Decrease In Fluorescence Intensity Research Articles

Indirect photodegradation of anthracene and pyrene induced by dissolved organic matter derived reactive species in ice

The influences of dissolved organic matter (DOM) derived reactive species (RS), including singlet oxygen (1O2), hydroxyl radical (•OH) and triplet excited state DOM (3DOM*) on the photodegradation kinetics of polycyclic aromatic hydrocarbons (PAHs) in ice, as well as the spectroscopic changes of PAHs in ice caused by DOM-induced photodegradation were investigated. Anthracene (Ant) and pyrene (Pyr) were chosen as model compounds in this study. The minimum contributions of RS generated from the four DOM to the photodegradation of Ant and Pyr were higher than 20.0 %. •OH contributed more to the photodegradation of Ant and Pyr than 3DOM*. When PAHs coexisted with DOM, direct photodegradation and indirect photodegradation via reaction with 3DOM* seem to have no effect on aliphatic C−C functional groups corresponding to the peak at 1450 cm−1; Photodegradation pathways other than reaction with •OH resulted into the production of C−O functional groups corresponding to the peak at 1113 cm−1; the production of C═O functional groups corresponding to the peak at 1567 cm−1 and the elimination of amide-2 functional groups corresponding to the peak at 1567 cm−1 were attributed to direct photodegradation and indirect photodegradation via reaction with 1O2 and •OH. The fluorescence intensity decreases of Ant when coexisted with DOM were mainly attributed to its direct photodegradation, whereas indirect photodegradation induced by DOM contributed more to fluorescence intensity decreases of Pyr than direct photodegradation.

Albendazole induces an anti-tumor effect and potentiates PD-L1 blockade immunotherapy.

Previously, albendazole (ABZ) has been reported as an anti-parasitic drug rather than anti-tumor drug. Our study aim to investigate whether ABZ also has a potential anti-tumor effect by shaping the tumor immune microenvironment and interrogate whether ABZ could synergize with the PD-L1 blockade. C57BL/6 mice (C57) were intravenously injected with B16F10-luciferase (B16-luc) cells to establish a lung metastatic melanoma model and subcutaneously inoculated with B16-luc cells to establish a subcutaneous tumor model. The tumor volume and tumor metastasis loci of the mice were measured by a vernier caliper and in vivo imaging. RNA sequencing was performed to analyze the different genes and pathways of immune cells in the tumors. Flow cytometry and immunofluorescence were used to analyze the different subsets of tumor-infiltrating immune cells. The results suggested that ABZ significantly inhibited lung melanoma metastasis with decreased fluorescence intensity and nodule score and mediated the regression of subcutaneous melanoma in mice with decreased tumor volume. Moreover, RNA sequencing results showed that ABZ regulated the gene expression levels and pathways of immune cells in the tumor microenvironment (TME). Meanwhile, flow cytometry and immunofluorescence showed that the number and percentage of CD8+ T cells, CD4+ T cells, and TH1 cells were enhanced in tumors after ABZ treatment. Furthermore, the combination of ABZ and anti-PD-L1 treatment significantly potentiated anti-tumor efficacy in both lung metastasis and subcutaneous melanoma models and mediated an increase in the percentage of CD8+ T cells, CD4+ T cells, and TH1 cells as compared to the control group. ABZ inhibits melanoma growth and metastasis. Moreover, ABZ synergized with PD-L1 blockade mediates tumor regression.

Cooperative & competitive binding of anti-myosin tail antibodies revealed by super-resolution microscopy

