Low Molecular Products Research Articles

Chemical composition, thermal profile and functional properties of grasshopper (Sphenarium purpurascens Ch.), cockroach (Nauphoeta cinerea) flours and their mixtures

SummaryThe use of insects as food is a hot topic today and the obtaining and comprehensive characterisation of insect meals is relevant since any scientific information represents progress towards the real use of these ‘new foods’. Therefore, the objective of this study was to evaluate the chemical composition of flours obtained from Sphenarium purpurascens Ch. and Nauphoeta cinerea, identify the main components and know their functional properties and thermal profile in flours and their mixtures to establish their potential applications as ingredients in the food and feed industry. The results revealed that flours and their mixtures can be used to increase the nutritional value of foods, especially thanks to their high protein content (35%–38%); in addition, their potential uses are numerous and range from baking, snacks, drinks and meat substitutes thanks to their techno‐functional and thermal properties. Regarding the thermal profile, this study presents results above 250 °C that have not been reported before for these insects and relate to the decomposition of acetylglucosamine units and the evaporation of low molecular weight volatile products that have not been reported for the flours of these insects. This study represents an advance in terms of the use of insects, pending attention to issues such as innocuity.

Distinct actors drive different mechanisms of biopolymer processing in polar marine coastal sediments.

Heterotrophic bacteria in the ocean initiate biopolymer degradation using extracellular enzymes that yield low molecular weight hydrolysis products in the environment, or by using a selfish uptake mechanism that retains the hydrolysate for the enzyme-producing cell. The mechanism used affects the availability of hydrolysis products to other bacteria, and thus also potentially the composition and activity of the community. In marine systems, these two mechanisms of substrate processing have been studied in the water column, but to date, have not been investigated in sediments. In surface sediments from an Arctic fjord of Svalbard, we investigated mechanisms of biopolymer hydrolysis using four polysaccharides and mucin, a glycoprotein. Extracellular hydrolysis of all biopolymers was rapid. Moreover, rapid degradation of mucin suggests that it may be a key substrate for benthic microbes. Although selfish uptake is common in ocean waters, only a small fraction (0.5%-2%) of microbes adhering to sediments used this mechanism. Selfish uptake was carried out primarily by Planctomycetota and Verrucomicrobiota. The overall dominance of extracellular hydrolysis in sediments, however, suggests that the bulk of biopolymer processing is carried out by a benthic community relying on the sharing of enzymatic capabilities and scavenging of public goods.

ДИСИПАЦІЯ ЕНЕРГІЇ НИЗЬКОМОЛЕКУЛЯРНИМИ РЕЧОВИНАМИ ПІД ЧАС ЗОНДУВАННЯ ЕЛЕКТРИЧНИМ ПОЛЕМ БАГАТОЖИЛЬНИХ КАБЕЛІВ АТОМНИХ ЕЛЕКТРИЧНИХ СТАНЦІЙ

A model of the piece-homogeneous interphase space of stranded cables is proposed, taking into account the influence of cracks oriented along the lines of force of the electric field. The cracks are filled with low molecular weight substances. The case of a probing electric field with a significant tangential component is considered.. The equivalent values of the tangent of the dielectric loss angle at various parameters of low molecular weight substances in the cracks of the polyethylene insulation of the conductor with a cross section of 2.5 mm2 were determined. The equivalent tangent of the angle of dielectric loss increases by (3-20) times when the dissipation of electrical energy by low molecular weight substances changes from 10% to 100% in a crack, which is 1% of the thickness of an intact section of polyethylene insulation. The distribution of the electric field for the general case of accumulation of low-molecular products in capillaries formed by slit-like gaps between isolated veins is obtained. A strong electric field in the smaller part of the gap between the insulated cores, which occurs at a core potential of 1 kV, contributes to the capillary absorption of decomposition products of both solid polyethylene insulation and water vapor from the atmosphere in the case of unshielded structures of multi-core cables. The asymmetric configuration of the probing electric field with a significant tangential component makes it possible to detect low-molecular decomposition products of solid polymer insulation, which are a sign of its aging. Differences experimentally observed in the value of tgδ with different schemes of examination of multi-core cables are related, to a greater extent, to the uneven distribution of substances dissipating electrical energy across the cross-section of the cable, and not to a change in the structure of the probing electric field. References 11, figure 5.

