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The proton transfer processes of 10-hydroxybenzo[h]quinoline (HBQ) and its cyano derivatives (4CN-HBQ, 7CN-HBQ and 7,9CN-HBQ) were studied by density functional theory (DFT) and time-dependent density functional theory (TD-DFT) in ethyl acetate. The optimized geometric structures and infrared spectra show that the intramolecular hydrogen bond of enol form structure is weakened when the cyano group substitutes on the pyridine ring and that is strengthened when the cyano group substitutes on the phenol ring in the S0 state. Electron spectra show that the substitution of cyano group also has a significant effect on electron spectra. The reason for the change in the electron spectra can be obtained from the analysis of frontier molecular orbitals (MOs). The calculated potential barriers for proton transfer of these four molecules are 6.83, 7.83, 4.87 and 2.79 kcal/mol respectively in the S0 state, illustrating that the presence, position and number of cyano groups affect the proton transfer processes to some extent. After vertical excitation to the S1 state, the proton transfer processes of these four molecules become barrierless because of the promotion of charge transfer. Through the analysis of Mulliken charge, it can be found that the cyano group, an electron-withdrawing group, can change the strength of hydrogen bond by withdrawing the electronic charge from hydroxyl oxygen or neighboring nitrogen atom of its ring and thus affects the barrier in the S0 state.

Antimicrobial peptides (AMPs) play an important role in the host defense system of shrimps. In this study, an Arasin-like peptide, named as LvArasin-like, was identified from the hemocytes of the pacific white shrimp, Litopenaeus vannamei. The complete open reading frame (ORF) of LvArasin-like was 213 bp, encoding 70 amino acid residues with a predicted molecular mass of 5.68 kDa and a theoretical isoelectric point (pI) of 6.73. The predicted peptide consisted of a signal peptide, an N-terminal Pro/Arg-rich domain, and a C-terminal cysteine-rich domain. LvArasin-like expression was most abundant in the gills and was up-regulated in hemocytes after LPS or Poly I:C injection as well as challenges by Vibrio parahaemolyticus or Staphylococcus aureus infection. In the heterologous expression system, LvArasin-like protein (rLvArasin-like) was recombinantly expressed in the forms of a dimer or both a monomer and dimer. The rLvArasin-like could directly bind to gram-positive and gram-negative bacteria and exhibited broad-spectrum antimicrobial activity towards them, with 50 % of minimal inhibitory concentrations (MIC50) of 6.25–50 μM. Moreover, dsRNA-mediated knockdown of LvArasin-like enhanced the susceptibility of shrimp to V. parahaemolyticus. In addition, the transcriptional level of LvArasin-like was downregulated when silencing of the transcription factors LvDorsal and LvRelish using RNAi in vivo. All of these results suggest that LvArasin-like is involved in host defense against bacterial infection. Therefore, it is a potential therapeutic agent for disease control in shrimp aquaculture.

Recently, Krishnamoorthy and coworkers reported a new type of proton transfer, which was labeled as ‘proton transfer triggered proton transfer’, in 3,5-bis(2-hydroxypheny)-1H-1,2,4-triazole (bis-HPTA). In this work, the excited-state double proton transfer (ESDPT) mechanism and multiple fluorescent characteristics of bis-HPTA were investigated. Upon photo-excitation, the intramolecular hydrogen bonding strength changed and the electron density of bis-HPTA redistributed. These changes will affect the proton transfer process. In S0 state, the proton transfer processes of bis-HPTA were prohibited on the stepwise and concerted pathways. After vertical excitation to the S1 state, the ESIPT-II process was more likely to occur than the ESIPT-I process, which was contrary to the conclusion that the ESIPT-II process is blocked and the ESIPT-II process takes place after the ESIPT-I process proposed by Krishnamoorthy and coworkers. When the K2 tautomer was formed through the ESIPT-II process, the second proton transfer process on the stepwise pathway was prohibited. On another stepwise pathway, after the ESIPT-I process (form the K1 tautomer), the second proton transfer process should overcome a higher potential barrier than the ESIPT-I process to form ESDPT tautomer. On the concerted pathway, the bis-HPTA can synchronous transfer double protons to form the ESDPT tautomer. The ESDPT tautomer was unstable and immediately converted to the K2 tautomer via a barrierless reverse proton transfer process. Thus, the fluorescent maximum at 465 nm from the ESDPT tautomer reported by Krishnamoorthy and coworkers was ascribed to the K2 tautomer. Most of the fluorophores show dual fluorescent properties, while the bis-HPTA undergoing ESDPT process exhibited three well-separated fluorescent peaks, corresponding to its normal form (438 nm), K1 tautomer (462 nm) and K2 tautomer (450 nm), respectively.

Simple sequence repeats (SSRs) of short nucleotide motifs occur very frequently in the 5′ untranslated coding region (5′-UTR) of genes and have been implicated in the regulation of gene expression. In this study, we identified an SSR with a variable number of CT repeats in the 5′-UTR of the Litopenaeus vannamei IRF (LvIRF) gene that has been shown to mediate antiviral responses by inducing the expression of Vago, a functional homolog of mammalian IFN. We then explored the effects of varying the number of (CT)n repeats on the expression of LvIRF using both dual-luciferase reporter assays and Western blots. Our results demonstrate that the length of the (CT)n-SSR in this gene can influence the expressional level of LvIRF, in that a shorter (CT)n repeat had a stronger ability to induce the expression of LvIRF. Moreover, we found that the (CT)n repeat in LvIRF was associated with viral resistance in shrimp. Individual shrimps with shorter (CT)n repeats in the 5′-UTR of LvIRF exhibited high tolerance to white spot syndrome virus (WSSV), and this trait was inherited in offspring. Taken together, these results indicated that this (CT)n-SSR could be used as a molecular marker for shrimp breeding for WSSV resistance.

