Fluorescence Technique Research Articles

Performance of the silica adsorbent from snake fruit peel for removing heavy metals of Ag, Cu, Mn, and Cr in SCW

Silver crafts wastewater (SCW) typically contains environmentally harmful heavy metals, including Ag, Cu, Mn, and Cr, necessitating treatment before disposal. This study explores a promising solution using silica (SiO2) adsorbents derived from snake fruit peel through acidic activation with HCl concentrations of 2, 4, and 6 M. Qualitative analysis of the adsorbent involved Fourier-transform infrared spectrometer (FTIR) and x-ray fluorescence (XRF) techniques. XRF analysis revealed major compositions of Si (26%) and Cl (71.46%), with minor elements such as Ca (0.91%), P (0.42%), K (0.37%), Fe (0.12%), and others. FTIR analysis indicated the presence of siloxane (Si-O-Si) and silanol (Si-OH) on the adsorbent. The SiO2 adsorbent demonstrated effectiveness in removing heavy metals (Ag, Cu, Mn, and Cr) from SCW, achieving removal percentages of approximately 16.96%, 24.38%, 19.34%, and 9.82%, respectively. This research contributes to the development of an environmentally friendly approach for SCW treatment using silica adsorbents derived from agricultural waste.

Formamide denaturation of double-stranded DNA for fluorescence in situ hybridization (FISH) distorts nanoscale chromatin structure.

As imaging techniques rapidly evolve to probe nanoscale genome organization at higher resolution, it is critical to consider how the reagents and procedures involved in sample preparation affect chromatin at the relevant length scales. Here, we investigate the effects of fluorescent labeling of DNA sequences within chromatin using the gold standard technique of three-dimensional fluorescence in situ hybridization (3D FISH). The chemical reagents involved in the 3D FISH protocol, specifically formamide, cause significant alterations to the sub-200 nm (sub-Mbp) chromatin structure. Alternatively, two labeling methods that do not rely on formamide denaturation, resolution after single-strand exonuclease resection (RASER)-FISH and clustered regularly interspaced short palindromic repeats (CRISPR)-Sirius, had minimal impact on the three-dimensional organization of chromatin. We present a polymer physics-based analysis of these protocols with guidelines for their interpretation when assessing chromatin structure using currently available techniques.

Using Förster Resonance Energy Transfer (FRET) to Understand the Ubiquitination Landscape.

Förster resonance energy transfer (FRET) is a fluorescence technique that allows quantitative measurement of protein interactions, kinetics and dynamics. This review covers the use of FRET to study the structures and mechanisms of ubiquitination and related proteins. We survey FRET assays that have been developed where donor and acceptor fluorophores are placed on E1, E2 or E3 enzymes and ubiquitin (Ub) to monitor steady-state and real-time transfer of Ub through the ubiquitination cascade. Specialized FRET probes placed on Ub and Ub-like proteins have been developed to monitor Ub removal by deubiquitinating enzymes (DUBs) that result in a loss of a FRET signal upon cleavage of the FRET probes. FRET has also been used to understand conformational changes in large complexes such as multimeric E3 ligases and the proteasome, frequently using sophisticated single molecule methods. Overall, FRET is a powerful tool to help unravel the intricacies of the complex ubiquitination system.

A non-spherical nanoparticles system for the delivery of peptides using polymer grafted nanocellulose

