Sensitive spectrophotometric determination of human serum albumin(HSA) with (2-(5-bromo-2-pyridylazo)-5-(N-phenyl-N-sulfopropylamino)phenol) (5-Br.PAPS)-cobalt(II)) complex

Rapid and sensitive determination of proteins with Eriochrome Red in the presence of anionic surfactant by multi-spectroscopic methods

A new high-sensitivity detection of protein assay at the nanogram level is proposed based on multi-spectroscopic methods including resonance light scattering (RLS), atomic force microscopy (AFM), ultraviolet spectra (UV) and fluorescence spectra etc. Under the optimum conditions, the amplified RLS signals of anionic azo dyes Eriochrome Red B (ERB) in the presence of anionic surfactant sodium dodecyl sulphonate (SDS) was in proportion to the concentration of proteins in the range of 0.0-3.5 mg L(-1) and 3.5-12.5 mg L(-1) for bovine serum albumin (BSA), 0.0-2.0 mg L(-1) and 2.0-8.0 mg L(-1) for human serum albumin (HSA). The detection limits were 4.2 ng mL(-1) and 2.7 ng mL(-1), respectively. The method was satisfactorily applied to the measurement of total protein in human serum samples and a high-sensitivity was achieved.

Sensitization of surfactants on the chemiluminescence reaction of fluorescein isothiocyanate labeled proteins

The effect of surfactants on fluorescein isothiocyanate (FITC)-bovine serum albumin (BSA)-hypochlorite (ClO(-)), FITC-human serum albumin (HSA)-ClO(-), FITC-ovoconalbumin (OVA)-ClO(-), FITC-hemoglobin (Hb)-ClO(-) systems were investigated with chemiluminescence method by the reversed phase flow injection. It was found that the chemiluminescence (CL) intensity of each system was increased greatly in the presence of cationic surfactants. Cethyltrimethylammonium bromide (CTAB) is the optimal surfactant of these systems. The optimal conditions of the CL reaction and the optimal concentration of CTAB were examined and the function of cationic surfactant CTAB on the CL reaction was also discussed.

Scopoletine as fluorescence probe for determination of protein

Scopoletine (SLT), 7-hydroxy-6-methoxylcoumarin, is known to possess biological activities such as abirritating and anti-tumor, it can quench intrinsic fluorescence of bovine serum albumin (BSA) and the fluorescence intensity of itself is enhanced. So, SLT is used as fluorescence probe for quantitative determination of protein. The experiments indicate that under optimum conditions, the enhanced intensity of fluorescence is in proportion to the concentration of proteins in a wide range, and their detection limits (S/N=3) are 1.4 x 10(-8)g mL(-1) for BSA and 1.1 x 10(-8)g mL(-1) for HSA, respectively. Samples were satisfactorily determined. The interaction mechanism is also discussed.

A flow-injection chemiluminescence method for the determination of human serum albumin, using the reaction of fluorescein–human serum albumin–sodium hypochlorite by the enhancement effect of the cationic surfactant cetyltrimethylammonium bromide

The interaction between surfactant and fluorescein was studied, using a fluorescence spectroscopy and flow-injection (FI) chemiluminescence (CL) method. It was found that the cationic surfactant cetyltrimethylammonium bromide (CTAB) could cause the structural transformation of fluorescein from the quinone to the spirolactone form, and greatly enhance the CL intensity of the fluorescein-human serum albumin (HSA) complex. Based on this finding, a rapid and sensitive FI-CL method was developed for the determination of HSA. Under the optimum conditions, the proposed method has a linear range of 0.05-24.0 microg/mL, with a detection limit of 0.03 microg/mL for HSA (3sigma). The relative standard deviation (RSD) of 1.2 microg/mL HSA (n = 8) is 0.8%. The method was applied to the determination of protein content in urine samples, with satisfactory results. Density functional theory was used to study the mechanism of surfactant-enhanced CL intensity of the fluorescein-HSA complex.

