Visible light neutralizes the effect produced by ultraviolet radiation in proteins

Probing silver nanoparticle mediated mitigation of UV-photolysis in proteins by electrical impedance analysis

The dynamic equilibrium between an array of molecular forces precisely organizes the native structure of the protein. The charge on the protein, an interconnected network continuum, is crucial in determining its secondary and tertiary structure. The photolysis of the protein by ultraviolet (UV) light occurs by generating reactive oxygen intermediates from the interaction of matter and light. Herein, we have investigated the photolysis of the protein and its prevention by the pre-treatment with silver nanoparticle (AgNP) using non-faradaic electrical impedance spectroscopy (Nf-EIS). Five microliters of protein solution are used to measure its impedimetric parameters via Nf-EIS. The photoionization process sparks off an altered surface charge continuum of the protein molecules in tandem with the genesis of solvated electrons and protons, spurring an upward shift in conductivity. The AgNP pre-treatment has reduced the damaging effects of the UV radiation, which is reflected as lesser conductivity in contrast to the photolyzed protein solution. Raman Spectroscopy and circular dichroism tests affirm the trend of Nf-EIS results. These results show that Nf-EIS can evaluate protein structure analysis utilized in quality assurance and toxicity analysis for biologics.

Preparation of injectable hydrophilic dextran/AgNPs nanocomposite product: White light active biomolecules as an antitumor agent

Incidence of various cancers including melanoma continues to rise worldwide. While treatment options have expanded in the recent years, the benefit of these treatments suffer from short period of duration for many patients. Hence, new treatment options are highly desired. Here, we propose a method combining a Dextran/reactive-copolymer/AgNPs nanocomposite and a harmless visible light approach to obtain a plasma substitute carbohydrate-based nanoproduct (D@AgNP) that shows strong antitumor activity. Light-driven polysaccharide-based nanocomposite provided essential conditions for extra small (8-12nm) AgNPs capping with subsequent specific self-assembly into spherical-like cloud nanostructures. Obtained biocompatible D@AgNP are stable over six months at room temperature and demonstrated absorbance peak at 406 nm. New formulated nanoproduct revealed efficient anticancer properties against A375 with IC50 0.0035 mg/mL following 24-h incubation; complete cell death is achieved at 0.001 mg/mL and 0.0005 mg/mL by 24- and 48-h time points, respectively. SEM examination shows that D@AgNP altered the shape of the cell structure and damaged the cell membrane. TEM finding shows that D@AgNP are mostly localized at vesicles such as the endosomes, lysosomes and mitochondria. It is anticipated that the introduced new method serves as the cornerstone for improving the generation of biocompatible hydrophilic carbohydrate-based anticancer drugs.

Light-Driven Conversion of Silicon Nitride Nanopore to Nanonet for Single-Protein Trapping Analysis

The single-molecule technique for investigation of an unlabeled protein in solution is very attractive but with great challenges. Nanopore sensing as a label-free tool can be used for collecting the structural information of individual proteins, but currently offers only limited capabilities due to the fast translocation of the target. Here, a reliable and facile method is developed to convert the silicon nitride nanopore to a stable nanonet platform for single-entity sensing by electrophoretic or electroosmotic trapping. A nanonet is fabricated based on a material reorganization process caused by electron-beam and light-irradiation treatment. Using protein molecules as a model, it is revealed that the solid-state nanonet can produce collision and trapping flipping signals of the protein, which provides more structural information than traditional nanopore sensing. More importantly, thanks to the excellent stability of the solid-state silicon nitride nanonet, it is demonstrated that the ultraviolet-light-irradiation-induced structural-change process of an individual protein can be captured. The developed nanonet supplies a robust platform for single-entity studies but is not limited to proteins.

MYC amplifies gene expression through global changes in transcription factor dynamics

The MYC oncogene has been studied for decades, yet there is still intense debate over how this transcription factor controls gene expression. Here, we seek to answer these questions with an in vivo readout of discrete events of gene expression in single cells. We engineered an optogenetic variant of MYC (Pi-MYC) and combined this tool with single-molecule RNA and protein imaging techniques to investigate the role of MYC in modulating transcriptional bursting and transcription factor binding dynamics in human cells. We find that the immediate consequence of MYC overexpression is an increase in the duration rather than in the frequency of bursts, a functional role that is different from the majority of human transcription factors. We further propose that the mechanism by which MYC exerts global effects on the active period of genes is by altering the binding dynamics of transcription factors involved in RNA polymerase II complex assembly and productive elongation.

Brought to Light: How Ultraviolet Disinfection Can Prevent the Nosocomial Transmission of COVID-19 and Other Infectious Diseases

The novel coronavirus disease 2019 (COVID-19) pandemic has brought to light the role of environmental hygiene in controlling disease transmission. Healthcare facilities are hot spots for infectious pathogens where physical distancing and personal protective equipment (PPE) are not always sufficient to prevent disease transmission. Healthcare facilities need to consider adjunct strategies to prevent transmission of infectious pathogens. In combination with current infection control procedures, many healthcare facilities are incorporating ultraviolet (UV) disinfection into their routines. This review considers how pathogens are transmitted in healthcare facilities, the mechanism of UV microbial inactivation and the documented activity of UV against clinical pathogens. Emphasis is placed on the severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) as well as multidrug resistant organisms (MDROs) that are commonly transmitted in healthcare facilities. The potential benefits and limitations of UV technologies are discussed to help inform healthcare workers, including clinical studies where UV technology is used in healthcare facilities.

Circadian Regulation of Mitochondrial Dynamics in Retinal Photoreceptors

Energy expenditure and metabolism in the vertebrate retina are under circadian control, as we previously reported that the overall retinal ATP content and various signaling molecules related to metabolism display daily or circadian rhythms. Changes in the fission and fusion process of mitochondria, the major organelles producing ATP, in retinal photoreceptors are largely dependent on light exposure, but whether mitochondrial dynamics in photoreceptors and retinal neurons are under circadian control is not clear. Herein, we investigated the possible roles of circadian oscillators in regulating mitochondrial dynamics, mitophagy, and redox states in the chicken retina and mammalian photoreceptors. After entrainment to 12:12-h light-dark (LD) cycles for several days followed by free-running in constant darkness (DD), chicken embryonic retinas and cone-derived 661W cells were collected in either LD or DD at 6 different zeitgeber time (ZT) or circadian time (CT) points. The protein expression of mitochondrial dynamin-related protein 1 (DRP1), mitofusin 2 (MFN2), and PTEN-induced putative kinase 1 (PINK1) displayed daily rhythms, but only DRP1 was under circadian control in the chicken retinas and cultured 661W cells. In addition, cultured chicken retinal cells responded to acute oxidative stress differently from 661W cells. Using pMitoTimer as a mitochondrial redox indicator, we found that the mitochondrial redox states were more affected by light exposure than regulated by circadian oscillators. Thus, this study demonstrates that the influence of cyclic lights might outweigh the circadian regulation of complex mitochondrial dynamics in light-sensing retinal cells.