Direct measurement of the tryptophan-mediated photocleavage kinetics of a protein disulfide bond

An ultraviolet-driven rescue pathway for oxidative stress to eye lens protein human gamma-D crystallin

Human gamma-D crystallin (HGD) is a major constituent of the eye lens. Aggregation of HGD contributes to cataract formation, the leading cause of blindness worldwide. It is unique in its longevity, maintaining its folded and soluble state for 50-60 years. One outstanding question is the structural basis of this longevity despite oxidative aging and environmental stressors including ultraviolet radiation (UV). Here we present crystallographic structures evidencing a UV-induced crystallin redox switch mechanism. The room-temperature serial synchrotron crystallographic (SSX) structure of freshly prepared crystallin mutant (R36S) shows no post-translational modifications. After aging for nine months in the absence of light, a thiol-adduct (dithiothreitol) modifying surface cysteines is observed by low-dose SSX. This is shown to be UV-labile in an acutely light-exposed structure. This suggests a mechanism by which a major source of crystallin damage, UV, may also act as a rescuing factor in a finely balanced redox system.

Recovery of a highly reflective Bragg grating in DPDS-doped polymer optical fiber by thermal annealing

We report fiber Bragg grating manufacturing in poly(methyl methacrylate) (PMMA)-based polymer optical fibers (POFs) with a diphenyl disulfide (DPDS)-doped core by means of a 266 nm pulsed laser and the phase mask technique. Gratings were inscribed with different pulse energies ranging from 2.2 mJ to 2.7 mJ. For the latter, the grating reflectivity reached 91% upon 18-pulse illumination. Though the as-fabricated gratings decayed, they were recovered by post-annealing at 80°C for 1 day, after which they showed an even higher reflectivity of up to 98%. This methodology for the fabrication of highly reflective gratings could be applied for the production of high-quality tilted fiber Bragg gratings (TFBGs) in POFs for biochemical applications.

Nonclinical pharmacokinetics and biodistribution of VSV-GP using methods to decouple input drug disposition and viral replication

Viral replication places oncolytic viruses (OVs) in a unique niche in the field of drug pharmacokinetics (PK) as their self-amplification obscures exposure-response relationships. Moreover, standard bioanalytical techniques are unable to distinguish the input from replicated drug products. Here, we combine two novel approaches to characterize PK and biodistribution (BD) after systemic administration of vesicular stomatitis virus pseudotyped with lymphocytic choriomeningitis virus glycoprotein (VSV-GP) in healthy mice. First: to decouple input drug PK/BD versus replication PK/BD, we developed and fully characterized a replication-incompetent tool virus that retained all other critical attributes of the drug. We used this approach to quantify replication in blood and tissues and to determine its impact on PK and BD. Second: to discriminate the genomic and antigenomic viral RNA strands contributing to replication dynamics in tissues, we developed an in situ hybridization method using strand-specific probes and assessed their spatiotemporal distribution in tissues. This latter approach demonstrated that distribution, transcription, and replication localized to tissue-resident macrophages, indicating their role in PK and BD. Ultimately, our study results in a refined PK/BD profile for a replicating OV, new proposed PK parameters, and deeper understanding of OV PK/BD using unique approaches that could be applied to other replicating vectors.

Potent Inactivation of Human Respiratory Viruses Including SARS-CoV-2 by a Photoactivated Self-Cleaning Regenerative Antiviral Coating

The COVID-19 pandemic marks an inflection point in the perception and treatment of human health. Substantial resources have been reallocated to address the direct medical effects of COVID-19 and to curtail the spread of the virus. Thereby, shortcomings of traditional disinfectants, especially their requirement for regular reapplication and the related complications (e.g., dedicated personnel and short-term activity), have become issues at the forefront of public health concerns. This issue became especially pressing when infection-mitigating supplies dwindled early in the progression of the pandemic. In consideration of the constant threat posed by emerging novel viruses, we report a platform technology for persistent surface disinfection to combat virus transmission through nanomaterial-mediated, localized UV radiation emission. In this work, two formulations of Y2SiO5-based visible-to-UV upconversion nanomaterials were developed using a facile sol-gel-based synthesis. Our formulations have shown substantial antiviral activities (4 × 104 to 0 TCID50 units in 30 min) toward an enveloped, circulating human coronavirus strain (OC43) under simple white light exposure as an analogue to natural light or common indoor lighting. Additionally, we have shown that our two formulations greatly reduce OC43 RNA recovery from surfaces. Antiviral activities were further demonstrated toward a panel of structurally diverse viruses including enveloped viruses, SARS-CoV-2, vaccinia virus, vesicular stomatitis virus, parainfluenza virus, and Zika virus, as well as nonenveloped viruses, rhinovirus, and calicivirus, as evidence of the technology's broad antiviral activity. Remarkably, one formulation completely inactivated 105 infectious units of SARS-CoV-2 in only 45 min. The detailed technology has implications for the design of more potent, long-lived disinfectants and modified/surface-treated personal protective equipment targeting a wide range of viruses.

