Modification Of Macromolecules Research Articles

Association between advanced glycation end-products and fall risk in older adults: The Yakumo Study.

Advanced glycation end-products (AGEs) are irreversibly and heterogeneously formed compounds during the non-enzymatic modification of macromolecules, such as proteins. Aging and lifestyle habits, such as high-fat and high-protein diets, and smoking, promote AGEs accumulation. This study aimed to investigate the relationship between fall risk and AGEs in community-dwelling older adults. This cross-sectional study included patients from the 2022 Yakumo Study who were evaluated for fall risk index 5-items version, locomotive syndrome stage and AGEs. AGEs were evaluated using Skin autofluorescence (SAF) measured by the AGE reader (DiagnOptics Technologies BV, Groningen, the Netherlands). We divided the participants into two groups according to the presence or absence of fall risk (fall risk index 5-items version ≥6 or not), and investigated the factors associated with fall risk. The fall risk group had a higher age and SAF, and a higher proportion of locomotive syndrome stage >2 than the without fall risk group in patients aged ≥65 years (P < 0.01). The multivariate logistic regression analysis after adjustment of age, sex and body mass index showed that locomotive syndrome stage ≥2 and SAF were independent associators of fall risk in older adults (odds ratio 3.26, P < 0.01, odds ratio 2.96, P < 0.05, respectively). The optimal cutoff value of the SAF for fall risk was 2.4 (area under the curve 0.631; 95% CI 0.53-0.733; sensitivity 0.415; specificity 0.814; P < 0.05). The accumulation of AGEs in skin tissues can be used to screen for fall risk comprehensively. Geriatr Gerontol Int 2024; 24: 517-522.

Intracellular Staphylococcus aureus infection in human osteoblasts: circRNA expression analysis

Staphylococcus aureus (S. aureus) has the ability to invade human cortical bones and cause intracellular infections in osteoblasts, which may lead to a long-term infection that is difficult to eliminate. It is critical to identify the underlying mechanisms of the osteoblast response to the intracellular S. aureus. More recently, multiple circular RNA (circRNA) functions have been identified, including serving as protein scaffolds or miRNA sponges and being translated into polypeptides. The role that circRNAs play in intracellular S. aureus infection of osteoblasts has not, to our knowledge, been investigated. Here, we established an intracellular infection model of S. aureus in osteoblasts and compared the circRNA expression of osteoblasts between the infected and control groups using RNA sequencing technology, by which a significant difference was found. In total, 117 upregulated and 125 down-regulated differentially expressed circRNAs (DEcircRNAs) were identified, and reverse transcription-quantitative PCR was employed to validate the results of RNA sequencing. Gene Ontology and Kyoto Encyclopedia of Genes and Genomes pathway analyses demonstrated that DEcircRNAs were enriched in processes associated with macromolecule modification, cellular component organization or biogenesis, and intracellular non-membrane-bound organelles. Finally, a potentially important network of circRNA-miRNA-mRNA based on the DEcircRNAs was constructed. Overall, this study revealed the circRNA expression profile of human osteoblasts infected by intracellular S. aureus for the first time, and identified the circRNAs that may contribute to the pathogenesis of infectious diseases caused by intracellular S. aureus infection in human osteoblasts.

Redox imbalance and metabolic defects in the context of Alzheimer disease.

Redox reactions play a critical role for intracellular processes, including pathways involved in metabolism and signaling. Reactive oxygen species (ROS) act either as second messengers or generators of protein modifications, fundamental mechanisms for signal transduction. Disturbance of redox homeostasis is associated with many disorders. Among these, Alzheimer's disease is a neurodegenerative pathology that presents hallmarks of oxidative damage such as increased ROS production, decreased activity of antioxidant enzymes, oxidative modifications of macromolecules, and changes in mitochondrial homeostasis. Interestingly, alteration of redox homeostasis is closely associated with defects of energy metabolism, involving both carbohydrates and lipids, the major energy fuels for the cell. As the brain relies exclusively on glucose metabolism, defects of glucose utilization represent a harmful event for the brain. During aging, a progressive perturbation of energy metabolism occurs resulting in brain hypometabolism. This condition contributes to increase neuronal cell vulnerability ultimately resulting in cognitive impairment. The current review discusses the crosstalk between alteration of redox homeostasis and brain energy defects that seems to act in concert in promoting Alzheimer's neurodegeneration.