The MF30 monoclonal antibody, which binds to the myosin subfragment-2 (S2), was found to increase the extent of myofibril shortening. Yet, previous observations found no effect of this antibody on actin sliding over myosin during in vitro motility assays with purified proteins in which myosin binding protein C (MyBPC) was absent. MF30 is hypothesized to enhance the availability of myosin heads (subfragment-1 or S1) to bind actin by destabilizing the myosin S2 coiled-coil and sterically blocking S2 from binding S1. The mechanism of action likely includes MF30's substantial size, thereby inhibiting S1 heads and MyBPC from binding S2. Hypothetically, MF30 should enhance the ON state of myosin, thereby increasing muscle contraction. Our findings indicate that MF30 binds preferentially to the unfolded heavy chains of S2, displaying positive cooperativity. However, the dose-response curve of MF30's enhancement of myofibril shortening did not suggest complex interactions with S2. Single, double, and triple-stained myofibrils with increasing amounts of antibodies against myosin rods indicate a possible competition with MyBPC. Additional assays revealed decreased fluorescence intensity at the C-zone (central zone in the sarcomere, where MyBPC is located), where MyBPC may inhibit MF30 binding. Another monoclonal antibody named MF20, which binds to the light meromyosin (LMM) without affecting myofibril contraction, showed less reduction in fluorescence intensity at the C-zone in expansion microscopy than MF30. Expansion microscopy images of myofibrils labeled with MF20 revealed labeling of the A-band (anisotropic band) and a slight reduction in the labeling at the C-zone. The staining pattern obtained from the expansion microscopy image was consistent with images from photolocalization microscopy which required the synthesis of unique photoactivatable quantum dots, and Zeiss Airyscan imaging as well as alternative expansion microscopy digestion methods. Consistent with the hypothesis that MF30 competes with MyBPC binding to S2, cardiac tissue from MyBPC knockout mice was stained more intensely, especially in the C-zone, by MF30 compared to the wild type.

ZnSSe Decorated Reduced Graphene Oxide for Enhanced Photoelectric Properties

AbstractZSSG (ZnSSe/rGO) composites are prepared by a hydrothermal method. The structure, morphology and material properties are investigated by various tests. Compared to ZnSe, the diffraction peaks of ZnSSe are moved to a larger angle and located between cubic phase ZnSe and cubic phase ZnS. The photocurrent density of ZSSG20 with 20 wt.% graphene is 2.17×10−5 A cm−2, which is 8.9 times higher than that of pure ZnSSe. ZSSG20 has the minimum charge transfer resistance and highest carrier density. The decreased fluorescence intensity in PL spectra indicates that graphene can effectively prevent the recombination of electron‐hole pairs.

An aggregation-induced emission sensor combined with UHPLC-Q-TOF/MS for fast identification of anticoagulant active ingredients from traditional Chinese medicine

Xuebijing injection (XBJ) has a good therapeutic effect on the patients with severe coronavirus disease, but the material basis of XBJ with the anticoagulant effect to improve the coagulopathy and thromboembolism is still unclear. Herein, we developed a new strategy based on aggregation-induced emission (AIE) for monitoring thrombin activity and screening thrombin inhibitors from XBJ. The molecule AIE603 and the thrombin substrate peptide S-2238 were formed into AIE nanoparticle (AIENP) which emitted notable fluorescence due to the restriction of intramolecular motions. In the presence of thrombin, AIENP was specifically hydrolyzed and AIE603 was released from AIENP, leading to the decrease of fluorescence intensity. Furthermore, AIENP was combined with ultra-high performance liquid chromatography-fraction collector (UHPLC-FC) and ultra-high performance liquid chromatography quadrupole-time-of-flight mass spectrometry (UHPLC-Q-TOF/MS) for separation, preparation, screening and identification of the thrombin inhibitors from XBJ, a total of 58 chemical constituents were identified, among which 6 compounds possessed higher anticoagulant activity. Notably, the overall inhibition rate of the 6 mixed standards was equivalent to about 60% of the inhibition rate of XBJ. Therefore, this work provides a novel, cheap and simple method for monitoring thrombin activity and is promising to screen active substances from traditional Chinese medicines.

(Invited) Kinetics of SWCNT Coating Displacement By ssDNA Depends on SWCNT Structure

