Differentiating the protein dynamics using fluorescence evolution of tryptophan residue(s): A comparative study of bovine and human serum albumins upon temperature jump

Effects of mono-substituents on the polarity-sensitive fluorescent probe properties of pyrene

This study investigates the effects of mono-substituents (i.e., hydroxyl, methyl, amino and nitro groups) on the polarity-sensitive fluorescent probe properties of pyrene (Pyr) using fluorescence, UV-vis, and circular dichroism absorption spectroscopy. The results indicate that the four mono-substituents altered the fluorescence spectral characteristics of Pyr to varying degrees, with the most to least influential order being: nitro, amino, hydroxyl, and methyl. 1-Aminopyrene (1-APyr) and 1-nitropyrene (1-NPyr) are deemed unsuitable for use as polarity-sensitive fluorescent probes due to their limited or absent spectral characteristics. The I386/I406 and I376/I396 ratios of 1-HPyr and 1-MPyr decrease as solvents polarity increases, contrasting with the I372/I384 ratio of Pyr. Thus, 1-hydroxypyrene (1-HPyr) and 1-methylpyrene (1-MPyr) also exhibit polarity-sensitive characteristics similar to Pyr, and their solubility in PBS buffer surpasses that of Pyr at 298 K. Moreover, 1-HPyr and 1-MPyr are practicable for detecting the polarity of human serum albumin (HSA) under simulated physiological conditions. The results underscore the potential of the polarity-sensitive mono-substituents of Pyr in biological applications, particularly in probing protein polarity and conformational changes, and further providing a potential tool for the related research in biochemistry and pathology.

A red-emissive tripodal nanoprobe for the discrimination of serum albumin with conformational change from Y- to ω-like and probing mitochondrial viscosity

Serum albumins, such as bovine serum albumin (BSA) and human serum albumin (HSA), play a crucial role in various biological processes. Discrimination between BSA and HSA is challenging due to their similar structures and reactivity. Here, we report mitochondria-targeted red fluorescent tripodal nanoprobe DMAS-TP, forming spherical nano-aggregates (∼90 nm) in water for discrimination of BSA over HSA and detection and imaging of viscosity in HeLa cells. DMAS-TP exhibits an ∼56-fold fluorescence intensity increase in 95% glycerol compared to water, which indicates restricted movement in high-viscosity solvents. Furthermore, the addition of 5 equiv. BSA and HSA to DMAS-TP solution displays ∼50-fold and ∼10-fold fluorescence intensity increases at 630 nm (λex 490 nm), respectively, and can detect as low as 20 nM BSA and 140 nM HSA. The fluorescence anisotropy plot shows that the DMAS-TP anisotropy values decrease from 0.234 to 0.185 with increasing [BSA/HSA], suggesting a conformational change from Y- to ω-like structure. The fluorescence lifetime of DMAS-TP increases gradually with BSA/HSA, suggesting dynamic complexation. DMAS-TP aggregates diminish to 6 nm particles when encapsulated in BSA confirmed by DLS, SEM, and TEM, with reduced fluorescence intensity in the presence of bilirubin, indicating that DMAS-TP binds within the BSA cavity near site IB. DMAS-TP is highly permeable to HeLa cells and shows a strong affinity for mitochondria, making it suitable for imaging viscosity and BSA via strong fluorescence in the red channel.

Unraveling binding interactions between methasterone and bovine serum albumin (BSA): A spectroscopic and computational study

In this study, binding interactions between methasterone and bovine serum albumin (BSA) were analyzed using spectroscopic techniques and molecular docking. UV absorption spectroscopy showed the formation of a ground-state complex between methasterone and bovine serum albumin (BSA). Thermodynamic parameters from fluorometric analysis indicated that the hydrogen bonding and van der Waal forces were the main interacting forces between the complex and the reaction was found to be spontaneous. Molecular docking further validated it. Nano differential scanning fluorimetry showed the protein was found to be more thermally stable in the presence of methasterone. Circular dichroism spectroscopy revealed slight reduction in the helicity after binding with methasterone suggesting conformational changes to promote binding. As no prior information exists on the binding interactions between methasterone and BSA, this study provides insights into methasterone-BSA interactions, which can serve as a foundation for future investigations into its pharmacological properties.

