Peptides: an analytical method for their resolution by polyacrylamide gel electrophoresis applicable to a wide range of sizes and solubilities

A new multiphasic buffer system for sodium dodecyl sulfate-polyacrylamide gel electrophoresis of proteins and peptides with molecular masses 100,000-1000, and their detection with picomolar sensitivity

A novel multiphasic buffer system for high resolution sodium dodecyl sulfate-polyacrylamide gel electrophoresis of dansylated and nondansylated proteins/peptides in the relative molecular mass (Mr) range of 100,000-1000 is described. The system, based on Jovin's theory of multiphasic zone electrophoresis, allows complete stacking and destacking of proteins/peptides within the above Mr range. The buffer system uses Bicine and sulfate as trailing and leading ion, respectively, and Bistris and Tris as counter ions in the stacking and separating phase, respectively. Through selection of two different counter ions--the characteristic feature of the present ionic system--the stacking limits of a multiphasic buffer system can be further widened, thus making it applicable to gel electrophoresis of a larger spectrum of rapidly migrating species, such as sodium dodecyl sulfate-proteins/peptides and nucleic acids, than has been possible previously. Highly sensitive detection methods for proteins as well as for polypeptides down to approximately Mr 1000 are described. Dansylated proteins/peptides were detected by their fluorescence either directly within the gel or following electroblotting into anion-exchange or polyvinylidene difluoride membranes. The latter procedure resulted in detection sensitivities of approximately 1 ng. Nondansylated proteins/peptides were either detected within the gel by colloidal Coomassie staining or by electroblotting into polyvinylidene difluoride membranes, followed by colloidal gold staining. Prior to both staining procedures the proteins/peptides were pretreated with glutardialdehyde in the presence of borate at near neutral pH values to generate protein/peptide polymers of poor solubility. For a given pH the efficiency of the latter procedure was significantly influenced by the nature of the buffer ion used in the fixation buffer. In contrast to conventional fixation procedures even small polypeptides (Mr 1000) were immobilized and approximately 15 ng and 0.75 ng could be detected after colloidal Coomassie and colloidal gold staining, respectively.

Application of sodium dodecyl sulfate-gel electrophoresis to low molecular weight polypeptides

Experiments with nine polypeptides with molecular weights between 2000 and 10,760 confirm the value of sodium dodecy sulfate (SDS)-gel electrophoresis for separating polypeptides in this molecular weight range. In one case, electrophoretic blotting and microsequencing were successfully carried out. However, molecular weight determination in the low molecular weight range (less than 10,000) is much less reliable than that in the conventional molecular weight range (greater than 10,000) for SDS gels. Information provided by suppliers of horse heart myoglobin fragment kits is potentially misleading.

Peptide and protein molecular weight determination by electrophoresis using a high-molarity tris buffer system without urea

Various buffer systems were examined for their ability to resolve and provide molecular weight determinations of proteins and peptides over a wide size range using electrophoresis in sodium dodecyl sulfate-polyacrylamide gels. Sharp bands and high resolution were achieved in the 1300 to 100,000 molecular weight range using a modified Laemmli discontinuous buffer system with high concentrations of Tris in the resolving gel (0.75 M) and in the running buffer (0.05 M). Linear gradient gels (8 to 25% acrylamide) were tested with and without varying concentrations of urea and/or glycerol and/or sucrose. At this high molarity of Tris, the inclusion of urea, glycerol, or sucrose proved unnecessary for successful peptide electrophoresis. Gels run without these reagents showed superior resolution throughout the entire molecular weight range when run with Tris at 0.75 and 0.05 M, respectively, obviating the need for urea or other additives as used in other systems. A single gel is thus able to resolve an entire range from large proteins to small peptides.

Detection and quantitation of fluorescamine-labeled bradykinin, its analogues and metabolites using high-performance liquid chromatography

A sensitive technique is described for detecting and quantitating fluorescamine-labeled kinins and their usual metabolic products using reversed-phase high-performance liquid chromatography (HPLC) linked with a fluorescence detector. Kinins and their enzymatic products were labeled with fluorescamine, subjected to HPLC, and scanned for the fluorescence signal with excitation at 390 nm and emission at 476 nm. The fluorescence signal was linear with bradykinin, Lys-bradykinin and Met-Lys-bradykinin in amounts upward from 2.5 ng. Separation of the fluorescamine-labeled kinins using HPLC was carried out with a solvent system of methanol-triethylammonium formate buffer. Labeled kinins were eluted in the following order: bradykinin, Lys-bradykinin, and Met-Lys-bradykinin. When native (unlabeled) kinins were subjected to HPLC using a solvent system of acetonitrile-triethylammonium formate buffer, the minimum amount of native kinin detected at 210 nm was 1 microgram. All three kinins showed linearity at 210 nm in amounts upward from 1 microgram. Kinins were eluted in the following order: Lys-bradykinin, bradykinin and Met-Lys-bradykinin. The different elution patterns of kinins by means of these two separation techniques provide a useful method for identification of purified kinins. The fluorescamine label provides a 400-fold more sensitive detection technique than ultraviolet absorbance of the native kinins and may be used to identify the metabolic products of kinins.

Native molecular weight of adenovirus proteins: on the oligomeric structure of the fiber

Fluorescamine-modification of amino groups was used to eliminate the influence of basic charge on the final migration position of protein's in alkaline pH polyacrylamide gradient gel electrophoresis. As applied to adenovirus structural components, this type of analysis suggested the fiber to be composed of three identical subunits. The trimeric nature of both penton base and fiber therefore displaces the problem of symmetry mismatching to penton base and surrounding hexons at each vertex of the adenovirus icosahedron.

