Rosin Surfactant QRMAE Can Be Utilized as an Amorphous Aggregate Inducer: A Case Study of Mammalian Serum Albumin

Label-free visualization of unfolding and crosslinking mediated protein aggregation in nonenzymatically glycated proteins

Nonenzymatic glycation (NEG) unfolds and crosslinks proteins, resulting in aggregation. Label-free evaluation of such structural changes, without disturbing molecular integrity, would be beneficial for understanding the fundamental mechanisms of protein aggregation. The current study demonstrates the assessment of NEG-induced protein aggregation by combining autofluorescence (AF) spectroscopy and imaging. The methylglyoxal (MG) induced protein unfolding and the formation of cross-linking advanced glycation end-products (AGEs) leading to aggregation were evaluated using deep-UV-induced-autofluorescence (dUV-AF) spectroscopy in proteins with distinct structural characteristics. Since the AGEs formed on proteins are fluorescent, the study demonstrated the possibility of autofluorescence imaging of NEG-induced protein aggregates. Autofluorescence spectroscopy can potentially reveal molecular alterations such as protein unfolding and cross-linking. In contrast, AGE-based autofluorescence imaging offers a means to visually explore the structural arrangement of aggregates, regardless of whether they are amyloid or non-amyloid in nature.

Invitro anti-biofilm activity and the artificial chaperone activity of quinoline-based ionic liquids

The maintenance of protein conformation under stressful conditions is one of the prevailing challenges. This has led to a rapid growth in the ingenious protein therapies, in the past few decades, prioritizing the investigation of the structure and function of proteins in novel environments. Ionic Liquids (ILs) are currently dominating the biomedical industry, by endowing great solubility and stability to bio-molecules, especially proteins. Recently, researchers have devoted their attention towards the artificial chaperone activity of several classes of ILs. Thus, comprehending the long-term as well as momentary stability of protein conformation in IL formulations is an absolute necessity. In this context, we present the activity of quinoline-based ionic liquids (ILs) as artificial cheperones against time-dependent, self induced fibril formation in Bovine Serum Albumin (BSA). Herein, a series of quinoline-based ILs were synthesized and characterized. The structural and morphological changes induced in BSA in the presence and absence of these ILs are corroborated using several spectroscopic measurements and in-silico studies. The anti-microbial and antibiofilm activity of these compounds demonstrating their medicinal properties is substantiated in this study. Furthermore, the present research also gives an account of the toxicity of these compounds under in vivo conditions, using C. elegans as the model organism.

Aggregation and cytotoxicity of food additive dye (Azorubine)-albumin adducts: a multi-spectroscopic, microscopic and computational analysis

Protein and peptide misfolding is a central factor in the formation of pathological aggregates and fibrils linked to disorders like Alzheimer's and Parkinson's diseases. Therefore, it's essential to understand how food additives, particularly Azorubine, affect protein structures and their ability to induce aggregation. In this study, human serum albumin (HSA) was used as a model protein to investigate the binding and conformational changes caused by azorubine, a common food and drink colorant. The research revealed that azorubine destabilized the conformation of HSA at both physiological (pH 7.4) and acidic (pH 3.5) conditions. The loss of tryptophan fluorescence in HSA suggested significant structural alterations, particularly around aromatic residues. Far UV-CD analysis demonstrated disruptions in HSA's secondary structure, with a notable reduction in α-helical structures at pH 7.4. At pH 3.5, Azorubine induced even more extensive perturbations, resulting in a random coil conformation at higher azorubine concentrations. The study also investigated aggregation phenomena through turbidity measurements, RLS analysis, and TEM imaging. At pH 3.5, larger insoluble aggregates formed, while at pH 7.4, only conformational changes occurred without aggregate formation. Cytotoxicity assessments on neuroblastoma (SH-SY5Y) cells highlighted the concentration-dependent toxicity of albumin aggregates. Molecular dynamics simulations reaffirmed the stable interaction between azorubine and HSA. This research provides valuable insights into the mechanisms by which azorubine influences protein conformations. To further advance our understanding and contribute to the broader knowledge in this area, several future directions can be considered such as exploring other proteins, studying dose-response relationship, gaining mechanistic insights, biological relevance, toxicity assessment, identifying alternative food colorants, and mitigation strategies to prevent adverse effects of azorubine on serum proteins.Communicated by Ramaswamy H. Sarma.