Research progress on chemical modifications of tyrosine residues in peptides and proteins.

The chemical modifications (CMs) of protein is an important technique in chemical biology, protein-based therapy, and material science. In recent years, there has been rapid advances in the development of CMs of peptides and proteins, providing new approaches for peptide and protein functionalization, as well as drug discovery. In this review, we highlight the methods for chemically modifying tyrosine (Tyr) residues in different regions, offering a comprehensive exposition of the research content related to Tyr modification. This review summarizes and provides an outlook on Tyr residue modification, aiming to offer readers assistance in the site-selective modification of macromolecules and to facilitate application research in this field.

Characterization of the basic leucine zipper transcription factor family of Neoporphyra haitanensis and its role in acclimation to dehydration stress

BackgroundNeoporphyra haitanensis, a major marine crop native to southern China, grows in the harsh intertidal habitats of rocky coasts. The thallus can tolerate fluctuating and extreme environmental stresses, for example, repeated desiccation/rehydration due to the turning tides. It is also a typical model system for investigating stress tolerance mechanisms in intertidal seaweed. The basic leucine zipper (bZIP) transcription factors play important roles in the regulation of plants’ responses to environmental stress stimuli. However, little information is available regarding the bZIP family in the marine crop Nh. haitanensis.ResultsWe identified 19 bZIP genes in the Nh. haitanensis genome and described their conserved domains. Based on phylogenetic analysis, these 19 NhhbZIP genes, distributed unevenly on the 11 superscaffolds, were divided into four groups. In each group, there were analogous exon/intron numbers and motif compositions, along with diverse exon lengths. Cross-species collinearity analysis indicated that 17 and 9 NhhbZIP genes were orthologous to bZIP genes in Neopyropia yezoensis and Porphyra umbilicalis, respectively. Evidence from RNA sequencing (RNA-seq) data showed that the majority of NhhbZIP genes (73.68%) exhibited transcript abundance in all treatments. Furthermore, genes NN 2, 4 and 5 showed significantly altered expression in response to moderate dehydration, severe dehydration, and rehydration, respectively. Gene co-expression network analysis of the representative genes was carried out, followed by gene set enrichment analysis. Two NhhbZIP genes collectively responding to dehydration and rehydration and their co-expressing genes mainly participated in DNA repair, DNA metabolic process, and regulation of helicase activity. Two specific NhhbZIP genes responding to severe dehydration and their corresponding network genes were mainly involved in macromolecule modification, cellular catabolic process, and transmembrane transport. Three specific NhhbZIP genes responding to rehydration and their co-expression gene networks were mainly involved in the regulation of the cell cycle process and defense response.ConclusionsThis study provides new insights into the structural composition, evolution, and function of the NhhbZIP gene family. Our results will help us to further study the functions of bZIP genes in response to dehydration and rehydration in Nh. haitanensis and improve Nh. haitanensis in southern China.

