- Coumarin Derived "Turn on" Fluorescent Sensor for Selective Detection of Cadmium (II) Ion: Spectroscopic Studies and Validation of Sensing Mechanism by DFT Calculations. [Journal Article]
- JFJ Fluoresc 2019 Jul 20
- A novel coumarin based Schiff base sensor probe 1, was synthesized and structural elucidation was carried out by FTIR, UV-vis, 1H and 13C NMR and MS spectroscopy. The optical properties of the sensor…
A novel coumarin based Schiff base sensor probe 1, was synthesized and structural elucidation was carried out by FTIR, UV-vis, 1H and 13C NMR and MS spectroscopy. The optical properties of the sensor probe were investigated by employing absorption and fluorescence titrations which showed specific recognition behaviour being highly selective towards Cd2+ over the other 3d transition metal ions. The strong fluorometric response of probe 1 towards Cd2+ ion is attributed to inhibition of C=N isomerization effect upon coordination of the metal ion. The binding stoichiometry was determined by Job's plot and the probable sensing mechanism of the probe towards Cd2+ was investigated by employing FTIR spectra analysis and 1H NMR titration experiments. Computational validation of the sensing mechanism in various modes towards Cd2+ was also performed by carrying out the DFT studies which were found to be in good concordance with the experimental results. The reversible nature of the probe was studied by EDTA titration indicating that it can be reused. Interaction studies of the sensor probe with the BSA showed the practical applicability for the quantitative determination of Cd2+ concentration in the blood plasma. The lower detection limit of the probe upto 0.114 μM further proves its practical application in the sensing phenomenon.
- Inactivation of Alpha-2-Macroglobulin by Photo-Illuminated Gallic Acid. [Journal Article]
- JFJ Fluoresc 2019 Jul 20
- Gallic acid is a naturally occurring plant polyphenol found in green tea and various fruits. Under certain conditions gallic acid exhibits pro-oxidant characteristics rather than its well known antio…
Gallic acid is a naturally occurring plant polyphenol found in green tea and various fruits. Under certain conditions gallic acid exhibits pro-oxidant characteristics rather than its well known antioxidant property. In the present work, we explored the interaction of gallic acid with sheep alpha-2-macroglobulin (α2M) in the presence of light and determined the functional alteration and conformational modifications induced in α2M structure. α2M is a highly abundant homotetrameric antiproteinase glycoprotein having diverse functions. Our result suggests α2M loses almost 54% of its proteinase inhibitory activity after 2 h incubation with gallic acid in presence of light. The inactivation of α2M was due to photodynamic generation of superoxide radical and hydrogen peroxide by gallic acid. The UV/visible absorption spectra of α2M showed increase in absorbance due to complex formation with gallic acid. Intrinsic fluorescence study shows that α2M-gallic acid interaction leads to quenching of fluorescence intensity of α2M and the mechanism of quenching is found to be static in nature. Synchronous fluorescence measurements reveal that gallic acid interaction leads to change in the microenvironment around tryptophan residues of α2M. Moreover, Fourier transform infrared spectroscopy and circular dichroism spectra suggests perturbation in secondary structure of α2M. Binding parameters were investigated by spectroscopic as well as calorimetric measurements. Negative value of enthalpy change and Gibbs free energy confirms the binding process to be exothermic and spontaneous.
- An assessment of bioavailability of acrylate based pH-sensitive complexes of lovastatin. [Journal Article]
- PJPak J Pharm Sci 2019; 32(3 (Supplementary)):1129-1136
- Lovastatin (LSN), a potent anti-hyperlipidemic drug, possesses poor bioavailability due to its very low aqueous solubility. The objective of this study was to establish a relationship between increas…
Lovastatin (LSN), a potent anti-hyperlipidemic drug, possesses poor bioavailability due to its very low aqueous solubility. The objective of this study was to establish a relationship between increased drug solubility before reaching site of absorption or increasing drug solubility at target absorption site for accentuated bioavailability of LSN. Composites of LSN with oppositely natured pH-sensitive acrylate polymers, cationic Eudragit EPO (EPO) and anionic Eudragit L100 (L100), were fabricated with physical trituration and kneading methods. Formulations were characterized for solubility, FTIR, PXRD, DSC, SEM, dissolution and bioavailability studies in rats. Interestingly, we observed that physical mixtures of EPO outmatched its kneaded formulations, whereas the physical mixtures and kneaded dispersions of L100 were virtually similar in characteristics. EPO was superior in boosting LSN solubility in the respective medium than the L100. Moreover, EPO produced immediate release profile in gastric environment whereas L100 offered sustained release of LSN in intestinal milieu. Bioavailability studies in rats further supported the EPO formulation in terms of shorter Tmax, higher Cmax and heightened AUC.
