Direct chemiluminescent imaging detection of serum proteins in polyacrylamide gels

Development of sensitive metalloporphyrin probes for chemiluminescent imaging detection of serum proteins

The development of metalloporphyrin- (ferric protoporphyrin IX chloride (FePP), cobalt (III) protoporphyrin IX chloride, copper (II) protoporphyrin IX) enhanced chemiluminescent (CL) imaging detection of serum proteins after PAGE is described in this article. The detection is based on the catalytic activity of metalloporphyrins, especially FePP, in the CL reaction of the luminol-H2O2 system. Some relatively low abundant proteins such as hemopexin (Hpx) and complement C4 are sensitively detected by FePP-enhanced CL imaging. Other proteins such as haptoglobin, apolipoprotein A-1, complement C3, and alpha-1-antitrypsin are also detected and identified by MS and MS/MS techniques. Detection limit of Hpx is as low as 20 ng, without the need of expensive antibodies or tedious immunoassay procedures. The mechanism of the proposed method is discussed employing standard proteins. The application to the analysis of different protein patterns in healthy people and in Thalassemia patients is being investigated.

Improving sensitivity in micro-free flow electrophoresis using signal averaging

Microfluidic free-flow electrophoresis (microFFE) is a separation technique that separates continuous streams of analytes as they travel through an electric field in a planar flow channel. The continuous nature of the microFFE separation suggests that approaches more commonly applied in spectroscopy and imaging may be effective in improving sensitivity. The current paper describes the S/N improvements that can be achieved by simply averaging multiple images of a microFFE separation; 20-24-fold improvements in S/N were observed by averaging the signal from 500 images recorded for over 2 min. Up to an 80-fold improvement in S/N was observed by averaging 6500 images. Detection limits as low as 14 pM were achieved for fluorescein, which is impressive considering the non-ideal optical set-up used in these experiments. The limitation to this signal averaging approach was the stability of the microFFE separation. At separation times longer than 20 min bubbles began to form at the electrodes, which disrupted the flow profile through the device, giving rise to erratic peak positions.

Direct chemiluminescent imaging detection of human serum proteins in two-dimensional polyacrylamide gel electrophoresis

A novel chemiluminescence (CL)-based imaging method capable of directly detecting proteins in polyacrylamide gels after electrophoresis is proposed. Human serum proteins are presently detected by a direct CL imaging method after native 2-D PAGE. As a consequence, some proteins, including haptoglobin (Hp), Hp precursor, hemopexin (Hpx) precursor, Ig alpha-1 chain C region, and Complement C3 precursor can be detected and identified by MS and MS/MS techniques. These proteins are all acute phase proteins, which have been defined as biomarkers for certain diseases. Moreover, serum proteins from healthy people and cirrhotic patients were analyzed. A decrease in Hp spots for cirrhotic patients could be confirmed. The CL imaging conditions were optimized, including the concentrations of H(2)O(2) and luminol. The process of CL detection of proteins is simple, and there is no need for specialized equipment. In comparison with the traditional CBB-R250 staining method, the detection sensitivity was improved and the detection period decreased about 70 times. Hence, this technique possesses potentials as a rapid, convenient, and inexpensive analytical technique for protein detection and for the diagnosis of diseases.

A novel [Ag(NH3)2]+ probe for chemiluminescent imaging detection of proteins after polyacrylamide gel electrophoresis

The development of a novel [Ag(NH3)2]+ probe chemiluminescence (CL)-based imaging method for the detection of various proteins after PAGE is described. The detection is based upon the probe [Ag(NH3)2]+ catalyzing the CL reaction of the luminol-potassium persulfate system. The proposed method detects various proteins labeled by [Ag(NH3)2]+ and expands the application scope to SDS gels. It also detects proteins directly in polyacrylamide gels, without tedious transferring procedures. Furthermore, successful identification of proteins by peptide mass profiling using ionization MS was easily performed, and no pretreatments of gel prior to digestion are needed. Detection limits for standard marker proteins match CBB-R250 staining and the linear dynamic range is superior to CBB-R250 staining and silver staining. The CL imaging conditions, including luminescent reagents, silver ion concentration, the ammonia-controlled system and the washing reagents parameters have also been optimized.

Coupling chemiluminescence with capillary electrophoresis to analyze single human red blood cells

In this paper, we describe a new method for determination of hemoglobin of single red blood cells by coupling chemiluminescence with capillary electrophoresis (CL-CE). The chemiluminescent detection is based on the catalytic effects of hemoglobin on the luminol-hydrogen peroxide reaction. The conditions of chemiluminescent reaction and capillary electrophoresis were investigated. Hemoglobin in human blood samples was detected with the present method, the linear range from 1.7 microg mL(-1) to 6.8 microg mL(-1) was tested, and the correlation coefficient of 0.997 and low detection limit of 0.17 microg mL(-1) (approximately 2.2 pg, S/N=3) were obtained. Cell injection procedure was improved, and the method was successfully used to determine hemoglobin of single red blood cells and the statistical result of the average content of hemoglobin in 26 human red blood cells was 23.6 pg. Compared to other current methods, CE with CL system is simple, sensitive and will become an attractive alternative method for single cell analysis.

Direct chemiluminescent imaging detection of Cu/Zn-superoxidase dismutase, glutathione peroxidase, carbonic anhydrase-III, and catalase in rat liver cytosol separated by native porous gradient polyacrylamide gel electrophoresis

The cytosolic enzymes extracted from rat hepatocytes were separated by native porous gradient-PAGE (PG-PAGE) and were detected with a sensitive and fast chemiluminescence (CL) imaging method. Several peroxidases including glutathione peroxidase, Cu/Zn-superoxidase dismutase, and some other metallo-enzymes such as catalase, carbonic anhydrase-III (CA-III) present in the cytosol of rat hepatocytes have been selectively and sensitively detected by the direct CL imaging method using the luminol-H(2)O(2) chemiluminescent reagents. All detections after PG-PAGE were completed within 9 min. The linear range for the typical metallo-enzyme, e.g., CA-III is 0.75-4.9 microg/mL, with a detection limit of 0.25 microg/mL. In comparison with the traditional CBB-R250 staining method, the detection period decreased about 70 times and the detection sensitivity improved over ten times. Furthermore, two enzymes present in rat liver cytosol were identified employing MALDI-MS analysis of the tryptic digest after PG-PAGE.