Adaptogen Technology for Skin Resilience Benefits

(1) Background: Skin undergoes constant changes, providing capabilities to repair and renovate its constituents once damaged and a fundamental shield to contrast environmental stress. Nevertheless, environmental stressors may overcome the skin’s protective potential inducing premature aging and accelerating the appearance of anaesthetic age-related skin aspects. Ultraviolet radiation (UVR) and pollutants (particulate matters, PAHs) contribute to skin aging and functional decline inducing harmful oxidative modifications of macromolecules and stress-related skin disorders. Innovative approaches to preserve skin are needed. (2) Methods: Skin keratinocytes were treated (or not) with a combination of ingredients (Lactobacillus plantarum extract, Withania somnifera root extract and Terminalia ferdinandiana fruit extract; “MIX”) in the presence or absence of stress (oxidative stress or pollution). The effects of the MIX adaptogen technology on (a) cellular resilience, (b) the regulation of cellular functions and (c) regeneration of skin were disclosed through expression proteomics and bioinformatics analyses first, and then through focused evaluations of protein carbonylation as a hallmark of oxidative stress’ deleterious impact and mitochondrial activity. (3) Results: The deleterious impact of stressors was evidenced, as well as the beneficial effects of the MIX through (a) mitochondrial activity preservation, (b) the “vigilance” of the NRF2 pathway activation, (c) NADPH production and protein homeostasis improvements, (d) preserving skin regeneration function and I the contrasting stress-induced oxidation (carbonylation) of mitochondrial and nuclear proteins. (4) Conclusions: The effects of the MIX on increasing cell adaptability and resilience under stress suggested a beneficial contribution in precision cosmetics and healthy human skin by acting as an adaptogen, an innovative approach that may be employed to improve resistance to harmful stress with a potential favourable impact on skin homeostasis.

The Carcinogenic Potential of Bisphenol A in the Liver Based on Transcriptomic Studies.

Bisphenol A (BPA) is an environmental toxin widely used in the production of polycarbonate plastics. A correlation exists between BPA tissue contamination and the occurrence of pathological conditions, including cancer. First-passage detoxification of high BPA amounts in the liver promotes hepatotoxicity and morphological alterations of this organ, but there is a lack of knowledge about the molecular mechanisms underlying these phenomena. This prompted us to investigate changes in the liver transcriptomics of 3-month-old female mice exposed to BPA (50 mg/kg) in drinking water for 3 months. Five female mice served as controls. The animals were euthanized, the livers were collected, and RNA was extracted to perform RNA-seq analysis. The multistep transcriptomic bioinformatics revealed 120 differentially expressed genes (DEGs) in the BPA-exposed samples. Gene Ontology (GO) annotations indicated that DEGs have been assigned to many biological processes, including "macromolecule modification" and "protein metabolic process". Several of the revealed DEGs have been linked to the pathogenesis of severe metabolic liver disorders and malignant tumors, in particular hepatocellular carcinoma. Data from this study suggest that BPA has a significant impact on gene expression in the liver, which is predictive of the carcinogenic potential of this compound in this organ.

Nutritional and metabolic control of germ cell fate through O-GlcNAc regulation.

Fate determination of primordial germ cells (PGCs) is regulated in a multi-layered manner, involving signaling pathways, epigenetic mechanisms, and transcriptional control. Chemical modification of macromolecules, including epigenetics, is expected to be closely related with metabolic mechanisms but the detailed molecular machinery linking these two layers remains poorly understood. Here, we show that the hexosamine biosynthetic pathway controls PGC fate determination via O-linked β-N-acetylglucosamine (O-GlcNAc) modification. Consistent with this model, reduction of carbohydrate metabolism via a maternal ketogenic diet that decreases O-GlcNAcylation levels causes repression of PGC formation in vivo. Moreover, maternal ketogenic diet intake until mid-gestation affects the number of ovarian germ cells in newborn pups. Taken together, we show that nutritional and metabolic mechanisms play a previously unappreciated role in PGC fate determination.

Synthesis and Applications of Hybrid Polymer Networks Based on Renewable Natural Macromolecules.

