Investigation on the interaction of tetrachloride fluorescein–bovine serum albumin-β-cyclodextrin and the determination of protein by flow injection analysis

Assessing the molecular interaction between a COVID-19 drug, nirmatrelvir, and human serum albumin: calorimetric, spectroscopic, and microscopic investigations

The research examined the molecular interaction between nirmatrelvir (NIR), a drug used to treat COVID-19, and human serum albumin (HSA) using various techniques, viz., isothermal titration calorimetry (ITC), absorption, fluorescence, CD spectroscopy, and atomic force microscopy (AFM). ITC analysis showed that the NIR-HSA system possessed a moderate binding affinity, with a K a value of 6.53 ± 0.23 × 104 M-1 at a temperature of 300 K. The thermodynamic values demonstrated that the NIR-HSA complex was stabilized by hydrophobic contacts, hydrogen bonds, and van der Waals forces. The research also discovered modifications in the UV-Vis absorption spectrum of the protein as well as swelling of the HSA molecule when exposed to NIR, based on AFM results. The three-dimensional fluorescence spectral data indicated changes in the microenvironment around HSA's Trp and Tyr residues. Alterations in the protein structure (both secondary and tertiary structures) of HSA after NIR binding were verified using CD spectral studies in the far-UV and near-UV regions. The identification of the NIR binding site in subdomain IB (Site III) of HSA was predicted through competitive displacement experiments.

Research progress of fluorescent composites based on cyclodextrins: Preparation strategies, fluorescence properties and applications in sensing and bioimaging

Fluorescence analysis has been regarded as one of the commonly used analytical methods because of its advantages of simple operation, fast response, low cost and high sensitivity. So far, various fluorescent probes, with noble metal nanoclusters, quantum dots, organic dyes and metal organic frameworks as representatives, have been widely reported. However, single fluorescent probe often suffers from some deficiencies, such as low quantum yield, poor chemical stability, low water solubility and toxicity. To overcome these disadvantages, the introduction of cyclodextrins into fluorescent probes has become a fascinating approach. This review (with 218 references) systematically covers the research progress of fluorescent composites based on cyclodextrins in recent years. Preparation strategies, fluorescence properties, response mechanisms and applications in sensing (ions, organic pollutants, bio-related molecules, temperature, pH) and bioimaging of fluorescent composites based on cyclodextrins are summarized in detail. Finally, the current challenges and future perspectives of these composites in relative research fields are discussed.

β-Cyclodextrin/chitosan–magnetic graphene oxide–surface molecularly imprinted polymer nanocomplex coupled with chemiluminescence biosensing of bovine serum albumin

In this report, a sensitive and selective chemiluminescence biosensor for bovine serum albumin coupled with surface molecularly imprinted nanocomplex using β-cyclodextrin/chitosan–magnetic graphene oxide as backbone material was investigated.

Resonance light scattering determination of metallothioneins using levofloxacin-palladium complex as a light scattering probe

A novel method of resonance light scattering (RLS) was developed for the analysis of trace metallothioneins (MTs) in human urine. In a CH(3)COOH-CH(3)COONa buffer solution of pH 4.5, the formation of a complex between levofloxacin (LEV)-Pd and MTs led to enhance the RLS intensity of the system, and the enhanced RLS intensity at 468 nm was proportional to the concentration of MTs in the range of 0.059-22.4 μg mL(-1). The linear regression equation was ΔI=127.5 ρ (μg mL(-1))-88.02 with a correlation coefficient of 0.9992, and the detection limit of 17.8 ng mL(-1). The relative standard deviation and the average recovery were 3.8-5.4% (n=11) and 92.15%, respectively. The proposed method is convenient, reliable and sensitive, and has been used successfully for the determination of trace MTs in human urine samples.

β-cyclodextrin cross-linked polymer as solid-phase extraction material coupled with the spectrophotometric method for the analysis of serum albumin

The β-cyclodextrin cross-linked polymer (β-CDCP) was synthesized and used as solid-phase extraction material to preconcentrate/analysis bovine serum albumin (BSA) coupled with UV-vis spectroscopy. The method based on the complex (BSA-phenylfluorone (PF)) adsorbed on β-CDCP. Adsorption kinetics and various factors of the formation procedure of BSA-PF and its retention on β-CDCP were investigated. The linear range and detection limit (DL) was 20.0-200.0 and 0.03 mg/L, respectively. Moreover, the β-CDCP could be used repeatedly. The proposed method has been applied to analysis serum albumin with satisfactory results.

Determination of L-tyrosine by beta-cyclodextrin sensitized fluorescence quenching method

A novel beta-cyclodextrin (beta-CD) sensitized fluorescence quenching method for the determination of l-tyrosine (l-Tyr) with Mo(VI)-phenyl-fluorone (PF) as a fluorescence probe has been developed. The fluorescence intensity of Mo(VI)-PF-beta-CD was diminished as the l-tyrosine was added, the fluorescence quenching value DeltaF=F(beta-CD-Mo-PF)-F(beta-CD-Mo-PF-l-Tyr) was enhanced in beta-CD and there was a linear relationship between the DeltaF and the concentration of l-Tyr. Under the optimal conditions, the linear range of calibration curve for the determination of l-tyrosine was 0.3-20.0microgmL(-1); the detection limit was 0.094microgmL(-1). NaOH (10%, w/v) is the best reagent of hydrolysis in sample preparation. The sensitized mechanism of beta-cyclodextrin was discussed. The method has been applied to the determination of l-tyrosine in spirulina and food samples with satisfactory results.