The control of internal molecular motions by outside stimuli is a decisive task in the construction of functional molecules and molecular machines. Light-induced intramolecular rotations of photoswitches have attracted increasing research interests because of the high stability and high reversibility of photoswitches. Recently, Henry et al. reported an unprecedented two-dimensional controlled photoswitch, the hemithioindigo (HTI) derivative Z1, whose single bond rotation in dimethyl sulphoxide (DMSO) solvent and double bond rotation in cyclohexane solvent can be induced by visible light (J. Am. Chem. Soc. 2016, 138, 12,219). Here we investigate the intramolecular rotations of the HTI and Z1 in different polar solvents by time-dependent density functional theory (TDDFT) and Nonadiabatic dynamic simulations. Due to the steric hindrance between methyl and thioindigo fragment, the rotations of Z1 in the excited state are obstructed. Interestingly, the HTI exhibits two distinct rotation paths in DMSO and cyclohexane solvents at about 50 fs. The intermolecular hydrogen bonds between HTI and DMSO play an important role in the rotation of HTI in DMSO solvent. Therefore, the HTI is a more promising two-dimensional photoswitch compared with the Z1. Our finding is thus of fundamental importance to understand the mechanisms of this class of photoswitches and design complex molecular behavior.

The intramolecular proton transfer reaction of the 2-amino-3-(2′-benzoxazolyl)-quinoline (ABO) and 2-amino-3-(2′-benzothiazolyl)-quinoline (ABT) molecules in both S0 and S1 states at B3LYP/6–311 ++G(d,p) level in ethanol solvent have been studied to reveal the deactivation mechanism of the tautomers of the two molecules from the S1 state to the S0 state. The results show that the tautomers of ABO and ABT molecules may return to the S0 state by emitting fluorescence. In addition, the bond lengths, angles and infrared spectra are analyzed to confirm the hydrogen bonds strengthened upon photoexcitation, which can facilitate the proton transfer process. The frontier molecular orbitals (MOs) and natural bond orbital (NBO) are also calculated to indicate the intramolecular charge transfer which can be used to explore the tendency of ESIPT reaction. The potential energy surfaces of the ABO and ABT molecules in the S0 and S1 states have been constructed. According to the energy potential barrier of 9.12 kcal/mol for ABO molecule and 5.96 kcal/mol for ABT molecule, it can be indicated that the proton transfer may occur in the S1 state.

The non-fused five-membered ring structure of 2-(1H-pyrrol-2-yl)pyridine (5-HB) is more flexible than the fused six-membered ring structure of 10,11,12,13-tetrahydro-9H-quinolino[8,7-a]carbazole (6-HB) to form the intramolecular hydrogen bond between pyrrole and pyridine, while the six-membered ring structure possesses more favorable distance and orientation between pyrrole and pyridine. In the present work, we carried out the electronic structure calculations and nonadiabatic dynamics simulations to gain insight into the effect of different structure feature on the excited-state intramolecular proton transfer (ESIPT) processes of 5-HB and 6-HB. The geometric parameters, IR vibrational spectra, bond critical point (BCP) parameters and reduced density gradient (RDG) show that the intramolecular hydrogen bond of 6-HB is much stronger than that of 5-HB. The 6-HB has a lower kinetic stability and a higher chemical activity than 5-HB through the analysis of the energy gap between the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO). The pyridine N1 atom of 6-HB shows much stronger ability than that of 5-HB to attract the hydrogen proton based on the natural population analysis (NPA). The analysis of the potential energy curves and time evolution of selected bond distances indicate that the ESIPT process of fused six-membered ring structure is easier and faster than the non-fused five-membered ring structure. Our findings might be useful for the design of relevant ESIPT systems.

Penaeidins are members of an antimicrobial peptide (AMP) family that have broad anti-microbial activities only found in penaeid shrimps. The LvBigPEN, a member of penaeidins from shrimp Litopenaeus vannamei, has showed antiviral activity against white spot syndrome virus (WSSV) in our previous report. However, whether LvBigPEN possesses potential anti-bacterial activities is still unknown. Herein, we found that the LvBigPEN played an important role in restricting the infection of Vibrio parahaemolyticus, a natural and Gram-negative bacteria pathogen in shrimp. The transcription of LvBigPEN was strongly induced after V. parahaemolyticus challenge. RNA interference (RNAi) mediated knockdown of LvBigPEN showed that LvBigPEN had a potential antibacterial function against V. parahaemolyticus. Microorganism binding assays indicated that rLvBigPEN could bind to both Gram-negative bacteria and Gram-positive bacteria. Transmission electron microscopy (TEM) analysis showed its ability to destroy bacterial cells in vitro. Besides, in a gel retardation assay, rLvBigPEN could bind to plasmid DNA and bacteria (V. parahaemolyticus) genomic DNA in a concentration-dependent manner. Moreover, the AP-1 pathway could participate in the transcription of LvBigPEN by the dual luciferase reporter assays. Taken together, these results suggested that LvBigPEN possessed the antibacterial activity against V. parahaemolyticus and may be alternative agents for the prevention and treatment of diseases caused by V. parahaemolyticus.