Macromolecules obtained from renewable natural sources are gaining increasing attention as components for a vast variety of sustainable polymer-based materials. Natural raw materials can facilitate continuous-flow production due to their year-round availability and short replenishment period. They also open new opportunities for chemists and biologists to design and create "bioreplacement" and "bioadvantaged" polymers, where complex structures produced by nature are being modified, upgraded, and utilized to create novel materials. Bio-based macromonomers are expected not only to compete with but to replace some petroleum-based analogs, as well. The development of novel sustainable materials is an ongoing and very dynamic process. There are multiple strategies for transforming natural macromolecules into sophisticated value-added products. Some methods include chemical modification of macromolecules, while others include blending several components into one new system. One of the most promising approaches for incorporating renewable macromolecules into new products is the synthesis of hybrid networks based on one or more natural components. Each one has unique characteristics, so its incorporation into a network brings new sustainable materials with properties that can be tuned according to their end-use. This article reviews the current state-of-the-art and future potential of renewable natural macromolecules as sustainable building blocks for the synthesis and use of hybrid polymer networks. The most recent advancements and applications that involve polymers, such as cellulose, chitin, alginic acid, gellan gum, lignin, and their derivatives, are discussed.

Improvement of some techno-functional properties of aquafaba by pre-fermentation with Lactobacillus plantarum MA2

Recently, modification of macromolecules in food products has gained special interest to increase their utilization during food processing. In this respect, the aim of this study was to modify chickpea aquafaba by using a pre-fermentation process with Lactobacillus plantarum MA2 for 3, 6 and 9 h and physicochemical and techno-functional of the modified aquafaba samples were investigated. The results showed that fermentation significantly improved foaming expansion, solubility and stability, with shorter fermentation times resulting in lower stability. Emulsifying properties were also improved by fermentation, with the 3-h fermentation sample having significantly higher emulsion stability. The protein profiles of chickpea during fermentation were analyzed using SDS-PAGE, and changes in the secondary structure of proteins were examined using FTIR spectroscopy. The major bands of low-molecular weight proteins were observed between 6.5 and 66 kDa, with minor bands between 66 and 200 kDa distributed similarly across all samples. The longer period of fermentation resulted in the formation of higher amounts of lower peptides. FTIR spectroscopy revealed changes in the secondary structure of proteins during fermentation, particularly in the amide-I region, which is sensitive to changes in the secondary structures of proteins consisting of layers such as the α-helix, β-turn, β-sheet, and random coil. Rheological properties of the aquafaba solution were investigated and all solutions showed shear thinning behavior while Ostwald de Waele model well described the flow behavior. The findings of the study highlighted that fermentation can be used as safe, eco-friendly, and green method for improving techno-functional characteristics of chickpea aquafaba.

Redox control of tumor cell apoptosis during hypoxia

Currently, close attention is paid to studies aimed at searching for redox-sensitive targets for the regulation of tumor cell death. Tumor growth is characterized by impaired cell proliferation, differentiation, and apoptosis against the background of oxidative stress. Hypoxia contributes to the formation of mitochondrial dysfunction and acts as an additional factor that exacerbates oxidative stress in the tumor cell. Reactive oxygen species are general damaging factors, however, they can act as modulators of processes such as reception, intracellular signaling, proliferation, apoptosis, while taking part in the functioning of the cell redox system and contributing to the oxidative modification of macromolecules. One of the possible reasons for the activation of the production of reactive oxygen species is the low content of O2 in the cell, the final electron acceptor to ensure the functioning of the enzymes of the mitochondrial respiratory chain. The glutathione system makes a significant contribution to maintaining the balance between prooxidants and antioxidants in the cell. The role of this system is justified by the reduction potential of glutathione, which, acting as an acceptor of hydroxyl ions and singlet oxygen, significantly reduces the cytotoxic and damaging effects of reactive oxygen species. At the same time, it serves as a coenzyme for glutathione-dependent enzymes, which play a leading role not only in providing antioxidant processes, but also in maintaining the thiol disulfide balance. Hypoxia, which acts as a factor in the activation of free radical oxidation against the background of proliferation and apoptosis dysregulation, contributes to the formation of resistance of tumor cells to chemotherapeutic effects. In light of this, the importance of studying the redox-dependent mechanisms involved in the regulation and implementation of tumor cell death under insufficient oxygen supply becomes obvious, which is necessary for the development of personalized antitumor therapy. The article presents a review of modern literature, including the results of our own research, on the role of the thiol disulfide system and oxidatively modified proteins in the redox regulation of proliferation and apoptotic death of tumor cells, including under hypoxic conditions.