A Fluorescence-Based Temperature-Jump Apparatus for Illustrating Protein Dynamics on the Millisecond Time Scale

A fluorescence-based temperature jump (T-jump) module was constructed to illustrate the large-domain motion of a given protein upon thermal stimulus on the millisecond time scale. The aqueous sample was readily heated by 5.0 °C in ca. 2 ms with a lasting high temperature plateau (>1 s) upon irradiation with the "optical Riemann sum" of the discrete infrared pulses of different energy sequences from a 1467 nm diode laser operated at 1k Hz. The temperature evolution was revealed by the time-evolved fluorescence intensity change of the dissolved tryptophan. Bovine serum albumin (BSA) and human serum albumin (HSA) were chosen as model proteins, and their fluorescence intensity evolutions were recorded at 36.6-39.9 °C upon T-jump from 35.0 °C, within the range of physiological temperatures. The observed protein dynamics of BSA was characterized with an apparent activation energy of 276 ± 23 kJ mol-1, whereas HSA did not manifest the dynamic component. In this measurement, only a tiny amount of sample, ca. 1 μL, was required due to the conjugation of the microspot objective, and the initial temperature was readily controlled by a homemade thermostatic pad. This millisecond-resolution technique is advantageous for illustrating the large-domain dynamics of the targeted protein, bridging the characterizations of the localized protein dynamics on nanosecond to microsecond time scales using the fast techniques and the steady-state protein conformational features by conventional methods, such as Fourier-transform infrared and circular dichroism spectroscopies.

Biocompatibility of Phosphorus Dendrimers and Their Antibacterial Properties as Potential Agents for Supporting Wound Healing

Dendrimers are a wide range of nanoparticles with desirable properties that can be used in many areas of medicine. However, little is known about their potential use in wound healing. This study examined the properties of phosphorus dendrimers that were built on a cyclotriphosphazene core and pyrrolidinium (DPP) or piperidinium (DPH) terminated groups, to be used as potential factors that support wound healing (in vitro). Therefore, the degree of toxicity of the tested compounds for human erythrocytes and the human fibroblast cell line (BJ) was determined, and it was found that at low concentrations, the tested compounds are compatible with blood. The influence of phosphorus dendrimers on plasma proteins (human serum albumin (HSA) and fibrinogen) was examined, with a lack of conformational changes in the structure of these proteins, suggesting that their physiological function was not disturbed. The effects on plasma coagulation cascade and fibrinolysis were also assessed, and it was found that phosphorus dendrimers in low concentrations are blood compatible and interfere neither with coagulation processes nor in clot breakdown. Skin injuries, especially chronic wounds, are also susceptible to infection; therefore, the antimicrobial potential of dendrimers was tested, and it was found that these dendrimers had antibacterial activity against both Gram-negative and Gram-positive bacteria. The highest activity of the tested compounds was found for higher applied concentrations.

Insights into the Binding of Metadoxine with Bovine Serum Albumin: A Multi-Spectroscopic Investigation Combined with Molecular Docking

BACKGROUND

Metadoxine, also known as pyruvate dehydrogenase activator, is a small molecule drug that has been used in the treatment of various medical conditions. Bovine serum albumin is a commonly studied protein that serves as a plasmatic for understanding protein-drug interactions due to its abundance.

OBJECTIVE

This research suggests that metadoxine can bind to bovine serum albumin with moderate affinity, leading to an alteration in the secondary structure of the protein, which may also influence the protein's stability and function, which could provide a comprehensive understanding of the interaction at a molecular level. In this study, a variety of methodologies wereused to determine various thermodynamic parameters.

METHODS

The study uses UV-visible, Fluorescence, Fourier-transform infrared, Circular dichroism spectroscopy, and Molecular docking to analyze the interaction between bovine serum albumin and metadoxine, providing thermodynamic parameters for understanding the protein structure and its binding.

RESULT

The binding of metadoxine with bovine serum albumin, causes a hyperchromic shift. In fluorescence spectroscopy, the value of the Stern Volmer increases constantly with an increase in temperature, suggesting a stronger interaction between the Metadoxine and the Bovine serum albumin, leading to dynamic quenching. Additionally, Fourier-transform infrared and circular dichroism indicated a reduction in the secondary structure of Bovine serum albumin.

