[Occurrence Characteristics of Microplastics in Multi-environmental Media and Bellamya aeruginosa of Manao River].

Microplastic pollution poses threats to aquatic ecosystems and human health. In this study, in order to investigate the characteristics of microplastic occurrence in different environmental media, the abundance, particle size, shape, color, and composition types of microplastics in the water column, sediment, riparian zone soil, and the benthic snail Bellamya aeruginosa of the Manao River were analyzed using field sampling, microscopic observation, and Fourier infrared spectroscopy. The results showed that the average abundance of microplastics in the surface water of the Manao River was (5.9±0.26) n·L-1; the abundance of microplastics in the upper sediment (by dry weight) was (1.35±0.1) n·g-1, and that in the lower sediment (by dry weight) was (0.93±0.12) n·g-1. The abundance of microplastics in the near riparian zone soil (by dry weight) was (0.68±0.16) n·g-1, and that in the far riparian zone soil (by dry weight) was (0.69±0.14) n·g-1, and the abundance of microplastics in the B. aeruginosa was (2.06±0.25) n·g-1. The analysis results showed that the abundance of microplastics in the upper and lower sediments were positively correlated; the abundance of microplastics in B. aeruginosa was positively correlated with the abundance of microplastics in the upper and lower sediments, respectively; and the abundance of microplastics in the near and far riparian zone soils were also correlated. Most of the microplastics within each environmental medium and B. aeruginosa were <0.1 mm in size, mainly in the form of fibers and fragments, mainly blue and black in color, and mainly composed of polypropylene (PP) and polyethylene (PE). It was found that microplastics in riparian zone soils mainly originated from the fragmentation and decomposition of agricultural plastic films. The results of this study shed light on the accumulation of microplastics in macrobenthic organisms through the investigation of microplastics in multi-environmental media and in the B. aeruginosa, which helps us to understand the potential ecological risk of microplastics in a comprehensive manner.

[Assessment of Microplastic Pollution and Estimation of Annual Emission Volume in the Dongshan Canal of Yichang City].

Microplastics, as an emerging pollutant, have garnered global attention. Urban areas are key hotspots for the generation of microplastic pollution, whereas urban water bodies act as vital conduits for the dissemination of microplastics to other freshwater environments. In this study, the Dongshan Canal in the urban area of Yichang City was selected as the research subject. Through field sampling, microscopic observation, and Fourier infrared spectroscopy analysis conducted in July and October 2022, the occurrence characteristics and potential pollution sources of microplastics in the water body of the Dongshan Canal were identified and analyzed. The ecological risk and annual emission volume of microplastics in the water body were quantitatively assessed using the risk index (H), pollution load index (PLI) model, and proportional flow method. The results indicated that the average abundances of microplastics in the surface water of the Dongshan Canal were (7 295±1 051) n·m-3 (July) and (5 145±762.6) n·m-3 (October). Fibrous microplastics (27.63%-63.23%), microplastics with a size of <0.5 mm (75.68%-96.2%), and colored microplastics (22.73%-61.83%) dominated the samples, with PE (30.1%) and PET (26.33%) being the predominant materials. The assessment results from the two models classified the ecological risk index of the Dongshan Canal as class Ⅲ, whereas the overall pollution load fell into class I, with certain sampling points reaching class Ⅱ. Estimates revealed that the Dongshan Canal transports approximately 3.37 t of microplastics to the Yangtze River annually. Overall, the microplastic pollution level in the Dongshan Canal of Yichang City could be considered moderate, with potential sources of pollution including laundry wastewater, personal care products, and plastic waste.

Adsorption Kinetics of Biosurfactant Surfactin at the n-Hexadecane/Aqueous Solution Interface.

Surfactin is a typical kind of biosurfactant with a large diversity of structure, and its molecular structure is expected to play a crucial role in its adsorption dynamics. Adsorption kinetics of surfactin homologues at the n-hexadecane/aqueous solution interface is studied using a droplet-based microfluidic method. Molecular dynamics simulations are performed to illustrate the dependence of adsorption energy on the surfactin structure. Rapid reduction of dynamic interfacial tensions is obtained. The best fit to experimental results reveals that surfactin with shorter aliphatic chains, C13-surfactin and C14-surfactin, has larger rate constants of adsorption and desorption. Interfacial tensions are rapidly reduced in the case of the oil/water interface which is freshly formed, and the equilibrium adsorption is rapidly established approximately in 100-350 ms at concentrations above the critical micelle concentration. C15-surfactin that has a longer aliphatic chain adsorbs and desorbs slower, and the equilibration time of adsorption is slightly longer. Moreover, C15-surfactin has a strong tendency for adsorbing at the interface, which is in accordance with the larger adsorption energy obtained by molecular dynamics simulation, and aggregating behavior in solution. The present study provides insights on the surfactin structure and the dynamics of adsorption at the liquid/liquid interface.

Anharmonic Coupling Revealed by the Vibrational Spectra of Solvated Protonated Methanol: Fermi Resonance, Combination Bands, and Isotope Effect.