2,5-bis(benzoxazol-2-yl)thiophene-3,4-diol (BBT) is a newly synthesized water-soluble fluorophore dye with two intramolecular hydrogen bonds. It was demonstrated that BBT exhibits the excited-state intramolecular single and double proton transfer emissions in recent experiment. In order to explain the phenomenon, the density functional theory (DFT) and time-dependent density functional theory (TD-DFT) are used to study the ground states and excited states of BBT and its tautomers. The theoretical results confirm that the hydrogen bonds are strengthened upon photoexcitation. To further reveal the proton transfer mechanism, potential energy surfaces of the S0 and S1 states have been constructed. According to the energy potential barrier of 13.69 kcal/mol, it was indicated that the double proton transfer may occur in stepwise rather than simultaneously in the S1 state unless the excited molecule can overcome the barrier.

Researchers have proposed different effective mechanisms of hydrogen bonding (HB) on the fluorescence of 6-propionyl-2-dimethylaminonaphthalene (PRODAN) and its derivatives. Herein, excited state transition and dynamics analysis confirm that the fluorescence of PD (a derivative of PRODAN with ethyl replaced by 3-hydroxy-2,2-dimethylpropan) emits from the planar intramolecular charge transfer (PICT) state rather than twist ICT (TICT) state, because the fluorescence emission and surface hopping from the TICT state to the twist ground (T-S0) state is energy forbidden. Nevertheless, the strengthening of intramolecular-HB (intra-HB) and intermolecular-HB (inter-HB) of PD-(methanol)2 smooth the pathway of surface hopping from TICT to T-S0 state and the external conversion going to planar ground state by decreasing the energy difference of the two states. This smoothing changes the fluorescence state of PD-(methanol)2 to the TICT state in which fluorescence emission does not occur but surface hopping, leading to the partial fluorescence quenching of PD in methanol solvent. This conclusion is different from previous related reports. Moreover, the inter-HB strengthening of PD-methanol in PICT state induces the cleavage of intra-HB and a fluorescence red-shift of 54 nm compared to PD. This red-shift increases to 66 nm for PD-(methanol)2 for the strengthening of the one intra-HB and two inter-HBs. The dipole moments of PD-methanol and PD-(methanol)2 respectively increase about 10.3D and 8.1D in PICT state compared to PD. The synergistic effect of intra-HB and inter-HB induces partial quenching of PD in methanol solvent by turning on the TICT state and fluorescence red-shift. This work gives a reasonable description on the fluorescence red-shift and partial quenching of PD in methanol solvent, which will bring insight into the study of spectroscopic properties of molecules owning better spectral characteristics.

The concentration and distribution of organic matter, phosphate nodules, and framboidal pyrite preserved in shales are controlled by organic matter decomposition and the cycles of phosphorus, sulfur, and iron, which, in turn, are controlled by bottom-water redox conditions. The organic-rich shale in the 7th member of the Upper Triassic Yanchang Formation (Ch7) contains high organic carbon concentrations and abundant phosphate nodules and pyrite framboids, providing an opportunity to better understand the redox conditions at the time of deposition. Framboidal pyrite in the Ch7 organic-rich shales are composed of octahedral, pyritohedral, and spherulitic microcrystals with uniform crystal size. SEM photographs and statistical data suggest that pyrite framboids have large mean diameters (10.0 to 18.1 μm) and standard deviations (2.8 to 5.9 μm). This may indicate that the organic-rich shale was deposited under oxic-suboxic bottom-water conditions. The Corg:P ratios of the organic-rich shale exhibit considerable variation, ranging from 7.2 to 216, but the majority of them (83.2%) belong to the lower-intermediate range (

The behavior of three-centered hydrogen bond (THB) in excited state is unveiled firstly. The notion proposed in experiment that the THB configuration can be stable in solution has been verified. And one more stable configuration has been found which has two intramolecular hydrogen bonds compared with THB configuration. The analysis of optimization geometrical configurations shows that the THB weakens upon photoexcitation and is apparent weaker than the two-centered hydrogen bond. The reduced electron density gradient (RDG) maps indicate that the weakening of THB compared with two-centered hydrogen bond is due to the steric repulsion of hydrogen bond donors and acceptors. In addition, fluoresce spectra indicate that the 3-position substituent of coumarin has a large blue-shift on maximum fluorescence wavelength compared with the 7-aminocoumarin C500.

The excited-state double proton transfer (ESDPT) mechanism in a model DNA base pair, 7-azaindole (7AI) dimer, has been debated over the years. Recently, Otero and coworkers concluded that the stepwise mechanism is not possible and the concerted mechanism dominates the dynamics (Chem. Sci., 2015, 6, 5762). In this work, the potential energy surfaces of the 7AI dimer in the ground state (S0) and the lowest energy excited singlet state (S1) were constructed. After vertical excitation to the S1 state, the single proton transfer can occur. The second proton transfer process in the stepwise mechanism is blocked by a high potential barrier (36.4 kcal mol−1), which is consistent with the result proposed by Otero and coworkers. However, the single proton transfer process is compatible with the concerted mechanism and we show that the single proton transfer process rather than the concerted mechanism dominates the dynamics. The concerted process is unfavorable in the S1 state compared with the barrierless single proton transfer process. In addition, the proton transfer process in the S0 state is revealed. The single proton transfer tautomer in the S1 state returns to the S0 state and transfers the second proton via a barrierless process. Finally, the double proton transfer tautomer in the S0 state can recover to the normal dimer through the reverse proton transfer reaction.