AbstractPeptide drugs are increasingly used to treat a variety of diseases ranging from cancer, and infections to cardiovascular diseases. However, peptides can suffer from low stability in the bloodstream. Entrapment of peptides into nano-sized carriers of various types has widely been explored, but all of them have spherical shapes. Nanocellulose can in contrast serve as a non-spherical nanoparticle with a high aspect ratio. After the isolation of nanocellulose by TEMPO-mediated oxidation, the material needs to be modified with polymers to generate nanoparticles with high water-solubility that can also favourably interact with peptide drugs. We have here chosen insulin as the model drug, which can strongly interact with cationic polymers. As it is known that cationic polymer may retain charged drugs too tightly, we have selected poly(2-(dimethylamino)ethyl acrylate) PDMAEA as a degradable polymer that undergoes self-hydrolysis to poly(acrylic acid) in water. This polymer was compared to poly(N-(3-(dimethylamino)propyl) acrylamide) PDMAPAA, which is a stable cationic polymer. The cationic polymer was co-grafted with poly(2-hydroxyethyl acrylate) PHEA as a water-soluble neutral polymer using the three-component Passerini reaction. A combination of fluorescence and UV-Vis techniques were used to quantify the amount of polymer that was conjugated to the surface. The polymer-coated nanocellulose was labelled with the fluorescent cyanine dye Cy5 while insulin was labelled with Cy3 creating a FRET system that allows monitoring of the interaction between insulin and polymer in cell growth media. We observed that despite the self-hydrolysis of PDMAEA into a negatively charged polymer, the negatively charged insulin was not released in buffer solution according to the FRET studies. Only the addition of serum-supplemented cell growth media led to insulin release. The limited release was explained with the fact that insulin, as well as other peptides, have a mixture of negative and positive charges, with the pH value and the isoelectric point determining the balance between both. Negative-charged polymers can therefore still interact favourably with negatively charged peptides by interacting with cationic amino acids. Graphical Abstract

Label-Free Interference Imaging of Intracellular Trafficking.

ConspectusIntracellular cargo trafficking is a highly regulated process responsible for transporting vital cellular components to their designated destinations. This intricate journey has been a central focus of cellular biology for many years. Early investigations leaned heavily on biochemical and genetic approaches, offering valuable insight into molecular mechanisms of cellular trafficking. However, while informative, these methods lack the capacity to capture the dynamic nature of intracellular trafficking. The advent of fluorescent protein tagging techniques transformed our ability to monitor the complete lifecycle of intracellular cargos, advancing our understanding. Yet, a central question remains: How do these cargos manage to navigate through traffic challenges, such as congestion, within the crowded cellular environment? Fluorescence-based imaging, though valuable, has inherent limitations when it comes to addressing the aforementioned question. It is prone to photobleaching, making long-term live-cell imaging challenging. Furthermore, they render unlabeled cellular constituents invisible, thereby missing critical environmental information. Notably, the unlabeled majority likely exerts a significant influence on the observed behavior of labeled molecules. These considerations underscore the necessity of developing complementary label-free imaging methods to overcome the limitations of fluorescence imaging or to integrate them synergistically.In this Account, we outline how label-free interference-based imaging has the potential to revolutionize the study of intracellular traffic by offering unprecedented levels of detail. We begin with a brief introduction to our previous findings in live-cell research enabled by interferometric scattering (iSCAT) microscopy, showcasing its aptitude and adeptness in elucidating intricate nanoscale intracellular structures. As we delved deeper into our exploration, we succeeded in the label-free visualization of the entire lifespan of nanoscale protein complexes known as nascent adhesions (NAs) and the dynamic events associated with adhesions within living cells. Our continuous efforts have led to the development of Dynamic Scattering-particle Localization Interference Microscopy (DySLIM), a generalized concept of cargo-localization iSCAT (CL-iSCAT). This label-free, high-speed imaging method, armed with iSCAT detection sensitivity, empowers us to capture quantitative and biophysical insights into cargo transport, providing a realistic view of the intricate nanoscale logistics occurring within living cells. Our in vivo studies demonstrate that intracellular cargos regularly contend with substantial traffic within the crowded cellular environment. Simultaneously, they employ inherent strategies for efficient cargo transport, such as collective migration and hitchhiking, to enhance overall transport rates─intriguingly paralleling the principle and practice of urban traffic management. We also highlight the synergistic benefits of combining DySLIM with chemical-selective fluorescent methods. This Account concludes with a "Conclusions and Outlook" section, outlining promising directions for future research and developments, with a particular emphasis on the functional application of iSCAT live-cell imaging. We aim to inspire further investigation into the efficient transport strategies employed by cells to surmount transportation challenges, shedding light on their significance in cellular phenomena.

Portable x-ray fluorescence for bone lead measurement: Current approaches and future directions.