Biochemical and Biophysical Characterisation of the Hepatitis E Virus Guanine-7-Methyltransferase

Hepatitis E virus (HEV) is an understudied pathogen that causes infection through fecal contaminated drinking water and is prominently found in South Asian countries. The virus affects ~20 million people annually, leading to ~60,000 infections per year. The positive-stranded RNA genome of the HEV genotype 1 has four conserved open reading frames (ORFs), of which ORF1 encodes a polyprotein of 180 kDa in size, which is processed into four non-structural enzymes: methyltransferase (MTase), papain-like cysteine protease, RNA-dependent RNA polymerase, and RNA helicase. MTase is known to methylate guanosine triphosphate at the 5'-end of viral RNA, thereby preventing its degradation by host nucleases. In the present study, we cloned, expressed, and purified MTase spanning 33-353 amino acids of HEV genotype 1. The activity of the purified enzyme and the conformational changes were established through biochemical and biophysical studies. The binding affinity of MTase with magnesium ions (Mg2+) was studied by isothermal calorimetry (ITC), microscale thermophoresis (MST), far-UV CD analysis and, fluorescence quenching. In summary, a short stretch of nucleotides has been cloned, coding for the HEV MTase of 37 kDa, which binds Mg2+ and modulate its activity. The chelation of magnesium reversed the changes, confirming its role in enzyme activity.

Phytochemical thymoquinone prevents hemoglobin glycoxidation and protofibrils formation: A biophysical aspect

d-ribose, a reducing sugar, in diabetic hyperglycemia provokes non-enzymatic glycoxidation of hemoglobin (Hb), an abundant protein of red blood cells (RBCs). Different types of intermediates adduct formation occur during glycoxidation, such as advanced glycation end-products (AGEs) which lead to amyloid formation due to structural and conformational alterations in protein. Therefore, the study of these intermediate adducts plays a pivotal role to discern their relationship with diabetes mellitus and related disorders. Here, we investigated the interaction mechanism of d-ribose with Hb, and Hb prebound phytochemical thymoquinone (TQ). Our investigation reveals that the interaction of TQ with histidine residues of Hb interferes with the interaction of d-ribose with glycine residues at the glycation-site. Based on that, we had performed a time-based (21-days) in-vitro glycoxidation study at 37 °C to investigate the structural perturbation mechanism of Hb at different time-intervals in absence/presence of TQ. We found that prolonged glycoxidation induces amyloid formation in absence of TQ but in its presence, the process was prohibited. In summary, this study examined and characterized biophysically different intermediate-states of protein carrying glycoxidation-modification. Our findings suggested that TQ potentially affects interaction of d-ribose with Hb that prevents glycoxidation and protofibril formation, which establishes TQ as a potential therapeutic agent.

Comparative refolding of guanidinium hydrochloride denatured bovine serum albumin assisted by cationic and anionic surfactants via artificial chaperone protocol: Biophysical insight

In the present study, we report the cooperative refolding/renaturation behaviour of guanidinium hydrochloride (GdnHCl) denatured bovine serum albumin (BSA) in the presence of cationic surfactant cetyltrimethylammonium bromide (CTAB), anionic surfactant sodium dodecyl sulphate (SDS) and their catanionic mixture in the solution of 60 mM sodium phosphate buffer of physiological pH 7.4, using artificial chaperone-assisted two-step method. Here, we have employed biophysical techniques to characterize the refolding mechanism of denatured BSA after 200 times of dilution in the presence of cationic, anionic surfactants and their catanionic mixture, separately. We have found that minimum refolding of diluted BSA in the presence of 1:1 rational mixture of CTAB and SDS (CTAB/SDS = 50/50), it may be due to the micelles formation which is responsible for the unordered microstructure aggregate formation. Other mixtures (CTAB/SDS = 20/80 and 80/20) slightly played an effective role during refolding process in the presence of methyl-β-cyclodextrin. On other hand, CTAB and SDS are more effective and reflect a good renaturation tendency of denatured BSA solution separately and in existence of methyl-β-cyclodextrin as compare to their mixture compositions. But overall, CTAB has the better renaturation tendency as compare to SDS in the existence of methyl-β-cyclodextrin. These results ascribed the presence of charge head group and length of hydrophobic tail of CTAB surfactant that plays an important task during electrostatic and hydrophobic interactions at pH 7.4 at which BSA carries negative charge on their surface. These biophysical parameters suggest that, CTAB surfactant assisted artificial chaperone protocol may be utilized in the protein renaturation/refolding studies, which may address the associated problems of biotechnological industries for the development of efficient and inexpensive folding aides, which may also be used to produced genetically engineered cells related diseases, resulting from protein misfolding/aggregation.