CONCLUSION

The interactions between metadoxine and bovine serum albumin, cause hyperchromic shift revealed by UV-visible spectroscopy, whereas in Fluorescence spectroscopy, the value of the Stern Volmer constant increases with an increase in temperature, suggesting a stronger interaction between the MD and the BSA, leading to dynamic quenching. Additionally, Fourier-transform infrared and circular dichroism spectroscopy indicated a reduction in the secondary structure of the protein, as evidenced by the shifting of the amide II band and leading to a slight decrease in the α- helix content. The molecular docking shows that metadoxine was docked in the subdomain IIA binding pocket of BSA.

Transient spectroscopic insights into nitroindole's T1 state: Elucidating its intermediates and unique photochemical properties

Indoles are notable for their distinct photophysical and photochemical properties, making them useful indicators in biological systems and promising candidates for a variety of pharmaceutical applications. While some indoles exhibit room temperature phosphorescence, such a phenomenon has not been observed in nitroindoles. Typically, adding of a nitro group into aromatic compounds promotes ultrafast intersystem crossing and increases the formation quantum yield of the lowest excited triplet (T1). Therefore, understanding the reactivity of nitroindoles' T1 states is imperative. This study investigated the physical properties and chemical reactivities of the T1 state of 6-nitroindole (3HN-6NO2) in both polar aprotic and protic solvents, using transient absorption spectroscopy. Our results demonstrate the basicity and acidity of 3HN-6NO2, emphasizing its potential for protonation and dissociation in mildly acidic and basic conditions, respectively. Furthermore, 3HN-6NO2 has a high oxidizing capacity, participating in electron transfer reactions and proton-coupled electron transfer to produce radicals. Interestingly, in protic solvents like alcohols, 3HN-6NO2 dissociates at the -NH group and forms N-H…O hydrogen-bonded complexes with the nitro group. By identifying transient absorption spectra of intermediates and quantifying kinetic reaction rate constants, we illuminate the unique properties of the T1 state nitroindoles, enriching our understanding of their photophysical and photochemical behaviors. The results of this study have significant implications for their potential application in both biological systems and materials science.

Insight into the binding mechanisms of fluorinated 2-aminothiazole sulfonamide and human serum albumin: Spectroscopic and in silico approaches

4-Fluoro-N-(thiazol-2-yl)benzenesulfonamide (3) is a novel fluorinated compound, containing various biological activities. Therefore, absorption spectroscopy, fluorescence quenching, molecular docking, and molecular simulation were employed to investigate the interaction between 3 and human serum albumin (HSA). Firstly, compound 3 meets all criteria for drug-likeness prediction. UV absorption spectra revealed the interaction of 3 with HSA altered the microenvironment of protein, as well as circular dichroism spectroscopic analysis indicated slightly conformational changes and a reduction in α-helical content. The binding parameters of the HSA-3 complex suggested that fluorescence quenching is driven by combined static and dynamic processes. Additionally, the stability of the complex is attributed to conventional hydrogen and hydrophobic bonding interactions. Furthermore, esterase-like activity indicated that the binding of 3 might disrupt HSA's bond networks, leading to structural alterations. Consequently, the strong binding constant (Ka ≈ 1.204 × 106 M-1) aligns with the predicted unbound fraction (0.28) in serum, indicating that thiazole 3 has good bioavailability in plasma and can be effectively transported to target sites, thereby exerting its pharmaceutical effects. However, careful dosage management is essential to prevent potential adverse effects. Overall, these findings highlight the potential of 3 as a therapeutic agent, emphasizing the need for further research to optimize its uses.

Isolation, Characterization, and Single-Crystal X-ray Analysis of Lantabetulic Acid from Rhus alata: Insights into HSA and BSA Binding Interactions, with In-Silico Study

This study investigated the bioactive potential of Rhus alata, a plant known for its rich phytochemicals. A previously unreported compound was isolated from R. alata and characterized using various spectroscopic techniques (IR, UV, NMR, MS) and confirmed for the first time by X-ray crystallography. In isolated compound 1, noncovalent interactions between H···H/H···H, C···C/C···C and O···H/H···O play a major role in its packing arrangement. This observation is consistent with the results of Hirshfeld surface analysis, which quantified these interactions as 14.2%, 84.6%, and 1.2%, respectively. The isolated compound was identified as lantabetulic acid (1) (3β,25-expoxy-3α-hydroxylup-20(29)-en-28-oic acid). To understand its potential biological interactions, the binding affinity of lantabetulic acid to biomolecules such as bovine serum albumin (BSA), and human serum albumin (HSA), was assessed. The results showed significant binding efficacy, indicating potential interactions with these molecules. Furthermore, the DPPH assay demonstrated the potent antioxidant activity of this compound. We used in silico molecular docking to clarify the binding affinity between lantabetulic acid and a particular receptor. Furthermore, molecular dynamic simulation studies also explored the binding interaction. As well, MM/GBSA calculations corroborate the simulation results and the stability of the complex. Docking and dynamics studies revealed promising binding scores, suggesting further investigation into their potential therapeutic applications. Geometric parameters and the absorption spectrum of compound 1 were also determined using the DFT approach and compared with experimental findings.

