Maximum Fluorescence Wavelength Research Articles

Synthesis of Side-Chain Liquid Crystalline Polyacrylates with Bridged Stilbene Mesogens.

In recent years, π-conjugated liquid crystalline molecules with optoelectronic functionalities have garnered considerable attention, and integrating these molecules into side-chain liquid crystalline polymers (SCLCPs) holds potential for developing devices that are operational near room temperature. However, it is difficult to design SCLCPs with excellent processability because liquid crystalline mesogens are rigid rods, have low solubility in organic solvents, and have a high isotropization temperature. Recently, we developed near-room-temperature π-conjugated nematic liquid crystals based on "bridged stilbene". In this work, we synthesized a polyacrylate SCLCP incorporating a bridged stilbene that exhibited a nematic phase near room temperature and could maintain liquid crystallinity for more than three months. We conducted a thorough phase structure analysis and evaluated the optical properties. The birefringence values of the resulting polymers were higher than those of the corresponding monomers because of the enhanced order parameters due to the polymer effect. In addition, the synthesized polymers inherited mesogen-derived AIE properties, with high quantum yields (Φfl = 0.14-0.35) in the solid state. It is noteworthy that the maximum fluorescence wavelength exhibited a redshift of greater than 27 nm as a consequence of film formation. Thus, several unique characteristics of the SCLCPs are unattainable with small molecular systems.

A Fluorescent Organic Probe for Naked-Eye Detection of Chloromethanes.

An organic fluorescent probe (OFP-TAR) with a propeller-like structure was designed and synthesized. The photoluminescence of OFP-TAR in solution exhibited a significant red shift with the increase of solvent polarity, enabling a transition of fluorescence emission from blue (445 nm) to yellow (540 nm). The organic thin-film materials based on OFP-TAR/PMMA exhibit significant color changes upon exposure to CH2Cl2, CHCl3, and CCl4, with their maximum fluorescence wavelengths measured at 445, 471, and 494 nm respectively. The device facilitates the visual detection of chloromethanes and is capable of enduring more than 7 cycles of testing. These materials can also be prepared as binary-coded microarray data storage devices or applied in the field of anti-counterfeiting. The quantum yields of guest-loaded crystals CH2Cl2@OFP-TAR, CHCl3@OFP-TAR and CCl4@OFP-TAR are observed as 19.13 %, 8.79 %, and 0.83 % respectively, which are consistent with the tendency of OFP-TAR in CH2Cl2 (47.30 %), CHCl3 (34.27 %) and CCl4 (3.10 %). The fluorescence properties of OFP-TAR, OFP-TAR/PMMA, guest-loaded and guest-free crystals provided insights into the special response mechanism of OFP-TAR towards different chloromethanes.

Metal-induced self-assemble transition: Triple responses on photophysical, liquid crystalline and gel properties of Hg(II)-coordination tetraphenylene dimer

The metal-coordination self-assemble system played an important role on constructing novel supramolecular smart-response materials. Although the single and double-response materials based on metal-induced self-assembly had been studied extensively, the triple responses for this kind of supramolecular material was seldom reported. In this work, the first metal-induced self-assemble system with triple responses on photophysical, liquid crystalline and gel properties was presented based on Hg2+-coordination tetraphenylene dimer (Bis-TPE). Bis-TPE was prepared by bridging two alkyl-substituted tetraphenylene with amido chain. It possessed the fluorescence response from the strong emission for Bis-TPE to the faint emission for Bis-TPE-Hg2+ complex. The self-assemble mechanism of Bis-TPE-Hg2+ was clarified as that Hg2+ was located in the cavity of the amido-ether chain of Bis-TPE. The Hg2+-induced mesomorphic transition was also observed from smectic mesophase for Bis-TPE to hexagonal columnar mesophase for Bis-TPE-Hg2+ complex. The unique Hg2+-induced gel transition was further distinguished from low-order spherical morphology for Bis-TPE to high-order fibrous morphology for Bis-TPE-Hg2+ complex. The maximum fluorescence wavelength exhibited the giant shift from 494 nm for Bis-TPE in gel to 606 nm for Bis-TPE-Hg2+ in gel. This kind of triple responses on photophysical, liquid crystalline and gel properties for metal-coordination self-assemble system was described for the first time, affording a new idea on design of new multiple-response materials with unique properties.

