Spectrophotometric Measurements Research Articles

Global Extraction from Parallel Reaction Monitoring to Quantify Background Peptides for Improved Normalization and Quality Control in Targeted Proteomics.

Mass spectrometry-based targeted proteomics employs heavy isotope-labeled proteins or peptides as standards to improve accuracy and precision. The input sample amount is often determined by the total quantity of endogenous proteins or peptides, as defined by spectrophotometric assays, before the heavy-isotope standards are spiked into the samples. Errors in spectrophotometric measurements, which may be due to low sensitivity or chemical or biological interference, have a direct impact on the quantitative mass spectrometry results. Currently used targeted proteomics workflows cannot identify or correct deviations that arise from differences in the input sample amount. We have developed a workflow, global extraction from parallel reaction monitoring (PRM), to identify and quantify thousands of background peptides that are inherently acquired by PRM experiments. These background peptides were used to identify differences in the input sample amount and to reduce this variance by intensity-based, post-acquisition normalization. This approach was then applied to a xenograft study to improve the quantification of human proteins in the presence of mouse tissue contamination. In addition, these background peptides also provided a direct source of quality control metrics related to sample handling and preparation.

Experimental study and theoretical modeling of coating-speed-dependent optical properties of TiO2-graphene-oxide thin films

Nanostructured titanium dioxide–graphene oxide (TiO2-GO) thin films have been successfully synthesized and deposited on glass substrates using spin coating technique. TiO2-GO nanocomposites were prepared using Titanium Tetra Isopropoxide (TIP) and Graphene Oxide (GO) nanosheets. The influences of spin coating deposition speed on the structural, morphological, and optical features of the resulting TiO2-GO samples have been investigated. X-ray diffraction (XRD) patterns showed an amorphous structure of all deposited films. Scanning electron microscopy (SEM) images demonstrated that these films are homogeneous and all free from cracking over the entire surface of the sample, regardless of the number of rotations used. Atomic force microscopy (AFM) topography images reveal that all samples are smooth with very small surface roughness. Optical data obtained from UV–Vis spectrophotometer measurement together with theoretical modeling using Tauc–Lorentz (TL) oscillator model showed that all films display high transmittance level around 85% from the visible to the near-infrared region. It is also shown that an increase in spin coating speed results in a decrease in the film thickness and the optical band gap. The observed optical features reveal that TiO2-GO thin films are promising candidate that can be used as transparent conducting oxide electrode in solar cells.

Physical and optoelectronic characteristics of novel low-cost synthesized coumarin dye-based metal-free thin films for light sensing applications

Herein, we have evolved a new and efficient procedure for the synthesis of 3-(2-(4-bromophenyl)hydrazone)-2,4-chromandione BPHCvia the cyclization of (4-bromo-phenylhydrazono)-malonic acid with phenol in the presence of zinc chloride. The thermal stability of the final product is investigated by using DSC/TGA techniques. Thermal deposited BPHC thin films are successfully prepared under vacuum. The IR results of BPHC powder and thin films declare that the deposited films exhibit a stable molecular structure even upon annealing. The as-deposited BPHC thin films exhibit a polycrystalline phase and smooth surface, which are enhanced by annealing at 373 K as observed in the XRD and FE-SEM results. The spectrophotometric measurements showed the enhanced optical absorption in UV and visible spectral bands for the annealed films at 373 K with a decreased energy gap of about 2.37 eV. The dispersion behavior is analyzed as a function of annealing temperatures by using a single oscillator model. The BPHC thin films showed strong PL emission at 522 nm with excitonic binding energy ∼0.17 eV. Furthermore, the organic/inorganic hetero-architecture based on BPHC/n-type silicon is designed and fabricated with significant rectification behavior. The microelectronic parameters of the manufactured heterojunction are calculated and discussed in detail. Moreover, the fabricated device showed a promising stable linear response to light signals with responsivity ∼16.9 mA/W and specific detectivity ∼3.35 × 1010Jones. The repeatable, stable, and efficient performance of the present device suggests this material as a powerful candidate for photosensing applications.