Legacy lead exposures persist as a widespread problem. Blood lead is traditionally used for lead exposure surveillance; however, bone lead proves to be a cheaper, more accessible, and more revealing tool for surveillance that can be measured using portable x-ray fluorescence techniques. We outline how this approach excels for bone lead measurements. Portable XRF offers quick, non-invasive in vivo quantification of bone lead. Compared to traditional KXRF systems, pXRF is limited to cortical bone but allows for quicker and similar results. Current methodologies of lead exposure need re-evaluation as lead-related disease burden and trends are dependent on both cumulative and acute impacts. We examined the evolution of XRF techniques for measuring bone lead, comparing current methods with previous ones. We assessed their accuracy, identified limitations, and discussed potential advances in future techniques. Legacy lead exposures call for a revitalization of lead surveillance methods, and pXRF measurement of bone lead offers such a solution.

Dissolved black nitrogen: an overlooked active nano-catalyst in the abiotic transformation of chlorophenols by sulfides in the subsurface water

The incomplete combustion of biomass and fossil fuels results in the formation of not only black carbon (BC) but also black nitrogen (BN), the dissolved fractions of which (i.e., DBC and DBN) are important components of dissolved organic matter pool. Relative to DBC, the activity and reactivity of DBN are much less understood. Here, we investigated the catalytic effect of DBN derived from N-enriched biomass in the abiotic transformation of chlorophenols by sulfides. The medium-temperature DBN (450 °C) exhibited 13–144% higher catalytic efficiency than other DBN samples and 9.3 times higher than its DBC counterpart. Both electron paramagnetic resonance spectra and fluorescent probe technique indicated that the attached sulfides contributed to the formation of reactive oxygen species (ROS) as the “primary” radicals by favoring electron transfer from DBN to chemisorbed oxygen, and then the generated ROS reacted with N-oxides in DBN to form reactive nitrogen species (RNS) as the “secondary” radicals. The contribution of RNS to the decay of 2-chlorophenol by DBN450 was up to 72%, much higher than that of ROS and non-radical mechanism. These findings suggest that the catalytic effect of DBN is distinct but no less significant than that of DBC to the abiotic transformation of micropollutants in water/soil systems.Graphical

Parascedosporium putredinis NO1 tailors its secretome for different lignocellulosic substrates.

Parascedosporium putredinis NO1 is a plant biomass-degrading ascomycete with a propensity to target the most recalcitrant components of lignocellulose. Here we applied proteomics and activity-based protein profiling (ABPP) to investigate the ability of P. putredinis NO1 to tailor its secretome for growth on different lignocellulosic substrates. Proteomic analysis of soluble and insoluble culture fractions following the growth of P. putredinis NO1 on six lignocellulosic substrates highlights the adaptability of the response of the P. putredinis NO1 secretome to different substrates. Differences in protein abundance profiles were maintained and observed across substrates after bioinformatic filtering of the data to remove intracellular protein contamination to identify the components of the secretome more accurately. These differences across substrates extended to carbohydrate-active enzymes (CAZymes) at both class and family levels. Investigation of abundant activities in the secretomes for each substrate revealed similar variation but also a high abundance of "unknown" proteins in all conditions investigated. Fluorescence-based and chemical proteomic ABPP of secreted cellulases, xylanases, and β-glucosidases applied to secretomes from multiple growth substrates for the first time confirmed highly adaptive time- and substrate-dependent glycoside hydrolase production by this fungus. P. putredinis NO1 is a promising new candidate for the identification of enzymes suited to the degradation of recalcitrant lignocellulosic feedstocks. The investigation of proteomes from the biomass bound and culture supernatant fractions provides a more complete picture of a fungal lignocellulose-degrading response. An in-depth understanding of this varied response will enhance efforts toward the development of tailored enzyme systems for use in biorefining.IMPORTANCEThe ability of the lignocellulose-degrading fungus Parascedosporium putredinis NO1 to tailor its secreted enzymes to different sources of plant biomass was revealed here. Through a combination of proteomic, bioinformatic, and fluorescent labeling techniques, remarkable variation was demonstrated in the secreted enzyme response for this ascomycete when grown on multiple lignocellulosic substrates. The maintenance of this variation over time when exploring hydrolytic polysaccharide-active enzymes through fluorescent labeling, suggests that this variation results from an actively tailored secretome response based on substrate. Understanding the tailored secretomes of wood-degrading fungi, especially from underexplored and poorly represented families, will be important for the development of effective substrate-tailored treatments for the conversion and valorization of lignocellulose.