Chelates of cobalt(III) and iron(II) with 2-(5-bromo-2-pyridylazo)-5-diethylaminophenol as test probes for the characterization of chromatographic effects on a reversed-phase liquid chromatography stationary phase

The chromatographic effects on a reversed-phase liquid chromatography (RPLC) phase were established with the use of chelates system: cobalt(III) and iron(II) with 2-(5-bromo-2-pyridylazo)-5-diethylaminophenol as the test probes. Both chelates have the same octahedral structure, M:L = 1:2, the former chelate is cationic and can be used to probe the ion-exchange phenomena on a RPLC phase, whereas the latter is not charged and can be used as reference molecule with respect to the charged one. Based on well-established LC phenomena referred in the literature, the suitability of the chelate system for examining some chromatographic effects was tested. It was concluded that the proposed test method is sensitive towards the ion-exchange phenomena on the LC phase and the hydrogen bonding between the solvent eluent and the LC phase. In addition, chromatographic effects due to the presence of ultrasonic field or due to the presence of aromatic amines in the eluent were observed with the help of the proposed test method. Based on molecular computation, the properties of chelates were compared with properties of quaternary amines, the probes most frequently used for testing LC phases, and the possible differences in an interaction of the mentioned compounds with a surface of a RPLC phase were indicated.

Fluorimetric study of the interaction between human serum albumin and quinolones-terbium complex and its application

A highly sensitive spectrofluorimetric method is proposed for determination of human serum albumin (HSA) and some quinolone drugs. Using quinolones-terbium (Tb3+) complex as a fluorescent probe, in the buffer solution of pH 7.8, HSA can remarkably enhance the fluorescence intensity of the quinolones-Tb3+ complex at 545 nm and the enhanced fluorescence intensity of Tb3+ ion is in proportion to the concentration of HSA and quinolone drugs. Optimum conditions for the determination of HSA were also investigated. The linear ranges and limits of detection are 8.0 x 10(-9) to 8.0 x 10(-8) mol L(-1), 4.20 x 10(-9) mol L(-1) (for HSA); 1.0 x 10(-6) to 4.0 x 10(-6) mol L(-1), 1.87 x 10(-8) mol L(-1) (for norfloxacin) and 1.0 x 10(-7) to 1.0 x 10(-6) mol L(-1), 4.82 x 10(-8) mol L(-1) (for enoxacine), respectively. This method is simple, practical and relatively free interference from coexisting substances, as well as much more sensitive than most of the existing assays.

Study of the interaction of proteins with curcumin and SDS and its analytical application

It is found that protein and sodium dodecyl sulphonate (SDS) can enhance resonance light scattering (RLS) of curcumin (CU). Based on this phenomenon, a new quantitative method for protein in aqueous solution has been developed. In the BR (pH 3.5) buffer, the RLS intensity of CU-SDS system is greatly enhanced by protein. The enhanced RLS is proportional to the concentration of protein in the range of 0.00020-20.0 microgml(-1) for bovine serum albumin (BSA) and 0.00040-1.0 microgml(-1) for human serum albumin (HSA) and their detection limits are 0.16 and 0.041 ngml(-1), respectively. An actual sample is satisfactorily determined. In addition, the interaction mechanism between protein and CU-SDS is also studied by using multi-techniques such as RLS, absorption spectroscopy and fluorescence, zeta potential assay measurement.

Determination of trace proteins with pyronine Y and SDS by resonance light scattering

A new resonance light scattering (RLS) probe for determining proteins is presented. The weak RLS of pyronine Y-SDS can be enhanced substantially by adding proteins in the presence of H2SO4, resulting in a strong and wide RLS band in the region 310-425 nm. The interaction of pyronine Y-SDS with proteins was studied on the basis of this behavior and a new quantitative method was developed for determining proteins. The enhanced RLS intensity is proportional to the concentration of proteins in the range 0.15-3.6 microg mL(-1) for bovine serum albumin (BSA) and 0.06-4.8 microg mL(-1) for human serum albumin (HSA), with detection limits of 21.0 and 12.0 ng mL(-1), respectively. This method is characterized by high sensitivity, rapidity of reaction, and simplicity. Four synthetic samples were determined satisfactorily and recovery was 99.5-101.5%. Results for human serum and urine samples were in agreement with those obtained by the Bradford method, with relative standard deviations (RSD) of 1.5-3.1%.

