Biomedical subjects

Changxia Sun

Publications and source records attributed to Changxia Sun.

15 recordsLinked to original sources

PubMed2006

The sensitive determination of nucleic acids using resonance light scattering quenching method.

It is found that in hexamethylene tetramine (HMTA)-HCl buffer of pH 7.00, nucleic acids can quench the resonance light scattering (RLS) of europium (III) (Eu3+)-2-thenoyltrifluoroacetne (TTA)-1,10-phenanthroline (Phen) system. Based on this, a sensitive method for the determination of nucleic acids is proposed. The experiments indicate that under the optimum conditions, the quenched RLS intensity is in proportion to the concentration of nucleic acids in the range of 1.0x10(-10) to 2.0x10(-6) g ml-1 for fish sperm (fsDNA), 1.0x10(-11) to 1.0x10(-6) g ml-1 for yeast RNA (yRNA), 5.0x10(-11) to 5.0x10(-7) g ml-1 for calf thymus DNA (ctDNA). Their detection limits (S/N=3) are 0.03, 0.006 and 0.002 ng ml-1, respectively. Therefore, the proposed method is the most sensitive RLS method for the determination of nucleic acids so far. The interaction between nucleic acids and Eu3+-TTA-Phen is also discussed.

Europium↗

PubMed2005

Molecular self-assembling and the fluorescence enhancement in morin-Al3+-cetyltrimethylammonium bromide-protein system.

Fluorescence enhancement effect of the morin-Al3+-cetyltrimethylammonium bromide (CTAB)-bovine serum albumin (BSA) system is reported here and the interaction mechanism is studied using fluorescence, resonance light scattering (RLS), absorption spectroscopy, Far-UV circular dichroism (CD) spectrum and small angle X-ray scattering (SAXS) measurement. It is considered that protein can bind with Al3+, morin and CTAB through self-assembling function with electrostatic attraction, hydrogen bond, hydrophobic interaction and Vander Waal force etc, and forms a supermolecular association with multilayer structure, in which morin-Al3+ is clamped between BSA and CTAB. In this system, the fluorescence enhancement of morin originates from both intermolecular energy transfer between BSA and morin, and the hydrophobic microenvironment provided by BSA and CTAB. Whereas Al3+ plays a key role for the enhancement of energy transfer efficiency because it provides an efficient channel for the energy transfer between BSA and morin.

Aluminum Compounds↗

PubMed2005

Unfolding and refolding of bovine serum albumin induced by cetylpyridinium bromide.

The interaction of bovine serum albumin (BSA) with cationic surfactant cetylpyridinium bromide (CPB) in aqueous solution (pH 7.00) was studied quantitatively with ultraviolet (UV)-visible, far-UV, and near-UV circular dichroism, fluorescence, small angle x-ray scattering, and nuclear magnetic resonance measurement. It was found that CPB at low and high concentrations could induce the unfolding and refolding of BSA, respectively. We suggest that in the unfolding process, there existed BSA-CPB complex with the "necklace and bead" structure in which the unfolded BSA wrapped around CPB micelles, and that the hydrophobic interaction between the complexes led to the formation of large aggregates. The aromatic headgroup of CPB interacted with the tryptophan residues of BSA, resulting in the aromatic ring stacking between BSA and CPB. During the refolding process, the BSA molecule was penetrated into the rod micelle of CPB and the hydrophobic moiety of the BSA molecule was exposed outside while its hydrophilic part was hidden inside, thereby disrupting the aromatic ring stacking.

Animals↗

PubMed2004

The fluorescence enhancement effect of the Tb-Gd-guanosine-5'-triphosphate-phen system and its analytical application.