Advances in Rosin-Based Chemicals: The Latest Recipes, Applications and Future Trends

A comprehensive review of the publications about rosin-based chemicals has been compiled. Rosin, or colophony, is a natural, abundant, cheap and non-toxic raw material which can be easily modified to obtain numerous useful products, which makes it an excellent subject of innovative research, attracting growing interest in recent years. The last extensive review in this research area was published in 2008, so the current article contains the most promising, repeatable achievements in synthesis of rosin-derived chemicals, published in scientific literature from 2008 to 2018. The first part of the review includes low/medium molecule weight compounds: Especially intermediates, resins, monomers, curing agents, surfactants, medications and biocides. The second part is about macromolecules: mainly elastomers, polymers for biomedical applications, coatings, adhesives, surfactants, sorbents, organosilicons and polysaccharides. In conclusion, a critical evaluation of the publications in terms of data completeness has been carried out with an indication of the most promising directions of rosin-based chemicals development.

Aggregation and conformational stability evaluation of myoglobin in the presence of ionic surfactant

Sodium lauroyl sarcosinate (SLS) is frequently used for the solubilization of inclusion bodies in vitro due to its structural similarity to lipid plasma membrane. There are many factors that could influence protein aggregation propensity, including overall protein surface charge and hydrophobicity. Here, the aggregation pathway of myoglobin protein was studied under different conditions (pH 3.5 and 7.4) in the presence of varying concentrations of SLS to evaluate the underlying forces dictating protein aggregation. Data obtained from Rayleigh light scattering, ThT binding assay, and far-UV CD indicated that SLS have different effects on the protein depending on its concentration and environmental conditions. In the presence of low concentrations of SLS (0.05-0.1 mM), no aggregation was detected at both pH conditions tested. Whereas, as we reach higher SLS concentrations (0.5-10.0 mM), myoglobin started forming larger-sized aggregates at pH 3.5 and not pH 7.4. These results suggest that electrostatics interactions as well as hydrophobic forces play an important role in SLS-induced myoglobin aggregation.

Biophysical insight into the interaction mechanism of plant derived polyphenolic compound tannic acid with homologous mammalian serum albumins

Numerous phenolic compounds have been reported in the last decade that have a good antioxidant property and interaction affinity towards mammalian serum albumins. In the present study, we have utilized mammalian serum albumins as a model protein to examine their comparative interaction property with polyphenolic compound tannic acid (TA) by using various spectroscopic and calorimetric methods We have also monitored the esterase and antioxidant activity of mammalian serum albumins in the absence and presence of TA. The obtain results recommended that the TA have a good binding affinity (∼10⁴ to 10⁶M^-1) towards mammalian serum albumins and shows double sequential binding sites, which depends on the concentration of TA that induced the conformational alteration which responsible for the thermal stability of proteins. Binding affinity, structural transition and thermodynamic parameters were calculated from spectroscopic and calorimetric method reveals that non-covalent interaction causes partial conformational alteration in the secondary structure of protein ie.; increase in α-helical content with decrease in β-sheet, random coil and other structure. Meanwhile, we have found that esterase activities of serum albumins were also stabilized against hydrolysis and shows higher antioxidant activity in the presence of TA because albumins its self have an immense antioxidant activity beside TA.

Polyols (Glycerol and Ethylene glycol) mediated amorphous aggregate inhibition and secondary structure restoration of metalloproteinase-conalbumin (ovotransferrin)

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Conalbumin aggregates at 65 °C and denaturation occur at above this temperature.

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The nature of aggregates was identified as amorphous.

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The polyols inhibits the aggregation of conalbumin via protecting the secondary structure.

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Glycerol is found to be more protective than ethylene glycol.

Under physical or chemical stress, proteins tend to form aggregates either highly ordered (amyloid) or unordered (amorphous) causing many pathological disorders in human and loss of proteins functionality in both laboratory conditions and industries during production and storage at commercial level. We investigated the effect of increasing temperature on Conalbumin (CA) and induced aggregation at 65 °C. The enhanced Thioflavin T (ThT) and ANS (1-anilinonaphtalene 8-sulfonic acid) fluorescence intensity, show no shift on Congo red binding, additionally, transmission and scanning electron microscopy (TEM) (SEM) reveal amorphous morphology of the aggregate. Our investigation clearly demonstrated that polyols namely Glycerol (GL) and Ethylene glycol (EG) are so staunch to inhibit amorphous aggregates via restoring secondary conformation. Addition of polyols (15% GL and 35% EG) significantly decrease the turbidity, Rayleigh scattering ThT and ANS fluorescence intensity. The dynamic light scattering (DLS) data show that hydrodynamic radii (R_h) of the aggregates is ∼20 times higher than native CA while nearly similar for GL and EG protected CA due to condensation of core size with little difference.