Non-covalent hybrids formed by suspending single-wall carbon nanotubes (SWCNTs) in single-stranded DNA (ssDNA) present novel phenomena and suggest potential applications in biomedicine and nanotube sorting. Although the structures of these hybrids have been simulated using molecular dynamics calculations, much more experimental research is needed to understand their properties. In this study, selective interactions between SWCNTs and ssDNA are probed by measuring the kinetics by which ssDNA displaces SDS (sodium dodecyl sulfate) coatings on the nanotube surfaces. We used samples initially suspended in a low concentration of SDS to allow the coating displacement to occur and to suppress formation of free SDS micelles. The displacement process was monitored by time-dependent measurements of SWCNT fluorescence intensities and wavelengths. Our experiments showed very smooth decreases in fluorescence intensity and red-shifts in fluorescence wavelengths during the displacement process. Through a series of measurements, we found that ssDNA sequences with repeated guanine (G) and thymine (T) bases showed systematic patterns in the coating displacement kinetics. One result is that SDS displacement depends strongly on oligo length, with (GT)3 showing an initial rate constant 500 times greater than that of (GT)20. For shorter oligos in the (GT) n series, we observe an inverse dependence of initial rate constant on SWCNT diameter, with SDS displacement from (6,5) more than twice as fast as from (8,7). However, this diameter dependence is not present for (GT) n oligos with n greater than 6. We also find a distinct and systematic dependence of initial rate constant on nanotube chiral angle for (GT)5 and (GT)6. This effect gives a factor of ~3 difference between (9,1) and (6,5) despite their identical diameters. We empirically find these initial rate constants to vary as (SWCNT diameter)-4(cos 3θ)-y with y = -1/2 for (GT)5 and -1 for (GT)6. In addition, the full displacement kinetic traces are well fitted by double exponential kinetics, with rate constants and amplitudes dependent on SWCNT diameter. A two-step kinetic model for the displacement process will be presented to account for these findings.

Recording of Low-Oxygen Stress Response Using Chlorophyll Fluorescence Kinetics in Apple Fruit

AbstractLong-term storage of apples (Malus x domestica, Borkh.) is increasingly taking place under Dynamic Controlled Atmosphere (DCA). The oxygen level is lowered to ≤ 1 kPa O2 and the apples are stored just above the Lower Oxygen Limit (LOL). Low oxygen stress during controlled atmosphere storage can lead to fermentation in apples if oxygen levels are too low. Chlorophyll fluorescence can be used to detect low-oxygen stress at an early stage during storage. The currently available non-imaging fluorescence systems often use the minimal fluorescence (Fo) parameter. In contrast, the use of chlorophyll fluorescence kinetics is insufficiently described. Therefore, this study aimed to gain more knowledge about the response of chlorophyll fluorescence kinetics to low oxygen stress in apples using a fluorescence imaging system. The results show that the kinetic fluorescence curves differ under aerobic and fermentation conditions. The fermentative conditions initiated a decrease in fluorescence intensity upon application of the saturation pulses during exposure to actinic light. This result was made at 18 °C and 2 °C ambient temperatures. Interestingly, the kinetic curve changed at 2 °C before fermentation products accumulated in the apples. Non-photochemical quenching (NPQ) decreased under fermentation conditions in the dark phase after relaxation. Upon entering the dark relaxation phase after Kautsky induction, ɸPSII began to increase. Under atmospheric oxygen conditions, ɸPSII reached values of 0.81 to 0.76, while under fermentation, ɸPSII values ranged from 0.57 to 0.44.

Exploring the pH-Responsive Interaction of β-Blocker Drug Propranolol with Biomimetic Micellar Media: Fluorescence and Electronic Absorption Studies.

Interaction of neutral and charged lipophilic beta-blocker drug, propranolol (PPL) with biomimicking nanocavities formed by micelles bearing same and opposite charges namely, cationic cetyltrimethylammonium bromide (CTAB), a surface-active ionic liquid 1-hexadecyl-3-methylimidazolium chloride (HDMIC) and anionic sodium dodecyl sulphate (SDS) have been investigated using fluorescence and absorption spectroscopic techniques. Binding of PPL to SDS at pH < pKa is characterised by biphasic interactions with decrease in fluorescence intensity at lower concentrations and subsequent increase post micellization. All the surfactants show significant interactions with the neutral drug molecule at pH > pKa, which is evident from the strongest binding constant ( ) values at pH 10.4. Results of quenching studies indicate that the location of drug molecule is determined by its charge, which is influenced by both pH and charge on micelle surface. For PPL-CTAB and PPL-HDMIC systems, quenching was strongest at pH 10.4, moderate at pH 7.4 and was absent at pH 3.5. However, the PPL-SDS system displayed similar values at all pH conditions, suggesting that the probe is at the same position regardless of pH. Non-covalent interactions, which play crucial role in biological systems, are similarly the primary driving force governing the interaction between PPL and surfactant micelles.