Jimusar sag, which lies in the Junggar Basin, is an important tight oil study area in China. However, the properties and origin of the crude oil and the geochemical characteristics of the tight oil from the Lucaogou Formation have not yet been studied. In the present study, 23 crude oil samples from the Lucaogou Formation were collected for analysis, including physical properties (density and viscosity), bulk composition, saturated hydrocarbon gas chromatography–mass spectrometry, and calculation of various biomarker parameters. Source rock evaluation and porosity permeability analysis were applied to the mudstones and siltstones. To analyze the hydrocarbon generation history of the Lucaogou source rocks, one-dimensional basin modeling was performed. The oil-filling history was also investigated by means of basin modeling and microthermometry. Biomarkers of suitable source rocks (total organic carbon content is >1%, summation of the free and volatile hydrocarbon and remaining hydrocarbon generative potential is >6 mg HC/g rock, and vitrinite reflectance is between 0.7% and 1%) were analyzed for oil–source correlation. The results indicate that low-maturity to mature crude oils originated from the source rocks containing terrigenous organic matter, which were deposited in a saline lake. The source rocks are of mainly type II kerogen. Oil in the lower section of the Lucaogou Formation is relatively dense and viscous and has elevated nonhydrocarbon content. In addition, a higher proportion of bacteria and algae is shown to have contributed to the formation of crude oil in the lower section when compared with the upper section of the Lucaogou Formation. Oil–source correlations demonstrate that not all mudstones within the Lucaogou Formation contribute to oil accumulation. Thin section observation indicates organic macerals surround the grains of some siltstones within the porous and permeable subsections, which proves the siltstones contribute to hydrocarbon generation. Crude oils from the upper and lower sections mainly originate from thin-bedded mudstones interbedded and siltstones within the porous and permeable subsections. The mudstones over or beneath the porous and permeable subsections consist of seals and prevent the vertical movement of oil by capillary forces. Despite being thicker, mudstones between the two porous and permeable subsections make no obvious contribution to the oil accumulation because of their low permeability and distance from the porous and permeable subsections, which is consistent with the principle of near-source charging for tight oil accumulations. Lucaogou oil has been charged twice, once from 235 to 210 Ma and again from 180 to 150 Ma, coinciding with oil generation time.

The fast and accurate detection of amyloid fibrils, which are associated with many neurodegenerative diseases, is important for their early diagnosis. {[50-(p-Hydroxyphenyl)-2,20-bithienyl-5-yl]-methylidene}-propanedinitrile (NIAD-4) is a new promising fluorescent marker for amyloid fibrils, and the photophysical behaviour of NIAD-4 is controversial. Nonadiabatic dynamic simulations, density functional theory (DFT) and time-dependent density functional theory (TDDFT) calculations were performed to determine the influence of the environment on NIAD-4 and the photophysical behaviour of NIAD-4. The results indicate that NIAD-4 is in the NIAD-4·3H2O compound form in the ground state in water. The torsion process of NIAD-4 proposed by Hu et al. (Phys. Chem. Chem. Phys. 2016, 18, 28) does not occur in the excited state. In addition, the fluorescence behaviour of NIAD-4 is sensitive to a hydrogen bonding environment, the maximum fluorescence wavelengths of NIAD-4 show considerable red-shifts, and the fluorescence intensity of NIAD-4 increases significantly in a hydrogen bonding environment. Intermolecular hydrogen bonds are vital for the phenomenon observed in the experiment because the fluorescence intensity of NIAD-4 becomes unusually high with increasing solvent polarities. Therefore, the influence of the intermolecular hydrogen bond should be carefully taken into consideration when NIAD-4 is used to probe the amyloid fibrils in hydrogen-bonding surroundings, especially in complex bioenvironments.

The excited-state intramolecular proton transfer (ESIPT) reactions of 2-(2′-hydroxyphenyl)benzimidazole (HBI) derivatives were investigated using time-dependent density functional theory (TD-DFT) method at B3LYP/TZVP theoretical level. The geometric parameters, infrared (IR) vibrational spectra, frontier molecular orbitals (MOs), Mulliken charge distribution analysis, natural bond orbital (NBO) analysis and potential energy curves were calculated to provide the direct information about the effect of electron acceptor and donor groups on the ESIPT reactions. The intramolecular hydrogen bonds are significantly strengthened and the electronic density is redistributed after a vertical excitation to S 1 state. The proton transfer (PT) reactions are unlikely occur in S0 state through the analysis of potential energy curves and the Hartree-Fock energy of the stable structures. The presence of the electron acceptor NO 2 group can facilitate the ESIPT reaction, while the presence of electron donor NH 2 group can hinder the ESIPT reaction. In general, the electron acceptor NO 2 group and electron donor NH 2 group can influence the ESIPT reactions in a completely different way.