Resonance light scattering technique for the determination of protein with rutin and cetylpyridine bromide system

A new resonance light scattering (RLS) assay of protein is presented. In Tris-NaOH (pH = 10.93) buffer, the RLS of rutin-cetylpyridine bromide (CPB) system can be greatly enhanced by protein, including bovine serum albumin (BSA) and human serum albumin (HSA). The enhanced RLS intensities are in proportion to the concentration of proteins in the range of 5 x 10(-9) to 2.5 x 10(-6) g ml(-1) for BSA and 2.5 x 10(-8) to 3.5 x 10(-6) g ml(-1) for HSA. The detection limits (S/N = 3) are 3.0 ng ml(-1) for BSA and 10.0 ng ml(-1) for HSA. Samples are determined satisfactorily.

Evaluation of two lanthanide complexes for qualitative and quantitative analysis of target proteins via partial least squares analysis

Two lanthanide complexes, namely 5-aminosalicylic acid ethylenediaminetetraacetate europium(III) (5As-EDTA-Eu3+) and 4-aminosalicylic acid ethylenediaminetetraacetate terbium(III), were evaluated for the analysis of carbonic anhydrase, human serum albumin (HSA), and gamma-globulin. Quantitative analysis is based on their luminescence enhancement upon protein binding and qualitative analysis on their lifetime capability to recognize the binding protein. Analytical figures of merit are presented for the three proteins. The limits of detection with 5As-EDTA-Eu3+ are at the parts per billion level. Partial least square regression analysis is used to determine HSA and gamma-globulin in binary mixtures without previous separation at the concentration ranges typically found in clinical tests of human blood serum.

Protein analysis with tetra-substituted sulfonated cobalt phthalocyanine by the technique of Rayleigh light scattering

This is the first report of cobalt-tetrasulfonatophthalocyanine (CoTSPc) as a probe of Rayleigh light scattering (RLS) to determine proteins at nanogram levels. A highly sensitive method has been developed for the determination of proteins by the light scattering technique on a common spectrofluorimeter, based on the fact that the weak RLS of CoTSPc can be greatly enhanced in the presence of proteins. Under optimum conditions, the linear ranges of the calibration curves were 0.10-34.3 microg x mL(-1) for both human serum albumin and bovine serum albumin, with detection limits of 15.5 and 13.9 ng x mL(-1), respectively. Moreover, there is almost no interference of any amino acids and metal ions. The method has been applied to the direct determination of total proteins in human serum samples, and the results were satisfactory with clinical data provided.

Frequency doubling scattering and second-order scattering spectra of phosphato-molybdate heteropoly acid-protein system and their analytical application

In the sulfuric acid medium, the reaction of heteropoly compounds with proteins could result in the enhancement of frequency doubling scattering (FDS) and second-order scattering (SOS). Based on the characteristic, a novel method for the determination of trace amounts of protein by using the FDS and SOS method has been developed. Their maximum scattering wavelengths, lambda(ex)/lambda(em), appear at 940/470 nm for FDS and 350/700 nm for SOS, respectively. In a certain range, the concentration of proteins is directly proportional to the enhanced intensity of FDS and SOS. The suitable reaction conditions, affecting factors as well as the influence of some coexisiting substances were investigated. The methods exhibited high sensitivity, and the detection limits were in the range of 8.6-39.3 ng ml(-1) depending on different methods. The method had good selectivity, and was applied to the determination of protein in synthetic samples and practical samples with satisfactory results.

Study on the interaction between protein and Eu(III)-chlorotetracycline complex and the determination of protein using the ?uorimetric method

Chlorotetracycline (CTC) can react with europium ions Eu3+, and the complex emits the intrinsic fluorescence of Eu3+. The intensity is greatly enhanced by proteins and this forms the basis of a new fluorimetric method for determination of protein. Further research indicates that under optimum conditions, the enhanced intensity of fluorescence is in proportion to the concentration of proteins, in the range 2.0 x 10(-7)-1.0 x 10(-5) g/mL for bovine serum albumin (BSA) (linear equation, I(f) = 34.35933 + 11.54467 x 10(6)C)(r = 0.99895) and 8.0 x 10(-7)-1.0 x 10(-5) g/mL for human serum albumin (HSA) (linear equation, I(f) = 76.58881 + 5.3569 x 10(6)C) (r = 0.99283). Detection limits (S/N = 3) were 8.9 x 10(-9) g/mL for BSA and 3.3 x 10(-8) g/mL for HSA. In an assay for BSA in calf serum, this method gave a value close to that determined by the UV spectrophotometric method.