Multiphase reactions of proteins in the air: Oligomerization, nitration and degradation of bovine serum albumin upon ambient exposure

Proteins in atmospheric aerosol can react with atmospheric pollutants such as ozone (O3) and nitrogen dioxide (NO2) in the atmosphere via the reactions of oxidation, nitration, and cross-linking etc. Currently, the reactions have been more thoroughly studied in the laboratory but rarely investigated in the ambient environment. In this study, we used bovine serum albumin (BSA) as the model protein to conduct the exposure experiment in the ambient environment in southern China, an area with increasing oxidative capacity, to investigate the reactions of proteins in the atmosphere. We observed the occurrence of oligomerization, nitration and degradation of BSA upon exposure. The mass fraction of BSA monomer decreased by 5.86 ± 1.61% after exposure and those of dimers, trimers and higher oligomers increased by 1.04 ± 0.49%, 1.37 ± 0.74% and 3.40 ± 1.06%, respectively. Simultaneously, the nitration degrees of monomers, dimers, trimers and higher oligomers increased by 0.42 ± 0.15%, 0.53 ± 0.15%, 0.55 ± 0.28% and 2.15 ± 1.01%, respectively. The results show that oligomerization was significantly affected by O3 and temperature and nitration was jointly affected by O3, temperature and relative humidity, indicating the important role of atmospheric oxidants in the atmospheric reactions of protein. Atmospheric degradation of BSA was observed with the release of free amino acids (FAAs) such as glycine, alanine, serine and methionine. Glycine was the dominant FAA with a molar yield ranging from ∼8% to 33% for BSA. The estimated stoichiometric coefficient (α) of glycine is 10−7–10−6 for the degradation of BSA upon O3. Our observation suggests the occurrence of protein reactions in the oxidative ambient environment, leading to the production of nitrated products, oligomers and low molecular weight products such as peptides and FAAs. This study may deepen the current understanding of the atmospheric reaction mechanisms and reveal the influence of environmental factors in the atmosphere.

Digital microfluidics with distance-based detection - a new approach for nucleic acid diagnostics.

There is great enthusiasm for using loop-mediated isothermal amplification (LAMP) in point-of-care nucleic acid amplification tests (POC NAATs), as an alternative to PCR. While isothermal amplification techniques like LAMP eliminate the need for rapid temperature cycling in a portable format, these systems are still plagued by requirements for dedicated optical detection apparatus for analysis and manual off-chip sample processing. Here, we developed a new microfluidic system for LAMP-based POC NAATs to address these limitations. The new system combines digital microfluidics (DMF) with distance-based detection (DBD) for direct signal readout. This is the first report of the use of (i) LAMP or (ii) DMF with DBD - thus, we describe a number of characterization steps taken to determine optimal combinations of reagents, materials, and processes for reliable operation. For example, DBD was found to be quite sensitive to background signals from low molecular weight LAMP products; thus, a Capto™ adhere bead-based clean-up procedure was developed to isolate the desirable high-molecular-weight products for analysis. The new method was validated by application to detection of SARS-CoV-2 in saliva. The method was able to distinguish between saliva containing no virus, saliva containing a low viral load (104 genome copies per mL), and saliva containing a high viral load (108 copies per mL), all in an automated system that does not require detection apparatus for analysis. We propose that the combination of DMF with distance-based detection may be a powerful one for implementing a variety of POC NAATs or for other applications in the future.

Characterization of balsam sulfide via pyrolysis-gas chromatography-mass spectrometry/sulfur chemiluminescence detection and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry.

Balsam sulfide, produced by the reaction of turpentine/rosin and sulfur, has been used as one of the raw materials of liquid gold to decorate ceramics and tableware with thin gold film for more than 100years. The characterization of balsam sulfide is still insufficient because of its compositional complexity. In this study, balsam sulfide was characterized using pyrolysis-gas chromatography (Py-GC)-mass spectrometry (MS) and Py-GC with sulfur chemiluminescence detection (SCD) as well as matrix-assisted laser desorption/ionization time-of-flight MS (MALDI-TOFMS). Py-GC-MS/SCD analyses of balsam sulfide and its model samples revealed that the low molecular weight reaction products were mainly composed of compounds of one α-pinene unit reacted with 1-3 sulfur atoms. In the analysis of the high molecular weight components by MALDI-TOFMS, the products of two or three α-pinene units crosslinked by sulfur atoms were observed. It was found that dehydrogenation reaction proceeded gradually with the increase in the reaction time.