Comparison of proanthocyanidins A2 and B2 on IgE-reactivity and epitopes in Gly m 6 using multispectral, LC/MS-MS and molecular docking

This study comparatively analyzed the changes in IgE-reactivity and epitopes in proanthocyanidins A2- (PA-Gly m 6) and B2-Gly m 6 (PB-Gly m 6) conjugates prepared by alkali treatment at 80 °C for 20 min. Similar to the western blot, ELISA also showed a higher reduced IgE-reactivity in PA-Gly m 6 (70.12 %) than PB-Gly m 6 (63.17 %). SDS-PAGE demonstrated that proanthocyanidins A2 caused more formation of >180 kDa polymers than proanthocyanidins B2. Multispectral analyses revealed that PA-Gly m 6 exhibited more structural alteration (e.g., a decrease of α-helical content and ANS fluorescence intensity) to unfold protein structure than proanthocyanidins B2, improving the accessibility to modify Gly m 6 for shielding or destroying conformational epitopes. LC/MS-MS revealed that PA-Gly m 6 conjugates had a lower abundance of allergens, peptides and linear epitopes than PB-Gly m 6 conjugates. Molecular docking showed that proanthocyanidins A2 and B2 reacted with Gln-317 and Asn-94 of epitopes, respectively. Overall, proanthocyanidins A2 is more effective than proanthocyanidins B2 to decrease the IgE-reactivity of Gly m 6 due to more shielding or destruction of conformational epitopes and lower content allergens and linear epitopes, which was attributed to more protein-crosslinks formation and structural changes in PA-Gly m 6 conjugates.

Plant-Based, Hydrogel-like Microfibers as an Antioxidant Platform for Skin Burn Healing.

Natural polymers from organic wastes have gained increasing attention in the biomedical field as resourceful second raw materials for the design of biomedical devices which can perform a specific bioactive function and eventually degrade without liberating toxic residues in the surroundings. In this context, patches and bandages, that need to support the skin wound healing process for a short amount of time to be then discarded, certainly constitute good candidates in our quest for a more environmentally friendly management. Here, we propose a plant-based microfibrous scaffold, loaded with vitamin C (VitC), a bioactive molecule which acts as a protecting agent against UV damages and as a wound healing promoter. Fibers were fabricated via electrospinning from various zein/pectin formulations, and subsequently cross-linked in the presence of Ca2+ to confer them a hydrogel-like behavior, which we exploited to tune both the drug release profile and the scaffold degradation. A comprehensive characterization of the physico-chemical properties of the zein/pectin/VitC scaffolds, either pristine or cross-linked, has been carried out, together with the bioactivity assessment with two representative skin cell populations (human dermal fibroblast cells and skin keratinocytes, HaCaT cells). Interestingly, col-1a gene expression of dermal fibroblasts increased after 3 days of growth in the presence of the microfiber extraction media, indicating that the released VitC was able to stimulate collagen mRNA production overtime. Antioxidant activity was analyzed on HaCaT cells via DCFH-DA assay, highlighting a fluorescence intensity decrease proportional to the amount of loaded VitC (down to 50 and 30%), confirming the protective effect of the matrices against oxidative stress. Finally, the most performing samples were selected for the in vivo test on a skin UVB-burn mouse model, where our constructs demonstrated to significantly reduce the inflammatory cytokines expression in the injured area (50% lower than the control), thus constituting a promising, environmentally sustainable alternative to skin patches.

Engineering a simple multisignal-output probe for measuring residual peroxymonosulfate in advanced oxidation reactions

