Dodecyl sulphate/polyacrylamide-gel electrophoresis at low pH values and low temperatures.

A simple method is described for dodecyl sulphate/polyacrylamide-gel electrophoresis of pH- and temperature-labile biological intermediates. The method is based on a catalyst system that works at temperatures of 2--4 degrees C and pH values of 2--4 and an appropriate buffer system containing Li+ or Tris [CH2OH--C(CH2OH)2--NH3+] instead of Na+. This system does not lead to the precipitation of 1% dodecyl sulphate.     

Anomalous migration of leghaemoglobin on sodium dodecyl sulphate/polyacrylamide-gel electrophoresis.

The estimate of the molecular weight of leghaemoglobin by sodium dodecyl sulphate/polyacrylamide-gel electrophoresis is about 20% too low. This is due to an anomalously high limiting relative mobility. Leghaemoglobin binds 1.4 g of sodium dodecyl sulphate/g of protein with a concomitant decrease in the helical content from 71-72% to 49-51%.     

Isoelectric focusing electrophoresis of lignin.

Isoelectric focusing is introduced as a technique for the analysis of macromolecular lignin. The analysis is performed in a pH gradient from 3.5 to 10. Separated lignin fragments are visualized under uv light or by silver staining. The method can be used to distinguish between differently processed lignin preparations and to identify their components. Even the slight modification resulting from attack by ligninolytic enzymes could be detected.     

A convenient apparatus and tracking dye for anaerobic analytical polyacrylamide-gel electrophoresis

An anaerobic modification of conventional polyscrylamide-gel electrophoretic equipment is described. The modified apparatus has been applied to the separation of Azotobacter vinelandii nitrogenase components and should prove useful in the analysis of other O₂-sensitive proteins. Electrophoresis in reducing gels can be followed with a dithionite-resistant tracking dye, potassium gualazulene-1-sulfonate.     

Highly purified agarose as stacking gel in sodium dodecyl sulphate/polyacrylamide-gel electrophoresis.

A modified sodium dodecyl sulphage/polyacrylamide-gel-electrophoretic method is described that utilizes highly purified agarose as stacking gel. The same electrophoretic resolution of different marker proteins is found as when polyacrylamide is used as stacking gel, but the background staining seen when polyacrylamide is used as stacking gel is decreased.     

Fractionation of heparin-derived oligosaccharides by gradient polyacrylamide-gel electrophoresis.

Heparin-derived oligosaccharides, prepared by using flavobacterial heparinase, having a high degree of heterogeneity (sequence variability) were resolved into sharp well-defined bands by using polyacrylamide gel electrophoresis (PAGE). The use of a stacking gel and a high-density-pore-gradient resolving gel was primarily responsible for the success of this separation. Low-Mr standards of known structure and having a degree of polymerization (dp) 2-6 were used to establish that the separation on gradient PAGE was primarily dependent on molecular size. High-Mr oligosaccharides (dp 8-20) were prepared using strong-anion-exchange h.p.l.c. and were used to help characterize the gradient PAGE separation. Kinetic profiles were obtained for the depolymerization of heparin and heparan sulphate with heparinase and heparitinase respectively. The utility of this approach in sequencing oligosaccharides derived from glycosaminoglycans is discussed.     

Isoelectric focusing by free solution capillary electrophoresis.

A reproducible, quantitative isoelectric focusing method using capillary electrophoresis that exhibits high resolution and linearity over a wide pH gradient was developed. RNase T1 and RNase ba are two proteins that have isoelectric points (pI's) at the two extremes of a pH 3-10 gradient. Site-directed mutants of the former were separated from the wild-type form and pI's determined in the same experiment. The pI's of RNase T1 wild-type, its three mutants, and RNase ba were determined for the first time as 2.9, 3.1, 3.1, 3.3, and 9.0, respectively. The paper describes the protocol for isoelectric focusing by capillary electrophoresis, as well as presenting data describing the linearity, resolution, limits of mass loading, and reproducibility of the method.     

Membrane-associated nuclease activities in mycoplasmas.

Membrane-associated nucleases of various mycoplasmal species were investigated by using two nuclease assays. A lambda DNA assay was developed to measure nuclease activity associated with whole-cell suspensions, activity released from intact cells, and activity associated with detergent-disrupted cells. In most species, nuclease activities were entirely membrane associated, and disruption by a detergent had a stimulatory effect on these activities. All mycoplasmal species contained nuclease activity, but Mycoplasma capricolum was unusual because its activity was dependent upon magnesium and was inhibited by calcium. We developed a sodium dodecyl sulfate-polyacrylamide gel electrophoresis system that produced reproducible nuclease patterns, and this system was used to determine the apparent molecular weights of the nuclease proteins. An examination of 20 mycoplasmal species failed to identify common bands in their nuclease patterns. An examination of 11 Mycoplasma pulmonis strains, however, indicated that nuclease patterns on polyacrylamide gels may provide a means for categorizing strains within a species. Our results suggest that nucleases are important constituents of mycoplasmal membranes and may be involved in the acquisition of host nucleic acids required for growth.     