The outbreak of diseases ordinarily results from the disruption of the balance and harmony between hosts and pathogens. Devoid of adaptive immunity, shrimp rely largely on the innate immune system to protect themselves from pathogenic infection. Two nuclear factor-κB (NF-κB) pathways, the Toll and immune deficiency (IMD) pathways, are generally regarded as the major regulators of the immune response in shrimp, which have been extensively studied over the years. Bacterial infection can be recognized by Toll and IMD pathways, which activate two NF-κB transcription factors, Dorsal and Relish, respectively, to eventually lead to boosting the expression of various antimicrobial peptides (AMPs). In response to white-spot-syndrome-virus (WSSV) infection, these two pathways appear to be subverted and hijacked to favor viral survival. In this review, the recent progress in elucidating microbial recognition, signal transduction, and effector regulation within both shrimp Toll and IMD pathways will be discussed. We will also highlight and discuss the similarities and differences between shrimps and their Drosophila or mammalian counterparts. Understanding the interplay between pathogens and shrimp NF-κB pathways may provide new opportunities for disease-prevention strategies in the future.

The fluorescence properties of 4'-methoxy-3-hydroxyflavone (M3HF) dye in different solvents were investigated through experimental (Phys. Chem. Chem. Phys., 2018, 20, 7885) and theoretical (Org. Chem. Front., 2019, 6, 218) methods. However, the intermolecular hydrogen bonds between M3HF and solvents were ignored. In this work, we investigated the effect of methanol (MeOH) and N,N-dimethylformamide (DMF) solvents on the excited-state intramolecular proton transfer (ESIPT) of M3HF fluorescent dye. In excited state (S1), the intramolecular hydrogen bonds are significantly strengthened, which can facilitate the ESIPT processes. The calculated absorption and fluorescence spectra agree well with the experimental date. The fluorescence spectra of M3HF and ESIPT tautomers (T⁎) were found to be sensitive to the solvent polarity. Upon photo-excitation, the electron density of the M3HF molecular is redistributed, which can provide driving force for the ESIPT. The polar solvents MeOH (hydrogen bond donor) and DMF (hydrogen bond acceptor) can form different types of intermolecular hydrogen bonds with M3HF. The two different bonding modes of intermolecular hydrogen bonds are expected to weaken the intramolecular hydrogen bond of M3HF to varying degrees. The analysis of the potential energy curves indicate that the ESIPT processes of M3HF can be hindered by the intermolecular hydrogen bonds. The intermolecular hydrogen bond of M3HF-DMF complex is weaker than that of M3HF-MeOH complex, while the potential barrier of the ESIPT process in DMF solvent is higher than that of in the MeOH solvent. This is principally because, in DMF solvent, the hydroxyl group H1 atom of M3HF can be captured by the O3 atom of DMF and form O3H1 bond with O3 atom in the intermediate process of ESIPT. There appears an energy barrier hopping point on the potential energy curve of M3HF in DMF solvent but does not appear in MeOH solvent.

The time-dependent density functional theory (TDDFT) is used to investigate the effects of solvent polarity and hydrogen bond on coumarin 500 (C500). Both the absorption maximum and the hydrogen bond strength of C500 hydrogen bonded complex are confirmed to have a linear relationship with the solvent polarity function Δf. The type B (at carbonyl group position) complex whose absorption spectrum is extremely agreement with the experimental results is demonstrated to be preponderant among all the hydrogen bonded complexes. The investigation of C500-phenol complex (type B) shows that the strengthening of hydrogen bond in the S1 state induces the fluorescence intensity of C500 weakened. The solvent polarity is the key influencing factor on intermolecular hydrogen bond by comprising the influence of solvent polarity and substituent on C500.

In the evolutionarily conserved canonical NF-κB pathway, degradation of the NF-κB inhibitor IκB in the cytoplasmic NF-κB/IκB complex allows the liberated NF-κB to translocate into the nucleus to activate various target genes. The regulatory mechanism governing this process needs further investigation. In this study, a novel microRNA, temporarily named miR-1959, was first identified from an invertebrate Litopenaeus vannamei. miR-1959 targets the 3′-untranslated region of the IκB homolog Cactus gene and reduces the protein level of Cactus in vivo, whereas the NF-κB homolog Dorsal directly binds the miR-1959 promoter to activate its transcription. Therefore, miR-1959 mediates a positive feedback regulatory loop, in that Dorsal activates miR-1959 expression, and in turn, miR-1959 inhibits the expression of Cactus, further leading to enhanced activation of Dorsal. Moreover, miR-1959 regulates the expression of many antimicrobial peptides in vivo and is involved in antibacterial immunity. To our knowledge, it is the first discovery of a microRNA-mediated feedback loop that directly regulates the NF-κB/IκB complex. This positive feedback loop could collaborate with the known NF-κB/IκB negative loop to generate a dynamic balance to regulate the activity of NF-κB, thus constituting an effective regulatory mechanism at the critical node of the NF-κB pathway.