Nonlinear optical behavior of non‐centrosymmetric biferrocenyl Schiff‐base derivatives and their DNA binding potential supported by DFT and electrochemical investigations

AbstractTwo new non‐centrosymmetric biferrocenyl Schiff bases, that is, N‐(ferrocenylmethylene)‐4‐(4‐(ferrocenylmethyleneamino)phenoxy)benzenamine (FeL1) and 4,4′‐([1,1′‐biferrocenyl]‐4,4′‐diylbis(methylene)bis(N‐benzylideneaniline) (FeL2), have been synthesized and studied by density functional theory (DFT) to understand their nonlinear optical (NLO) behavior. The synthesized compounds were characterized by FTIR, NMR, and UV–visible spectroscopic techniques. DFT studies were performed to obtain the polarizability and first‐order hyperpolarizability parameters useful in determining the NLO response. Results indicate that the substituted biferrocenyl Schiff bases show a substantial increase in first‐order hyperpolarizability (44 times greater than the reference urea) compared with unsubstituted ferrocene. The enhanced NLO behavior follows the trend FeL2 > FeL1 > urea. Bader's atoms in molecules (AIM) theory has been employed to obtain topological parameters and critical points to evaluate the nature and strength of different types of intramolecular interactions. Charge delocalization in the complexes was investigated through natural bond order (NBO) analysis. It was observed that intramolecular charge transfer (ICT) is responsible for the optical nonlinearity of the biferrocenyl Schiff bases, with hydrogen bonding playing a prominent role in the bonding networks leading to increased hyperpolarizability. Furthermore, molecular electrostatic potential (MEP) surfaces of the molecular systems have also been analyzed. From an application viewpoint, the interaction of the biferrocenyl derivatives with fish‐sperm DNA was studied through spectrophotometric and electrochemical measurements. Results indicate major groove binding with DNA, which is also predicted by molecular docking studies.

Direct method of extracting broadband complex refractive index from spectrophotometric measurements: an application to polydimethylsiloxane for passive radiative cooling.

We describe an algorithm to extract the complex refractive index of a material from broadband reflectance and transmittance measurements taken by spectrophotometers. The algorithm combines Kramers-Kronig analysis with an inversion of Fresnel's equations to provide a direct method of solving for the refractive index which is accurate, even for weakly absorbing materials, and easily applicable to radiative heat transfer calculations. The algorithm is validated by extracting the complex refractive index of polydimethylsiloxane between 0.25 μm and 100 μm and comparing against existing literature. We also discuss the importance of broadband optical properties to passive radiative cooling and details of the uncertainty analysis of the algorithm.

Synthesis, Characterization and Thermogravimetric Study of Some Metal Complexes of Selenazone Ligand Nanoparticles Analogue of Dithizone

A new method for preparing 1,5-diphenylselenocarbazone (selenazone) nanoparticles and their complexes with Pb2+, Cd2+, Co2+, and Ni2+ has been performed using hot methanol solvent. The ligand and its complexes were characterized using FT-IR, UV-Vis, 1H-NMR, 13C-NMR, X-ray powder diffraction (XRD), EI-mass spectrometry, scanning electron microscopy (SEM), HG and flame-atomic absorption spectrophotometer, thermal analysis (TG/DTA), and molar conductance measurements. The molar conductance measurements in all complexes were recorded low values in DMSO, indicating that all the metal complexes were non-electrolytes except the nickel complex that possessed an electrolytic nature. Kinetic and thermodynamic parameters of complexes (A, E, ∆H, ∆S, and ∆G) have been computed using three kinetic models of Coast-Redfern, Broido, and Horowitz-Metzger, that illustrated the decomposition reactions in all steps were nonspontaneous. Thermogravimetric analyses (TG/DTA) were consistent with the atomic spectroscopy data proving that the geometry shape of all the complexes was octahedral.

Study on inhibition behaviors of asphaltene inhibitor to asphaltene aggregations

The changes in the stability of asphaltene in crude oil will give rise to its aggregation, coalescence and deposition from crude oil. The preferred method for improving asphaltene stability is the addition of asphaltene inhibitor (ASIN). The interactions between asphaltene and six inhibitors (S1-S6) were investigated from effects of the ASIN molecular properties such as the acidity, the relative positions of polar and non-polar groups on the benzene ring, and molecular size on the effectiveness of ASIN. The effectiveness, asphaltene aggregation number and degree of solvation for the asphaltene of Canadian oil sand bitumens (COSB) in heptol with or without ASIN were obtained by the solution viscosity and spectrophotometric measurements. The groups impacting the inhibitor effectiveness from high to low are sulfonic acid group, hydroxyl group and the amine group attached to the benzene ring. The interaction between the boric acid group in S5 and asphaltene is stronger than that between sulfonic acid group in S6 and asphaltene, indicating that the spatial protection to asphaltene by macromolecular chains of S5 relative to acidity is expected to prevail. Because of their suitable spatial structure, the inhibitor molecules with the polar and nonpolar groups located at the para-position of the benzene ring are more favorable to inducing dense arrangement of inhibitor molecules on asphaltene and thus provide a stronger protective effect for asphaltene. Viscosity measurements showed that the aggregation number of asphaltene in heptol with inhibitors decreased and the solvation constant increased, leading to improve the compatibility of asphaltene aggregates with solvents.