Determination of proteins using the p-acetylchlorophosphonazo-barium(II) complex as a spectroprobe

A novel spectrophotometric method has been developed for the determination of proteins using the p-acetychlorophosphonazo (CPA-pA)-barium(II) complex as a spectroprobe. In the pH range of 2.0-2.8, the absorbance of the CPA-pA-barium(II) complex at 649 nm is greatly decreased by protein. The absorbance decrease is in proportion to the concentration of protein in the range of 0-20 mg/L. The apparent molar absorptivities are 1.56 x 10(6), 1.70 x 10(6) and 6.04 x 10(5) L mol(-1) cm(-1) for bovine serum albumin (BSA), human serum albumin (HAS) and ovalbumin (OVA), respectively. The method is reproducible and simple, and has been used to determine total protein in human sera. The results are in agreement with those obtained by the pyrocatechol violet (PV)-Mo(VI) method, with relative standard deviations of 2.5-3.5% (n=6).

Direct quantification of human serum albumin in human blood serum without separation of gamma-globulin by the total internal reflected resonance light scattering of thorium-sodium dodecylbenzene sulfonate at water/tetrachloromethane interface

A direct quantification of human serum albumin (HSA) in blood serum samples without separation is proposed based on the measurements of total internal reflected resonance light scattering (TIR-RLS) at water/tetrachloromethane (H(2)O/CCl(4)) interfaces. In the pH range of 6.37-6.59, the coadsorption of the binary complex of HSA-Th(IV) with sodium dodecylbenzene sulfonate occurs at the H(2)O/CCl(4) interface, forming an amphiphilic layer and displaying greatly enhanced TIR-RLS signals with the maximum peak located at 340-370 nm. The enhanced TIR-RLS intensity is in proportion to the HSA concentration in the range 0.15-1.0 micro gml(-1). The limit of detection is 14.4 ngml(-1). The contents of HSA in blood serum samples were determined with the recovery of 97.1-102.3% and RSD of 0.6-2.9%, which are identical to those obtained according to the spectrofluorimetric method using chrome azurol S.

[Photometric analysis with reaction between metal ion (M) and organic reagent (R)]

Firstly, the syntheses of various organic reagents (R) containing such xanthene derivatives as O-hydroxyhydro-quinonephthalein (QnPh), and 3,4,5,6-tetrahydroxyfluoran (gallein, Gall) were studied. Secondarily, the coexisting effects of surfactant (cationic-, anionic-, amphoteric- and nonionic-surfactants alone or combination) on the coloring or fluorescence reactions between various (R) such as xanthene derivatives, aromatic amines and various metal ions (M) such as bismuth(III), tin(IV), iron(III), molybdenum(VI), uranium(VI), cobalt(II), aluminum(III), etc. were systematically investigated. Thirdly, numerous simple and sensitive photometric analyses (spectrophotometry and fluorophotometry) for various (M) and organic compounds(Org) such as biological samples, and pharmaceutical preparations by formation reactions of (R-M) binary or ((R-M)-Org) ternary complexes were established in the coexistence of surfactant alone or combination.

A highly sensitive assay for protein using resonance light-scattering technique with dibromohydroxyphenylfluorone-molybdenum(VI) complex

At pH 2.8 and in the presence of 0.090% p-octylpolyethyleneglycol phenylether, the resonance light-scattering (RLS) spectrum of molybdenum(VI) complex with dibromohydroxyphenylfluorone (DBHPF) has a sharp peak at 586 nm. If the micro protein coexists with Mo(VI) and DBHPF, the RLS intensity of the complex at 586 nm is significantly enhanced by protein due to the binding interaction between protein and DBHPF-Mo(VI) complex. Based on this a new assay for protein is described. The dynamic ranges for bovine and human serum albumins are both 0.05-0.75 mg l-1 with detection limits of 13 and 15 ng ml-1, respectively. Besides high sensitivity, the method is characterized by good reproducibility, rapidity of reaction, good stability of chemical system, commonality of spectrofluorometer, few coexisting substances, especially detergents. The determinations of diluted human serum and urine by this method give the results very close to these by the Coomassie brilliant blue G-250 colorimetry, with relative standard deviations of five duplicates of 1.8-2.5%.