Synergistic Anti-Inflammatory Activity of Lipid-Free Apolipoprotein (apo) A-I and CIGB-258 in Acute-Phase Zebrafish via Stabilization of the apoA-I Structure to Enhance Anti-Glycation and Antioxidant Activities.

CIGB-258, a 3 kDa peptide from heat shock protein 60, exhibits synergistic anti-inflammatory activity with apolipoprotein A-I (apoA-I) in reconstituted high-density lipoproteins (rHDLs) via stabilization of the rHDL structure. This study explored the interactions between CIGB-258 and apoA-I in the lipid-free state to assess their synergistic effects in the structural and functional enhancement of apoA-I and HDL. A co-treatment of lipid-free apoA-I and CIGB-258 inhibited the cupric ion-mediated oxidation of low-density lipoprotein (LDL) and a lowering of oxidized species in the dose-responsive manner of CIGB-258. The co-presence of CIGB-258 caused a blue shift in the wavelength of maximum fluorescence (WMF) of apoA-I with protection from proteolytic degradation. The addition of apoA-I:CIGB-258, with a molar ratio of 1:0.1, 1:0.5, and 1:1, to HDL2 and HDL3 remarkably enhanced the antioxidant ability against LDL oxidation up to two-fold higher than HDL alone. HDL-associated paraoxonase activities were elevated up to 28% by the co-addition of apoA-I and CIGB-258, which is linked to the suppression of Cu2+-mediated HDL oxidation with the slowest electromobility. Isothermal denaturation by a urea treatment showed that the co-presence of CIGB-258 attenuated the exposure of intrinsic tryptophan (Trp) and increased the mid-points of denaturation from 2.33 M for apoA-I alone to 2.57 M for an apoA-I:CIGB-258 mixture with a molar ratio of 1:0.5. The addition of CIGB-258 to apoA-I protected the carboxymethyllysine (CML)-facilitated glycation of apoA-I with the prevention of Trp exposure. A co-treatment of apoA-I and CIGB-258 synergistically safeguarded zebrafish embryos from acute death by CML-toxicity, suppressing oxidative stress and apoptosis. In adult zebrafish, the co-treatment of apoA-I+CIGB-258 exerted the highest anti-inflammatory activity with a higher recovery of swimming ability and survivability than apoA-I alone or CIGB-258 alone. A co-injection of apoA-I and CIGB-258 led to the lowest infiltration of neutrophils and interleukin (IL)-6 generation in hepatic tissue, with the lowest serum triglyceride, aspartate transaminase, and alanine transaminase levels in plasma. In conclusion, the co-presence of CIGB-258 ameliorated the beneficial functionalities of apoA-I, such as antioxidant and anti-glycation activities, by enhancing the structural stabilization and protection of apoA-I. The combination of apoA-I and CIGB-258 synergistically enforced the anti-inflammatory effect against CML toxicity in embryos and adult zebrafish.

Fluorescence behaviors of perylene-dispersed super engineering plastic films

We attempted to manufacture films in which fluorescent dye is dispersed using engineering plastic as a matrix which has high heat and chemical resistance as well as excellent mechanical performance. In this study, films containing highly dispersed perylene in colorless and transparent aromatic polyamide (PA) and polyimide (PI) were manufactured. The perylene-dispersed PA film emitted strong blue light with a maximum fluorescence at 457 nm. On the other hand, the perylene-dispersed PI film showed significant fluorescence quenching with its maximum fluorescence wavelength significantly red-shifted to 546 nm. The perylene-dispersed PI film treated with ethylene diamine at 80 °C showed strong blue fluorescence, and when the film was further heated at 200 °C, the fluorescence was quenched. These films are expected to be applied as back light unit or color conversion layer for OLED and Micro LED due to their excellent physical properties.