The extensive applications of peroxymonosulfate (PMS) in the field of environmental pollutant treatment based on advanced oxidation processes (AOPs) have prompted a high demand for advances in the probe ranging from improving their performances to strengthening their practicalities. Here, a multisignal-output probe of PMS was achieved by the unconventional application of traditional chromogenic system, 3,3′,5,5′-tetramethylbenzidine with Co2+ ions (Co2+-TMB). It works on the trace Co2+-catalyzed specific conversion of a colorless TMB into a blue oxidation product (oxTMB) with PMS as the oxidizing agent, accompanied by the enhanced absorption value of oxTMB at 652 nm and decreased fluorescence intensity of TMB at 405 nm. The change of color was directly observed. The combination of a hydrogel with a colorimetric platform favors the real-time and convenient sensing of PMS in the concentration range of 0.98 to 130.29 μM. A good linear relationship between the PMS concentration and both the absorption and fluorescence intensity was obtained with an r2 value of 0.999, and a detection limit of 0.03 μM for fluorescence and 0.11 μM for spectrometry. Such a multisignal output probe with the advantages of simplicity, convenience, high sensitivity and stability improves the reliability and practical adaptability. This study successfully applied a valuable strategy for sensing PMS, and verified its availability in detecting the residual quantity of PMS in pollutant water treated by AOPs and PMS concentrations in actual water samples with peroxydisulfate (PDS).

Fluid property identification of the Lower Cretaceous reservoirs with complex oil-water contacts in Deseo Basin, Chad

Recently, exploration breakthroughs have been made in the Lower Cretaceous sandstone reservoirs in the Doseo Basin, but the identification of reservoir fluid property is difficult due to variable reservoir lithology, complex oil-water contact within and faint responses of the oil zone, which causes the lower accuracy of reservoir fluid property identification with conventional mudlogging and wirelogging techniques. Applying the geochemical logging, fluorescent logging, mud logging and cutting logging technology, in combination with formation test data, this paper distinguishes the crude oil types, analyzes the logging response characteristics of oil zone after water washing, and establishes the interpretation charts and parameter standards for reservoir fluid properties. The crude oil can be divided into two types, namely viscous-heavy and thin-light, based on total hydrocarbon content and component concentration tested by mud logging, features of pyrolysis gas chromatogram and fluorescence spectroscopy. The general characteristics of oil layers experienced water washing include the decrease of total hydrocarbon content and component concentration from mud logging, the decrease of S1 and PS values from geochemical logging, the decrease of hydrocarbon abundance and absence of some light components in pyrolysis gas chromatogram, and the decrease of fluorescence area and intensity from fluorescence logging. According to crude oil types, the cross plots of S1 versus peak-baseline ratio, and the cross plots of rock wettability versus fluorescence area ratio are drawn and used to interpret reservoir fluid property. Meanwhile, the standards of reservoir fluid parameter are established combining with the parameters of PS and the parameters in above charts, and comprehensive multiparameter correlation in both vertical and horizontal ways is also performed to interpret reservoir fluid property. The application in the Doseo Basin achieved great success, improving interpretation ability of fluid property in the reservoir with complex oil-water contact, and also provided technical reference for the efficient exploration and development of similar reservoirs.

Excited-state properties of 6-methoxyflavone in the presence of halide ions in aqueous media

The present work investigated the influence of different halides on the excited state dynamics of 6-methoxyflavone (6MF) in an aqueous solution with steady-state and time-resolved techniques. On successive addition of I− and Br− ions, the fluorescence of 6MF quenched significantly, whereas the respective ions do not change the maximum fluorescence band. Fluorescence of 6MF was quenched 66% by I− ions and 34% by Br− ions. In a pure aqueous medium, both the H-bonded: CT and protonated species of 6MF participate in the quenching of fluorescence. The quenching process was categorized by Stern–Volmer (S–V) and Lehrer equations. Quenching parameters such as KSV, KSV-L and kq were higher for I− ions than Br− ions. The decrease in fluorescence intensity and a reduction in fluorescence lifetime suggested the dynamic nature of quenching by I− ions following the electron transfer mechanism. Fluorescence quenching of 6MF has also been observed in the acidic medium in the presence of different halides. Thus, the study reveals that 6MF is responsive towards I− ions in a wide range of pH, specifically in a purely aqueous environment (pH∼7), hence important for sensing/detection applications.