Multimodal 2D and 3D microscopic mapping of growth cartilage by computational imaging techniques - a short review including new research.

Being able to image the microstructure of growth cartilage is important for understanding the onset and progression of diseases such as osteochondrosis and osteoarthritis, as well as for developing new treatments and implants. Studies of cartilage using conventional optical brightfield microscopy rely heavily on histological staining, where the added chemicals provide tissue-specific colours. Other microscopy contrast mechanisms include polarization, phase- and scattering contrast, enabling non-stained or "label-free" imaging that significantly simplifies the sample preparation, thereby also reducing the risk of artefacts. Traditional high-performance microscopes tend to be both bulky and expensive. Computational imaging denotes a range of techniques where computers with dedicated algorithms are used as an integral part of the image formation process. Computational imaging offers many advantages like 3D measurements, aberration correction and quantitative phase contrast, often combined with comparably cheap and compact hardware. X-ray microscopy is also progressing rapidly, in certain ways trailing the development of optical microscopy. In this study, we first briefly review the structures of growth cartilage and relevant microscopy characterization techniques with an emphasis on FPM and advanced X-ray microscopies. We next demonstrate with our own results computational imaging through Fourier ptychographic microscopy (FPM) and compare the images with hematoxylin eosin and saffron (HES)-stained histology. Zernike phase contrast, and the nonlinear optical microscopy techniques of second harmonic generation (SHG) and two-photon excitation fluorescence (TPEF) are reported. X-ray attenuation-, phase- and diffraction-contrast computed tomography (CT) images of the very same sample are also presented for comparisons. Future perspectives on the links to artificial intelligence, dynamic studies and in vivo possibilities conclude the article.

Insulin amyloid fibril formation reduction by tripeptide stereoisomers.

Insulin fibrillation is a problem for diabetic patients that can occur during storage and transport, as well as at the subcutaneous injection site, with loss of bioactivity, inflammation, and various adverse effects. Tripeptides are ideal additives to stabilise insulin formulations, thanks to their low cost of production and inherent cytocompatibility. In this work, we analysed the ability of eight tripeptide stereoisomers to inhibit the fibrillation of human insulin in vitro. The sequences contain proline as β-breaker and Phe-Phe as binding motif for the amyloid-prone aromatic triplet found in insulin. Experimental data based on spectroscopy, fluorescence, microscopy, and calorimetric techniques reveal that one stereoisomer is a more effective inhibitor than the others, and cell live/dead assays confirmed its high cytocompatibility. Importantly, in silico data revealed the key regions of insulin engaged in the interaction with this tripeptide, rationalising the molecular mechanism behind insulin fibril formation reduction.

Temporally resolved relative krypton neutral density during breathing mode of a hall effect thruster recorded by TALIF

A key issue in the development of theory and models for plasma propulsion devices is to describe the instabilities and fluctuations of the devices. It has been widely recognized that many Hall effect thrusters (HETs) exhibit oscillations at frequencies in the range of ∼ 20 kHz. These ionization-related oscillations are generally referred to as Breathing Mode oscillations and have been the subject of considerable research. Here, for the first time, we report direct temporally resolved measurements of the ground state neutral density variation during the period of the oscillation. We used the laser-based Two-Photon Absorption Laser Induced Fluorescence (TALIF) technique to measure neutrals within the plume of a 1.5 kW HET operating on krypton (Kr). Our TALIF scheme employs a frequency-doubled, pulsed dye laser operating at ∼ 212 nm to probe ground state Kr atoms. A novel phase-binning approach is used to recover the time-dependent signal by assigning the timing of each collected TALIF signal (laser shot) relative to the phase of the discharge current. We find that the neutral density fluctuates quite strongly over the period of the oscillation, and that this fluctuation leads the current fluctuation as expected.

Interactions of Co(II)- and Zn(II)porphyrin of 5,10,15,20-tetrakis(1-methyl-4-pyridinio)porphyrin with DNA in Aqueous Solution and Their Antimicrobial Activities.