The Solvent Effect on Nanomaterials Composed of Liquid Crystals and Nanoparticles: uv-vis Absorbance and Fluorescence Spectra

We have been investigated in different solvent medium to interactions between 4-Ethoxybenzoic acid (4EOBA), 4-Pentylbenzoic acid (4PentBA), and 4-Pentylphenyl 4-Methylbenzoate (4PP4MetB) liquid crystals with CdS, CdSe and ZnS nanoparticles. For this, the new materials composed from LC compound including the solvent and nanoparticle were investigated by use absorbance and fluorescence spectra. Electronic transitions and differences in absorbance and fluorescence spectra were interpreted. The fluorescence of liquid crystals has been defined in the shifts between wavelengths of the fluorescence of nanomaterials. It can be said that it has occurred blue shift at the maximum fluorescence wavelengths of the 4EOBA-CdS-DMSO and 4EOBA-CdSe-DMSO compared to 4EOBA-DMSO. On the other hand, we can say that in the 4EOBA-ZnS-DMSO solution occurs red shift in the fluorescence band, while the peaks seen in the fluorescence band occur in result of interaction of liquid crystals and nanoparticles.

Reductant-mediated unfolding of soy 11S globulin enhancing its interaction with curcumin

Loading hydrophobic bioactive with protein-based nanocarrier is challenged by inefficient encapsulation or colloidal instability. In this study, unfolding 11S globulin was induced by reducing disulfide bonds to form nanoparticles which served as effective nanocarriers for curcumin. Results revealed that 11S globulin unfolded after reducing treatment, as proved by the red-shifting in maximum fluorescence wavelength and the transitions of secondary structure. Disulfide-linked subunits progressively dissociated into their separate polypeptides and even vanished at high reductant concentrations. Reductant-treated 11S globulin was characterized by exposed hydrophobic regions, evidenced by the increased surface hydrophobicity and fluorescence quenching, which triggered the hydrophobic interaction between protein and curcumin. Finally, up to 98.77% of curcumin (0.5 mg/mL) could be encapsulated into 11S globulin nanoparticles. 11S-Cur complex exhibited superior thermal stability, with enhanced water solubility compared to the free curcumin. Accordingly, reducing treatment can be considered a facile and high-encapsulation-performance method to fabricate protein-based nanoparticles for embedding hydrophobic bioactive.

Development of multifunctional curcuminoid dye-based inks and applications

Curcuminoids are a group of naturally occurring polyphenolic compounds found in turmeric (Curcuma longa) that are widely employed as coloring agents in traditional medicine and the food industry. Moreover, they have been used as dyes in pH indicators, which are part of diagnostic intelligent packaging. Recently, there has seen a steady increase of the interest in the curcuminoids due to their fluorescent property. In this study, a curcuminoid dye (CurD) containing a total curcuminoid content of 38.34 ± 0.66 % w/w was prepared by using a microwave-assisted extraction, and was used as a multifunctional dye with different commercial screen binders, including solvent-based ink (Si) and water-based ink (Wi). A solution of CurD (0.1 % w/v) exhibited a maximum fluorescence wavelength of 526 nm. Based on the print-quality test using a screen printing on clear polyvinyl chloride and paper, the viscosity and drying time of CurD-Si and CurD-Wi inks were not significantly different. The printed-inks had a yellow color under illuminant D50 and D65, and exhibited remarkable green fluorescence under UVA (365 nm). The total color differences (∆Eab∗), which are not fluorescence intensities, of both inks were changed by increasing CurD concentrations. CurD-Wi containing 1 % w/w CurD could be printed as latent graphics on a paper label for use as an anti-counterfeiting application. In addition, it immediately responded to alkaline solution and vapor through color transition from yellow to orange-brown, with the maximum ∆Eab∗ values of 15.02 and 26.62, respectively. In contrast, all CurD-Si samples could fluoresce but did not respond to alkaline conditions.