Spectral-luminescent properties of Zn(II) curcuminates

1,7-bis-(4-hydroxy-3-methoxyphenyl)-1,6-heptadiene-3,5-dione (curcumin, Cur) and mono- and mixed Zn(II) complexes based on it were synthesized using the improved method. It was established that curcumin forms metal chelates of the composition ZnCur22Н2О and Zn(Cur)2Phen with the zinc ion. Coordination of the curcumin ligand with the central atom is bidentate cyclic through the -diketone group, and the ortho-methoxyphenol fragment of Cur does not participate in chelation. The fluorescent properties of all synthesized compounds were studied. It was shown that the complex formation of zinc with curcumin causes an increase in the relative intensity of fluorescence and a shift of the emission band to the long-wave region. This indicates both the complexation process and the sensitizing effect of the zinc ion. When phenatroline is added to the zinc(II) complex, the fluorescence emission maximum undergoes a bathochromic shift compared to the ZnCur2 monoligand complex, and the relative fluorescence intensity decreases by 2.5 times. The shift of the radiation maximum to the region of low energies is due to the coordination of the phenathroline molecule to metal ions; and the decrease in emission is due to the shielding ability of the phenathroline donor molecule in relation to the weaker curcumin donor, which increases the number of non-radiative energy losses caused by its inefficient transfer due to the large energy gap between the triplet levels of the ligands.

Probing the Influence of Novel Organometallic Copper(II) Complexes on Spinach PSII Photochemistry Using OJIP Fluorescence Transient Measurements.

Modern agricultural cultivation relies heavily on genetically modified plants that survive after exposure to herbicides that kill weeds. Despite this biotechnology, there is a growing need for new sustainable, environmentally friendly, and biodegradable herbicides. We developed a novel [CuL2]Br2 complex (L = bis{4H-1,3,5-triazino[2,1-b]benzothiazole-2-amine,4-(2-imidazole) that is active on PSII by inhibiting photosynthetic oxygen evolution on the micromolar level. [CuL2]Br2 reduces the FV of PSII fluorescence. Artificial electron donors do not rescind the effect of [CuL2]Br2. The inhibitory mechanism of [CuL2]Br2 remains unclear. To explore this mechanism, we investigated the effect of [CuL2]Br2 in the presence/absence of the well-studied inhibitor DCMU on PSII-containing membranes by OJIP Chl fluorescence transient measurements. [CuL2]Br2 has two effects on Chl fluorescence transients: (1) a substantial decrease of the Chl fluorescence intensity throughout the entire kinetics, and (2) an auxiliary "diuron-like" effect. The initial decrease dominates and is observed both with and without DCMU. In contrast, the "diuron-like" effect is small and is observed only without DCMU. We propose that [CuL2]Br2 has two binding sites for PSII with different affinities. At the high-affinity site, [CuL2]Br2 produces effects similar to PSII reaction center inhibition, while at the low-affinity site, [CuL2]Br2 produces effects identical to those of DCMU. These results are compared with other PSII-specific classes of herbicides.

Highly selective ratiometric fluorescent sensing of fleroxacin via functionalized Zr metal–organic frameworks

The fluoroquinolone antibacterial agent fleroxacin (FLO) has been widely used for the treatment of urinary infections. Quantitatively analyzing the amount of FLO is vital for human health and the ecological system, but still proves challenging due to the complex environmental interference. In this work a ratiometric fluorescence sensor MOF-808-TPY is successfully constructed by incorporating a functional ligand, 2,2′:6′,2′'-terpyridine-4′-carboxylic acid (TPY), to the zirconium node of MOF-808 via post-synthetic modification. With the addition of fleroxacin, the prepared MOF-808-TPY sensor exhibits decreased fluorescence intensity at 370 nm, while the intrinsic fluorescence from fleroxacin at 440 nm is greatly enhanced. The yielded ratiometric response can effectively eliminate interference from environmental factors, and is able to discriminate FLO from other fluoroquinolone antibiotics efficiently, demonstrating high selectivity towards FLO analysis. A linear relationship of the fluorescence ratio F370/F440 against the concentration of FLO is observed in the range of 0 ∼ 13.50 μM with the detection of limit down to 0.01 μM. Excellent recoveries of FLO levels in real water samples for practical application are also achieved. Additionally, MOF-808-TPY could be easily integrated onto nanofibers for FLO sensing in aspect of potential sensing device. This work represents a promising strategy for constructing MOFs-based ratiometric sensors in monitoring fluorescent antibiotics.