From Food to Mobility: Investigating a Screening Assay for New Automotive Antioxidants Using the Stable Radical DPPH

AbstractBy taking inspiration from the food industry, an assay was investigated as a potential screening tool to test the efficiency of new phenolic antioxidants. The method was based on the spectrophotometric measurement of the stable free radical 1,1‐diphenyl‐2‐picryl hydrazyl (DPPH) which, in its radical form, has an absorbance maxima at 515 nm. The disappearance of this absorbance band, upon reaction with an antioxidant, was monitored to reveal the kinetic pathway of the reaction, which was defined simply as either fast, medium or slow. Adaptation of the assay was attempted for application to biofuels and oil‐based automotive fluids whereby the effect of polar and non‐polar solvents on the kinetics of the reaction was investigated. In addition, the stoichiometry of the radical scavenging reaction was also analysed to give an insight into the structure‐activity relationships of phenolic antioxidants.

Optoacoustic Sensing of Surfactant Crude Oil in Thermal Relaxation and Nonlinear Regimes.

We propose a laser optoacoustic method for the complex characterization of crude oil pollution of the water surface by the thickness of the layer, the speed of sound, the coefficient of optical absorption, and the temperature dependence of the Grüneisen parameter. Using a 532 nm pulsed laser and a 1–100 MHz ultra-wideband ultrasonic antenna, we have demonstrated the capability of accurate (>95%) optoacoustic thickness measurements in the 5 to 500-micron range, covering 88% of slicks observed during 2010 oil spill in the Gulf of Mexico. In the thermal relaxation regime of optoacoustic measurements, the value of optical absorption coefficient (30 mm−1) agreed with the data of independent spectrophotometric measurements, while the sound speed (1430 m/s) agreed with the tabular data. When operating in a nonlinear regime, the effect of local deformation of the surface of the oil film induced by heating laser radiation was revealed. The dose-time parameters of laser radiation ensuring the transition from the thermal relaxation regime of optoacoustic generation to nonlinear one were experimentally investigated. The developed OA method has potential for quantitative characterization of not only the volume, but also the degree and even the type of oil pollution of the water surface.

Cover Image, Volume 138, Issue 46

The image provided by Tomoya Takada and colleagues shows a cross-sectional SEM micrograph of acrylic denture base resin impregnated with nanodiamond (ND). This study aimed to evaluate the effect of ND impregnation on the thermal conductivity of commercially available acrylic denture base resins. It was found that the thermal conductivity of the resin was maximum when the resin was impregnated with a small amount of NDs. The colors of the ND-impregnated resins were also compared using spectrophotometric measurements. DOI: 10.1002/app.51436

Green Composite Sensor for Monitoring Hydroxychloroquine in Different Water Matrix.

Hydroxychloroquine (HCQ), a derivative of 4-aminoquinolone, is prescribed as an antimalarial prevention drug and to treat diseases such as rheumatoid arthritis, and systemic lupus erythematosus. Recently, Coronavirus (COVID-19) treatment was authorized by national and international medical organizations by chloroquine and hydroxychloroquine in certain hospitalized patients. However, it is considered as an unproven hypothesis for treating COVID-19 which even itself must be investigated. Consequently, the high risk of natural water contamination due to the large production and utilization of HCQ is a key issue to overcome urgently. In fact, in Brazil, the COVID-19 kit (hydroxychloroquine and/or ivermectin) has been indicated as pre-treatment, and consequently, several people have used these drugs, for longer periods, converting them in emerging water pollutants when these are excreted and released to aquatic environments. For this reason, the development of tools for monitoring HCQ concentration in water and the treatment of polluted effluents is needed to minimize its hazardous effects. Then, in this study, an electrochemical measuring device for its environmental application on HCQ control was developed. A raw cork–graphite electrochemical sensor was prepared and a simple differential pulse voltammetric (DPV) method was used for the quantitative determination of HCQ. Results indicated that the electrochemical device exhibited a clear current response, allowing one to quantify the analyte in the 5–65 µM range. The effectiveness of the electrochemical sensor was tested in different water matrices (in synthetic and real) and lower HCQ concentrations were detected. When comparing electrochemical determinations and spectrophotometric measurements, no significant differences were observed (mean accuracy 3.0%), highlighting the potential use of this sensor in different environmental applications.