Carbohydrate-Containing Low Molecular Weight Metabolites of Microalgae.

Microalgae are abundant components of the biosphere rich in low molecular weight carbohydrate-containing natural products (glycoconjugates). Glycoconjugates take part in the processes of photosynthesis, provide producers with important biological molecules, influence other organisms and are known by their biological activities. Some of them, for example, glycosylated toxins and arsenicals, are detrimental and can be transferred via food chains into higher organisms, including humans. So far, the studies on a series of particular groups of microalgal glycoconjugates were not comprehensively discussed in special reviews. In this review, a special focus is given to glycoconjugates' isolation, structure determination, properties and approaches to search for new bioactive metabolites. Analysis of literature data concerning structures, functions and biological activities of ribosylated arsenicals, galactosylated and sulfoquinovosylated lipids, phosphoglycolipids, glycoside derivatives of toxins, and other groups of glycoconjugates was carried out and discussed. Recent studies were fundamental in the discovery of a great variety of new carbohydrate-containing metabolites and their biological activities in defining the role of microalgal viral infections in regulating microalgal blooms as well as in the detection of glycoconjugates with potent immunomodulatory properties. Those discoveries support growing interest in these molecules.

Modification of low-density lipoproteins by low molecular weight carbonyl products of free-radical oxidation of lipids and carbohydrates plays a key role in atherosclerotic lesion of the vascular wall and in endothelial dysfunction

The review presents evidence of the participation of low-density lipoproteins (LDL) modified by low molecular weight dicarbonyl compounds formed during freeradical oxidation of lipids (malondialdehyde) and carbohydrates in the development of endothelial dysfunction and atherosclerotic vascular lesions. The authors believe that it is they, and not oxidized (hydroperoxide-containing) LDL, that are the main factors of pathogenesis. The role of dicarbonyl-modified LDL in LOX-1 dependent induction of processes leading to the development of endothelial dysfunction is discussed. The results of studies proving that damage to the glycocalyx (a layer of macromolecules that prevent the development of endothelial dysfunction) covering the luminal surface of the endothelium is caused by hyperproduction of reactive oxygen species. Ways of pharmacological correction of free-radical oxidation processes are discussed, due to which inhibition of atherogenesis and diabetogenesis can be achieved.

Research on the kinetics and degradation pathways of gaseous acetic acid ester organics

ABSTRACT Designed to meet the specific needs of the printing industry exhaust gas emissions, this paper proposes a method for the degradation of gaseous acetic acid ester organics that is environmentally friendly, safe, and simple to use: micro-nano cavitation technology. In the process of using micro-nano cavitation technology to degrade acetic acid ester organics, the products in the degradation process were analyzed by gas chromatography-mass (GC-MS) spectrometry, and the degradation pathways of acetic acid ester organics were identified. Under high temperatures and high pressure caused by cavitation collapse, the C–C bond and C–O bond on the main chain of organic matter are cleaved to form low molecular products. Low-molecular intermediate products are continuously produced as the reaction advances, and these intermediate products are further oxidized and decomposed into carbon dioxide and water. Besides, the factors that influence the degradation rate of acetic acid ester organics were investigated. Based on the experimental data, acetic acid esters can degrade with the greatest efficiency when their initial concentration is 200 ± 50 mg/m3 and their treatment time is 20∼30 min. Moreover, the experiment was optimized using the response surface method. The results suggested that for an initial concentration of 155.544 mg/m3 and a reaction time of 21.961 min, the best degradation rate was 0.251 min−1. Micro-nano cavitation technology is a novel and promising technology for the degradation of volatile organic compounds, with a wide range of practical applications.

Cationic Tantalum Hydrides Catalyze Hydrogenolysis and Alkane Metathesis Reactions of Paraffins and Polyethylene.