Intriguing vibrational features of solvated protonated methanol between 2400-3800 cm-1 are recorded by infrared predissociation spectroscopy. Positions of absorption bands corresponding to OH stretching modes are sensitive to changes in solvation environments, thus leading to changes in these vibrational features. Two anharmonic coupling mechanisms, Fermi resonance (FR) contributed by bending overtones and combination band (CB) associated with intermolecular stretching modes, are known to lead to band splitting of OH stretching fundamentals in solvated hydronium and ammonium. Theoretical analyses based on the ab initio anharmonic algorithm not only well reproduce the experimentally observed features but also elucidate the magnitudes of such couplings and the resulting interplay between these two mechanisms, which provide convincing assignments of the spectral patterns. Moreover, while the hydroxyl group plays the leading role in all the above-mentioned features, the role of the methyl group is also analyzed. Through the H/D isotope substitution, we identify overtones of the methyl-hydroxyl rocking modes and their participation in FR.

Vibrational Coupling in Solvated H3O+: Interplay between Fermi Resonance and Combination Band.

Complex vibrational features of solvated hydronium ion, H3O+, in 3 µm enable us to look into the vibrational coupling among O-H stretching modes and other degrees of freedom. Two anharmonic coupling schemes have often been engaged to explain observed spectra: coupling with the OH bending overtone, known as Fermi resonance (FR), has been proposed to account for the splitting of the OH stretch band at ∼3300 cm-1 in H3O+···Ar3, but an additional peak in H3O+···(N2)3 at the similar frequency region has been assigned to a combination band (CB) with the low-frequency intermolecular stretches. While even stronger vibrational coupling is expected in H3O+···(H2O)3, such pronounced peaks are absent. In the present study, vibrational spectra of H3O+···Kr3 and H3O+···(CO)3 are measured to complement the existing spectra. Using ab initio anharmonic algorithms, we are able to assign the observed complex spectral features, to resolve seemingly contradictory notions in the interpretations, and to reveal simple pictures of the interplay between FR and CB.

Vibrational spectra of small methylamine clusters accessed by an ab initio anharmonic approach.

Methylamine (MMA) is one of the simplest amines, and the vibrational spectra of its dimer have recently been obtained experimentally. The vibrational spectra of NH stretch modes were well resolved, but the complex features of the CH3 group could not be fully accounted for even with the assistance of ab initio molecular dynamics (AIMD) with various density functional methods. In this study, we carried out anharmonic vibrational calculations on MMA clusters up to tetramers using MP2/aug-cc-pVDZ to examine vibrational coupling among CH/NH and compute the vibrational spectra of these clusters between 2800 and 3500 cm-1. We found that the main origin of the complexity between 2800 and 3000 cm-1 was caused by Fermi resonance (FR) between the stretching and bending overtones of the CH3 group. This spectral feature becomes simpler in trimers and tetramers. Furthermore, Fermi resonance in the NH2 group is found to be very strong. In the MMA dimer, no noticeable FR features can be found; however, in its trimers and tetramers, the enhancement of hydrogen bond strength due to the cooperative effect will cause the N-H stretching mode to red-shift to revert the energy order of the fundamental of the N-H stretch and overtone of N-H bending between n = 3 and n = 4. Therefore, significant re-distribution of the intensities of the bands at 3200 and 3300 cm-1 should be seen.

Hydrogen bond network structures of protonated short-chain alcohol clusters.

Because of the hydrogen bond coordination properties of alcohols, their possible hydrogen bond network structures are categorized into only a few types. Therefore, gas phase clusters of alcohols can be a very simple model system to examine the properties of hydrogen bond networks, such as structural development with cluster size and temperature dependence. In this perspective, we focus on the structural study of protonated short-chain alcohol clusters, whose excess protons (charge) enable size-selective spectroscopy in combination with mass spectrometric techniques. Size-selective infrared spectroscopy and a theoretical multi-scale isomer search were applied to protonated clusters of methanol, which is a prototype of short-chain alcohols, and their hydrogen bond network development is elucidated in detail. Complete isomer population switching with increasing temperature was predicted by the quantum harmonic superposition approximation and this isomer switching was evidenced by the remarkable temperature (internal vibrational energy) dependence of the observed infrared spectra. The characteristics of the temperature dependence of protonated methanol were compared with those of water and neutral methanol. In addition, possible hydrogen bond networks of methanolated ions were discussed on the basis of the results for protonated methanol. Stepwise changes in the internal energy of clusters with inert gas tagging are demonstrated. Convergence of the hydrogen bond network to the bulk-like network in large clusters is also discussed. The hydrogen bond structures of the protonated clusters of longer normal alkyl chain alcohols (ethanol, 1-propanol, 1-butanol, and 1-pentanol) are determined by comparison of their infrared spectra with those of the protonated methanol clusters. It is demonstrated that the normal alkyl chain interferes only slightly with the most stable hydrogen bond structure, although a few exceptional cases were also found. These exception cases serve as good model systems for further theoretical and computational studies.

A novel binary flooding system of a biobased surfactant and hydrophobically associating polymer with ultralow interfacial tensions.