It has been found that Tb(3+) can react with guanosine-5'-triphosphate (GTP) and o-phenanthroline (phen), resulting in the intrinsic fluorescence of Tb(3+). This fluorescence can be enhanced by adding La(3+), Gd(3+), Lu(3+), Sc(3+), Y(3+), and so on, among which Gd(3+) produces the greatest enhancement. These are new co-luminescence systems. The experiments indicate under optimum conditions, the fluorescence intensity of the Tb-Gd-GTP-phen system is proportional to the concentration of GTP over the range 1x10(-9) to 3x10(-5) mol/l. The detection limit is 3.1x10(-10) mol/l. The proposed method provides the most sensitive fluorimetry of GTP so far. The mechanism of the Tb-Gd-GTP-phen system has also been studied. The data indicates that there is a large congeries of Tb-Gd-GTP-phen, and the fluorescence enhancement of the Tb-Gd-GTP-phen system is considered to originate from intramolecular and intermocular energy transfers, and the energy-insulating sheath of the Gd complex.

Gadolinium↗

PubMed2004

Advances in the study of luminescence probes for proteins.

Spectral probes (or labels) have been widely used for the investigation and determination of proteins and have made considerable progress. Traditional luminescence probes include fluorescent derivatizing reagents, fluorescent probes and chemiluminescence probes which continue to develop. Of them, near infrared (NIR) fluorescent probes are especially suitable for the determination of biomolecules including proteins, so their development has been rapid. Novel luminescence probes (such as nanoparticle probes and molecular beacons) and resonance light scattering probes recently appeared in the literature. Preliminary results indicate that they possess great potential for ultrasensitive protein detection. This review summarizes recent developments of the above-mentioned probes for proteins and 195 references are cited.

Luminescent Measurements↗

PubMed2004

Study on the interaction between nucleic acids and cationic surfactants.

The interactions of nucleic acids and cationic surfactants (cetylpyridine bromide (CPB) and cetyltrimethylammonium bromide (CTMAB)) in aqueous solution have been studied using the techniques of resonance light scattering (RLS) spectroscopy, the absorption spectroscopy, zeta potential assay and NMR assignment measurement. It is considered that CPB or CTMAB can assemble on the surface of nucleic acid via electrostatic and hydrophobic forces, which results in the formation of large associate of nucleic acid-cationic surfactant and RLS enhancement of nucleic acid. Besides these forces, the pi-pi stacking force between CPB and nucleic acid also exists in the associate. In comparison with CTMAB, CPB has larger enhancement on RLS of nucleic acid, which is attributed to that the enhancement of the former is only due to the absorption of the bases of nucleic acid, while the enhancement of the latter is own to the synergetic resonance caused by the absorption of both bases of nucleic acid and the pyridyl in CPB. These results have important implication for understanding the influence of surfactants on nucleic acid functionality in life science.

Bromides↗

PubMed2004

Study on the fluorescent enhancement effect in terbium-gadolinium-protein-sodium dodecyl benzene sulfonate system and its application on sensitive detection of protein at nanogram level.

The co-luminescence effect in a terbium-gadolinium-protein-sodium dodecyl benzene sulfonate (SDBS) system is reported here. Based on it, the sensitive quantitative analysis of protein at nanogram levels is established. The co-luminescence mechanism is studied using fluorescence, resonance light scattering (RLS), absorption spectroscopy and NMR measurement. It is considered that protein could be unfolded by SDBS, then a efficacious intramolecular fluorescent energy transfer occurs from unfolded protein to rare earth ions through SDBS acting as a "transfer bridge" to enhance the emission fluorescence of Tb3+ in this ternary complex of Tb-SDBS-BSA, where energy transfer from protein to SDBS by aromatic ring stacking is the most important step. Cooperating with the intramolecular energy transfer above is the intermolecular energy transfer between the simultaneous existing complexes of both Tb3+ and Gd3+. The fluorescence quantum yield is increased by an energy-insulating sheath, which is considered to be another reason for the resulting enhancement of the fluorescence. Förster theory is used to calculate the distribution of enhancing factors and has led to a greater understanding of the mechanisms of energy transfer.

Absorption↗

PubMed2004

Sensitive determination of carbohydrates by fluorimetric method with Ce(IV) and sodium triphosphate.