Sulfated aluminum oxide (SAO), a high surface area material containing sulfate anions that behave like weakly coordinating anions, reacts with Ta(═CHtBu)(CH2tBu)3 to form [Ta(CH2tBu)2(O-)2][SAO] (1). Subsequent treatment with H2 forms Ta-H+ sites supported on SAO that are active in hydrogenolysis and alkane metathesis reactions. In both reactions Ta-H+ is more active than related neutral Ta-H sites supported on silica. This reaction chemistry extends to melts of high-density polyethylene (HDPE), where Ta-H+ converts 30% of a low molecular weight HDPE (Mn = 2.5 kg mol-1; Đ = 3.6) to low molecular weight paraffins under hydrogenolysis conditions. Under alkane metathesis conditions Ta-H+ converts this HDPE to a high MW fraction (Mn = 6.2 kDa; Đ = 2.3) and low molecular weight alkane products (C13-C32). These results show that incorporating charge as a design element in supported d0 metal hydrides is a viable strategy to increase the reaction rate in challenging reactions involving reorganization of C-C bonds in alkanes.

Characterization Techniques of Polymer Aging: From Beginning to End.

Polymers have been widely applied in various fields in the daily routines and the manufacturing. Despite the awareness of the aggressive and inevitable aging for the polymers, it still remains a challenge to choose an appropriate characterization strategy for evaluating the aging behaviors. The difficulties lie in the fact that the polymer features from the different aging stages require different characterization methods. In this review, we present an overview of the characterization strategies preferable for the initial, accelerated, and late stages during polymer aging. The optimum strategies have been discussed to characterize the generation of radicals, variation of functional groups, substantial chain scission, formation of low-molecular products, and deterioration in the polymers' macro-performances. In view of the advantages and the limitations of these characterization techniques, their utilization in a strategic approach is considered. In addition, we highlight the structure-property relationship for the aged polymers and provide available guidance for lifetime prediction. This review could allow the readers to be knowledgeable of the features for the polymers in the different aging stages and provide access to choose the optimum characterization techniques. We believe that this review will attract the communities dedicated to materials science and chemistry.

Direct pathway cloning and expression of the radiosumin biosynthetic gene cluster.

Radiosumins are a structurally diverse family of low molecular weight natural products that are produced by cyanobacteria and exhibit potent serine protease inhibition. Members of this family are dipeptides characterized by the presence of two similar non-proteinogenic amino acids. Here we used a comparative bioinformatic analysis to identify radiosumin biosynthetic gene clusters from the genomes of 13 filamentous cyanobacteria. We used direct pathway cloning to capture and express the entire 16.8 kb radiosumin biosynthetic gene cluster from Dolichospermum planctonicum UHCC 0167 in Escherichia coli. Bioinformatic analysis demonstrates that radiosumins represent a new group of chorismate-derived non-aromatic secondary metabolites. High-resolution liquid chromatography-mass spectrometry, nuclear magnetic resonance spectroscopy and chemical degradation analysis revealed that cyanobacteria produce a cocktail of novel radiosumins. We report the chemical structure of radiosumin D, an N-methyl dipeptide, containing a special Aayp (2-amino-3-(4-amino-2-cyclohexen-1-ylidene) propionic acid) with R configuration that differs from radiosumin A-C, an N-Me derivative of Aayp (Amyp) and two acetyl groups. Radiosumin C inhibits all three human trypsin isoforms at micromolar concentrations with preference for trypsin-1 and -3 (IC50 values from 1.7 μM to >7.2 μM). These results provide a biosynthetic logic to explore the genetic and chemical diversity of the radiosumin family and suggest that these natural products may be a source of drug leads for selective human serine proteases inhibitors.

Application of Rhodococcus jostii RHA1 glycolate oxidase as an efficient accessory enzyme for lignin conversion by bacterial Dyp peroxidase enzymes.

Lignin oxidation by bacterial dye-decolorizing peroxidase enzymes requires hydrogen peroxide as a co-substrate, an unstable and corrosive oxidant. We have identified a glycolate oxidase enzyme from Rhodococcus jostii RHA1 that can couple effectively at pH 6.5 with DyP peroxidase enzymes from Agrobacterium sp. or Comamonas testosteroni to oxidise lignin substrates without addition of hydrogen peroxide. Rhodococcus jostii RHA1 glycolate oxidase (RjGlOx) has activity for oxidation of a range of α-ketoaldehyde and α-hydroxyacid substrates, and is also active for oxidation of hydroxymethylfurfural (HMF) to furandicarboxylic acid. The combination of RjGlOx with Agrobacterium sp. DyP or C. testosteroni DyP generated new and enhanced amounts of low molecular weight aromatic products from organosolv lignin substrates, and was able to generate high-value products from treatment of lignin residue from cellulosic biofuel production, and from a polymeric humin substrate.

