Stokes-Mueller polarization-based analysis of model SARS-CoV-2 virions.

Understanding the virology of the coronavirus at the structural level has gained utmost importance to overcome the constant and long-term health complications induced by them. In this work, the light scattering properties of SARS-CoV-2 of size 140 nm were simulated by using discrete dipole approximation (DDA) for two incident wavelengths 200 nm and 350 nm, respectively. Three different 3-dimensional (3D) models of SARS-CoV-2 corresponding to 15, 20, and 40 numbers of spike proteins on the viral capsid surface were constructed as target geometries for the DDA calculations. These models were assessed by employing Stokes-Mueller polarimetry to obtain individual polarization properties such as degree of polarization (DOP), degree of linear polarization (DOLP), and degree of circular polarization (DOCP). Irrespective of its spike numbers, all the coronavirus models were found to display higher DOP and DOCP values and negligibly small DOLP values for circularly polarized incident light, indicating the presence of chiral structures. On the other hand, the lack of understanding about the dependence of the Mueller matrix on its microstructural properties was overcome by transforming 16 Mueller elements into sub-matrices with specific structural and physical properties using Lu-Chipman-based Mueller matrix polar decomposition method. The obtained properties such as retardance, diattenuation, and depolarization were used for investigating the composition and microstructural information. The approach presented in this work has the potential to understand the virology of the coronavirus at the structural level and, therefore, will be beneficial in developing effective detection strategies by exploiting their characteristic electromagnetic scattering signatures.

An insight into optical beam induced current microscopy: Concepts and applications.

Laser scanning optical beam induced current (OBIC) microscopy has become a powerful and nondestructive alternative to other complicated methods like electron beam induced current (EBIC) microscopy, for high resolution defect analysis of electronic devices. OBIC is based on the generation of electron-hole pairs in the sample due to the raster scanning of a focused laser beam with energy equal or greater than the band gap energy and synchronized detection of resultant current profile with respect to the beam positions. OBIC is particularly suitable to localize defect sites caused by metal-semiconductor interdiffusion or electrostatic discharge (ESD). OBIC signals, thus, are capable of revealing the parameters/factors directly related to the reliability and efficiency of the electronic device under test (DUT). In this review, the basic principles of OBIC microscopy strategies and their notable applications in semiconductor device characterization are elucidated. An overview on the developments of OBIC microscopy is also presented. Specifically, the recent progresses on the following three OBIC measurement strategies have been reviewed, which include continuous laser based single photon OBIC, pulsed laser based single photon OBIC, and multiphoton OBIC microscopy for three-dimensional mapping of photocurrent response of electronic devices at high spatiotemporal resolution. Challenges and future prospects of OBIC in characterizing complex electronic devices are also discussed. HIGHLIGHTS: Characterization of electronic device quality is of paramount importance. Optical beam induced current (OBIC) microscopy offers spatially resolved mapping of local electronic properties. This review presents the principle and notable applications of OBIC microscopy.

Polarimetric Measurements of Surface Chirality Based on Linear and Nonlinear Light Scattering.

A molecule, molecular aggregate, or protein that cannot be superimposed on its mirror image presents chirality. Most living systems are organized by chiral building blocks, such as amino acids, peptides, and carbohydrates, and any change in their molecular structure (i.e., handedness or helicity) alters the biochemical and pharmacological functions of the molecules, many of which take place at surfaces. Therefore, studying surface chirogenesis at the nanoscale is fundamentally important and derives various applications. For example, since proteins contain highly ordered secondary structures, the intrinsic chirality can be served as a signature to measure the dynamics of protein adsorption and protein conformational changes at biological surfaces. Furthermore, a better understanding of chiral recognition and separation at bio-nanointerfaces is helpful to standardize chiral drugs and monitor the synthesis of adsorbents with high precision. Thus, exploring the changes in surface chirality with polarized excitations would provide structural and biochemical information of the adsorbed molecules, which has led to the development of label-free and noninvasive measurement tools based on linear and nonlinear optical effects. In this review, the principles and selected applications of linear and nonlinear optical methods for quantifying surface chirality are introduced and compared, aiming to conceptualize new ideas to address critical issues in surface biochemistry.

Enantiomeric Recognition and Separation by Chiral Nanoparticles.

Chiral molecules are stereoselective with regard to specific biological functions. Enantiomers differ considerably in their physiological reactions with the human body. Safeguarding the quality and safety of drugs requires an efficient analytical platform by which to selectively probe chiral compounds to ensure the extraction of single enantiomers. Asymmetric synthesis is a mature approach to the production of single enantiomers; however, it is poorly suited to mass production and allows for only specific enantioselective reactions. Furthermore, it is too expensive and time-consuming for the evaluation of therapeutic drugs in the early stages of development. These limitations have prompted the development of surface-modified nanoparticles using amino acids, chiral organic ligands, or functional groups as chiral selectors applicable to a racemic mixture of chiral molecules. The fact that these combinations can be optimized in terms of sensitivity, specificity, and enantioselectivity makes them ideal for enantiomeric recognition and separation. In chiral resolution, molecules bond selectively to particle surfaces according to homochiral interactions, whereupon an enantiopure compound is extracted from the solution through a simple filtration process. In this review article, we discuss the fabrication of chiral nanoparticles and look at the ways their distinctive surface properties have been adopted in enantiomeric recognition and separation.

Direct mineralogical imaging of economic ore and rock samples with multi-modal nonlinear optical microscopy.