- Photoelectrochemical biosensor for 5hmC detection based on the photocurrent inhibition effect of ZnO on MoS2/C3N4 heterojunction. [Journal Article]
- BBBiosens Bioelectron 2019 Jul 16; 142:111516
- A novel photoelectrochemical biosensor was fabricated for 5-hydroxymethylcytosine (5hmC) detection based on the photocurrent inhibition effect of ZnO on MoS2/C3N4 heterojunction. Firstly, the ITO ele…
A novel photoelectrochemical biosensor was fabricated for 5-hydroxymethylcytosine (5hmC) detection based on the photocurrent inhibition effect of ZnO on MoS2/C3N4 heterojunction. Firstly, the ITO electrode was modified successively with MoS2 and g-C3N4 as photoelectric materials to deliver a strong photocurrent response. Next, the 5-hydroxymethyl group (-CH2OH) of 5hmC was oxidized by KRuO4 to produce an aldehyde group (-CHO), where 5hmC was converted into 5-formylcytosine (5fC). Based on the covalent reaction with between -CHO of 5fC and -NH2 groups of g-C3N4, 5fC can be captured on electrode surface. Finally, the ZnO-PAMAM composite was covalently attached to the phosphate group of the immobilized 5fC, which could decrease the electron transfer amount of g-C3N4 to MoS2, absorption of light and consumption of electron donors thereby resulting the decrease of photocurrent. Under optimal conditions, the photocurrent shows a linear relationship with the logarithm value of 5hmC concentration from 0.01-200 nM with a low detection limit of 2.6 pM. Moreover, this method was selective and allowed to discriminate between 5hmC and 5-methylcytosine (5mC) in DNA. Finally, the photoelectrochemical biosensor was successfully applied to investigate the effect of heavy metal ion and phytohormones on 5hmC expression in rice seedlings leaves.
- Cyanine dyes with tail length asymmetry enhance photoselection: A multiscale study on DiD probes in a liquid disordered membrane. [Journal Article]
- SASpectrochim Acta A Mol Biomol Spectrosc 2019 Jul 05; 224:117329
- Visualization of membrane domains like lipid rafts in natural or artificial membranes is a crucial task for cell biology. For this purpose, fluorescence microscopy is often used. Since fluorescing pr…
Visualization of membrane domains like lipid rafts in natural or artificial membranes is a crucial task for cell biology. For this purpose, fluorescence microscopy is often used. Since fluorescing probes in lipid membranes partition specifically in e.g. local liquid disordered or liquid ordered environments, the consequent changes in their orientation and location are both theoretically and experimentally of interest. Here we focused on a liquid disordered membrane phase and performed molecular dynamics (MD) simulations of the indocarbocyanine DiD probes by varying the length of the attached alkyl tails and also the length of the cyanine backbone. From the probed compounds in a DOPC lipid bilayer at ambient temperature, a varying orientation of the transition dipole moment was observed, which is crucial for fluorescence microscopy and which, through photoselection, was found to be surprisingly more effective for asymmetric probes than for the symmetric ones. Furthermore, we observed that the orientation of the probes was dependent on the tail length; with the methyls or propyls attached, DiD oriented with its tails facing the water, contrary to the ones with longer tails. With advanced hybrid QM/MM calculations we show that the different local environment for differently oriented probes affected the one-photon absorption spectra, that was blue-shifted for the short-tailed DiD with respect to the DiDs with longer tails. We show here that the presented probes can be successfully used for fluorescence microscopy and we believe that the described properties bring further insight for the experimental use of these probes.