Pancreatic spasmolytic polypeptide (PSP): I. Preparation and initial chemical characterization of a new polypeptide from porcine pancreas

A novel polypeptide, named Pancreatic Spasmolytic Polypeptide (PSP), was discovered in a side-fraction from the purification of porcine insulin. PSP was prepared by two different purification methods based on combinations of precipitations, anion-exchange and cation-exchange chromatography. The highest yield obtained, 52 mg PSP/kg pancreas, indicates that the content of PSP in porcine pancreas is about half the content of insulin. Both preparations appeared to be very pure as judged by basic disc electrophoresis, isoelectric focusing, analytical gel filtration and radioimmunoassays for various polypeptides known to be present in pancreas. The PSP molecule contains 106 amino acids (MW about 11 700). PSP is an acidic (pI 4.4), non-glycosylated protein without free N-terminal amino groups, and with high contents of proline and cystine. The high content of S-S bridges (7 per molecule), an unexpected low apparent MW determined by gel filtration, and a remarkable resistance towards treatment with trypsin and chymotrypsin, point to a compact structure of the PSP molecule.

Analysis of peptides from pigeon cerebrum: a comparison of sacrifice methods

Peptides were extracted and fractionated from pigeon cerebrum and analyzed by thin-layer chromatography, polyacrylamide disc gel electrophoresis, and amino acid analysis. A highly consistent pattern of peptides in the 700-5000 molecular weight range was obtained from each cerebral sample. A comparison was also made between cerebral peptide patterns obtained from animals sacrificed by decapitation with those from animals sacrificed by microwave irradiation. Amino acid analysis of the peptide fraction from microwaved and decapitated animals revealed slight differences in the amount and incidence of various amino acids. These differences may be due to post-mortem proteolysis in the cerebra of decapitated pigeons prior to homogenization and freezing.

The delta EEG (sleep)-inducing peptide (DSIP). XI. Amino-acid analysis, sequence, synthesis and activity of the nonapeptide

A peptide which induces slow-wave EEG (sleep) after intraventricular infusion into the brain has been isolated from the extracorporeal dialysate of cerebral venous blood in rabbits submitted to hypnogenic electrical stimulation of the intralaminar thalamic area. It was shown by amino-acid analysis and sequence determination to be Trp-Ala-Gly-Gly-Asp-Ala-Ser-Gly-Glu and named "Delta Sleep-Inducing Peptide" (DSIP). This compound was synthesized as well as 5 possible metabolic products (1--8, 2--9, 2--8, 1--4 and 5--9), 2 nonapeptide analogues (with one and two amino-acids exchanged) and a related tripeptide (Trp-Ser-Glu). All 9 synthetic peptides were infused intraventricularly in rabbits (6 nmol/kg in 0.05 ml of CSF-like solution over 3.5 min) and tested under double-blind conditions. A total of 61 rabbits including controls were used. The EEG from the frontal neocortex and the limbic archicortex were subjected to direct fast-Fourier transformation and analyzed by an 1108 computer system. A highly specific delta and spindle EEG-enhancing effect of the synthetic DSIP could be demonstrated. The mean increase of EEG delta activity reached 35% in the neocortex and limbic cortex as compared to control animals receiving CSF-like solution or any of the other 8 peptides. The final chemical characterization of the synthetic DSIP revealed that only the pure alpha-aspartyl peptide is highly active in contrast to its beta-Asp isomer. A neurohumoral modulating and programming activity was suggested.

The differentiation of fluorescamine-modified kinins by gel electrophoresis

To decrease the risk of iatrogenic thromboembolic complications during interventional procedures with coaxial catheter systems, aspirin and systemic heparinization were used in 57 consecutive cases. No thromboembolic complications occurred. This group was compared with a second group of 25 patients who also had interventional procedures with coaxial systems but who had only a continuous heparinized drip infusion flushing the inside of the coaxial system. Two patients had an embolic complication and two others had thrombus formation inside or outside the catheters without neurologic symptoms. The use of systemic heparinization has been extended to all prolonged angiographic procedures except in cases of acute or recent subarachnoid hemorrhage.

Fibrinopeptide A in plasma of normal subjects and patients with disseminated intravascular coagulation and systemic lupus erythematosus

A radioimmunoassay for fibrinopeptide A (FPA) has been developed. This assay uses rabbit antibodies induced by injection of native FPA-human serum albumin conjugates and 125I introduced into tyrosine-FPA synthesized in out laboratory. Plasma FPA is separated from fibrinogen by TCA extraction. The assay is capable of detecting as little as 50 pg/ml of FPA. In 20 normal donors this assay revealed a mean concentration of 0.9 ng/ml (0.3 SD). In five patients with disseminated intravascular coagulation, FPA concentrations ranged from 13.0 to 346 ng/ml. Two groups of patients with systemic lupus erythematosus (SLE) whose disease had achieved complete remission were studied; one consisted of four patients with no history of lupus nephritis and another with a history of nephritis. Mean FPA concentrations of 1.5 ng/ml (range, 0.7-1.8 ng/ml) and 2.7 ng/ml (range, 1.1-5.6 ng/ml) were found in these two groups, respectively. Another group of nine patients with active SLE, but without evidence of lupus nephritis, had a mean FPA concentration of 4.5 ng/ml (range, 2.4-7.8 ng/ml). Finally, a group of seven patients with active SLE, including active nephritis, had a mean FPA concentration of 10.2 ng/ml (range, 5.3-17.0 ng/ml). A positive correlation was found between the concentration of plasma FPA and serum DNA-binding activity and an inverse correlation was found between plasma FPA and the concentration of serum C3. No correlation existed between plasma FPA and concentration of serum creatinine. Several possibilities for the origin of plasma FPA in patients with SLE were considered; at present it seems most likely that FPA arises through the action of thrombin on fibrinogen.