Heteroatom substitution controlled luminescent property and excited state intramolecular proton transfer (ESIPT) process of novel benzothiazole-based fluorophore: A TD-DFT investigation

By using density functional theory (DFT) and time-dependent DFT (TD-DFT) methods, we have systematically explored the spectral characteristics and excited state intramolecular proton transfer (ESIPT) processes of 3-(benzo[d]thiazol-2-yl)-2-hydroxy-5-methylbenzaldehyde (BTFM-OH) and its derivatives. The sulfur (S) atom in the thiazole ring of BTFM-OH was replaced by O/Se atom (denoted to BOFM-OH/BSeFM-OH) to probe the impact of heteroatom substitution on the luminescent property and ESIPT process. The simulated maximum absorption and fluorescence wavelengths of BTFM-OH are well consistent with the experimental values. From BOFM-OH to BTFM-OH and BSeFM-OH, the red-shifts of absorption and fluorescence (at normal and tautomer forms) wavelengths are found, which is in good accordance with the decreasing order of ground state and excited state HOMO-LUMO gaps of BOFM-OH < BTFM-OH < BSeFM-OH. According to the data obtained from structure, infrared vibrational frequency and electron density, it can be found that the intramolecular hydrogen bonds (IHBs) are enhanced in the S1 state, which is favorable to ESIPT process. From BOFM-OH to BTFM-OH and BSeFM-OH, the atomic electron-withdrawing ability of heteroatom is decreasing from O to S and Se, the IHB strengths become stronger in the order of BOFM-OH < BTFM-OH < BSeFM-OH, which makes the ESIPT process occur much easier along this order.

Alternative Strategy for Spectral Tuning of Flavin-Binding Fluorescent Proteins.

iLOV is an engineered flavin-binding fluorescent protein (FbFP) with applications for in vivo cellular imaging. To expand the range of applications of FbFPs for multicolor imaging and FRET-based biosensing, it is desirable to understand how to modify their absorption and emission wavelengths (i.e., through spectral tuning). There is particular interest in developing FbFPs that absorb and emit light at longer wavelengths, which has proven challenging thus far. Existing spectral tuning strategies that do not involve chemical modification of the flavin cofactor have focused on placing positively charged amino acids near flavin's C4a and N5 atoms. Guided by previously reported electrostatic spectral tunning maps (ESTMs) of the flavin cofactor and by quantum mechanical/molecular mechanical (QM/MM) calculations reported in this work, we suggest an alternative strategy: placing a negatively charged amino acid near flavin's N1 atom. We predict that a single-point mutant, iLOV-Q430E, has a slightly red-shifted absorption and fluorescence maximum wavelength relative to iLOV. To validate our theoretical prediction, we experimentally expressed and purified iLOV-Q430E and measured its spectral properties. We found that the Q430E mutation results in a slight change in absorption and a 4-8 nm red shift in the fluorescence relative to iLOV, in good agreement with the computational predictions. Molecular dynamics simulations showed that the carboxylate side chain of the glutamate in iLOV-Q430E points away from the flavin cofactor, which leads to a future expectation that further red shifting may be achieved by bringing the side chain closer to the cofactor.

A New Ratiometric Fluorescent Probe Based on BODIPY for Highly Selective Detection of Hydrogen Sulfide.

Hydrogen sulfide (H2S) as small molecular signal messenger plays key functions in numerous biological processes. The imaging detection of intracellular hydrogen sulfide is of great significance. In this work, a ratiometric fluorescent probe BH based on an asymmetric BODIPY dye for detection of H2S was designed and synthesized. After the interaction with hydrogen sulfide, probe display colorimetric and ratiometric fluorescence response, with its maximum emission fluorescence wavelength red-shifted from 542 nm to 594 nm, which is attributed to the sequential nucleophilic reaction of H2S leading to enhanced molecular conjugation after ring formation of the BODIPY skeleton. A special response mechanism has been fully investigated by NMR titration and MS, so that the probe has excellent detection selectivity. Furthermore, probe BH has low cytotoxicity and fluorescence imaging experiments indicate that it can be used to monitor hydrogen sulfide in living cells.