Antibiotics are frequently used to treat, prevent, or control bacterial infections, but in recent years, infections resistant to all known classes of conventional antibiotics have significantly grown. The development of novel, nontoxic, and nonincursive antimicrobial methods that work more quickly and efficiently than the present antibiotics is required to combat this growing public health issue. Here, Co(II) and Zn(II) derivatives of tetrakis(1-methylpyridinium-4yl)porphyrin [H2TMPyP]4+ as a tetra(ρ-toluenesulfonate) were synthesized and purified to investigate their interactions with DNA (pH 7.40, 25 °C) using UV-vis, fluorescence techniques, and antimicrobial activity. UV-vis results showed that [H2TMPyP]4+ had a high hypochromicity (∼64%) and a substantial bathochromic shift (Δλ, 14 nm), while [Co(II)TMPyP]4+ and [Zn(II)TMPyP]4+ showed little hypochromicity (∼37%) and a small bathochromic shift (Δλ, 3-6 nm). Results reveal that [H2TMPyP]4+ interacts with DNA via intercalation, while Co(II)- and [Zn(II)TMPyP]4+ interact with DNA via outside self-stacking. Fluorescence results also confirmed the interaction of [H2TMPyP]4+ and the metalloporphyrins with DNA. Results of the antimicrobial activity assay revealed that the metalloporphyrins showed inhibitory effects on Gram-positive and Gram-negative bacteria and fungi, but that neither the counterions nor [H2TMPyP]4+ exhibited any inhibitory effects. Mechanism of antimicrobial activities of metalloporphyrins are discussed.

Recent Developments of Hybrid Fluorescence Techniques: Advances in Amyloid Detection Methods.

Amyloid fibrils are formed from various pathological proteins. Monitoring their aggregation process is necessary for early detection and treatment. Among the available detection techniques, fluorescence is simple, intuitive, and convenient due to its sensitive and selective mode of detection. It has certain disadvantages like poor photothermal stability and detection state limitation. Research has focused on minimising the limitation by developing hybrid fluorescence techniques. This review focuses on the two ways fluorescence (intrinsic and extrinsic) has been used to monitor amyloid fibrils. In intrinsic/label free fluorescence: i) The fluorescence emission through aromatic amino acid residues like phenylalanine (F), tyrosine (Y) and tryptophan (W) is present in amyloidogenic peptides/protein sequence. And ii) The structural changes from alpha helix to cross-β-sheet structures during amyloid formation contribute to the fluorescence emission. The second method focuses on the use of extrinsic fluorophores to monitor amyloid fibrils i) organic dyes/small molecules, ii) fluorescent tagged proteins, iii) nanoparticles, iv) metal complexes and v) conjugated polymers. All these fluorophores havetheir own limitations. Developing them into hybrid fluorescence techniques and converting it into biosensors can contribute to early detection of disease.

Investigation of the X‐ray fluorescence technique in the characterization of Ni coatings applied to historical heritage studies

AbstractHistorical heritage pieces allow a better comprehension of the characteristics of different civilizations over time. The characterization of such pieces is of paramount importance for their preservation. Energy‐dispersive X‐ray fluorescence (EDXRF) is recommended for this application, mostly because it is non‐destructive and the equipment is portable. However, one of its limitations is the difficulty in separating the signal from the substrate and the coating of multilayered samples, as it does not provide depth resolution. This project investigates the application of EDXRF in the characterization of metallic coatings, in the context of historical heritage. The elemental concentration of electrodeposited Ni coatings onto carbon steel substrates was obtained from EDXRF analyses. The relationship between the layer thickness and the variation of the Kα/Kβ intensity ratio of nickel peaks was exploited and the thicknesses of the coatings were estimated through EDXRF measurements. For comparison, particle‐induced x‐ray emission spectroscopy and scanning electron microscopy of the cross‐section were employed, providing a depth profile of the coatings. The estimated thicknesses from EDXRF analysis were comparable to those observed in the microscopy images for thinner films (up to 8 μm). On the other hand, for thicker films, the thicknesses were underestimated, due to the technique's depth limit and matrix effects, as secondary absorption. Despite these limitations, EDXRF remains valuable for evaluating cultural heritage pieces, often providing sufficient information to address authenticity concerns or to guide restoration processes. A case study was also performed to apply the methodology discussed on historical metallic pieces.