Time-dependent density functional theory (TD-DFT) method at B3LYP/6-31G(d,p) theoretical level was employed to investigate the excited-state intramolecular proton transfer (ESIPT) reaction of 6-amino-2-(2′-hydroxyphenyl)benzoxazole in dichloromethane and methanol solvents. Upon photo-excitation, the intramolecular hydrogen bond between the hydroxyl and neighboring N atom is significantly strengthened, which provides a driving force in facilitates the ESIPT reaction. The calculated steady-state absorption and fluorescence spectra agree well with the experimental results. Especially, after the photo-excitation from HOMO (π) to LUMO (π*), the rearrangement of electronic density distribution of frontier molecular orbitals (MOs) is a very important positive factor for the ESIPT process. The potential energy curves confirm that, after photo-excitation, the EXIPT reaction occurs with the H atom of the hydroxyl group remove to the neighboring N atom. By contrast, the potential barrier of the 6A-HBO-MeOH complex in the S 1 state falls ca. 3.57 kcal/mol, lower than the isolated 6A-HBO. It is likely that the ESIPT reaction occurs more easily for the 6A HBO-MeOH complex due to the influence of the intermolecular hydrogen bonding.

The excited-state intramolecular proton transfer (ESIPT) reactions of 2-(2′-hydroxyphenyl)benzoxazole (HBO), 5-amino-2-(2′-hydroxyphenyl)benzoxazole (5A-HBO) and 6-amino-2-(2′-hydroxyphenyl)benzoxazole (6A-HBO) were investigated with the time-dependent density functional theory (TD-DFT) method at the B3LYP/6-31G(d,p) theoretical level. The primary bond lengths and infrared (IR) vibrational spectra show that the intramolecular hydrogen bond is significantly strengthened in S1 state. The Mulliken's charge distribution and the frontier molecular orbitals (MOs) were analyzed. The result is consistent with the ESIPT mechanism proposed by Han and co-workers. Upon photo-excitation, the intramolecular hydrogen bond of 5A-HBO-enol (1.73 A) and 6A-HBO-enol (1.74 A) in the S1 state is weaker than that of HBO-enol (1.69 A) due to the influence of the amino group in the HBO framework. After vertical excitation to the S1 state, the electronic density redistributes and migrates from the phenol ring to the benzoxazole ring of HBO. While for 5A-HBO and 6A-HBO, it transfers from the amino-benzoxazole moiety to the phenol ring. The analysis of the potential energy curves of HBO, 5A-HBO and 6A-HBO indicates that the ESIPT process of HBO occurs most easily. It is demonstrated that the presence and the position of the amino group in the HBO framework can change the behavior of the intramolecular hydrogen bonds O–H⋯N in the S1 state and thus hinder the ESIPT processes to some extent.

In this work, the influence of cyanide group substituted on the excited-state intramolecular proton transfer of 2-(2-hydroxyphenyl)benzothiazole (HBT) has been theoretical studied. It is found that the intramolecular hydrogen bonds of HBT and its cyanide substituted derivatives are significantly strengthened in the first excited (S1) state, while this strengthening tends to decrease with the substitution of cyano group. The natural population analysis (NPA) is performed to interpret this phenomenon and the calculated results show that the introduction of cyano groups induces intramolecular charge transfer, leading to the decrease of electrostatic interaction of intramolecular hydrogen bond in the S1 state compared to isolated HBT. Therefore, proton transfer of HBT and its derivatives become difficult with the introduction of cyano groups, which is consistent with the calculated potential barriers (1.95, 2.71 and 2.81 kcal/mol respectively) of the three molecules in the S1 state. This work interprets the hindrance of cyanide group on the proton transfer of HBT and its derivatives in the S1 state, which will bring new insight into the study of analogous molecular system.

Asymmetric substitution has not been termed as an essential factor in studying photo-induced ultrafast dynamics of molecular system. Asymmetric 4-hydroxybut-3-en-2-one (HEO), together with symmetric malonaldehyde (MA) and acetylacetone (AA), have been provided as target sample to study the nonradiative decay (ND) processes of β-diketones. An effective ND pathway of the three molecules is presented that their excited second (S2) states transfer to first (S1) state by nonadiabatic surface hopping, and then transfer to triplet (T1) state by crossing minimum energy crossing point (MECP), after which decay to ground (S0) state through MECP. More importantly, the asymmetric substitution of HEO induces the proton transfer in the S1 state and generates a proton-transferred conformer with lowest energy, which does not occur for MA and AA. This change exploits a new ND pathway that the S1 state decays to the proton transferred T1 state and then undergoes reverse proton transfer to S0 state through the MECPs between the three states. The two pathways of HEO give detailed energy and geometric information on surface hopping of S2/S1 and MECPs of S1/T1/S0, and interpret the reason of the ND pathway while not spectra emission. This result is significantly different from the previous reported ND pathway of photoisomerization or conical intersection between different states. This work shows that asymmetric substitution changes the molecular structure and then changes their spectra behaviors.

In this work, density functional theory (DFT) calculations were carried out to study the role of solvation effects on the reaction of diiron dithiolate complex with CO to form [Fe]-hydrogenase model complex. In the gas phase, the energy barrier of the first transition state TS 1 species is ca. 6.1 kcal/mol higher than the second transition state TS 2 species. However, when the solvation effects were included, the energy order was reversed, i.e., the energy barrier of TS 1 falls ca. 1.2 kcal/mol lower than TS 2 , indicating that the insertion of the second CO to iron is the rate-determining step in the whole transformation process. The initial insertion of the CO plays an important role in increasing the reaction barrier of the binding of a second CO, which prevented the second step transformation. Thus, the solvation effects play a significant role in determining the reaction mechanism. In addition, the energy of PC species is lower than RC species, demonstrating that this transformation is a significantly exothermic process.