The Role of Ovalbumin in Manganese Homeostasis during Chick Embryogenesis: An EPR Spectroscopic Study

Ovalbumin (OVA), a protein vital for chick embryo nutrition, hydration, and antimicrobial protection, together with other egg-white proteins, migrates to the amniotic fluid and is orally absorbed by the embryo during embryogenesis. Recently, it has been shown that for optimal eggshell quality, the hen diet can be supplemented with manganese. Although essential for embryonic development, manganese in excess causes neurotoxicity. This study investigates whether OVA may be involved in the regulation of manganese levels. The binding of Mn(II) to OVA was investigated using electron paramagnetic resonance (EPR) spectroscopy. The results show that OVA binds a maximum of two Mn(II) ions, one with slightly weaker affinity, even in a 10-fold excess, suggesting it may have a protective role from Mn(II) overload. It seems that the binding of Mn(II), or the presence of excess Mn(II), does not affect OVA's tertiary structure, as evidenced from fluorescence and UV/vis measurements. Comparative analysis with bovine and human serum albumins revealed that they exhibit higher affinities for Mn(II) than OVA, most likely due to their essentially different physiological roles. These findings suggest that OVA does not play a role in the transport and storage of manganese; however, it may be involved in embryo protection from manganese-induced toxicity.

Insight into the Effect of Submicellar Concentrations of Sodium Deoxycholate on the Structure, Stability, and Activity of Bovine and Human Serum Albumin: An Interesting Comparison between Single and Double Tryptophan Proteins

The progressive escalation in the applications of bile salts in diverse fields has triggered research on their interaction with various biological macromolecules, especially with proteins. A proper understanding of the interaction process of bile salts, particularly in the lower concentrations range, with the serum albumin seems important since the normal serum concentration of bile salts is approximately in the micromolar range. The current study deals with a comprehensive and comparative analysis of the interaction of submicellar concentrations of sodium deoxycholate (NaDC) with two homologous transport proteins: bovine serum albumin (BSA) and human serum albumin (HSA). HSA and BSA with one and two tryptophans, respectively, provide the opportunity for an interesting comparison of tryptophan fluorescence behavior on interaction with NaDC. The study suggests a sequential interaction of NaDC in three discrete stages with the two proteins. A detailed study using warfarin and ibuprofen as site markers provides information about the sites of interaction, which is further confirmed by inclusive molecular dynamics simulation analysis. Moreover, the comparison of the thermodynamics and stability of the NaDC-serum albumin complexes confirms the stronger interaction of NaDC with BSA as compared to that with HSA. The differential interaction between the bile salt and the two serum albumins is further established from the difference in the extent of decrease in the esterase-like activity assay of the proteins in the presence of NaDC. Therefore, the present study provides important insight into the effect of submicellar concentrations of NaDC on the structure, stability, and activity of the two homologous serum albumins and thus can contribute not only to the general understanding of the complex nature of serum albumin-bile salt interactions but also to the design of more effective pharmaceutical formulations in the field of drug delivery and biomedical research.