Isoelectric focusing and electrophoresis at subzero temperatures

Electrophoretic and isoelectric focusing separations have been achieved at ?20 to ?30°C, i.e., at temperatures considerably lower than previously reported by using as supporting media gels of acrylamide-methylacrylate copolymers and dimenthylsulfoxide-water mixtures. Hybrids of human and sickle cell hemoglobin and partially oxidized human carboxyhemoglobin have been separated in the temperature range ?20 to ?30°C, both by a discontinuous buffer gel electrophoresis and by isoelectric focusing.     

An apparatus for the simultaneous performance of polyacrylamide-gel electrophoresis at multiple pHs.

Optimization of the operative pH of polyacrylamide-gel electrophoresis can be carried out on a single workday by a single operator using a multichamber PAGE apparatus. The apparatus was shown to be capable of simulataneous gel electrophoresls at up to 10 different pH values.     

The use of lectins to characterize and separate living canine spermatozoa: A preliminary study

This study was designed as a preliminary attempt to develop a methodology for relating the glucidic structure of the sperm membrane to sperm morphology. Differences in plasma membrane glycoconjugates between motile and nonmotile spermatozoa were studied by using 7 lectins. Fresh spermatozoa from 3 dogs were analyzed by fluorescein isothiocyanate (FITC) labeled lectins. The binding of lectins to the sperm membrane and the capability of the lectins to agglutinate spermatozoa were estimated semi-quantitatively by observation with either an epifluorescence or a phase contrast microscope, respectively. All the lectins tested bound to non motile spermatozoa, with Helix pomatia , Pisum sativum and Arachis hypogaea showing intense fluorescence, Triticum vulgare and Glycine maxima showing moderate fluorescence, and Phaseolus vulgaris and Phytolacca americana showing low fluorescence. However, Helix pomatia . and Triticum vulgare also bound to rapid and slow moving spermatozoa, and were the only 2 lectins that induced sperm agglutination. These results suggest that lectins could be a possible tool for characterizing and separating spermatozoa with different rates of motility.     

Two-dimensional polyacrylamide-gel electrophoresis of the proteins and glycoproteins of the human erythrocyte membrane.

A two-dimensional polyacrylamide gel electrophoresis technique has been developed, improving the analytical separation of some proteins and glycoproteins of the human erythrocyte membrane. Freshly prepared membranes are totally solubilized, subjected to dodecylsulfate--polyacrylamide gel electrophoresis in the first dimension, followed by electrophoresis in the second dimension, using a detergent-free polyacrylamide gradient gel. By this method the proteins of the human erythrocyte membrane could be resolved into a two-dimensional pattern, which has been shown to be highly reproducible with respect to various blood-groups and within one blood-group from specimen to specimen. The method enables especially the investigation of the hydrophobic and very likely integrated membrane proteins and glycoproteins. Thus, band III[Fairbanks, G., Steck, Th. & Wallach, D. F. H., Biochemistry, 10, 2606--2617 (1971)] could be shown to consist of five proteins, one of them being the major glycoprotein of the human erythrocyte membrand. The two spectrin bands differed considerably in their two-dimensional patterns. The value of the given method for the investigation of membrane defects, which may be linked with various diseases of human erythrocytes, could be demonstrated in the case of two patients suffering from congenital dyserythropoetic anaemia.     

Analysis of the heterogeneity of human collagens by two-dimensional polyacrylamide-gel electrophoresis.

The heterogeneity of the CNBr-cleavage peptides of human types I, II, III and V collagens were studied by using two-dimensional electrophoresis combining non-equilibrium pH-gradient-gel electrophoresis and sodium dodecyl sulphate/polyacrylamide-gel electrophoresis. Specific 'maps' were produced by the peptides obtained from the chains of each type of collagen, and most peptides had at least three charged forms of the same molecular weight. Specific 'maps' were also produced by the peptides of types I, III and V collagens from insoluble dermis and the peptides of types I and V collagens from decalcified bone. The alpha 1(I) CB7 and alpha 1(I) CB8 and the alpha 2 CB4 peptides obtained from the type I collagens of these tissues contained the same number of charged components, but there was a relative increase in the more basic components in bone. Some aspects of the involvement of the alpha 1(I) CB6 and the alpha 1(III) CB9 peptides in cross-linkages were also studied. The recovery of the alpha 1(I) CB6 peptide from bone and dermis was decreased and the alpha 1(III) CB9 peptide was not detected in dermis. Additional peptides, which were probably cross-linked peptides involving the alpha 1(I) CB6 peptide, were also observed.     

Effect of corticotropin treatment in vivo on the synthesis of a specific adrenal cytosolic protein. Characterization by dual-labelling technique and polyacrylamide-gel electrophoresis.