The NF-κB family transcription factors regulate a wide spectrum of biological processes, in particular immune responses. The studies in human suggest that the NF-κB repressing factor (NKRF) negatively regulates the activity of NF-κB through a direct protein-protein interaction. However, the function of NKRF has not been studied outside mammals up to now. The current study identified a NKRF gene (LvNKRF) from the Pacific white shrimp, Litopenaeus vannamei, which showed homology with NKRFs from insects, fishes and mammals. LvNKRF was high expressed in intestine, stomach and muscle tissues and was localized in the nucleus. LvNKRF could interact with both Dorsal and Relish, the two members of the shrimp NF-κB family. Interestingly, although sharing a similar protein structure with that of human NKRF, LvNKRF showed no inhibitory but instead enhancing effects on activities of Dorsal and Relish, which was contrary to those of mammalian NKRFs. The expression of LvNKRF could not be induced by Gram-positive and -negative bacteria and immunostimulants lipopolysaccharide (LPS) and poly (I:C) but was significantly up-regulated after white spot syndrome virus (WSSV) infection. Silencing of LvNKRF significantly decreased the mortalities of shrimp caused by WSSV infection and down-regulated the WSSV copies and the expression of WSSV structural gene in tissues. These suggested that LvNKRF could facilitate the infection of shrimp by WSSV, which may be an additional strategy for WSSV to hijack the host NF-κB pathway to favor its own replication. The current study could provide a valuable context for further investigating the evolutionary derivation of NKRFs and facilitate the study of regulatory mechanisms of invertebrate NF-κB pathways.

p53 is a transcription factor with capability of regulating diverse NF-κB dependent biological progresses such as inflammation and host defense, but the actual mechanism remains unrevealed. Herein, we firstly identified two novel alternatively spliced isoforms of p53 from Litopenaeus vannamei (LvΔNp53 and the full-length of p53, LvFLp53). We then established that the two p53 isoforms exerted opposite effects on regulating NF-κB induced antimicrobial peptides (AMPs) and white spot syndrome virus (WSSV) immediate-early (IE) genes expression, suggesting there could be a crosstalk between p53 and NF-κB pathways. Of note, both of the two p53 isoforms could interact directly with LvDorsal, a shrimp homolog of NF-κB. In addition, the activation of NF-κB mediated by LvDorsal was provoked by LvΔNp53 but suppressed by LvFLp53, and the increased NF-κB activity conferred by LvΔNp53 can be attenuated by LvFLp53. Furthermore, silencing of LvFLp53 in shrimp caused higher mortalities and virus loads under WSSV infection, whereas LvΔNp53-knockdown shrimps exhibited an opposed RNAi phenotype. Taken together, these findings present here provided some novel insight into different roles of shrimp p53 isoforms in immune response, and some information for us to understand the regulatory crosstalk between p53 pathway and NF-κB pathway in invertebrates.

There is very little scientific understanding of photoexcitation effect on the adsorption properties of adsorbent. The adsorption of four hazardous gases (SARIN (propan-2-ylmethylphospho-nofluoridate), methyl dichlorophosphate (MDCP), trimethyl phosphate (TMP) and hydrogen sulfide (H2S)) on silica surface is taken as target sample in this work. The adsorption energy order (MDCP

The toll-like receptor (TLR)/NF-κB signaling pathways play critical roles in the innate immune system. The intracellular signal transduction of most TLR pathways in invertebrate cells is triggered by formation of a heterotrimeric complex composed of MyD88, Tube and Pelle. In this study, we identified a Litopenaeus vannamei Pelle (LvPelle) and an isoform of L. vannamei Tube (LvTube) designated as LvTube-1. The interactions among LvPelle, LvTube/LvTube-1 and LvMyD88/LvMyD88-1 were elucidated and their functions during pathogen infections were investigated. Knockdowns of LvPelle and LvTube/LvTube-1 using RNAi strategy led to higher mortalities of shrimps during Vibrio parahemolyticus infection, and could reduce the genome copy number of white spot syndrome virus (WSSV) in the infected muscle tissue but did not affect the mortality caused by WSSV infection. The effects of LvPelle and LvTube/LvTube-1 on promoters containing NF-κB binding motifs were analyzed by dual-luciferase reporter assays and the results demonstrated that LvTube-1 could activate the NF-κB activity to significantly higher level than LvTube did. Moreover, tissue distributions of LvTube and LvTube-1 mRNAs and their expression profiles during pathogen and immune stimulant challenges were different, indicating that they could play different roles in immune responses. This is the first report of Tube isoforms in invertebrates. Together with our previous study on LvMyD88 isoforms, our results suggest that various isoforms of adaptor components may be involved in various regulatory patterns of signal transduction in invertebrate TLR/NF-κB pathway and this could be a strategy adopted by invertebrates to modulate immune responses.