Cavitation technology for the production of bionutrients from coprolites and evaluation of their effectiveness

The article presents the results of the development of a technology and a production line for the production of bionutrients for use in crop production in order to increase plant resistance to adverse climatic factors and reduce doses of pesticides and mineral fertilizers. The technology is based on the bioconversion of organic animal waste into coprolites (biohumus), uses the nutritional activity of earthworms. and this is a kind of solid-phase fermentation, where the fermented mass is a heterophase system of the type: solid phase - liquid - gas. Compost as the basis for the vital activity of earthworms is prepared by accelerated biotechnological processing of animal manure and other organic materials. Nutrients are converted by worms into coprolites - forms available to plants.. The humus of coprolites differs in chemical composition from humus formed in the soil with the participation of microflora, in that polymerization processes of low molecular weight decomposition products of organic substances develop in the digestive canal of worms and humic acid molecules are formed. The resulting product was tested for effectiveness on winter rye crops. A noticeable increase in resistance to climatic factors and an increase in yield while maintaining high nutritional qualities is shown.

Periplasmic expression of Pseudomonas fluorescens peroxidase Dyp1B and site-directed mutant Dyp1B enzymes enhances polymeric lignin degradation activity in Pseudomonas putida KT2440

Expression of lignin-oxidising Pseudomonas fluorescens Dyp1B in the periplasm of Pseudomonas putida KT2440, using a tat fusion construct, was found to lead to enhanced whole cell activity for oxidation of DCP and polymeric lignin substrates. Four amino acid residues predicted to lie at the manganese ion binding site of Pseudomonas fluorescens peroxidase Dyp1B were investigated using site-directed mutagenesis. Mutants H127R and S223A showed 2-fold and 4-fold higher kcat for Mn(II) oxidation respectively, and mutant S223A showed 2-fold enhanced production of low molecular weight phenolic products from a polymeric soda lignin. The mutant Pfl Dyp1B genes were expressed as tat fusions to investigate their effect on lignin oxidation by P. putida KT2440.

Low allergenic fermented drink enriched with bioactive peptides of whey proteins

Whey protein hydrolysates are most often used in the production of hypoallergenic products, as low molecular weight proteolysis products do not cause allergic reactions in consumers. However, it has been found that whey proteins are not only a good source of amino acids, but also a large number of natural biologically active peptides (BAP). They are formed during normal digestion in the gastrointestinal tract. These natural BAP have a positive effect on various functions of the human body regardless of age. When using microbial and plant enzyme preparations, as well as hydrolysis conditions other than physiological, the formation of such biologically active peptides is impossible, and such products lose much of their biological value. The article highlights the results of research on the development of technology of low-allergenic fermented drink enriched with biologically active peptides of whey proteins. To develop the technology of beverage, we proposed to use micellar casein, which is a source of basic milk protein – casein and whey protein hydrolysate, obtained in physiological conditions, as a source of biologically active peptides from whey proteins. Whey protein hydrolysate was added to the product in two ways: to the normalized mixture before and after fermentation. The hydrolysate was added to the product in an amount corresponding to the whey protein content: 0.5 %; 0.7 %; 0.9 %; 1.1 %. It was found that the amount of hydrolysate introduced affects the duration of fermentation of the studied samples. It was noted that until the end of the recommended shelf life, the organoleptic characteristics of samples fermented with hydrolysate remained virtually unchanged, while the consistency of samples in which the hydrolysate was added after fermentation became slightly thinner compared to the day of production. It is also proved that the usage of whey protein hydrolysate helps to reduce the release of whey when filtering a fermented beverage during storage for seven days.

