Chiral recognition of thiaheterohelicenes by alkyl beta-D-pyranoside micelles. Influence of extension of helix

Chiral recognition of alkyl beta-D-pyranoside micelles toward [7] and [5] heterohelicenes possessing helical structures was investigated by 1H-NMR and CD (circular dichroism) spectroscopy. In dodecyl maltopyranoside micellar solution, P and M enantiomers of tetrathia[7]heterohelicene (7TH), which have rigid and stable helixes, manifested different chemical shifts in their 1H-NMR spectra due to differences in the diastereomeric interactions, implying that the micelles undergo stronger recognition toward the M enantiomer than the P enantiomer. On the other hand, in octyl glucopyranoside micellar solution, trithia[5]heterohelicene (5TH) and two kinds of its derivatives which are rapidly equilibrated between the enantiomers in solution, gave no distinctly resolved 1H-NMR peaks for either enantiomer even at a lowered temperature. However, these racemic [5]heterohelicenes in the micelles did develop induced CD absorptions owing to a displacement of the equilibrium, suggesting from the signs of their Cotton effects that the micelles prefer the M enantiomer to its antipode in conformity with the 1H-NMR results of 7TH.     

Amino acids and peptides. XXXVIII. Facile synthesis of laminin-related peptide-poly(ethylene glycol) hybrids by the solid phase method

Poly(ethylene glycol) (PEG) has been studied as a drug-carrier for proteins, but not for small peptides. Laminin, a cell adhesive protein, has Tyr-Ile-Gly-Ser-Arg (YIGSR) sequence and peptides containing this sequence inhibit experimental metastasis. We have studied PEG hybrids of YIGSR and other small laminin-related peptides. In a previous paper, we reported preparation of YIGSR-PEG hybrids by combination of the solid phase method and the solution method, but the synthetic procedure was problematic. Here we report a facile synthesis of PEG hybrids of YIGSR (PEG-YIGSR, YIGSR-PEG, PEG-YIGSR-PEG) by the solid phase method.     

Limonoids from Citrus sudachi

Four new limonoid derivatives, 1-O-methylichangensin (1), sudachinoid A (2), B (3), and C (4) were isolated from the seeds of Citrus sudachi, together with the known compounds ichangensin, obacunone, obacunoic acid and limonin, and the structures of the new compounds were elucidated based on spectroscopic and chemical evidence.     

Measurement of Masseteric Oxygenation by Near-Infrared Spectroscopy during Chewing

To non-invasively determine the condition of the masticatory muscles during chewing in real time, we used near-infrared spectroscopy and measured the masseter muscle. It increased in size, while the deoxy Hb in this muscle experienced the change in the short cycle by chewing. Periodic change of deoxy Hb was in agreement with the vertical movement of the lower jaw. It was found that the amount of increase in the deoxy Hb differs depending on the hardness of food being chewed. Moreover, by carrying out simultaneous measurement of the masseter muscles on both side of the jaw it was possible to determine the predominant muscles currently used in chewing.     

Fluorescent modification for peptide sequencing by postsource decay-matrix assisted laser desorption/ionization-mass spectrometry

The sequential analysis of a peptide of CDYEGRLI, relating to the nucleic proteins in influenza virus, was performed by the postsource decay (PSD) fragmentation method using matrix assisted laser desorption/ionization-time of flight-mass spectrometry (MALDI-TOF-MS). The sequence of the peptide was difficult to analyze by MALDI-MS since the PSD fragment ions of the peptide were almost never observed and were not amenable to complete sequence interpretation. The peptide was modified by 4(5)-(iodoacetamide) fluorescent reagent to improve the sensitivity of the MALDI-PSD fragment spectrum. In the spectrum of the fluorescent modified peptide, almost all sequential b-series fragment ions were observed clearly, which was sufficient for complete sequence interpretation. The results indicate the advantage of fluorescent modification for the total sequencing of the peptides by MALDI-MS.     

Pseudogap formation in the intermetallic compounds (Fe1-xVx)3Al

Optical conductivity data of the intermetallic compounds (Fe1-xVx)3Al ( 0相似文献   

Measurement of D(d,p) T Reaction Cross Sections in Sm Metal in Low Energy Region (10≤Ed≤20keV)

To study the screening effect of nuclear reactions in metallic environments, the thick target yields, the cross sections and the experimental S(E) factors of the D(d,p)T reaction have been measured on deuterons implanted in Sm metal at 133.2K for beam energies ranging from 10 to 20keV. The thick target yields of protons emitted in the D(d,p) T reaction are measured and compared with those data extrapolated from cross sections and stopping power data at higher energies. The screening potential in Sm metal at 133.2K is deduced tobe 520±56eV. As compared with the value achieved in the gas target, thecalculated screening potential values are much larger. This screening potential cannot be simply interpreted only by the electron screening. Energy dependences of the cross section σ(E) and the experimental S(E) factor for D(d,p)T reaction in Sm metal at 133.2K are obtained, respectively.     

ECR离子源引出束流周期性波动研究

Earlier we reported an ion current jump which was observed at a fixed negative biased disc potential in the 6.4GHz ECR ion source at VECC,Kolkata.In a recent experiment with neon ions,we measured the time spectra of the ion current and observed the presence of a burst frequency in the kilohertz range.This frequency shows a correlated jump with the ion current jump described above.Another interesting feature is that the observed burst frequency shows a good linear correlation with the extracted ion current.The higher the ion current,the higher is the burst frequency.This means that current per burst is a constant factor;when there are more number of bursts,the current also increases.     

Practical optical frequency measurement system around 1.5 μm based on an acetylene-stabilized laser-locked optical frequency comb

We have developed a practical and precise frequency measurement system at 1.5 μm telecommunication band. An electro-optic-modulator based optical frequency comb is phase-locked to a dither-free acetylene-stabilized laser to realize an optical frequency comb with frequency uncertainty of 10 kHz (5 × 10⁻¹¹) and the linewidth of 15 kHz. The present frequency comb can be also used as an optical frequency reference grid defined by ITU-T (International Telecommunication Union, Telecommunication Standardization Sector). Using the present frequency measurement system, we have demonstrated the first optical frequency measurement of ¹²C¹⁶O overtone absorption lines around 1.56 μm with the uncertainty of lower than 900 kHz.