Effect of Functional Nanoporous TiO2 Film Obtained on Ti6Al4V Implant Alloy to Improve Resistance in Biological Solution for Inflammatory Conditions.

The metallic titanium-based biomaterials are sensitive to corrosion-induced degradation in biological fluids in the presence of inflammatory conditions containing reactive oxygen species (ROS). Excess ROS induces oxidative modification of cellular macromolecules, inhibits protein function, and promotes cell death. In addition, ROS could promote implant degradation by accelerating the corrosive attack of biological fluids. The functional nanoporous titanium oxide film is obtained on titanium alloy to study the effect on implant reactivity in biological fluid with reactive oxygen species such as hydrogen peroxide, which are present in inflammations. The TiO2 nanoporous film is obtained by electrochemical oxidation at high potential. The untreated Ti6Al4V implant alloy and nanoporous titanium oxide film are comparatively evaluated for corrosion resistance in biological solution by Hank's and Hank's doped with hydrogen peroxide by electrochemical methods. The results showed that the presence of the anodic layer significantly improved the resistance of the titanium alloy to corrosion-induced degradation in biological solutions under inflammatory conditions.

Modification of Macromolecules of Polyimide Films by Electron Irradiation.

New polymeric materials formation by controlling their properties is the primary and most challenging problem in developing a methodology for synthesizing a chosen technology and its use. The combined effect of high-energy electron radiation and tensile stress will cause a decrease in crystallinity and the breakage of chemical bonds in polyimide film macromolecules and is a new approach in their production technology. The effect of uniaxial tension and electron irradiation on the modification of polyimide film at room temperature was studied. Irradiation of the films caused an increase in the intensity of the IR spectrum by ~2-6 times and an increase in the width of the bands. The intensity in the range of 1700-3500 cm-1 increased, indicating an increase in the content of radicals as a result of irradiation. The amplitudes of the electron paramagnetic resonance signal from non-irradiated films increased from 3 × 103 to 5 × 103 as a result of uniaxial tension to fracture, indicating an increase in radicals in the material. The lines of the electron paramagnetic resonance spectrum shifted from 3475.0 cm-1 to 3512.5 cm-1, with a simultaneous decrease in the signal's amplitude from 6 ×103 to 4 × 103, as a result of the electron irradiation of the films, followed by their subjection to tension. This was due to a decrease in the concentration of the radicals of the =N-H and -N-H2 groups until their disappearance and the formation of new ones.

Advances in the Synthesis of Preceramic Polymers for the Formation of Silicon-Based and Ultrahigh-Temperature Non-Oxide Ceramics.

Preceramic polymers (PCPs) are a group of specialty macromolecules that serve as precursors for generating inorganics, including ceramic carbides, nitrides, and borides. PCPs represent interesting synthetic challenges for chemists due to the elements incorporated into their structure. This group of polymers is also of interest to engineers as PCPs enable the processing of polymer-derived ceramic products including high-performance ceramic fibers and composites. These finished ceramic materials are of growing significance for applications that experience extreme operating environments (e.g., aerospace propulsion and high-speed atmospheric flight). This Review provides an overview of advances in the synthesis and postpolymerization modification of macromolecules forming nonoxide ceramics. These PCPs include polycarbosilanes, polysilanes, polysilazanes, and precursors for ultrahigh-temperature ceramics. Following our review of PCP synthetic chemistry, we provide examples of the application and processing of these polymers, including their use in fiber spinning, composite fabrication, and additive manufacturing. The principal objective of this Review is to provide a resource that bridges the disciplines of synthetic chemistry and ceramic engineering while providing both insights and inspiration for future collaborative work that will ultimately drive the PCP field forward.