Mechanical Properties Evolution and Damage Mechanism of Kevlar Fiber under Ozone Exposure in Near-Space Simulation

The stratospheric airship, a long-term floating vehicle in near-space, has become a new hotspot in aerospace exploration. The airship’s envelope material is vulnerable to ozone exposure in near-space and degrades. This paper used typical Kevlar fiber as the research material for an ozone exposure experiment in a near-space simulated environment. The results showed that the elongation of the Kevlar fiber decreased and the elastic modulus increased after ozone exposure. The tensile strength of fiber decreased gradually with an increase in ozone concentration and exposure time. When ozone concentration increased from 0 pphm to 1000 pphm, the tensile strength of fiber decreased from 2397 MPa to 2059 MPa. With increasing ozone exposure time from 0 h to 1000 h under ozone concentration 1000 pphm, the tensile strength of fiber decreased from 2332 MPa to 1954 MPa. The hydrogen bonds and partial amide groups in the fiber structure were damaged, and the surface chemical functional groups of the Kevlar fiber were reassembled under ozone exposure. Low molecular weight oxidation products, including -COO- structures, formed on the surface of the Kevlar fiber. This work explores the ground simulation method in a near-space environment and enriches the service data of airship envelope materials.

Hypoxia and Hypoxic Exercise Induced Systemic Ros Disrupts the Redox Homeostasis in the Brain

Aim: We aimed to investigate the overall effects of hypoxic/normoxic exercise and hypoxia on redox status in both systemic circulation and brain, and to prove whether the variations in plasma redox status could affect the brain’s own redox homeostasis, vice versa. Methods: We designed hypoxic, normoxic exercise groups with their respective controls. We studied on redox status biomarkers i.e., hydroperoxide, low molecular weight thiols, protein thiols, total thiols, and advanced oxidation protein products in frontal cortex; total antioxidant and total oxidant status in the plasma. Results: There is no statistically significant difference observed in redox homeostasis of the brain after hypoxic and/or normoxic exercise or hypoxia itself with an increased systemic oxidant status. Conclusions: Live in hypoxia and exercise at normoxia might diminish the hazardous effect of ROS on the brain at hypoxia. From our findings, thiols, which are the indicators of the antioxidant power of the brain, are found to be protected in groups that are exposed to long-term hypoxia and exercise at normoxia. It might be possible that people who are exposed to hypoxia will be least affected by this damage with normoxic exercise, or even will not be affected at all. Keywords: Hypoxic exercise, Redox homeostasis, Brain, Plasma

МАТЕМАТИЧЕСКАЯ МОДЕЛЬ БИФУНКЦИОНАЛЬНОГО КАТАЛИЗАТОРА

A mathematical model of a bifunctional catalyst for the process of hydrocarbon isomerization is proposed, taking into account the composition of the reaction mixture, as well as the ratio of metallic and acid active centers. The elementary surface processes are considered: adsorption/desorption of reagents, dehydrogenation of paraffin into olefin, isomerization of olefins, cracking, hydrogenation of isoolefins and unsaturated low molecular weight cracking products, desorption of reaction products, coke formation, diffusion of adsorbed particles. The given amounts of desorbed reaction products are calculated. Snapshots of the catalyst surface were obtained.

Evaluation of salivary oxidative stress in oral lichen planus using malonaldehyde.

Background:Oral lichen planus is a chronic, mucocutaneous, inflammatory disease, with an unknown etiology. Reactive oxygen species and oxidative damage to the tissues might be the cause. Malonaldehyde (MDA), a low molecular weight end product of lipid peroxidation reaction is a suitable biomarker of endogenous DNA damage. monitoring the oxidant-antioxidant status of saliva may serve as an efficient marker of disease development in oral lichen planus patients.Aim and Objectives:To evaluate salivary oxidative stress in oral lichen planus subject using MDA and compare it with control subjects. Furthermore, to compare MDA levels in erosive and hypertrophic lichen planus.Materials and Methods:The current study is case–control study. Unstimulated salivary samples in the morning hours were taken from oral lichen planus subjects (n = 25) and controls subjects without any oral disease (n = 25). The saliva was centrifuged at 900 g for 10 min at a temperature of 4°C. Then, the entire filtrate was transferred to Eppendorf test tubes and frozen at–80°C until analysis. Salivary MDA was done through thiobarbituric acid reactive substance assay as per the protocol laid down by the manufacturer (Sigma Aldrich Lipid Peroxidation Assay Kit).Results:The data were expressed as the mean ± standard deviation and the statistical analysis was done using Student's t-test using SPSS version 21 IBM software. The salivary level of MDA was significantly higher than that of controls (P < 0.05).Conclusion:The higher level of MDA in patients with oral lichen planus suggests that free radicals and the resulting oxidative damage may be important in the pathogenesis of oral lichen planus lesions.