Evaluating the masking ability of CAD/CAM hybrid ceramics with different thicknesses

Aim: A discoloration existing under the restoration can affect the final restoration color, and various techniques can be used to address this situation. The aim of this study was to investigate the masking ability of the substructure, color of different hybrid CAD/CAM ceramics in various thicknesses.
 Methodology: A total of 120 samples were produced from 4 different CAD/CAM hybrid ceramic blocks (Cerec blocs, GC Cerasmart, Vita Enamic, 3M Lava Ultimate) in 1, 1.5 and 2 mm thickness. The samples were sliced with 100 N pressure in a low-speed precision cutting device under water cooling. The specimens were placed over the neutral grey background for initial spectrophotometric measurements. A3 color posterior nanohybrid composite (14 X 7 X 1 mm) was preferred to mimic discoloration in the substructure. The cementation procedure of composite and the CAD/CAM hybrid ceramic complex was standardized under 10 N continuous pressure and was performed using a dual cured resin cement. All samples were incubated at 37 °C for 24 hours in incubator after cementation. And the second spectrophotometeric measurement was done via the L*, a*, and b* color attributes of the complex specimens. Additionally, ΔE* values were calculated to determine the color differences between each group. Kruskal Wallis test was used for statistical analysis and Dunn’s test was used for group comparison. Significance was evaluated at least p <0.05.
 Results: It was found that thickness of the ceramics increases, the substructure color is better masked and the thickness made a statistically significant difference on the masking ability (p<0.01). For 1 mm thick samples, the highest ΔE* value was found in Cerec blocs with 9.36, while the lowest value was found in GC Cerasmart as 4.27.
 Conclusion: Within the limitations of this study, it was concluded that the tested CAD/CAM hybrid ceramics showed better masking ability than Cerec blocs.
 
 How to cite this article: Ünalan Değirmenci B, Wahid WF. Evaluating the masking ability of CAD/CAM hybrid ceramics with different thicknesses. Int Dent Res 2021;11(2):114-20. https://doi.org/10.5577/intdentres.2021.vol11.no1.9
 
 Linguistic Revision: The English language in this manuscript has been checked by at least two professional editors, both native speakers of English.

Hydroxyl Radical Scavenging Activity of Stachytarpheta jamaecensis Root Extract using In Vitro Deoxyribose Degradation Assay

Use and demand of traditional medicinal plants currently growing in the direction that research in traditional medicines have also increased. One of the plants that is efficacious as a medicine is S. jamaecensis. This plant is usually used by people as a traditional medicine to treat various diseases. This study aims to determine the antioxidant activity of porterweed root. Antioxidant activity assays performed using hydroxyl radical scavenger that begins with the extraction by maceration. Dry roots of S. jamaecensis (250 g) was soaked with ethanol 96% for 3x24 hours at room temperature. The liquid extract obtained is evaporated by rotary evaporator and waterbath till viscous extracts is obtained. Then to extract performed phytochemical screening by quantitative and qualitative method. The antioxidant test was carried out using the hydroxyl radical scavenger method. The extract concentrations were varied, namely 125, 250, 500 and 1000 ppm. The data obtained was performed one-way ANOVA test. The results of the phytochemical screening showed the extract contains flavonoids, alcaloids, saponins, phenols and tannins. The results obtained were significant values from the antioxidant test with the antiradical scavenger method, the largest average value of root extract was 60.606% at a concentration of 1000 ppm. The results of spectrophotometric measurements showed that the extract has IC50 was 683.5294 µg/ml, while vitamin C has IC50 lower value (251.700 µg/ml). Q

Real-Time Monitoring of Microalgal Biomass in Pilot-Scale Photobioreactors Using Nephelometry

The increasing cultivation of microalgae in photobioreactors warrants efficient and non-invasive methods to quantify biomass density in real time. Nephelometric turbidity assessment, a method that measures light scatter by particles in suspension, was introduced already several decades ago but was only recently validated as a high-throughput tool to monitor microalgae biomass. The light scatter depends on the density of the suspended particles as well as on their physical properties, but so far there are hardly any accounts on how nephelometric assessment relates to classic methods such as dry weight and spectrophotometric measurement across a broad biomass density range for different microalgae species. Here, we monitored biomass density online and in real time during the semi-continuous cultivation of three commercial microalgae species Chloromonas typhlos, Microchloropsis gaditana and Porphyridium purpureum in pilot-scale photobioreactors, and relate nephelometric turbidity to dry weight and optical density. The results confirm a relatively strong (R2 = 0.87–0.93) and nonlinear relationship between turbidity and biomass density that differs among the three species. Overall, we demonstrate how nephelometry can be used to monitor microalgal biomass in photobioreactors, and provide the necessary means to estimate the biomass density of the studied species from turbidity data to facilitate automated biomass monitoring.