A new simple and sensitive fluorimetric method for the determination of carbohydrates is described. The method is based on the reaction between carbohydrates and Ce(IV) in the presence of sulfuric acid. All the reductive carbohydrates can be detected indirectly by the fluorescence of Ce(III) produced. The addition of sodium triphate enhances the sensitivity of the method by more than 10-folds. Under optimum conditions, an excellent linear relationship was obtained between the fluorescence intensity and the concentration of carbohydrates. The limits of detection lie in the range of 9.3 x 10(-10) - 1.3 x 10(-9) mol/L. As compared to the normal fluorimetric method, the proposed method is faster and more sensitive.

Carbohydrates↗

PubMed2003

Resonance light-scattering method for the determination of BSA and HSA with sodium dodecyl benzene sulfonate or sodium lauryl sulfate.

A new resonance light-scattering (RLS) assay of proteins such as bovine serum albumin (BSA) and human serum albumin (HSA) is presented. In the medium of phosphoric acid (pH=2.6), the weak RLS of sodium dodecyl benzene sulfonate (SDBS) or sodium lauryl sulfate (SLS) can be greatly enhanced by proteins, owing to interaction between the protein and the anionic surfactant and formation of an associate. The RLS intensity of the SDBS-protein system is stronger than that of the SLS-protein system under same experimental conditions. It is considered that the synergistic resonance caused by the absorption of both protein and SDBS could produce strong RLS, while absorption of protein only in the SLS system could cause relatively weak RLS. The enhanced intensity of RLS is proportional to the concentration of the protein. If SDBS is used as the probe the linear range is 7.5 x 10(-9)-1.5 x 10(-5) g mL(-1) for BSA and 1.0 x 10(-8)-1.0 x 10(-5) g mL(-1) for HSA. The detection limits are 1.8 and 2.8 ng mL(-1), respectively. When SLS is used as the probe the linear range is 2.0 x 10(-8)-1.0 x 10(-5) g mL(-1) and 2.5 x 10(-8)-1.0 x 10(-5) g mL(-1) for BSA and HSA, respectively, and the detection limits are 12.8 and 21.6 ng mL(-1), respectively. The biological mimics samples are synthetic concoctions of BSA and HSA with some interferents. In these samples, the concentration of interferents is higher than the concentration normally existing in organisms. The samples were determined satisfactorily.

Animals↗

PubMed2002

Study on the resonance light scattering spectrum of berberine-cetyltrimethylammonium bromide system and the determination of nucleic acids at nanogram levels.

The interaction of berberine with nucleic acid in the presence of cetyltrimethylammonium bromide (CTMAB) in aqueous solution has been studied by spectrophotometry and resonance light scattering (RLS) spectroscopy. At pH 7.30, the RLS signals of berberine were greatly enhanced by nucleic acid in the region of 300-600 nm characterized by four peaks at 324.0, 386.5, 416.5 and 465.0 nm. The binding properties were examined by using a Scatchard plot based on the measurement of enhanced RLS data at 416.5 nm. Under optimum conditions, the increase of RLS intensity of this system at 416.5 nm is proportional to the concentration of nucleic acid. The linear range is 7.5 x 10(-9)-7.5 x 10(-5) g ml(-1) for calf thymus DNA, 7.5 x 10(-9)-2.5 x 10(-5) g ml(-1) for herring sperm DNA, and 5.0 x 10(-9)-2.5 x 10(-5) g ml(-1) for yeast RNA. The detection limits (S/N = 3) are 2.1 ng ml(-1) for calf thymus DNA, 6.5 ng ml(-1) for herring sperm DNA and 3.5 ng ml(-1) for yeast RNA, respectively. Three synthetic samples were analyzed satisfactorily.

Animals↗

PubMed2002

Study on the molecular recognitions of calix[n]arenes to 2,3-diaminonaphthalene by using fluorometric technique.

The molecular recognition properties of calixarenes to 2,3-diaminonaphthalene (DAN) were investigated. We found that the fluorescence emission of DAN has a blue shift after p-sulfonic sodium calix[4]arece (SSCA) was added to DAN. The proposed mechanism of the molecular recognition between SSCA and DAN indicates that DAN goes into the cavity of SSCA with the help of the hydrogen bonding between the amino group of DAN and sulphonyl group of SSCA. The inclusion ratios and inclusion constants of the host-guest complexes are determined by using the deduced equations.

