Is there a prechordal region and an acroterminal domain in amphioxus?

This essay re-examines the singular case of the supposedly unique rostrally elongated notochord described classically in amphioxus. We start from our previous observations in hpf 21 larvae [Albuixech-Crespo et al., 2017] indicating that the brain vesicle has rostrally a rather standard hypothalamic molecular configuration. This correlates with the notochord across a possible rostromedian acroterminal hypothalamic domain . The notochord shows some molecular differences that specifically characterize its pre-acroterminal extension beyond its normal rostral end under the mamillary region. We explored an alternative interpretation that the putative extension of this notochord actually represents a variant form of the prechordal plate in amphioxus, some of whose cells would adopt the notochordal typology, but would lack notochordal patterning properties, and might have some (but not all) prechordal ones instead. We survey in detail the classic and recent literature on gastrulation, prechordal plate and notochord formation in amphioxus, compared the observed patterns with those of some other vertebrates of interest, and re-examine the literature on differential gene expression patterns in this rostralmost area of the head. We noted that previous literature failed at identifying the amphioxus prechordal primordia at appropriate stages. Under this interpretation, a consistent picture can be drawn for cephalochordates, tunicates, and vertebrates. Moreover, there is little evidence for an intrinsic capacity of the early notochord to grow rostralwards (it normally elongates caudalwards). Altogether, we conclude that the hypothesis of a prechordal nature of the elongated amphioxus notochord is consistent with the evidence presented.

Species-Specific Differences in Aryl Hydrocarbon Receptor Responses: How and Why?

The aryl hydrocarbon receptor (AhR) is a transcription factor that regulates a wide range of biological and toxicological effects by binding to specific ligands. AhR ligands exist in various internal and external ecological systems, such as in a wide variety of hydrophobic environmental contaminants and naturally occurring chemicals. Most of these ligands have shown differential responses among different species. Understanding the differences and their mechanisms helps in designing better experimental animal models, improves our understanding of the environmental toxicants related to AhR, and helps to screen and develop new drugs. This review systematically discusses the species differences in AhR activation effects and their modes of action. We focus on the species differences following AhR activation from two aspects: (1) the molecular configuration and activation of AhR and (2) the contrast of cis-acting elements corresponding to AhR. The variations in the responses seen in humans and other species following the activation of the AhR signaling pathway can be attributed to both factors.

Research on the Influence of Sodium Ion on Mechanism of Polymer Solution Viscosity Loss

The researches on the influence of sodium ion on mechanism of polymer solution viscosity loss were conducted. Scanning electron microscopy was used to analyze the polymer microstructure. Molecular dynamics simulation was employed to reveal the influence of sodium ion on the polymer molecular configuration. The results shown: the polymer viscosity loss was more than 70% when the concentration of sodium ion was above 4000 mg/L. The results of microstructure and molecular conformation analysis indicated that the main reason of viscosity loss was the electrostatic attraction between sodium ion and negatively charged groups of polymer molecule chains, which cause compression of polymer molecular chain. The coil and shrinkage of polymer molecular chain led to the breakage of the spatial network structure of macromolecules.

Thermal behavior and thermodynamic parameters of some complexes of biologically active nucleic acid constituents

The thermal behavior of some complexes derived from biologically nucleic acid constituents has been studied applying differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) techniques. Thermodynamic parameters, decompositions and thermal stabilities are calculated and explained. All the complexes gave exothermic peaks with -ve signs for change of entropy values, ΔS which indicate that the activated transition states are more ordered, i.e. in a less random molecular configuration than the reacting complexes. TGA gives the mechanism of decomposition.

Software Implementation and Design of Information Encryption Algorithm Based on DNA Nano Self-Assembled Sensor Array

In the field of information security, DNA cryptography based on DNA molecular configuration and special recognition mechanism between molecules has developed rapidly. DNA molecules have great development potential in the field of information security technology such as information encryption, hiding and authentication, which provides a new way for the development of modern cryptography. The nodes of traditional sensor networks are mostly distributed in the form of a net with strong openness. In the process of node data transmission, the information is likely to be stolen, tampered with, and destroyed at any time. In this paper, an information encryption method based on DNA nano self-assembled sensor technology is proposed, and the encryption software based on DNA nano self-assembled sensor array is designed. The information encryption algorithm is designed, tested, simulated and analysed, and compared with other designs. The simulation results show that the encryption algorithm system based on DNA nano self-assembled sensor array has good function and excellent performance, can fully meet the requirements of network real-time encryption, has good feasibility and security, and reveals the great application potential of DNA molecules in the field of information security.

Effect of Material Properties on the Foaming Behaviors of PP-Based Wood Polymer Composites Prepared with the Application of Spherical Cavity Mixer

For the low weight and high strength, the microcellular extrusion foaming technology was applied in the preparation of polypropylene (PP)-based wood polymer composites, and the spherical cavity mixer was used to construct an experimental platform for the uniform dispersion of wood flour (WF). The effects of PP molecular configuration on the composite properties and cell morphology of samples were also investigated. The experimental results indicated that the application of a spherical cavity mixer with a cavity radius of 5 mm could effectively improve the mixing quality and avoid the agglomeration of WF. In addition, compared with the branched molecule, the linear molecule not only increased the melting temperature by about 10 °C, but also endowed composites with a higher complex viscosity at a shear rate lower than 100 s−1, which contributed to the cell morphology of more microporous samples.

Understanding adsorption geometry of organometallic molecules on graphite

To comprehensively investigate the adsorption geometries of organometallic molecules on graphene, Cp*Ru+ fragments as an organometallic molecule is bound on highly oriented pyrolytic graphite and imaged at atomic resolution using scanning tunneling microscopy (STM) (Cp* = pentamethylcyclopentadienyl). Atomic resolution imaging through STM shows that the Cp*Ru+ fragments are localized above the hollow position of the hexagonal structure, and that the first graphene layer adsorbed with the fragments on the graphite redeveloped morphologically to minimize its geometric energy. For a better understanding of the adsorption site and molecular geometry, experimental results are compared with computed calculations for the graphene surface with Cp*Ru+ fragments. These calculations show the adsorption geometries of the fragment on the graphene surface and the relationship between the geometric energy and molecular configuration. Our results provide the chemical anchoring geometry of molecules on the graphene surface, thereby imparting the theoretical background necessary for controlling the various properties of graphene in the future.