Heterocyclic (pyrazine)carboxamide Ru(ii) complexes: structural, experimental and theoretical studies of interactions with biomolecules and cytotoxicity

Treatments of N-(1H-benzo[d]imidazol-2-yl)pyrazine-2-carboxamide (HL1) and N-(benzo[d]thiazol-2-yl)pyrazine-2-carboxamide carboxamide ligands (HL2) with [Ru(p-cymene)Cl2]2 and [Ru(PPh3)3Cl2] precursors afforded the respective Ru(ii) complexes [Ru(L1)(p-cymene)Cl] (Ru1), [Ru(L2)(p-cymene)Cl] (Ru2), [Ru(L1)(PPh3)2Cl] (Ru3), and [Ru(L2)(PPh3)2Cl] (Ru4). These complexes were characterized by NMR, FT-IR spectroscopies, mass spectrometry, elemental analyses, and crystal X-ray crystallography for Ru2. The molecular structure of complex Ru2 contains one mono-anionic bidentate bound ligand and display pseudo-octahedral piano stool geometry around the Ru(ii) atom. The interactions with calf thymus DNA (CT-DNA) and bovine serum albumin (BSA) were investigated by spectroscopic techniques. The experimental binding studies suggest that complexes Ru1-Ru4 interact with DNA, primarily through minor groove binding, as supported by molecular docking results. Additionally, these complexes exhibit strong quenching of the fluorescence of tryptophan residues in BSA, displaying static quenching. The in vitro cytotoxicity studies of compounds Ru1-Ru4 were assessed in cancer cell lines (A549, PC-3, HT-29, Caco-2, and HeLa), as well as a non-cancer line (KMST-6). Compounds Ru1 and Ru2 exhibited superior cytotoxicity compared to Ru3 and Ru4. The in vitro cytotoxicity and selectivity of compounds Ru1 and Ru2 against A549, PC-3, and Caco-2 cell lines surpassed that of cisplatin.

Revealing the mechanistic interactions of profenofos and captan pesticides with serum protein via biophysical and computational investigations

Profenofos (PF) and captan (CT) are among the most utilized organophosphorus insecticides and phthalimide fungicides, respectively. To elucidate the physicochemical and influential toxicokinetic factors, the mechanistic interactions of serum albumin and either PF or CT were carried out in the current study using a series of spectroscopy and computational analyses. Both PF and CT could bind to bovine serum albumin (BSA), a representative serum protein, with moderate binding constants in a range of 103-104 M-1. The bindings of PF and CT did not induce noticeable BSA's structural changes. Both pesticides bound preferentially to the site I pocket of BSA, where the hydrophobic interaction was the main binding mode of PF, and the electrostatic interaction drove the binding of CT. As a result, PF and CT may not only induce direct toxicity by themselves, but also compete with therapeutic drugs and essential substances to sit in the Sudlow site I of serum albumin, which may interfere with the pharmacokinetics and equilibrium of drugs and other substances causing consequent adverse effects.

Electrospinning of bovine serum albumin-based nano-fibers: From synthesis to medical prospects; Challenges and future directions

Bovine serum albumin (BSA) is a globular non-glycoprotein that has gotten a lot of attention because of its unique properties like biocompatibility, biodegradability, non-immunogenicity, non-toxicity, and strong resemblance to the natural extracellular matrix (ECM). Given its robust mechanical properties, such as interfacial tension, conductivity, swelling resistance, and viscoelasticity, it can be concluded that it is an appropriate matrix for producing novel BSA-based nanoconstructs. Thus, simple analytic methods are required for accurately detecting BSA as a model protein in medical sciences and healthcare. Furthermore, the characteristics mentioned above aid BSA in the electrospinning process, which results in fibers conjugated with other polymers. Electrospun synthesis has recently received much attention for its ability to produce stable, biomimicking, highly porous, 3D BSA-derived nano-fibers. As a result, BSA-based nano-fibers have achieved exclusive developments in the medical sector, such as tissue engineering for the remodeling of damaged tissue or organ repair by creating artificial ones. Meanwhile, they could be used as drug delivery systems (DDS) for target-specific drug delivery, wound dressings, and so on. This study illustrates the structural and physicochemical properties of BSA and the determination of BSA using various methods, by citing recent reports and current developments in the medical field. Furthermore, current challenges and future directions are also highlighted.