- Boosted photocatalytic decomposition of nocuous organic gases over tricomposites of N-doped carbon quantum dots, ZnFe2O4, and BiOBr with different junctions. [Journal Article]
- JHJ Hazard Mater 2019 Jul 06; 380:120866
- Herein, the effect of material structure on photocatalytic activity in the decomposition of nocuous organic gases (1,3,5-trimethylbenzene (TMB) and o-xylene (XYL)) was investigated by synthesizing tr…
Herein, the effect of material structure on photocatalytic activity in the decomposition of nocuous organic gases (1,3,5-trimethylbenzene (TMB) and o-xylene (XYL)) was investigated by synthesizing tricomposite photocatalysts of N-doped carbon quantum dots, ZnFe2O4, and BiOBr (NCQDs/ZFO/BOB) with different junctions. The NCQDs/ZFO/BOB material (NCQDs/ZFO/BOB1) synthesized using a one-pot method revealed the highest photocatalytic efficiency. The NCQDs in NCQDs/ZFO/BOB1 exhibited photoluminescence property that expanded the photo-absorption nature and acted as a mediator to enhance the Z-scheme charge transfer between ZFO and BOB. The photocatalytic activity exhibited by NCQDs/ZFO/BOB1 was higher than that exhibited by the selected reference materials (CQDs/ZFO/BOB, NCQDs/BOB, ZFO/BOB, BOB, NCQDs/ZFO, and ZFO). Results showed that the decomposition efficiencies of TMB and XYL in the presence of NCQDs/ZFO/BOB1 under specified operational conditions were 94.5% and 72.5%, respectively. Moreover, the synthesized NCQDs/ZFO/BOB photocatalysts displayed excellent stability. Herein, the conversion ratios of TMB and XYL into CO2 with NCQDs/ZFO/BOB1 and the intermediates formed during photocatalysis were assessed. Furthermore, a potential mechanism for the NCQDs/ZFO/BOB1-catalyzed organic gas decomposition was proposed. The hybridization access introduced herein thus provides a method for the intelligent synthesis of a new type of multicomponent nanocomposites for environmental remediation.
- Percutaneous penetration of drugs applied in transdermal delivery systems: An in vivo based approach for evaluating computer generated penetration models. [Journal Article]
- RTRegul Toxicol Pharmacol 2019 Jul 18; :104428
- Human skin is a viable pathway for administration of therapeutics. Transdermal delivery systems (TDS) have been approved by the US-FDA since 1981. To enable the risk assessment of dermal exposure, pr…
Human skin is a viable pathway for administration of therapeutics. Transdermal delivery systems (TDS) have been approved by the US-FDA since 1981. To enable the risk assessment of dermal exposure, predictive mathematical models are used. In this work the accuracy of predicted flux of the models is compared to experimental human in vivo data of drugs applied in US-FDA approved TDS. A database of pharmacokinetic data of drugs applied in TDS was used and updated. Three mathematical models (QSAR) were used to calculate predicted fluxes, and compared to the human in vivo data. For more than half of the drugs applied in TDS, the predicted flux by the mathematical models was an underestimation compared to the flux calculated with the experimental in vivo data. The flux was over- or underestimated by a factor 10-100. All mathematical models were significantly correlated with the experimental in vivo data. The process of percutaneous penetration has several influencing factors, TDS minimize some of these factors. Limitations are discussed. Further research is needed, with a focus on validation and standardization of the permeability coefficient. This work offers observations that should give a stimulus for refinement on the appropriate usage and limitations of mathematical models.