The DarT/DarG Toxin–Antitoxin ADP-Ribosylation System as a Novel Target for a Rational Design of Innovative Antimicrobial Strategies

The chemical modification of cellular macromolecules by the transfer of ADP-ribose unit(s), known as ADP-ribosylation, is an ancient homeostatic and stress response control system. Highly conserved across the evolution, ADP-ribosyltransferases and ADP-ribosylhydrolases control ADP-ribosylation signalling and cellular responses. In addition to proteins, both prokaryotic and eukaryotic transferases can covalently link ADP-ribosylation to different conformations of nucleic acids, thus highlighting the evolutionary conservation of archaic stress response mechanisms. Here, we report several structural and functional aspects of DNA ADP-ribosylation modification controlled by the prototype DarT and DarG pair, which show ADP-ribosyltransferase and hydrolase activity, respectively. DarT/DarG is a toxin-antitoxin system conserved in many bacterial pathogens, for example in Mycobacterium tuberculosis, which regulates two clinically important processes for human health, namely, growth control and the anti-phage response. The chemical modulation of the DarT/DarG system by selective inhibitors may thus represent an exciting strategy to tackle resistance to current antimicrobial therapies.

Naegleria genus pangenome reveals new structural and functional insights into the versatility of these free-living amoebae.

Free-living amoebae of the Naegleria genus belong to the major protist clade Heterolobosea and are ubiquitously distributed in soil and freshwater habitats. Of the 47 Naegleria species described, N. fowleri is the only one being pathogenic to humans, causing a rare but fulminant primary amoebic meningoencephalitis. Some Naegleria genome sequences are publicly available, but the genetic basis for Naegleria diversity and ability to thrive in diverse environments (including human brain) remains unclear. Herein, we constructed a high-quality Naegleria genus pangenome to obtain a comprehensive catalog of genes encoded by these amoebae. For this, we first sequenced, assembled, and annotated six new Naegleria genomes. Genome architecture analyses revealed that Naegleria may use genome plasticity features such as ploidy/aneuploidy to modulate their behavior in different environments. When comparing 14 near-to-complete genome sequences, our results estimated the theoretical Naegleria pangenome as a closed genome, with 13,943 genes, including 3,563 core and 10,380 accessory genes. The functional annotations revealed that a large fraction of Naegleria genes show significant sequence similarity with those already described in other kingdoms, namely Animalia and Plantae. Comparative analyses highlighted a remarkable genomic heterogeneity, even for closely related strains and demonstrate that Naegleria harbors extensive genome variability, reflected in different metabolic repertoires. If Naegleria core genome was enriched in conserved genes essential for metabolic, regulatory and survival processes, the accessory genome revealed the presence of genes involved in stress response, macromolecule modifications, cell signaling and immune response. Commonly reported N. fowleri virulence-associated genes were present in both core and accessory genomes, suggesting that N. fowleri's ability to infect human brain could be related to its unique species-specific genes (mostly of unknown function) and/or to differential gene expression. The construction of Naegleria first pangenome allowed us to move away from a single reference genome (that does not necessarily represent each species as a whole) and to identify essential and dispensable genes in Naegleria evolution, diversity and biology, paving the way for further genomic and post-genomic studies.

The Detection Methods of Hydroxyl Radical: A Review

Hydroxyl radical (·OH) can rapidly react with biological macromolecules, organic and inorganic substances on account of its strong oxidizing property, so it is widely used in sewage treatment, chemiluminescence analysis, biological macromolecule modification and other fields. The strengthening effect of Hydrodynamic cavitation on chemical reactions depends on the number of free radicals initiated by cavitation. These free radicals are highly reactive and react rapidly with pollutants and other species in wastewater. Therefore, the systematic summary of detection methods of hydroxyl radical and the description of its advantages and disadvantages can provide technical support for scientific researchers, and guides the research in the future.