Detergent-Free Decellularization of Notochordal Cell-Derived Matrix Yields a Regenerative, Injectable, and Swellable Biomaterial

Porcine notochordal cell-derived matrix (NCM) has anti-inflammatory and regenerative effects on degenerated intervertebral discs. For its clinical use, safety must be assured. The porcine DNA is concerning because of (1) the transmission of endogenous retroviruses and (2) the inflammatory potential of cell-free DNA. Here, we present a simple, detergent-free protocol: tissue lyophilization lyses cells, and matrix integrity is preserved by limiting swelling during decellularization. DNA is digested quickly by a high nuclease concentration, followed by a short washout. Ninety-four percent of DNA was removed, and there was no loss of glycosaminoglycans or collagen. Forty-three percent of the total proteins remained in the decellularized NCM (dNCM). dNCM stimulated as much GAG production as NCM in nucleus pulposus cells but lost some anti-inflammatory effects. Reconstituted pulverized dNCM yielded a soft, shear-thinning biomaterial with a swelling ratio of 350% that also acted as an injectable cell carrier (cell viability >70%). dNCM can therefore be used as the basis for future biomaterials aimed at disc regeneration on a biological level and may restore joint mechanics by creating swelling pressure within the intervertebral disc.

Photolysis for the Removal and Transformation of Pesticide Residues During Food Processing: A State-of-the-Art Minireview

Pesticide residues are of great significant issue that exerted adverse effects on humans. There is a need for effective and non-toxic decontamination of pesticide residues during food processing. In this minireview, the recent advances in the degradation of pesticide residues by photolysis have been firstly described during food processing. The mechanisms of pesticide residues destruction by photolysis were discussed accordingly. Finally, applications of photolysis in the degradation of pesticide residues from beverages, fresh produce, and food rinse waste were also summarized.

Defining T Cell Subsets in Human Tonsils Using ChipCytometry

ChipCytometry is a multiplex imaging method that can be used to analyze either cell suspensions or tissue sections. Images are acquired by iterative cycles of immunostaining with fluorescently labeled Abs, followed by photobleaching, which allows the accumulation of multiple markers on a single sample. In this study, we explored the feasibility of using ChipCytometry to identify and phenotype cell subsets, including rare cell types, using a combination of tissue sections and single-cell suspensions. Using ChipCytometry of tissue sections, we successfully demonstrated the architecture of human palatine tonsils, including the B and T cell zones, and characterized subcompartments such as the B cell mantle and germinal center zone, as well as intrafollicular PD1-expressing CD4+ T cells. Additionally, we were able to identify the rare tonsillar T cell subsets, mucosal-associated invariant T (MAIT) and γδ-T cells, within tonsil tissue. Using single-cell suspension ChipCytometry, we further dissected human tonsillar T cell subsets via unsupervised clustering analysis as well as supervised traditional manual gating. We were able to show that PD1+CD4+ T cells are comprised of CXCR5+BCL6high follicular Th cells and CXCR5-BCL6mid pre-follicular Th cells. Both supervised and unsupervised analysis approaches identified MAIT cells in single-cell suspensions, confirming a phenotype similar to that of blood-derived MAIT cells. In this study, we demonstrate that ChipCytometry is a viable method for single-cell suspension cytometry and analysis, with the additional benefit of allowing phenotyping in a spatial context using tissue sections.

Photolysis kinetics of cartap and nereistoxin in water and tea beverages under irradiation of simulated sunlight and ultraviolet under laboratory conditions

Cartap applied widely in agricultural crops and tea plants is readily degraded into nereistoxin, resulting in a longer residual period and higher exposure risk to humans. The photolysis kinetics of cartap and nereistoxin in water and tea beverages was firstly investigated to explore the effect and mechanism of pesticide residue removal. Cartap and nereistoxin could be effectively photolyzed by ultraviolet and their photolysis rate increased with light intensity increasing. The photolysis percentage of cartap and nereistoxin in different solutions under ultraviolet irradiation of 200 W mercury lamp reached 81.8%-100.0% within 6 h. Relative to water solution, the water-soluble components in tea had an inhibition effect on the photodegradation of cartap and nereistoxin. This research provided a reference for the development of effective methods for the removal of cartap and its metabolite in water and tea beverages.

