Genomic Structure of the Amphioxus Calcium Vector Protein

Calcium vector protein (CaVP) is an EF-hand Ca2+-binding protein, which is unique to the protochordate, amphioxus. CaVP is supposed to act as a Ca2+ signal transductor, but its exact function remains unknown. Not only its function but also its exact evolutionary relationship to other Ca2+-binding proteins is unclear. To investigate the evolution of CaVP, we have determined the complete sequences of CaVP cDNAs from two amphioxus species, Branchiostoma lanceolatum and B. floridae, whose open reading frame cDNA and amino acid sequences show 96.5 and 98.2% identity, respectively. We have also elucidated the structure of the gene of B. floridae Ca VP, which is made up of seven exons and six introns. The positions of four of the six introns (introns 1, 2, 3, and 5) are identical with those of calmodulin, troponin C, and the Spec protein of the sea urchin. These latter proteins belong to the so-called troponin C superfamily (TnC superfamily) and thus CaVP likely also belongs to this family. Intron 6 is positioned in the 3‘ noncoding region and is unique to CaVP, so it may represent a landmark of the CaVP lineage only. The position of intron 4 is not conserved in the genes of the TnC superfamily or CaVP, and seems to result from either intron sliding or the addition of an intron (randomly inserted into or close to domain HE) to the genes of the TnC superfamily during their evolutio

Diversity of the Troponin C Genes during Chordate Evolution

To elucidate the diversity of troponin C (TnC) during chordate evolution, we determined the organization of TnCs from the amphioxus, the lamprey, and the frog. Like the ascidian, the amphioxus possesses a single gene of TnC, and the fundamental gene structure is identical with the ascidian TnC. However, because alternative splicing does not occur in amphioxus, the potential for generation of TnC isoforms through this event arises only in the ascidian lineage. From the frog Xenopus laevis, two distinct cDNAs encoding fTnC isoforms and a single s/cTnC cDNA were determined. The duplication of the fTnC gene may be a character of only Xenopus or closely related species. The lamprey possesses two cDNAs each encoding fTnC and s/cTnC. The lamprey is the earliest diverged species among vertebrates, and thus it is supposed that the presence of both fTnC and s/cTnC is universal among vertebrate species, and that the gene duplication might have occurred at a vertebrate ancestor after the protochordate/vertebrate divergence. The position of the 4th intron is 3.24/0 in protochordate TnC genes, but at 3.11/2 in vertebrate fTnCs and s/cTnCs. It is suggested that the 4th intron sliding might have occurred prior to the gene duplicatio

Inhibition of the photoinduced structural phase transition in the excitonic insulator Ta2_2NiSe5_5

Femtosecond time-resolved mid-infrared reflectivity is used to investigate the electron and phonon dynamics occurring at the direct band gap of the excitonic insulator Ta$_2$NiSe$_5$ below the critical temperature of its structural phase transition. We find that the phonon dynamics show a strong coupling to the excitation of free carriers at the \Gamma\ point of the Brillouin zone. The optical response saturates at a critical excitation fluence $F_C = 0.30~\pm~0.08$~mJ/cm$^2$ due to optical absorption saturation. This limits the optical excitation density in Ta$_2$NiSe$_5$ so that the system cannot be pumped sufficiently strongly to undergo the structural change to the high-temperature phase. We thereby demonstrate that Ta$_2$NiSe$_5$ exhibits a blocking mechanism when pumped in the near-infrared regime, preventing a nonthermal structural phase transition

The role of trefoil factor family in apparently healthy subjects administrated gastroprotective agents for the primary prevention of gastrointestinal injuries from low-dose acetylsalicylic acid: a preliminary study

It is well-known that acetylsalicylic acid induces gastrointestinal complication. Recently, trefoil factor family has been reported as a mucosal protective factor. We focused on trefoil factor family as one of defensive system for gastrointestinal injuries. The aim of this trial was to evaluate trefoil factor family levels in the serum of healthy subjects with low-dose acetylsalicylic acid. Low-dose acetylsalicylic acid with placebo or proton pump inhibitor or rebamipide were administered in 30 healthy subjects. Transnasal endoscopy was performed at 0, 24 h, 3 and 7 day. Changing of trefoil factor family (1,2,3) and numbers of gastric injuries were evaluated. The numbers of gastric injuries were significantly increased in the placebo group at 3 and 7 days. Injuries in the proton pump inhibitor group were not induced, in the rebamipide group were slightly induced. Trefoil factor family level in the placebo group were decreased in 3 and 7 days compared with prior to starting the trial. Trefoil factor family may have an important association with acetylsalicylic acid-induced gastrointestinal damage. Proton pump inhibitor and rebamipide prevented low-dose acetylsalicylic acid-induced gastrointestinal complications compared with the placebo group

Ultrafast Electronic Band Gap Control in an Excitonic Insulator

We report on the nonequilibrium dynamics of the electronic structure of the layered semiconductor Ta$_2$NiSe$_5$ investigated by time- and angle-resolved photoelectron spectroscopy. We show that below the critical excitation density of $F_{C} = 0.2$ mJ cm$^{-2}$, the band gap $narrows$ transiently, while it is $enhanced$ above $F_{C}$. Hartree-Fock calculations reveal that this effect can be explained by the presence of the low-temperature excitonic insulator phase of Ta$_2$NiSe$_5$, whose order parameter is connected to the gap size. This work demonstrates the ability to manipulate the band gap of Ta$_2$NiSe$_5$ with light on the femtosecond time scale