Influences of urea and guanidine hydrochloride on the interaction of 6-thioguanine with bovine serum albumin

The interaction of 6-thioguanine (6-TG) and bovine serum albumin (BSA) in the absence and presence of denaturant (urea and Guanidine hydrochloride) was investigated by fluorescence spectroscopic techniques. Changes of fluorescence intensity both in F(304) and in F(348) of BSA reflected increasing participation of tyrosine fluorescence in the total emission with increasing denaturant, which indicated that energy transfer from tyrosyl residues to tryptophanyl residues became less efficient in the denatured tertiary protein structure. The quenching effects of 6-TG were shown not only on the native but also on the unfolded form of BSA. The quenching constants and binding constants were calculated from the fluorescence spectra of the BSA/6-TG complex both in the absence and presence of the denaturant. The data suggested that the quenching constants and binding constants of 6-TG for BSA decreased with increasing concentration of denaturant. The spectroscopic analysis also showed antidenaturant properties of 6-TG under both denaturant conditions.

Study on the interaction between methyl violet and bovine serum albumin by spectral analyses

In this article the interaction between methyl violet (MV) and bovine serum albumin (BSA) was studied with spectroscopy. The results indicated that the fluorescence intensity of BSA was quenched strongly by MV through a static quenching procedure. The association constants, the number of binding sites and basic thermodynamic parameters were obtained based on fluorescence quenching data. The effect of MV on the conformation of BSA had been investigated with synchronous fluorescence spectroscopy and circular dichroism (CD) spectrum.

Solid substrate-room temperature phosphorimetry for the determination of trace protein using ion association complex [Cu(BPY)2]2+ . [(Fin)2]2- as a phosphorescent probe

Fluorescein (HFin) emitted strong and stable room temperature phosphorescence (RTP) on filter paper after set at 50 degrees C for 10 min using Li(+) as the ion perturber. HFin existed as Fin(-) when the pH value was in the range of 5.45-7.36. Fin(-) could react with [Cu(BPY)(2)](2+) (BPY: alpha,alpha-bipyridyl) to produce ion association complex [Cu(BPY)(2)](2+).[(Fin)(2)](2-), which could enhance the RTP signal of Hfin. In the presence of bovine serum albumin (BSA), the -COOH group of Fin(-) in the [Cu(BPY)(2)](2+).[(Fin)(2)](2-) could react with the -NH(2) group of BSA to form the ion association complex [Cu(BPY)(2)](2+).[(Fin-BSA)(2)](2-), which contained -CO-NH- bond. This complex could sharply enhance the RTP signal of Hfin and the Delta I(p) was directly proportional to the content of BSA. According to the facts above, a new solid substrate-room temperature phosphorimetry (SS-RTP) for the determination of trace protein had been established using the ion association complex [Cu(BPY)(2)](2+).[(Fin)(2)](2-)as a phosphorescent probe. This method had wide linear range (0.40 x 10(-9)-280 x 10(-9)mg l(-1)), high sensitivity (the detection limit (LD) was 1.4 x 10(-10)m gl(-1)), good precision (RSD: 3.4-4.9%) and high selectivity (the allowed concentration of coexistent ions or coexistent materials was high). It had been applied to the determination of the content of protein in 10 kinds of real samples, and the result agreed well with pyrocatechol violet-Mo (VI) method (P.V.M.M.), which indicated it had high accuracy. Meanwhile, reaction mechanism for the determination of trace protein with [Cu(BPY)(2)](2+).[(Fin)(2)](2-) phosphorescent probe was also discussed. The academic thought of this research could not only be used to develop many kinds of ion association complex phosphorescent probes, but also provided a new way to promote the sensitivity of SS-RTP.

Synchronous fluorescence determination of urinary 1-hydroxypyrene, beta-naphthol and 9-hydroxyphenanthrene based on the sensitizing effect of beta-cyclodextrin

A novel method for the simultaneous determination of 1-hydroxypyrene (1-OHP), beta-naphthol (beta-NAP) and 9-hydroxyphenanthrene (9-OHPe) in human urine has been established by using synchronous fluorescence spectrometry. It was based on the fact that synchronous fluorescence spectrometry can resolve the broad-band overlapping of conventional fluorescence spectra, which arise from their similar molecular structures. Only one single scan is needed for quantitative determination of three compounds simultaneously when Deltalambda=15nm is chosen. The signals detected at these three wavelengths, 369.6, 330.0 and 358.0nm, vary linearly when the concentration of 1-OHP, beta-NAP and 9-OHPe is in the range of 2.16x10(-8)-1.50x10(-5)molL(-1), 1.20x10(-7)-1.10x10(-5)molL(-1) and 1.07x10(-7)-3.50x10(-5)molL(-1), respectively. The correlation coefficients for the standard calibration graphs were 0.994, 0.999 and 0.997 (n=7) for 1-OHP, beta-NAP and 9-OHPe, respectively. The limits of detection (LOD) for 1-OHP, beta-NAP and 9-OHPe were 6.47x10(-9)molL(-1), 3.60x10(-8)molL(-1) and 3.02x10(-8)molL(-1)with relative standard deviations (R.S.D.) of 4.70-6.40%, 2.80-4.20%, 3.10-4.90% (n=6), respectively. The method described here had been applied to determine traces of 1-OHP, beta-NAP and 9-OHPe in human urine, and the obtained results were in good agreement with those obtained by the HPLC method. In addition, the interaction modes between beta-cyclodextrin (beta-CD) and 1-OHP, beta-NAP or 9-OHPe, as well as the mechanism of the fluorescence enhancement were also discussed.