements of absorption intensities are associated with temporal delays of infrared pulses transmitted through the mesh. Finite difference time domain calculations reproduce the observed pulse delays as a function of hole size. These facts indicate that the delays of transmitted pulses are not caused by coupling of infrared radiation to surface plasmon polaritons propagating on the front and rear surfaces of the mesh, but they are caused by the reduction in group velocity owing to coupling to waveguide modes of mesh holes. Consequently, the strong enhancements of the absorption intensities are attributed to adsorbates inside the holes rather than to those on the mesh surfaces that have been proposed previously.     

Interlaboratory study of DNA extraction from multiple ground samples, multiplex real-time PCR, and multiplex qualitative PCR for individual kernel detection system of genetically modified maize

In many countries, the labeling of grains, feed, and foodstuff is mandatory if the genetically modified (GM) organism content exceeds a certain level of approved GM varieties. We previously developed an individual kernel detection system consisting of grinding individual kernels, DNA extraction from the individually ground kernels, GM detection using multiplex real-time PCR, and GM event detection using multiplex qualitative PCR to analyze the precise commingling level and varieties of GM maize in real sample grains. We performed the interlaboratory study of the DNA extraction with multiple ground samples, multiplex real-time PCR detection, and multiplex qualitative PCR detection to evaluate its applicability, practicality, and ruggedness for the individual kernel detection system of GM maize. DNA extraction with multiple ground samples, multiplex real-time PCR, and multiplex qualitative PCR were evaluated by five laboratories in Japan, and all results from these laboratories were consistent with the expected results in terms of the commingling level and event analysis. Thus, the DNA extraction with multiple ground samples, multiplex real-time PCR, and multiplex qualitative PCR for the individual kernel detection system is applicable and practicable in a laboratory to regulate the commingling level of GM maize grain for GM samples, including stacked GM maize.     

Excellent chiralselectivity in sulfur-bridged CoIIIMCoIII (M = NiII and PdII) trinuclear complexes containing 1,2-cyclohexanediamine

The reaction of [Ni(aet)2] with [CoCl2(R,R-chxn)2]+ (aet = 2-aminoethanethiolate, R,R-chxn = 1R,2R-cyclohexanediamine) in water gave a CoIIINiIICoIII trinuclear complex, DeltaRRDeltaRR-[Ni(Co(aet)(2-)(R,R-chxn))2]4+ ([1a]4+), in which two cis(S)-[Co(aet)2(R,R-chxn)]+ units are linked by a central NiII ion through sulfur bridges. The two CoIII units in [1a]4+ uniformly adopt the Delta configuration, which is induced by the chirality of the terminal R,R-chxn ligands. The central NiII ion in [1a]4+ was replaced by a PdII ion to produce an analogous CoIIIPdIICoIII trinuclear complex, DeltaRRDeltaRR-[Pd(Co(aet)2(R,R-chxn))2]4+ ([2a]4+), with retention of the Delta configuration. When racemic R,R/S,S-chxn was employed instead of R,R-chxn, not only the chirality about two CoIII centers but also the chirality about two chxn ligands was unified in the S-bridged trinuclear structure, leading to the selective formation of a pair of enantiomers, DeltaRRDeltaRR/LambdaSSLambdaSS-[M(Co(aet)2(chxn))2]4+ (M = NiII ([1b]4+) and PdII ([2b]4+)). The stereochemical and spectroscopic features of these complexes are discussed on the basis of the electronic absorption, CD, and NMR spectroscopies, along with the crystal structures of [1a]4+ and [2a]4+.     

Formation,Expansion, and Interconversion of Metallarings in a Sulfur‐Bridged AuICoIII Coordination System

A novel Au^ICo^III coordination system that is derived from the newly prepared [Co(D ‐nmp)₂]⁻ ( 1 ⁻; D ‐nmp=N‐methyl‐D ‐penicillaminate) and a gold(I) precursor Au^I is reported. Complex 1 ⁻ acts as a sulfur‐donating metallaligand and reacts with the gold(I) precursor to give [Au₂Co₂(D ‐nmp)₄] ( 2 ), which has an eight‐membered Au^I₂Co^III₂ metallaring. Treatment of 2 with [Au₂(dppe)₂]²⁺ (dppe=1,2‐bis(diphenylphosphino)ethane) leads to the formation of [Au₄Co₂(dppe)₂(D ‐nmp)₄]²⁺ ( 3 ²⁺), which consists of an 18‐membered Au^I₄Co^III₂ metallaring that accommodates a tetrahedral anion (BF₄⁻, ClO₄⁻, ReO₄⁻). In solution, the metallaring structure of 3 ²⁺ is readily interconvertible with the nine‐membered Au^I₂Co^III metallaring structure of [Au₂Co(dppe)(D ‐nmp)₂]⁺ ( 4 ⁺); this process depends on external factors, such as solvent, concentration, and nature of the counteranion. These results reveal the lability of the Au S and Au P bonds, which is essential for metallaring expansion and contraction.     

Antioxidant activity and Neurite outgrowth-enhancing activity of scorbamic acid and a red pigment derived from ascorbic acid

Abstract

L-Ascorbic acid (AA), known as vitamin C, can form browning products by a non-enzymatic process during storage and the browning products cause deterioration of agricultural products. In the browning reaction, a red pigment, 2,2´-nitrilodi-2(2´)-deoxy-L-ascorbic acid ammonium salt (NDA), is generated from AA via L-scorbamic acid (SCA) as an intermediate. However, the biological activities of SCA and NDA have not yet been clarified. In this study, we assayed the antioxidant activities of SCA and NDA using ABTS radical cation and their neurite outgrowth-enhancing activities in PC12 cells. SCA showed stronger radical-scavenging activity than that of AA, while NDA hardly showed any activity. SCA and NDA enhanced the neurite outgrowth induced by dibutyryl cyclic AMP after their incorporation into cells in the same manner as that of AA. The results indicated that SCA has antioxidant activity and that SCA and NDA have neurite outgrowth-enhancing activity.     

Theoretical investigation of the stability of highly charged C60 molecules produced with intense near-infrared laser pulses

We theoretically investigated the stability of highly charged C(60) (z+) cations produced from C(60) with an ultrashort intense laser pulse of lambda approximately 1800 nm. We first calculated the equilibrium structures and vibrational frequencies of C(60) (z+) as well as C(60). We then calculated key energies relevant to dissociation of C(60) (z+), such as the excess vibrational energy acquired upon sudden tunnel ionization from C(60). By comparing the magnitudes of the calculated energies, we found that C(60) (z+) cations up to z approximately 12 can be produced as a stable or quasistable (microsecond-order lifetime) intact parent cation, in agreement with the recent experimental report by V. R. Bhardwaj et al. [Phys. Rev. Lett. 93, 043001 (2004)] that almost only intact parent C(60) (z+) cations up to z=12 are detected by a mass spectrometer. The results of Rice-Ramsperger-Kassel-Marcus calculation suggest that the lifetime of C(60) (z+) drastically decreases by ten orders of magnitude as z increases from z=11 to z=13. Using the time-dependent adiabatic state approach, we also investigated the vibrational excitation of C(60) and C(60) (z+) by an intense near-infrared pulse. The results indicate that large-amplitude vibration with energy of >10 eV is induced in the delocalized h(g)(1)-like mode of C(60) (z+).