Golgi Stress Response: New Insights into the Pathogenesis and Therapeutic Targets of Human Diseases.

The Golgi apparatus modifies and transports secretory and membrane proteins. In some instances, the production of secretory and membrane proteins exceeds the capacity of the Golgi apparatus, including vesicle trafficking and the post-translational modification of macromolecules. These proteins are not modified or delivered appropriately due to insufficiency in the Golgi function. These conditions disturb Golgi homeostasis and induce a cellular condition known as Golgi stress, causing cells to activate the 'Golgi stress response,' which is a homeostatic process to increase the capacity of the Golgi based on cellular requirements. Since the Golgi functions are diverse, several response pathways involving TFE3, HSP47, CREB3, proteoglycan, mucin, MAPK/ETS, and PERK regulate the capacity of each Golgi function separately. Understanding the Golgi stress response is crucial for revealing the mechanisms underlying Golgi dynamics and its effect on human health because many signaling molecules are related to diseases, ranging from viral infections to fatal neurodegenerative diseases. Therefore, it is valuable to summarize and investigate the mechanisms underlying Golgi stress response in disease pathogenesis, as they may contribute to developing novel therapeutic strategies. In this review, we investigate the perturbations and stress signaling of the Golgi, as well as the therapeutic potentials of new strategies for treating Golgi stress-associated diseases.

Accessing the Thiol Toolbox: Synthesis and Structure-Activity Studies on Fluoro-Thiol Conjugated Antimicrobial Peptides.

The para-fluoro-thiol reaction (PFTR) is a modern name for the much older concept of a nucleophilic aromatic substitution reaction in which the para-position fluorine of a perfluorinated benzene moiety is substituted by a thiol. As a rapid and mild reaction, the PFTR is a useful technique for the post-synthetic modification of macromolecules like peptides on the solid phase. This reaction is of great potential since it allows for peptide chemists to access the vast catalogue of commercially available thiols with diverse structures to conjugate to peptides, which may impart favorable biological activity, particularly in antimicrobial sequences. This work covers the generation of a library of antimicrobial peptides by modifying a relatively inactive tetrapeptide with thiols of various structures using the PFTR to grant antimicrobial potency to the core sequence. In general, nucleophilic substitution of the peptide scaffold by hydrophobic thiols like cyclohexanethiol and octanethiol imparted the greatest antimicrobial activity over that of hydrophilic thiols bearing carboxylic acid or sugar moieties, which were ineffectual at improving the antimicrobial activity. The general trend here follows expected structure-activity relationship outcomes like that of changing the acyl group of lipopeptide antibiotics and is encouraging for the use of this reaction for structural modifications of antimicrobial sequences further.

Analysis of the level of oxidative stress by assessing the damage to the plasma protein serum albumin under the influence of an oxidizing agent

Oxidative stress, which leads to oxidative modification of various macromolecules, including proteins, is now considered an important pathogenetic link in many diseases. In this work, oxidative damage to a blood plasma protein, bovine serum albumin BSA, under the action of an oxidizing agent, hydrogen peroxide H2O2, was studied by spectrofluorometric method. The H2O2 concentration-dependent quenching of the intrinsic fluorescence of BSA is shown. BSA fluorescence quenching constants in hydrogen peroxide solutions are calculated by mathematical modeling methods. The dependences found in the fluorescence quenching constants are explained both by oxidative damage to the microenvironment of BSA tryptophan residues and by changes in the native conformation of protein globules upon oxidative damage. More significant peroxide damage to BSA occurs at lower pH values due to the fact that H2O2, as an oxidizing agent, acts more strongly in an acidic environment. The registered quenching of the protein's own fluorescence when damaged by an oxidizing agent can be used as a medical method for assessing the level of oxidative stress in the body in the diagnosis of a number of diseases.