Multi-modal nonlinear optical (NLO) microscopy, including stimulated Raman scattering (SRS) and second harmonic generation (SHG), was used to directly image mineralogical features of economic ore and rock samples. In SRS/SHG imaging, ore samples generally require minimal preparation and may be rapidly imaged, even in their wet state. 3D structural details, at submicron resolution, are revealed tens of microns deep within samples. Standard mineral imaging based on scanning electron microscopy (SEM), with elemental analysis via energy dispersive X-Ray spectroscopy, was used to independently validate the mineral composition of the samples. Spatially-resolved SRS from dominant Raman-resonant bands precisely maps the locations of specific minerals contained within the samples. SHG imaging reveals locally non-centrosymmetric structures, such as quartz grains. Competing absorption and nonlinear scattering processes, however, can reduce contrast in SRS imaging. Importantly, the correlation between standard electron microscopy and multi-modal NLO optical microscopy shows that the latter offers rapid image contrast based on the mineral content of the sample.

Evaluation of Antioxidant and Hepatoprotective Activity of Fruit Rind Extract of Garcinia dulcis (Roxburgh) Kurz.

BACKGROUND: Garcinia spp. belongs to the family Clusiaceae has been traditionally used for the treatment of many ailments including the liver damage. Garcinia dulcis found in North Eastern region of Assam; India can be a potential candidature to combat different ailments. Objective: The present work has been designed in such a way to appraisal the antioxidant and hepatoprotective activity of fruit rind extract of this plant. MATERIALS AND METHODS: The antioxidant activity was investigated through the various in vitro models, namely, 2,2-diphenyl-1-picrylhydrazine, 2,2'-azino-bis-3-ethylbenzothiazoline-6-sulfonic acid, nitrite oxide. Phytochemical investigation for total phenolic and flavonoids contents were carried out by standard protocol. For the evaluation of hepatoprotective activity, albino Wistar rats were divided into five groups, five animals per group and activity was determined by measuring the contents of liver function marker enzymes such as serum glutamate oxaloacetate transaminase (SGOT), serum glutamate pyruvate transaminase (SGPT), serum alkaline phosphatase (ALP), and biochemical parameter, that is, Bilirubin and total protein. Histopathology observation of liver sections was conducted. RESULTS: Phytochemical investigation revealed the presence of both phenolic and flavonoid groups in the extract in a significant amount. Antioxidant activity of the plant extract was observed in all models and percentage of inhibition was dose-dependent. Intoxicated with carbon tetrachloride, elevated the liver function enzymes, bilirubin, and suppressed the production of total protein. Pretreatment with the extract decreased the SGOT, SGPT, ALP, and bilirubin level significantly and increased the production level of total protein in a dose-dependent manner. The histopathological observation supported the hepatoprotective potentiality of the extract. CONCLUSION: The results indicate that fruit rind part of G. dulcis is nontoxic and the plant can utilize as an antioxidant source. The plant has a protective agent for liver damages and other diseases caused by free radicals. SUMMARY: In vitro antioxidant and in vivo hepatoprotective activity was evaluatedMethanolic extract was subjected to quantify the both phenolic and flavonoid contents. The extract showed the significant amount of both phenolic and flavonoids contents. The extract showed the free radical scavenging activity in 2,2-diphenyl-1-picrylhydrazine, 2,2'-azino-bis-3-ethylbenzothiazoline-6-sulfonic acid and nitrite oxide modelsThe extract was administrated against the carbon tetrachloride intoxicated animal models to evaluate the hepatoprotective activity by determining the level of liver marker enzymes such as serum glutamate pyruvate transaminase, SGOT, alkaline phosphatase and biochemical parameter such as protein and bilirubin. Pretreatment with the extract reversed the elevated level of the enzymes and increased the protein level in a dose-dependent mannerThe histopathological observations of the liver sections supported the hepatoprotective activity of the extractThe present study revealed that the Garcinia dulcis extract is a good candidature for preventing liver damage and other disease caused by free radicals. Abbreviations Used: DPPH: 2,2-diphenyl-1-picrylhydrazine, ABTS: 2,2'-azino-bis-3-ethylbenzothiazoline-6-sulfonic acid, SGOT: Serum glutamate oxaloacetate transaminase, SGPT: Serum glutamate pyruvate transaminase, ALP: Serum alkaline phosphatase.

Polarization resolved second harmonic microscopy.

Second harmonic (SH) microscopy has proven to be a powerful imaging modality over the past years due to its intrinsic advantages as a multiphoton process with endogenous contrast specificity, which allows pinhole-less optical sectioning, non-invasive observation, deep tissue penetration, and the possibility of easier signal detection at visible wavelengths. Depending on the relative orientation between the polarization of the incoming light and the second-order susceptibility of non-centrosymmetric structures, SH microscopy provides the unique capacity to probe the absolute molecular structure of a broad variety of biological tissues without the necessity for additional labeling. In addition, SH microscopy, when working with polarimetry, provides clear and in-depth insights on the details of molecular orientation and structural symmetry. In this review, the working principles of the polarization resolving techniques and the corresponding implements of SH microscopy are elucidated, with focus on Stokes vector based polarimetry. An overview of the advancements on SH anisotropy measurements are also presented. Specifically, the recent progresses on the following three topics in polarization resolved SH microscopy will be elucidated, which include Stokes vector resolving for imaging molecular structure and orientation, 3-D structural chirality by SH circular dichroism, and correlation with fluorescence lifetime imaging (FLIM) for in vivo wound healing diagnosis. The potentials and challenges for future researches in exploring complex biological tissues are also discussed.