Near-Infrared Liposome-Capped Au-Rare Earth Bimetallic Nanoclusters for Fluorescence Imaging of Tumor Cells

Early detection of cancer can effectively improve the survival rate of cancer patients. Fluorescence imaging has the advantages of high sensitivity and rapid imaging, and is widely used in the precise imaging detection of tumors. In this study, five kinds of Au-rare earth bimetallic nanoclusters (Au/Ln NCs) were prepared by template method using five representative rare earth elements doped with gold. The morphologies, surface charges, sizes, fluorescence quantum yields and maximum fluorescence emission wavelengths of these five kinds of Au/Ln NCs were characterized and contrasted. The findings indicated that the Au/Ce nanoclusters (Au/Ce NCs) prepared by Ce doping have the longest fluorescence emission wavelength (695 nm) and higher quantum yield, which could effectively avoid the interference of autofluorescence, and was suitable for fluorescence imaging of tumor cells. In order to improve the specific accumulation of nanoclusters in tumor cells, Au/Ce NCs were coated with folic acid modified liposomes (lip-FA) to constructed a targeted fluorescent imaging probe with near-infrared response (Au/Ce@lip-FA), which was successfully used for fluorescence imaging of tumor cells. The probe has the characteristics of stable fluorescence signal, good targeting, easy internalization, and safe metabolism, and can provide high-resolution and high-brightness imaging information, which is expected to play an important role in the clinical diagnosis and surgical treatment of tumors.

Synthesis, optical and electrochemical properties of (D-π)2-type and (D-π)2Ph-type fluorescent dyes.

The (D–π)2-type fluorescent dye OTT-2 with two (diphenylamino)carbazole-thiophene units as D (electron-donating group)–π (π-conjugated bridge) moiety and the (D–π)2Ph-type fluorescent dye OTK-2 with the two D–π moieties connected through a phenyl ring were derived by oxidative homocoupling of a stannyl D–π unit and Stille coupling of a stannyl D–π unit with 1,3-diiodobenzene, respectively. Their optical and electrochemical properties were investigated by photoabsorption and fluorescence spectroscopy, time-resolved fluorescence spectroscopy, cyclic voltammetry (CV) and molecular orbital (MO) calculations. In toluene the photoabsorption and fluorescence maximum wavelengths (λmax,abs and λmax,fl) of OTT-2 appear in a longer wavelength region than those of OTK-2. The fluorescence quantum yield (Φfl) of OTT-2 is 0.41, which is higher than that (Φfl = 0.36) of OTK-2. In the solid state OTT-2 shows relatively intense fluorescence properties (Φfl-solid = 0.24 nm), compared with OTK-2 (Φfl-solid = 0.15 nm). CV results demonstrated that OTT-2 and OTK-2 exhibit a reversible oxidation wave. Based on photoabsorption, fluorescence spectroscopy and CV for the two dyes, it was found that the lowest unoccupied molecular orbital (LUMO) energy level of OTT-2 is lower than that of OTK-2, but OTT-2 and OTK-2 have comparable highest occupied molecular orbital (HOMO) energy levels. Consequently, this work reveals that compared to the (D–π)2Ph-type structure, the (D–π)2-type structure exhibits not only a bathochromic shift of the photoabsorption band, but also intense fluorescence emission both in solution and the solid state.

Efficacy Comparison Study of Human Epidermal Growth Factor (EGF) between Heberprot-P® and Easyef® in Adult Zebrafish and Embryo under Presence or Absence Combination of Diabetic Condition and Hyperlipidemia to Mimic Elderly Patients.