The dispersion-corrected density functional theory (DFT-D3) is used to investigate the mechanism of mesoporous pulp waste (MPW) and polyaniline (PANI) adsorptive removal methyl orange (MO) dye from their aqueous solutions. The results are absolutely reliable because of the sufficiently accurate method although such big systems are studied. It is demonstrated that hydrogen bond and Van Der Waals interactions play a significant role in MO adsorption by MPW and PANI. For MO adsorption by MPW, hydrogen bond and Van Der Waals interactions are both weakened in S1 state. In contrast, hydrogen bond and Van Der Waals interactions between PANI and MO are both enhanced in S1 state. The thermodynamic parameters such as enthalpy and free energy change reveal that the MO adsorption by MPW and PANI are spontaneous and exothermic. The adsorption of MO on MPW is less favorable in S1 state and the adsorption of MO on PANI is more favorable in S1 state. Therefore, the photoexcitation should be controlled during the MO adsorption by MPW and applied for MO adsorption by PANI.

The 1,8-Dihydroxydibenzo[a,c]phenazine (DHBP) is chosen to investigate the relationship among the extension of π-conjugation framework, excited-state proton transfer and the Stokes shift. The IR spectra, bond and angle analyses show that the two intramolecular hydrogen bonds in DHBP molecule are both significantly strengthened in S 1 state. The proton donor methanol molecule can inhibits the hydrogen bond strengthening in S 1 state. The increment of π-conjugation framework effectively decreases the Stokes shift and promotes the proton transfer. The potential energy surfaces of DHBP indicate that the reverse double-proton transfer can spontaneously happen in S 0 state, and the double proton can easily transfer for its relative low potential energy barrier in S 1 state.

The 1,3-bis(2-pyridylimino)-4,7-dihydroxyisoindole (BPD) is chosen to investigate the excited-state double proton transfer process (ESDPT). The IR spectra, bond distance, and angle analyses show that the two intramolecular hydrogen bonds in the BPD molecule, formed between hydroxyl group and pyridine-type nitrogen atom, are significantly strengthened in the S1 state. The potential energy surfaces in both S0 and S1 states are scanned with varying O–H bond lengths to visually investigate the double proton transfer mechanism. Compared with previous investigations, the proton transfer process can be interpreted in more detail. The hydrogen bond strengthening promotes the proton transfer in the S1 state effectively. The large Stocks shift observed in the experiment can be explained more comprehensively according to the ESDPT mechanism.

Pellino, named after its property that binds Pelle (the Drosophila melanogaster homolog of IRAK1), is a highly conserved E3 class ubiquitin ligase in both vertebrates and invertebrates. Pellino interacts with phosphorylated IRAK1, causing polyubiquitination of IRAK1, and plays a critical upstream role in the toll-like receptor (TLR) pathway. In this study, we firstly cloned and identified a crustacean Pellino from pacific white shrimp Litopenaeus vannamei (LvPellino). LvPellino contains a putative N-terminal forkhead-associated (FHA) domain and a C-terminal ring finger (RING) domain with a potential E3 ubiquitin-protein ligase activity, and shows a high similarity with D. melanogaster Pellino. LvPellino could interact with L. vannamei Pelle (LvPelle) and over-expression of LvPellino could increase the activity of LvDorsal (a L. vannamei homolog of NF-κB) on promoters containing NF-κB binding motifs and enhance the expression of arthropod antimicrobial peptides (AMPs). The LvPellino protein was located in the cytoplasm and nucleus and LvPellino mRNA was detected in all the tissues examined and could be up-regulated after lipopolysaccharides, white spot syndrome virus (WSSV), Vibrio parahaemolyticus, and Staphylococcus aureus challenges, suggesting a stimulation response of LvPellino to bacterial and immune stimulant challenges. Knockdown of LvPellino in vivo could significantly decrease the expression of AMPs and increase the mortality of shrimps caused by V. parahaemolyticus challenge. However, suppression of the LvPellino expression could not change the mortality caused by WSSV infection, and dual-luciferase reporter assays demonstrated that over-expression of LvPellino could enhance the promoters of WSSV genes wsv069 (ie1), wsv303, and wsv371, indicating a complex role of LvPellino in WSSV pathogenesis and shrimp antiviral mechanisms.

Many viruses can hijack the host cell NF-κB as part of their life cycle, diverting NF-κB immune regulatory functions to favor their replications. There were several reports on the functions of Litopenaeus vannamei NF-κB (LvNF-κB) in White spot syndrome virus (WSSV) replication in vitro. Here, we studied the relationship between LvNF-κB family protein Dorsal (LvDorsal) and Relish (LvRelish) with WSSV replication in vivo. The expressions of LvDorsal and LvRelish were significantly upregulated by WSSV challenge. Virus loads and expression of viral envelope protein VP28 in LvDorsal or LvRelish silencing shrimps were significantly lower than the control shrimps injected with EGFP-dsRNA or PBS after challenge with 1×10(5) copies WSSV/shrimp. In addition to the LvDorsal activation of WSV069 (ie1) and WSV303 promoter that we have reported, LvRelish can also activate WSV069 (ie1) and WSV303 promoter by dual luciferase reporter assays through screening 40 WSSV gene promoters that have putative multiple NF-κB binding sites. The promoter activity of the WSV069 (ie1) by LvDorsal activation was significantly higher than that by LvRelish activation. WSSV replication in LvDorsal, LvRelish or WSV303 silencing shrimps were significantly inhibited. These results indicate that the L. vannamei NF-κB family proteins LvDorsal and LvRelish expressions are significantly activated by WSSV challenge and WSSV replication partially relied on the activations of LvDorsal and LvRelish in vivo.