The effect of corticotropin in vivo on total and specific protein synthesis in the adrenal was studied. Adrenal slices from control and corticotropin-treated animals were incubated with [14C]- and [3H]-leucine respectively, followed by sodium dodecyl sulphate/polyacrylamide-gel electrophoresis of subcellular components. With this sensitive dual-labelling technique the following results were obtained. There was a general trophic effect on most adrenal proteins, but corticotropin produced a marked stimulation of a specific adrenal cytosolic protein. This protein has mol.wt. approx. 30 000 and pI 5.5. Corticotropin increased the incorporation of labelled leucine into proteins within 4 h, but no effect was observed before 2 h and after 16 h there was no further increase. These data suggest that this protein is not involved in the corticosteroidogenic action of corticotropin, but rather in the trophic action of this hormone.     

A pattern recognition technique to characterize the differential modulation of co-activating muscles at the performer/environment interface.

The purpose of this research was to develop and test an analytical tool that would recognize and classify the surface electromyographic (EMG) signal of co-activating muscles of the leg into pre-defined patterns of muscle activity: burst, tonic, and tonic-burst. Developed to study the task of landing from a jump in children, the pattern recognition technique (PRT) quantifies the full-wave rectified surface EMG signal over a short-duration sampling window by a single linear regression value. Shifting the sampling window across the data string ultimately defines the signal by a set of regression values that produce the recognizable burst, tonic and tonic-burst patterns on a least-squares surface plot. Statistical comparison of the PRT to the classical combination of threshold detection (+2 S.D. of mean baseline activity) and visual inspection proves the PRT to be more reliable on repeated measures for event detection and classification, with a Kappa statistic of 0.83 compared to 0.54 for threshold detection. Application of the PRT to motor control studies is presented for the regulation of the mechanical response of the leg during impact. Responsiveness of the PRT is tested, issues of accuracy and validity are addressed, and limitations in spatial-temporal resolution are identified.     

Isoelectric focusing and 2D electrophoresis of the human androgen receptor.

Nuclear androgen receptors from cultured genital skin fibroblasts were analyzed by non-denaturing isoelectric focusing (IEF) in ultrathin polyacrylamide gels before and after photoaffinity labeling with [3H]methyltrienolone. Both reversibly and covalently labeled receptors focused at pH 5.28 +/- 0.20 when extracted from nuclei with high salt. Lowering of the salt concentration yielded, in both cases, a second species which focused at pH 7.16. This species became predominant when nuclei were sonicated in IEF sample buffer containing no salt, even after extensive nucleic acid digestion. Low salt cytosols from both prostate and foreskin focused as a single peak of pI: 4.93 +/- 0.31 which remained unchanged when KCl was added to the cytosol up to a concentration of 0.6 M. SDS-polyacrylamide gel electrophoresis of photoaffinity labeled receptors revealed labeled proteins with Mw 90-95 kDa. Two-dimensional electrophoresis of photoaffinity labeled nuclear receptors, extracted in low or high salt, showed that the two isoforms (pI 5.28 and 7.16) contain the same steroid-binding subunit with Mw 90-95 kDa. Nuclear receptors from 4 patients with the receptor positive form of the Complete Androgen Insensitivity Syndrome (CAIS, Rc+) were analyzed by non-denaturing IEF: a single species was observed, focusing at pH 6.0 whether in high or low salt conditions. These results indicate that the nuclear androgen receptor is an acidic protein with pI 5.28 and Mw 90-95 kDa under maximum protein dissociation conditions. When extracted under low salt conditions, it can be isolated in a neutral form (pI 7.16) suggesting its association with a nuclear protein. Receptors of (CAIS, Rc+) patients have an abnormal charge and show no pI shift upon lowering of the salt concentration suggesting that this shift could be a significant step in the mechanism of action of androgens.     

A new and more accurate technique to characterize airway nitric oxide using different breath-hold times.

Exhaled nitric oxide (NO) arises from both airway and alveolar regions of the lungs, which provides an opportunity to characterize region-specific inflammation. Current methodologies rely on vital capacity breathing maneuvers and controlled exhalation flow rates, which can be difficult to perform, especially for young children and individuals with compromised lung function. In addition, recent theoretical and experimental studies demonstrate that gas-phase axial diffusion of NO has a significant impact on the exhaled NO signal. We have developed a new technique to characterize airway NO, which requires a series of progressively increasing breath-hold times followed by exhalation of only the airway compartment. Using our new technique, we determined values (means +/- SE) in healthy adults (20-38 yr, n = 8) for the airway diffusing capacity [4.5 +/- 1.6 pl.s(-1).parts per billion (ppb)(-1)], the airway wall concentration (1,340 +/- 213 ppb), and the maximum airway wall flux (4,350 +/- 811 pl/s). The new technique is simple to perform, and application of this data to simpler models with cylindrical airways and no axial diffusion yields parameters consistent with previous methods. Inclusion of axial diffusion as well as an anatomically correct trumpet-shaped airway geometry results in significant loss of NO from the airways to the alveolar region, profoundly impacting airway NO characterization. In particular, the airway wall concentration is more than an order of magnitude larger than previous estimates in healthy adults and may approach concentrations (approximately 5 nM) that can influence physiological processes such as smooth muscle tone in disease states such as asthma.