Recombinant human epidermal growth factor (EGF) has been used to treat adult diabetic foot ulcers and pediatric burns by facilitating wound healing and epithelization, especially for elderly patients. Several formulation types of EGF from different expression hosts are clinically available, such as intralesional injection and topical application. On the other hand, no study has compared the in vivo efficacy of EGF products directly in terms of tissue regeneration and wound healing activity. The present study compared two commercial products, Heberprot-P75® and Easyef®, in terms of their tissue regeneration activity in adult zebrafish and the developmental speed of zebrafish embryos. Fluorescence spectroscopy showed that the two EGF products had different Trp fluorescence emission spectra: Easyef® showed a wavelength of maximum fluorescence (WMF) of 337 nm with weak fluorescence intensity (FI), while Heberprot-P75® showed WMF of 349 nm with a 4.1 times stronger FI than that of Easyef®. The WMF of Heberprot-P75® was quenched by adding singlet oxygen in ozonated oil, while the WMF of Easyef® was not quenched. Treatment with Heberprot-P75® induced greater embryo development speed with a higher survival rate after exposure to EGF in water and microinjection into embryos. Under normal diet (ND) consumption, Heberprot-P75® showed a 1.4 times higher tail fin regeneration activity than Easyef® during seven days from the intraperitoneal injection (10 μL, 50 μg/mL) after amputating the tail fin. Under ND consumption and diabetic condition caused by streptozotocin (STZ) treatment, Heberprot-P75® showed 2.1 times higher tail fin regeneration activity than Easyef® from the same injection and amputation protocol. Under a high-cholesterol diet (HCD) alone, Heberprot-P75® showed 1.2 times higher tail fin regeneration activity than the Easyef® group and PBS group from the same injection and amputation. Under diabetic conditions (STZ-injected) and HCD consumption, the Heberprot-P75® group showed 1.7 and 1.5 times higher tail fin regeneration activity than the Easyef® group and PBS group, respectively, with a distinct and clean regeneration pattern. In contrast, the Easyef® group and PBS group showed ambiguous regeneration patterns with a severe fissure of the tail fin, which is a typical symptom of a diabetic foot. In conclusion, Heberprot-P75® and Easyef® have different Trp fluorescence properties in terms of the WMF and fluorescence quenching. Treatment of Heberprot-P75® induced a greater developmental speed of zebrafish embryos in both water exposure and microinjection. Heberprot-P75® induced significantly higher wound healing and tissue regeneration activity than Easyef® and PBS in the presence or absence of diabetic conditions and cholesterol supplementation.

Machine learning assisted dual-emission fluorescence/colorimetric sensor array detection of multiple antibiotics under stepwise prediction strategy

Effective sensors to detect antibiotics as environmental and health hazards are urgently needed. Herein, we constructed a dual-emission fluorescence/colorimetric sensor array based on novel high fluorescence quantum yield carbon dots and CdTe quantum dots. Multi-dimensional data (fluorescence intensities and maximum emission wavelengths) was used to establish a sensor array platform with improved specificity. To meet the challenges of establishing a unified model and detecting outside datasets samples, we innovatively built a unified SX-model using a “stepwise prediction” strategy combined with machine learning to screen optimal methods. By integrating classification and concentration models under a tree-based pipeline optimization technique framework, the extreme random forest was selected as the most accurate classification model. The sensor array detected nine antibiotics at 0.5–50 μM with 95% accuracy and 4.93% average concentration error for unknown samples outside the datasets. Simultaneous identification of binary and ternary mixed samples was also enhanced. Furthermore, antibiotics in 216 river water and milk samples were discriminated with 100% accuracy and 3.25% and 4.43% average concentration errors of unknown samples outside the datasets, respectively. Finally, antibiotics were completed visually identified. The proposed original SX-model assisted dual-emission sensor not only overcomes low specificity and immobility, but breaks the bottleneck of existing analysis methods showing great application potential in the array detection field.