Design and synthesis of Lanthanide(III) complex based luminescence probes for time-resolved luminescence detection of β-galactosidase

β-Galactosidase (β-Gal), confirmed to provide energy and participate in the galactosyl transfer reaction, is primarily over-expressed in ovarian cancer cells. Herein, detecting endogenous β-Gal is essential for the diagnosis and monitoring of primary ovarian cancer cells. In this study, we proposed two structurally related cationic Lanthanide(III) triamide complexes for highly sensitive and rapid detection of β-Gal. Moreover, LDEu02 showed a low detection limit (2.3 × 10−3 U/mL) and high specificity with high affinity for β-Gal, which had great potential to the detection of the β-Gal activity by using time-resolved fluorescence techniques.

Light Induced Proton Coupled Charge Transfer Triggers Counterion Directional Translocation

AbstractWe demonstrate directed translocation of ClO4− anions from cationic to neutral binding site along the synthetized BPym‐OH dye molecule that exhibits coupled excited‐state intramolecular proton‐transfer (ESIPT) and charge‐transfer (CT) reaction (PCCT). The results of steady‐state and time‐resolved spectroscopy together with computer simulation and modeling show that in low polar toluene the excited‐state redistribution of electronic charge enhanced by ESIPT generates the driving force, which is much stronger than by CT reaction itself and provides more informative gigantic shifts of fluorescence spectra signaling on ultrafast ion motion. The associated with ion translocation red‐shifted fluorescence band (at 750 nm, extending to near‐IR region) appears at the time ~83 ps as a result of electrochromic modulation of PCCT reaction. It occurs at substantial delay to PCCT that displayed fluorescence band at 640 nm and risetime of <200 fs. Thus, it becomes possible to visualize the manifestations of light‐triggered ion translocation and of its driving force by fluorescence techniques and to separate them in time and energy domains.

Development and clinical evaluation of a real-time multiple cross displacement amplification assay for rapid and sensitive detection of Mycobacterium tuberculosis

Molecular techniques of nucleic acid testing recommended by the World Health Organization (WHO) for the Mycobacterium tuberculosis (MTB) detection were considered to have the potential access to the accurate tuberculosis (TB) notifications. In this study, a new method, which coupled real-time (rt) fluorescence technique with multiple cross displacement amplification (MCDA), was developed for the rapid, sensitive and specific detection of MTB (termed MTB-rt-MCDA). According to the principle of the rt-MCDA test, a set of ten primers were designed for the MCDA reaction, of which one was engineered with a restrictive endonuclease recognition site, a fluorophore and a quencher for achieving the real-time fluorescence detection. MTB-rt-MCDA test was conducted under the optimized conditions (67 °C, 40 minutes) on the real-time fluorescence platform. The MTB-rt-MCDA assay accurately identified the MTB strains with no cross reaction with other bacteria. The lowest detectable genomic DNA concentration of the MTB-rt-MCDA assay was 25 fg/μl. We employed the genomic DNA templates extracted from sputum of clinical cases for validating the practical applicability of this assay, and the detection power of the MTB-rt-MCDA assay was comparable to that of the Xpert method and MCDA-based biosensor detection and superior to smear microscope method. The complete process of the MTB-rt-MCDA assay, including rapid extraction of DNA and rt-MCDA test, takes less than 1 hour. In conclusion, the presented MTB-rt-MCDA assay provided an effective and simple option for the rapid screening of MTB infection.

Performance of sulfided NiMo catalyst supported on pillared bentonite Al and Ti under hydrodeoxygenation reaction of guaiacol

Bio-crude oil is known to be sustainable, eco-environmentally, and an alternative energy source produced by biomass pyrolysis. However, its quality remains relatively low due to a higher oxygen concentration compared to liquid fuels from fossils. Therefore, an upgrading process is necessary through the catalytic hydrodeoxygenation (HDO) process. This work synthesized pillared bentonite using Al and Ti metals as the pillaring agent to produce Al-PILC and Ti-PILC as catalyst support for sulfided NiMo. Their catalytic activity in HDO reaction using guaiacol as a model compound of bio-crude oil were also evaluated. Characterization of the bentonite-pillared materials, including Al-PILC, Mo/Al-PILC, NiMo/Al-PILC, Ti-PILC, Mo/Ti-PILC, and NiMo/Ti-PILC, was performed using Surface Area Analyzer, X-ray Diffractometer (XRD), Temperature-Programmed Desorption of ammonia (NH3-TPD), X-Ray Fluorescence (XRF), and Scanning Electron Microscope (SEM) techniques. The characterization results confirm the pillarization process of bentonite using Al and Ti metals as the pillaring agent, and the preparation of the NiMo catalyst using the stepwise impregnation method was successfully prepared. The NiMo/Ti-PILC catalyst performs a superior conversion value on the HDO guaiacol reaction than other catalysts. A well dispersion of Mo and Ni metals on the surface support (NiMo/Ti-PILC), thus creating numerous active sites of the catalyst after the sulfidation. Variations in time and temperature during the HDO guaiacol reaction significantly affected the conversion.