A selective Nile Red based solvatochromic probe: A study of fluorescence in LUVs and GUVs model membranes

In this work, a membrane probe (NR18) with a Nile Red-based chromophore, a long tail of 18 carbon atoms and a zwitterionic head was synthesized. The probe is optimized to remain anchored to the phospholipid bilayer without internalizing. NR18 was fully characterized chemically and optically and showed marked solvatochromism. Incorporation into model membranes of LUVs and GUVs having different compositions, demonstrated that the probe could be used to discriminate the lipid order in membranes, based on the fluorescent radiation emitted. Spectrophotometric and fluorimetric measurements on LUVs showed that the emission wavelength increases with temperature, confirming the increase in fluidity and hydration in membranes at higher temperatures. DFT simulations helped us to clarify the impact of NR18 on the membrane thickness and the order parameter showing that NR18 does not cause substantial perturbation in the bilayer. Moreover, we demonstrated that the presence of an enaminic terminal group is mainly responsible for the ability of NR18 to have a different fluorescence in Ld and Lo membranes.

How Different Albumin-Binders Drive Probe Distribution of Fluorescent RGD Mimetics

The biodistribution of medical imaging probes depends on the chemical nature of the probe and the preferred metabolization and excretion routes. Especially targeted probes, which have to reach a certain (sub)cellular destination, have to be guided to the tissue of interest. Therefore, small molecular probes need to exhibit a well-balanced polarity and lipophilicity to maintain an advantageous bioavailability. Labelled antibodies circulate for several days due to their size. To alter the biodistribution behavior of probes, different strategies have been pursued, including utilizing serum albumin as an inherent transport mechanism for small molecules. We describe here the modification of an existing fluorescent RGD mimetic probe targeted to integrin αvβ3 with three different albumin binding moieties (ABMs): a diphenylcyclohexyl (DPCH) group, a p-iodophenyl butyric acid (IPBA) and a fatty acid (FA) group with the purpose to identify an optimal ABM for molecular imaging applications. All three modifications result in transient albumin binding and a preservation of the target binding capability. Spectrophotometric measurements applying variable amounts of bovine serum albumin (BSA) reveal considerable differences between the compounds concerning their absorption and emission characteristics and hence their BSA binding mode. In vivo the modified probes were investigated in a murine U87MG glioblastoma xenograft model over the course of 1 wk by fluorescence reflectance imaging (FRI) and fluorescence mediated tomography (FMT). While the unmodified probe was excreted rapidly, the albumin-binding probes were accumulating in tumor tissue for at least 5 days. Considerable differences between the three probes in biodistribution and excretion characteristics were proved, with the DPCH-modified probe showing the highest overall signal intensities, while the FA-modified probe exhibits a low but more specific fluorescent signal. In conclusion, the modification of small molecular RGD mimetics with ABMs can precisely fine-tune probe distribution and offers potential for future clinical applications.

Dielectric properties, Optoelectrical parameters and electronic polarizability of thermally evaporated a-Pb-Se-Ge thin films

This article is devoted to the study of various dielectric and optoelectrical parameters, besides electronic polarizability, and metallization parameter of amorphous Pb10Se90-xGex (0.0≤x≤10.0at.%) thin films. These studies are based on the calculated values of refractive and extinction coefficient. The thin films were prepared using the conventional thermal evaporation technique. All samples were previously investigated by XRD, EDX, and UV–Vis–NIR spectrophotometric measurements. Using refractive index and extinction coefficient spectra, the dielectric constant (real and imaginary parts), dissipation and quality factors are discussed. Also, many optoelectrical factors of Pb–Se-Ge films have been studied. The energy loss functions, high-frequency dielectric constant and optical carrier concentration are also deduced and studied. The plasma frequency and some other optoelectrical parameters, such as scattering time, optical mobility, and optical resistivity are studied and discussed. From the computed results it can be said that these films can be used in many optoelectronic applications, IR photodetectors, and sensors.