PH influence on the mechanisms of interaction between chitosan and ovalbumin: a multi-spectroscopic approach

The forces behind supramolecular structures (SS) formation need to be deeply understood, to allow identifying conditions under which their production can be optimized. In this study, a multi-spectroscopic approach was used to study SS formation upon ovalbumin (OVA) and chitosan (CHS) interaction in HCl solution, at pH 4.0 (both biomacromolecules positively charged) or 6.0 (biomacromolecules oppositely charged). UV-Vis and fluorescence spectroscopies showed that the biomacromolecules interacted and formed complexes without suggesting major modifications in the protein’s structure. The increase in CHS concentration progressively augmented the UV-vis absorption of OVA-CHS structures at 278 nm, whereas reduced the fluorescence emission of OVA, at both pH values, without promoting obvious shift of the maximum fluorescence wavelength, with an estimated center of spectral mass of <λ> = 341.41 ± 0.31 nm (at pH 4.0) and <λ> = 342.30 ± 0.40nm (at pH 6.0). Additionally, a conjoint analysis of CD and FT-IR spectroscopies revealed that the presence of CHS promoted alterations on the secondary structure of OVA. Indeed, CHS may have affected the hydrogen bonding network that stabilized the structure in the native protein, increasing the stability of α-helix and random coil structures, which was reflected in the loss of β-sheet. Results suggested that the OVA-CHS interaction, at pH 6.0, are driven mainly by electrostatic forces (attractive) and H-bonds. At pH 4.0, these macromolecules are more likely to interact through a balance of electrostatic forces (repulsive), hydrophobic interactions and H-bonds.

The effects of thermal treatments on the antigenicity and structural properties of soybean glycinin.

The effects of thermal treatments on the antigenicity and structural properties of soybean glycinin were investigated. An indirect enzyme-linked immunosorbent assay (iELISA) result indicated that the antigenicity of the soybean glycinin decreased to the lowest level when the heat treatment time was 50min and the temperature was set at 110°C. The reducing sodium dodecyl sulfate-Gel electrophoresis results showed that the heat treatment had promoted the formation of small molecular weight protein subunits and concentrated protein. The free sulfhydryl (-SH) group of glycinin had increased significantly (p<.05) under the conditions of temperature between 90 and 120°C and 40 to 50min heat treatments. The maximum fluorescence wavelength of the intrinsic fluorescence also changed significantly when compared with the control. The circular dichroism showed that the number of disordered structures had also increased significantly. These results provided evidence that the heat-induced structural modifications of glycinin will alter the antigenicity of soybean glycinin. PRACTICAL APPLICATIONS: The relationship between antigenicity and structural properties of heat-treated soybean globulin was studied by different protein structural research methods. The results showed that the antigenicity of the protein was minimized at 110°C 50min, which could be used in food safety production. This study chose to analyze the changes in the antigenicity and structural characteristics of soybean glycinin, both prior to and after heat treatments, for the purpose of promoting the development of low allergenic food products.

Fluorescence and Micro-FTIR characteristics of typical liptinite at low temperature thermal conversion

The subgroups and contents of liptinite have significant influence on yields of tar and gas in pyrolysis.The heating stage microscope, fluorescence analysis and Micro-FTIR were used to study the characteristics of typical liptinite at low temperature thermal conversion. The results showed that the relative fluorescent intensities decreased and the maximum fluorescence wavelength increased as the pyrolysis temperature increase. The fluorescence characteristics of resinite and suberinite began to change at 240 ℃, and remarkable changed at 280−320 ℃. The fluorescence characteristics of sporinite, cutinite, and bituminite A began to change at 280 ℃, and remarkable changed at 320−360 ℃. The fluorescence characteristic of alginite began to change at 280 ℃, and lasting changed till 400 ℃. The fluorescence characteristic of bituminite B changed at 320−360 ℃. The absorption peak of aliphatic compound in alginite was strongest, and the peaks of bituminite, resinite, cutinite, and sporinite decreased in turn. The aliphatic compounds and oxygen-containing groups of liptinite group decreased and the content of aromatic hydrocarbon relatively increased as the temperature increase. The aromatization degree of liptinite group was low and basically remain unchanged at low temperature thermal conversion. The hydrogen-rich degrees and the change of aliphatic chains of liptinite group confirmed well with the fluorescence characteristics.