Probing the interaction of uranyl(VI) complex with bovine serum albumin via in-depth experimental and computational perspectives

Interaction aspects of uranyl(VI) complexes as well as the coordinated ONNO-donor ligand with bovine serum albumin (BSA) were investigated by the fluorescence spectroscopy and computational insights. Under optimal physiological condition, it was observed that there was significant decrease in fluorescence intensity of BSA upon interaction with uranyl(VI) complexes as well as the ligand. The mechanism of interaction between the uranyl(VI) complex and BSA protein was examined by fluorescence measurement. The Stern-Volmer constant, binding affinity, binding constant, standard free energy, and fluorescence lifetime decay profile of BSA in the absence as well as in the presence of uranyl(VI) complex were determined. Furthermore, the conformational binding of uranyl(VI) complexes with BSA protein was explored via molecular docking studies, and confirmed that there is a strong affinity between the Trp-213 residue in the binding pocket of sub-domain IIA and uranyl(VI) complex.

Physicochemical properties of soybean protein isolate-based gel produced through probiotic fermentation

Soy protein isolate (SPI) was used to prepare gels through probiotic fermentation. The effects of fermentation time (0–20 h) on the physicochemical properties of resulting gel were evaluated. The effect of probiotic fermentation on physicochemical properties of gel was found to highly depend on the fermentation time. The probiotic fermentation decreased the pH value below pH 4.75 and this process also induced SPI to form a gel upon 10 h. The formation of gel was indicated by the increase of particle size, viscosity and storage modulus, and appearance of a new peak in molecular weight distribution. The formation of porous and gel-like microstructure, due to the aggregation of SPI molecules, also occurred after 10 h of fermentation. Water holding capacity of SPI-based gel reached the highest value at 15 h fermentation and decreased with further fermentation. The probiotic fermentation caused an increase of band intensity of amide-A in FTIR spectra. It also caused a decrease of surface hydrophobicity and fluorescence intensity in intrinsic tryptophan fluorescence spectra. The subunits of SPI remained intact and were not affected by probiotic fermentation.

The organic osmolyte betaine effectively counteracts the deleterious effect of diclofenac on protein structure and stability

Understanding the physicochemical properties of pharmacy and the concept of pharmacophore is essential to devise guidelines for the synthesis of target-oriented drugs. In the present study, thermal denaturation, circular dichroism, intrinsic fluorescence, and docking were employed for studying the effects of the non-steroidal anti-inflammatory drug, diclofenac sodium, on the stability and structure of bovine pancreatic ribonuclease (RNase A) taken as a model of an enzyme. Since drug-protein interaction is an important pharmacokinetic parameter of a drug, it was deemed significant to study the effects of diclofenac on protein structure and stability. When the thermodynamic parameters were assessed, it was shown that RNase-A was destabilized in the presence of diclofenac sodium in terms of Tm and ΔGD°, while the addition of osmolytes stabilized the protein. In the presence of diclofenac sodium and osmolyte, there was a change in a tertiary structure of the protein but not in its secondary structure. Spectral results revealed a decrease in fluorescence intensity confirming fluorescence quenching of RNase-A by diclofenac sodium and osmolytes. Molecular docking analysis suggested that hydrogen bonds and Van der Waals are involved in the binding of RNase-A to diclofenac sodium. The RNAse-A activity is decreased in the presence of diclofenac sodium while osmolyte can restore the RNase-A activity and the indices kcat increase and Km values decrease. This study presents new combination of drug therapy comprising diclofenac sodium and osmolytes to reduce the risk of adverse effects of diclofenac sodium.

Influence of laser radiation of a surgical laser on the structure of bovine serum albumin molecules in vitro

The influence of laser radiation of a surgical laser on the physicochemical properties of bovine serum albumin molecules was studied. After exposure to laser radiation, the optical density of protein solutions increases, the fluorescence intensity decreases, a significant decrease of the intensity of the a-helix band on the Raman spectrum is observed and the refractive index of protein solution did not significantly change. However, the viscosity increased, and the pseudoplasticity of aqueous solutions of albumin decreased. There was no massive damage to the protein polypeptide chain, on the contrary, intensive aggregation was observed. Thus, in a bovine serum albumin solution subjected to contact action of laser radiation, the processes of partial denaturation and aggregation prevail, aromatic amino acid residues of the protein are damaged to a lesser extent, and fragmentation of albumin molecules is not observed.