Consistency and stability of purified meta-cresol purple for spectrophotometric pH measurements in seawater

Analysis of a global hydrographic data product showed a clear pH-dependent discrepancy between pH on the total scale measured spectrophotometrically (pHspec) using purified meta-Cresol Purple (mCP) and pH calculated from total alkalinity and dissolved inorganic carbon. However, this was based mainly on US cruises, and three recent Japanese cruises do not show this pH-dependent discrepancy. One potential explanation is that purified mCP batches obtained from different institutions lead to significantly different pHspec. Here, we tested this hypothesis by comparing the performance of purified mCP obtained from four different institutions. We demonstrate that consistent pH of ±0.0012 (95% C.I.) can be achieved regardless of the institution when impurities are properly removed. However, there was at least one batch from three of the four institutions that had significant pH-dependent errors that were as large as −0.008. The presence of impurities that led to pH-dependent errors was identified using HPLC and, for 8 out of the 9 cases, by spectrophotometry (although issues still remain for the latter). We conclude that pH-dependent errors due to impurities that remain after the purification process are, by themselves, too small to account for the differences observed between the recent set of cruises. Identifying the source of this difference should be a top priority. This study also highlights the importance of establishing robust quality assurance and quality control protocols to ensure consistent behavior with previously published equations to compute pH. We recommend a centralized system where one or a handful of institutions distribute purified mCP for the community, as this distribution approach will lead to lower prices and simplify quality assurance.

Optical properties upon ZnS film thickness in ZnS/ITO/glass multilayer films by ellipsometric and spectrophotometric investigations for solar cell and optoelectronic applications

ZnS film with various thicknesses (d ≈ 100–350 nm) deposited on the ITO coated glass substrate (ZnS/ITO/glass) by an electron beam evaporation process was examined structurally and optically. Different techniques were used to specify and analyze the optical characteristics of the film, such as spectroscopic ellipsometric (SE) and spectrophotometric (SP). The ZnS/ITO/glass films exhibit a wurtzite hexagonal type structure entrenched in the crystalline background of ITO film. XRD analysis revealed changes in structural and microstructural parameters, such as a decrease in lattice parameters, a reduction in microstrain, and a raise in crystallite size. The optical constants and the optical energy gap were extracted from SE by constructing an ellipsometric optical model, while the optical constants were calculated from SP by using Murmann's exact equations. It was seen that the overall behaviour of the refractive index n of the ZnS/ITO/glass films obtained from SE and SP increases with an increase in ZnS layer thickness, which is attributed to the increment of the size of the grain. It was additionally found that, the overall behaviour of the extinction coefficient k of the ZnS/ITO/glass films increases, when the thickness of the ZnS layer increments. Also, the direct optical transition was observed with energy band gap diminishes from 3.423 (d = 100 nm) eV to 3.287 eV (d = 350 nm) that is because of the rise in grain size, the decrease in microstrain, and reduction in lattice constants. Furthermore, it was found that the deposition of ZnS on ITO coated glass substrate increases the absorption compared with the ZnS/glass film and then reduces the transmittance and energy band gap. It was concluded that as the ZnS thickness increases, the optical constants of ZnS/ITO/glass films enhance. Finally, the overall behaviour of the optical constants within the experimental error range of the ZnS/ITO/glass films with different ZnS layer thicknesses obtained by SE was found to be consistent with that calculated from SP measurement. • Synthesis of various thicknesses (d ≈ 100–350 nm) of (ZnS/ITO/glass) via electron beam evaporation. • Investigation of the effects of film thickness on the optical and structural properties of (ZnS/ITO/glass). • The increase in ZnS thickness led to enhance the optical constants of ZnS/ITO/glass films.

Alternative Methods of Evaluation of Antimicrobial Activity of Breast Milk Serum.

Antimicrobial properties are traditionally evaluated by the seeding technique, which is laborious, time-consuming, and rather imprecise. We studied the possibility of using microscopy and spectrophotometry methods for evaluation of cytotoxic activity of breast milk serum against opportunistic microbes. Activity of 50 breast milk samples obtained from healthy women at different lactation stages was tested against opportunistic yeast C. albicans. Microscopy showed that incubation of cell suspension with lactoserum led to destruction of cell walls and cytoplasmic membranes with the formation of vesicular debris that absorbed the dye from the medium. Spectrophotometric measurement of the dye remained in the medium revealed a dose-depended effect of the lactoserum on C. albicans cells and strong inverse correlation between the lactation period and cytotoxic activity of the lactoserum (r=-0.948). These methods can be used in veterinary and food processing for estimation of biological activity of milk.