DFT and TD-DFT study on quadratic NLO response and optoelectronic activity in novel Y-shaped imidazole-based push-pull chromophores.

A theoretical analysis of a series of imidazole-based Y-shaped chromophores, D1-D8, is performed in order to investigate their non(linear) optical, fluorescence, and charge-transport properties. The calculations have been carried out employing DFT and TD-DFT methods at CAM-B3LYP and M06-2X levels of theory. FMO analysis reveals that in ground state, the highest occupied molecular orbital is localized on the 4,5-dimethylanilino donor moiety and imidazole core while the lowest unoccupied molecular orbital spreads on π-linker and nitro acceptor moieties. Vertical absorption and fluorescence transitions are characterized as intramolecular charge transfer and maximum absorption and fluorescence wavelengths show that by changing the π-bridge to the imidazole C2, we can tune fluorescence color from cyan to orange. Calculated (hyper)polarizabilities show that elongation of π-linker by polarizable subunits, such as double bonds or heteroaromatic rings, increases significantly the nonlinear response and shifts the charge-transfer band bathochromically. Calculated reorganization energies indicate that the studied compounds are hole-transporting materials rather than electron-transporters. Interestingly, D7 and D8, with higher hyperpolarizabilities, are predicted to be potent candidates for NLO-devices while D5 and D8 molecules are expected to be promising candidates for luminescent materials and good hole-transport materials for organic light-emitting diodes.

Study on the effect of substituents on the structure, volatility, and fluorescence of N-(Alkyl or TMS)-2-pyridinamine diethyl aluminum complexes

A series of N-(Alkyl or TMS)-2-pyridinamine ethyl aluminum complex with different substituents were prepared and characterized. When the substituent is n-propyl and n-butyl, the N-(Alkyl or TMS)-2-pyridinamine diethyl aluminum complexes agglomerate at -30 °C. On the contrary, when the substituent is isopropyl and trimethylsilyl, the agglomerate is not easily observed. Compared with the N-(Alkyl or TMS)-2-pyridinamine diethyl aluminum complexes of isopropyl, trimethylsilyl, and isopropyl, the 1H NMR spectra of the pyridine part of N-(n-propyl)-2-pyridinaminoe diethyl aluminum have three sets of peaks. The extra peak may come from the dimer and trimer. Due to the high tension of the quaternary ring and pyridine's influence on the bonding, pyridine did not participate in the coordination, and the optimized monomer structure determines that the monomer is not a quaternary ring structure. Considering the rapid condensation of the liquid product of N-(n-propyl)-2-pyridinaminoe diethyl aluminum at -30 °C, the existence form of compound 2 at different temperatures was determined by variable temperature NMR and simulated NMR. When the temperature reaches 60 °C, the structure of N-(n-propyl)-2-pyridinaminoe diethyl aluminum is a monomer (a stable structure formed with toluene). At -30 °C, the monomer dissociates from the stable structure formed with toluene, and the dimer increases with it. The thermodynamic properties of ethyl aluminum complexes with different substituents were studied by thermal analysis. It was found that the ethyl aluminum complexes with two substituents, isopropyl and trimethylsilyl and difficult to dimerize, were more volatile. The maximum fluorescence wavelength of the complex is affected by the substituents. The spatial and electronic absorption effects of trimethylsilyl make the fluorescence spectrum of the complex 6 blue shift to 406nm. On the contrary, due to the small steric hindrance of n-Propyl, and the easy bonding between Al-N, the fluorescence spectrum of complex 2 shifts to 464nm.