We study angular and frequency-angular distributions of the terahertz (THz) emission of the low-frequency region (0.3-3 THz) from a two-color femtosecond plasma spark experimentally and in ...three-dimensional numerical simulations. We investigate the dependence of the angular shapes of the THz radiation on focusing conditions and pulse durations by using two laser facilities (pulse durations 35 and 150 fs) for different focusing geometries. Our experiments and simulations show that decrease in the numerical aperture from NA ≈0.2 to NA ≈0.02 results simultaneously in (I) squeezing of the THz angular distribution and (II) formation of the bright conical emission in the THz range. The moderate focusing NA ≈0.05, which forms the relatively narrow unimodal THz angular distribution, is identified as optimal in terms of angular divergence. Numerical simulations with carrier wave resolved show that bright THz ring structures appear at the frequencies ≥2 THz for longer focuses (NA ≈0.02), while for optimal focusing conditions NA ≈0.05 the conical emission develops at THz frequencies higher than 10 THz.
We report a robust display technology for the screening of disulfide-rich peptides, based on cDNA–protein fusions, by developing a novel and versatile puromycin-linker DNA. This linker comprises four ...major portions: a ‘ligation site’ for T4 RNA ligase, a ‘biotin site’ for solid-phase handling, a ‘reverse transcription primer site’ for the efficient and rapid conversion from an unstable mRNA–protein fusion (mRNA display) to a stable mRNA/cDNA–protein fusion (cDNA display) whose cDNA is covalently linked to its encoded protein and a ‘restriction enzyme site’ for the release of a complex from the solid support. This enables not only stabilizing mRNA–protein fusions but also promoting both protein folding and disulfide shuffling reactions. We evaluated the performance of cDNA display in different model systems and demonstrated an enrichment efficiency of 20-fold per selection round. Selection of a 32-residue random library against interleukin-6 receptor generated novel peptides containing multiple disulfide bonds with a unique linkage for its function. The peptides were found to bind with the target in the low nanomolar range. These results show the suitability of our method for in vitro selections of disulfide-rich proteins and other potential applications.
We report the first experimental observation of backward terahertz emission from the two-color laser induced plasma filament in air. The ratio of measured forward-to-backward terahertz radiation is ...∼25/1. This result agrees with numerical simulations based on interferometric model assuming 0.3 mm long plasma source.
We examined the paleoceanographic origin of the deep water in the Japan Sea over the last 145kyr by using stable isotope data from foraminifera and paleontological data related to diatoms and ...planktonic foraminiferal coiling direction from core KT05-9p2 recovered from the Yamato Rise in the center of the Japan Sea. Carbon and oxygen isotope records of benthic and planktonic foraminiferal tests reveal that not only the Tsushima Current but also the Oyashio Current have been the major sources of Japan Sea water during the past 145kyr and that changes in deep water properties correspond with eustatic sea-level fluctuations. Seasonal cooling of surface water mainly derived from the Tsushima Current is known to have produced deep water during high sea-level stands. Baroclinic forcing that prevailed during surface-water freshening resulted in the inflow of the Oyashio Current through the Tsugaru Strait at the northeast end of the Japan Sea. After entering the Japan Sea, the Oyashio water sank to the bottom and contributed to deep water formation. Oxygen isotope values of benthic foraminiferal tests from the horizons corresponding to MIS 3 and 4 are similar to the calculated values for Oyashio Current water from periods during which sea level was ~80m lower than at present. The occurrence of authigenic branching pyrite from weakly disturbed layers indicates the onset of oxygen deficiency immediately below the sediment–water interface during stages of low sea-level stands, suggesting the prevalence of deep water stagnation from the weakening of overturning circulation during Japan Sea isolation. Glacio-eustatic sea-level changes have greatly influenced the oceanic regime of the Japan Sea.
► We examined the paleoceanographic origin of the Japan Sea for the last 145ka. ► The Tsushima and Oyashio currents have been the major source of the Japan Sea water. ► The glacio-eustatsy has greatly influenced the oceanic regime of the Japan Sea. ► Seasonal cooling of surface water produced deep water at high sea-level stands. ► Baroclinic forcing induced the inflow of the Oyashio Current at low sea-level stands.
The urinary concentrations of the main metabolites of 3,4-methylenedioxymethamphetamine (MDMA; Ecstasy), specifically 4-hydroxy-3-methoxymethamphetamine sulfate (HMMA-Sul) and ...4-hydroxy-3-methoxymethamphetamine glucuronide (HMMA-Glu), have been directly measured in both MDMA users and rats by an established liquid chromatography-electrospray ionization mass spectrometry (LC-ESI-MS) procedure. The concentrations of these conjugates in urine from MDMA users (n = 25) ranged from 6.5 to 202 µM (from 1.8 to 55.6 µg ml−1) for HMMA-Sul and from 1.3 to 87.0 µM (from 0.5 to 32.3 µg ml−1) for HMMA-Glu, and the ratio of HMMA-Sul to HMMA-Glu ranged from 1.6 to 9.9 (3.1 ± 1.8). These results demonstrate that the sulfation is quantitatively more significant than the glucuronidation for HMMA in humans. In rats, in contrast, almost all the conjugated HMMA (>99%) was excreted as the glucuronide. These findings indicate that hydrolysis should be carefully made in urine analysis by gas chromatography (GC) or gas chromatography-mass spectrometry (GC-MS) by using either an acid or an enzyme possessing both sulfatase and β-glucuronidase activities. It is concluded that a considerable interspecies variation exists in the conjugation of HMMA between humans and rats.
A sensitive and reliable LC-ESI–MS procedure for the simultaneous determination of MDMA and its five metabolites including 4-hydroxy-3-methoxymethamphetamine (HMMA) conjugates has been established ...following the synthesis of two HMMA conjugates, 4-hydroxy-3-methoxymethamphetamine-glucuronide (HMMA-Glu) and 4-hydroxy-3-methoxymethamphetamine-sulfate (HMMA-Sul). Pretreatment of urine samples with methanol and LC–MS employing a C
18 semi-micro column with a gradient elution program provided the successful separations and MS determinations of these analytes within 20
min. Upon applying the method to MDMA users’ urine specimens, HMMA-Glu and HMMA-Sul have been directly determined, suggesting the superiority of sulfation to glucuronidation in the HMMA phase II metabolism.
The polymeric immunoglobulin receptor (pIgR) is a type I transmembrane protein that is expressed on the surfaces of glandular and intestinal epithelial cells. The extracellular portion of the pIgR is ...composed of six different domains. Domain 6 is involved in the enzymatic cleavage and release of the pIgR into the intestinal lumen as a free secretory component (fSC). A highly conserved 9‐amino acid sequence is present in this region in various species. Although mutations in domain 6 are associated with particular diseases, such as IgA nephropathy and Epstein–Barr virus‐related nasopharyngeal cancer, and the glutamic acid residues in the conserved 9‐amino acid sequence are expected to be indispensable for the secretion of fSC, the importance of these residues has not been examined. In the present study, we attempted to examine the role of these residues in the enzymatic cleavage of the pIgR. The enzymatic cleavage of the pIgR was not affected by the presence of an alanine to valine substitution at position 580 or glutamine to alanine substitutions at positions 606 and/or 607, or the deletion of the whole 9‐amino acid conserved sequence. Intriguingly, the 10 amino acid sequences flanking the N‐ and C‐terminal ends of the conserved 9‐amino acid sequence had opposite effects on pIgR cleavage. Namely, the N‐terminal and C‐terminal sequences enhanced and reduced pIgR cleavage efficiency, respectively. These results indicated that the pIgR can be divided into several functionally distinct regions.
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