On the effects of walking speed, crowd density and human-to-source distance on pollutant dispersion in indoor spaces

The effects of walking speed, crowd density and human-to-source distance on pollutant dispersion in two scaled room models are investigated using simultaneous planar laser-induced fluorescence and particle-image velocimetry techniques. For a small 3 m high room, where the length-scales of the people and room are comparable, the walking motions significantly influenced the macro room mean flow patterns. This has a strong effect on the scalar dispersion properties as the magnitudes of the advective scalar fluxes are often comparable or larger than the turbulent scalar fluxes. As such, the scalar dispersion properties are case specific. For a large 9 m high room, the walking motion influenced only the local mean flow field. The increase in walking speed and crowd density improves the efficiency in which the scalar is transported and mixed with fresh ambient fluid out of the measurement plane (i.e. along the direction of the motion), leading to scalar-free zones observed on the opposite side of the room from the ventilation outlet. The area of the scalar-free zone increases with an increase in the walking speed and crowd density. The advective scalar fluxes are more sensitive to the human motion than the turbulent components, and as the mixing efficiency improves, the advective fluxes show a greater weakening with increased distance from source. The concentration PDFs in the near-source region can be described by the exponential function where the expected value at the 99% percentile can be derived as C99/crms′=4.61, which agreed well with the experimental measurements of 4.1 to 5.9.

Addressing the interaction of stem bromelain with different anionic surfactants, below, at and above the critical micelle concentration (cmc) in phosphate buffer at pH 7: Physicochemical, spectroscopic, & molecular docking study

The structural stability and therapeutic activity of Stem Bromelain (BM) have been explored by unravelling the interaction of stem BM in presence of two different types of anionic surfactants namely, bile salts, NaC and NaDC and the conventional anionic surfactants, SDDS and SDBS, below, at and above the critical micelle concentration (cmc) in aqueous phosphate buffer of pH 7. Different physicochemical parameters like, surface excess (Γcmc), minimum area of surfactants at air water interface (Amin) etc. are calculated from tensiometry both in absence and presence of BM. Several inflection points (C1, C2 and C3) have been found in tensiometry profile of surfactants in presence of BM due to the conformational change of BM assisted by surfactants. Similar observation also found in isothermal titration calorimetry (ITC) profiles where the enthalpy of micellization (ΔH0obs) of surfactants in absence and presence of BM have calculated. Further, steady state absorption and fluorescence spectra monitoring the tryptophan (Trp) emission of free BM and in presence of all the surfactants at three different temperatures (288.15 K, 298.15 K, and 308.15 K) reveal the nature of fluorescence quenching of BM in presence of bile salts/surfactants. Time resolved fluorescence studies at room temperature also support to determine the several quenching parameters. The binding constant (Kb) of BM with all the surfactants and free energy of binding (∆G0 of bile salts/surfactants with BM at different temperatures have been calculated exploiting steady state fluorescence technique. It is observed that, the binding of NaC with BM is greater as compared to other surfactants while Stern-Volmer quenching constant (KSV) is found greater in presence of SDBS as compared with others which supports the surface tension and ITC data with the fact that surface activity of surfactant(s) is decreasing with the binding of the surfactants at the core or binding pocket of BM. Circular Dichroism (CD) study shows the stability of secondary structure of BM in presence of NaC and NaDC below C3, while BM lost its structural stability even at very low surfactant concentration of SDDS and SDBS which also supports the more involvement of bile salts in binding rather than surfactants. The molecular docking studies have also been substantiated for better understanding the several experimental investigations interaction of BM with the bile salts/surfactants.