- The Hydration Shell of Monomeric and Dimeric Insulin Studied by Terahertz Time-Domain Spectroscopy. [Journal Article]
- BJBiophys J 2019 Jul 03
- Protein aggregation is believed to be a significant biological mechanism related to neurodegenerative disease, which makes the early-stage detection of aggregates a major concern. We demonstrated the…
Protein aggregation is believed to be a significant biological mechanism related to neurodegenerative disease, which makes the early-stage detection of aggregates a major concern. We demonstrated the use of terahertz (THz) time-domain spectroscopy to study protein-water interaction of monomeric and dimeric bovine insulin in aqueous samples. Regulated by changing pH and verified by size-exclusion chromatography and dynamic light scattering, we then measured their concentration-dependent changes in THz absorption between 0.5 and 3.0 THz and quantitatively deduced the extended hydration shell thickness by cubic distribution model and random distribution model. Under a random distribution assumption, the extended hydration thickness is 15.4 ± 0.4 Å for monomeric insulin and 17.5 ± 0.5 Å for dimeric insulin, with the hydration number of 6700 and 11,000, respectively. The hydration number of dimeric insulin is not twice but 1.64 times that of monomeric insulin, further supported by the ratio of solvent-accessible surface area. This "1.64-times" relation probably originates from the structural and conformational changes accompanied with dimerization. Combined with the investigations on insulin samples with different single amino acid mutations, residue B24 is believed to play an important role in the dimerization process. It is demonstrated that THz time-domain spectroscopy is a useful tool and has the sensitivity to provide the hydration information of different protein aggregates at an early stage.
- Influence of chirality on fluorescence and resonance energy transfer. [Journal Article]
- JCJ Chem Phys 2019 Jul 21; 151(3):034305
- Electronically excited molecules frequently exhibit two distinctive decay mechanisms that rapidly generate optical emission: one is direct fluorescence and the other is energy transfer to a neighbori…
Electronically excited molecules frequently exhibit two distinctive decay mechanisms that rapidly generate optical emission: one is direct fluorescence and the other is energy transfer to a neighboring component. In the latter, the process leading to the ensuing "indirect" fluorescence is known as FRET, or fluorescence resonance energy transfer. For chiral molecules, both fluorescence and FRET exhibit discriminatory behavior with respect to optical and material handedness. While chiral effects such as circular dichroism are well known, as too is chiral discrimination for FRET in isolation, this article presents a study on a stepwise mechanism that involves both. Chirally sensitive processes follow excitation through the absorption of circularly polarized light and are manifest in either direct or indirect fluorescence. Following recent studies setting down the symmetry principles, this analysis provides a rigorous, quantum outlook that complements and expands on these works. Circumventing expressions that contain complicated tensorial components, our results are amenable for determining representative numerical values for the relative importance of the various coupling processes. We discover that circular dichroism exerts a major influence on both fluorescence and FRET, and resolving the engagement of chirality in each component reveals the distinct roles of absorption and emission by, and between, donor and acceptor pairs. It emerges that chiral discrimination in the FRET stage is not, as might have been expected, the main arbiter in the stepwise mechanism. In the concluding discussion on various concepts, attention is focused on the validity of helicity transfer in FRET.
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- Orientational relaxation of a quantum linear rotor in a dissipative environment: Simulations with the hierarchical equations-of-motion method. [Journal Article]
- JCJ Chem Phys 2019 Jul 21; 151(3):034101
- We study the effect of a dissipative environment on the orientational relaxation of a three-dimensional quantum linear rotor. We provide a derivation of the Hamiltonian of a linear rotor coupled to a…
We study the effect of a dissipative environment on the orientational relaxation of a three-dimensional quantum linear rotor. We provide a derivation of the Hamiltonian of a linear rotor coupled to a harmonic bath from first principles, confirming earlier conjectures. The dynamics generated by this Hamiltonian is investigated by the hierarchical equations-of-motion method assuming a Drude spectral density of the bath. We perform numerically accurate simulations and analyze the behavior of orientational correlation functions and the rotational structures of infrared absorption and Raman scattering spectra. We explore the features of orientational correlation functions and their spectra for a wide range of system-bath couplings, bath memory times, and temperatures. We discuss the signatures of the orientational relaxation in the underdamped regime, the strongly damped regime, and the librational regime. We show that the behavior of orientational correlation functions and their spectra can conveniently be analyzed in terms of three characteristic times, which are explicitly expressed in terms of the parameters of the Hamiltonian.