An Activatable Triplet Sensitizer Based on Triplet Electron Transfer and Its Application for Triplet-Triplet Annihilation Upconversion

Activatable triplet photosensitization refers to a photosentization process which can be turned on/off easily by external stimulus. Activatable triplet photosensitizations are normally achieved by interfering with the singlet excited state before the intersystem cross process (ISC), i.e., the formation process of triplet states of sensitizer. To achieve novel activatable triplet photosensitization, a disulfide-bridged porphyrin zinc(II) dyad (ZnPor-S-S-ZnPor) is prepared. Although fast ISC can be conducted in this dyad, an extremely low efficiency is obtained when employing this dyad as a triplet donor in triplet-triplet annihilation upconversion (TTA-UC) for sensitizing perylene. This is because of the presence of electron transfer from the triplet state of the porphyrin zinc(II) unit to the disulfide bond, which quickly quenches the triplet state of the porphyrin zinc(II) unit. This electron transfer process can be stopped by the cleavage of the disulfide bond in the presence of thiol, and TTA-UC efficiency can be enhanced significantly. Our result demonstrates for the first time that the disulfide bond can act as not only an easy cleavage linker but also a triplet electron acceptor. Furthermore, quenching the triplet states of sensitizer by triplet electron transfer provides an alternative protocol for designing activatable triplet sensitizers except controlling the singlet excited state before the ISC process.

Exploring long-range proton conduction, the conduction mechanism and inner hydration state of protein biopolymers

Proteins are the main proton mediators in various biological proton circuits. Using proteins for the formation of long-range proton conductors is offering a bioinspired approach for proton conductive polymers. One of the main challenges in the field of proton conductors is to explore the local environment within the polymers, along with deciphering the conduction mechanism. Here, we show that the protonic conductivity across a protein-based biopolymer can be hindered using straightforward chemical modifications, targeting carboxylate- or amine-terminated residues of the protein, as well as exploring the effect of surface hydrophobicity on proton conduction. We further use the natural tryptophan residue as a local fluorescent probe for the inner local hydration state of the protein surface and its tendency to form hydrogen bonds with nearby water molecules, along with the dynamicity of the process. Our electrical and spectroscopic measurements of the different chemically-modified protein materials as well as the material at different water-aprotic solvent mixtures result in our fundamental understanding of the proton mediators within the material and gaining important insights on the proton conduction mechanism. Our biopolymer can be used as an attractive platform for the study of bio-related protonic circuits as well as a proton conducting biopolymer for various applications, such as protonic transistors, ionic transducers and fuel cells.

Characterization of Ultraviolet Photoreactions in Therapeutic Peptides by Femtosecond Laser Catalysis and Mass Spectrometry

Peptides and proteins have diverse ultraviolet (UV) photoreaction pathways that can be activated by the energy of the UV photons absorbed. Simple light sources such as lamps are conventionally used to study these photoreactions in solution. This work provides a proof of concept that femtosecond laser technology can function as a highly potent UV source in rapidly conducting UV photostability studies of peptides. Correspondingly, sufficient quantities of photoproducts were generated in 1 min or less, allowing for identification of known and new photomodifications in the therapeutic peptides somatostatin-14 and arginine vasopressin. Identical photoproducts were also generated with a conventional continuous source. The major modifications included N-formylkynurenine, a cross-link between Trp and Phe, a Tyr product with an NH₃ loss, and disruption of an unstable disulfide bond into a complex mixture of a trisulfide bond and multiple scrambled dimeric products. In conclusion, femtosecond lasers are extremely useful to drive fast UV-induced reactions for high throughput screening of photostability and modifications in amino acid polymers.