2-Naphthylamine↗

PubMedDate not supplied

A fluorimetric method for the determination of nucleic acids using Ce(IV) and sodium triphosphate.

A novel and stable fluorimetric method was established for the determination of nucleic acids. The proposed method is based on the reduction by nucleic acids of Ce(IV) to fluorescent Ce(III). The fluorescence intensity can be greatly increased by sodium triphosphate. The enhanced fluorescence intensity is proportional to the concentration of nucleic acids in the range 4.2 x 10(-8)-4.2 x 10(-6) g/mL for fish sperm DNA and 5.0 x 10(-8)-6.5 x 10(-6) g/mL for yeast RNA, and the detection limits (S/N = 3) are 13.5 ng/mL and 45 ng/mL, respectively. The reaction mechanism of the hydrolytic scission of nucleic acids by Ce(IV) is discussed.

Animals↗

PubMedDate not supplied

Fluorescence enhancement effect of the morin-Al3+ -sodium dodecyl benzene sulphonate-protein system and the determination of proteins.

The fluorescence intensity of the morin-Al(3+) complex was greatly enhanced by proteins in the presence of sodium dodecyl benzene sulphonate (SDBS). Based on this, a new fluorimetric method for the determination of protein was developed. Under optimum conditions, the enhanced intensity of fluorescence was in proportion to the concentration of proteins in the range 1.0 x 10(-8)-1.3 x 10(-5) g/mL for bovine serum albumin (BSA), 4.0 x 10(-8)-1.2 x 10(-5) g/mL for egg albumin (EA) and 5.0 x 10(-8)-1.2 x 10(-5) g/mL for human serum albumin (HSA). Their detection limits (S:N = 3) were 5.0 x 10(-9), 1.8 x 10(-8) and 1.6 x 10(-8) g/mL, respectively. The interaction mechanism was also studied.

Aluminum↗

PubMedDate not supplied

Resonance light scattering technique for the determination of proteins with Congo red and Triton X-100.

Resonance light scattering (RLS) of Congo red (CR) was greatly enhanced by BSA (HSA) in the presence of Triton X-100 (TX-100). In sodium citrate-HCl buffer (pH 2.7-3.0), the enhanced intensity of resonance light scattering at 360 nm was in proportion to the concentration of proteins [corrected] The linear relationship was obtained between the resonance light scattering intensity and proteins in the range 5.0 x 10(-8)-8.0 x 10(-6) g/mL and 1.0 x 10(-9)-6.0 x 10(-6) g/mL for BSA and HSA, respectively. Their detection limits were 1.4 x 10(-8) g/mL and 2.8 x 10(-10) g/mL (S:N = 3), respectively. Synthetic and actual samples were analysed satisfactorily.

Buffers↗

PubMedDate not supplied

The sensitive determination of nucleic acids using a fluorescence-quenching method.

Experiments indicated that nucleic acids can quench the fluorescence of the Eu3+ -2-thenoyltrifluoroacetone (TTA)-1,10-phenanthroline (Phen) system. Based on this, a sensitive method for the determination of nucleic acids was proposed. The experiments indicated that under the optimum conditions, the quenched fluorescence intensity was in proportion to the concentration of nucleic acids in the range 1.0 x 10(-11)-1.0 x 10(-6) g/mL for yeast RNA (yRNA), 5.0 x 10(-11)-5.0 x 10(-7) g/mL for fish sperm (fsDNA) and 1.0 x 10(-10)-1.5 x 10(-6) g/mL for calf thymus DNA (ctDNA). Their detection limits were 3.0 x 10(-12), 4.0 x 10(-12) and 5.0 x 10(-11) g/mL, respectively. Therefore, the proposed method is one of the most sensitive methods available. The interaction between nucleic acids and Eu3+ -TTA-Phen is also discussed.

Europium↗