Noncovalent Association Thermodynamics of Turn-On Fluorescent Probes with Human Serum Albumin: Dual-Concentration Ratio Method

Efficient quantification of the affinity of a drug and the targeted protein is critical for strategic drug design. Among the various molecules, turn-on fluorescent probes are the most promising signal transducers to reveal the binding strength and site-specificity of designed drugs. However, the conventional method of measuring the binding ability of turn-on fluorescent probes by using the fractional occupancy under the law of mass action is time-consuming and a massive sample is required. Here, we report a new method, called dual-concentration ratio method, for quantifying the binding affinity of fluorescent probes and human serum albumin (HSA). Temperature-dependent fluorescence intensity ratios of a one-to-one complex (L ⋅ HSA) for a turn-on fluorescent probe (L), e. g., ThT (thioflavin T) or DG (dansylglycine), with HSA at two different values of [L]0 /[HSA]0 under the constraint [HSA]0 >[L]0 were collected. The van't Hoff analysis on these association constants further resulted in the thermodynamic properties. Since only two samples at different [L]0 /[HSA]0 are required without the need of [L]0 /[HSA]0 at a wide range, the dual-concentration ratio method is an easy way to greatly reduce the amounts of fluorescent probes and proteins, as well as the acquisition time.

Insights into the interaction between the kusaginin and bovine serum albumin: Multi-spectroscopic techniques and computational approaches

Kusaginin, as a phenylethanoid glycoside, which has exhibited wide antioxidant and antimicrobial properties. The molecular mechanism underlying the broad biological activities of kusaginin has not yet been well documented. In this paper, the interaction of kusaginin with bovine serum albumin (BSA) has been explored by fluorescence spectra, UV-vis absorption spectra, and circular dichroism (CD) spectra along with computational approaches. The fluorescence experiments showed that kusaginin could strongly quench the intrinsic fluorescence of BSA through both dynamic and static quenching mechanisms. The thermodynamic analysis suggested that hydrophobic force was the main force in stabilizing the BSA-kusaginin complex. In addition, conformation changes of BSA were observed from three-dimensional and synchronous fluorescence spectra, UV spectra, and CD spectra under experimental conditions. All these experimental results have been complemented and validated by the molecular docking and dynamic simulation studies, which revealed that kusaginin was bound on the hydrophobic cavity in subdomain IIA of BSA and formed a stable BSA-kusaginin complex. Finally, density functional theory (DFT) calculation further implied that hydrogen bonds also support stabilizing the BSA-kusaginin complex. This research may aid in understanding the pharmacological characteristics of kusaginin and provide a vital reference modeling for the design of analogues drugs.

Investigation of the binding behavior of bioactive 7-methoxyflavone to human serum albumin by coupling multi-spectroscopic with computational approaches

The natural flavonoids with bioactivity as secondary plant metabolites are mostly found in fruits, vegetables, tea and herbs, the distribution and bioavailability of which in vivo depends on the interaction and successive binding with carrier proteins in the systemic circulation. In this paper, the binding behavior of bioactive 7-methoxyflavone (7-MF) with human serum albumin (HSA) was studied with the aid of the combination of multi-spectroscopic methods, molecular docking and molecular dynamic simulation. The results of multi-spectroscopic experiments revealed that 7-MF interacted with HSA predominantly via fluorescence static quenching and the microenvironment around the fluorophore Trp residues in HSA became more hydrophilicity with the binding of 7-MF. Thermodynamic analysis demonstrated that hydrogen bonds and van der Waals forces played a dominant role in stabilizing the HSA-7-MF complex. Moreover, the docking experiment and molecular dynamic simulation further confirmed that 7-MF could enter the active cavity of HSA and caused more stable conformation and change of secondary structure of HSA through forming hydrogen bond. The exploration of the mechanism of 7-MF binding to HSA lights a new avenue to understand the stability, transport and distribution of 7-MF and 7-MF may hold great potential to be extended as a promising alternative of dietary supplements or pharmaceutical agents.

White light-emitting, biocompatible, water-soluble metallic magnesium nanoclusters for bioimaging applications

Ultra-small (1.6 nm), water-soluble, white light-emitting (WLE), highly stable (∼8 months) BSA templated metallic (Mg⁰) nanoclusters (fluorescent magnesium nanoclusters = FMNCs) is developed using the green and facile route. Synthesis was facilitated by the reduction of magnesium salt, where template bovine serum albumin is utilized as a reducing agent and ascorbic acid act as a capping agent to impart stability in water, thereby obtaining stabilized Mg⁰nanoclusters In solution, stabilized Mg⁰nanoclusters produce white light (450-620 nm with FWHM ∼120 nm) upon 366 nm light excitation. This white light emission was found to have a CIE coordinate of 0.30, 0.33 [pure white light CIE (0.33, 0.33)]. Taking advantage of WLE and ultrasmall size, FMNCs were used forin vitrofluorescence imaging of HaCaT cell lines, yielding blue (τ= 2.94 ns, with a relative of QY = 1.2 % w.r.t QS), green (τ= 3.07 ns; relative quantum yield of 4.6% w.r.t R6G) and red (τ= 0.3 ns) images. Further, incubation of FMNCs with HEK293 (Human embryonic kidney cell) and cancerous MDA-MB-231 (Breast cancer cell line) human cell lines yielded 100 % cell viability. Current work is envisioned to contribute significantly in the area of science, engineering, and nanomedicine.