The alkali free surfactant-polymer flooding system with ultralow interfacial tension is a challenge in enhanced oil recovery at present. A novel alkali free binary flooding system of a biobased zwitterionic surfactant and hydrophobically associating polymer with ultralow interfacial tension at a low surfactant dosage was studied in this paper.

Hydrogen-bonded ring closing and opening of protonated methanol clusters H(+)(CH3OH)(n) (n = 4-8) with the inert gas tagging.

The preferential hydrogen bond (H-bond) structures of protonated methanol clusters, H(+)(MeOH)n, in the size range of n = 4-8, were studied by size-selective infrared (IR) spectroscopy in conjunction with density functional theory calculations. The IR spectra of bare clusters were compared with those with the inert gas tagging by Ar, Ne, and N2, and remarkable changes in the isomer distribution with the tagging were found for clusters with n≥ 5. The temperature dependence of the isomer distribution of the clusters was calculated by the quantum harmonic superposition approach. The observed spectral changes with the tagging were well interpreted by the fall of the cluster temperature with the tagging, which causes the transfer of the isomer distribution from the open and flexible H-bond network types to the closed and rigid ones. Anomalous isomer distribution with the tagging, which has been recently found for protonated water clusters, was also found for H(+)(MeOH)5. The origin of the anomaly was examined by the experiments on its carrier gas dependence.

An infrared spectroscopic and theoretical study on (CH3)3N-H(+)-(H2O)(n), n = 1-22: highly polarized hydrogen bond networks of hydrated clusters.

Infrared spectra of protonated trimethylamine (TMA)-water clusters, (CH3)3N-H(+)-(H2O)n (n = 1-22) were measured in the OH stretching vibrational region by size-selective photodissociation spectroscopy. Density functional theory calculations of stable structures were performed, and temperature dependence of the isomer populations and infrared spectra was also simulated by the harmonic superposition approximation approach to analyze hydrogen bond network structures in the clusters. It was shown that the excess proton (H(+)) in this system localizes on the TMA moiety regardless of cluster size. In the small-sized clusters, many isomers coexist and their hydrogen bond networks are highly polarized to induce the large charge-dipole interaction to stabilize the excess proton. Magic number behavior is not observed at around the magic number size (n = 21) of protonated water clusters and its implication on the hydrogen bond network structures is discussed.

Structural evolution and solvation of the OH radical in ionized water radical cations (H2O)n(+), n = 5-8.

Structural evolution of ionized water radical cations (H2O)n(+), n = 5-8, is studied by ab intio methods. A structure searching method based on the previous understanding of the hydrogen bond (H-bond) network in neutral and protonated water clusters is found to be effective, covering a wide range of structural isomers of (H2O)n(+). With these local minima, we can analyze both the size and temperature dependence of the structure of (H2O)n(+) and solvation of the OH radical. Agreement between our calculated IR spectra and experimental data in the free OH stretching region confirms that the OH radical preferred to stay on the terminal site of the H-bond network at n = 5 and n = 6. Furthermore, we found that the OH radical began to form H-bonds with water molecules as a H-bond donor at n = 7 and 8. Vibrational signatures of fully solvated OH were found to be located at 3200-3400 cm(-1) coinciding with the additional peaks found in previous experimental data obtained by Mizuse and Fujii.

Folding of the hydrogen bond network of H(+)(CH3OH)7 with rare gas tagging.

A number of isomer structures can be formed in hydrogen-bonded clusters, reflecting the essential variety of structural motifs of hydrogen bond networks. Control of isomer distribution of a cluster is important not only in practical use for isomer-specific spectroscopy but also in understanding of isomerization processes of hydrogen bond networks. Protonated methanol clusters have relatively simple networks and they are model systems suitable to investigate isomer distribution changes. In this paper, isomer distribution of H(+)(CH(3)OH)(7) is studied by size-selective infrared spectroscopy in the OH and CH stretching vibrational region and density functional theory calculations. While the clusters produced by a supersonic jet expansion combined with electron ionization were predominantly isomers having open hydrogen bond networks such as a linear chain, the Ar or Ne attachment (so-called rare gas tagging) entirely switches the isomer structures to compactly folded ones, which are composed only of closed multiple rings. The origin of the isomer switching is discussed in terms of thermal effects and specific isomer preference.

Polypyrimidine Tract Binding Protein Negatively Regulates the Expression of HBV Surface Antigen by Interacting with HBV Postranscriptional Regulatory Element / 中国生物工程杂志

In order to demonstrate PTB bind to HPRE,reverse transcription,PCR-mediated detection,were used.HepG2.2.15 cell line and HBs-HPRE transient expression cells were adopted to identify PTB function in HBV life cycle.The results showed that PTB could directly bind to HPRE RNA.Functional analysis indicated that PTB could inhibit the expression of HBs antigen and this inhibition was in a dose-dependent manner in HepG2.2.15 cells.Higher expression of HBs in cells transfected pcDNA3-HBs-HPRE comparing with pcDNA3-HBs,and this high expression could also be inhibited by PTB.The data demonstrated that PTB inhibits HBs expression by interacting with HPRE.