Photochemical and Structural Studies on Cyclic Peptide Models

Ultra-violet (UV) irradiation has a significant impact on the structure and function of proteins that is supposed to be in relationship with the tryptophan-mediated photolysis of disulfide bonds. To investigate the correlation between the photoexcitation of Trp residues in polypeptides and the associated reduction of disulfide bridges, a series of small, cyclic oligopeptide models were analyzed in this work. Average distances between the aromatic side chains and the disulfide bridge were determined following molecular mechanics (MM) geometry optimizations. In this way, the possibility of cation–π interactions was also investigated. Molecular mechanics calculations revealed that the shortest distance between the side chain of the Trp residues and the disulfide bridge is approximately 5 Å in the cyclic pentapeptide models. Based on this, three tryptophan-containing cyclopeptide models were synthesized and analyzed by nuclear magnetic resonance (NMR) spectroscopy. Experimental data and detailed molecular dynamics (MD) simulations were in good agreement with MM geometry calculations. Selected model peptides were subjected to photolytic degradation to study the correlation of structural features and the photolytic cleavage of disulfide bonds in solution. Formation of free sulfhydryl groups upon illumination with near UV light was monitored by fluorescence spectroscopy after chemical derivatization with 7-diethylamino-3-(4-maleimidophenyl)-4-methylcoumarin (CPM) and mass spectrometry. Liquid cromatography-mass spectrometry (LC-MS) measurements indicated the presence of multiple photooxidation products (e.g., dimers, multimers and other oxidated products), suggesting that besides the photolysis of disulfide bonds secondary photolytic processes take place.

Proteomics Approach To Trace Site-Specific Damage in Aquatic Extracellular Enzymes During Photoinactivation

Extracellular enzymes are major drivers of biogeochemical nutrient and carbon cycling in surface water. While photoinactivation is regarded as a major inactivation process of these enzymes, the underlying molecular changes have received little attention. This study demonstrates how light exposure leads to a rapid loss of phosphatase, aminopeptidase, and glucosidase activities of biofilm samples and model enzymes. Here, an optimized proteomics approach allowed simultaneous observation of inactivation and molecular changes. Site-specific fingerprints of degradation kinetics have been generated and visualized in the three-dimensional proteins. Oxidation of tryptophan, the chromophoric target, initiated secondary reactions. Evidence was obtained that tyrosine residues act as intramolecular antioxidants, reflected in decelerated decay of tryptophan-containing peptides and enhanced decay of tyrosine-containing peptides. In addition, subsequent methionine oxidation and disulfide reduction contribute to heterogeneous photodamage. The proximity to tryptophan residues explains >95% of the photodamage across the protein structures. The presence of redox active organic matter or a model antioxidant in solution quenched not only photoinactivation and tryptophan oxidation but also all subsequent damage. The developed analytical approach can be applied to other research questions in environmental sciences where site-specific damage in a protein is essential.

Copper-Mediated Polymerization without External Deoxygenation or Oxygen Scavengers

As a method for overcoming the challenge of rigorous deoxygenation in copper-mediated controlled radical polymerization processes [e.g., atom-transfer radical polymerization (ATRP)], reported here is a simple Cu0 -RDRP (RDRP=reversible deactivation radical polymerization) system in the absence of external additives (e.g., reducing agents, enzymes etc.). By simply adjusting the headspace of the reaction vessel, a wide range of monomers, namely acrylates, methacrylates, acrylamides, and styrene, can be polymerized in a controlled manner to yield polymers with low dispersities, near-quantitative conversions, and high end-group fidelity. Significantly, this approach is scalable (ca. 125 g), tolerant to elevated temperatures, compatible with both organic and aqueous media, and does not rely on external stimuli which may limit the monomer pool. The robustness and versatility of this methodology is further demonstrated by the applicability to other copper-mediated techniques, including conventional ATRP and light-mediated approaches.

Ultra-fast polymer optical fibre Bragg grating inscription for medical devices

We report the extraordinary result of rapid fibre Bragg grating inscription in doped polymer optical fibres based on polymethyl methacrylate in only 7 ms, which is two orders of magnitude faster than the inscription times previously reported. This was achieved using a new dopant material, diphenyl disulphide, which was found to enable a fast, positive refractive index change using a low ultraviolet dose. These changes were investigated and found to arise from photodissociation of the diphenyl disulphide molecule and subsequent molecular reorganization. We demonstrate that gratings inscribed in these fibres can exhibit at least a 15 times higher sensitivity than silica glass fibre, despite their quick inscription times. As a demonstration of the sensitivity, we selected a highly stringent situation, namely, the monitoring of a human heartbeat and respiratory functions. These findings could permit the inscription of fibre Bragg gratings during the fibre drawing process for mass production, allowing cost-effective, single-use, in vivo sensors among other potential uses.