Effect of Oxidative Modification by Peroxyl Radical on the Characterization and Identification of Oxidative Aggregates and In Vitro Digestion Products of Walnut (Juglans regia L.) Protein Isolates

Walnut protein is a key plant protein resource due to its high nutritional value, but walnuts are prone to oxidation during storage and processing. This article explored the oxidative modification and digestion mechanism of walnut protein isolates by peroxyl radical and obtained new findings. SDS-PAGE and spectral analysis were used to identify structural changes in the protein after oxidative modification, and LC-MS/MS was used to identify the digestion products. The findings demonstrated that as the AAPH concentration increased, protein carbonyl content increased from 2.36 to 5.12 nmol/mg, while free sulfhydryl content, free amino content, and surface hydrophobicity decreased from 4.30 nmol/mg, 1.47 μmol/mg, and 167.92 to 1.72 nmol/mg, 1.13 μmol/mg, and 40.93 nmol/mg, respectively. Furthermore, the result of Tricine-SDS-PAGE in vitro digestion revealed that protein oxidation could cause gastric digestion resistance and a tendency for intestinal digestion promotion. Carbonyl content increased dramatically during the early stages of gastric digestion and again after 90 min of intestine digestion, and LC-MS/MS identified the last digestive products of the stomach and intestine as essential seed storage proteins. Oxidation causes walnut proteins to form aggregates, which are then re-oxidized during digestion, and proper oxidative modification may benefit intestinal digestion.

Preparation and characterization of high embedding efficiency epigallocatechin-3-gallate glycosylated nanocomposites

Glycosylated protein nano encapsulation was an efficient encapsulation technology, but its embedding rate for EGCG was not high, and the research on the embedding mechanism was relatively weak. Based on this, this study compared the embedding effect of glycosylated peanut globulin and glycosylated casein on EGCG. The embedding mechanism of EGCG with glycosylated protein was discussed by ultraviolet, fluorescence, infrared and fluorescence microscopy. Results revealed that the highest encapsulation efficiency of EGCG was 93.89 ± 1.11%. The neutral pH value and 0.3 mg/mL EGCG addition amount were suitable for EGCG glycosylated nanocomposites. The hydrogen bond between EGCG hydroxyl group and tyrosine and tryptophan of glycosylated protein is mainly non covalent. The encapsulation effect of EGCG glycosylated nanocomposites could be quenched by changing the polar environment and spatial structure of the group. The fluorescence characteristic and dispersibility of EGCG glycosylated peanut globin were higher than EGCG glycosylated casein. This study might provide a theoretical basis for EGCG microencapsulation technology and EGCG application in tea beverage and liquid tea food systems.

Protein dynamics of human serum albumin at hypothermic temperatures investigated by temperature jump

Human serum albumin (HSA) is the most abundant protein in human plasma. Most protein dynamics studies of HSA have been performed above the hyperthermia temperature (>42 °C), so information on the dynamics under hypothermic conditions (<35 °C) is lacking. In this work, a tryptophan-based fluorescence temperature jump system was employed to investigate the thermally-induced dynamic process of HSA at a physiological concentration of ca. 45 mg mL^-1 and pH = ca. 7 upon an instantaneous temperature increase from 25 °C to 30-43 °C. The observed kinetics manifested a three-state consecutive feature, . Upon analysis with the Arrhenius model, the rate coefficients k₁ and k₂ manifested piecewise temperature dependence, and the turning-point temperature was found to be ca. 34 °C, coinciding with the upper bound of hypothermic temperature. Meanwhile, the corresponding activation energies of the transitions at 34-43 °C were lower than those at 30-34 °C, suggesting that protein conformational adjustments at 34-43 °C were more feasible than those at hypothermic temperatures. These observations provided a fresh viewpoint on the relationship between the energetics of protein dynamics and the apparent functioning of a given protein at the molecular level.